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PHYSIOLOGY OF THE

INVERTEBRATA

THE

PHYSIOLOGY

THE INVERTEBRATA

• • • * • • 'kV '•* ».. »»^ -

A. B. GRIFFITHS, Ph.D., F.R.S.(Edin.), F.C.S,

MEMBRE DE LA SOClixi CHIMIQUE OB PARIS ; MEMBER OP THE
PHYSICO-CHEMICAL SOCIETY OF ST. PETERSBURG

AUTHOR OP

" RESEARCHIiS O.V Af/CRO-ORG^.V/SAfS," '* T///I DISH ASKS OF CROPS,"

ETC. ETC.

LONDON

L. REEVE AND CO.

5 HENRIETTA STREET, COVENT GARDEN. W.C

1892
\^A II rights reserved]

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G-85-
I 892.

Prof. T. H. HUXLEY, LL.D., F.R.S., F.L.S., F.Z.S.

Correspondant de rinstitut de France
Past' President of the Royal Society^ etc. etc.

WHO HAS CREATED A NEW EPOCH IN BIOLOGY ; AND WHOSE

GENIUS ^AS DONE SO MUCH TO AWAKEN THE KEENEST

INTEREST IN THE STUDY AND POPULARISATION

OF SCIENCE

^bid TRnotk fa (b« pemttoeion) Dedicated

A TOKEN OF ADMIRATION AND RESPECT

THE AUTHOR

.^503

PEEFACE.

»♦!

** PhysMogy it to a great extent applied phyaica and chemistry:*

Prop. Huxlbt.

**A trtte knowledge of biology must be bated on a kmwkdge qf chendatry
andphyHes:' — M. M. P. Munu

** Biology being the tdence which deals with the matter and energy qf living
things, manifestly rests on physics and chemistry, since it invobres the appli'
caikm of the laws and principles qf these sciences to the special case qf living
matter,*'''^ J. H. G1B8ON.

" Chemistry lies at the basis qf physiology:' -^Jl Binet.

** It is in^ifossible that physiology can ever acquire a scient(/lc foundation
without the aid 0/ chemistry ami physics.^ — J. ton Liebio.

The branch of biology detailed in the following pages has
had only a few workers^ for the reason that the majority of
biobgists are not chemists, and consequently have not the
necessary manipolatiye skill in applying a science like
chemistry to the solution of biological problems.

The true functions of the various organs of the Irwertebraia
have always been, until recent years, more or less prob-
lematical. Morphology and histology alone could not answer
correctly the questions involved ; but physiology with chemical
and physical methods of research have illuminated very
many obscure problems concerning the functions of the
various organs and tissues of the InvcrtebrcUa ; and no doubt

they are destined to play an important part in the elncidatioa I
of many problems still requiring solution.

The following work gives an account of some of the most
important researches on the subject, which have been published
during the past fifteen or twenty years; and I have also
included an account of my own researches in the present
volume, more especially as these have appeared in the
FroccedtTigs of the Koyal Societies of London and Edinbui-gh,
and have also attracted the attention of the Acad^mie des ,(
Sciences (I'Institut de France), to the extent that its Council j
thought proper to award me an " honourable mention "
connection with the Prir. Mfmtyon, which is given annaally '
for researches in experimental physiology and physiological
chemistry. Besides, several well-known biologists have !
informed me that a work on the physiology of the Inverte- |
hraiti- would be a welcome addition to biological literatura
Consequently, I hope that this work (although I am fully
cognisant of its many imperfections and shortcomings) may
prove of some utility to those scientists and students who are
desirous of investigating biological problems involving the "i
applications of chemistry and physics. 1

I take this opportunity of expressing my gratitude and i
beat thanks to Sir Richard Owen, K.C.B.. F.R.H., for the '
great interest he has always taken in my investigations, and
for the many letters of friendly criticism which I have received
from him,

I am also grateful to Mr. F- E. Beddard, F.R.S.E. ; the
Rev. W. H. Dallinger, LUD., F.R.S. ; Mr. H. H. Dixon (of
the University of Dublin) ; Prof. J. C. Ewart (of the Univer-
sity of Edinburgh) ; Prof. Leon Fredericq (of the University
of Liege) ; Dr. A. Giard (of Paris) ; Mr. S. T. Griffiths ;

PREFACE. ix

Mr. A. Johnstone, P.G.S. (of the University of Edinburgh) ;

Dr. C. A. MacMnnn, F.C.S. ; Prof. P. Mantegazza (of the

University of Rome) ; Dr. A. C. Maybnry, F.G.S. ; Prof.

A. von Mojsisovics (of the University of Gratz) ; Mr. E. B.

Ponlton, P.R.S. ; Dr. G. J. Romanes, F.R.S. ; Prof. G. 0.

Sars (of the University of Christiania) ; and Dr. C. Zeiss, for

valuable assistance in various parts of the book.

My obligations are due to the President and Council of

the Royal Society of Edinburgh for the loan of certain
wood-blocks used in illustrating my own papers on the
InvertebrcUa, and which were originally printed in the
Society's Proceedings.

In conclusion, I here record the name of my sister (Miss
Mildred H. GriflSths), for her help in preparing, under my
direction, certain drawings for the illustrations. Figures 32
and 33 are supplied by Dr. Carl Zeiss, optician, Jena, from
his catalogue of microscopes.

A. B. GRIFFITHS.

Edobastof, Feb, 1892.

CONTENTS.

CHAPTER I.

PAGB

Introdnction : Definition of Physiology— The Actions of Li?ing

Ifatter— Cells and their Functions — The Function of the Sarcode

•

of the lowest Animals — ^Daal and Triple Functions of an Organ
— Law of Von Baer — Classification of the Invtrtebrata — Division
of Physiological Laboar, &c. . . . . i

CHAPTER II.

The Chemistry of Protoplasm: ''The Physical Basis of Life''—
Analyses of Albumin — Chemical and Physical Properties of
Albumin — Lieberkilhn's Formula for Albumin — Schorlemmer
on the Synthesis of Albumin — Loew and Bokomy's Researches —
Researches of Reinke, Mori, Kretzschmar, Griffiths, Schutzen-
berger, Palladin, Schulze, and Kisser, on Albumin — Decomposition
Products of Albumin or Protoplasm — Latham's Formula for
Albumin — Spencer's Definition of Life, &c. . .10

CHAPTER III.

Digestion in the Invertebraia : Digestion in obnbral — Modes of
Nutrition — Digestion in the iVotosoa— Phosphorescence and
Digestion — Digestion in the For if era, Coelenteratci, Echinudennata,
TriehoteoUces, Nematoteolkes^ Cfuetognatiia, Arthropoda, Polyzoa^

CONTENTS.

Braehiopoda, MoUutea, Hemichirrdalo, and Urociiorilala — General
BainBikB conceinlDg Digestion in tbe Invertebrata

CHAPTER IV.

.gesiion eontiaued: DiaBSTIOir in PABTicr lab— Digestion in tho
IVotosoa: Ho specialisation of parts— Digestion In the Pori/era
and Qtlmltrala : Researches of Greenwood, Lankoster, HaSckol.
Voigt, Cieokowski, MacMimn, Kredericq — Digestion in the
EehiHodermala : Researches of Fredericq, Griffiths, MaoMunn —
Digestion in the Tyichmeolicet : Experiments of Frederioq —
Digestion in the A nntltdn : Researches of Fredericq tuid Griffiths ;
the Fiuicreatic Function of the so'calletl " Liver " — Digestion in
the Itiaecta and Aruckniilu : Researches ot GrifHths on the
Sallrary Glands and "Livers'' of the Imecta; Lowno on the
Malpighian Tabules of CuUiphora ; Von Planta, Leuckart, and
Schonfeld on the Food Stuil of Bees ; the ReaesTchos of Griffiths
and Johnstone on the Solivarj Glands and " Liver " of the Spider
— Digestion in tho Vrtataeta ; Investigations of Griffiths on the
" Livers" of the Jlrachi/ura and Macroara ; Stamati's Investiga-
gatlons on the Gattric Juice of the Crajliah— Digestion in the
LamtUibranthiata : Researohea of Fredericq. Griffiths, and
Mao Hunn— Digestion in the Oatterapada : Investigations of
Griffiths, Levy, and Fredericq — Digestion in the Cephalopoda t
Reaearohes ot OriOiths, Krnkenberg, Fredericq, and De llellesme
on the " Livet " (Pancreas) of Sepia — Digestion in the TuHieata^
CoDStitnents of the Secretions of the Salivary Glands and Pancreas
(io-called " liver") in the InvrTiclmiia, &e. . . ■ 79 ,

CHAPTER V.

Absorption in the laverltbrala : No Distinct Set ot Vessels— The
Function of the Typhlosole — Absorption bj the Alimentary Caaal
and Blood-vessels— ALsorptton in the Protoioa: Protozoan Absorp-
tion due to Excitability or Irritability of the Cell— Absorption in
the Pwlfera, Cirienterata, Echinodenaatti, CtnioiJta, AntieUdii,
Mj/riopoda, Innxla, AriKhnulo, Cnularta, l^yzoa, BraxJiyopoda,
and llMutea — General Remarks on Absorption, ka

CONTENTS. xiii

CHAPTER VI.

PA.GB

The Blood in the Inveriebrata : The Size of some Invertebrate Cor-
poades — Coagulation of Invertebrate Blood — The IVotozoa and
JPorifera devoid of Blood — The Blood in the Aetinozfta and.
Eehinodermata — The Blood in the Myru^toda : Three distinct
Corpuscles — ^The Blood in the Annelida : The Fluids of the
Perivisceral Cavity and the Pseado-hsBmal System ; First appear-
ance of a Coloured Corpuscle ; Researches of MacMonn, Lankester,
Delle Chiaje, Schwalbe, Krnkenberg, and Milne-Edwards — The
Blood in the In$ecta: Pigments of the Blood; Researches of
Poolton and Fredericq ; Coagulation of Insects' Blood— The Blood
in the Cnutacea: Investigations of Fredericq; Percentages of
Saline Matter in Crustacean Blood; Densities of Crustacean
Blood ; Blood of the MoUusca : Researches of Griffiths, Cu^not,
Fredericq, 'and Krukenberg ; Transport of Oxygen by means
of Hnmocyanin ; Percentages of Saline Matter in MoUuscan
Blood; Saline Composition of MoUuscan Blood — The Chro-
matology of Invertebrate Blood : Researches of MacMunn,
Poulton, and others ; The Hemoglobin of Lumbricm ; Micro-
spectroscopes — Griffiths' Researches on the Gases of the Inverte-
brate Blood — General Remarks, &c. . . . . .125

CHAPTER VII.

Circulation in the InverttbraJla : Fusion of Circulation and Digestion
in the Protozoa^ Borifera^ and Codenterata — ^Blood and Vascular
Systems in the Eckinodermata and Annelida — Circulation in the
TrickoieoUoes, Arthropoda, Polyzoa^ Braehiqpoda, MoUuBcay and
TunicaJla^ kc 182

CHAPTER VIII.

Respiration in the Inveriebrata : Respiration in the Prototoa, Porifera^
Codenieraia: Respiratory Pigments; Researches of Moseley,
MacMunn, M^Kendrick, Krukenberg, and De Negri ; Internal or
Tissue Respiration; Respiration in the Echinodermata ; Investi-
gations of Dug^s, MacMunn, and Foettinger — Respiration in the
TriehoBcoUees and Annelida : Researches of MacMunn, Geddes,
Beddard, and Yejdovsky — Respiration in the NematoeeoUcet :

xiv COiXTENTS.

BiiDge'e Investigations OB Respiration ia ^««ari«^BeBpiration in
the Myriapoda and Ineeaa : Griffiths and Ljonnet on tbe Powei
of certain Inaecta resisting Aephyiia ; Tiachen and Tracheal
Gills; TiSBiie BeEpiration — Respiration in the ^rocANu/a; Respira-
tion by Tiachen, " Lnngs/' and the General Surface of the Body —
Respiration b? Branchiae and Pigments — Activity of Respiration —
Respiration in the IWyzoa, Braehiopoila, MoSuica, and Tunioata—
General Rctnarlu on Invertebrate KespirHtion, Ac. .

CHAPTER IX.

Secretion and Excretion in the Ineerlt^atu : Genetid Remarks on
Secretion and Eiccetion — The Prototoan Contractile Vacuole —
Secretion of Lime Oarbonatu in the CaUntcrala : Researches of
Mnrrajand Irvine— The Excretory Organs in the Echinodtrmata :
Investigations of Griffiths on the Renal Organs of Urailer — The
Renal Organs to the .'laiiiJiWn and .Veniotorifaa— The Secretion of
Viscid Matter by the Prolofraelieiila—ExcTelOTj Function of the
Malpighian tubules in the Hyrinpixla — Poisons secreted by Insecta :
Researches of Poulton ; Tbe Salivary Glands in the LrpiitopUrn
and their Function ; Grlfliths' Researches on the Renal Function
of the Malpighian Tubules in the /irice'ii— Tbe Arachnida : Poison
Glands of the Arlhroyaitra and Arancmn ,- The Arachnidiom of the
AroHeinn ; Investigations of Griffiths, Johnstone, and Weiniand
on the Renal Organs in the Arrmtintt—Tbe Criatacta .- The Shell-
gland a Renal Organ ; Keeearcbes of GriffitliB on the Green Glands
of J»(ucu»— Tbe Braehiopoila : Secretion of tbe Shell ; tba
Functions of the Psendo- hearts— Tbe JloUmca: SecreUon of
Lime Carbonate by tbese AnimaJs ; Formation of Pearls; Re-
searches of Irvine and Woodhead on Shell- formation ; Researches
ofOrlSltba aud Follows on the Organ of Bojanus ; Researches
of MaoMunn, Griffiths, and others on the Function of tbe
Mepbridia in the Hollvica; Secretion of Mucus by tbe Pubiio-
giuUropoda—Nenea and the Phenomena of Secretion— The
Invertebrate Kidney— Comparison of the Invertebrate Eldnej
with that of the riTff/)rQ(o,i:c. . . . . .2

CHAPTER X.

Nervous Systems of the /wi'o'feirn/n .■ General remarks ; Nerve-centres,
Nerve fibres ; Functions of Nerve- fibres— The Diffased Nervous

CONTENTS. XV

PA.OB

System of the Prototoa — Ledenf eld's Investigations on a Nervous
System in the P^fera — ^The Nervous System of the Ccdenterata :
Researches of Kleinenberg, Romanes, Haeckel, Hertwlg, and
others ; Experiments of Romanes on the Nervous System of the
Jfedtisoe: Elmer's Investigations on CtenopTwra — The Nervous
System of the Behinodermata : Researches of Romanes, Bwart,
Fredericq, Prooho, and Hamann ; Internal and External Nerve-
plexuses of JEchintu — Nervous Systems of the Trichoacolices, Anne-
Kdot NematoiooiiceB, Chcetognatha^ Prototracheata^ and Myriapoda —
The Nervous Systems of the hisecta : The Cerebral Ganglion or
Brain — The Nervous Systems of the Aracknida and Oruatacea :
Investigations of Sars, Fredericq, Vandeveide, and Griffiths— The
Nervous Systems of the Polyzoa^ BrcuHiiopodcty MdUuaea^ and
Ihtnieaia, &c. ........ 293

CHAPTER XI.

The Organs of Special Sense, &c., in the Invertebrata : Tactile Sensi-
bility and Sight in the Protozoa and Porifera — The Ccdenterata:
Rudimentary Eyes and Olfactory Organs in the Medusoi — The
Echinodermata : Tactile Sensibility ; Sense of Smell : Experiments
of Griffiths; Sense of Hearing ; Eyes: Researches of Romanes
and Ewart — The Sense-organs in the Trichoaeolices, Annelida^
KemaJt090olice8^ Chaiognatha, and Myriapoda — Sense-organs in the
Imecta : Tactile Organs ; The Senses of Taste, Smell, and Hearing ;
Simple and Compound Eyes of Insects, Mosaic Vision; The
*' Voices " of Insects— Sense-organs in the Crustacea : Blind Cave-
crabs, Cirripedia^ Crayfishes, &c. — Sense-organs in the MoiHuaca :
Organs of Touch, Taste, Smell, Hearing, and Sight ; The Cepha-
lopod Eye — Intelligence or Reason in certain Invertebrates, &c. . 345

CHAPTER XII.

Movements and Locomotion in the Invertebrata : In the Protozoa :
Pseudopodia, Flagella, and Cilia as locomotive organs ; Researches
of Dallinger and Drysdale ; The Muscular Fibre in the Peduncle
of VorticeUa — Movements in the Porifera — Locomotion, &c., in the
Coilenterata: Researches of Romanes— Locomotion, &c., in the
Trichoeeolieei, Annelida^ NematoscoUces, and Myriapoda; Loco-

xvi CONTENTS.

PACK

motion, &c., in the Imeda : The Flight of Insects—Locomotion,
&c., in the Araehiida, Crutiacea, and MoUtuca^ &c. . 374

CHAPTER XIII.

Reprodaction and Development in the InverUbrata: Spontaneous
Generation, Gemmation, Fission, Endogenous Cell Formation,
Parthenogenesis, Seznal Reproduction, Hermaphroditism, Sexual
Elements 'of Reproduction, Fecundation, Development of the
Embryo, and Conjugation — Reproduction in the Protozoa : Investi-
gations of Dallinger and Drjsdale and others— Reproduction, &c.,
in the Ihriferaf CcdenUrata^ EcMnodermeUa, TViehoacolices^ Anne-
UdOf NematoBcoUeetf Chcetognatha^ Onychopkora^ and Myriapoda —
Reproduction, &c., in the Insecta: their Odours, Colours, Dances,
and Music, as Agents in the Reproduction of the Intecta — Repro-
duction in the Arachnida, CruMtacea^ BoHyzoa^ BrachiopodcL,
MdUutca^ and Tanioata — Concluding Remarks : Fleomorphism,
Origin of Life, &c. ....... 399

Appendix ......... 457

INDRX OF Authorities . 461

Subject Index ........ 465

THE

PHYSIOLOGY OP THE INVERTEBRATA.

CHAPTER I.

I N T K O D U C T I O N.

Anlmal physioloffy may be defined as that branch of biology
which is concerned in the elucidation of the various functions
which take place in the animal economy. It is a branch of
study quite distinct from morphology, chorology, and setio-
logy ; and as a separate branch of biological science we propose
to treat it in the following pages.

Researches undertaken to investigate accurately the proper
physiological functions of the various organs and tissues of
the lyunidtrata were greatly needed; and it is only during
the last few years that certain biological chemists — fully
equipped with the necessary manipulative skill — have con-
siderably advanced this important but much-neglected branch
of biology.

If one studies any particular organ from only one aspect,
incomplete or erroneous conclusions are apt to be drawn.
For instance, the vesicular tissue lying in the rectal loop in
Asculia^ and in some species extending over the intestine, is
well known to be renal in function. This vesicular tissue is
a true kidney physiolof/ically ; morphologically it is another

3 PHYSIOLOGY OF THE INVERTEBRATA.

matter, and depends upon one's definition o£ a true kidn^JI
Emh-ifoliyienllii these voaicles are the remains of a part of t
original colon.

As more attention has been paid to the morpliology of thel
IiLrcrtcbmln, it is not onr object to speak of that branch of I
the subject farther than is necessary ; but in some cases the |1
function of an organ or a tissue cannot be comprehended^fl
without referring to its anatomy.

According to the great apostle" of biological thought, " thu
actions of living matter are termed its fmictiom ; and thei
functions, varied as they are, may be reduced to threftl
categories. They are either — f i) Functions which affect tho'l
material composition of the brjdy, and determine its mass,]
which is the balance of the proceBses of waste on tlie one I
hand, and those of assimilation on the other. Or (2) they
are functions which sub8ei"ve the jjrocess of reproduction,
which is essentially the detachment of a part endowed with
the power of developing into an independent whole. Or (3)
they are functions in virtue of which one part of the body is
able to ejcert a direct influence on another, and the body, by H
its partrS or as a whole, becomes a source of molar motion.
The first may be termed nustenfaikr, the second fjencratirr.
and the third i-omhdh-c functions. In the lowest forms of
life the functions which have been enumerated are seen in
their simplest forms, and they are exerted indifferently, or
nearly so, by all parts of the jirotoplasmic body ; and the like
is true of the functions of the btidy of even the highest
organisms, so long as they are in the condition of the
nucleated cell, which constitutes the starting-point of their
development. But the first process in the development is
the division of the germ into a number of morphological
units or blastomeres, which eventually give rise to cells ; and
as each of these possesses the same physiological functions
as the germ itself, it follows that each morphological

' ProtHoiley.

PHYSIOLOGY OF THE INVERTEHRATA, 3

unit is also a physiological unit, and the multi-cellular
mass is strictly a compound organism, made up of a multi-
tude of physiologically independent cells. The physiological
activities manifested by the complex whole represent the sum,
or rather the resultant, of the separate and independent physio-
logical activities resident in each of the simpler constituents
of that whole.

*'The morphological changes which the cells undergo in
the course of the further development of the organism do
not affect their individuality; and, notwithstanding the
modification and confluence of its constituent cells, the adult
organism, however complex, is still an aggregate of morpho-
logical units. Nor is it less an aggregate of physiological
units, each of which retains its fundamental independence,
though that independence becomes restricted in various
ways.

''Each cell, or that element of a tissue which proceeds
from the modification of a cell, must needs retain its susten-
tative functions so long as it grows or maintains a condition
of equilibrium; but the most completely metamorphosed
tjells show no trace of the generative functiou, and many
exhibit no correlative functions. Contrariwise, those cells
of the adult organism which are tHe unmetamorphosed
derivatives of the germ exhibit all the primary functions,
not only nourishing themselves and growing, but multiplying
and frequently showing more or less marked movements."

The cell theory, first ably worked out by Schwann, has led
physiology, aided by chemical means, to scrutinise more
profoundly the mechanism of the vital acts ; it has taught it
to refer them to their ultimate agents — that is, to the histo-
logical elements themselves, which vary in function and in
form in complex beings, and which we must consider as
playing a part in the mechanism of organised beings
analogous to that of atoms in chemical molecules.

In the lowest animals all functions are performed by all
tissues: the sarcode of an amoeba assimilates, breathes.

4 PHYSIOLOGY OF THE INVERTFJiRATA.

excretes, and reproduces — for no special part is set aside for
the fnnctioDS of digestion, of respiration, of excretion, of re-
production. There seems to be in the lowest Invertebrates a
confusion of organic materials and functions. Many of the
Protozoa are endowed with motility and sensibility, with ft
sort of instinct ; ' and yet, as far as we know at present, they
are destitute of muscular and nen'ous elements. Possibly
the Barcode is the rudiment, still undivided, of nuiscnlar
fibre.

But as we ascend gradually from lower to higher forms
the diffei-entiation becomes more marked, and we find par-
ticular parts of the body reserved for special actions. But
this difierentiation passes through various stages before
arriving at the most differentiated forms of animal life. Afl
already stated, the single cell of the nmceba performs many
functions ; and even when an organ has arrived at Mich a
st^e that it is quite distinct, it may have a dual or triple
function — as, for instance, the pentagonal pyloric sac of
ITraslcf ritUiiit (one of the Asf'-rulm) has been proved to
have a dual function. t It ia a digestive gland as well as an
excretorj' organ, separating the niti-ogenous products of the
waste of the tissues, &c.. from tlie blood in the form of uric
acid, which is to be found in the five pouches of that
organ. In TVic On;fin of Specu's (chapter vi.) Darwin mentioas
the fact that " numerous cases could be given among the
lower animals of the same or^u performing at the same
time wholly distinct functions : thus, in the lar\'a of the
dragon-fly .... the alimentary canal respires, digests, and
excretes." But as we pass from the lower to the higher
forma of animal life the various organs have special functions
assigned them. This rule not only applies to the physio-
logical functions of various organs, but also to their ana-

• See Ilinet'B AjicAip f.lfi of Mkro-Orgam,m,.

t See Dr. A. B. GrlfKilw' papers in the Proeetiliu/s of Royl Soa'etif of
LoBiIoii, vol. 44, p. 32s ; "id tlie Proaeil'iigf of Ret/ol daeiely iff fUixbutyA,

PHYSIOLOGY OF THE INVERTEBRATA. 5

tomical elements. The more simple is the organisation of an
animal, taken as a whole, the simpler is also the structure of
each of the orders of anatomical elements. For example, the
muscular fibres of the Radiata^ Anmdom, and Mollusca are
simpler than the same elements in the crab (Robin). But in
the higher animals there is a complete differentiation of parts
into organs having special physiological functions and varied
degrees of structure. In fact, the important law of Von Baer
— " the law of progress from the general to the special " —
reigns supreme in the organic world.

In the higher Invertebrates the various organs are localised
in different parts of the body. One area is restricted to
digestion, another to circulation, a third to respiration, and
a fourth to reproduction. The more highly organised the
animal, the more divided is its body into sepai'ate and dis-
tinct organs, each endowed with its own special function.

The main object of this volume will be to consider in
detail the physiological functions of the various organs in
the Invertebi^ata ; but as it is impossible to investigate func-
tions without a knowledge of the organs performing them,
we shall refer (when necessary to a proper understanding of
the mechanism described) to their anatomy.

As we shall have to allude to numerous classes, &c., of
animals, a classification of the InvertcbrcUa will hardly be out
of place in concluding the present chapter.

The following tables are founded on the classifications of
Professor Huxley : —

PROTOZOA.

Monera.

Protoplasta.

Gregariaida.

CataUacta.

Infusoria.

Foraminlfeia.

Radiolaria.

(a) Heliozoa.

(6) Cytophora

PHYSIOLOGY OF THE IKVERTEBRATA.

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PHYSIOLOGY OF THE INVERTEBRATA.

I ii

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llill

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PHYSIOLOGY i>F THE 1 XVERTEBRATA.

V, MAI^COZOIC SKB1E8.

VI. Phabvkoop-

NBUBTAL SerIRS.

Uslaoggoolicei.

Mollnsca.

BraoMopoda.

Phylaetolnmata

GfiiiQolBmalA

PcdieeUinea

ClistCDtemta

chiata

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Gasteropoda

(a) Pnlmogas-

('.) Branchio-

Pteropoda

('0 Dlbnn-
chiata

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branchiaW,

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UruchordRta
(TuniMU)

■

If snimala are looked upon as machines for doing work,
they differ from one another in the extent to which thi»
work is subdivided, ■■ Each subordinate group of actions or
functuyns 18 allotted to a particular portion of the body,
which thus becomes tlie organ of those functions; and the
extent to which this division of physiological labour a
carried differs in degree within the liniita of each common
plan, and is the chief cause of the diversity in the working
out of the common plan of a group exhibited by its members.
Moreover, there are certain types which never attain the sania
degree of physiological differentiation as others do

Thus, some of the I'miozm attain a grade of physiological
complexity as high as that which is reached by the lower

call
rer ^1

PHYSIOLOGY OF THE INVERTEBRATA. 9

Atetazoa. And notwithstanding the multiplicity of its parts,
no Echinoderm is so highly differentiated as a physiological

machine as is a snail It is not mere multiplication of

organs which constitutes physiological differentiation; but
the multiplication of organs of different functions in the
first place, and the degree in which they are co-ordinated,
so as to work a common end, in the second place. Thus,
a lobster is a higher animal, from a physiological ix)int of
view, than a CydapSy not because it has more distinguishable
organs, but because these organs are so modified as to per-
form a much greater variety of functions, while they are all
co-ordinated towards the maintenance of the animal by its
weU-developed nervous system and sense-organs. But it is
impossible to say that, e.(/,, the Arthropoda, as a whole, are
physiologically higher than the Molhisca, inasmuch as the
simplest embodiments of the common plan of the Arfhrofwdu
are less differentiated, phyjsiologically, than the great majority
ofMollusks." (Huxley.)

CHAPTER 11.

THE CHEMISTRY OF PROTOPLASM.

Before commencing our study of the physiology of the
Inraich'ata in detail, we offer a few remarks concerning the
chemical nature and supposed composition of protoplasm.*
or albumin. As the complex molecule of albumin is the
basis of all physiological functions — in fact, "the physical
basis of life" — no apology is needed in bringing this chapter
before the attention of our readers.

Many chemists have submitted albumin to ultimate ana-
lyses. Among these may be mentioned the following : —

Carbon

Hydrogen

Nitrogen

Oxygen

Sul])hur

rt O

53-4

7.1
15.8

■

•

Mulder.

52.9

53.3

53.5

1
53.4

7.2

7.1

7.2

7.0

156 .

157

15.8

15-7

22.1

22.3

I.S

1.7

1.6

54.3

7.1

15.9

53.1
7.0

B .

ts £7
oc

52.6

7.1

— 16.3

1.3 I 1.8

Besides the above elements, there is always present in proto-
plasm a small, but variable, amount of ash, which contains
phosphorus and other elements in infinitesimal quantities.

* From vpunot (first), Jind xXdcr/ua (formed substance).

PHYSIOLOGY OF THE INVERTEBRATA, ii

Albumins are incapable of being crystallised, or, if they
are present in some tissues in an apparently crystalline
condition, they are not crystals in the true sense of the word.
These pseudo-crystals are readily recognisable beneath a
microscope, for they dissolve in a dilute solution of potash,
and are stained yellow by nitric acid.

A solution of iodine colours albumin or protoplasm brown,
while sulphuric acid colours it red. Carmine deeply stains
duul protoplasm, but has no action on living protoplasm.
Dilute mineral acids and alcohol coagulate albumin ; but it
is soluble in concentrated hydrochloric acid. According to
Dr. F. Hoppe-Seyler,* albumin has a specific rotatory power
of from- 35. 5*^ to- 56°. A temperature of about 50° C. co-
agulates albumin ; ix,, it is converted into an isomeric modi-
fication by the action of heat, as well as by dilntc acids, as
already stated.

Albumin combines with hydrochloric, sulphuric, phosphoric,
. and acetic acids, forming albuminates. It also combines with
certain bases and salts, forming similar compounds. It was
the albuminate of potash which gave Lieberkuhn the means
of ascertaining the empirical formula of this complex chemical
compound. Lieberkiihn's formula for albumin is represented
as follows : —

The above formula gives no idea of the atomic constitution
of albumin.

Dr. C. Schorlemmer, F.R.S. {Rise and DevelopinmU of
Organic Chemidmj^ p. 1 23) says : " The enigma of life can only
be solved by the discovery of the synthesis of an albuminous
compound.'' The direct synthesis of albumin has not yet
been performed ; but during the past nine or ten years some
excellent work has been done by Loevv and Bokorny in this
line of research, which opens a vast field of inquiry for
the physiological chemist. These chemists have paved the

* Handbuch der Physioh^fisch- u»d Pathologhrh-CheiniscJien Analyse,

12 PHYSIOLOCY OF THE INVEKTEBKATA.

wny for the synthesis* of this componnd ; wid in thf
searches " on living and dead protoplasm, they have atriveil
at the conclusion that living protoplasm contains an ftlde-
hydic group of elements. In their experiments on the living
protoplasm of the fresh-water algie, Sinro'jijni and Xyipumtit
growing in spi-ing-water containing o.i per cent, of dipotss-
Biura phosphate and ammonium nitrate, Loi-w and Bokomy
found that the living cells had the power of reducing ailver
from very dilute alkaline solutions of saltf^ of that metal.
Dead cells do not give this reaction.

Lofw and Bokorny have esperimented (with the
result) npon the cotyledons of -^!.'^ia/i^/(»s rtvi iiiM, the epidei
hairs of plants, the sap of the pine and oak, the cells of fruits,
fungi, and also many of the In/nsori'i. They conclude
from these ohservationa that living protoplasm contains an
aldehydic group of elements, whereas thei-e is no such gronjK'
in dead protoplasm.

Keinke {/ATWi/f i/n- JJn-Mim Chemvo'hni h\'«-!h.-fia/(, vol,
14, p. 2144; vol. IS, P- 107) says that the aidehydic nature,
as tested by an alkaline silver solution, is only a property of
the protoplasm of the chlorophyll, for he failed to find it in
the protoplasm of cells in unopened buds ; therefore he thinks
it is probable that it is formed only in the presence of sunlight
by the chlorophyll corpuscles.

Mori (Cliemisiif'i VmtraMatt [3], vol. 1 3, p. 565) couniders
that formic aldehyde is the first product of assimilation, for
he detected (by the action of a solution of silver nitrate) a
substance which reduced the nitrate in plantu containing
chlorophyll which had be<-n exposed to sunlight. When the
same plants were left for about forty-eight hours in a dark
place, so that on applying the test again tlie first protliicts of
aasiinilalion might be used up, no reduction of silver nitrate

* Die ChimUche KraJI'/ucUe I'm Ulmitdti Protuiiiama; also JlrrieUr lUr
DmttdKn Chtmitehta QeaiUaehaft, vol. 14, p. ijoS ; vol. 15, p. 695;
jyiUffir't Arcfiii' far I'hfftiologir, vol. 35, p. 150 ; vol. 45, p. 199 ; and Sol.

PHYSIOLOGY OF THE INVERTEBRATA, 13

took place. Therefore, both Beinke and Mori support Baeyer's
theory that formic aldehyde is formed by chlorophyll under
the influence of light from the carbonic acid of the atmosphere
in the presence of water :

fCO, = CO + O) fH

(H,0 = H, + 0/ ' ^ ICOH.

Dr. Kretzschmar {Bicd^irniannH Centralhlatt fur Agrvndtur^
Chemie^ 1882, p. 830), on the other hand, states that the
protoplasm of living and dead cells reduces silver from an
alkaline solution of the salts of that metal, and so concludes
that this reagent fails to distinguish between living and dead
protoplasm.

The author * has also shown that the alkaline solutions of
copper (cupric) and silver salts are reduced by both living
and dead protoplasm. In fact, these reagents fail to dis-
tinguish between living and dead protoplasm, but these
investigations do not disprove Loew and Bokomy's idea that
protoplasm (i.e., living and dead) contains an aldehydic group
of elements ; but this particular group of elements is only one
of many combinations of elements forming the complex
molecule of albumin.

When we study the decomposition of albumin (both animal
and vegetal) by the agency of different chemical reagents,
we begin to see that its chemical constitution is not repre-
sented by any simple group of elements. Many of the
substances found in the animal body are products of the
metabolism of protoplasm — e.y,, urea (CNjH^O), creatine
(C^H,N,0,), creatinine (C^H^NjO), cholesterine (C^H^Pj), uric
acid (C,H,N,0,), guanin (CjH.N.O), leucin (CeH^jNO,), tyrosin
(C.H,,N03), &c.

Professor P. Schtitzenberger (Comptvs-Rendus, vol. 106,
p. 1407) has shown experimentally that when albumin is
boiled with barium hydroxide, it yields leucin, leucein, and
the products of hydration of urea and oxamide ; and Dr. W.

* Tht Chemiefd NeivSt vol. 48, p. 179 ; Journal of Royal Microscopical
'^iociety, 1884, p. 249; Journ. Chem, Soc. 1884, p. 202.

■4 PHYSIOLOGY OF THE INVERTEBRATA.

Palladin iJJi-richk da- Dcidm-ltcn Botan. iltmilschaft, vol. 1
p. 296), and Drs, Hchulze and Kisser (Liiiiih'-. KfV.tKc/iJi-iSVaf.,
vol. 36, p. 1^, have shown that vegetal protoplasm can be
made to yield tyrosin, leucin, xanthine, hypoxonthine, and
Bimilar compounds, which are nndoubtedly some of the j
ducts of the decomposition of albumin occurring in the I
of liviJig animals. If protoplasm or albumin gives rise t
such compounds as the above, we have good reason to beliw
that its constitution is more complex than Loew and Bokomjl
would have us suppose. Many of the substances formed™
during the decomposition of albumin have been artificially
prepared in the Inboratoiy. For instance, leucin is very
largely diffused in the animal organiatn, and has been obtained
artificially by oxidising amyUc alcohol with jtotassium bi-
chromate and sulphuric acid, and then distilling, when the
following reaction occurs : ■

2C,H„H0 + O,

[Amjiic alcohol.]

2C,H,COH + 2H,0.

[Valeric aWelij'ie.]

When valeric aldehyde is treated with ammonia, valeroi
ammonia is formed, and if the latter compound is digested
with hydrocyanic and hydrochloric acids it is converted inl
leticin :

00 C.H,.COH .

NH, = C.H.CH(NH,)OH.

[Valeral ummonia.l

itO^H

(b) C,H„CN(NH,)OH + HCN + H,0 =

[Leucin.]

Aiuido-isovaleric acid (a substance which occurs in the
pancreas of the ox J, amido-butyric acid, and amido-propionic
acid, have been obtained by Schtitzt-nberger' from albumin ;
and all these substances have been obtained artificially 1
laboratory.

}Mplti-/ien>liii, mla. Kl anil H4.

Lcially in the^H

PHYSIOLOGY OF THE INVERTEBRATA, 1$

Dr. Gackelberger {LicbiijH Amwlmiy vol. 64, p. 39) obtained
caproiCy valeric, butyric, propionic, acetic, and formic acids by
oxidifflng albumin with potassium bichromate and sulphuric
acid. As these organic acids can be obtained artificially from
cyan-alcohols, it has been stated that albumin or protoplasm
is a compound of cyan-alcohols or cyanhydrins united to a
benzene nucleus.

By looking upon albumin as built up of cyan-alcohols, we
can readily account for the formation of such compounds as
glyoocine, leucin, the acids of the (\Hj„^jCOOH series, as well
as those of the lactic series — occurring in the animal body.

In the year 1828 W5hler converted ammonium cyanate
into urea; and Dr. Pfl tiger {Fjliujcr\ Archir, vol. 10, p. 337),
in calling attention to the great molecular energy of the
cyanogen compounds, suggested that the functional meta- .
bolism of protoplasm by which energy is set free, may be
compared to the conversion of the energetic unstable cyanogen
compounds into the less energetic and more stable amides.
In other words, that " ammonium cyanate is a type of living,
and urea of dead nitrogen, anjd the conversion of the former
into the latter is an image of the essential change which takes
place when a living proteid dies."*

Dr. P. W. Latham, in ** The Croonian Lectures" for 1886,
ably argues from experimental data that albumin or proto-
plasm has the following constitutional fonnula :

* See Foster's Text-book of Phyalolof/f/ (4th ed.), p. 749.

PHYSIOLOGY OF THE INVERTEBRATA.

S(),1I- -C

H V

{;

C-H

^'"•"ICNOH

C,,H„

^i** 10 •.

C,H,

C.H,

C,H,

CjHj \

^»H, •

C,H

C,H,
C,H,

ClI,

CH.

CH,

CH.

CH,

-CH

6 •,

CNOH

CXOH

CNOH

ICNOH

CNOH

PHYSIOLOGY OF THE INVERTEBRATA. 17

This substance, whose cjomposition is Cy,H„jNjgO^S, differs
from Dr. Lieberktthn's empirical formula (C,,H,jjNjgO„S) only
by six atoms of hydrogen.

According to Latham, albumin '^ is a compound of cyan-
alcohols united to a benzene nucleus, these being derived
from the various aldehydes, glycols, and ketones, or that they
may be formed in the living body by the dehydration of the
amido-acids ; that from a body so constituted all the different
substances may be obtained which have been extracted from
albuminoid tissues ; that lactic acid is obtained in two ways,

OH
either from C,H^<;;^p^ or from changes and condensation in

CH,\pT^ with the simultaneous development of carbonic

anhydride, a result which is brought about when a muscle
contracts or when it dies; and that urea may be obtained
from one series of cyan-alcohols with the production of a
cyan-alcohol higher in the series.

" Such a compound of cyan-alcohols therefore, presenting
so much resemblance in its properties to albumin, cannot
differ very widely (though perhaps not absolutely correct)
from the molecular constitution of albumin.

*' Taking this view, then, of the constitution of albumin, the
following may be given as a summary of the nutritive
changes : The amido-acids — glycocine, leucin, tyrosin, &c. — in
passing from the alimentary canal to the liver, are dehydrated,
forming a series of cyan-hydrins or cyan-alcohols attached to
a benzene nucleus, and then pass into the circulation. In the
tissues these cyan-alcohols, partly by condensation, partly by
hydration and oxidation, give rise to the various effete
products which are eliminated from the system in the form
of carbonic acid and urea."

There is no doubt that the theory of protoplasm being
a complex molecule,* derived from various aldehydes, glycols,

* See also a paper by Dr. P. Schiitzen in the Cumptes-Jitndut, tome 112,
p. 198.

1 8 PHYSIOLOGY OF THE INVERTEBRATA.

and ketones, aids lis considerably in understanding the orig^ J
of various secretory products found in the Tiuvrtehrata as weil J
aa in the Vtrtdii-ata.

Living protoplasm is a substance which is constantly
undergoing chemical changes. It is the chemical anJ
physical properties of this complex substance, diversely
raodiGed, which underlie all the vital functions — nutrition,
secretion, growth, reprodnction, motility, &c. Of these
functions the most important is nutrition, tlie double and
perpetual movement of molecular renovation of the living
substance. Without nutritiou there can be no growth, no J
reproduction, no movement, and in fact no physiological i_
function whatsoever. It has been stated that " life can txM
conceived of as reduced to its most simple expression, tvl
mere nutrition. A being capable of nourishing itself, antt|
destitute of every other property or function, which, after allj
is only a simple extension of the nutritive property, its 1
will be only an individnal life;" a time will come when thff
nutritive functions will have less energy — then " the nutritive
residue, incompletely expuUed, will impregnate the living
tissues and liquids obstructing them." Such obstruction
necessarily interferes with physiological activity, and ulti-
mately ends in complete arrest. When this stage arrives,
the organism, no longer capable of adjusting its '' interDal
relations to external relations,'"* undei^es those chemico-
biological changes which finally result in its molecules (as
new combinations) once more re-entering the mineral kin^
dom — or the world of inanimation. On the other hand, if
the nutritive activity of a living organism " is sufficiently
energetic to rise, as it were, to excess, even to growth and
reproduction, the being is sure of living in its offspring ; it-
fills its place in the innumerable crowd of living beings, and
can even, according to the doctrine of evolution, become
the source of a superior organised type, can ascend in the
hierarchy of life,"

• Mr. Herbert Spencer's definitiou of "life."

PHYSIOLOGY OF THE INVERTEBRATA. 19

From what has been said in this chapter it will be gathered
that '* a mass of living protoplasm is simply a molecular
machine of great complexity ; but it must not be supposed
that the differences between living and not-living matter are
sach as to bear out the assumption that the forces at work in
the one are different from those which are to be met with in
the other. Considered apart from the phenomena of con-
sciousness," Professor Huxley says, " the phenomena of life
are all dependent upon the working of the same physical and
chemical forces as those which are active in the rest of the
world."

CHAPTER III.

DIGK3TI0S IS THE 1XVERTEBRAT4.

DynsHon in General.

In tliia chapter we have to trace the function of di'jtsl\
from its lowest or moat general form to that stage when it
nearly approaches in complexity the digestive process occur-
ring in the backboned animals.

Digestion is that process whereby food is taken into an
organism, and there made fit to become part thereof — i.t.,
the digested food becomes assimilation, for in the living
organism, however low in the animal scale, there is never
any repose. The organism has to reckon with its environ-
ment; oxidation is always going on, therefore the digested
food is employed in the work of reparation and of recon-.
Btmction. Animal organisms cannot live without constantly^
absorbing complex organic substances. As they canaot
manufacture these substances, they obtain them from other
animals or from plants; hence we may divide even tho
lowest animals into either camivoroas, herbivorous, or omni-
vorous forms.

For the process of digestion the organism is furnished with
either a general or a special apparatus, whose office consistB
in forming a kind of physiological kitchen to modify the raw
materials, which renders them more suitable for assimilation
or absorption. This apparatus is the digestive system.

Many of the lowest animals are comparable to the lowest
plants — in fact, the two great kingdoms may be said to

PHYSIOLOGY OF THE INVERTEBRATA. 21

lap, for there is no sharp line of demarcation, as far as
digestion is concerned, between \}[m^ Protozoa and the j&io^eria.
For instance, if one compares the Gregarine (a parasite) to a
bacteriam or any other fungns, both forms live by assimilating
the products of decomposed organisms, or rather organic
matter ; thus showing that the lowest members of the animal
kingdom are closely allied to the lowest members of the
vegetal kingdom.

The mode of nutrition among the lowest animals is not
uniform — a fact which ought not to appear remarkable when
we bear in mind that these animals are made up of all manner
of heterogeneous beings that have nothing in common save
the microscopic smallness of their bodies and the simplicity
of their structure. In the animal kingdom three main types
of nutrition may be distinguished : —

(i) Holophytic or vegetal nutrition.

(2) Saprophytic or endosmosis nutrition.

(3) Animal nutrition.

The first type of nutrition or digestion is found in animal
cells that contain chlorophyll, and that nourish themselves
by forming assimilable substances from ingredients taken
from the medium in which they live. It should be borne in
mind that the function of chlorophyll in the animal as well
as in the vegetal kingdom is essentially that of nutrition^
and not of respiration ; although we shall see later in this
volume that many of the animal chromophylls (using the
word in its widest sense) have respiratory as well as other
functions.

A large number of the lower animals contain chlorophyll,
but these animals are met with chiefly among the Flagellata.
Their assimilative or digestive organs bear the name of chro-
matophores. These chromatophores are small granular masses
of protoplasm impregnated with a colouring substance. In
the centre of the chromatophore is a small bright globule
which is said to possess the same chemical reactions as

11 PHYSIOLOGY OF THE JNVERTEBRATA.

uuclein. Dr. Schmitz has named this small globule pyrenoiA* '
The function of the pyreiioid is the formation of starch and
similar carbohydrates. This is a process of digestion akin
to the vegetal kingdom.

It IB interesting to note that " the Eiiylewr (belonging to^
the FlaijcUaltt) might nourish themselves && animals do, for J
they^have a mouth and a digestive apparatus. The buccal,!
or oral, apertnre opens in the anterior end at the base of tin

C, costriclile vacuole; tl, eye or ocular spol; P, disk of
paramylone ; N, nucleus; Ch. chromnlophorcs.

M, moulh; B, eye; D, conlractile reservoir; C, contractile
vacuole.

flagellum, and is connected with a short gullet or ccHophagoB' 1
(Fig. i). Nevertheless the Eii;/Ieiia is never seen using itsl
mouth forawallowingalimentary particles. A curious problem "
is involved here. If it is true, as has been claimed, that it is
the function that makes the organ, hoiv do we explain the
existence, and especially the genesis, of this digestive
npparatus, which performs no function?"

The second type of nutrition or digestion in the

the animal ^M

PHYSIOLOGY OF THE INVERTEBRATA, 23

kingdom is that of saprophytic or endosmosis nutrition. It
•occnrs in the Gregarinida, &c., and is the simplest type of
nntritiony for the organism simply nourishes itself by
absorbing, through the whole surface of its body, the liquids
containing decomposing or digested animal and vegetal
substances.

The third and highest type of nutrition occurs in all
animals except those coming under the previously mentioned
types. In the highest type of nutrition the organism
'* seizes solid alimentary particles, and nourishes itself after
the fashion of an animal, whether it be by means of a
permanent mouth, or by means of an adventitious one,
improvised at the moment of Aeed."

Before describing in detail the great physiological functions,
it may be stated that " in organised beings, from the lowest
to the highest, the most differentiated, there is a graduated
hierarchy. From the physiological confusion which exists at
the lowest step of the ladder we pass, step by step, through
A series of organic models, better and better finished, to the
most perfect specialisation. Nothing is more interesting
than this seriation of organs, especially from the point of view
x)t the great doctrine of evolution, which more and more
vivifies all the branches of natural history."

The Protozoa.

(a) The Gregarina. — This animal (Fig. 2, a) infests the
interior of cockroaches, earthworms, and other Invertebrates.
It well illustrates an example of endosmosis or saprophytic
nutrition, for it absorbs or imbibes fluid nutriment by every
part of its surface, and most probably the effete matter is
likewise given out at every part of its surface.

Although the anatomical structure of the Gregarina gives it
a higher rank in the zoological scale than the Amoeba, the
latter organism is certainly its superior in the matter of
-digestion. It may be stated that the gradual specialisation of

24 PHYSIOLOGY OF THE INVERTEBRATA.

different fnnrtioas do not follow the same lines in the i
Bcrles. Nor will the advance of particular foncrions keep
pace with the advance in anatomical structnre. As far a»

A = Gregarina. B = Amtcba. C = MogosphEera. D = AcliDophiys,

E = AclinosptiieriuTn. F = I'Bit al E highly magnified.

:' = contiaclile vacuole. i = nucleus.

Etrncture is concerned, the Greffariiut ranks higher than tlu
Amceba.

(ft) The Amosbn. — ^In the Protopiatta, to which the Ama
belongii, we have a distinct advance in the mechanism o£'l

PHYSIOLOGY OF THE INVERTEBRATA. 25

digestion, for in this order one beholds the very birth of the
digestive function.

The Amceha (Fig. 2, b) seizes its food by extending some
portion of its cell. The extended portion is known as a
psendopodinm. The pseudopodium, after seizing the particles
of food, retract, and the food becomes incorporated in the
interior of the cell, which has the property of digesting and
absorbing the nutritive portion of the food and ejecting the
non-digested portion.

In some forms of the Protoplasta pseudopodia are extended
from any part of the protoplasmic cell ; whereas in others
(e.^., Pamphagiii) these non-diflferentiated prehensile organs
are extended from one particular region only of the cell. In
Arcella and Diffliigia, having an external covering or shell,
the pseudopodia are extended only from the single opening
present in each shell.

There is another point of difference between the Gregarina
and the Amcebcc — ^namely, the latter organism has a contractile
vacuole. It is possible that this vacuole is in some way
directly connected with the function of digestion, but there is
no doubt that it performs more than one function, for the
author has shown that at times the contractile vacuole of the
Amoeba acts as a renal organ (see later in this volume).

As far as the function of digestion is concerned in the
Protoplasta, every part of the protoplasm may be made to
serve as a digestive cavity in enveloping the food particles.
"A mouth region and an anal region are marked off for each
particular particle of food, but there is no mouth and there is
no anus."

(c) The Foraminifera, — These complex Protozoa may be
looked upon as colonies of AiJKebw connected together and
surrounded by a complex shell. They have been divided into
the Perforata and the Imper/orata, according to whether the
shell is either perforated or imperforated. In the former
class, the shell contains many apertures, through which the
pseudopodia of the particular individual dwelling within that

26 PHYSIOLOGY OF THE INVERTEBRATA.

division of the shell are protroded. In the Imperforata " the
food for the whole colony is seized and taken in by the
pseudopodia given off by the individual segment f oond in the
last-formed, and therefore most free cavity of the shelL"

Nearly all the Foraminifcra are marine animals ; whereas
the Aniixbcc chiefly inhabit fresh water, although some are
found in the sea.

((l) The Catallacta. — There is a morphological diSiarence
between this order and the Protoplasta, although the mechan-
isms of their digestive functions are closely allied.

Magosphccra (Kg. 2, c) which represents the Catalla/Ua,
protrudes pseudopodia which are broad at the base, while
the other extremities break up into a number of very fine
filaments. We may term these secondary pseudopodia.
Magosph(vra has a well-marked contractile vacuole.

{c) The Radiol aria. — One of the most common of this
order is Adinophrys (the sun-animalcule). It has stiffish
pseudopodia, '' which radiate from all sides of the globular
body." Adinophrys (Hg. 2, d) has a contractile vacuole, but
secretes no shell. In Adinospharrium (Fig. 2, e) the " central
part of the protoplasm is distingushed from the rest by con-
taining a number of endoplasts" (nuclei). Most of the
Radiolaina are simple and solitary organisms, but Sphanvzotim
and Collospharra form colonies.

In the case of AdinopJwys sol any part of the body serves
as a way of entry for food ; in fact it is a pantostomate being
(W. S. Kent).

(/) Infusoria, — Under this head Professor Huxley
includes —

In/w^ria Jlagdlata (the " ^lonads ").
Infusoria tcntacidifcra (the Acinda:).
Infusoria ciliata.

The Infusoria are the well-known inhabitants of water
containing decomposing vegetable matter. These organisms
differ entirely from those previously described, inasmuch as
they have a permanent aperture — the mouth. Beyond this

PHYSIOLOGY OF THE INVERTEBRATA. 27

aperture there is a distinct tube — a short oesophagus, which is
closed at one end, for it does not dilate into a stomach.
Although there is no further differentiation of this primitive
alimentary canal, it forms a distinct advance on the forms so
far described. The posterior end of the oesophagus is closed
by the protoplasmic mass of the cell. Food particles are
brought to the mouth by means of the vibrating flagellum or
flagella in the Infusoria fldgdlata^ or by tentacula in the
Infusoria tmtaculifera, or by cilia in the Infusoria cUiata,

In Monas vidgaris, one of the Flagdlata^ the food is dashed
by a sudden jerk directly against the oral aperture or mouth,
and the base of the flagellum presses the food particles into it.
According to Cienkowsky, bacteria, micrococci, and other
forms, which constitute the food of the Monas, " are pulled
into the latter's neighbourhood by strokes of the flagellum " ;
and Drs» Dallinger and Drysdale remark that certain forms
of the Flagellata are most voracious creatures. ** The * field '
in their neighbourhood is rapidly cleared of dead and living
bacteria, simply devoured by them. It is probable that this
capacity for absorbing nutriment, which must give large
advantage in the struggle for existence, explains the amoeboid
condition so common at what will be seen to be such an
important period in the development of the monads." *

Noctiluca (Fig 3, a) is another genus of the Flagellata. It
is extremely abundant in the upper layers of the waters of
the ocean, ** and is one of the most usual causes of the phos-
phorescence of the sea." Phosphorescence is associated with
the function of digestion or nutrition, for many micro-
organisms will not *' phosphoresce " unless supplied with
certain foods.t Noctiluca is a free swimmer. It is globular
in form, and possesses a strong flagellum. The central pro-
toplasmic mass is connected by many radiating filaments
with the external layer, and contains a gastric or food

* See Drs. Dallinger and Drysdale's paper in Monildy Microacopkal
Journal, 1S75, p. 194.
t Dr. A. B. GriflSths' book : Researches on Micro-Organisms^ p. 165.

i8 PHySIOLOGV or THE INVERTEBRATA.

Vftcnole, where the food is retained until digested. There \
no contractile vacuole.

The Infusoria IcniiicuN/ira, or Acineto' (Fig. 3, b),
organisms that move about very little— soine of them beiii

Fic. 3,— Types of Infi.soiiia.

Ktpresenling Ihe Flagtiiala. Ibe Ttnlarirli/tra, aud the Ciliala.

A = Nocriluca. B ■= Acinela. C r = VoitieelU. C a and 3 = Paramttciaa

Gi' = Gaslric vacuole. F = nagelluni. / = Trniacles. « = Nucleus.

T' = Coalraclile vacucle, ti = Mouih. 0 = l^LwphBgu^.

fixed to a pedicle their whole life. These organisms posse««l
tentacnla, or suckers, and are entirely different from thoa
radiating pseiidojwdi a of the RatJiolana. Each tentaculamj
is a tube (containing; a granular finid) which tenninate

PHYSIOLOGY OF THE JNVERTEBRATA. 29

exteraally in a slight knob, the latter being pierced with
a small air-hole. These knob-like projections are used for
seizing the prey. The protoplasm of the captured infusorium
slips slowly through the tentacula,* and is gathered together
in the interior of the Acineta in the form of small globules.
Therefore we have in these tentacula a direct advance on
the flagella of^the monads and the pseudopodia of the forms
already described, inasmuch as the former are not only pre-
hensile organs, but act as suckers.

The Acinetce possess one or more contractile vacuoles, and
in this respect differ from the monads.

The Infusoria cUiata are characterised by having number-
less cilia (Fig. 3, c). These cilia are either localised to the
oral side of the body, or form a zone round it, or are scattered
over its external surface.

In all the Infusoria cilicUa there is an oral region, or mouth,
an oesophagus which leads into the central protoplasmic mass,
and there is an anal region. In this division of the Infusoria
the differentiation into parts has gone so far as to produce a
mouth, an oesophagus, and an anal region ; but the alimentary
canal is broken, for the oesophagus and anal region do not
form one continuous tract. The Infusoria ciliata have con-
tractile vacuoles.

In the Vorticellw (Fig. 3, c) "the oral region presents a
depression, the vestibule from which a permanent oesophageal
canal leads into the soft semi-fluid endosarc, where it ter-
minates abruptly ; and immediately beneath the mouth, in
the vestibule, there is an anal region, which gives exit to the
refuse of digestion, but presents an opening only when faecal
matters are passing out." The Vorticellm possess a contractile
vacuole as well as several gastric or food vacuoles. The latter
are filled with a clear fluid containing the swallowed bodies
(algsB, &c.). The food vacuoles do not remain stationary, but are
conveyed round the inner part of the body, so that the particles
of food contained in these vacuoles undergo digestion.

* See Stein'd Dcr OrganUmus der InfusiontthUre, vol. i, p. 76.

30 PHYSIOLOGY OF THE INVERTEBRATA.

In the ParanujBcia (Fig. 3, c) the oral r^ion or moath is
sitaated near the anterior end of the body, and an anal
aperture is observable in a definite part of the body during
the excretion of the undigested portion of the food. There
is also an oesophagus which passes into the endosarc, or the
semi-fluid portion of the protoplasmic mass. In the endosarc
the particles of food give rise to food vacuoles which undergo
a rotatory movement round the endosarc; this movement
being caused by the contractility of the ectosarc or " cell-
membrane." During the rotation of the food vacuoles digestion
proceeds ; the nutritive portion of the food being absorbed,
while the indigestible residuum is ejected through the im-
provised anus. As already stated, there is no actual anal
aperture ; but there is a very distinctly marked region where
the effete matter is ejected. Therefore, in Paranuecium there
is an oral aperture, an oesophagus, a distinct course for the
food, though there is no intestine, and an anal region, though
no permanent opening. We have in the higher Ciliata a
beginning of a true alimentary canal, although of a simple
form ; and even the tract of the moving food vacuoles has
been described as *' a rudimentary intestinal canal."

In the Paramcecia there are two contractile vacuoles,
situated anteriorly and posteriorly in the ectosarc ; the
physiological function of these cavities will be considered
later ; but they have probably a dual functions-one of these
being that of a renal organ.*

The Porifera or Spongida.

These are animals having many cells, ^id are the lowest in
the zoological scale of the Metazoa. The body cavity (gastro-
vascular space) serves alike for digestion and circulation ;
and it may be remarked that, ** with the exception of certain
parasites, and the extremely modified males of a few species,

* The author's paper in the Proctedingt of Royal Society of Edinlmrf^,
voL 16, p. 133.

PHYSIOLOGY OF THE INVERTEBRATA. 31

all these animals possess a permanent alimentary cavity, lined
by a special layer of cells."

The histological structure of an adult sponge is comparable
in certain details to the Am<jebce and to the Infusoria Jlagel-
IcUaj for adult sponges are partly composed of aggregations
of amoebiform cells and partly of flagellate cells. But in the
embryonic condition a sponge is comparable to an embryo
Hydrozoorij and is consequently unlike any form belonging to
the Protozoa.

The body of these animals has a spongy consistence, and is
usually strengthened by a calcareous, silicious, or fibrous
skeleton.* All over the surface of the body are minute
inhalent apertures, through which the water, bearing food
particles, passes into the gastro-vascular space or body-cavity.
This body-cavity is lined internally with flagellate cells.

Besides the inhalent apertures, there may be one or many
exhalent apertures (oscula). The former are comparable to
the intercellular spaces of plants, and are formed by the

Fig. 4.— Diagram of Section of Spongilla.

(A/fer Huxley.)

A, a = inhalent apertures, d = exhalent aperture ; the arrows indicate
the direction of the ciirrents. B = an endoderm cell.

separation of one cell from another. These apertures or
pores are not constant, for " they may be temporarily or per-
manently closed, and new ones formed in other positions."
The waste materials or excretory matters of each cell are

* The Myxospongicc are devoid of a skeleton.

31 PHYSIOLOGY OF THE INVERTEBRATA.

thrown into the gastro-vascular cavity, and collectively a
pelled through the exhalent aperture or apertures (Fig. 4,J^
as the case may be.

The Porifera are compoaed of three layers: the ectodras''
(of flat epithelial cells), the mesodt-rm, and the endoderm
(of long flagellate cells, Fig. 4, b). Besides a flagellnm, a
single endodermic cell contains one or more contractile
vacuoles and a nucleus. It is possible that these endo-
dermic cells have the power of digesting the food particleB.
and thereby rendering the food into such a state that it ia
readily absorbed. The gastro-vascular cavity, with its in-
ternal lining of endodermic cells, is a rudimentary form of
digestive system.

The CtELESTEKATA."

This class of the Mdazoa is divided into two sub-classes —
the Ilydrozoa and the Adbiozoa. They have a mouth, a
gastro-vascular cavity, but no inhalent or exhalent apertures;
in this point they differ from the Pori/era.

The morphological characteristic of the CalenUrata ia a bo^l
with a constant cavity, which may be considered s digeEtivs '
cavity, but sometimes it is badly differentiated.

In the case of the Hydra, it was formerly stated that if
the anima! were turned inside out, it can digest with what was
previously its external surface ; that is, the ectoderm and
endoderm were interchangeable. But recent Japanese ex-
periments have shown that this organism is more speciaHsed
than was originally supposed to be the case ; and it has beer
shown that when turned inside out, the Hyilrii again tnms
itself back to its normal condition, so that the functions
of its inner and outer surfaces are not interchangeable.
Although in the Hydra the digestive cavity is somewhat badly
differentiated, in many of the Hydrozon the digestive system
in divided into three parts — viz., an oesophageal portion, a

■ofXoi, Impar.

PHYSIOLOGY OF THE INVERTEBRATA. 33

dilated portion, and a narrowed portion, which ultimately
terminates in a csecum.

The Hydrozoa which live in colonies, have an intestinal
tube in common — that is, the tube acts for the whole tribe of
organisms ; while in the Siphonophora (one of the four orders
of the Hydrozoa) V certain members of the colony specially
adapt themselves for the digestive function. For that pur-
pose they come to bear the form of dilatable sacs, and are
in communication interiorly with the digestive cavity common
to all the tribe."

In the Actinozoa the body cavity is hardly more differen-
tiated than that of the Hydrozoa^ for it is still a gastro-vascular
cavity, but is divided by vertical partitions (mesenteries) into
a number of intermesenteric chambers which communicate
with each other at the bottom of the gastro-vascular cavity.
The mouth or oral aperture of the Actinozoa serves both for
the reception of food and the rejection of excreta.

The mesenteries of the Actinozoa are divided into primary
and secondary; the former being longer than the latter.
The secondary mesenteries, which are situated between the
primary, have on their free edges twisted and coiled filaments.
'These mesenteric filaments secrete a fluid which has digestive
properties.

The Actinozoa may be divided into two groups — the
Coralligcna and the Ctcnoplwra. Most of the Coralligcjia
" are fixed temporarily or permanently, and may give rise to
4^j gemmation) tuft-like or arborescent zoanthodemes. The
^reat majority possess a hard skeleton, composed principally
of carbonate of lime." This group of the Ccelcnterata has a
digestive or somatic cavity divided by mesenteries.

The Ctcnophora are free swimming organisms, and never
give rise to colonies. They possess a mouth or oral aperture,
-an oesophagus, and a gastro-vascular canal system, which
^communicates with the exterior by two aboral apertures.

So far we have seen, in this general study of the digestive
function of the Invertebrata^ this function performed by the

3i PHYSIOLOGY OF THE INVERTEBRATA.

whole of the body (Grreganna) ; by auy portion thereof
(fihizopoda) ; by a month, an ccsophagns, and a tolerably
definite portion of the sarcode of the body, without, however
(after the ceaophagus), auy diatiuct tube (In/usorin) ; by
an oral aperture or mouth, and a distinct alimentary canal,
one with a somatic or body cavity {Hydra) ; by an onJ
aperture and a distinct alimentary canal suspended in, dis-
tinct from, but communicating with the somatic caviti
(Acti7na).

The Ecbinodeumata.

In this ciais, physiological differentiation in the digestive
apparatus has taken an important step forward. In the
Holothitriiha there is a mouth and an cesophagus leading"
into an alimentary canal, but it is not differentiated intoa^
stomach and intestine. The alimentary canal is simply u
tube with oral and aboral apertures.

In the Asteriih-a, there is an oral aperture or mouth, and
an oesophagus leading into a wide stomach which has fire
sacs round its periphery. The intestine is short and ter-
minates iu an auus. In each ray tliere are two pyloric
CBSca.

The Ophiuridca have a mouth, gastric sac or etomacb
without C£Bca, and there is no intestine or anus.

In the Echinidm there is a mouth provided with so-called
teeth (masticatoiy apparatus), and the intestine is long and
terminates in an anus. There is no differentiation into a
stomach and appendages.

The Crinoidm* have an oral aperture which leads into a
short, wide oesophagus. There is a large, coiled, and saccu-
lated alimentary canal which terminates in an anus.

In the Cystidea there is an aboral as well as an oral
aperture.

Therefore, to summarise the Echiiwdermata, we may sav

• S«e Prof. Sars'a papers, ilimoirrt pour i

r i la eoHHaitimnet Jtt

PHYSIOLOGY OF THE INVERTEBRATA. 35

that there is a digestive cavity or alimentary canal with an
oral aperture, and usually an anus; also a water-vascular
system, and a true vascular system.

r
I

The Trichoscolices.

This class of the Annuloid Series is divided into the
following orders : — the Tarbellaria^ Eotifera, Trematoda, and
Cestoidea. ,

(i) The Titrhellai^ possess a mouth or oral aperture, and
an alimentary canal,*^ but there is no anus, except in
the higher forms. The mouth is either at the anterior or
posterior end of the body, or sometimes it is situated in the
middle. The alimentary canal is lined by an endoderm, and
between the endoderm and ectoderm there is a mesoderm
consisting of muscular and connective tissues. The ali-
mentary canal of the Turbellaria is either straight or
branched.

(2) The Rotifera, or the ''wheel-animalcules," have a
funnel-shaped oral aperture or mouth situated on one side, or
in the middle, of the trochal disc. The mouth of these
organisms is a great advance on all the forms previously
described. Its internal lining, as well as the trochal disc, are
abundantly provided with cilia, and at the posterior end of
this cavity there is a muscular pharynx (mastax) with an
armature consisting of four distinct pieces. The muscular
pharynx and its appendages are used in the mastication of
the prey seized by the ciliated trochal disc. The pharynx
leads into a short oesophagus (also provided with cilia) which
passes into a digestive cavity or stomach. The stomach then
passes into a short intestine. Opening into the anterior part
of the stomach are two large glandular tubes having a
pancreatic function. The intestine, which usually opens
externally by a cloaca, has numerous lateral diverticula

* With the exception of Convoluia, for in this form an alimentary canal
can hardly be said to exist.

PHYSIOLOGy OF THE INVERTEBRATA.

(cseca). However, i

ief.H

cli

1 some of the RoUftni, as, for example,
Notommnta, the alimentary canal is blind or closed at ihe
posterior end; and the males of some forms are entirelj
devoid of any digestive apparatus. The whole of their brief .|
life is devoted to reprodnction.

(3) The Tri-maloda are all parasitic animals, having one OT^
more suckers upon the ventral side of the body, and behind
the raouth. The mouth leads into a muscular phar}Tix, which
opens into a more or less elongated cesophagus, and terminateB
in a branched intestine. There is no anus.

In AmpMptychca and Ampkilwn the alimentary canal in
entirely absent ; and on the authority of Professor 1'. J. VaH
Beneden* it "becomes aborted in the adult ZHsiuma JilicolU."

(4) The Cestuiiien, or tape-worms, are examples of reverswms
to a very low type of digestion, although in other respects
these animals are comparatively high in the zoological scal^P
They live by the imbibition of partly digested food of t
animals whose intestines they infest.

In the words of Professor Huxley, f " it is obvious that till
CestovJim are very closely related to the Trnnafoda. In fao
inasmuch as some of the latter are anenterous, and some q
the former are not segmented, it is impossible to draw a
absolute line of demarcation that the Cistoidm are eitl
Trematodea which have undergone retrogressive metamoi
phosis, and have lost the alimentary canal which they
primitively possessed ; or that they are modifications of a
Trematode type, in which the endoderm has got no farther
than the spongy condition which it exhibits in CoiivoliUa
among the Tiuidlarin, and in which no oral aperture has
been formed ; or, lastly, it is possible that the central cavity
of the body of the embrj-o Tania simply represents a blasto-
ccele. If the CextoiiUn are essentially Trematodes, modified
by the loss of their digestive organs, some trace of the diges-
tive apparatus ought to be discoverable in the embryo tape-

t The Am

•lofthe l,n-

PHYSIOLOGY OF THE INVERTEBRATA, 37

worm. Nevertheless, nothing of the kind is discernible,
unless the cavity of the saccular embryo is an enteroccele.
And if this cavity is a blastocoele, and not an enteroccele, it
may become a question whether the tape-worms are anything
but gigantic morulas, so to speak, which have never passed
through the gastrula stage."

The Annelida.

The second class of the Annuloid Series contains the follow-
ing orders: the Myzostomata, Gephyrea, Hiitidinea, Oligoihata,
and Polychccta,

(i) The Myzostomuta are parasitic unsegmented worms.
There is a mouth, through which a proboscis is protruded.
The mouth passes into a straight alimentary canal terminating
in a cloaca. The alimentary canal has numerous lateral
C80ca*

(2) The Gephyrea are marine unsegmented worms * with a
more or less cylindrical body. The oral aperture or mouth is
either terminal, or has a ventral aspect. In some forms the
mouth is provided with a proboscis, or is surrounded by
tentacula ; and it passes into a pharynx, which opens into
either a straight or coiled intestine. The anus is always
situated dorsally, and in Plwrmiis it is close to the mouth.

(3) The Himidinea, — The leeches are more or less segmented
worms, provided with a sucker at the anterior end of the
body. Most species have a second unperf orated sucker
situated posteriorly, and there are a few of the ffinuliriea
with lateral suckers. The mouth of Hirudo medicinalis is
armed with chitinous teeth, and opens into the pharynx,
which is provided with glands. The sucking action of the
animal is produced by the contraction of the muscles which
suspend the pharynx. The pharynx passes into a slender
oesophagus, which leads into a very long stomach ; and from

* In the larvae of ChiHiftra (belonging to the Gephyrea) there are traces
of segmentation.

PHYSIOLOGY OF THE ISVERTEBRATA.

the stomncb a narrow intestine passes to the hdhs, which
sitnated dorealiy. The stomach is prodoced into b nnmber
lateral casca, or diverticula.

The alimentaiy canal of M.<f\a(tM(Un is " a simple tnbo
bent several times npon itself."

(4) The Oli(io<:luitn — The earthworm and certain fresh-
water worms belong to tliis order. The body is elongsted,
roonded, and segmented. The month is a email apertnre^
leading into a baccal cavity, and into which tme salivary
glands open. This cavity or sac passes into a pharynx,
which is continued into a straight cesophagns bearing three
pairs of lateral diverticula (the esophageal glands), Abont
the region of the fifteenth segment the rcsophagiis opens into
a dilated portion of the alimentary canal called the crop
proventriculns. The crop leads into the gizzard or stomach,
which is provided with strong muscles. The gizzard is
succeeded by the intestine, which tenninates in an anna.

(5) The Pnl ifchalii .—Iti this order the alimentary canal
■' rarely presents any marked distinction into stomach and
intestine." The mouth opens into a moscniar pharynx, which
is capable of being protruded as a proboscis : and in Poiyiuit
and other genera the proboscis is provide<I with papillee and
chitinous teeth. The pharynx leads into a straight tubniar
intestine. In certain genera of the Po!i/ch<rta there are long
aeca which form lateral appendages to the intestine, Tha
function of these cffca is of a pancreatic nature ; while the
pair of glandular organs appended to the base of the proboscis
in Xfi-ein are true salivary glands. The anus, in many
Annelids, ut not terminal, bot is situated in the centre of a
raised papilla on the dorsal side of the animal.

TnE Nematoscouces,

ThiB class of the Arthrozoic Series is divided into three
orders : the Scmaloidca, Xanator/11/nehn, and AcarUhO'
rephnlft.

PHYSIOLOGY OF THE INVERTEBRATA. 39

(i) The Nematoidea. — ^The " thread- worms " possess elon-
gated, rounded bodies. They are not segmented organisms.
The anterior end is sometimes furnished either with hooks
and spines within the oral cavity, or with papillae around
the mouth. The mouth leads into a muscular pharynx, lined
with chitin, which then proceeds into a narrow oesophagus —
the latter passing into a long intestine which terminates in
an anus * situated ventrally. There is no dilatation of the
alimentary canal to form a stomach.

(2) The Ne?natorhy7icha, — This order contains the follow-
ing genera among others: CJicetonotus, Chxetura^ Dasyditis^
and Turbanella. These organisms are allied to the Itoti/era,
" but they differ from them in the absence of a mast>ax, and
in the disposition of the cilia, which are restricted to the
ventral surface of the body." Professor Huxley says : " On
the whole, however, I think that, notwithstanding the cilia
of the Gastrotricha,^ the closest affinities of the Nemato-
rhyncha are with the Neinatoidea, and I therefore place them
among the Nematoscolicesy

(3) The Acanfliocepfiala, — The animals of this order, and
particularly Echinorhynchus, are parasitic, for in the sexless
condition they infest the Invertehrata, while in the sexual
state they are found infesting the Vcrtehrata,

There is neither a mouth nor an alimentary canal in
Echinorhynchus. This is another example of reversion to a
low type of digestion. No doubt nutrition is performed by
the absorption or imbibition of fluid nutriment through the
external walls of the body.

The CHiETOGNATHA.

This class of the Arthrozoic Series is represented by only
one genus — the Sagitta,

* Mermis has no anas.

t One of the two groups into which the Nematorhjncha have boon
divided.

40 PHYSIOLOGY OF THE IXVERTEBRATA.

The Biigitln have rounded, elongated, unsegment^d bodiea.
There is a head, at the anterior end of which is the month.
On each side of the mouth is situated several strong, curved.
chitiuons spines, which are said to act as jaws. The mouth
paSB^es into a straight alimentnry canal which terminates in
an anus situated ventrallr and anteriorly to the caudal
region. The cauda! region ends in a fan-like " fin " of
delicate seta?. No salivary glands or pancreatic follicles
appear to exist in Sti;ilttu. The eudoderra of the alimentary
canal possibly performs the function of a digestive gland.

The genus Sa-jittn includes several species of vermiform
animals which live near the surface of " the ocean in all parts
of the world,''

The Arthropoda.

This is the third and last claaa of the Arthrozoic Series, aj
is divided into the Onyckojjhura, Myrwpoih, [jmcHn, An
nitia, and Crustacea. These divisions are again subdivide!
(see the table given in Chapter I.).

(1) The Prototmclinda. — The only genus is PcripatuA, i
due to the important investigations of Professor H. N, Mosel^
F.R.S,' l\riputns has been referred to the Ar/lnvpodn. All
the species of this genus have a well-developed tracheal
Ryatem. There is a distinct head, with several tentaculaj—
the mouth is situated ventrally beneath a large projectin
BDctorial lip, and is provided with a pair of mandibles i
jaws. There is also a short oral papilla attached to the hei

on each side of the mouth. The month or oral apertoi
leads into a muscular pharynx; then follows a short (
phagus, which passes into a wide and long stomach, Th^
stomach leads into a short intestine terminating in an anus
situated at the posterior end of the body. There appears to
be no salivary glands or pancreatic follicles.

(2) The Ch ilopot/fi. — On referring to the classification giv<
in the first chapter of the book it will be obsei-ved that tht^

• ri<iloii',<!.!cal T,n,.farth«> Of lit Iloynl .Six-.Vl

PHYSIOLOGY OF THE INVERTEBRATA.

Myriaiioda have been divided into four orders ; and as two
of these contain only fossil genera they do not come under
onr notice.

In the ChUopoda (centipedes) the body is usually long and
segmented ; each segment carrying a pair of many-jointed
limbs. The first and second pairs of limbs are masticatory,
while the fourth pair are known as poison-claws. The head
is flattened and the mouth is constructed for biting. The
mouth leads into a long oesophagus, followed by an alimentary
canal which is usually straight, some-
what like the intestinal tube of cater-
pillars. There is a pair of salivary
glands (Fig. 5) which pour their
contents into the mouth.

(3) The Diplojyoda or ChUognatha
(millipedes) have rounded bodies,
which are segmented. There are two
pairs of limbs on each segment ex-
cept the anterior one. The first pair
of maxillae is represented by a four-
lobed buccal plate or under-lip. The
digestive system (like the ChUopoda^
is a simple tube with salivar}^
glands.

(4) The Thyscmura represent the
first order of the Insecta, and are
said to resemble the young Blatta\

The mouth is provided with mandibles and maxillae. The
alimentary canal is divided into a buccal, a median, and a
terminal portion. There are well-marked salivary glands,
and according to Sir John Lubbock Zcpisma is provided with
foar Malpighian tubules; but certain genera of the TJiysanunf
{e.g., Japyx, Camj^odea) are devoid of these excretory organs.

(5) The Orihoptera comprise the cockroaches, crickets,
dn^on-flies, may-flies, grasshoppers, &c. The body is
divided (like all the Insecta) into head, thorax, and abdomen.

Fig. 5.
Alimentary Canal 01

THE CHII.OPODA.

m = mouth. s = salivary
glands. / = intestine.

42 PHYSIOLOCV OF THE JNVERTEBRATA.

In hlatta the moutii leads into an ceaophagus which ^
ally dilates info a large croii (inghivies). The crop passes
into a small gizzard or proven trie ulna, and then inio a
wide tubular stomach, the so-called chylific ventriculus, which
leads into the small intestine or ileum, followed by the large
intestine or colon, and the rectum; the latter terminating
in the anus, which is situated between the podical plates.
To the anterior end of the stomach are attached seven or
eight pyloric ca3Ca ; and from the posterior end of the
stomach are several Malpighian or urinary tubules (from i
twenty to thirty). The mouth of Blntta. which has a ventrAl-M
aspect, is provided with a pair of wellnieveloped salivaryj
glands and receptacles. Each gland is divided into twOj
lobes composed of numerous acini. The proventriculus oonJ
tains six principal teeth, and between each pair of teeth arofl
five smaller teeth. These teeth or ridges are produced byj
the folding of the chitinous lining of the crop, which passes!
into the proventriculus. The ileum is separated from thai
large intestine or colon by a circular valve ; and the walls c
the rectum are raised into six ridges projecting into tfaoV
interior. Thi/se ridges are the rectal glands.

The mouth of Tllutla is situated between "the labrum in
frant, the mandibles and ma-rillse at the sides, and the
iabium, with the large lingna, or hypopharynx, behind," In.i
all the Orthoplrru the month is constructed on the aboTAl
plan, but the I'kysopoila* "'present a modification which Vkm
transitional to the Ilemipteran mouth. There is a probosasl
directed backwards, and formed by the union of the labrum. 4
with the labium, which last is provided with palps, though J
they are sometimes very small."

The labrum, labium, mandibles, and maxilla of the Insccta\
are, in the main, subservient to the functions of taking in c
crushing food. In the carnivorous LiMluln depivsm, I
alimentar)' canal is fibort and there is neither cropuorg
but the so-called chylific ventriculus is pi'eeent.
• A sub-order lo which Tkripf belongs.

PHYSIOLOGY OF THE INVERTEBRATA. 43

(6) The Palceodictyoptera are found only in the fossil
condition.

(7) The Khynclwta form an order of the Insecta having a
suctorial month in the form of a jointed rostrum. The order
includes the bugs (land and water), Aphides, Cicada, &c.
They all suck the juice of plants or the blood of animals.
According to Huxley, " there is a usually sharp and pointed
labrum, while the mandibles and maxillae are mere tubercles,
surmounted by long chitinous pointed styles, of which there
are four. The labium is usually represented by a median,
jointed, fleshy, elongated body, the anterior face of which
presents a longitudinal groove in which the mandibles and
maxillae are enclosed. Neither the maxillae nor the labium
are provided with palps." With such an arrangement of
parts one can readily understand the suctorial power of the
Rhynchota ; for it may be mentioned that the Cicada) perforate
the bark of the trees on which they live, and exhaust their sap.
The structure of these mandibles, maxilte, &c., are also well
adapted for piercing the skin and sucking the blood of animals.

The Bhynchota have a crop, either forming an appendage
to the oesophagus, or forming an anterior dilatation to the
so-called chylific ventriculus, which in the Cicadcc is of great
length.

(8) The Diptcra, — This order includes the fleas, flies, gnats,
crane-flies, &c. The mouth is suctorial, and is therefore
constructed on a somewhat similar plan to the last-mentioned
order; but the maxillae have palps. In the house-fly " the
labrum, mandibles, and maxillae coalesce at their origins to
constitute the base of the probocsis, which is mainly formed
bv the confluent second maxillae."

The mouth leads into a narrow oesophagus which passes into
a crop situated upon the stomach. This is followed by a small
intestine which is convoluted, and then a short rectum provided
with two lateral glandular bodies — the so-called rectal glands.

(9) The Zepidoptera. — In this order ** the labrum and the
mandibles abort, and the labium is represented only by a

= proboscis ImaJtilliB). /• - sali-

«; = mouth.

0 = fiemphagus. .1 = nlimfy

vary glondj. c = (Esophngus.

glands *

= spining gland*. -■ ^ chylifici

rf = crop. ( = ehyUfic vemri-

stonacb.

,1 = Malpighian tubulo*.

cutus, / = sm>lt inlesline.

r - ialesti

i = rwrium. » = Mslpighian

(ubules. g = large itntslirf.

]ong cesophagua (Fig. 6).
Bmall, bnt ia sacculated.

The " chyli6c " ventriculus is very I
The small intestine is short and j
passes into the wide rectum. In the larvse of the Lcpidoptfi-a
the cesophagus is short and wide (Fig. 7), and posses to a long (
chylific stomach. The intestine is short, and Itfrminates in ,
the rectum. Both in the larval and perfect state there are .
well-developed salivary glands and Malpighian tubnles. The j

PHYSIOLOGY OF THE INVERTEBRATA, 45

former secrete the silk-like material in which the larvae invest
themselves on turning into the pupal state.

(lo) The Neuroptera, — In this order the mouth parts are
masticatory, although sometimes also suctorial. The alimen-
tary canal is somewhat similar to that of the Lepidoptcra.
There are eight free Malpighian tubules.

(ii) The Hymenoptera is the order to which bees, wasps,
and ants belong. The mouth parts are for biting (ants), and
licking (bees). The labial palps are long and slender ; " there
are two large paraglosssB, and between them a median, annu-
lated, setose, cylindrical organ proceeds, which either repre-
sents the lingua, or is an independent prolongation of the
ligula. Fanctionally this organ is a tongiie, and enables the
bee to lap up the honey an ivhich it feeds. The mandibles and
maxilhe are employed as cutting and modelling instruments,
but appear to have little or nothing to do with mastication,
properly so called."

In the bee the mouth opens into a slender oesophagus,
which extends the whole length of the thorax, and at whose
posterior end it dilates into the large honey-bag (Fig. 8).
Before any honey passes into the stomach the so-called
valve (i)* must be withdrawn by a special action. The
" valve " then returns to its usual position, and thereby
converts the crop (6) into a special receptacle for collecting
nectar until the bee reaches its hive. In the crop the nectar or
honey undergoes a change which prevents it (to a certain extent)
undergoing acetic fermentation. When the bee reaches its
hive the honey is regurgitated into waxen cells. The stomach
or chylific ventriculus (c) is very long and leads into a short
intestine (e), and then into a wide, distensible rectum {g).

The poison of the Hymenoptera is a fluid containing formic
€U3id (H,CO,), which is secreted by a gland and retained in a
receptacle connected with the sting. The sting is nothing
more than a modified ovipositor.f In the larval bee the

* Vide next chapter.

t See Lacaze-Dathiers'd ScchercJief sur Varmurc gi.iUaU femeUc des
jMecte$.

PHYSIOLOGY OF THE INVERTEBRATA.

alimeutaiy eana! consista only of a short but wide tesophagu f .
a Iiirga chylific ventricnlus, and from four to six; Malpigbiau
tnbules. There is no Lntestiti-
or anus.

(12) The fu/eojj^era (beetles)
have masticatory mouths, and
the alimentary canal is framed
on the same type as the Oj-lfw-
pta-n ; but in the larval con-
dition of the Coleoptcra the
gizzard is entirely absent. In
most herbivorous Cideoptera the
chylific ventriculusof the larval
form is much shorter than in the
perfect insect or imago, and has
appended at both ends a nnm-
ber of Ciecal tubes. But the
latter disappear during the
metam oqiho sis . *

"The alimentary caual is
most simple in the larvae of
insects in which, as in worms,
it usually extends, without con-
volutions, from one end of the body to the other ; iu a few larva*,
as that of the bee, it has only the anterior opening or mouth,
and the opposite or anal orifice is not developed until the pupal
state. In all matiur insects the alimentary canal presents
the two distinct apertures : it is simplest iu the carnivorous
larviform ilyriapodsf ; present more numeraus and distinct
constrictious and divisions in the HexaiK>ds, and increases in
complexity and length as the food requires most prei>aration
in order to effect its conversion into the animal nutrient
flnid."

FlO. 8 — .\LIMEHTARy Ca.N.'

Bee (Hymt«u/>lcra).
— ccsophagus. b — honey-bag.
r = slomach r = ileum,
pighiaii lubules. g =

■' = valvular opening of
i = sallvur glands.

" Wilh the exception of the genae Hiil
tabee ore to be found in the perfect iUBect.

. t ^'c^ true iosecte.

A of these oeeal I

PHYSIOLOGY OF THE INVERTEBRATA. 47

(13) The Pentastomida is the first order of the Arachnida
— one of the five divisions of the Arthropoda. The only genus
is the parasitic Pcntastomum. In the sexual state, the vermi-
form Pentastomum is found in the nasal cavities of the Car-
nivora, while in the sexless condition it infests the liver and
lungs of the Hei^bivora and EepHlia, There are ambulatory
limbs, the only appendages are four hooks, two on each side
of the mouth or oral aperture. The alimentary canal is very
simple, at the anterior end of which is a slender oesophagus
and at the posterior end the anus.

(14) The Ardisca or Tardigrada, — Like the previously
mentioned order, the Ardisca are low-organised members of
the Arachnida; yet there is an advance not only in the
alimentary canal, which is more in keeping with the highly
developed digestive system of the Iiiscda, but in the presence
of rudimentary legs.

The genus Macrobiotus is found in moss and in sand. The
mouth (Fig. 9) is suctorial, which is situated at the end of a
rostrum, and is provided with two styles. It leads into a
short oesophagus which passes into a muscular pharynx. The
ducts from two well-defined salivary glands discharge their
contents into the posterior part of the oral cavity. The
pharynx leads into a wide alimentary canal which gradually
narrows to the anus.

(15) The Pycnogonida, — ^The alimentary canal of these
marine animals is very different from that of the two
previously mentioned orders. The oesophagus leads into a
more or less circular stomach which sends off very long
diverticula or casca into the legs. There is a short rectum
terminating in an anus.

(16) The AcariTia, — This order includes the mites and
ticks. The alimentary canal is short and straight; but the
stomach is produced into several caecal appendages. Salivary
glands are sometimes present. In Ixodes the salivary glands
are situated on the sides of the anterior part of the body,
and pour the secretion into the mouth at the base of the

PHYSIOLOGY OF THE INVERTEHRATA.

labluoi. Milpigliiao tubules are al:K» sometimes preaeott J
The alimentary canal terminates in an anus which is eitliez^
situated at th'a postfirior end of th= b33y or near the middle J
of the abdomen.

dial cavily. b = salivary dud. i- = »[ivaTy gland.
= (EsophaguG. 1/ = pharynx, t = alimentary Imcl or ialcsUoe.
= aoiu. £ = cnicnMcopical stiuclure of !>alivaty gland.

(17) The Amni'ina are A racluUif .i with sub-chelate ■
clielicerec, and posBesa a poison frland which opens in the
terminal joint. They have from four to six spinning glands |
situated at the posterior end of the abdomen.

" The spidera are remarkable for the minuteness of the 1
pharynx and {esophageal canal. Sa^-igny believed that io j

PHYSIOLOGY OF THE INVERTEBRATA. 49

6ome Bpeciea there existed three pharyngeal apertures,
through which the juices expressed from the captured insect
by the action of the raaxiUary plates were filtered, as it
were, into the narrow resophagus. In Mijiji'Ji-, however,
there ia only one aper-
ture." The cesophagus
leads into a stomach pro-
dnceil into several lateral
appendagE-s, which some-
times extend into thr
limbs. The stomach of
Ttgemiria ilomestim, and
other species, ia capable
of great distension, and
passes directly into thf
intestine, which dilates
into a rectum and then
terminates in an unus.
Into the intestine open
several so-called biliary
docts. The latter are
thrown off fi-om a large
organ (Fig. lo) situated
on either aide of the in-
testine, but which is
greatly concealed by large
masses of adipose tissue
occupying the sides of
the abdomen. This organ
has not the function of a
liver, for its secretion is
of a pancreatic nature.

In front of the rectum open two long slender tubes which
often branch; these are the Malpighian tubules. Salivary
glands are also present. Spiders are carnivorous animals,
.and the females are sometimes addicted to cannibalism.

= salivary glands. i = si
= intestine. d — so

= Malpighian mbulc5. /= ii

JO PHYSIOLOGY OF THE INVERTESRATA.

They devour their " Romeoa," if the latter are in the least
obnoxious.

(i8) The ArthroQostm. — In this order, to which the
scorpion belongs, " the mouth is situated between the labram
in front, the bases of the pedipalpi and those of the first
two pairs of ambulatory limbs at the aides and behind." It
is a very small aperture and leads into a pharyngeal sac
with chitinous walls. The pharynx passes into a narrow
fesophagus, and into this two ducts from large salivary
gianda discharge the secretion. The intestine forms prac-
tically a straight tube which terminates in an anns. As in
the Affuii-inn, numerous so-called biliary ducts open into
the intestine. The pancreas or digestive gland {the so-called
liver) is extremely well developed in Sivrpio, occupying all
the spaces between " the other organs in the enlarged part
of the body, and even extending for some distance into the
narrow posterior soniites."

All the Arfhrai/astrn have a distinctly segmented abdomen,

(icjj The EnrifpUrida form an order of extinct Crmtaeea,
consequently it does not come ander our description,

Before alluding to the other orders, it may be stated tbab'
the Cnititnci-a have been subdivided into the Gnaikopoda,
Ptictostrnra, and Malaeustmcu. The Gnathopoda have been
further divided into the Merostomata, Branrhiopoda, andt'
Lophyropoda, These three divisions comprise seven orders^
commencing with the Eurypterida and ending with the
Copqioda.

(3o) The Jiiphumtra. — Of this order the only existing
representative is the genus Liniulm (the king crabs). The
mouth of LimuJus is provided with a small labmm,
rudimentai-y metastoma, and six pairs of lateral appendages
which terminate in chelrc. It is situated in " the centre of the
sternal surface of the anterior division of the body ; the anus
opens on the same surface, at the junction between the
middle division and the telson." The cesophagus is continued
from the mouth forwards and upwards, and then dilates into

PHYSIOLOGY OF THE INVERTEBRATA. 51

a stomach, the posterior end of which gradually lessens in
diameter and finally passes into the intestine. The stomach
is lined internally with a dense rugged membrane. " The
distinction between the stomach and intestine is effected, as
Van der Hoeven has shown, by a conical valvular pylorus,
which projects into the commencement of the intestine.
The hepatic mass, composed of contorted slender caeca,
which with the generative glands fills the greater part of the
cephalo-thoracic cavity and also extends into the abdomen,
pours its secretion into the commencement of the intestine
by two ducts on each side."

The so-called liver or hepatic mass is a very large organ in
the Crustacea; but its secretion answers chemically to that
of a pancreas — in fact, this organ is nothing more than a
pancreas or digestive gland. In Liimihts there is a short
rectum opening into a kind of cloaca.

(21) The Trilobita form an extinct order of Crustacea.

(22) The Phyllopoda. — In this order the alimentary canal,
as represented by Apus, is very simple. The mouth is
situated anteriorly on the ventral side of the body, and leads
into a vertical oesophagus which finally bends back into a
small stomach. The stomach passes into a straight intestine,
the latter terminating in an anus situated below the terminal
segment. The pancreas (the so-called liver) is situated in
the head, and consists of many caecal tubules branching from
the stomach. There are two salivary glands whose secretion
is poured directly into the stomach, these glands being
situated above that organ.

Dr. G. 0. Sars (the distinguished Professor of Natural
History in the University of Christiania) has very fully
described the digestive system of Cyehstheria hislopi* a new
generic type of bivalve FhyUopoda,

In Cydcstheria hislojn the mouth, " located between the
masticatoiy parts of the mandibles, is generally covered

• See CkrUtiania Vidtntkahs — Selskabs FurhamUingtfr^ 1887, No. i, pp. 28
And 4a

SI PHYSIOLOGY OF THE INVERTEBRATA.

below by the labriiin. It leads to a short and narrow (eso-
phagus, which ascends almost perpendicularly to the intesiine,
in the inner cavity of which it forms a distinct mainiiiillflr

projection. The walls of the ccsophagua are highly niuscnlar,
and its contours wavy from the strong circular muscles.
Besides numerous fine muscular bundles forming a coatinua-

PHYSIOLOGY OF THE INVERTEBRATA. 53

tion of the transverse muscles of the labrum mentioned above
ore found adjoining its anterior wall. The intestine (Fig. 1 1),
as in the other forms of the Phyllapodu, constitutes a rather
wide and uniform tube, running along the axis of the body,
but very slightly dilated in its anterior part, that curves more
or less abruptly downward, according to the attitude of the
head. The foremost part of the intestine, extended within
the preoral part of the head, expands at the end on either
side to a very short and broadly rounded caBCum, quite simple,
without any trace of folds or lobes, and communicating with
the intestinal cavity by a wide opening."

In Cydcstheria hislopi there is no pancreas or so-called liver
filling up a great part of the anterior end of the body. The
total want of this organ is a striking feature, as it is present
in all other known bivalve Phyllopoda. In this respect
Cj/cIestJuria occupies a lower rank than the Branchipodid(v^ in
which the digestive tubules are found to be at least more
or lees distinctly folded or lobed. " The structure of the in-
testinal tube (of Cyclestheria) is that usually met with, its
walls being rather thin and surrounded by numerous circular
muscles. At the end of the trunk the intestine terminates
with a well-defined rectum, traversing the caudal part close
to its ventral side, and opening at its extremity between the
two caudal claws. The latter part of the intestinal canal is
very strongly muscular and generally devoid of contents,
except when at intervals the excrements are expelled from
the anal orifice."

According to Dr. Sars, the food of Cyclestheria consists of
vegetable matter (e.g., -^ly^i Desinidicc^ Diatomew, and CoH"
fcrvcc). The contents of the alimentary canal are of a yellow
colour in its anterior part, becoming gradually darker poste-
riorly, and the excreta are invariably of a dark-brown colour.
''The food is conveyed to the mouth by the rhythmical move-
ments of the legs, which give rise to a whirling motion,
whereby any small particles suspended in the surrounding
water are sucked between the valves and brought into the

54 PHYSIOLOGY OF THE INVERTEBEATA.

uaiTow- conduit running along the ventral sidi- of the trunk
between the bases of the legs. The particles are here suc-
cessively tlirown forward, chiefly by the aid of the coxal lobes
of the legs, till they reach the oral region, where they VK j
partly pushed into the month by the aid of tJie uiaxiUw, |
partly caught by the protracted labrum, and by the retraction I
of that part brought immediately within the reach of tbe I
niandiblea. When the animal is feeding, the latter organs I
are found to move almost incessantly, their molar gnrfaces I
being at abort intervals closely applied against each other J
and their bodies revolved, so aa to cross and tritnrat* the \
particles. At the same time the labrum ia lowered at short I
reprises and then thrown back against the mandibles, tha» j
continually conveying new particles within the reach of the I
mandibles. The swallowing movements of the ossophagos I
when transferring prepared food to the intestine, are very I
distinctly observed through the shell, whereas the tnteatiue I
itself doea not seem to perform any perceptible perUtaltio f
movements."

(■23) The C/"<h«'rn'.~lii this order, to which DapkniaM
belongs, the alimentary canal doea not differ very mnch from 1
that of the Phi/llopor/n. Many of the Australian CIndocera j
have been recently investigated by Dr. G. O. Sara." In |
Latmtopsis amfmlis, Siiiioi-rphtthis australirims, Maerolkn
spinosa, and Ih/ofryptva loiir/'u'emis, the alimentary canal is
simple tube traversing the body, whereas in Duiihftvdia cnnstt I
and Alijtia unhcri the alimentary canal forms in the middle f
of the body a double loop before passing to a dilatation in |
front of the muscular rectum. A large dilatation or sac is
also present in Jli/orri/plns lonffireinw, but there are no loops.
A sac of aiualler size is observable in all the above-mentioned j
forms, and is sitnated in each case in front of the rectum. 1
The intestine or alimentary canal of Macrolhrli- xpinosa is I
dilated in its anterior part; and the digestive tube ot Simo- j
rephtih'S itivi/raliriiiii/i is provided with two large incurved I

• VbrUtiaiin Vi.lrn.h'b^—'-M.oU Fin-handiim^r. 1888, No. 7.

PHYSIOLOGY OF THE JNVERTEBRATA. 55

csBcal appendages. The ducts from these appendages open
into the anterior end of the alimentary canal. These caacal
appendages are not present in any of the other Australian
forms mentioned above. The anus in these forms is situated
behind or above the caudal claws. For a further description
of the Cladoc^^ra the reader is referred to an excellent paper,
entitled "Oversigt af Norges Crustaceer nied forelobige
Bemaerkninger over de nye eller mindre bekjendte Arter/'
by Dr. Sars.*

(24) The Ostracoda. — ** The alimentary canal of the Ostra-
coda is provided anteriorly with an apparatus of hard parts
resembling in many respects the gastric armature of the
Isapoda^ aad gives rise to two hepatic ca^ca."

In Cypri7wtus dentato-margiimtus, the alimentary canal
consists of three principal parts: a narrow, muscular oeso-
phagus ascending almost perpendicularly from the oral aper-
tore, the intestine proper, and a very short rectum opening
just in front of the caudal rami. " The intestine proper
exhibits two considerable dilatations, the anterior, lying in
the foremost part of the body, almost globular in form, the
posterior somewhat larger and more oval, both defined by a
well-marked median instriction, just above the great adductor
muscle of the shell. From the anterior division of the in-
testine two slender csBcal appendages are given off, each
being received between the lamellae of the corresponding
valve and nuining diagonally backwards to the infero-posteal
comer." These csecal appendages, of a green colour, are,
d priori, pancreatic in function. The kidney or shell-gland
in the Ostracoda is very small.f

(25) The Copepoda. — The mouth leads into a straight and
simple alinientary canal. In Cyclops, which is probably the
most common form of the Copepoda, there is no distinct

* CkrMania Videnskahs — SeUkabs ForhamUivyer, 1890, No. i, pp. 30-53.

t For a detailed description of many genera and species of the Ostracoda^
see a paper by Dr. G. 8. Brady, F.R.S., in the Transactions of the Hoyul
Society of Edinhurgh^ vol. 3$, p. 489 ; and one by Dr. Sars in Christ, Vidensk
M$k. ForhandL, 1889, No. 8, pp. 5-58 ; and 1890, No. i, pp. 54-76.

PHYSIOLOGV OF THE JM'ERTEBRATA.

a of

a of I
and

digestive gland or pancreas. In Diaptoinns orimtnlig, first
deacribed by E>r. Bratly,* the anterior portion of the intostiod
is dilated ; but, speaking generally, the digestive eystem of
the Copi-poihi is a simple tube devoid of appendages,

(26) The Rlnzofi'phtilii form the first order of the Perta
dram ; and they are parasitic organisms. The body is s
like, and, unlike the majority of the Criisfocrii, is devoid of
limbs and segmentation. The mouth is funnel-shaped, and
is surrounded by chitin. There is no alimentary canal. Iii^
fact, we have in this order one of the reversions to a 1
low type of digestion,

(27) The Cirrijjcdia contain the b&macles (Lfjins) and 1
acorn -shells {Belnnvs).

The mouth in Lcpas faces the posterior end of the body and
leads into a short (esophagus, which dilates into a stoniacii»a
The ptomach passes into the intestine, which is bent upon tj
former organ. The intestine tapers gradually to the ann
which is situated at the base of the candal appendage.
stomach is covered by small branched glands which are pai
creatic in function.

The food of the barnacles (consisting of small mai
animals) is brought to the mouth by the currents product
by the cirri. In the words of I'rof. Huxley. " a barnacle m^
be said to be a crustacean fixed by its head, and kicking tbj
food into its mouth with its lege."

'J'he majority of the C'irnjx'din are hermaphrodites, but in thai
so-called supplemental or complemental male of Scalpellwm rul-
(/«i'<- (one of the /itihiiiiifir: or sessile Ptr/yxy/in) there is neither
mouth nor alimentary canal. In Sra/jx/hivi omatutn the com-
plemental males have no mouth ; but in S-iilpclhnn rosirntam^
these males have n well-developed alimentar}' canal. t ■

(38) The Amphipo<la have a laterally compressed body with!
brancbife attached to the thoracic limbs. The mouth opens
into a straight and simple alimentary canal. The ducts of

* Iahk, Sue. Jfirrx. Zoai., voL I9, ]

+ S.-e Darwin'i Monigniph <^lki Cirriprdia.

PHYSIOLOGY OF THE INVERTEBRATA. 57

the pancreas (the Bo-called liver) discharge the secretion into
the anterior part of the aliroentary canal. There are in some
of the Amphipoda Malpighian tabnles which open into the
posterior part of the alimentary canal.*

(29) The Isopoda. — In this order, to which the wood-louse
belongs, the body is usually broad, depressed, or vertically
flattened, and more or less arched. The alimentary canal is
similar to that of the Amphipoda.

Fig. 12 represents the digestive
system of Oniseas (the wood-
louse). It forms a straight tube,
the masticatory portion being
strongly anned . T wo d ucts,
leading from a pair of cellular
pancreatic follicles on each side
of the alimentary canal, poar the
digestive fluid into the anterior
portion of the canal. The num-
ber of these follicles is variable
in other genera of the Isopoda,
but in OnifKus there are always °' uncscus.

four, two on each side of the "- ^^ticatoty portion,

in- * — pancrealic follicles.

alimentary canal. oometimes , = imesiine. d = anus,
there are one or two tubnles which

open into the posterior part of the intestine. The function
ot these appendages is of the same nature as the Malpighian
tnbules of the Insecta.

(30) The Stmnapoda are elongated. Crustacea having a
short, cephalo-thoracic shield which does not entirely cover
all the thoracic segments. In the genus Squilla there are
five pairs of mazillipeds, and three pairs of backwardly
tnmed biramons thoracic feet. The alimentary canal, some-
what dilated in its anterior part, is a long cylindrical tube,

1 Bpecles ot tho Amphtpala have been described by Sars ii
» I'lWcfxit. Se'ik. ForhaniU., 188a, So. 16, pp. 75-115.

PHYSiOLOGY OF THE I.WERTEBRATA.

into whicli namerous pairs of pancreatic follicles dischargel
the digestive floid. The intestine becomes narrower at tho
posterior end, and terminates in an anus situated behind tJio
twentieth somite.

(31J The Anomtmra form a small order containing thi
hermit-crabs [PtujuHda'), They are distinguished from the
Mvcro'ira in having an nncalciGed and soft integument. The
appendages of the body are moreor less abortive through disuse,
while those of the sixth somite are modified to form claapers.
By means of the claspers the hermit-crabs are capable of
holding on to the columella! of the shellsofMolluscs which thf
Pdijuriilo: inhabit. The inner part of the Aiio7noii>-a are
somewhat similar in structure to those of the Mitcronrc

(32) The Brwhyura.. — This order includes the crabs. Thef^
abdomen is small and without a caudal "fin/' It ia carved
round against the channelled ventral surface of the thorax,
The mouth lies between the mandibles, and is a wide aperture,
bounded by the labrum in front and the metastoma behind.
It leads into a wide but short tesophagus. The resophagna
opens almost ventrically into a large stomach of globular
form. The walls of the stomach, as well as those of the
tesophagus, are lined by a chitinous extension of the exo-
skeleton — the so-called teet h. The function of these chitinooB
teeth is to divide and macerate the food before it passes into
the intestine. The posterior part of the stomach of the
Bmchyura gradually lessens in diameter, and then leads into
the intestine, " The intestine passes backwards with a slight
vertical bend to the base of the penultimate abdominal
segment." The so-called liver, which is essentially pancrentio
in function,* consists of two symmetrical halves. This large
bilobed organ extends the whole length of the cephalo-thorax ;
and the numerous ctecal tubes (arranged in tufts), of which it is
composed, are clearly seen under the surrace of water. The
ciecal tubes of each half of the digestive organ lead into a

' Dr. Grirtithn' paper in the Procuilingt of Boyal Socltlg 0/ Etliniurgli,
vol. 16, page 178.

PHYSIOLOGY or THE INVERTEBRATA. 59

" bile-dnct," which opens into the anterior portion o£ the
intestine.

(33) The Macmura form the last order we have t(. consider

f the Crustacea. To this order belong the lobster {Ilunuirus),
nyfish (AMitcvs), and shrimp (Pala-mon).
The alimentary canal Is well defined, especially the stomach.

fx> rHYSIOLOGy OF THE JNVERTEBFATA.

As an exniiiple of the Miin-ovm, we describe in detail the ali-
mentary canal of Ast'icii^ flurintUis (the fresh -water crayfish).
The mouth lies behind the mandibles, and is a wide apertnie
botinded by the labrum in front and the tnetastoma behind.
This oral aperture leads into a wide but short cesopba^ns
situated on the ventral side of the head. The Q>soph&(^s
opens almost rertically into a large stomach divided into
cardiac and pyloric portions. The pyloric jrortion, dilated
dorsatly in a CiCcum, passes
w^ ^fl^k~" ^ directly into a long tabularJ
^^^^^^^^■''^^r intestine, which dilates into ■
Hv^^^bJH,^ small rectum, and finally i
^^^^^^^H^ 'iiinateB in an anns (Fig. 13)4
^^^^^^^^^^_^ 1'he only lateral appendage t
^^B I ^^V^ thealinientary canal (if .-!.>:/([/■
«V I ^B i» the so-called liver (Figs. lA

▼ ■ y find 16), whose dncts open i

I •* each side of the pyi'irns, Th»B

I so-called liver is in reality a

I digestive gland or pancreas,

m — tic and consists of numeroas ceecal

I- C\x,\i. Ill' tubes, whose microscopioal
st.mcture is represenled in Fig.
adi. t - aa- 16, There are no other ctecal
f1oric"mn of app^nda^es to the alimentai;
pyloric ossicle, canal of Antitciu ; in this i«-
^rs<^iTJd"ii.^.''"^*='^i™m spectthe crayfish differs fro

I = lolestine. * = rectum. the Btiichyurn and EOI

Mttcronra. But it may
stated that " in many ( 'i-^i-n/iu-m the digestive canal is s
rounded by cells filled with oily or fatty matter of a yelloi
or blue colour ; they may be compared to au omentum, i
probably serve as a store of nutriment, to be drawn 1
during the moult, or when food is scarce,"

There are no salivary glands in Ashmis flui-Uiiilis. As t
stomach of the ci-ayfish (Fig. 15) is far in advance of any-fl

FlC, 14 —

PHYSIOLOGY OF THE INVERTEBRATA. 6i

previously described, it is important that a full detailed
deacription of it should be given. As already stated, the
stomach of Astficim is divided into cardiac and pyloric

■r.. .s.-Lr.sciTU

= cesophagiu. f — poiiiiun of gatirolilh. c = laieral looih. d = piero-
Lo tmiclc. I — anierior gaslrEc muscle. / = cardiac ossicle, g — uni-
b cardiac procos. A = lygocnrdiacosiiclr. i — pre-pyloric ossicle, t — median
^'toMh. / = pyloric ouicle. w — posterior gutric miucle. a = BeGum,
inn pjlorie valve. /> = aptnure of "bile" duel. 1/ = laieial pouch.
K*- = cardJD-pylaric vaWe, i = inmiinc. / = laieral pj'Ioric valve v ^ small
" ~ " )r lootli.

rtioQS. The internal
alls of the anterior
iialf of the cardiac por-
tion are membranoua
and are invested with
numberless miuuti'
bairs ; but in the pos-
terior half the walls
are strengthened by
calcified and chitinous
ossicles which are so
arranged as to form a gastiic mill or gizzard. Professor
Huxley ' describes the gastric mill of Astacvs in the following

.„.,j.jlnr

mh. p. :

pfiysioLOGy OF the invertebrata.

words: "It consists, in tha first place, of s transverse,
slightly arcuated cardiac plate, calcified posteriorly, wliicli
extends across the whole width of the stomach, and articalat«»
lit each ext.reruity by an oblique suture with a small cur\'ed
tviangular antero-lateral or pterocardiac ossicle. Ou each
side, a large, elongated poatero-lateral or zygocardiac ossicle
wider posteriorly than anteriorly, is connected with the lower
i-nd of the antero-lateral ossicle, and. passing upwards and
backwards, becomes continuous with a transverse arcuated
plate, calcified in its anterior moiety, and situated in the roof
of the anterior dilatation of the pyloric portion ; this is the
pyloric ossicle. These pieces form a sort of six-sided frame.
the anterior and lateral angles of which are formed by mov-
able joints, while the posterior angles are united by the elastic
jiyloric plate,

"From the middle of the cardiac piece a strong calcified
urocardiac process extends backwards and downwards, and,
immediately under the anterior half of the pyloric ossicle,
terminates in a broad, thickened extremity, which presents
inferiorly two strong rounded tuberosities, or cardiac teeth.
With this process is articulated obliquely npwards and
forwards, in the front wall of the anterior dilatation of the
pyloric portion, and articulates with the anterior edge of the
pyloric ossicle, thus forming a kind of elastic diagonal brace
between the urocardiac process, and the pyloric ossicle. The
inferior end of this pre-pyloric ossicle is produced downwards
into a strong bifid urocardiac tooth. Finally, the inner edges
of the postero-lateral ossicles are flanged inwards horizontally,
and, becoming greatly thickened and ridged, form the large
lateral cardiac teeth. The membrane of the stomach is con-
tinued from the edges of the pre-pyloric to those of the
postero-lateral ossicle in such a manner ai5 to form a kind of
pouch with elastic sides, which act, to a certain extent, as a
spring, tending to approximate the inferior face of the pre-
pyloric ossicle to the superior face of the median process of
the cardiac ossicle,"

PHYSIOLOGY OF THE INVERTED RATA. 63

There are four principal muscles (see Figs. 14 and 1 5) which
work this complex stomach. The two anterior gastric muscles
attached to the cardiac ossicle, ascend obliquely forwards and
are fixed to the inner surface of the carapace. The two
posterior gastric muscles attached to the pyloric ossicle are
also fixed to the carapace. The food torn to pieces by the
mandibles is crushed into a fine state of division in the
cardiac portion of the stomach. The thick walls of the
pyloric portion are covered internally with long hairs. These
project into the interior forming a kind of strainer, which only
allows the nutritive juices and fiaely divided particles to pass
into the intestine.

At the sides of the cardiac portion of the stomach, embedded
in its tissues, are usually to be found in the summer two cal-
careous masses or plates, known as gastroliths. At the period
when the crayfish moults the gastroliths are also cast. They
weigh from two to three grains ; what their function may be
is still unknown. Possibly, they may be simply deposits due
to an excess of calcareous matter in the system.*

We have now come to the end of the great class, Arthro-
PODA. The majority of its members, excepting degenerate
types, have well-defined digestive apparatuses. Often, as in
the Crustacea and Inscda^ the intestinal epithelium is famished
with a hard layer of chitin (Cj^H^NjOiJ, sometimes raised
into projections destined to crush and macerate the food. The
month is either suctorial, masticatory, or biting ; and in the
Cru^acea certain anterior parts of the intestinal canal become
buccal pieces. In some of the lower Arthropods there are
present both salivary glands and so-called livers ; in others,
either one or the other organ is absent — e.g., both salivary
glands and "livers" are present in the Orthoptcra, Colcoptera,
and Arthrogastra. In the Lepidoptcra^ Arctisca^ and DUopoda
only salivary glands are present ; and in the Xijihosura and
Odracoda there are only the so-called livers or digestive

• See also Irvine and Woodhead in Proc. Roy, JSoc. Edin,, vol. 16,
P-330.

64 PHYSIOLOGY OF THE INVERTEBRATA.

glands. The " liver " iu tlie lower Arthropods consista of
caacal prolongations of tho intestinf, but in tlie higher
Cnislnccn it bfcomes an organ of considerable size. As a
rule the salivary glands are better differentiated in the
Iiisfcta and Aiwhniila than in any of the other classes of the
ArthropOiio.. But the largf bilobed liver, or, as we prefer to
call it, the pancreas, is characteristic of the Cnislitou,
espfcially the higher forms. It appears that the salivar}'
glands and pancreas are interchangeable, sometimes one
replacing the other.

It may hv remarked that in many of the Artkropoela tbttS
alimentation considerably infiuences both the form and thtfl
dimensions of the digestive apparatus. Carnivorous suitnalii
have a dtgestivo apparatns which is comparatively ehort.
Caterpillars, which are most voracious, have wide intestines,
while the butterflies, which eat little, and only liquid foodi^
have long and slender alimentary tubes. Certain genera oSm
the Insefta {E^'hemcra, Bombyj; d-e.) which are very voraciouaJ
as larvae, are in the mature state destitute of organs of manda-
cation. Wholly destined for generation or reproduction, the]
cannot take any nutriment ; hence the brief duration of tbei
lives.

The I'OLYZOA.

The Mahjcoscolices, one of the Malacozoio Series, is di?ii
into two great classes — the J'ali/zoa and BrmJn'opodi
the former class is subdivided iuto four orders.

The Po/i/zoa have a mouth surrounded with tentacola, an
enlarged alimentary canal, sometimes furnished with denti-
form projections destined for mastication. Occasionally there
exists a sort of stomach.

Most of the Foli/zoa are microscopic animals ; but, living lo.
colonies, they sometimes form conspicuous masses ; conse-
quently they bear a resemblance to the Sertularian Hydrozoa.

(i) The l'o(foslomutii. — This order is represented by the
genua lUuihilu^kuru. The disc or lophophore is horseshoe-.

PHYSIOLOGY OF THE INVERTEBRATA.

flh&ped. In the BJuiMffplexmi the tentacula are i
but longer, than any other Polyzoa; in this respect they
somewhat resemble the Brachiopoda. " The mouth is
idtnated beneath the free margin of the disc, on the opposite
Bide to the anus."

(2) The 1'hi/luctolfcm.ata are all fresh-water Poh/soa. The
mouth (Fig. 1 7) is situated
on the lophophore, and
B Burrounded by a num-
ber of ciliated tentacula.
The month leads into an
(esophagus which passes
into a muscular phaiyux.
"The particles of food
are carried down the
inner surface of each ten-
tacle, and the mouth and
pharynx expand to re-
ceive snch B» are appro-
priate, as if by an act of
Belection. The rejected
particles pass out between
the bases of the tentacula,

■ or are driven off by
the centrifugal currents."
The muscular pharynx
leads into a capacious
stomach . The narrow
intestine is continued * = neivous ganglion.
from the posterior end of

the stomach, and terminates in an anus sitnated near the
month. The intestine is bent backwards, so that it runs
almost parallel with the anterior portion of the alimentary
canal. The walls of the stomach are studded with cells or
■ follicles of a pancreatic nature ; and its orifice is surrounded

^^L bv cilia. The food particles are constantly regurgitated into

«6

PHYSIOLOGY OF THE INVERTEBRATA.

tlie middle portion of the stomacii (which is sometimes called
a gizzard), and, aft^r having undergone a further oommina-
tion, are retnrned to the anterior portion of that organ, where
they are kept in constant agitation. These particles finally
pass into the intestine. The undigested portion o£ the food
agglomerates into small pellets which are carried upwards
and are expelled through the anus.

The alimentary canal of the Polyzoa is devoid of salivary
glands.

It has been stated that the Poli/zoa resemble somewhat the
Sertnlariau Hydrozm, but it must be distinctly understood
that the I'oli/zooii. has not merely a digestive cavity, like the
H/i'Jra and the Acliitiii; for the digestive apparatus of the
former is dlfierentiated into a pharynx, stomach, and int^istiiie
provided with an anal aperture. In fact, the Polifvxm has a
complex and highly developed digestive system. Then, again,
the Polyzoan tentacula differ from those of the Hydrozoa and
Aclittozoa, in being somewhat stiff and provided with cilia.

(3) The GymiioUemata are marine Polyam, except Pal^
txlla, which is a fresh-water form,

(4) The Pcdiecllinea. — In this order the bads, produced
gemmation, become detached from the original stock.

The Bbachiopoda.

This class is divided into two orders, the TrctentertUa
the Clislcnteraia. They are all marine animals "prorided
with a bivalve shell, and are usually fixed by a peduncle,
which passes between the two valves in the centre of the
hinge line, or the region which answers to it li those Bracli>>
opods which have no proper hinge."

(l) The Trdaitevnta have no hinge. The mouth or 01
aperture leads into an (esophagus, which passes into a stomaott
provided with pancreatic follicles. From the stomach passeti
the intestine, which opens into the cavity of the pallium or
mantle on the right side of the mouth. The alimentary canal

iftott
hssefi
a or
:anal ■

PHYSIOLOGY OF THE INVERTEBRATA. 67

la suspended in a spacious perivisceral cavity. " The walls
of this cavity are provided with cilia, the working of which
keeps np a circulation of the contained fluid." In lAngida
the intestine is long, and forms two bends before it terminates
in the pallial cavity.

(2) The Clistenterata have a hinge uniting the two valves
of the shell. In the Terebratida the mouth opens downwards
into the pallial chambers, and is situated in the middle line,
aboat one-third of the length of the shell from the hinge.
The mouth of the Brachiopoda has no rudiments of a maxillary
or dental apparatus^ The oesophagus in Terebratula is short,
and is situated between the anterior portions of the so-called
liver. The stomach is an oblong organ which is dilated at
the cardiac end; the narrower may be spoken of as the
pyloric portion, but there is no valvular structure at the
pylorus. The cardiac portion of the stomach is surrounded
by the so-called liver. The intestine is short, straight, and
is continued in a line with the pylorus to the interspace
between *' the attachments of the adductores longi and cardi-
nales to the ventral valve," where it ends blindly. The so-
called liver (pancreas) is a large organ consisting of numerous
ramified follicles. There are usually two ducts from this
organ, communicating with the cardiac portion of the stomach.
The alimentary canal is freely suspended in the body cavity
by delicate membranes which stretch from the body walls.

The MoLLUSCAt

The MMvjSca form the second division of the Malacozoic
ISeries ; and this division comprises seven orders.

(i) The Zamellibranchiata include the Ostrea, Analontaj
J^ytUus, Pecterij Cardiurriy Mya^ Unis, &c. The mouth is
bounded by lips, which are usually produced into two labial
palps. These palps are ciliated, and by the action of the cilia
food particles, which have passed into the branchial chamber,
are driven into the mouth. The mouth of a Lamellibranch

68 PHYSIOLOGY OF THE INVERTEBRATA.

carries no organs — -jaws or teeth — for the preliension or
maBticatioQ of food particles. It passes by a abort cesophagos
(Fig. l8) into an expanded stomach, which is embedded in

the so-called liver. At the pyloric end of the stomach a
diverticDlnm of that organ conbuns a rod-like body — the

crystalline style. The function of the crystalline style is most

PHYSIOLOGY OF THE INVERTEBRATA. 69

likely to mix the food particles with the secretions of the
stomach and those poured into it from the ducts of the large
digestive gland (** liver"), which surrounds the stomach.
The crystalline style is well-developed in Mya^ Cytherea^ &c. ;
but in Ostrea it only exists in a rudimentary state as a piece
of cartilage ; and in Phdas it is said to have the form of a
folded plate.

The Lamellibranch stomach leads into a long intestine,
which turns downwards and makes many convolutions among
the so-called liver and genital gland, and again comes into
the dorsal region, where it traverses the heart, leaving the
pericardium at its posterior end, and ultimately terminates in
an anus situated behind the posterior adductor muscle. The
anus is placed on a projecting papilla. That portion of the
intestine from where it enters the heart to the anal aperture
is usually called the rectum. In a transverse section, the
intestine is horseshoe-shaped, due to the folding in of its
dorsal wall, consequently forming a typhlosole. The so-called
liver, which is pancreatic in function, consists of numerous
branched caacal follicles. These are united into ducts which
open into the stomach by several irregular apertures. There
are no salivary glands in the Laincllihranchiata,

(2) The Scaplwpoda, — In Lentaliwm the mouth is sur-
rounded by many filiform tentacula which play the rdle of
prehensile organs. The mouth leads into a buccal chamber
containing the odontophore — a prehensile rasp-like tongue.
The buccal chamber passes into the oesophagus leading into
the stomach. The intestine then follows, and after being
coiled several times, terminates in an anus behind the root of
the foot.

The intestine of the Scaphopoda does not traverse the heart,
as in the Lanidlibranchiata, for that organ is entirely absent.
The so-called liver is bilobed.

(3) The Polyplacoplwra are vermiform MoUitsca without
eyes or tentacula. In Chiton the shell is unlike that of any
other Mollusc. It consists of eight calcified plates arranged

PHYSIOLOGY OF THE INVERTEBRATA.

iu a segmented, imbricated manner one behind the other.
The mouth is at one end of the body, and the anus at the
other.

(4) The Heleropodtt. — ^This order, which includes Atlanta, |

is sometimes immersed in that of the Gaslircpodn.

It may be remarked in passing that, although the £amd»
lihmm-hiuta have no salivary glands, these organs tat
frequently present in the OdontopJtwa, which include the
Scaph&pmia, Polyplaeopiiora, Ga^tropuiiat Pteropoda, and
Cfphalfipoila,

(5) The Giistcropoda are subdivided into the Piilmoffcut/tTO-
poda and the B'ranchiijgastei'opoda.

As an example of the digestive system of tlie Piihiio*
gastfi-opodii we describe that of ffdix (the snail).

The alimentaiy canal, which is much coiled, bends forward
to open by an anus in the mantle cavity. The mouthy'
situated at the base of the head-lobe in front of the foot,
bounded by lipa. It leads into a buccal cavity, into which
poured the secretion from two Isrge salivary glands (Fig, 19, a).
Then follows the CDsophagus, which dilates into a crop or pro-
ventriculus. The crop leads into the stomach (provided
with a blind ca?cal appendage) passing into a long-coiled
intestine embedded in a large many-lobed organ — the
called liver, which opens by ducts into both the intestine and
stomach. The posterior portion of the intestine bends anteriorly
and widens into a rectum which opens, by an anal aperture
situated on the right side of the body, into tJie mantle or
pallial cavity. The intestine of JTclie is folded internally so
as to form a typhloaole.

The two salivary glands are on each side of the crop, but
their ducts open into the buccal cavity. These glands present
diiferent degrees of devpinpment in different Gasteropods.
This is doe to the construction of the mouth and the naturti
of the food. In ffdix and Limax the salivary glands ara
well -developed organs; bat in CaJyplraa they are simple
tubes.

PHYSIOLOGY OF THE INVERTEBRATA. ?■

A. a = tnoulh. b — odonlophore, t = loolh. rf = buccail mass.
( = uaophagiH. /= Mlivnryducl. ^' = salivary gland. * = reclum-
I = crop or prove airiculus. t = [Dtesiine, / = liver, in — stomach,

B. Buccal Ma£5. a ~ lentncle (opiic organ). ^ — icniacle (olfactory
organ ?). c =: homy jaw. d = mouth, c — lateral lip. / = cir-
cuIai lip.

C. Longitudinal Section o( Buccal Mass. n = odontopliore. ^ = ra-
dulat- jncmbTHne. c = odonlophore cartilage, d - intrinsic muscle.

72 PHYSIOLOGY OF THE INVERTEBRATA.

The ductH from the large many-lobed " liver " (pancreas)
open into the stomach and anterior ixirtion of the iatestine,
The secretion of this organ is pancreatic in function.

The buccal ciivity (Fig. 19, B and c) is furnished with hard
masticatory structurep. The upper portion is provided with
horny jaw, and on the floor is the odontophore or radola.
This odontophore (lingual ribbon) ties over a cartilaginoui
support (Fig. 19, c). Powerful muscles are attached to this
supix»rt<, and by the alternate expansion and contraction of
these muscles the odontophore ia worked backwards and
forwards. By this mecbanism the food taken into the month
is ground down against the homy palate. The odontophore i»
ft chitinous product of the radular membTane (Fig. 19, c), and
is armed with tooth-like projections. The projections are
constantly being replaced as they are worn away by the
friction which ensues during mastication.

In the Branchioijasteroptxla (which includes Bticci;
J'utdla, Cijprn'n, i&c.) the alimentary canal doea not, as a rule,
vary very much from that of the I'li.lino'jfiderijpoda.

(6) The PU">i>poda are marine Molluscs. The foot, which
ia small, is provided with two large, muscnlar, wing-like fins
(epijjodia)." Ill Jfi/alaa the (esophagus dilates into a kind
of crop or proventriculus, which ia followed by a cylindrical
stomach. The intestine is tubular, describes two convolutions
in the substance of the liver, and then terminates in an anus,
situated beneath the right fin.

(7) The Cfphalop<x!a.^This order is divided into the'
IHIji'anehiata and the Tctrahrauchiata ; and the former ordi
is subdivided into the Dccapoda and the Oclopoda.

The DUmtJichiata include Sepia, Octojnis, Argonauta, &c
As an example of the digestive system (Fig. 20) we describe
that of Srpia oJfiHiMlis. The mouth, armed with two
chitinous jaws which overlap each other, is provided with au

PHYSIOLOGY OF THE INVERTEBRATA.

odontophore. It leads into a long oesophagaF, which is
narrower in the Dibranehiaia than in the Tetrairanchiata, and
then dilates into the mnaoolar stomach. The pyloric portion
of the stomach commanicates with a glandular sao — the
pyloric csecam. The intestine is bent somewhat upon itself,
paaeing towards the neural

^ventral) end of the body ..-.---i"" "■ ""V". ■

and terminating in a median
anos. One or two pairs of
salivaiy glands are present
in the DibranchieUa, which
poar the secretion into the
bnccsl cavity or the anterior
portion of the (esophagus.
The so-called liver ia a well-
developed bilohed oi^an
provided with two dncta,
which in ^^i.&Deeapoda receive
the ducts of a large number
of Cfecal appendices. It
has been considered that
these appendages are the
mdimente of a pancreas;
but there is no doubt that
the so-called liver per sc is
essentially pancreatic in
f onction. This organ does
not give rise to any of the
Inliary acida (glycocholic
and taorocbolic acids) nor
glyct^n. The colouring
matters which the so-called liver contains, do not answer
chemically to bilirubin and biliverdin. But its secretion con-
tains leucin, tyrosin, and a ferment (or ferments) which con-
Terts starch into glucose.

The ink-bag is a tough, fibrous, glandular sac. It is usually

= buccal mass, b = salivary glands.
= oesophagus, d — so-called liver.
{ = pancrealic follicles Iso-called).
= stomach, g = pyloric caecum.
-- ink-bag. i = intestine. * = anus.

74 PHYSIOLOGY OF THE INVERTEBRATA.

of an oblong piriform shape, and secretes a brown op black
fluid, the colour of which is yery durable.

The Tftrabranckiatct are represented by the only existing
genus, A'auiilua, which is provided with an external chambered
eiphuQculated shell.

Like that of the Se^na, the mouth of the Nautilvs h armed
with powerful jaws (Fig. 21). It leads into an <BBopIiagu- .
which dilates into a wide crop. The crop passes into t

FiC. ai.— ALfMENTAkV Canai

= buccal mass, i = cpsopliagus. r = crap.

• /»

us. A = so-called U'

Btomach whose internally chitlnous lining is thick and ridged.
The ctecum in Nmitil us iB&ma\\,&nd is attached to the anterior
portion of the intestine. The intestine makes two abrnpt
bends and terminates in the branchial cavity. In NnutUict
there are no salivary glands, unless certain small glandular
bodies within the buccal cavity possess that function. The ao-
called liver is a racemose tetra-lobed gland, and its fnnctit
IB, A pi-iori, that of a pancreas.

The Tdralrranchiata have four gills and numerous sht

PHYSIOLOGY OF THE INVERTEBRATA. 75

retractile tentacnla without sackers ; while the Dibranchiata
possess two gills and from eight to ten tentacnla with suckers
round the head.

From what has been said, it will be seen that the Mollmca
have a very complete digestive system which is comparable,
in a great measure, with that of the Vcrtebrata. In some
of the Mollusca we find a long oesophagus and enlarged
stomach, an intestine with circumvolutions, and a rectum.
In others, we observe the stomach arranged more or less
after the plan of certain Vertebrates ; there are cardiac and
pyloric portions, separated by a salient fold. "Sometimes
the stomach is furnished with triturating booklets of varied
form. But it is especially by the development of the
glandular appendages that the stomach of the MollvMa is
distinguished from that of the animals hierarchically inferior.
These organs, in fact, go on perfecting and complicating
themselves more and more in the diverse families of Molluscs,
and especially in the more advanced of the Molluscs — the
Cephalopods (Cuvier) — there are oesophageal salivary glands
with short caeca, a liver (so-called) developed, compact,
divided into lobes, provided each of them with an excretory
conduit or duct, and all these conduits or ducts open together
or separately at the commencement of the median intestine,
or into the stomach." But this *' liver " is essentially pan-
creatic in function: the true Vertebrate liver is entirely
absent in the Invertebrata.

The Pharyngopneustal Series.

This series is divided into two orders — the Hemkhordata
and the Urochordata (Tunicata).

(i) The Hemiclwrdata are represented by a single example
— Balanoglossus, which is " an elongated, apodal, soft- bodied
worm, with the mouth at one end of the body and the anus
at the other.'' The mouth, surrounded by a well-marked
lip, leads into a wide oesophagus which opens into a stomach.

PHYSIOLOGY OF THE INVERTEBRATA.

From the atomach passes the inteBtine, which terminates 13
an anal aperture situated at the posterior end of the body.
The mouth is provided with a proboscis,

(2) The Umchurdala- or Ttuiicata. — As an example of this
order we describe PhalliLsia mvntula (Fig. 22). The oral
aperture leads into the
phaiyngeal-reapiratory
chamber, from which
the cesophagns, situated
on the posterio-neural
side of the body, selects
the food particles intro-
duced into thatcbamber
by the action of small
teutacula. The walla
of the phar}'ngeal-re-
spiratoiy chamber are
gathered into ciliated
folds, which have a
number of slit-Hke per-
forations. These act
as a kind of sieve,
the haemal side of tl
pharynx there
ciliated groove bounded
by two gliindular folds
(the endostyle). The
CBSOphagus leads into
an internal-folded sto-
mach. The intestine,
which forms a loop, terminates in an anus situated opposite
the atrial or cloacal aperture on the neural side of the body.
The Savigny tubules lie upon, and open by a duct into, th*^
stomach. These tubules also ramify over the wall of (
intestine, and are pancreatic in function. Tbey are presenl
in nearly all the Tunieala.'

* Gee Chaadelon in JJufl. Actut. Be'g., 1875 ; and Dt. W. A. Herdrnan i

act

a = moiitli, i = imlacles. t ^ inlesllne.
rf = slomneh, ( = heart, /= oaopbagus.
g = Savigay's tubules, >l = snus. t = alrial
aperture.

PHYSIOLOGY OF THE INVERTEBRATA. 77

In Appedundaria there is a caadal appendage which
contains a notochord; bat in the Ascidians the caudal
appendage is only present in the larval condition of the
ooimal: — ^a condition closely resembling the tadpole or larval
frog. In fact, these animals are degenerated Vertebrates.*
Another point in which the Ascidians approach the Vertcbrata
is that the pharynx is also a respiratory cavity.

We have now come to the end of oar chapter on Inverte-
brate digestion in general. Below the Actinia the alimentary
canal commnnicates with the body cavity, bat with the excep-
tion of the Tunicatayin all those forms higher (than the Actinia)
in the animal scale, the body cavity and alimentary canal are
entirely separated from each other.

In regard to the masticatory apparatuses ; (i) a gizzard
is observed in the JRotifera, Oligoclujeta, the higher Insccta^
Polyzoa, Oasteropoda, and Cephalopoda. (2) The com-
plex masticatory apparatus of Echinus, with its five jaws,
each traversed by a tooth, is probably nothing more
than altered epithelium which has become hardened. (3)
Hardening of the membrane of the buccal mass is a
farther advance in the apparatus designed for mastica-
tion; as these structures are at the commencement of the
alimentary canal, and are separated from the stomach. In
the Annelida {e.g., Lunibricus and Hinido) the so-called jawd
are hardened parts of the epithelium of the mouth. These
structures may be functionally compared to the teeth of the
Vertcbrata. (4) The Arthropoda present a highly developed
masticatory apparatus in the jaws, which are appendages of
the body segments. ''The simplest condition is met with
in the Myriapoda^ as the centipede. A small labrum above
the oral aperture, a pair of mandibles or hard crushing jaws,
a labium below the oral aperture, with side lobes. The
Arachnida (spider and scorpion) have labrum and mandibles,

the Challenger ReporU, 1882, part i. p. 49; 1886, part ii. pp. 22, 52 and ^ \
part iiL pp. 22 and 42.
* See Bay Lankester's book, Degeneration^ p. 41.

PHYSIOLOGY OF THE INVF.RTEBRATA.

and two pairs of more delicate jaws — the maxillre. These
are the side lobes of the labium of the centipede, specialised
into distinct lateral jaws. In the Aracknida, the mandibles
are extended into prehensile and off e nave clawe. The
maxillse in the spider are related in a remarkable manner
to the function of reproduction. The specialisation is there-
fore incomplete. The Crustacea have a labrum, two mandibles,
four maxilliE (the second pair representative of the split
labium of the Myriapodn), and three pairs of maxillipedes
(feet-jaws). These last represent the sis legs of the lasecta. J
The somites, which in the latter bear motor organs,
in the Critxtaccn organs that serve for mastication, but thq
are in structure closely allied to the true legs on the sao-
ceeding somites."

In the Li.'ia-ta, the labium, labrum, mandibles and maxiUsl
are all met with ; they present numberless and compleKl
modifications, but for all that are chiefly subservient to thai
functions of taking in or crushing food. (5) The odontophomB
or radula of the MoUascn forms a still further advance, as ifr|
appears to combine the functions of teeth and of a tongue.

As far as a sfomnch is concerned, the first indication of it J
as a separate organ is observable in some of the Echinoilennata
<.g., in the Astcndai, but the specialisation of the organ is in-|
complete, inasmuch as it forms a dual function, viz., that of ■ '
renal organ as well as being a gastric cavity. There is a true
stomach (a dilatation of the alimentary canni) in the Annelida,
Arthropoda, Poli/wd, BracMopoda, and Mollusca. The crop
present in the Iiisfda is simply a cavity which serves to store
the food before passing into the stomach. The intestine ii
straight, and without convolutions in many forms — as, fa
example, in the Aakriilm, Myriapoda, Arthrugastra, &c—
also in many of the Mullusca there is a beud or flemire in t,
intestine.

CHAPTER IV.

DIGESTION IN THE INVERTEBRATA.

Digestion in Particular.

In the present chapter we describe in detail the physiology of
the digestive fanction in certain selected types of all the
more important branches of the Invertchrata.

The Protozoa.

The Protozoa having no differentiated parts, the cell itself
performs, among other functions, that of digestion. This
f miction is diffuse in the lower animals, and only becomes
specialised or differentiated as we ascend in the zoological

scale.

The Porifera and Ccelenterata.

Among the animals with cellular differentiation — the

-Porifera and the Ccelenterata — the internal cavity of the body

C*3iorphologically identical with the alimentary canal, and not

'^'^tili the somatic or body cavity of other animals) has the

^^^^ction of a digestive cavity.

Concerning the function of digestion in Hydra fiisca^
"^^- Grreenwood* has recently come to the following con-
clusions : (a) the ingestion of solids is performed by slow
^^v^ance over the prey of lip-like projections of the animal's
^^^>atance. Entomostracea, Nais, beetle larvae, and raw meat
pifove the most acceptable food; innutritiouR matter does
^ot act as a stimulus to digestion, (b) The digestion of

• Journal of Phy Biology, vol. 9, 317.

So PHYSIOLOGY OF THE INVEftTEBRATA.

eocloeed food p&rticles takes place entirely oatside the
dermic cells wliich tine the eoteric cavity, and among tlieee
may be difitiDguished : (i) pvrifonn cells destitnte of large
vacnoles holding aecretory spheroles daring hoDger, and
these empty daring digestive activity; (2) ciliated vocnoUte
cells, often pigmented : the water of the digestive finid is
probably derived from the vacuoles, (c) The pigment occnn
as brown or black gr^ns ; it has an albuminoid basis. The
pigment resists solution in most chemical reagents, but
dissolves slowly in nitric acid, (d) A resnr'e sabstance of sii
albuminoid nature accnmnlates during digestion in the basal
part of the vacuolated cells, and eventually takes the form of
spheres. The excretory pigment probably takes it« rise in
some residue from this absorbed substance ; it is also possibles
that fat is similarly formed, (c) The medium in whict*
digestive activity goes on is probably not acid.

In Hydra viridis, which contains chlorophyll,* the mode or^^
natrition appears to be dilferent from that just descnbe^^
Gland cells do cot form a conapicnous feature in the endo-— "
derm of Hydra nriclis, and consequently digestive secretioc^
is less active.

If the vacuolated cella of the endoderm of Hydra fwta^^
contain a nutritive fluid we may reason, il priori, that the^
food vacuoles of the Protozoa probably contain a digestive "
fluid; at any rate the food particles nearest to these vacuoles
are always becoming smaller in size, showing that digestion is
proceeding.

In Hyilni riridis chlorophyll has probably a secretory as
well as a respiratory function. The same remark applies to
the chlorophyllogenous Protozoa. " Professor Huxley first
■bowed the presence of " yellow cells " in J7«(7flsswo//n, which
have also been found in almost all Kadiolartans. These
bodies Haf^ckelt considered as secreting cells or digestive
glands, comparable to the liver cells of AmpJiioxiis, and those
• Tliu cliloropiastida o( Prof. E, Ray Lankester, F.RS.

+ DU Ila'tioloritii, p. 136,

PHYSIOLOGY OF THE INVERTEBRATA. 8i

of VeleUa and Forpitay as described by Voigt. Subsequently
Ha^kel found starch in these cells, and concluded that this
fifikjt supported the idea of the nutritional function previously
assigned to them by himself.*

'* Cienkowskit in 187 1 endeavoured to show that the yellow
cells of Radiolarians were parasitic algse, since they survived
the death of their host, and multiplied subsequently, passing
through an amoeboid and encysted state."

There is no doubt that the ** yellow cells " do survive for
eome time in the bodies of dead Radiolarians ; but in regard
to Hydra and SpongUUiy Prof. E. Ray LankesterJ has shown
that '' the chlorophyll corpuscles of these animals are not algsa
at all (as stated by Dr. Brandt §), but differ in no essential
respect from the chlorophyll bodies of plants."

Dr. C. A, MacMunn|| has shown that "the chlorophyll
bodies of SpongUla^ Hydra^ Paranuedum, Ophrydium^ Vortex
viridis, and SterUor polymoi'phtis are of different size, colour,
and give different reactions, and a different spectrum, from
the * yeUow cells ' of Actinicc. With regard to size, the
' yellow cells ' of Antheacereus were found to measure i2/i
(= I2xy^^mm.), or 13/i down to lO/i; while in Para^
vncedum they measured from 6pL down to 3/it — i.e., less than
half the size of the former ; in Hydra viridis mostly from
6fi to 4fu The colour is a dull brownish-yellow in the
* yellow cells ' of Anthea, &c. ; while it is a fine green in the
Infusoria and Hydra. The spectrum in Spongilla, in Hydra^
and in the Infusoria is that of plant chlorophyll ; while in
the * yellow cells ' it is that of chlorof ucin."

The chief function of animal chlorophyll and alUed pig-
ments is that of respiration; but it is probable that these
pigments play an important part in sexual selection, in

* Jtna Zeittch, 1870, p. 532. |

t Arduv, Mihro. Anal, 187 1.

{ Quarterly Journal of Microscopical Science, vol. 22, p. 229.

4 MonaUh, AJcad, Wist, Berlin^ i88i.

I Proceedings of Birmingham Philosophical Society, vol. 5, pt. I, p. 212.

PHYSIOLOGY OF THE INVERTEBRATA.

mimicry, or act as " acreena " for the protection of imder
lying cells, for protective purposes; and possibly, though
not probably, they may have a nntritional fuuctioD, as sug-
gested by Haitekel. Wliatever may be the true function or
functions of animal chlorophyll, one thing is certain — that
the pigment is manufacturpd in the body of the animal con-
taining it. In the words of Dr. MacMunn : " I would ask
investigators to pause before they deuide that when an nnim^
chlorophyll is met with, it has been simply eaten bj- tbt-
animal, and deposited unchanged in its tissues ; they moEt
remember that the radicle of chlorophyll, like the radicles of
other pigments, may be furnished by the action of the diges-
tive juices of the animal on Borae substance furnished by the
plant, and that the animal laboratory is capable of building
up molecules quite as large as that of chlorophyll. Our own
htemoglobin is not the unchanged hiemoglobin of our food :
what is derived from it is broken up and then regenerated ;
and it shows an ignorance of physiologj- to suppostr that
chlorophyll should bean exception to a general rule,"

Reverting once more to the Fwifrva. Dr. \jkia Fredericq* ,
has extracted from a large number of sponges a fennel
analogous \a trypsin or pancreatiu. This ferment acta upon 1
starch, fata, and albuminoids. The author of the preseiitl
work fully confirms Fredericq's researches. The fermeitfr|
contained in and raannfactured by the cells of the Pofifm
converts starch into glucose. It forms an emulsion witbil
neut]-al fats, and finally decomposes them into fatty acids
and glycerol (glycerine). The ferment also converts albomi*
noids into peptones, which become partially converted into
leucin and tyroain. There is no doubt that the cella of' J
the Po'i-ifera secrete a ferment in everj' way aualogous ti
pancreatic ferment of higher forms.

The EcniNODERMATA.

Fredericq has also obtained similar results with

* Archirii lie Zoologit Kcpiriinciifale, lume 7, p. 400.

PHYSIOLOGY OF THE INi'ERTEBRATA. Sj

jciesof the Adinice, oaly the digfative ferment secreted by
the cells of these aniniala does not appear to have the aame
degree of activity as that extracted from the Porifera. Its
action is much slower.

The digestive apparatus of Uragter ruhem (one of the
Astcruifo) h»a been examined by the author. The a>alh and
contents of the wide sacculated stomach, and its five sacs do
not cuntun digestive ferments; for the digestive fiuid is

derived from the pyloric ctcca situated in each ray. The
Xyloric sac, or stomach, gives off five radial ducts, each of
^bich divides into two tubules (Fig. 23) bearing a number of
lateral follicles, whose secretions are poured into pyloric sac
«nd intestine,'

The secretion (of the oeca) was obtained from a large
Bnmber of star-fishes, and gave the following reactions : —

• ProeecliHgi 0/ Soyal S-i^Ulji of Edinbnr'jh, vol. 15, p. \
axdi'Hf* of BDyal Saclils of L-wlon, vol. 44, p. 325.

; and Pro-

rite

84 PHYSIOLOGY OF THE INVERTEBRATA.

(a) The secretion forms an emulsion with oils yielding
Bobsequently fatty acids and glycerol.

(b) The secretion decomposes stearin, with the formation
of stearic acid and glycerol —

C„H„„0, + 3 H,0 - 3 C„H„0, + C,H,0,.

(c) The secretion acts npon starch paste with the formation
ofdejrtrose. The presence of dextrose was proved by the
formation of brownish-red cuprous oxide, with Fehling's
solntioD.

(il) The aecretiou dissolves coagulated albumin (hard white
of egg).

((■) Tannic acid gives a white precipitate with the secretion.

(/_) When a few drops of the secretion of the pyloric o«8
are e:^amined chemico-microscopically, the following re-
actions are observed : — On running in, bet\eeen the slide an*^
cover-glass, a solution of iodine in potassium iodide, a brow"*
deposit is obtained ; and on running in concentrated nitr*-''
acid npon another slide containing the secretion, yello"^ *'
xanthoproteic acid is readily formed. These reactions ebo^^
the presence of albumin in the secretion of the organ is^ '^
question.

(7) The presence of albumin in the secretion was furthe*^
confirmed by the excellent tests of Dr. R, Palm.*

(/() The soluble enzyme or ferment secreted by the cells o^^"^
the pyloric cffica was extracted by the Wittich-Kistiakowsky"*^
method-t The isolated ferment converted fibrin (from the^^
muscles of a young mouse) into leucin and tyrosin.

(1) The albumins in the secretion are not converted into
taorocholic and glycocholic acids ; for not the slightest traoee
of these biliary acids could be detected by the Pettenkofw
and otlier tests.

0) ^° glycogen was foond in the organ (i.e., the caeca) or
aecretion.

From these investigations, which have been repeated

t P/lOgeft Arehh-yar PhytiotogU

t, vol. 14, pt. I.
vol, 9, pp. 438-459-

PHYSIOLOGY OF THE INVERTEBRATA, 85

other genera besides Uraster, the pyloric casca or diverticula
of the Asteridea are proved to be pancreatic in function.

Dr. L. Fredericq (the distinguished Professor of Physiology
in the University of Lidge) has obtained similar results, but
by an entirely different method. Fredericq obtains various
aqueous extracts (neutral, alkaline, and acid) of the caaca
previously hardened in alcohol. These extracts each contain
the digestive ferments. They digest cooked and raw fibrin
exceedingly well in alkaline extracts. This action is less
active in neutral extracts, and is almost nil in acid extracts.

The pyloric caeca of the Asteridea are consequently diges-
tive organs — their function being similar to that of the pan-
creas of the Vertebrata.

Dr. MacMunn* has shown that these pyloric caeca '' con-
tain a large quantity of enterochlorophyll, mostly dissolved
in oil, which may possibly act in supplying oxygen to the
tissues of the animal, perhaps from the waste carbon di-
oxide." If this be correct, the pyloric caeca perform a dual
function — ^that of a digestive and a respiratory organ.

It may be stated that the stomach or pyloric sac of
Uraster rvbens is a digestive cavity and a renal organf — i.r.,
it has a dual function. Darwin states, in The Origin of Species
(chap, vi.), that " numerous cases could be given among the
lower animals of the same organ performing at the same time
wholly distinct functions ; thus, in the larva of the dragon-
fly and in the fish — Ccbites — the alimentary canal respires,
digests, and excretes."

The Trichoscolices.

Dr. Fredericq has investigated the nature of digestion in
Toenia serrata (one of the Cestoidca), which inhabits the
small intestine of the dog. His experiments were conducted
in the following manner : — Three tape- worms, killed by chloro-

* Proe. Birmingham PhUoBop, Soe, voL 5, pt. 1. p. 214.
t See Dr. A. B. Griffiths' paper in Proceedings o/Bagal Society of London^
vol. 44, p. 326.

86 PHYSIOLOGY OF THE INVERTEBRATA.

form, were washed in water, and then cleaned by meai
"brush. They were cut into small pieces and left to harden,
for twenty-four hours, in a lariie quantity of absolute alcohol
Aqueous extracts (neutral, alkaline, and acid) were made of
the hardened pieces; but each extract was found to be com-
pletely inactive as a digestive fluid. Fibrin remained intact
io tliem during many days.

These e.Ytracts bad a milky appearance, due to an totense
fluorescence, which immediately suggested the presence of
glycogen. A solution of iodine (in water) converted these ex-
tracts into brown -colon red liquids. They fornitd a precipitate
in the presence of alcohol, which was dissolved by copper aal-
phate and potash.

Finally, the addition of saliva caused the opalescence
disappear, and at the same time the liquid became rich
glucose, as proved by Fehling's solution. It mast be
tinctly underetood that this glycogen is not present in ti
internal fluids of the tape-worm's body, but ia present in ti
integument of that animal. Glycogen is also present in t]
integument of the Nvmatoidm.

It ia seen from these investigations that the Cestoidt
and possibly the Tremaloda as well, do not contain any trac
of digestive ferments, either pepsin, trypsin, or diastatio
ferment.

The juices of the small intestine in which Tentia serratt
lives are, nevertheless, rich in ferments; but these fermenUi
having little diffusive power, do not pass the barrier »
the external skin of these Entozoa offers them. This
proved in the following manner :— Some A^carts marginiU^
(belonging to the Ximatoidco), obtained fi-om the small in-
testine of a dog, were placed, some intact and othera cut
into pieces, into an artidcial pancreatic juice.* Those which
were left intact remained in the juice without apparent
change; but those cut into pieces were almost completely

PHYSIOLOGY OF THE INVERTEBRATA. S7

^digested or dissolved — only leaving the horny integument
{hyalin). This integument did not appear to be formed of
•chitin, for it was rapidly attacked by a boiling solution of
potask.

The Annelida.

(a) The Hirvdinea. For this purpose Fredericq cut into
pieces twelve horse-leeches (Hcemophsis va?'ax), and from these
pieces he prepared two extracts, one acid and the other alka-
line. Fibrin was digested (in twelve hours) in the alkaline
extract, but was unaltered in the acid extract.

The author of the present volume has obtained similar
results with Hirudo rnedidnalis. Digestion, therefore, in the
Hirudinea is somewhat similar to the pancreatic digestion in
the VertebrcUa.

(b) The Oligoclujcta. In this order, represented by Lumbriciis
tcrredris, the digestive system (Fig. 24) is more highly de-

FiG. 24.— Diagram of Anterior Portion of Alimentary Canal

OF LUMBRICUS.

a = mouth, b = salivary glands (?). c = oesophagus, d = pharynx.
e = caldferous glands. / = crop, g = gizzard. A = intestine.

veloped than in any other animal already alluded to in the
present chapter.

If the head or anterior portion of Luirdtricics (as far as the
sixth segment) is severed from the body, and that part of
the alimentary canal which it contains is dissected out of the
head, and is placed on starch, it will be converted into
glucose, but it has no action on fibrin. From this there is
no doubt that the saliva is poured into the pharynx. This
secretion bathes the food (which is of a mixed nature)
daring its passage through the oesophagus. Attached to

l ot

88 PHYSIOLOGY OF THE INVERTRBRATA.

the Bides of the posterior end of tlie cesopba^s ar*" thrW '
pairs of calciferons glands. These frlaads secrete a suV
etance extremely rich in calcium carbouate. The function of
these glands in secreting calcium carbonate is to neutral
the vegetable acids of the food, for the digestive fluid
LuvibricHs is inactive unless alkaline. The food and duids u
the crop of the earthworm are always alkaline. In the crop
the food matter ia stored before it passes into the gizzard.
whose powerful muscular walls and thick chitinous lining
crnsh any food-stuffs that require mastication or grinding.
The posterior portion of the gizzard has thinner walla, and
leads into the long glandular intestine, which is lined with
columnar cells. The intestine is almost enveloped
yellowish glandular tissue — the so-called liver. This oi^an
essentially pancreatic in function.*

There is no donbt that the principal digestive fluid
worms is of the same nature as the pancreatic juice of tl
Virtcbrata. Dr. L&n Fredericq (Archives lie Zoologie Exjj^rirj
mailfili; vol. vii. p. 394) proved this in the foUo>
manner : —

A large quantity of worms, chopped into small pieces,
treated with strong alcohol. The alcohol is left to act for
many hours ; and then decanted. The alcoholic extract is
used in the examination for biliary acids. The insoluble
residue is pressed between several folds of filter paper, dried
in air, and finally pulverised in a mortar. The pulverised
residue is divided into several parts, the object being to-
prepare several aqueous extracts (neutral, alkaline, and acid).
The dilute acid solutions used in preparing the acid extracts
are made from hydrochloric acid and water (the degrees of
concentration being from six to twelve cc. of HCI per litre
of water). The divided residue (previously atlnded to)
is allowed to macerate in the fluids for twenty-four hours ;
and then filtered. The filtered liquids are placed in separate
test-tubes in each of which a small piece of fibrin has been

• Dr. A. B. Grimtlis- paper in fiw. Ilwj. .Soc. Ediul.., vol. 14, p. jj;.

PHYSIOLOGY OF THE JNVERTEBRATA. 89

suspended. The test-tubes are then placed in an incubator*
heated to about 40"^ C. At the end of an hour or so,
the fibrin which is in the alkaline extract has almost en-
tirely disappeared ; leaving only a small quantity of finely
divided detritus. This liquid contains peptones.

The neatral extract acts in a similar manner, except that
the fibrin is dissolved a little more slowly ; it takes from five
to six hours t6 complete the digestion. This liquid also
contains peptones.

The most concentrated acid extract has no action on the
fibrin, which swells, but remains intact during many days.
On the other hand, the fibrin is dissolved more or less
completely in the dilute acid extracts, but to do this it
requires from thirty-six to forty-eight hours.

The ferment in which Zumbricm dissolves the fibrin acts
well in a neutral solution, better in an alkaline solution, and
badly or not at all in an acid solution; these properties
entirely resemble those of trypsin or the pancreatic ferment.

The neatral extract converts starch into glucose. The
aqueous extract, therefore, contained a substance or ferment
which acts in a similar manner to diastase.

Fredericq having dissected a large earthworm (under
water), removed the whole of the alimentary canal, and
obtained from the intestine a fluid which is slightly alkaline
and readily digests fibrin. This alkaline fluid is secreted by
the glandular tissue which almost covers the intestine. The
organ has been termed a '* liver," whereas it is a true
pancreas. The names " bile " and " liver " have been
employed at random by a great number of those who have
iQvestigated the anatomy of the Invertebrata. Nevertheless
the principal characteristics of the bile (pigments and biliary
acids) have never been discovered with exactitude in any
animals lower than the cranial Vertebrates. There is nothing
in this fact which ought to surprise us, because it is

* Like the incubatora nsed in bacteriological laboratories. See
Griffiths' Researches on Micro-OrffanUmSj p. 17.

90 PHYSIOLOGY OF THE INVERTEBRATA.

established that the colonring matters of the hile an
derived from one of the prodacts of the decomposition of
hiciiioglobin {probably of hEemochromogen), a Bobstancr
which is not foond, except very rarely in the InveHehrata.

The earthworm ia one of these animals rich in hiemt^lobin,
consequently one would suppose that liver pigments and
biliary acids would be present in this Invertebrate animal.

Tlie alcoholic filtrate from the macerated worms (already
referred to) would contain (if present) these pigments and
acids. This filtrate is very rapidly discoloured on exposure
to daylight, but, besides the colouring matter which is
sensitive to light, it often contains traces of chlorophyll (from
food).

The alcoholic filtrate is evaporated to dryness on a 'n
bath, and the residue treated with ether. The
solution is reserved for future examination, while the
insoluble residue (in ether) is dissolved in a small cfoantity
of water. ITie filtered a(|ueous solution is now aaed ia
testing for biliarj' acids by the Pettenkofer test ; but not the
slightest trace of these acids is detected in Lumhrieits. The
reaction of Gmelin and Tiedemann. employed in detecting
the presence of biliary pigments, was applied without sucoeak J
to the fresh juices and organs of Lmnlrrinis ; also to tlMS
alcoholic extracts (from which the alcohol bad been evapo* 1
rated).

The ethereal extract previously obtained was found to]
contain cholestrine and fatty globules.

In addition to the pancreatic ferment, the author i
detected iudol (C.H,N) as well as leucin and tyrosin in (
fresh juices and organs obtained from about 4 lbs.
eaithworms. This is an additional proof of the pancreatu
nature of the digestive fluid of Lumbricus.

Although biliary pigments are entirely absent in tlie
Oliffociiata, other pigments are present. Most likely the
pancreatic tissues, which almost envelop the intestine of
Liimhm^iis, contain enterochlorophyll.

PHYSIOLOGY OF THE INVERTEBRATA. 91

In the words of Dr. MacMunn {loc. cit, p. 189), ^*the
radicle indol is furnished by the action of pancreatic ferments
upon food proteids ; and as the so-called liver of Invertebrates
is really a pancreas in at least some of its functions, possibly
some such radicle may be changed by a ferment furnished by
the * liver ' into enterochlorophyll."

Not only is the digestive fluid of Lumbrims capable of
acting upon starch (as already stated), but it readily attacks
cellulose ; this fact agrees perfectly with the kind of food-
stu& which the earthworm consumes.

(c) The Polychoeta. — In Nereis, a pair of salivary glands
are appended to the base of the proboscis. The secretion
obtained from a larg^ number of these glands readily con-
verted starch into dextrose.

Concerning the digestive fluid of Nereis pelagica (a marine
species), Dr. L. Fredericq performed the following experi-
ments : — Sixty of these worms, which had been preserved in
alcohol for six months, were dried and pulverised. From the
pulverised mass the various aqueous extracts (neutral,
alkaline, and acid) were prepared. Fibrin was dissolved after
a few minutes in the alkaline extract ; at the end of a little
longer time in the neutral extract ; but remained intact for
many days in the acid extract. The liquid resulting from
the digestion gave distinctly the reactions of peptones with
copper sulphate and potash.

The same experiments repeated with fresh specimens of
Nereis gave the same results. The digestive power of the
alkaline extract is considerable ; for it can digest, in less
than two hours, a quantity of fibrin equal to the weight of
the worms employed in making the extract.

The Insecta and Arachnida.

We now proceed to the Insecta and Arachnida, and, as
examples of these two classes, we describe in detail the

92 PHYSIOLOGY OF THE INVERTEBRATA.

phyaioiogy of the alimentary canal in the Ortlu^ti'a, .
doptem, Ifi/nicnoptcra, and the Ai-nneina.

(a) The Orlhoptsra.—The alimentary canal of Slatta (tili»l
cockroach) ia very highly developed. The salivary ^landi
(Fig. 25, n and 6) of the cockroach are situated on each aide
of the cesophagus and crop, and extend posteriorly as far as
the abdomen. They are about one-third of an inch in
length, and composed of acini (Fig, 25, b). Accompanying
the glands are two salivary receptacles, one on cither side of

the crop, A quantity of the eecretion* was extracted by ;
crushing about sixty glands of cockroaches, which had been
recently killed. The secretion was alkaline to test-papers.
A portion of the secretion was added to a small quantity of
starch, which was converted into glucose in twelve minutes, j

* QiiHItbB, in I'ror. Jtog. iSoc. Edinh., vol. 14, p. 234; and Chtmkial Utta^M
ToL SI, p. 195-

PHYSIOLOGY OF THE INVERTEBRATA. 93

The presence of glacose was proved by the formation of red
cnproas oxide by the action of Fehling's solution.

Another portion of the secretion was distilled in a minia-
ture retort (made of glass tubing) with dilute sulphuric acid.
To the distillate ferric chloride was added, which produced a
red colour, indicating the presence of sulphocyanates.

The secretion of these glands yields a small quantity of
ash, which contains calcium phosphate.

The soluble ferment of this secretion may be isolated by
precipitating an infusion of the glands obtained from a large
number of these insects with dilute phosphoric acid, adding
lime-water, and filtering. The precipitate is then dissolved
in distilled water, and re-precipitated by alcohol. This
precipitate converts starch into glucose, but has no action
on fibrin ; in other words, it has a similar action to ptyalin
— ^the ferment of the saliva of the higher animals. It is
probable that in Blatta there are terminations of the nerves
in these salivary glands. It may be that these nerve-
endings affect the protoplasmic substance of the cells forming
the ferment, which has the property of converting starch into
glucose.

The crop of Blatta simply acts as a receptacle to store up
the rapidly swallowed food until time is afforded for the food
to be passed on to the true stomach.

The gizzard or proventriculus has been described in the
last chapter. It is considered by some to be an internal
masticatory apparatus, but M. Plateau* considers that the
proventriculus of Blatta acts simply as a strainer.

The chylific ventriculus may be termed the true stomach
of Blatta^ for it is probable that digestion is more active in
this than in any other part of the alimentary canal. It is
Imed with epithelium, and often contains peptones.

The pyloric C83ca, situated in front of the chylific ventri-

' * See his papers on the digestion in the Myriapoda, Insecta^ and
Arachnida, published in the Bulletin de VAcadimie Roy ale dea Sc'encea de
Be^gique, 1874-78.

PHYSIOLOGY or THE INVERTEBRATA.

cuius, liave been directly proved by the author* 1
pancreatic in function. The secretion from these cieca
into the chylific ventriculua, where digestion proceeds.

In the carnivorooa Lihdhila (the dragon-fly) there ia i

crop or gizzard, only the chylific ventrtculus is present; W

* Grifliths, in ftw. Ilo;/. Soc. Ediub., ta\. 14, p. 137,

PHYSIOLOGY OF THE JNVERTERRATA, 95

fluids within this organ are always slightly alkaline, and an
infusion of about twenty of these organs readily converted
starch into glucose, and digested fibrin.

(6) The Lepidoptera. — As an example of this important
order we describe the physiology of the alimentary canal of
the larva and imago of Pontia brasstccc (the large white
cabbage butterfly).

The alimentary canal of the larva (Fig. 26, a) agrees
closely with the general Lepidopterous tjrpe. The mouth
opens into a pharynx lined by a dark, firm cuticula, and into
the latter open two ducts from a pair of well-developed
salivary glands. These glands form elongated tubes, gra-
dually diminishing in diameter towai'ds the posterior ends.
The oesophagus is very narrow and short. It leads into a
long chylific stomach, which opens into a short duct. Behind
the stomach the intestine consists of four parts : first, a short,
constricted piece ; second, a dilated, oval division ; third, the
short rectum ; and fourth, the anal tube. The stomach has
an epithelium lining, which is thrown up into folds so as to
form imperfectly differentiated glandular follicles.

At the posterior end of the stomach are the Malpighian
tubules.

Fig. 26, B, represents the alimentary canal of the imago of
Pontia. The pharynx passes into a narrow, but long, oeso-
phagus leading to the crop or food receptacle.

This crop is entirely absent in the larval, but is developed
in the pupal stage. The stomach is much smaller than in
the larva, but its lining is also thrown up irto glandular
ioUicles. The posterior end of the stomach leads into a long
and peculiarly coiled small intestine. The intestine passes
into the wide terminal division, the rectum, from the front
end of which there is a curved blind caecum or pouch.

In the imago of Pontia there are also a pair of well-
developed salivary glands.

The secretion of the salivary glands is alkaline to test-
papers, and readily converts starch into glucose. It has,

96 PHYSIOLOGY OF THE INVERTEBRATA.

however, no action on fibrin. It contains aulphocyanatea,
proved by the red colour produced by ferric chloride with a
drop of the secretion. The stomach of both the larva and
imago contains glandular follicles. These secrete a dige^tire
fluid, which answers in every way to that of A Vertebral*
pancreas. The ilalpighian tubules are well-developed in the
imago, as well as in the larva of Fo7ilm. Their function ia
that of a renal organ, but this subject will be considered in
detail in our chapter on ejxretion. It may be stated in passing,
that according to Dr. B. T. Lowue, F.L.S,," the Malpighian
tubules of Calliphora erythrocephala (the blow-dy) are
"hepatic" in function. If by hejiatic he means that these
tubules have the function of a Vertebrate liver, his conclnsions
are erroneous, for neither biliary acids nor glycogen are present
in these tubules. Again, if Dr. Lowne means by " hepatic "
that they have a pancreatic function, this is also erroneous,
because these tubules do not yield any digestive ferment or
ferments. On the other hand, the Malpighian tubules of the
JHptira, including Call iphora, readily yield uric acid; and
there is little doubt that tl'.ey are physiologically the kidneys
of the animal; although, concerning their place of develop-
ment from the alimentary canal, ci& well aa from other
considerations, they are the homologues of heimtic organs
(liver).

((■) The Hymenoptcra. — The structure of the aliment
canal of Apis (the bee) has already been given. The h
stomach is furnished internally with small glandular follicle*,'
and by making an alkaline extract of the stomachs obtained
from a large number of bees (which had been kept for some
time without food), the extract contained a ferment which
hydrolyzes starch, and digests fibrin, although feebly. In
fact., it answei-s to the characteristic tests of trypsin or
pancreatin. An alcoholic extract of the bee's stomach does

•latom'j, Phi/notiigji, Moryhofoffg, anif Dtmlpprntut of tkt Blov-J^

PHYSIOLOGY OF THE INVERTEBRATA, 97

not contain the smallest trace of biliary acids, pigments, or
glycogen.

Dr. A. von Planta* has recently investigated the juice, or
the sticky substance, which the working bees store in the
cells of the larvaa of the queens, drones, and workers.
Leuckartf regarded it as the product of the true stomach
(see Rg. 8c) of the working bees, which they vomit into
the cells in the same way that honey is vomited from the
honey-bag (see Pig. 86). Fisher and others regarded it as
the product of the salivary glands of the bees. Sclionfeld
has more recently shown that Leuckart's original vi«'w is the
correct one. He showed that the saliva can be t^asily
obtained from the salivary glands of the head and thorax,
and that it is very different from the food-juice de]y)sited
in the cells by the bees; and that, moreover, the juice is
similar, both chemically and microscopically, to the contents
of the bee's true stomach ; he showed also, from the
consideration of certain anatomical and physiological pecu-
liarities of the bee, such as the position of the moutli, the
inability of the bee to spit, &c., that the view of this
substance being saliva is quite untenable. (Jertain observers
have to this replied, that a bee cannot vomit the contents of
its true stomach, because of a ijolvt which intervenes between
it and the honey-stomach or bag (see Fig. 80 ; but Schonfeld
has shown that the structure, mistaken for a valve, has not
the function of one, but is in reality an internal mouth, over
which the animal has voluntary control, and by means of
which it is able to eat and drink the contents of the honey-
stomach when necessity or inclination arises. By light
pressure on the stomach, and stretching out the animal's
neck, the contents of the stomach can be easily pressed out.

Dr. A. von Planta's investigations entirely confirm Sch5n-
feld's view, that the food-juice comes from the bee's true
^mach. The subject was investigated from the point of

* ZeUtckrift Fhy^ioL ChemU, vol. I2, p. 327.
t DeuUehe Bienenzeitwt^f, 1854-5.

t)S PHYSIOLOGY OF THE IXVERTEBRATA.

view of its chemical composition, and care, also, was taken to
investigate, individually, t!ie juice eis occurring in the ceUs
of three VRrieties of bees— queens, drones, and workers.

Kome preliminaiy microscopicnl examinations of this snb-
stance yielded the followinf^ results, which nre qnite in accord
with the subsequent chemical analyses : —

(l) The food of the queen-bee larvBO is the same during the
whole of the larval period ; it is free from pollen grains, whidi
have been reduced to a thickieh but homogeneous juice by the
digestive action of the bee's stomach.

[z) The food of the larval drones is also, during the firrt
four days 'if tlie larval period, free from [xillen, and appeare
to have Ix'en coTnpletely digested previously. After four days
their food is rich in jmllen grains, which have, however, under-
gone a certain amount of digestion. The food-stuff of tic
larvro is probably formed from bee-bread.

The following table gives the average percentages obtained
from several analyaes : —

Pf miliar

DrODHOT

NCBttTKOr

Wortteg.llMt

71.63 %

Total «oU(l8 ....

30.62 ..

Nitrogenous matter

45- '4..

43.79 ..

Si.ai „

In the

F... . . .

"3-SS"

8.32 .,

«.S4.

Bollds

Glucose .

ao.39..

*4.o3 „

■7.65..

Aah. . . .

4.06 „

^".,

}

All these food-stuffa are rich in nitrogen ; all were of a
greyish white colour; and that of the queen-bee waa the
stickiest, wliile that of the working-bees was the most fluid.
The greater part of the nitrogenous matter of thefood was
proteid. The sugar present was always invert-sugar, whereas
the sugar in ]>ollen grains is invariably sucrose.

PHYSIOLOGY OF THE INVERTEBRATA. 99

The preceding table shows certain differences in the compo-
sition of the different kinds of larval food, more especially in
the composition of the solids present. Its composition is,
moreover, quit« different from that of the bee's saliva, which
contains no sugar. The difference between the proportional
amount of the different solids present in the different forms
of larval food is a constant one, and no doubt this variation
has in view the particular requirements of the larv» in
question. Certain small but constant differences were also
observed in the chemical composition of the food of the
larval drones during the first four days and at subsequent
periods.

Not only is there a difference in the quality, but there is
also one in the quantity of the food supplied. The juice
from lOO queen-bee cells yielded 3.6028 grammes of dry
matter, that from 100 drones' cells 0.2612 gramme, and that
from 100 workers' cells, 0.0474 gramme.

(d) The Araneimi. — As the spider's web has indirectly to
do with digestion a few remarks on the subject may not be
out of place. There is no doubt that **one of the most
characteristic organs of the Araneina is the arachnidium, or
apparatus by which the fine silky threads which constitute
'the web are produced. H. Meckel,* who has fully described
this apparatus as it occurs in Epeira diadeTiia, states that, in
the adult, more than a thousand glands, with separate
excretory ducts, secrete the viscid material, which, when
exposed to the air, hardens into silk. These glands are
divisible into five different kinds, and their ducts ultimately
enter the six prominent arachnidial mammillse, which, in this
species, project from the hinder end of the abdomen. Their
terminal fences are truncated, forming an area beset with the
minute arachnidial papillso by which the secretion of the
glands is poured out."

The secretion of these glands is insoluble in water, and has
a nitrogenous basis. Web-spinning has several objects in

* MQXUr*$ Archiv, 1846.

loo PHYSIOLOGY OF THE INVERJKBR.ITA.

vitw ; ( I J it ia a means by which the spider obtains a livelihood ;
(2) it is subservient to jtropagatiou of the species * — the silk
being used as a cocoon for the reception of e^s, a nest for
the young, as well as forming at-ranautic gossamer lines for
the dispersioii of the young brood on tlie approach of
maturity; (3) in the genns HyilnK-luii' (Iwlonging to the
Acariiia) it serves to attach the moulting individual to mi
aquatic plant by the anterior part of the body, when it
struggles to ivithdraw itself from its exuvium ; (4) it forniB »
home for the spider.

The secretion of the salivary glands of Tryc/i
(the common house- spider) contains a diastafcic ferment i
solphocyanates. These were proved by the t^sts previonaly

it torniB »

ncnt au^H

The so-called "liver ducts" of T'ynuwiu ihiint^iea bare
been investigated by Mr. A. Johnstone, F.G,S.,t and the
author.J with the following results : —

When examined microscopically these ducts are seen to
consist of cellular tissue ; and the secretion is poured into the
int«stine. The secretion obtained from a lai-ge number of
aniuials, as well as an extract made of the intestines of a rei
large number of spiders, gave the following reactions :-

(i) The secretion and extract form emulsions with neni
oils, yielding subsequently fatty acids and glycerol.

(2j ITie secretion and extract decompose stearin with
formation of stearic acid and glycerol : —

Ci,H,„0„ + 3H,0 = 3C,.H„0, + l-',II,0,.

(3) The secretion and exti-act act upon starch paste with
the formation of dextrose. The presence of dextrose was
proved by the formation of red cuprons oxide with Pehling'a
solution.

(4) The secretion and extract dissolve coagulated albomin
with the formation of peptones, which are readily

• See Dr. H. C. McCook's American Splderf ,tml ihr.r Spi„~i«g IFw*. i
■f DeraoDslTstor in Geology in the University of EdiobuTgh.

t Pratrilioslof Koyid Socittjiof E<Jinl,tiriih.'.-o\.il,\'>. lij.

rof

PHYSIOLOGY OF THE INVERTEBRATA, loi

by the rose colour produced in the cold by potash and copper
sulphate.

(5) Tannic acid produces a white precipitate with the sec-
retion.

(6) When a few drops of the secretion of these ducts were
examined chemico-microscopically, the following reactions
were obser7ed : on running in a solution of iodine (in potas-
siam iodide) between the slide and cover-glass, a brown de-
posit was obtained; and on running in concentrated nitric
acid, on another slide containing the secretion, yellow xantho-
proteic acid was formed. These reactions prove the presence
of albumin in the secretion of the organ in question. The
presence of albumin was further confirmed by the tests of
Palm.*

(7) The soluble ferment, or enzyme, secreted by the cellular
tubes was extracted, although with some difficulty, by the
Wittich-Kistiakowsky method. This ferment converts fibrin
into leucin and tyrosin.

(8) The albumins in the secretion and extract are not
converted into taurocholic or glycocholic acids, for not the
slightest traces of these biliary acids could be detected by the
Pettenkofer and other tests.

(9) The secretion contains approximately four per cent, of
solids. The slight residue (solids), which contains some com-
bination of sodium, effervesced on the addition of dilute acid.

(10) No glycogen was found in the secretion or extract.
From these investigations, which have been repeated on

several occasions, the so-called liver of the Araneiixa is proved
to have a similar function to the pancreas of the Vertebrata,

The Crustacea.

(l) The Brnchyitra. — As a type of this order, the alimentary
canal of Caitinus moe^ws will be considered in detail.

This animal is a voracious feeder ; its food consists of

* 2eiUcftrift fUr AnalytMie Chemle, vol. 24, pt. i.

I03 PHYSIOLOGY OF THE INVERTEBKATA. ■

animal and vegetable substances. These contain albuuiinoid|^|
fatty and starchy matters, and earthy salts, Tlie food is toi^f
to pieces by means of the chelre. The wide and sliort cesofl
phagns leads into a large globular stomach containing chi-
tinons teeth, the object of these teeth being to sub-divide
the food so that it may be acted upon by the digestive fluid
poured into the intestine. The only lateral appendage of the
alimentary canal of CairAiiii-s is the so-called liver. It is an
organ of considerable size, and consists of two symmetrical
haJves. Its secretion has the following reactions : —

It decomposes fats and oils with the forroatiou of glycMol
and fatty acids. It converts starch into de.vtrose, and dis-
solves albumin. The action of the secretion upon milk is to
render it transparent. The secretion contains leucin and
tyrosin, no doubt produced by the metamorphoses of certain
albuminous substances. In the words of Prof. M. Foster,
F.R.S.,' " one result of the action of the piimrentw juitx \b
the formation of considerable quantities of leucin aod
tyrosin," These organic compounds are not formed in a livi
for they are " dehydrated in a trw liver, forming a i
of cyanhydrins or cyanalcohols attached to a benzene nuclei
which then pass into the circulation."

The principal mineral ingredient found in the ashefi (ind
crated at a low temperature) of the so-called liver of G"Tt
was sodium carbonate. In the ash of a Vertebrate liver the
chief mineral constituents are potassium and phosphoric acid.

The soluble ferment is readily extracted by the Witticli-
Kistiakowsky method, or by the method recently introdaced
by Dr. N. Kravkotf.t This method consists in precipitating
the soluble ferments and albuminoids by means of ammoninm
sulphate. By treatment with alcohol, the albumuioids become
insoluble, and the ferments are then exti-acted with water.
The ferment so extracted converts fibrin info leucin i
tyrosin ; as well aa hydrolyzes starch.

• 7Vj(-tooi nf Phj/iiotogi/. (4th ed. ), 438.
t Jouraal of Rafian Clifmical Siiricln. 18

info leucin ao^H

PHYSIOLOGY OF THE INVERTEBRATA. 103

The secretion of the so-called liver of Carciniui does not
contain glycocholic and taorocholic acidsi or glycogen*

By naing the methods of M. Zaleski* for ascertaining the
presence of ferrous, ferric, and ferrosoferric compounds in a
true liver, the author of the present volume could not detect
the presence of iron in the organ or its secretion.

From the above reactions the conclusion to be drawn is,
that this bilobed organ is essentially pancreatic in function.!

The Macroura*

The general details of the alimentary canal of Adncics have
been described in the last chapter. The principal organs are
the stomach and the ** liver."

The gastric juice of the crayfish has recently been investi-
gated by M. Stamati.:^ ^7 means of a gastric fistula, the
gastric juice can be easily collected from the crayfish. This
secretion is of a yellowish colour, somewhat opalescent, and
alkaline to test-papers. It digests fibrin, rapidly forming
peptones which give the ordinary reactions : it also transforms
starch into glucose. It appears also that fats are emulsified
and fatty acids liberated. This so-called gastric juice of M.
Stamati was in fact nothing more than the secretion of the
" liver," which pours its secretion into the anterior part of
the intestine, and no doubt finds its way into the pyloric
portion of the crayfish's stomach. After the stomach of
Astftats has been thoroughly washed out with water, an
extract of the organ does not digest fibrin, nor does it act upon
starch. This proves that Stamati's gastric juice was in reality
the secretion of the " liver."

The so-called liver of Adacits fiuinatUvi has been proved
by the author § to be pancreatic in function. Its secretion

* ZeiUehriftJUr Physiologische Chemie, vol. 10, pp. 453-502.

t Dr. A. B. Griffiths' paper in Proc Hoy. Soc, Edin., vol. 16, p. 178.

X Comptea Rendus de la Sociiti BioUnfique, [2], t. 5, p. 16.

§ Griffiths* paper in Proe, Roy. /Soc, Ediiu, vol. 14, p. 237.

104 rHYSiOLOCY OF THE INVERTEBRATA.

oontains about five jier cent, of solids, and readily digerts
fibrin and hydrolyzee starch.

Similar reactions to the above are atso produced by the
so-called livers o^ Hmn-anis &ad Paianuni . There is no dout)fc—
that the " liver " of the Marroura ia a true pancreas. ■

The Lamellibranchiatj. ■

Dr. Ijeon Fredericc^ has investigated the alimentary canal
oi Mffn iiii'Jim-ui (eee t'ig, i8) and Mi/IUvji nfuiis (the mnssel).
The secretions of the 'so-called livers of these two animals
digest fibrin analogous to the pancreas of higher forms.*
When neutral and alkaline extracts of the organ are prepared,
they have the characteristic reactions already gi\ en nnder thi
head of I'lirriiitix monax; but IVedericq states that he bat
extracted glycogen from the secretion of the '■ liver " of JlfySil
It is. liowever, probable that glycogen is only present in]
this organ and other tissues of Mj/n during certain periods I
of growtli. It may be remarked that in Carcinvx, whe]
development is achieved by sudden bounds — by monlti
the '■ liver " contains glycogen during these periods of rapi
growth, but at other times there is not the slightest trace of'
the cni-bohydrate in that organ or any part' of the alimentanr

The contents of the digestive canal of Mac ai-e acid. This
acid is chlorohydric acid, and is found cliiefly in fluids obtaiaed 1
from the stomach. It is possible that the function of Um j
Btomach, as a .separate digestive organ, becomes more diffeii- |
entiated in the Lami-llihrdne/iiata . If- it jxissible that it giw I
rise to n secri'tion similar to the gastric juice of hi^ei
forms V

The so-called liver of Oxlreii, Priiai, Anmhnifa. and Ciiniim
functionates as a true pancreas.

Dr. r, A. MacJJnnnt has extracted ent^rochlorophyll froni

• /Vr. /(«.v. Soe. Eihn.
t mioti-iAieai TraH"n

vol. 14, p. J37.

PHYSIOLOGY OF THE INVERTEBRATA. 105

the " liver " pigments of certain genera of the Mollusfa, as
well as from a large number of other Invertebrates. Among
the MMusca experimented on were — Mytilus^ Ostrea, Ano-
daniay Cardium, Unto, Octopu,% Buc/iinwn, Patella^ Helix, and
Liinax. In some Molloscs — as Patella — the ** liver " contains
enterohsematin besides enterochlorophyll. It might be
snggested in reference to the discovery by Fredericq of
glycogen (C^HioOi) in the " liver " of Mya that it was ])ro-
dnced by the enterochlorophyll present in the organ ; as
enterochlorophyll is allied to chlorophyll. But MacMunn
(loc. cU,j p. 257) states that he has made '* various sections of
Invertebrate * livers ' obtained from animals feeding and fast-
ing, but never obtained a trace of starch (CgH,yOi) or cellulose
with iodine in iodide of potassium. Schulze's fluid, or with
iodine and sulphuric acid. These experiments were made
on the 'livers' of Helh) aspcrrn^ A^unfcrnta a/f/nm, Patella
Vulgate, Odrea ediUiSy MytHus ednlis, A^tavns JinviatUh, the
cseca of star flshes, &c. The precautions recommended by
Geddes* of previously digesting the tissues in alcohol, and in
caustic potash, and neutralising with acetic acid, having been
adopted in each case."

It appears that the '' enterochlorophyll occurs dissolved in
oil globules, also in granular form, and sometimes dissolved
in the protoplasm of the secreting cells of the ' liver.' " The
probable function of this and other pigments will be alluded
to in a subsequent chapter.

Thk Gasteropoda.

The secretion of the salivary glands of Helir asjtcrm has
been examined by the author.f It contains a ferment which
converts starch into glucose. The ferric chloride test failed
to show the presence of sulphocyanates. The mineral ingre-
dients found were calcium and chlorine ; but no phosphates

* iVof. Hoy. *Soc. Ed in., vol. 1 1, p. 377.
t Ihiil, vol. 14, p. 235.

io6

PHYSIOLOGY OF THE ISVERTEBRATA.

or carbonates could bo detected in the salivary glands of H<\%
Similar results have been obtained with the salivary glands

o( Lirn't.cjtiicm, and Livutx 7iuu-imas.

The so-called livers of ffdir iisprrsii, /.imnj; Jtaviis, and
Liviiix 'tiuudiiiiut are pancreatic in fuuction.

Dr. M. Levy" haa recently carefully examined the so-called
liver of HdU }>(rmHtit(. The weight of its organic conetitaents
is very constant, being the same in sammer and winter, and
in great measure they are the same in kind in all periods of
the year. The alcoholic extract of the gland when examined
by the spectroscope gave the spectrum of eiiterochlorophyll.
The digestive ferments present are a diastatic, a pi-plic. but
not a tryptie one. The peptic ferment appears to be iden- J
tical with the late Dr. Krukenberg's helicopepsin. Tbel
diastatic ferment disappears during the winter sleep ; it ia^
capable of digesting raw starch, hut lias no action on cellnloBe.
A fat emulsifying action is shown by the secretion in the
sauimer-time, but this also disappears during hibernatiou.

The ferment, by means of which this action is bronght
about, is not identical with the one described by Dr. Schmiede-
bergt as histozyuie. Histozyme, which was separated from
pigs' kidneys, is concerned in the splitting up of hippnric
acid. The suail's ferment has no such action. According to
Dr. Levy, glycogen with sinistiiu is generally pri'seot in the
organ, bnt all tests for h'di' gave a negativi- result. Jeoc
was also absent. Dr. Levy has separated the following s
stances from the so-called liver of Hrii-' j"'iiii'/ut :—

Locilhin

Oleic acid

n the alcohglic ejttract

Fatty acids

1 Chlorine

Ash ] Phosphoric acid

t SQlphndc acid.

n the ethereal

xtract

A trace of fat.

• Z.,t.

JJiol., vol.

'7. P- 398-

t Arch

0. j;.-,.r.

FMh. un,lJ'!m.-::. y<^i. 14.

PHYSIOLOGY OF THE INVERTEBRATA, 107

In the aqueous extract

/Sugar
Globulin (coagulating at 66" C.)
Glycogen
Sinistrin
Hypoxanthine*

f Potassium
Sodium
Calcium
Magnesium
Ash ( Iron (traces)
Manganese
Chlorine
Phosphoric acid
\ V Sulphuric acid.

In winter animals, silica was also found as an ash con-
Btitnent.

Dr. Fredericq has investigated the nature of the secretions
of the salivary glands and "liver "of Arimi rnfiin. The
secretion of the salivary glands readily acts upon starcli, but
has no action upon fibrin and neutral oila The secretion of
the "liver" is a brown liquid, and can be collected in a
safficiently large quantity by killing a large number of fresh
snails. It suflSces to dissect them lengthways to extract the
viscera, and to collect the liquid which flows from the cut end
of the intestine. If the secretion is extracted after the ani-
mals have just been feeding, it is most likely that the secretion
wiD be slightly acid (acidity due to food) ; in that case the
digestion of fibrin takes about twenty-four hours. On the
other hand, if the secretion is extracted when alkaline, or if
the acid secretion is rendered slightly alkaline by a small
quantity of sodium carbonate, its activity is greatly increased.
In an acid solution the ferment is inactive, and this is readily
observed when a small quantity of acidulated water is added
to the digestive fluid of the snail, for it completely stops the
digestion of fibrin.

The " liver " and its secretion furnish a diastatic f eiinent
transforming starchy matters into glucose. The so-called

* And other bases precipitablc by phosphotungstic acid.

108 I'HYSJOLOiiY OF THE INVERTEBRATA.

liver of Arum ruj'm, as wfU as ITrlii; is a digestive gland
wliich is comparable to the pancreas of the Vn-l^brato. It
contains Dcitht-r bilinry pigments nor biliary acide. If one
considers that the \'ertpbratf liver is not- a digestive gland in
tht- proper sense of the word, since neither bile nor an infusion
of hepatic- ti&sat-s contains digestive ferments, we may conclude
that tlie nnme of livei- is in no way applicable to the digi
tive gland of the Gndcropodo.

It in Btttti-d by Barfartii that the liver of the Gader
performs the functions of a hepato-pancreas. It is cert«i
pancreatic in function ; but then- are no cliemico-phyBio
logical reasons foi' saying that, it also possesses a he]
function.

The saliviirj- glands and "liver" of Patella vuUjatn bftv^
been investigated by the author." The limpet (P. vttlgnta),
witli its conical shell adhering to the rocks of our coasts, is
well known to everj' sea-side wanderer. This member of the
GinUfiVfKHf'i, has been tlie subject, of many scientific memoirs
in ancient and niotlem times. Amongst naturalists, Aristotle
was the eariieai who gave an account of some of the Umpet's
liabits, and ('u\ier was t)ie first to describe its anatomy.
Altlioiigh this interesting little animal has attracted the
attoution of uiaiiy naturalists, it is only within the last
divaile Ihnt the tnie functions of its internal oi^ans have
bwD sati»fnclorily worked out.

Ilir " liwr " of l\tltlln ruJifntn is« yellowish saocnlar gland,
uhI lh4^ gn^alor Imlk of this organ is encircled by the saper^
ticml ci^l oTthe inlf^ttne. Ita SKretioa acts upon stanh-
ifiuX* cmtxvrhng lh« Miurch into gtoooae. as |M<oved by
iVhlinit's solutHVt. The aactvtMn, as w«iU as Uie organ its«lf
pRxInctM aa Muul^ioo with iiib and fads, yM£]^ aofaseqaently
I^IjxwmI mhI Ulty WMtsk 1V> stJaUe Urmm% wcireted by
iW OdtwHWir <y4U vt ihm <f«ttmliuB of tke gbad is readilj-
«xtaKlM I9 fMwr (W Wlnicb-Kiatbkowd^ or KrarkofF
«.«at.4^p.3gat

PHYSIOLOGY OF THE LWKRTEBRATA,

109

methods. The isolated ferment, as well as the organ and its
secretion, digest fibrin.

Neither the organ nor its secretion contains biliary acids or
glycogen. From these investigations th(^re is no doubt that
the so-called liver of Patella vulgata is similar in function to
the pancreas of the Vertebrate division of animal life.

The two salivary glands of Putclln are well-marked, and
situated anteriorly to the pharynx, lying beneath the pericar-
dium on one side and the renal and anal papilla? on the other.
They are of a yellowish-brown colour, and give oif four ductg.
The secretion of these glands was examined by the same
method applied to the salivary glands of Srplff offirhitilis (see
later in this chapter), and with similar i*esults.

The following table represents the constituents found in
the salivary secretions of the two orders of the Mitlhaua : —

+ — Present. — = Absent.

Soluble diastatic ferment
Mucin

Snlphocjaiiates
Calcium phosphate
Caloinm .
Cblorine .

Cephalopoda.
DIbraoehlata.

4-
+
4-
+
?

<iaMteropoda.

Piiliuofraatero- . BranohiovaM.
IKxla. ' toropodo.

■r

}
?

The "liver" and salivary glands of Bwcinum (whelk)
have similar functions as the same organs in Patdla.

The Cephalopoda.

In a memoir published in the Clwniiad Ncws^ vol. 48,
page 37, and the Journal of the Chemical SociHy, 1884,
page 94, the author gave an account of a peculiar excretory

no I'HYSIOLDCY OF THE INVBRTEBRATA.

pi-oduct found in the Sepia's "liver." This product ":i-
proved to be albumin in psfcdo-crystalline ^gregations whin
fxamiued under the microscupe. These bodies are not of -^
constant occurrence in thia organ of Sjjirt ojirhiilis.

Two years after the publication of the above-men tiocf J
memoir the author • made a, tliorough examination of this
organ in Si-pi" which substantiated and extended the obserw-
tiona of Krakenberg,t Fredericq.J ^^^^ Jousset de Bellesroe.f

Aft«r carefully dissecting the organ out of the cavity o£
the body of a fresh Srjn'-i., the following experimenta were
perfomied : —

fi) A small portion of the organ was placed on starct*^
paste. The starch grannies disappeared, with the exceptic***
of the celluloid covering, and on treating with water,
testing th<' solution with Fehling's solution, sugar in tfc^^
dextrose form was found.

(2) Tlie organ gave an akaline reaction to litmus paper.

(3) When a small portion of the organ was agitated witt^
a. smail (juantity of oil, an emulsion was produced — thL.^
emulsioti had first an alkaline reaction, and after some tim*-
becanie acid, owing to the formation of butyrio and other'
acids of the fatty series.

(■4) The action of it on milk was to render the milk trans^ —
parent in fi>ur hours ; 1 5 cc, of milk were rendered
parent by 6 milligrammes of the organ.

(5) A chemico-microscopical examination of tlie
of the organ revealed the presence of albumin

Tlu Ixntition, of t-hi: Fermait. — The process used to obtain
tlie ferment or ferments (in a crude state) from the secretion
of the organ was that devised by Wittich and oped
Kistiakowskyli in his researches on pancreatic

• Prtirreiliiig4 of Itoi/ai fixieli/ n/ /■J-h'nljarnli, val. 13,
t IJidertatk. Fhytio'. !n»U Hn.hll^rfi. Bd, 1, p. 317 (1H78].
J BW/. Aftil. Samn-fi llrlfli'iuf, tcime 56, p. 761 [1878J ;
Sarnet', t. 3. p. 163 (1879].

i f'.,.„,rfr. lUmtM, t. 88, pp. 304, 428 (i879l-

n I'/lii'jry't Arehiv. file Ph<,i<lologir, vol. 9, p. 438.

red tTHD^^
I secntaH

the secretion
md oiied fa^H
ic fermen^^l

PHYSIOLOGY OF THE INVERTEBRATA, in

The process consists in hardening the organ in alcohol for
three days, and then catting it np into very small pieces, ex-
tracting with glycerol and filtering.

On the addition of alcohol to the filtrate, the ferment is
precipitated.

The action of this ferment or ferments on starch was the
complete conversion of the latter into dextrose or right-
handed glucose, which was proved by the action of Fehling's
solution ; and the formation of crystals (CgHijOg NaCl, H,0)
with a solution of sodium chloride, a distinction from
levuloae or left-handed glucose, which does not form these
crystals with sodium chloride solution. The action of the
ferment on fibrin was the formation of leucin (^^- amido-
caproic acid, CgHisNO,) and tyrosin (paraoxyphenylamido-
propionic acid, C^HnNOs); for on treating the fermented
mass with hot water and filtering, a solution is obtained
which contains leucin and tyrosin. When acetic acid was
added to this solution, acicular crystals were deposited.
These crystals are insoluble in ether, but soluble in boiling
water. The aqueous solution produced a red flocculent pre-
cipitate on the addition of a neutral solution of mercuric
nitrate ; this reaction is characteristic of tyrosin.

The acetic acid solution, after precipitating the tyrosin,
^as evaporated, when leucin was deposited in white shining
plates, which melt at 98° C. These crystals of leucin were

beated with barium oxide, the result of the action being the

formation of amylamine and carbon dioxide : —

CeH„NO, = N(C,H„)H. + CO,
By digesting the organ itself with boiling water and

filtering, the filtrate contained leucin and tyrosin. The

f eiment has no action on cellulose.

From these investigations, the so-called liver of Sepia

^iffkincdis is proved to be a pancreas, for the juices of the organ
^^x^ purely digestive in function, digesting starch, oil, and
^milar bodies, and transforming fibrin into leucin and tyrosin.
'l^en, again, albumin is present in its secretion, which is

113 PHYSIOLOGY 01- THE INVERTEBKATA. ,

characteristic of the pancreatic fluid of the higher amm&ls—
no albumiii being found in the liver, for nlbiiminoids ore
decomposed by that organ. No glycocholic auJ taurocholio
acids or glycogen were obtained from the organ. Not the
slightest trace of these biliary conipoundB could be detected
in the organ or its secretion.

There is no doubt that theae inveBtigations prove that this
so-called liver of the C'lpkitloiniilH. is a true pancreas or
digestive organ.

The author in his paper entitled, " Further Researches on
the Physiology of the luvertebrata."" gave the following |
account of the salivary glauds of the cuttle-tish : There
two pairs of salivary glands in A'pia offi<-inidin. The posterior
pair, which an- the lai^er (see Fig. 20) lie on either side o'
the (.esophagus. The secretion of the posterior glands **■
poured into the assophagus, while the secretion of the smallc" ^
anterior pair of glands passes directly into the buccal carity' ■
A (jiiantity of the secretion was extracted by using severe
freshly-killed cutlle-fishea. It was alkaline to test-paper^'
A portion of the secretion was added to a small quantity o-^
starch, the starch being converted into glucose in fifteiec*
minutes. The presence of glucose waa proved by tin '
formation of red cuprous oxide by the action of Fehling'*
solution. The soluble enzyme, or ferment, contained in th^
secretion fwhich is capable of causing tlie hydration o^ng
starchy, was isolated by precipitating the secretion witj|^|
dilute normal phosphoric acid, adding lime-water and then^H
filtering. The precipitate produced was dissolved in distilled
water and ivprecipitated by alcohol. This precipitate converts
starch into glucose.

When a drop of thi' clear secretion was allowed to laU>V
into ft beaker containing dilute acetic acid, stringy flakes rfj
TRiu-iii were easily obtained. The presence of mucin '
confirmed by several well-known tests.

Another ^xirtiou of the secretion was distilled (with tiie I

• Peo^cniiiigi of Jlo'jal •Socicly of Loii-lon , vol. 44, (i. J17.

PHYSIOLOGY OF THE INVERTEBRATA. 113

utmost care) with dilute sulphuric acid, and to the distillate
ferric chloride solution was added, which gave a red colour,
indicating the presence of sulphocyanates.

The inorganic constituents, as far as the author could
make out, consisted only of calcium phosphate. No calcium
carbonate could be detected.

There is much in favour of the supposition that the
diastatic ferment in these secretions is produced as the result
of the action of nerve-fibres (from the inferior buccal gan-
glion) upon the protoplasm of the epithelial cells of the
glands.

The Tunicata.

The veiy fine, branched, and ampullated tubules (sometimes
known as Savigny's tubules), ramifying over the wall of the
intestine in nearly all the Tunicata, form a digestive gland,
which is certainly pancreatic in function. The common duct
of this gland opens into the stomach. The latter organ
always contains a secretion having similar chemical properties
to those produced by the pancreatic tubules.

The two following tables summarise our studies of the
salivary glands and the so-called livers of the Inverte-
hata: —

114

PHYSIOLOGY OF THE INVERTEBRATA.

poda.

+ +

''^

1
1

+ +

-r -r

•T4

Cii

e-«

e- +

Sri

•

55 *:

■

GLA
Absen

■<

>^ II

"S.

% '

<« a

9
a*

_ __^ 1

SAI
resei

Pui

» II

•a

••*

* 4.

^.^

k«

-*- +

+ <>•

^►^

1 _ _-

•

• •

•

•
00

J ■

•

-a

a s

5 .2

0 0

•n

3 g

0 0

-a -a

PHYSIOLOGY OF THE INVERTEBRATA.

i
II

§; §

C/}

-ti)«d{iinX

+ +

«'«podaia;at{)

+ + +

-muqilfaaiwq

*vnaxM]f

*«inXq9U{i

+ + +

*va|9izuv

+ +

*«aa)doii8aiXH : + +

'Bjaidop{da^

'wMoqiiO

•»;«qooJiio

•«9ii]paiiH

*«»3II00f0q9|JX i

I I

'n«auapoaiq93

+ +

4.Mipodoiwido3 + + + + + -*■

+ + + + + +

-uflgpoa

+ +

Oh h3

p d

O O

3!>

o
o

.St:

<D.S

jq d

fl CO

« CO

"3 '2

Ii6 PHYSIOLOGY OF THE INVERTEBRATA.

TLe chief digestive glands o£ the Inrerlth-ntn are the
pancreas (the so-called liver) and the salivary glands. There
appears to be no organ, from the lowest to the highest'
Invertebrate animal, corresponding with the Vertebrate liver.
Dr. C Letourneau, in his Z" Biologic, says : " Does the
pancreas exist in the Invertebrates ? This is a question of
comparative physiology which still waits for a reply. We do
not begin clearly to recognise the pancreas except in fishes,
and then only in a rudimentarj' state." After the recent
researches of Krukenberg, Fredericq, Jonsset de Bellesme,
Plateau, Hoppe-Seyler, as well as those of the aothor, tha
problem now requiring solution is the following : — Does a
true lieer exist in the I?ii'i.-richivla ? The pancreas appears
to be the chief digestive organ of the earlier forms of animal
life.

On the other hand, some biologists look upon the Verte-
brate liver, pancreas, and salivary glands as differentiated
bodies of an original pancreas of the Tiiverlch-nia. But have
not many forms of the lower animals similar salivary glands
to those found in the VertAiTot" 1 And is not the Bo-called
liver of the hivci-tchTiiUi a true pancreas, capable of producing
the same chemical and physiological reactions as the pancreaa
of higher forms ?

CHAPTER V.
Absorption in the Invertebrata.

In Chapters III. and IV. the processes of digestion in the
Invertebrata were considered in detail. The digested food
becomes tissue ; but before this is attained the said digested
food, which is still enclosed in the alimentary canal (if
present), must first pass through its walls and gain
entrance into the blood or tissues. This process is known
as absorption.

The function of absorption in the Vertebrata is carried on
by a distinct set of vessels, but these are entirely wanting in
the Invertebrata. In the higher animals absorption takes
place partly in the stomach and partly in the intestine.
^' The mucous membrane of the stomach and intestine con-
tains an abundant supply of capillaries ; the walls of these
vessels are only one cell thick; consequently the soluble
peptones and sugar will diffuse readily into their interiors."
In the intestine the area of absorption is largely increased
by means of the villi in the Vertebrata, and by means of the
typhlosole in those Invertebrates whose intestine is provided
with such an arrangement.

There are no openings in the substance of the villi and
typhlosoles; consequently the nutritive fluids pass directly
through their substance by a kind of transudation or imbibi-
tion (endosmosis). Every animal membrane will absorb
certain fluids with greater or less facility. Thus most of
them will absorb pure water more abundantly than a solution
of sodium or potassium chloride ; or a solution of sugar more

ii« fflYSlOLOOY OF THE INVERTEBRATA.

readily than one of gum; and the aame liquid will be ab-^
sorbed more i-f adily by one membrane, and less so by othera^l
Thua every membrane has a special power of absorjition fw;
certain flnids, which it will take up in greater or smaller'
quantity, according to their nature and composition. In all!
cases, however, there is a natural limit to this quantity^
beyond which absoqjtion will not continue.

In the higher animals there is absorption by the blood-
vessels and Absorption by the lacteals ; but, as already stated,
there are no ilhiinEt vesseh in the Invrfchrritn set apart for
the function of absorption. In the lower Molliwu, Eekintt-
drnaoln, &x., the digested food is absorbed by the walls of
the alimentary canal. In the higher Afollasc" aaA Arthi-opoda,
thedigeated food ornutritive fluids are absorbed by the blood-
vessels in the walls of the alimentarj- canal. In both of the
above cases, the two functions of absorption and digestion ara
not completely differentiated from each other.

In the Iitrnifhmhi the digested food is brought into con-
tact or close relationship with the various tissues in three
ways:

(1) 1'he food particles fas in Avtaiixt), during the proc«ss
of digestion, are brought into contact with the tissues (using
the term in its widest sense), that are to be noiirislied or
renovated by them. In this case there is a fusion of the two
functions of absorption and digestion. The digested food
immediately becomes tissue.

(2) The digested food or nutritive fluid transudes throng
the walls of the alimentary canal into the somatic or body
cavity, and is consequently absorbed by the walls of, and the
organs suspended in, that cavity. In this case, the nutritive
fluid passes through a transitor}- condition, in such a state
being known as the " chytaqueous" fluid. The so-called
chylaijueous fluid is found in the body cavity, and is nev^
enclosed in any distinct vessels ; it undoubtedly represents
the blood of the higher animals.

(3) The digested food contained in the alimentary cantil

: PHYSIOLOGY OF THE INVERTEBRATA. 119

absorbed by the blood-vessels distributed on the walls of the
digestive system. Through the medium of blood-vessels the
products of digestion are carried to all parts of the body.
In this case there is a fusion of the functions of absorption
and circulation ; the products of digestion become incorpo-
rated with the blood ere they reach the tissues for which they
are destined.

Therefore, in the Invertebraia the function of absorption
does not exist as an entirely separate function, as one finds in
the Vertebrata, It is either fused with the function of
digestion or the function of circulation.

The Protozoa.

The Oreyarinulit, being parasitic organisms, pass their
existence in the chyle or nutritive fluid of the higher animals.
They absorb by the whole surface of their bodies the nutritive
fluids of their hosts ; such fluids are already in such a state
as to form a nutritive material for these low organisms.
Probably the nutritive material does not undergo any fur-
ther change after passing into the body of a ChregaHna,
*' Perhaps no other animals present such a complete want of
differentiation between the functions of digestion and ab-
sorption " as do the Gregarinula.

In the H/dzopodu (e,(/., A^mdxt) food is taken in at any
part of the cell, but only at one region of the cell at one given
time — i.(?., the whole surface of the cell can ingest food, but
only one portion of it ingests at a time. In these animals
the intimate contact of the food particles, absorbed within the
living substance, is aided by the contractions of the sarcode,
by the emission and retraction of the pseudopodia. The
sarcode of these organisms absorbs nutrient matter from the
food particles. There is no distinct channel through which
the food particles pass. What causes the sarcode to absorb
nutrient matter from the heterogeneous materials introduced
into the cells by the pseudopodia ? There is no doubt that

lao PHYSIOLOGY OF THE INVERTEBRATA.

it is due to the exdbability" or irritabilityt of the cell, caasi^
indirectly by the preBence of food particles.

Speaking of the Rhizopuda, M. Kiohet says that " irritability
is their life complete." TJie presence of food particles excit«
digestion and absorption, but only the digested particl»
are absorbed. This power of selection is possessed by tie
protoplasm of the cell ; it is a physiological property of
that complex subatance whose composition has already been'
alluded to in the early part of the work.

In the compound IiMx<rpodft . only cei-tain regions of the
sarcode take in food particles, '" The food so ingested paasee
through more or less of a compound H/iizopoda ui a similar
fashion to that met with in the simple forms."

In the In/iisorift the iood particles may possibly undergoi>
a preliminary digestion in the short o-sophagns ('•.(/. Para^
iiuecinm). After this the food gives rise to food vacuoles in
the sarcode. These food vacuoles undergo a rotator}- move-
ment round the cell, just below the euticular layer. " Only the
sarcode immediately in contact with the food vacuoles, as they
pass round, can be regarded as truly absorptive. Here Ib,
then, the first marking off of a region (ouly a region) of tHe
sarcode, whose work is that of absorbing nutrient msteriala
from the food, and transferring them to other parts of the
sarcodic body."

The POHIFERA.

In the Porifcrii the food particles, along with water, enter
through the inhalent apertures, and pass into the gastro-
vascular cavity, which is lined with flagellate cells ; but the
functions of digestion and absorption in the I'wifei-a do sofe
differ very much from those occurring in the liliizojioda.

THK CoilJ-lNTElUTA.
In the Hydroxoa the function of absorption is somewhat I

fl
r

PHYSIOLOGY OF THE INVERTEBRATA. 121

more complicated than in the Khiaopoda. The digestive
and somatic cavities are not differentiated, for they form one
common cavity. The digested food is absorbed by the cells
of the endoderm. In the Protozoa the function of absorption
is effected by the saroode, whereas in the Hydrozoa the
^^saroode" becomes differentiated into cellular membranes,
the internal one (endoderm), lining the digestive cavity.
The endoderm of the Hydrozoa is the absorptive layer
and is the means of transferring the absorbed fluids to the
ectoderm.

Although there are many points in the mode of absorption
in the Hydrozoa comparable to those of the Rhizopoda^
yet the former class marks a distinct advance on that of the
latter; for the food is first digested in the " chylaqueous "
fluid contained in the digestive and somatic cavity, whereas
in the Bhizopoda the food particles are brought into actual
contact with the sarcode, which })erforms both the functions
of digestion and absorption.

In the Actinozoa the function of absorption comes under
the second method already described. The digested food
transudes through the linings of the digestive cavity, or
passes directly through the posterior aperture into the somatic
cavity. The somatic cavity, which is distinct from the
digestive cavity,* contains a '* chylaqueous " fluid. This fluid
consists largely of water, and contains albuminoid spherules,
which are possibly the precursors of the white corpuscles of
chyle and of blood in the higher animals.

The nutrient matter of the digested food, having passed
into the somatic cavity, is absorbed by the endodermic cells
of that cavity and by the mesenteries.

The Echinodermata.

As far as the function of absorption in the JEchinoderniata
is concerned, there is very little difference from that of the

* In Actinozoa the digestive cavity is suspended in the somatic cavity.

laa PHYSIOU>i;v i>F THK INVERTEBRATA.

Ai-tiiwzoii. The alimentary canal, or tli»estn-e systpm, is sa»-
pended in the somatic cavity ; and the digested food traDsndes
through the walls of tJie Conner into the latter. The nutrient
fluid is then absorbed by the walls of the somatic cavity, as
well as by the various organs suspended therein. The soiDatic
or peritoneal cavity in the A^'-ritfru contains a watery oor-
pusciilated Huid, The corpuscles are nucleat-ed cells; this
Huid therefore represents the blood of the higher animals.

It will be noticed that in the Ar/.ittozryi, as well as in the
Erliinod'-rmntd . the fnnctiou of absorption is distinct &om
that of di^stion, but it is not performed by any special
organs.

Thi: Cestoidea. J

Aa already stated, the ('rsioulra are reversions to a lower oM
simpler type. They are immersed in the chyle or the tissnea
of the higher animals ; conBecjuentiy they absorb the digested
food, &c.. by the whole of the external surface. Although
these animals are mucli higher iu the zoological scale th^i
the Gref/crinidd^ there is in the functions of digestion and
absorption a close analogy between these two orders. In
both, the processes of absorption and digestion are
differentiated.

The Annelida.

.vil^

The digestive tube is suspended in the perivisceral cai
The digested food transudes into this cavity, and thstW
becomes mixed with a colourless corpuscnlat^-d fluid. This
fluid fills the perivisceral cavity, and is analogous to the blood
of other Invertebrates, This colourless fluid is not contained
iu any vessels, although there is in Lumbricns, for example, a
red fluid contained in a well -developed system of vessels, iu
addition to the colourless fluid already mentioned.

The nutrient matters, afler having passed into the
visceral cavity or chambers^ — as the perivisceral cavity
generally divided into chambers by means of thin musci

PHYSIOLOGY OF THE INVERTEBRATA. 123

mesenteries — are absorbed by the pseudo-lisemal vessels, as
well as by the various tissues, &c., suspended in the peri-
visceral cavity.

The Myriapoda and Insfxta.

In these two classes of the Inverteh^ata there is a distinct
advance, in the mode of absorption, on all the forms alluded
to in the present chapter.

Over the external surface of the alimentarj^ canal there are
distributed blood-vessels ; and the nutrient matter of the food
is chiefly absorbed by these vessels, and more especially by
those carrying venous blood. Here the digested food is
absorbed by distinct vessels, although there may be some
transudation directly into the somatic or body cavity,
especially in some of the lower orders of these two classes.

The vessels which absorb the digested food are not special
vessels (like the lymphatics of the Vertehrata) set apart for
the function of absorption, for they perform the ordinary func-
tion of veins, as well as *' carrying away from the tissues of the
alimentary canal the effete products resulting from the work
of those tissues. But in addition to this there is laid upon
them the office of receiving the fresh material introduced into
the system through the alimentary canal. These vessels are
not only transmitting blood, but are absorbing ' chyle ' ; there
is a fusion of the functions of absorption and circulation."

The Arachnida.

The function of absorption in this class is performed in a
similar manner to that of the Myriitpochi and hiscda. The
digested food passes into the veins, and is conveyed to the
dorsal vasiform heart.

The Crustacea.

The digested food passes from the intestine into the blood-
vessels or veins, which are distributed on its walls. No other

124 PHYSIOLOGY OF THE INVEKTEBRATA.

vessels are known to convey the digested food into the circu-
latory system " than the irregular venotis receptacles which
are in contact with the parietes of the intestine."

The Poi,yzoA and Buachiopoda.

The function of absorption in the Pdipoii and the Brachw-
pod<i is not so highly differentiated as the M'lni'pixfn , Insrda.
Ariichuidii, and Vrnsttuxa. In the latter, the digested f<iod
passes into vessels, or, in other words, into tlie circulatory
system ; bnt as there are no vessfis in the J'uhrzfx and Uie
UrachuijM^f'i, the function of absorption is analogous tc that of
the AcliiujMii. There is an alimentaiy c-anal suspended in a
somatic or body cavity. The digested fixid transudes through
the walls of the digestive system, and is then absorbed by the
external endodenu of the body cavity, as well as by the organ*
suspended therein. ^1

The MoLLti.scA. ^(

The function of ab8ori)tiou in the Mi-lhiKr" is placed under
the head of our third category'. The digested matter is
absorbed by vessels, but these pei-fonn the dual functions of
absorption and circulation.

Thei>' are no special absorbent vessels in tie Iin'crtthmt-i.
But although there is no special apparatus set apait for
absorption, the nutrient fluids, absorbed by either the sarcode,
somatic linings, or blood-vessels, are spread wherever they are
required, the distribution being in ^uie animals effected
slowly, in a way analogous to absorption. In others the
distribution of the nutrient lluids is accomplished rapidly
by the establishment of currents, which perve also to remove
the excretory products eliminated from the organs. This
originates another function, the cii-culation of the bloocl. and
another set nf organs by which this is performed.

CHAPTER VI.

The Blood in the Invehtkbrata.

In animals of the simplest structure all the fluids of
animal economy resemble one another. '^ It seems, indeed,
to be only water charged with a certain amount of organic
particles ; but in animals higher in the scale of being, the
humours cease to be of the same nature, and there is one,
distinct from all the others, destined to nourish the body ;
this fluid is the blood. It not only nourishes the body, but
is the source whence are drawn all the secretions, such as the
saUTE, urine, bile, and tears." In the Mammnlm^ Arcs,
Itrptilia, Amphibia^ Pisces, and in most of the Annelida, the
blood is of a red colour. But in the greater number of the
Invertebrata the blood presents various colours and densities,
being often thin or watery, and slightly yellow or green,
brown, rose-coloured, or lilac. The majority of the Inver-
iebrtUa have white blood ; eg,, the Insecta, Crustacea, Mol~
lu8ca» &c.

The blood of the Invertebrata, like that of the VeHehrata, is
not homogeneous, for it consists of a transparent or semi-trans-
parent liquid, and a number of small, solid corpuscles, which
float in this liquid.

In the higher animals the corpuscles are of two kinds, red
and colourless ; but in the InveHebrcUa there are, as a rule,
only colourless corpuscles. The red blood of Annelides is
different from the red blood of the Vertebrata, inasmuch as
the plasma is coloured, and the corpuscles are colourless in
the former, while in the latter the plasma is colourless.

Ij6

PHYSIOLOGY OF THE I.WERTERRATA.

nnd there are present coloured and colourless corpoacles.
The perivisceral Huid of the AinifUda is colourless, and
contains colourless nucleated corpuscles.

The cor|3usclea in the blood of the fmrrtrhratii are of
different sizes, and the size varies much in the same in-
dividual. The size of the corpuscles in the earthworm and
leech are aa follows : —

/jumfiricus

yf] iocb ii
-iW inch ii

and th^H
a variaufl
TP recenfi^^

Their form, however, is generally spherical ;
surface has a raspbeiTy api>earance.

In the higher Ini-ri-lcbrata the blood clots after a '
period of time.

Di-s. J. B. Haycraft and E. W. Cariier* have i
examined the coagulation of the blotid in certain forms of the
Inrcrfdmita. According to their investigations, "'in Inverte-
brate blood the clot is formed, at any rate for the greater
part, by the welding together of blood-corpuscles. These
throw out processes, which interlace to form a solid mass.''
Haycraft and Carlier have examined the blood of a crab and
a sea-urchin.

■' Crab's blood clots in about live minutes, when the opaque
pinkish fluid becomes water-clear, with a branching clot
within it. During and alter coagulation the clot becomes c
a brown-black colour, from the development within
corpuscles of a pigment."

" The blood of the sea-urchin varies very much in the
number of corpuscles present in the different specimens. In
most cases, when allowed to coagulate, the clot is very
small, and not easy to demonstrate in a few drops of blootl."

The blood of the higher Invertebrates generally darkens
rapidly on exposure to air. For example, Mr. E. B. Poalton„_
F.H,S..t has shown that the blood of Lepidopterc

■ I'foe, Hoy. Soc. EtUitb., vol, is, p. 423.

-""■^

erous lame aadtiii

PHYSIOLOGY OF THE INVERTEBRATA. 127

papas becomes black : and Dr. C. A. MacMunn * has shown
that the blood of Hdix po7)iatia assumes a blue tinge on ex-
posure to air.

Ck>nceming the composition and nature of the Invertebrate
blood generally, further remarks will be given later in this
chapter.

The Protozoa and Pokifeka.

These animals are without blood, for no part of the sarcode
can be regarded as blood. The sarcodic substance lining the
canals, which traverse the skeleton of the Forifcra, is also
devoid of any fluid analogous to the blood of the higher
Inverteb^rata.

In some of the Cestoidea and allied forms the blood or
nutritive fluid found '' in those interstices of the mesoderm
that represent the somatic cavity of other animals, is said to
be free from corpuscles." The simplest form of Invertebrate
blood is present in the Nematoidea.

In the Polyzoa the fluid contained in the perivisceral cavity
consists largely of water, and has but few, if any, corpuscles.
This nutritive fluid (the chylaqueous fluid of some writers),
derived in the first instance from the food that has been
digested in the alimentary canal, and which has transuded
through the walls of that canal, is, without doubt, analogous
to the blood of higher forms.

In the Hydrozoa, which are provided with blood, the blood
is of a very watery nature. The amount of fibrin is extremely
small; consequently the fluid is nou-coagulable, and it is
almost devoid of corpuscles. That the so-called chylaqueous
fluid is analogous to the blood of higher forms is demonstrated
by the fact that the perivisceral fluid of the Annelidit yields
on investigation '^ not only albumin and fibrin, but crystals
which are derived from the water that constitutes so large a
part of the nutritive fluid."

From the above remarks it will be observed that the blood

* QuarUrly J<mrnal of ificroaeopicaf ScUncCf 1885.

138 PHYSIOLOGY OF THE INVERTEBRATA

of many of the Incerlcbrata is devoid of corpuscles ; and the
young of many of these animals (which in the adult form
have corpusculated blood) have blood without corpuscles.
This is another fact which proves that " development is a
progress from the general to the &f>ecial, from the lower to
the higher form, and that the earlier stages of the history' of
higher animals are similar to the adult forme of lower
ones."

Although many forms of the Invertebrata have blood
devoid, or ueaily devoid, of corpuscles, other forms have
corpusculated b!ood.

The AcTiNozoA asd Echikoderwata.

The "chylaqupous" fluid in the Ar/inoznn aad Ee/rinodermata^
is analogous to the blood of higher forms. In both these
classes the blood is corpusculated ; some of these corpuscles
are distinct cells with wall and nucleus, but the majority of
' the corpuscles in tlie blood of the ActiTwzofi. and EehinorUr-
ituUa are of a very rudimentary nature. "They are probably
small masses of matter witli no definite limiting membrane
on their exterior, akin, perhaps, to the albonunons molecules
in our chyle."

The Myhiapuba

In this class the blood is contained in some part of its coune
in blood-vessels. It contains three distinct corpuscles, which
are devoid of cell-walls. '■ The simplest kind are pellncid
central nuclei invested by a few granules. Next rank the
oat-shaped corpuscles, where the nucleus is still very evident.
The third and most perfect form presents a central nucleoa,
surrounded and almost obscured by a large number of
granules. As yet no definite cell-wall is to be seen on the
exterior of the grannies."

PHYSIOLOGY OF THE INVERTEBRATA. 129

The Annelida.

The perivisceral cavity, communicating with the excretory
or segmental organs, contains a corpusculated fluid which is
nntritive. The corpuscles are oval, flat, granular, colourless
bodies without a limiting membrane. Besides these corpuscles,
the blood of the Annelida contains " actual cell corpuscles of
fusiform shape, and devoid of granules. Here, then, are
some corpuscles with a true wall, but all the solid, floating
particles of the blood are not yet of that high order of
structure.

The fluid present in the pseudo-hflemal system or vessels
of the Annelidu contains a substance allied to haemoglobin ;
and according to Dr.MacMunn, this red colouring matter func-
tionates in a similar manner to the histohaematins of other
Invertebrates, i.e., it has a respiratory function. It will be
noticed, that there is in the case of the pseudo-haemal system
of the Annelida a fusion of the functions of circulation and
respiration. This haemoglobin is dissolved in the fluid and
does not belong to the corpuscles. It is questionable whether
this " respiratory blood," as Prof. Huxley* calls it, possesses
any nutritive properties ; it appears to be entirely devoted
to the function of respiration.

In the Gephyrca, represented by SipitnciduSj the blood
corpuscles contain a coloured fluid between the external wall
and the central nucleus. This is the flrst appearance of a
coloured corpuscle, but it differs essentially from the coloured
corpuscles of the Mammalia, for in the latter the colouring
matter is distributed throughout the corpuscle.

Prof. E. Ray Lankester, F.K.S.,t has shown that the
perivisceral cavity of Sipimculus nudus contains a pale
madder-like colouring matter, ** which is due to a large
number of coloured corpuscles from ^^Vo to :r-«V^ of an

* The Anatomy of the Invertebrated Animals, p. 57.
t Procudiihgt of Royal JSociety, vol. 21, p. 71.

I30

PHYSIOLOGY OF THE INVERTEBRATA.

inch in diamett-r, and that this colouring mfttter, also found
in other parts of tlie worm, is not ha?moglobin.'"

Delle Chiaje showed that in Siji/nwi'Iiig baUinorojAvA and
S. ecMiwrht/nehitii " the arterial blood is red, the venous
brown. G, Schwalbe' found that the body fiiiid of Phaaeola-
soma- di>}iff(Uum (a Gephyrean) is a bright-rose or greyish-red
colour, and is cloudy owing to the presence of morpbologicd
elements, and that on standing in the air it gets darker and
darker until it aaaumea an intense Burgundy-red colour.
By long atandiug in the air this colour goes into a dirty
brown owing to decomposition, and iu drying the whole
asanmes a dirty green colour. Krukenbergt found the blood
of Sipitvcidtis niuhis to contain the same colouring matter as
that observed by Schwalbe ; he finds that it is the oxygen of
the air which brings about the colour change, and that the
colour is removed by CO,, This colouring matter gives do
absorption band either in the oxidised or reduced condition.
Krukenberg calls this pigment hiBmerythrin, and the chro*
mogen belonging to it hEemerythrogen. The colouring
matter is decomposed by H,S. The oxygen in the oxidised
blood-pigment seems, according to Krukenberg, to be more
firmly fixed than in oxyliKmogtobin. JI ilne-Ed wards i in
1838 discovered that certain Annelida possessed green blood,
his observations being made on Snhcllfi.

" Prof. Itay Lankester § on examining the blood of SabcH"
vvnirikibriiiii and SiphonaMomn (sp. ?) with the spectroecope
discovered the interesting fact that it only gives a banded
absorption spectrum, but is capable of being oxidisi-d and
reduced, and it behaved in such a way with potassium
cyanide and ammonium sulphide, as to have led him to
conclude that haemoglobin and this colouring matter fchloro-
,) ' have a common base in cyanosulphjcm, and perhaps'

* Archiv. fiir .Vltr. Anal., vol. 5, p. 3^8, et if;.
+ Vcrglelck. Phjtiol. St«<tUn. p. 85.
t ^BBofe* dtt SfitHHi Xalurrllft, 1838, Tol. 10, p.
tj Journal 0/ Analoniij and Pkjii'ioUigii, 1868, p. 114

PHYSIOLOGY OF THE INVERTEBRATA.

13^

in Stokes' reduced haBmatin.'* .... Prof. Lankester could
not obtain derivatives of chlorocruorin, owing, as he has
stated, to the apparent instability of this body, which
decomposes rapidly."

Dr. MacMunn has recently examined spectroscopically the
behaviour of chlorocruorin with certain reagents, but his
investigations will be de-
scribed later in this chap-
ter, when we consider in
detail the chromatology of
the Invertebrate blood.

The red blood of Luin-
brictts can be made to
yield crystals of oxyhac-
moglobin (Fig. 27), and
a solution of these crystals
^ves an absorption spec-
trum (Fig. 28).

Haemoglobin is also pre-
sent in special corpuscles y,^ 27.-Ckystat,s ok oxvilkmoglobin

-of the blood of Glycera from Blood of Lumbricus.

{one of the Pdychceta) ;

AS well as in the vascular fluid of Nepliclis and Hirudo. It

120

iiri|iiii|iin|iiii

130 14^0

ISO

Fig. 28. — Absorption Spectrum of Oxvh-km(k;lobin from

Blood of Lumbricus.

appears that this particular colouring matter is spectro-
scopically identical with Vertebrate haemoglobin.

The Insecta.

In a large number of insects the blood is colourless ; although
flometimes it is of a green, yellow, or red hue. This colour

* Hsemochromogen.

133 PHYSIOLOGY OF THE INVKRTEBRATA.

is not due to the flat, oat-shaped, granular corpuscles with
their well-defined walla and nuclei, but is due to the liquid ia
which they float.

In thf case of Phytophagous larvic, Mr, E. B. Ponlton.
F.li.S.," has shown that they owe their colour and markings
to two causes: — (i) ■'Pigments derived from their food-
plants, chlorophyll and santhophyll, and probably others;
(2) pigments proper to the larvH" or lar\-al tissues made use I
of because of some {merely incidental) aid by either or both
of these groups of factors. It may be generally stated that
a!! green colouration without exception, is due to xantlio-
phyll. All other colours fincluding black and white) and
some yellows, especially those with an orange tinge, are due

to the second class of causes Derived pigments oft«a

occur dissolved in the hlood. or segregated in the subcuticular
tissues ("probably the hypodermic cells), or even in a chitinous J
layer, closely associated with the cuticle itself." |

In some cases, the colour of the blood changes before the
pupal stage ia reached, while in others it remains the same
as in the larval condition. On this point Mr, Poulton (/tv.
vit., p. 277) says : — " the superficial derived pigments of
Sji/diix LiifiislH become brown in the dorsal region, befon?
pupation, while the colour of the blood is unchanged. In
Dicrnniirfi Vivnl'i the whole larva becomes reddish -brown,
and in this case the green blood changes to brownish-yellow.
The true larval pigment also changes before pupation, except *
when it is cuticular. Thus the lan-a of E. Angnhtria \
becomes transparent by the disappearance of dark pigment,
and the green blood gives its colour to the larva. The green 1
colour of the blood is generally retained in the pupal slat«,
and it is often of great importance,'"

According to Mr, Ponlton, the blood of Phytophagous larvie I
and pupir is acid to litmus-paper, with the exception of j
that of Epkifift jmnetni-in, which seemed to be neutral. This
acid, which is volatile, ia readily extracted with ether; but its |

■ I'ror. lioj/. S>c., 18S5, p. ajo.

PHYSIOLOGY OF THE INVERTEBRATA. 133

nature has not been determined. The corpuscles of Phyto-
phagous blood are amoeboid.

CoofftUatiaii. — *' The blood clots after a very variable period
of time, but generally darkens in about five minutes,
ultimately forming a solid black clot which is due to oxida-
tion. If blood be sealed in a tube, the small quantity of
oxygen pi-esent will form a thin black film on the surface of
the blood, and the action then ceases." Mr. Poulton has
shown " how blood can be kept indefinitely without clotting
in a section of tube with a cover-glass over one end, and the
other cemented to a glass slide." He has kept '* the blood of
Pygacnt Bmephalus in this way for a month, quite unchanged,
and on then breaking ofiE part of the cover-glass a thick
black crust was formed on the surface, while the blood
beneath became translucent instead of clear and transparent.
On removing the crust a second thin one was formed, but on
removing this, no further coagulation took place. If in
sealing np blood, or placing it in a tube section, a bubble of
air is accidentally included, coagulation takes place round
the bubble, but not elsewhere. This black substance is the
normal clot, for the injured places on larvad which have
healed are always black, notably the horns of Sphinx larvas
which have been nibbled off by others of the same species.
The coagulation takes place after the addition of water, or of
a saturated solution of neutral salt (sodium sulphate).
The occurrence of a reducing agent in the blood appears to
be very remarkable, but it is possible that the substance is
capable of again yielding up its oxygen, and so acting as a
carrier. It has been observed that if fresh blood be added to
that which is turning black on the surface, the black clouds
are redissolved. If this be not so, it is difficult to see how
the blood can be the int.emal medium for the supply of
oxygen in these animals, and one is tempted to the supposi-
tion that in the tracheal system we have a means for the
supply of oxygen direct to the tissues." Another suggestion
which occurred to Poulton was that " the coagulation is a

"34

PHYSIOLOGY OF THE INVERTEnRATA.

very similar process to the darkening o£ cuticular pigment
on larviD, and the darkening of the pnpal covering. It las
always been assumed that this darkening is due to light,
but it takes place rapidly and completely in pupa> buried
several inches under ground, in compact and opaque cocoons.
or sometimes in the heart of a tree." Furthermore, Ponlton
has never observad that darkness made the least ditTereno' to
the darkening of pupa'. It is, therefore, "very probable that
this will also prove to be due to oxidation, and possibly to
the formation of a substance similar to the black clot of the
blood."

Poulton has observed that " the brown and coloorleae
blood darkens as well as the green." ^|

Thr Adum. of }!ei-!ieii''i.~The action of (») alcohol (fifty pfl
O'-nt.) on the blood of 1'. Birerp/urlvs was to precipitattH
proteids ; and if tiie mL"cture is shaken, " the prott-ids and
pigments are precipitated as yellowish-green clouds, and in a
few minutes the upper part of the liquid becomes blue, and
ultimately black, from the formation of coagnlnm. The
proteids are decolourised and sink, the alcohol remaining
yellow with xanthophyll (the chlorophyll disappearing).
Absolute alcohol does not lie on the top of the blood (likt^
diluted alcohol), but mixes with it at once, (h) Chloroform
bcDaveain the same manner as ether, but it dtsK>lve3 nothing
coloured from the green coagulum ; the latter (xintracts in a
few hours, and a clear blue liquid appears between it and the
sides of the tube. The exposed surface of the coagulum
(tiie chloroform having sunk to the bottom) rapidly l^ecomwi
black, (i) Distilled water, like weak spirit, lies on the top of
the blood with a cloud of precipitated proteid (probablv
globulin) above the junction. On shaking, the cloud disap-
pears, and the blood only seems diluted ; if now more water
Ix" added (altogether many times the volume of the blood), in
a few minutes the whole fluid becomes cloudy, remaining
dark -greenish. On filtering, a blue solution comes through,
which slightly darkens for some hours. With less water the

PHYSIOLOGY OF THE INVERTEBRATA. 135

blood coagulates normally, although after a longer interval
of time, {d) Carbon disulphide had no efiEect for a consid-
erable time. Eventually the blood was coagulated (green)
bat nothing coloured was dissolved out.''

Tht Action of HecU. — " The blood of the pupa of Sphinx
Liffustri was heated in a glass tube in a water-bath ; no
change was seen till the temperature reached 132° F., when
part of the blood became slightly dim. By 141** the whole
of the blood was distinctly cloudy, but it was not till 180*
that the blood became quite coagulated — solid-looking and
opaque, the proteids being yellow with xanthopLyll. In the
interstices of the clot was a clear yellow fluid. The xantho-
phyll in the coagulum was easily extracted by ether or
alcohol."

Dr. L. Fredericq* has also investigated the nature of the
blood in the Inseda. He experimented upon the blood of
the larv89 of Oryctes nasicmiivi (belonging to the Coleirptcra).
The blood was extracted by making a small slit (with fine
scissors) across the skin of the back and the walls of the
dorsal vessel ; into this slit a slender glass canula was inserted
when the blood of the animal immediately rose in the tube.
The blood is a colourless liquid having somewhat the aspect
of the lymph of the MavimalUt, and holding in suspension a
large number of colourless globules which slightly interfere
with its transparency. The blood of Oryctes quickly coagu-
lates. This coagulation is not arrested by the addition of
sodium chloride, magnesium sulphate, &c. But a slightly
elevated temperature (54° C.) sufficed to prevent coagula-
tion.

When exposed to the air the blood of this insect becomes
a dark brown colour ; but the brown colour has not the same
intensity throughout the fluid ; it is of a deeper colour in the
vicinity of the mass of globules. Light has no action in
changing the colour; the change being due to oxidation.
After being coagulated with hot water, the blood of Ort/ctes

♦ Bulletin de VAcafUmie Boyale de Belgijue, 3® sfirie, tome i.

136 PHYSIOLOGY OF THE JNVERTEBRATA.

changes to a brown colour in coutuct with air. But the
coagulnm produced by alcohol is not acted upon by air.

When the oxidised or brown blood is examined by thfl j
'spectroscope, it does not show any chnracteristic absorption
bands.

At first sight the blood of IJrydes appears to cootun a
substance acting under the influence of oxygen in a mmilar
manner to hiomoglobin or hfcmocyanin. The substance J
which becomes brown in air, does not probably play any rMt \
in the respiration of the animal. The blood in the vessels U
perfectly colourless ; the brown colour which is produced
after it has been extracted from the body is probably a
cadaveric or post iiwriem pheuouienon comparable to the
spontaneous coagulation which equally occurs in this liqnid. J
In fact, the colourless substance, which becomes brown on J
exposure to air is not contained in the blood which circalatea, 1
but is formed at the moment of spontaneous coagulation. Itl
one carefully plunges the \at\x of OrycU-s into warm wat«dr4
(50° to 55° C.) for a quarter of an hour before openiag it,
the blood extracted from the dorsal vessel neither coa^latea
nor colours in air.

The production of the colourless substance (susceptible of
becoming brown in contact with air) has probably been
prevented by the temperature of 50° to 55° C. Forwhen once
this substance has been produced, the temperature of boiling
is incapable of preventing its combination with oxygen, and
n change of colour which it indicates.

Finally, the most important fact which proves that the
phenomenon of colouration does not play any roh- iu tb^
respiration of the animal, is that the brown substance once
formed constitutes a stable combination, which is not decom-
posed by acids or alkalies, and is not decolourised when
placed in rttnio or in a sealed tube.

The phenomenon of colouration which the blood of the
larvaj of On/rics presents when it is exposed to air, appears
to be a cadaveric phenomenon, and as already stated, com-

i
a

° M

PHYSIOLOGY OF THE INVERTEBRATA, 137

parable to spontaneous coagulation. The substance which
becomes brown in air does not form any intermediate vehicle
between the exterior air and the tissues which require it.
The existence of such an intermediate vehicle is most
doabtfol, especially when one bears in mind the anatomical
disposition of the respiratory apparatus in the Insecta^ i.e.y
the air penetrates by the tracheae among all the living tissues.
By means of the trachea) the function of respiration is carried
on in every part of the body.

The Crustacea.

Dr. L^n Predericq* has examined the blood of various
Crustacea. The blood of crabs, lobsters, &c., which live in the
sea, has exactly the same taste as sea water ; which leads
one to suppose that the blood or nourishing fluid of these
animals has the same saline composition as the waters in
^vvhich they live.

A.coording to an analysis of Backs, and cited by Pelouze
ckiid Premy,t the water of the North Sea contains a little
more than three per cent, of soluble salts : —

Sodium chloride

. 2.358

Potassium chloride .

. 0.101

Magnesium chloride .

. 0.277

Magnesium sulphate .

. 0.199

Calcium sulphate

. O.III

3.046

It tastes strongly salt and bitter.

In support of the idea that the blood of certain Cimstaciut

'^^^ng in the North Sea, has the same saline composition as

^b© medium in which they live, Fredericq obtained the

following result after analysing the blood of an Ostend

^^oater (Homarus v^dgaris) : —

3.040 per cent, of soluble ashes.

• BvUttinM de VAcmUmie liojfa^e de Belffiq^te, y s6rie, tome iv.
t Train de CMmit, y ^., tome i, p. 252.

138

PHYSIOLOGY OF THE INVERTEBRATA.

The }ilood of a lai^e female lobster (bled by making a cut
in th<' claws) weighed 26.49 grainiaes. This blood waa dried
at a moderate heat in a covered crucible ; then heated to
compifte carbonisation. The porona carbon waa exhauak'd
with warm water. The filtered solution was evaporated to
dryness, the residue allowed to cool in a dessicator. and
weighed with the usual care. The 26.49 grammes of blool
yielded 0.8055 gramme of soluble salts, equal to 3.040
per cent.

23.01 grammes of the blood of the crabs {Oareinvix vusmi$}
of Roacotf yielded 0.708 gramme of soluble salts, eqn^ ^
3.07 per cent.

The crabs (('. sjwcjwrs) of Roacoff living in sea water of a
density of 1.026 were also examined; 14.78 grammes of the
blood of these animals yielded 0.445 gramme of soluble ealU,
equal to 3.001 per cent.

The hermit crab {I'ti'tijmn-inus'pfi'jnruii) of Roscoff, wh<
blood had a density of 1 .037, was examined by Fredeiii
13.54 grammes of this blood yielded O.419 gramme of soluble
salts or equal to 3.101 per cent. In the case of another
hermit crab the blood had a density of 1. 036, and 31. 08
grammes of it yielded 0.965 gramme of soluble salts.
equal to 3.104 per cent.

In the case of the sea crayfish {I'alinvTua viUgnris) of
Roscoff, 22.94 grauirnes of blood yielded 0.666 grammes of
soluble salts, equal to 2.9 per cent.

In the case of Mnjn s'/iiijifn/o of Roscoff, 15.60 grammes
of blood yielded 0.476 gramme of soluble salts, equal to
3.045 per cent.

The aea water of Itoscoff in which the above Crustaceans
lived was also analysed with the following results:- — 27,312
grammes of sea water yielded on evaporation 0.929 gramme
of saline residue which is equal to 3.401 per cent. In
another determination 26.266 grammes of the same water
yielded 0.894 gramme of saline residue, which is equal to
3.407 per cent.

the
alu,

PHYSIOLOGY OF THE INVERTEBRATA,

139

The Maja stpiinado of Naples lives in sea water which is
exceptionally rich in saline matter ; 20.669 grammes of this
water yielded 0.821 gramme of saline residue, equal to 3.9
per cent; 14.807 grammes of the blood of Maja yielded
0.498 gramme of soluble salts, equal to 3.37 per cent.

Not only has Fredericq examined the blood of various
Crustaceans inhabiting sea water but he has also examined
the blood from those living in brackish and fresh water.

6.48 grammes of the blood of CarcinuH mcenas inhabiting
brackish water yielded 0.096 gramme of soluble salts, equal
to iu|.8 percent.

To examine the blood of fresh water Crustaceans seven
crayfishes {Astacus Jluviatilis) were used in the experiments.
A large quantity of blood was obtained by making an incision
in the claws. Its taste was only slightly saline; 23.453
grammes of it yielded 0.221 gramme of soluble salts, that is
less than one per cent. (0.94 per cent.)

The following table gives a summary of the results
obtained concerning the saline matter of the blood of various
Crustaceans and the medium in which they live : —

PROPORTION OF SALINE MATTER IN

THE BLOOD OF

CRUSTACEANS.

Water

Blood.

in which the

Animals lived.

Per-

Deniiity.

eentoge
uf loluble

DeiiHity.

Percentaffd of
salts.

salts.

Aitaeua jitt riatilii .

0.040

fresh water

Cttrcinus iwtnas .

■ , - ' 1.480

1 1

•

brackish
water.

»» M • •

. , — 1.650

1.007

about 0.9

ff »» • «

— 1 1.560

1. 010

,. 1.3

f» ,» . .

— 1.990

1. 015

f, 1.9

ff f» • <

— ' 3.001

1.026

3.40

»f f» • •

. — 3.007

—

3.40

Homttrus vulgariM .

3.040

1.026

3-41

Platycarcintu pof^urut .

. 1.037

3.IOI

1.026

340

" »»

1.036

3.104

1.026

3.40

Fahnurus ruiffaris

, —

2.900

1.026

3.40

Maja gquintulo

3-045

1.026

340

W ff •

. — ' 3.370

3.90

I40 PHYSIOLOGY OF THE INVERTEBPATA.

The blood of crabs living in brackish water contains I
smaller percentftge of saline matter than those living L
wat«i- ; aotl the blood of crayfishes living in rivers conta
only a very small amount of saline matter — ^generally 1
than one per cent.

According to the above investigationa it appears that tJ
is an exchange of salts, forming a kind of eqailibriam
between the composition of the blood and the extt'rnal
medium in which these Crustaceans live. This eijuilibriam
is the result of the simple laws of diffusion.

Among the fresh water Crustaceans the albumincaftl
substances of the blood probably retain a little more *
of the soluble salts than is contained in the extenutl
medium.

It is probable that this exchange of dissolved salts is
established by the respiratory organs — the brauchiie. The
delicate walls of the branchite, which separate the blood from
the external medium, allow the respiratory gases to pass by
Btmple diffusion : and most likely these delicate walls act in
a similar manner t^ a dialyzer with easily diffusible salts.
The albuminoid substances of the blood do not pass into the
external medium.

The nourishing fluids, to which the illustrious physiologi
—Claude Bernard— gave the name of " milieu interieur,"!
have not (with the animals previously mentioned) the
constant chemical composition and independence of the
conditions of the " milieu ext*;rieur " which characterises t
blood of the higher animals.

Among fishes {Fisces) the branchial walls allow eqnallyj
pass the oxygen and carbonic anhydride of respiration. Otn
can therefore understand tliat there is a similar exchange of
salts between the blood and the external medium. But
experience proves that it is the inikTxc of that which takes
place among the Crustaceans and other Invertebrates ; for
the blood of marine fishes has a saliue composition which ia
entirely difff-rent from that of sea water. The blood of a sole, a

x> the

logii^l
ieur,'^H

the
the

BtJl^

PHYSIOLOGY OF THE INVERTEBRATA,

141

haddock, and a weever does not contain more soluble salts
than the blood of fresh water fishes.

Among fishes the interior fiuid constituting the blood is
isolated more or less from the external medium in which the
animal lives. In regard to this there is an advance on that
which occurs among Invertebrates.

The blood of the CrvMacea contains corpuscles which are
very well defined. They are oval in shape, granular, and
present a very distinct wall externally and nucleus within.

The Mollusca.

The blood of the lower Mollusca {LamellHyranchiata and
€kiMeropoda) is corpusculated, but the nuclei (which are
^nerally present) are sometimes very indistinct.

The percentages of saline matter contained in the blood of
^nodonta and MytUtts were found to be the following* : —

1.002
1.796

II.

III.

IV. Avenge.

•

Anodimta eygnea .
M^^^U . . .

0.998
1.799

1.006
I.8IO

0.996 I.OCX)
1.800 l.Sof

It will be observed that the blood of the fresh water
snussel contains a smaller amount of saline matter than that
<Df the marine form.

The blood of the Mollusca is principally colourless, but Dr.
Xi. Cu6nott has recently shown that the blood from the heart
C3f Aplysia depilans (one of the Gasteropoda) has a distinct
^^■ose colour, due to the presence of 0.636 per cent, of an
^baminoid which is precipitated by alcohol, acids, mercuric
<^oride, and the usual reagents. Its colour has no relation
tio the presence of oxygen, and it seems improbable that it
plays any part in respiration. When the blood is dialyzed,

* See Dr. Griffiths' paper read before the Royal Society of Edinburgh
^n June i, 1S91 {P, S. & E„ vol. 18, p. 288).
t Comptes Bendua, vol. 1 10, p. 724.

a
n

°°1

142 PHYSIOLOGY OF THE INVERTEBRATA.

or exposed for a long time to air, it decomposes spontaneously,
part of the albuminoid remaining in solntion and part
separating in a white, flocculent form. This albuminoid is
entirely distiuct from hfeniocyanin, and has been called _
ha;morhodin. If the blood is concentrated in eaeuo j
heated, it becomes opalescent at 58° C, and coagulater
completely at about 70' C.

The blood of Aph/siii jninetala is quite different, and
contains 1.77 per cent, of a perfectly colourless hiemocyanin
which is not affected by air, and coagulates at about 76° C
This albuminoid probably plays no part in the absorption q
oxygen.

In the G(tsteTopixl(i , CtpJi^xJojxidfi, as well a« in the Crnslneta
and Arnchnidn, the function of respiration is brought about
by an albuminoid substance analogous to hemoglobin, but
contains copper instead of iron. This substance, whites
Predericq* named h^mocyanin, combines with oxygen, foro^fl
ing a very unstable combination.

The blue colouring matter of the blood of (letoptis 111/gari
is due to the absorption of oxygen, for if tlie blood is plat
in vnciw it loses its colour, but regains it in the preseooe <
air or oxygen. Htemocyanin occurs in the arteries of t
living Octopus.

Krukenbet^ examined the blood of Sfjna officimd^
C'nn-imtJi mtrHOg, Homnnts riili/nris, Srpiiilff majit-K, as wd
as other species of the Mollitsea and Cmslaem, and obaerreA'
that the blood becomes blue by shakiug with oxygen or air ;
and that the bine colour disappears more or less with carbonic
anhydride. " Krukenberg also found great differences in the
hlood of individual Gasteropod Molluscs, which led him to
assume that perhaps the oxygen in such cases is in a firmer
combination with the haimocyanin than is the case in Crabs
and Cephalopods. He also made the interesting obaervatioa^

n-hhft lU Zoologie Expiry
■rilklch. Phyial. Stmlicn, u

entaie, 1878;

ting ooaervftuoa^j
\ta Fredericq'B ^^|

PHYSIOLOGY OF THE INVERTEBRATA. 143

tliat the blood of Crabs and Cephalopoda on treatment with
carbonic oxide became colourless, but regained its blue colour
on shaking with air. This behaviour is different from that
of hsBmoglobin when similarly treated. It was further found
that blood which had become blue by the reception of oxygen
if allowed to stand in a test-tube exposed to the air did not
lose its blue colour from above downwards, but from below
upwards, whence he concludes that the blueing is not due to
suspended particles, but to the presence of a chromogen

which becomes blue by the reception of oxygen He

oould find no hsamocyanin in the blood of several Molluscs
(^.^., Tethys fimhriu, Doris tuhemdata, Aplysia dc^ilmis^
Ac)."

Although the blood of the higher Invertebrates, as a rule,
contains copper, in some this element is replaced by man-
ganese. Krukenberg has shown that the blood of Pimia
sqtLanwsa (one of the Lavidlihrmichinta) as well as the organ
of Bojanus are rich in manganese. If a borax bead is dipped
into the blood of Pinna and then heated in the oxidising
blowpipe flame, the bead becomes a distinct violet colour, and
in the reducing flame it remains colourless.

It is probable that copper, manganese, and possibly other
metals play the same part in the blood of the Invertebrata as
iron plays in the Vertebrata,

The author* of the present volume has also extracted
copper from the blood and organs of Scput officinalis ; but the
process was entirely different from those of Fredericq and
Krukenberg.

In the majority of the Invcrtthrata the carrier of oxygen
to the tissues is hsemocyanin contained in the blood ; but in
many of the Annelida, as well as in nearly all Vertebrates,
the transport of oxygen from the surrounding medium (air
or water) to the living tissues is made by means of the
haemoglobin of the blood.

• Se6 Dr. Griffiths' paper in Chemical Xeic^, vol. 48, p. 37 ; Journal of
Chemical Society, 1884, p. 94.

144 PHYS/OLOGY OF THE INVERTEBRATA.

This substance (as is well known) forms an oxygemsej
combination whict is very luistable, and which is carried by
the blood across the tissues of the animal, and is there
dissociated, yielding its oxygen to tie elements of thoee
tissues which require it.

I'rof. llay Laukester discovered that in some Annelids the
hemoglobin is replaced by a gi-een -colouring matter (cLloro-
cruoriu).

Reverting once more to the saline matter contained in the
blood of the MoUtmcu, the author* obtained the folloi
results fi

iwiiu^H

'■

It.

.«™^

•

Hdix}»mat!fi .

..065

1.072

..069

LOSS

ffflix W,,^>f .

1.079

l.oSo

1.Q62

1.077 1

Limninu iliu/anliii

.200

i.K)3

,.2,0

■-L

Limaxfarui

MOO

i.iiS

I.IIS ^H

[ \

Linua mariimm ,

1. 119

i.ur

1.II4

....■

i!«

RittUarrdgala .

1.699

1.706

1.710
1.711

..698

..7.9

g-1 1 (ktapu. r«/r,«n-- .

2.840

1.862

.85.

".Si"

3.004

3-032

3.=»

J.018

Dr. L. Fredericqt found 3.016 per cent, of aolable tJ^

insoluble salts in the blood of Octojnis vvlyai-is. 1

The author of the present volume has submitted to
analysis the ashes of the blood of several Invertebrate
animals. The ashes were obtained by incinerating the blood, .
partially covered in a platinum dish, at a very low t«mp(

■ A paper read before tho Roj'bI Sooict.v of Edinburgh 01
+ ItuUtlini lU FAca-lfmie lloi/'aU <le Bth/iqur, 3° sfirie, torn

I, iSgt^l

PHYSIOLOGY OF THE INVERTEBRATA.

145

ture. By so doing the alkaline metals are not volatilised as
they are when a high temperature is used.

The following results represent the averages of three
analyses in each case : —

Cmnewr
pmgmrUM,

CarcimU9
mtenoi.

Jstmcu*
JiMvMiih,

Faiimurmt
PuigmrU.

Homaru*
vulgarit.

Copper oxide (CnO) .
Iron oxide (Fe^OJ
Lime (CaO)
MagneeiA (MgO)
Potaah (K.O)
Soda (Na.0)
Phoephonc acid (P,OJ
Sulfamic acid (SOJ .
Chlorine .

a 22

trace

3.55
1.91

4.97

43.90

4.90

2.90

37.65

0.19
trace

1.89

4.78

44.91
4.86

2.81

36.98

0.20

fit

4.82

44.96

4.81

2.75
37.00

0.18

3-79
1.90

4.92

43.98

4.87

2.86
37.50

0.18

trace

4.77

44.99

4.84

2.81

36.96

loaoo

99.99

loaoo

100.00

99.98

Copper oxide (CaO) .
Manganese oxide

iron oxide (Fe.OJ .
Ume (CaO)
^fagneeia (MgO)
l*otaah(K,0) .

SodaOr;?)) . .

•Latbiom

^ftioephoric acid
(PjOJ . . .

^iilphnxic acid (80,)

v^^iiorine . • .

Cfgnea.

a 23

3.61

1.82

4.90

44.18

trace

4.89
2.80

37.55

99.98

4.82

2.76

37.92

100.00

4-79

2.73
37.88

100.00

MgtUut
edmii*.

FiHHa
tquamoaa.

Sepia
nJiciHaiu.

0.22

trace

a 24

trace

0.19
trace

—

3.72

1.86

4.80

4390

3.70

1.83

4.86

44.02

2.31

I.51

4.92

45.40

^~~

^■^

4.90

2.81

37.90

99.99

Oriitpu$
vulgarii.

0.21

2.40

1.55
4.90

45.31

4.88

2.83

37.92

100.00

llhere is no doabt, from the above analyses, that copper
Pl«i»jg an important part in the blood of the InvertebrcUa ; in
it plays a similar rdle to that of iron in the blood of the
ler VerUbraia,^

^^ Detected by the tpectroscope.

"^ Bee Dr. GrifBths' paper road before the Royal Society of Edinburgh on
^'•^^e 1, 1891.

PHYSIOLOCV OF THE INVERTEBRATA.

The Chromatology of tse Blood op the IsvERTEBRATi

We have already alluded to some of the colouriag tnatt
contained in the blood of the Inverti^>mta, but as a consider-
able amount of work has been done in this direction, we
propose to describe more fully the reanltB obtained in this
important subject.

In England the two great authorities on the colouring
matter of the Invertebrate blood are Dr. C. A. MacMnnn,
and Mr, E. B. Poulton, F.ll.S. Both of these scientists have
presented ua with a valuable series of investigations which
we now proceed to describe.

The colour of the blood in the Tnn-rtel/riifa " does not as a
rule belong to the corpuscles, but to what in them answers to
the liquor sanguinis of Vertebrates, although there are many
exceptions. In some hremoglobin occurs. Thus, Prof,
Lankester has shown" that in Gh/cern, Cnpitdla, and P/ioronit.
and in Solen Ugtimen, it is found in special corpuscles ; while in
the vascular fluid of others it is found dissolved, i.'j., with cer-
tain exceptions in some chastopod Annelids, in some leeches
{Nqihdin, Hirudo), in Polin sntupiiriibm (ft Turbellarian), in
the special vascular system of a marine parasitic Crustacean
observed by E. van Beneden, in the general blood-system of
the larva of the Midge (C'hiroiiomus), in the general blood-
system of the Mollusc Planorhis, and in the general blood-
system of the Crnstaceans, Daj'/uni and Cheiroctpiuilvs."

Hsemoglobin is also present in the blood of Lviiibricui
Annicola, and Euniec ; and it has already been stated that
this haemoglobin is spectroscopically the same as that found
in Vertebrate blood.

The blood obtained from five hundred earth-worms {Lum-
bricus ierrestris) was treated with benzene, which readily
dissolves the colouring matter. The mixture was allowed to
stand for twenty-four hours at 0° C, ; when it separated
into two distinct It^yers. The one containing the colouring

* Proeetdingi of Boyal Sociily, vol. 31, p. 71. ,,^^^^^^H

PHYSIOLOGY OF THE INVERTEBRATA.

iiiatter was then separated from the other ; and about one-

^xtli of its volume of pure absolute alcohol was added. Afler

filtration the alcoholic extract was exposed to ~ 12** C, when

^ crystals were obtained. These crystals yielded the

following results on analysis : —

Blood of LHmhrlv%9.

1
1

Blood of
Dog.

II.

1
III.

1 d^ibon ....

53.91

53.85

—

52.85.

1 ^^^'diogen

7.02

7.10

7-32

^^itrogen

—

16.17

^^alphup ....

0.41

0.37

—

0.39

^**^:in ....

—

0-39

0.43

^^^*C7gen ....

—

21.84

The above analyses prove that the colouring matter of the
of Ltcmbricits is comparable chemically to that of a

to
of

^^:Ki;ehrate animal, like the dog.*

-Although hasmoglobin is present in the blood of certain
ertebrates, the chief constituent in the blood of the
ority of these animals is hjbmocyanin, a compound said
analogous to haemoglobin, but containing copper instead
iron,
t Lb well known that '* the blood of many Molluscs and
hropods is of a blue colour after exposure to the air, and
^^^ i8 in most cases due to the presence of hsemocyanin."
^ i) The Echinodennata, — Dr. MacMunnf has examined
^ blood of Holothuriti nigra. It does not contain hsemo-
8*^^^l)in, but when examined with the spectroscope it strongly
^^^orbed the violet end of the spectrum but gave no bands.
i^t^e colouring matter of the blood *' is soluble in absolute

* Griffiths in Proc. Hoy, Hoc, Kdinh., 1891 (June i).

t Quarterly Journal of Microscopical iSatnct^ voL 30, p. 60.

til.

148

PHYSIOLOGY OF THE INVERTEBRATA.

alcohol, forming a deep yellow solution, giving an ill-de<fined
band at tlie blue end of the green, beginning to be feebly
shaded at about X 526, darker at X 507. and extending to
about \ 474. On evaiwration it left a reddish residue soluble
in ether, in chloroform, and other li(K)chrome solvents, and
when in the solid state il became a transient blue with nitric
acid, bine, green, and brownish with sulphuric acid, and
greeniah-yellow with iodine in potasaic iodide. Therefore, the
blood of Holothuric, niijra contains a red lipochrome like that
of certain Crustaceans, aa Dr. Halliburton* has discovered."
Dr. MacMunn also found this red lipochrome or lutein
in the digestive gland of H. nigra ; and states that he •
has no doubt that it " is built up in the digestive gland
and carried in the blood current to be dejwsited in other "
parts of the body, though what its role may be when deposited J
there, it is difficult to say. It is not easy to see of what use ^
80 much brilliant coloration as exists within the body ot ^
Holothuria nigra can be, except that the lipochrome is *
changed into some other constituent. If it be respiratory
as tetronerythrin is believed by Merejkowskyt to be, «
could see some reason for its existence," but as Dr. Ma<^f unn
has repeatedly shown, " what has been called tetronerythin
does not exist in two states of oxidation. Merejkowskj'
would doubtless call the red lipochrome of H. nigra tetron-
erythrin without hesitation ; but since he published his results
our knowledge of these fat pigments has undergone a change,
for we now know that there are a great number of pigments,
formerly, with regard to their supposed respiratorj- properties,
included under the name tetronerj-thrin, which are distin-
guishable from each other, and which cannot any longer be
called tetronerythrin, the rhodophan of the retina % is not
respiratory, nor is the true tetronerythrin in the so-called
' roses ' around the eyes of certain birds, respiratory."

" -Tburno/ of Pbytiology, vol. 6.

-t BnlUlin de la SocUli Zoologuiw dt Fraurr, 1883. p. 8t.
J KOhnC in Uatertuchunijca a. d. Phytid. laitil. d. Un
Bd. I, Hett 4, nnd Bd. 4, s. 169-348.

.'■ aj

PHYSIOLOGY OF THE INVERTEBRATA. 149

lipochromes included nnder the name tetronerythrin by
Merejkowsky '^ fail to respond to the test used in determining
whether any pigment is respiratory or not, namely, change
of ooloor and spectrum nnder the influence of reducing
agents."

Dr. MacMunn* has also investigated the brown colouring
matter of the perivisceral fluid of Echinus (esciUentus ?) and
sphetra. This colouring matter gave two bands, one between
D and E covering E, and the other between b and F, the first of
which became decidedly darker after the addition of ammo-
nium sulphide. MacMunn named this pigment echinochrome,
and it has a respiratory function.

Since his discovery of echinochrome, MacMunn has made
some valuable observations on the perivisceral fluid of
Strongylocewtrotua lividus. On opening a specimen a pale red
fluid exudes from the perivisceral cavity. " In a short time
a clot forms ; this becomes gradually darker in colour and it
contracts more and more, until all its connections with the
side of the containing vessel are broken, and it finally
shrinks into a small brown-red mass. The corpuscles are
carried down by this clot, and it is to them, not to the
plasma, that the colouring matter belongs." Prof. P. Geddes t
(who has worked out the morphology of the corpuscles of the
perivisceral fluid of various Echinoderms) has shown that the
finely granular, pale corpuscles run together to form Plas-
modia, and that it is to their fusion that the clotting is due.

*' The corpuscles present all degrees of coloration, from a
brilliant red, through a pale orange, to colourless. The red
oaes are nucleated and of irregular shape, and rapidly throw
oat amceboid processes, so also do the others. The nucleus is
strongly refracting and gives the corpuscles the appearance of
a round hole having been punched in it. The red corpuscles
measure from jzto inch in long diameter x ^j^ inch in
short, down to ^^^y in long x -^^^^ in short, while several

* Pr0eudtKg9 of Birmingham PkUoMopkical Society, vol. 3, p. 3S0.
t /Voc Boy. Hoc,, i88a

i;o PHYSIOLOGY OF THE INVERTEBRATA. ^^k

measure jnsW in both diftmeters. The pale ones ^jVar " i^H
down to ip,V < BTnnr! the latter are multinnclented.

" The pigment itself in the freah state showed no distinct
bands, bnt treated with caustic potash in the solid condition

IJ C D Kb I- (i

d
f

i
}

■I

+KHO. <f«ti
cloi.
Kihinoehremr

Do. + Sun-
nous chtonde,

in blood dot.

Do. + .S-«HO.

Do. in stwlot
alcohol.

Do. WilbMXfc
add.

Do. with sUd-

noiB Chloride

Dried clol in
Do. in ctiloio-

Do.iitcarboD

bisuJpliidr

Do. in betiHj..

Krrali clol in
elyoOTOt

Do. itith Man-

Fic

39.— SpCCTKA UF Pt;K[Vlfi<;Kl(,VI. Fl.L-ll> Of Stronqvukknt*
{AfUri::. A. MacMcnn.)

the colour changed to dark purple " and showed t
the spectrum « (Fig. 29).

MacMuDD says that the deepening of co
echinochrome undergoes on exiwsure to the air

"■"-1

our which
must be iM

PHYSIOLOGY OF THE INVERTEBRATA. 151

part dae to the oxidation of a chromogen, if so we may infer
the existence of such, and name it echinochromogen.

Echinochrome differs from the blood pigments of most
Invertebrates, as it is readily dissolved by a great number of
solvents,

It con be obtained in solution and isolated by two
methods: — "(n) The fresh blood-clot can be extracted with the
solvents mentioned before, or (i) the clot may be separated
from the semm by filtering, the pigment dried at the tempera-
ture of the air (as it changes by using heat) and the dried
pigment thus obtained treated by solvents. By the adoption
of the latter method it can be obtained in a purer condition."

" The ' aerum ' after separation of the clot is a faint yellow
colour and shows two faint bands in the green, but if allowed
to stand some time in contact with the clot it becomes a
faint violet red," and tlien gives the spectrum seen in Fig.
29. h. On the addition of stannous chloride to the serum
dark bands (Fig. 29, c) make their appearance. These bands
have the following positions, X 541.5 to X 532 and X 50G to
A4S6.5. In the oxidised condition the serum has a spectrum
of the same kind but the hands are feebler. The serum
i(i "faintly acid or neutral, faintly opalescent on heating,
opalescent with absolnte alcohol, and faintly so with ether."

Spectra Fig. 29, d and c are those of the brownisli-red
clot, after standing in contact with the serum and with sodium
hydroxide respectively.

The red alcoholic solution of the clot gives the spectrum
represented in Fig. 29,/. These bands read: first, X 557 to
A 545-5 ; second, X 524.5 to A 501 ; third, A494.5 to X475.
On the addition of ammonium sulphide two new bands make
their appearance. The first is from X 531 to X 507 ; and the
second, A494.5 to X475, the colour of this solution being
changed to yellow, and on shaking with air remained the same.

On the addition of acetic acid to an alcoholic solution of
the fresh clot, the spectrum given in Fig. 29, g is seen. " The
spectrum of the original absolute alcohol solution is that

153 PHYSIOLOGY OF THE INVERTEBRATA.

of the neutral pigment, as can be proved. Hydrogen peroxide
did not affect the bands. Hydrochloric acid produced the
same effect as acetic acid; tlie bands reading: first, X 545.5
to X 529.5; second, X 51 1.5 to X 488. When the alcohol
solution is treated with stannous chloride the colour chaogea
to yellow, and two very well-marked bands appear (Fig. 29, A).
Dark part of the first band, X 535 to X 511.5; second,
X 496.5 to X 477. Sodiam hyposulphite changed the colour to
yellow, but the original bands could be seen, although faint"

Dr. MacMunn has also examined solutions of echinochroi
in chlorofonn, water, ether, carbon disolphide ; some of
spectra of these solutions are given in Fig, 29.

Echinochrome is only partially soluble in water and alcohot'
but is soluble in chlorofonn, ether, benzene, glycerol, carbon
disulpliide, and petroleum ether. It is capable of existing
in two states of oxidation, therefore its function ia of
respiratory nature. Echinochrome has not been obtAined
the crystalline condition.

(2) The Antfluh. — The blood of many Annelids contains
bsemoglobiit ; some contain pigments allied to chlorophyll,
while others contain lipochromes.

The blood of Areiikolii pisfntorion (one of the I'olffcha:!")
contains, besides hemoglobin, a lipochrome or Upocbromes.
Dr. MacMunn obtained a dark brown-green extract by treating
this worm with a solution of caustic potash. This solation
gave no bands. But he has extracted from the digestive
system and the integument of Annicola certain lipochromes.
which have well-defined absorption spectra.

The spectrum of the blood of X'l-n's J)u»ierillii consists of
a single band like that of reduced hR?nioglobin, The spectrum
of an atjueous solution of the blood of this worm consisted of
two feeble bands ; " the first was like that of the first of
osyhoemoglobin, but the second was rather narrower than ia
the second blood-band. These bands read approximately :
the first, fi-om X 584.5 to X 574, the second, about X 550.5
X 5 36, and a third one at the blue end of the green, fromal

rota^H

■^hot
bon
:ing

boa^

PHYSIOLOGY OF THE INVERTEBRATA. IS3

X 507 to A 474 (?) was visible. Sulphide of ammonium caused
these bands to disappear/' but Dr. MacMunn could not then

detect that of reduced haemoglobin.

The various colouring matters contained in the blood

and organs of certain worms are given in the following

table : —

Chloroeroorin.

dpkrodite .
SabeOa

C^irratulus,

rtbeOa .

irudo

^i-^JuKSUpttrwi

reiUcola .

present
present
present

"-•"»-• Sf^X^L.

present

present
present
present

absent
present

present

H»mogloUn. !

absent
present

present
present
present
present

present
present

Xhr. MacMunn has examined the green fluid (containing
ct»>l«rocruorin) of Sabella by means of the microspectroscope.
f^^ spectrum (Fig. 30, a) consists of a dark band before
^» and a feeble one between D and E. The green blood has
" ^ reddish tinge with reflected gaslight, and in most cases is
8**^^ with transmitted daylight, and reddish with transmitted
K^^light. Ou dilution with water this fluid gave two bands:

1S4

PHYSIOLOGY OF THE INVERTEBRATA.

the first from \6iStoX $93, the second fromX 576 to X 554.5."
On adding ammoninm sulphide, tbe spectrum Fig, 30, b is
produced. The first of these bands extends from X625 to
X 596.5 (?), bnt this, and also the second band, says AfacMnnn^^^

chlaf»^|

NH4HS.

Do. Imm ■

dilated pan - _
blood-nod^^

pan. iithiM^C

specimen.

pan. a fourth'

Fio. 3Q.— Spectr;

" were very faint." After the addition of sodinm hydrc
to this solution, a dark band is seen covering D, "whi
recalls to mind the band of alkaline hiematin (Fig. 30,c),i
this band extends from X 595 to A 576."

V When the blood ia treated with alcohol and potassinm
hydro3dde and filtered, a yellow-coloured solution is obtained
" free from bands, but on adding ammoniom sulphide a band
appears covering D" (Fig. 30, (/). "On treating aqueous
solntions with acetic acid the bands faded away, and the
colour of the solution changed to a brownish colour (gaslight).''

SlacMunn tried the action of alcohol acidulated with
sulphuric acid on chloi-ocruorin, and obtained a greenish
solution, which showed a faint shading in the greeu, too
indistinct, to map.

" Hence none of the decoiuposition products of hremoglobin
or hiematin conld be obtained, the pigment, as Prof. Lan-

■ tester had abeody shown, being destroyed by the reagents
required to produce acid hiernatin and ha?raatoporphyrin.
The blood of the pseudo-hieiiial system of Si-rjiula contortti-
}>!icttia presents some resemblance to that of Snbi-Un. There are
slight ditferences in the blood spectra of some specimens, which
donbtless are due to the pigment being present in different

■States of oxidation, and on comparing some of these spectra
(ritli those of the histoh^matins and with the decomposition
•roducts of hiemoglobin, a striking likeness is apparent."
" On putting a Scijmlit into the compreBsorium, and bring-
ing gentle pressure to bear on the upper surface of the
unimal, and examining with the microspectroscope, using a
good achromatic substago condenser, a series of spectra are
obtained when the various parts of the animal are moved
Under tlie objective ; what these parts are is seen by looking
«3own the left-hand tube of the microscope. In this way we
can differentiate the blood-vessels, intestine, gills, opercu-
lum, and other parts, and study the spectrum of each.''

With the paeudo- ha?mal system of S'-rjtu/'t, MacMunn
obtained a spectrum represented in Fig. 30, c. The band
before D is like that of Lankester's chlorocruorin, but the
first after 0 and also the second are different.

An aqueous solution of the blood from the pseudo-htemal
aystem is yellow by daylight, reddish-yellow by gaslight, and

PHYSIOLOGY OF THE INVERTEBRATA.

IS6

PHYSIOLOGY OF THE INVERTEBRATA.

its spectrum is represented in Fig. 30, c. The band before I
was from X620.S to X 593, the second aboutX 583.5 to X 572,
the third uncertain (about X 551 to X 532). After the addi-
tion of ammonium sulphide, "the only band seen with cer-
tainty was that before D, which seemed slightly nearer the
violet." In an alcoholic solntion only a faint band was visible
from about X 501 to X477.

In a specimen in which the blood appeared a bright
carmine-red colour, JIacMnnn obtained the spectrum repre-
sented in Fig. 30,/. The second band of this spectrum
resembleB tlie first band of haemochromogen, and is really
the same as Fig. 30, h.

Fig. 30,? rei)r686nta the spectrum of the blood from a
dilated part of the principal blood-vessel of Scrjmlij. "The
darkness of the second band at once distinguish cs the pigment
from chlorocrurorin." Fig. 30, h and / also represent the spectra
of the blood from the same part of a third and fourth specimen.

"An aqueous solution of blood obtained from a dozen
specimens, whose blood gave the above B]>ectra, was yellow,
and showed the three bands represented in Fig. $o.j, and these
gave the following readings: — First band, X618 to X 593 ;
second, X 5^2 to X 570.5 ; third, X 551 to X 529.5 (?) On
treatment with Bulphide of ammonium the solution became
slightly greener ; no bands could then be seen after D, and,
that before it was very faint. Kence it would appear that thM
two- and three-handed spectrum denotes the oxidised stato. fl

"In some Sayul a:, whose blood was not red but brown, J
the bands before and after D reminded one of chlorocruorin
(Fig. 30, 1.-). An aqueous solution of the blood of these sped-
mens had a reddish tint by gaslight, and gave three bands,
which read as follows: — First, X 620.5 ^o ^595; Bocond.
X 538.5 to X 570.5; third, X 551 to X 532. On adding sul-
phide of ammonium, the band before D read X 620.5 W*
X 598, and a second band was visible after D, which could c
be measured. On adding to this reduced fluid some canstidf
soda, at first the only change produced was the disappearanoe |

PHYSIOLOGY OF THE INVERTEBRATA. 157

of the faint band after D ; bat, after standing, the spectrum
given in Fig. 30^ I appeared, of which the bands read :
first, X623 to A 607 ; second, X 596.5 to X 579. This shows
that the Hood of these Serpuloe did not contain the same
kind of chlorocmorin as Sabella, but a pigment very closely
related to it, probably nearer to hsematin than it.''

MaoMunn has also investigated spectroscopically the gills
and opercula of Serjnda. The pigment present is allied
to, if not identical with, tetronerythrin. The use of this
pigment is not of a respiratory nature. '^ It is not unlikely
that, especially when its likeness to Kuhne's chromophanes
is taken into consideration, it may be of use in absorbing rays
of light concerned in some obscure photochemical process." *
From what has been said, it will be seen that the blood of
the Annelida contains various pigments; and that haBmo-
^obin and the lipochromes are uniformly distributed among
these animals. Krukenbergf observes : '' Chlorophane und
rhodophane tragen auch bei Wttrmern in manchen Fallen viel
ZQ einei^ lebhaften pigmentirnng bei."

(3) The Inseda. — ^Mr. E. B. Poulton, F.RS., has examined
spectroeeopically the blood of Lepidopterous larvsB and pup83.
Be nsed Zeiss' microspectroscope in these researches, which
Was found '' to be extremely delicate and convenient on all
Occasions." As a means of illumination a paraffin lamp was
at first used, ^' and it acted very well for the less refrangible

lialf of the spectrum, but in all later work bright sunlight

Was alone employed, because of its immense superiority at the

violet end."

Concerning Zeiss' and other microspectroscopes used in

researches on the chromatology of the Invertebrate blood, a

description of these instruments will be given later in the

pTesent chapter.

The greatest care is required in obtaining the blood of

uusects so as to prevent any admixture with food particles of

* QuarUrly Journal of Microscopical Science, 1885.

t OrundtUgeeiner vergl. Phytiof, d. Farhitcffe und der Farhen, 1884, p. 137.

158

PHYSIOLOGY OF THE tNVERTEBRATA.

the alimentary canal or any secretions. As the blood in
LepidopterouB larvBC exists under considerable pressure, it is
readily obtained by making a minute prick in the hypodemiis.
In larvae, Mr. I'oulton generally pricked the distal parts of
the ciaspers; and then examined a drop of the blood under
the microscope to see if any food particles were mixed with
it. The blood should be perfectly clear, containing only
colourless corpuscles, fat-cells, and minute splif-rules of fat..

The blood of pupie was obtained by making a prick in the
cuticle of the wings. The blood at once issues, being under
considerable pressure, " The whole of the blood was obtained
by pushing the abdominal segments inwards, and nltimately
by gradually increasing compression of the pupa. Owing t«
histolytic changes, the weak and tbin-walled digestive tract
is broken, and a red fluid escapes, which is mi.\ed with the
last of the blood. By carefully watching for the first appear-
ance of the red fluid, the blood may be obtained in a perfectly
pure state, exactly resembling that of the Inn-a in clearness
and in microscopic contents. The blood is received into
sections of glass tubes of various lengths, with the ends car^
fully gi-ound. One end is cemented with Dammar varnish
to a glass slide, and when the tube is filled with blood a
cover-glass is placed upon the open end, and becomes fixed
by the drying of the blood. In most cases the blood so pr^- i
pared will keep for months without change. K, however,*
air be admitted, an opaque black clot is formed on the sar-^
face, and the rest of the blood becomes cloudy. It will alao
keep indefinitely in sealed tubes."'

Mr. Poulton has examined the blood of the larvte of
Phiogophoi-ii metieulosn. These larvK assume various shadev J
of colour between green and brown. The green blood \
taken np by a capillary tube (0.75 mm. internal diameter) g
and allowed to stand four days, during which time it \
reduced to about half its volume (due to evaporation),
tube was then sealed. The spectrum produced by usi
* Froc, Hoy. Sue., vol. 38, p. aSj.

PHYSIOLOGY OF THE iNVERlEBRATA.

159

^^paraffin lamp waa tbe following: "a broad band in tbe red,
of which the extreme edges extended from 64.5-6S.5, and
when this band was best seen the violet end waa cut off at
51, and the green was darkened to 52. There was no
absorption of the red end. When the blood was fresh and
less concentrated, the blue came through on the violet side

>di the darkening at 51, thus showing a broad dark band
between this part, and the green. A more concentrated
nmple of similar blood, prepared in the same way and at
the same time, gave a darker band in the red with the same
limits, but with morr defined edges. The violet end waa
umilarly absorbed. There were indistinct traces of a broad
dim band about 59-6i-5-''

" Tbe fresh blood of another individual of the same species
which was dark greenish- brown, due to a combination of
subcuticular pigment and green blood, was examined in a
capillary tube. The compound character of the larval colour-
ing was proved by gentle pressure. The pale green blood
with a thickness of about 1 mm. gave the band in the red
from 65-68, the violet end, being completely absorbed at 45,
darkened to 51 (whea the slit was narrowed so as to render
the band distinct). A greater thickness of blood darkened
the band, and cut off the violet end at 50, darkening to 52

»(when the band was distinct). A still greater thickness
jnrodnced mon- marked results with nearly tbe same limits.
On widening the slit, no blue appeared at the absorbed end,
The dark baud now seemed to extend to 68.5. The whole
spectrum was much dimmed, but this was probably due to
tlae accidental presence of fat in the blood. In this case the
t^irkickness of Huid was 3.3 mm., and the colour was bright
^reen."

The fresh blood of a dark-brown larva {P. muticulosa) pro-

*T^ Deed a spectrum with a faint band in the red. After the

t>lood had been exposed to the air for 2i hours it became

^rown, but the spectrum was not altered.

^ The spectrum of the green fluid contents of the alimentary

lie grfBi^r

it VTTO
tken in ot^
»BOf fidM

160 PHYSIOLOGY OF THE INVERTEISRATA.

cnnal of another brown individual of the Mine aperies
a band in the red from 65.5-68.5, while the blue wbb
at 50, darkened to 52.

Poaltoa remarks that " this observation upon the
fluid from the dif^estive tract is important, because it
to identify the chlorophyil in the blood with that taken in
food. It is likely, however, that a greater thicktw
and the use of sunlight would bring out some dil
between the derived pigment dissolved in the dige&ti'
tions, and that united with a proteid in the blood
It seems quite certain that the derived pigments of the blood
and tissues are only protective, and play no further port in
the physiology of these organisms. Thus there are no
marked differences between the physiological process** of
the brown and green individuals of the same brood ia X
dimorphic species, or in the processes of a green larva,
has become brown, or j'liv ivr.srt. It seems that the pigmi
are entirely harmless, and are often retained when they
have no effect upon colour. Thus, in i'l/jo"
the blood is bright green, although the larva and popfrj
entirely opaque, while the eggs are white. It ib
that in this case the conspicuous colours — which warn eneini»
that the species is distasteful^ have been recently an)Utred,
and in consequence of the complete opacity, Ihere would b**
no advantage in losing the colour of the blood."

In the experiments just mentioned, Poulton used a par&flin
lamp as a means of illumination, but he afterwards found
that by the aid of sunlight the spectra were furtber developed.
The concentrated green blood of the larva of P. metintlosn.
when examined by sunlight, gave the spectrum represented
in Fig. 31, ap. i. "The band in the red, reaching from
64.5-68, was very black, except at the edges. When this
band was most distinct and clear, the violet end was absorbed
to 5 1, darkened to 52. On opening the slit a little, the blue
came through (though dimmed) at 48. the violet end being
absorbed at 43. When the sHt was very narrow, traces at

s atu

iilosa (green variety) ei
in a, thickness of about .75 mm. by sunlight. The blood had been allowed
(O remain in Hn open capillary lube for about four days, and was ihen sealed
op afler it had evaporaled to half ils bulk.

Sfieclmm a,— The fresh and unaltered blood of the pupa of 5. I.iguilri, examined
in a thickness of 35 mm. by sunlight.

Spectrum 3.— The (leah and unaltered blood of the pupa of P. lianphaliis.
eiatnincd in n thickness of 23 mm. by sunlight.

Sfitclritm 4-— Two tiesh calceolaria leaves, gently compressed, and examined by
niniighl.

Sfectrum 5. — Five dlllo ditto.

Sftelrum 6.— The fresh and unaltered blood of the pupa of i^ Ligiiili-i,
~ "a thickness of 3 mm. by illuminalioii from the bright sky near

^m the sun.

i62 I'HVSWLOGV OF THE INVEKTEBRATA.

another band, from 59.5-61.5, were faintly seen Tli'-

two ctief bands and the absorption of the violet end were
also Been in the blood of a living lan'a by passing the ligb'
through one of the claspers."

Poulton has also examined the blood of tbe pupte of the
J'ygani liiicephalus, Sphiiuj Liijustn, Chtcrocnmpa Elptmv,
HmtTiiithus Ocrltfitits, Smrrintktts THiee, Smerinthvs Poptdi,
DiciHinura Vinvla, PapUio Machaon, Ephyra Ihtnctaria, and
the ova of Ennomos Angvlaria, S. Tilifr, S. OcMitus, ami
SphiiLJc Liffusti-i. He has also made a comparison between
the spectra of the pigments contained in the blood of Lepi-
dopterous larvaj and pupte, and the spectra of unaltered planl
pigments (see Fig. 31).

The spectrum of the green blood of tlie pupa of P. Jfucrphnlv*
is represented in Fig. 31, sp. 3. " The characteristic band
in the red ends sharply at 71, gradually at about 64.5, paw-
ing into a lesser absorption of the red, which is continuous
with the second band, extending from about 58-60.5. bat
with very indistinct limits. When these appearances are
best seen, the violet end is completely absorbed to 52, dark-
ened to 52.5. On opening the slit a little, the dimmed bloi-
comes though from 48-42. The bond in the blue now 8bar|>ty
ends at 52, gradually at 4S. Diminishing the thickness of
the blood to 8 mm. (the previous tJiickness being 23.5 mm.l
produces nearly the same sjwctrum, the band in the red bein^
a little narrower, while tlie band at D canuot be detect*^.
On diminishing the thickness still further to 1 mm., another
band appears in the violet. The S])ectrnm is as follows :
The characteristic band from 65-70 ; the chief band of the
blue end, 48-51 ; the second band of the blue end, 45-46.75 ;
the violet being absorbed at 41. The second band of the
blue end is much fainter than the first band, and it is not
seen in a thickness of 5 mm,"

Fig. 31, sp. 2, represents the spectrum of the fresh blood
of the pupa of Sp/iin^ Ligiistri. The characteristic baud
extends from 70 to 64.5, becoming gradually continuous

]

PHYSIOLOGY OF THE l.WEKTEBRATA.

163

1^88 abaorptiou, extending to D, mi which ■' thu part
from 59-60 corresponds to the second band of the leas refran-
gible part of the s]jectram and the third band of true chloro-
phyll. The violet end is completely absorbed from 51.5,
dimmed to 52, but on widening the slit a little, blue comes
through on the violet aide of 48, but very dimly," With a
tlucknesa of 3 mm, the blood gives no absorjition of the red,
bnt shows three bands at the violet end (Fig. 31, ap, 6J.
The blood of the pupa of S. Liifusfri is a yellow colour in
those individuals which have fed upon jirivet in the larval
state, and greenish-yellow in those which have fed upon
lilac, "Com|jaring the spectra of the blood from pupie
of which the larvag had fed upon different foods, it waa found
that the liliM>fed individuals showed greater effect at the
red end than the privet-fed individuals, while the converse
waa true of the violet end. The coniparison waa made in a
thickness of about S mm. and by sonlight."

The table on p. 164 gives the sjiectra of the blood obtained
from various Lepidopteroua pupa;.

After adding absolute alcohol to the blood of the pupa of
■S fkfUatii-'i, a bright yellow solution of xanthophyll was ob-
'*ined, which gave " the characteristic apectruni (shifted to
foe violet) 49-47, 45.25-44, the violet being absorbed at

ifaolic extracts of the ova of E. Angidaria, S. TUim,
latus, a,Di SpkiiLK Liffitatri ga.ve each the spectrum of
ithophyll.

3?oulton has mode a comparison of the above results with
*oae yielded by unaltered plant pigments. In Fig, 3i,ap. 4
^^ 5, are given the spectra of two and five calceolaria* leaves
,*'>perpoaedj respectively, "Comparing these two spectra
wxtt those of y/vcii blood (Fig. 31, sp. 1, 2, and 3), the re-
»*'mblance is seen to be very great, the chief differences being
u* tte second and third bands of the red end, which are con-
Wnnoas (Pig. 31, sp. 2 and 3J, while the third is developed
^^k * The same results were ficen in the leaves of other pUmts.

i64

PHYSIOLOGY OF THE INVERTEBRATA.

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PHYSIOLOGY OF THE INVERTEBRATA. 165

re the second (Fig. 31, sp. i). Considering the chemical
ge which mast have taken place in the chlorophyll
ig digestion, rendering possible the passage of the walls
le digestive tract, and considering its chemical union with
oteid constituent of the blood, the resemblances of the
tra are very striking ; in fact, the two spectra are far
er to each other than the ordinary spectrum of chloro-
1 in alcoholic solution is to the unaltered chlorophyll of
»/'

Icoholic solutions of chlorophyll are very unstable, the
)n being that the alcohol precipitates the proteid which
orginally united to the colouring matter in the living
t or animal. Consequently, in the alcoholic solution the
3ination is no longer the same.

3th the chlorophyll and xanthophyll in caterpillars' blood
united chemically with a proteid ; hence their great
llity. The separation of these pigments from the proteid
once effected by the addition of alcohol. The former
into solution, while the latter is precipitated. The
Son of the pigments is very fugitive ; an alcoholic
ion of chlorophyll changing in a few seconds, so rapidly
acted on by light.

But while the pigments exist unchanged in the blood of
y larva3 for a long time, in other species they are entirely
royed during the comparatively short period preceding
sis, when some green larvaB become brown ; and con-
dy the pigments may appear in the blood equally suddenly,
former change must be due to an active destruction or
etion of the pigments, and is probably also accompanied
hanges in the digestive tract, whereby no more pigment
kssed through its walls. And so also the proportions of
hophyll and chlorophyll may be changed during the life
caterpillar."

rem Poulton's interesting investigations it will be observed

Lepidopterous larvas and pupse make use of a modified

rophyll^ as well as other plant pigments, derived from

r66 PHYSIOLOGY OF THE INVERTEBRATA.

their food, because of the protective * colour which thvj
acquire fram its presence in their blood nnd tisanes.

(4) TheAmc/niri^K. — Professor Ray Lanke^ter t has aho«"
that the blood of Srm'jno becomes bint; on exposure to ni'-
It contains hsDmocyanin. Tlie blood of Epcira, TrgmarU*'
and I'h<i!i:iis also contains hsemoc^'anin.

(5) The Ci-ustan(i. — Concerning the blood of the Civfiatc^^''
Genth iii 1852 first observed the bine colour of the blood *^''
LimiduK ci/r!ups; and in 1857, Professor Haeckel J obaerv^^'"
that the blue blood of ffoinnn's became, after many bouc ^
exjMSure to the air, a violet colour.

In 1873, Habuteau and Papillon § experimented on th:^''
blood of crabs, and found that it became blue in contaitf^
with air, but lost this property when submitted to the actic^ ^
of carbonic anhydride. It, however, recovered its bine coloi ^^^
on shaking with air. " Jolyet and Regnard [| showed in i8~ J
that on shaking crabs' blood with nir it showed a beautifi-^'
blue or brownish colour, according to the manner in which ^ '
was examined; it gradually loses this colour, becoming reddis^^*
and then feebly yellow ; but on treatment with pure orvge^^^
its original colour is restored. They found two coloorin^^^
matters in craba' blood: one ia blue, and is precipitated b^^^
alcohol with the albumin of the blood; the other is reddisl^ ^^
and remains in the alcoholic filtrate."

In 1 879, Dr. L(k)n Fredericq ^ proved that the blue blood <^^
Homnrtis contained hremocyonin, and that it was blue wit^^^^-"
reflected and brown with transmitted light. The blue pigmen-^ '^
— hfomocyanin — is a proteid containing copper. The red pi^""""^
ment in crabs' blood is alsio present in the blooil of Horn " rit-^^^^ "
But this pigment does not belong to the proteid constituen L-- *"*
of the blood ; it does not contain copper, iron, or maoganei

• From enemies,

+ Qaarlerly Journal nf MitTotcopinA Scitrtf, 1878, p. 453.

X MiUer't Ardiiv, 1S57. p. 511, Anm. i.

§ Oampttt-IiendM, t. 77, p. 137,

I ^rc^rirn lit FhytioUigie, 3 aine. t. 47.

^ AiJkd'na de VAeadhait Bogali de Selgigvf.

^ PHYSTOLOGY OF THE INVERTEBRATA. 167

^pncl it has nothiag to do with the chaDge in the colour of the
blood.

It may be remarked in passing that Dr. W. D. Hallibarton,
F.R.S.," has shown that tho blood plasma of ffom/'riin contams
a red pigment, which is soluble in alcohol, etber, and chloro-
form ; but it is possible that this pigment belongs to the
histohtematins which Ur. MacMunn has found to be pretty
g<'nerally distributed in the tiseaes and organs of the
Iiurrh-br"/".

The blood of Uowtiriis, Cnncrr, Cmtditiis, and Asincits does
not show any absorption bands when examined by the
microapectroscope. The blood in all these animals contMns
iiieniDCyanin,

The blood of Apiut, one of the i'lujlhpinl'i, is of a red colour,
and, according to Lankester, this colour is diii' to haemoglobin.

^^Asother Crustacean which has red or violet blood is Gam-

^HtC6) The Pdtfzoii. — Seveml of the I'oltiM" contain lipo-
^^iromes ; and in Fluxtm folUmn MacMunn t has shown
there exists a chlorophyll old pigment which is soluble in
alcohol. The spectrum of this pigment somewhat resembles
that of modified chlorophyll. The alcoholic solution is a yellow-
colour, and has a red tiuorescenco. Ita chief dark band reads
from A 68 1-5 to A 656, its darker part from \ 678 to X 662.
" It showed another before D ; the third chlorophyll band
was missing, and there was one lipochrome band."

(y) The MoUusva.—T^he blood of many Molluscs contams
the p^ment ha?mocyanin.

In 1816, Erman simply recorded the fact that the blood of
Udix was of a blue colour. Harless and \'on Bibra} (in
1847J stated that the blood of HtHx pumatio acquired a blue
cwlour on exposure, to air, but this colour was discharged by
ihaking the blood with carbonic anhydride. They also

• Brititk Sttdtfol Jovrnol. 1885.
t ProcPkniiol. 8oe.. (S87; and Qimri.
[ X HaUer't AtAxi; 1S47, p. 148.

t. vol. JO, p. 79.

168 PflYSIOLOCY OF THE INVERTEBRATA.

observed " that ammonia removed the blue colour, wliich
came back on neutralising with hydrochloric acid. They
stated 'that this bl(;>od contains copper, bet no iron ; bat
Gorup-Besanez • found iron also in its aah."

In 1858, Dr. Witting recorded in his paper, " Ueber daa
Blut einiger Crustaceen und MolliiBken,"t that the blood of
XJtiio ptffoni.ni had a slight blue tinge. Similar observations
were mode by Rongetf in 1859 on the blood of Octopui

In 1867, the late Dr. Paal Bert 5 described the blood of
Sr}na as " feebly bluish, especially in the veins of the gills.
and that it acquired a bright blue colour on exposure to
air. This colour belongs to the plasma, and ia not lost by.
boiling."

Kabuteau and Papillon|| in 1873 examined the blood
Octopus, which became bine on exposure to air. They
examined spectroscopically the blood of this animal,
arrived at the conclusion that it gives no bands. But
most remarkable paper ou the blood of Oiiopns rulgnris
that of Dr. Fredei-icq.f jniblished in 1S78. He proved that
the blood contained hH>mocyanin, and that the substance
was a proteid combined with copjwr. There is no doubt that
the blueing of the Molluscan as well as Crustacean blood ia
due to the oxidation of hiemocyanin, and that ha'mocyanin is
the carrier of oxygen within the system.

The blood of H'llx and Arioii was also shown by Fredariiii
to con tun h^mocyanin, and to give no nbaoqition
bands.

Among the Molhisca, the late Dr. Krukenberg** examined
the blood of Elalonc mosc/uita, Si-pin officiiuilisj Li/tnni

• Ltkrbmh i/er PhyiologuditA Chtiair, p, 369.

+ JavrnalJUi- Praetitehe C/ieniit, BA. 73, s. 131-132.

; JourHol de lu PhgtioUtgie, t. a, p, 66a

§ Compttt-Rtnilut, t. 65, p. 30a

I CompUi-Readia, t. 77. p. 137,

\ BvJktint de PAauliniie liable lie Belyi'iiie, 7 a^iie, t. 46

•• Verglt'idiciul-phyaiidiigUcht fftiidien, 1st Rt-ihCT 3 Abth..

« to

PHYSIOLOGY OF THE INVERTEBRATA.

'ilix. Hi-IIj- jm/ii'itiii. and HrlU

'-■"l"-

; and in all theae

he observed that the blood became blue by shaking with air
and oxy^n, and that the blue colonr disapijeared in the
presence of carbonic anhydride. Krukenberg statea that in
the blood of the three last-named Molluscs there exists a
body reri/ nfirli/ n-hiteil to, but different from, htemocyanin ;
but there ia no donbt that hseuiocyanin exiete in tlie blood of
these animals.

Krukenberg could find no htemocyanin in the blood
of Tfthys fimln'tit, Darin fubtreulata, Apiysii ilrpilans, and
PItardtn'Hiich uk.

Many years ago the blood of Aiwdmila cygiiea was
e.Taniined by Schmidt,* who described it as coloiirleas; but
the blood of this Lamellibranch contains, withoot donbt,
hfemocyanin.

L Among the Jtfo//»*-", MacMunnf has examined the blood
Helix pomatw. Heli-i- iigpcrm, J'/iluiiitKi ririj/crfi. and
rnmru^ slat/n'ilis. The blood of theae aoinials gave no
»r]ition bands when examined by the micros])eetroscope.
"The blood of //c/t/w/Jo-wiwaB found to be a bluish-white
bur by daylight, but by gaslight it had a purplish tinge;
ter twenty-four hours' standing that had disapireared, and
I was then very slighly brownish. Plxamim-d in a deep
^er, uo bands could be seen ; on treatment with ammonia,
1 bine colour persisted, and no bands came into view,
nith acetic acid the blue colour iwrsisted, and no bands
speared. After repeated filtering the blue colour remained ;
hence it can hardly have been due to jiarticles in suspension.
On treatntent with reducing agents the blue colour was lost,
*nd no bands appeared."

The blood of IfciU^ j/umnti't " assumed a distinct blue
tinge on exposure to air, and gave no absorption bands, but
absorbed a little of the violet end of the spectrum. On
■treatment with ammonia its colour was not so well t

It V.«i

irrly J„

: 1885.

I70

PHYSIOLOGY OF THE INVERTEBRATA.
it no bonds i

r reddisli tinge, but no bonds could 1
seen, nor after treatment with acetic acid, which did not
remove the colour. On treatment with ammonium solptiide
the bhie colour dieappeared, and could not be again brought
back by shaking with air for some time ; the Snid had
assumed a bronze colour, and with gaslight a faint violet tint,
but no bandB were seen."

The blood of lAmnauR staffnalis assumed a whitifih-blue
colour on exposure to air, " gave no bauds, nor after treat-
ment with ammonia, acetic acid, or ammonium sulphide; the
last discharged the colour completely, which could not be
restored on shaking with air."

The blood of PiiliuHim Heijifru " is frequently exuded
when the animal is pricked with a needle or otherwise irri-
tated, and is of a blue colour. It is quite free from bands.
Ammonia slightly diminishes the colour, but does not remove
it ; acetic acid does not remove it. With neither reagent nor
ammonium sulphide could any distinct bands be obtained."

The blood of the majority of the Molliwn contains htcmo-
cyanin, that of a few contains haemoglobin (cj., PiiuiorlfU),
while that of others, according to Krukenberg, is devoid _^^
either of these substances. ^^|

Microsprdfoseitpes. ^H

As the examination of the colouring matters of the blood
necessitates the use of a microspect rose ope, we now proceed
to describe two forms of this important instrument of re-
aeorcb.

The one need by Mr. E. B. Poulton, F.K.S., in his investi-
gations on the blood of the Lfpii^optfra is illustrated in
Fig. 32. This instrument has the slit mechanism between
the lenses. The upper achromatic lens is adjustable to the
slit; an Amici prism is placed over the eyepiece, and the
whole connected with the body by a clamping screw. The
mechanism worked by the screw F is for contracting and
expanding the slit by the symmetrical movement of botb.«

PHYSIOLOGY OF THE INVERTEBRATA. 171

edges. This opens so widely as to permit a view of the
whole visual tield. The slit la shortened by the screw H. so
that when the comparison prism ia inserted the aperture is
contracted to such an extent that the image of the object
under investigation completely fills it. There is a comparison
prism, with lateral frame and clips to hold the compared

I object and the mirror ; all these parts are fixed in a drum

= DiuiD wllh mechanhm

*n Amici prism of great dispersion, which turns aside on a
Jivot, leaving the eyepiece unobstructed for adjustment to
bn object K; the axial position of the prism is indicated
y tie spring L, which keeps it in place. A scale is projected
•oa the spectrum by means of a small scale-tube and mirror
attached to the mount of the prism. The divisions of the
scale give the wave-lengths of that section of the spectrum
«n which they fall in fractions of a micromillimetre, whereby
^B the second decimal place may be read off directly, and the

172 PHYSIOLOGY OF THE INVERTEBRATA.

third calculated by estimation. The position of the i
relative to the spectrum is adjuBted by s screw P on tie

jacket of the Amici prism,

^"ig- 33 represents Dr. Engelmann'a microspectrometer,
which is constructed on tlie principle of Vierordt's spectro«J
photometer for quantitative microspectrum analysis. IbI
place of the eyepiece, the box A is attached to the body of I

the microscope by the tube H ; it contains two indepeAdenu
conaxial, movable slits in juxtaposition, which are ■
metrically opened and closed by opposed reverse-threadeJ
screws. The width of each slit is read off on the drums 1
and T* accurately to O'OI mm,, and by estimation to
O'OOi mm. One slit is occupied by the image of the object
under investigation, and the other by light from the souroora

the souroor^H

PHVSiOLOOY or THE INVERTEBRATA.

173

of compariflon, which is brought to it by a superinipoaed
reflecting prism and lateral tube '/ with coSlimator lena,
diaphragm carrier n, and mirror S, or incandescent lamp.

In the upper opening of the box A is placed either an
eyepiece in a sliding jacket, which is accurately adjusted to
the slit ; or, instead of this (after proper adjustment of the

Image of the specimen in the objective slit) the speetroscopic
Apparatus «.'A'BC, which is fixed in the proper azimuth by
«n arresting mechaniam. This apparatus consists of the box
-A' which on one side (the upper end of «') contains a col-
limator lens /, to render parallel the cone of rays proceedinu
from the objective before they fall on a Rutherford prism P
^L.of great dispersion. By the lens t on the other side (at the

(74 PHYSIOLOGY OF THE INVERTEBRATA.

lower end of B) the parallel rays proceeding from the pi
are again brought to a focna, and this real spectmi
observed by an eyepiece L, By two slit mechanisms
right angles to each other, actuated by the screws f(',
the focal plane of the eyepiece, the visnal field can be limit
at pleasure according to tlie procedure of Vierordt.

By means of two lenses shown at 0 an image of a wavi
length scale is projected on the spectrum by reflection from"
the end-surface of the Amici prism, which is illuminat«d
the mirror S' and put out of action by closing the shutter </'
Adjnatmeut of this scale is made by inclining the whole
acale-tnbe C with the screw //■, wbicli is opposed by a counter-
spring -u (Pig. 33).

Both of these instruments are of the utmost importance fa
investigating the chromatology of the Lirrrfrbrato .

Although Dr. MacMunn ■ uses the microspectroscope,
says that, " when the amount of material is sufficient for thai
purpose, it is best to measure the position of bands by the
cht-mweU spetlivwojie and reduce the readings to wave-len^^s
by means of a curve plotted out on logarithm paper, as
directed in Watts' Index of Spcetm, Similarly, the readings
of others can be reduced to wave-lengths by laying a scale —
say of millimetres — along the top of their maps, and noting
the readings of the Fraunhofer lines, and then, by means of
an index of s]iectra (such as Watts'j, tinding the wave-lengtki
of these lines, and laying them down in accordance witli,
these data on the logarithm pa])er. One can also detect
error in the map of any observer by this method. ' So
delicate is this graphical method uf detecting error, that by
its means we might very readily detect error in table*'
of logarithms or trigonometrical functions.' In using ths
diiTraction grating it is nearly a straight line, and 8ir George
Stokes, P.R.S., says that by using the reciprocals of the-
wave-lengths instead of the numbers themselves, one has a
straight line instead of a curve."

• PnKfcdiiitji of Birmiiuiliam I'liiUuojihieiit .Siicittij, vol. 5. p. 180,

ole

the^l

PHYSIOLOGY OF THE INVERTEBRATA.

«75

Dr. MflcMunn uses in his researches three BpectroscopsB —
(i) a mi crospectro scope, (2) a Hilgers'a " Student's Kenaing-
ton Spectroscope," and (3) a large spectroscope with one
dense flint-glass prism, which is replaceable by a reflectloa
diffraction grating. Ue has curves adapted to each, so that
he can easily correct any error of observatimi by comparison.
■' The wave-length record of bands has raised the chroma-
tology of plants and animals from a state of chaos to one
which is daily assuming shape and symmetry, and we are
now beginning; to perceive relationships and the shadows of
generali!^ation3 which when made will undoubtedly be o£
great help to biology."

From the alx»ve remarks it will be seen that the spectro-
scope ia an instrument of the greatest value not only to the
chemist and physicist, but also to the biologist and physiolo-
gist. ■' Until the spectroscope was applietl to physiology no
one knew what the true colouring matter of the blood was,
and the chaotic state of medical knowledge *cith regard to
the canse of the colour of the various animal secretions
fof which survivals are still found in many text-books) is
sufficiently proved by a perusal of the older text-books, in
which one finds the pretended knowledge of the authoi"s
cloaked under the adoption of meaningless names, which
Oaay have, at the time they were written, brought conviction
Jiome to those incapable of judging for themsef ves, but which
*«Jiow us now what physiological chemistry alone could
•3<}, unaided by spectroscopic analysis, in detecting animal
I>igmenta and enabling us to follow tlieir metabolism "
^^lacMunn).

The Gases op the Blooi

^MtHlll

Tery little is known concerning the coinposit ion and nature
the gases in the blood of the Iiimrkhmta.
The author* has ascertained the approximate composition
Bdinbarijh on June 1, 1891;

PHYSIOLOGV OF THE INVERTER RATA.

Fig. 34.— AlTAKATUS FOH KXTRACTiNcl TIIK GaSKs ot THK BuxjLi.

ot the gases in the blood of certain InrL'rtebrate animals- '
The apparatus used for this purpose was that of Gantit- *"

elightly modified (Fig. 34) ; and the method allows the eoL— '

eoL-2

PHYSIOLOGY OF THE INVERTEBRATA. 177

lection of the blood in vacuo (from the time of leaving the
vein, Ac.) without any alteration in it« composition. The
glass receiver ACD (left-hand figure), in which the vacuum
is made, has a canula E fastened to its lower end. The
canula is drawn out into a fine capillary point, which is
pushed into the artery, vein, or under the hypodermis, as the
case may be. After introducing the canula into the blood
system, the tap B is opened, and the blood rises into the
receiver. The gases are evolved almost immediately, and by
means of the pump they are collected over mercury in the
tube ab^ where their composition is ascertained.

After the introduction of the blood into the receiver the
tap B is turned off; the receiver is then attached to the
pomp. Before opening the tap A, the receiver is placed in a
bath of water heated to about 40' C. The heat assists in the
liberation of the gases from the blood. Coagulation is pre-
vented by previously introducing a small quantity of sodium
cAloride xdXo the receiver {i,e,^ before the introduction of the
b/ood).*

The pump and pneumatic trough do not require description,
they are of the usual kind. The volume of the mixed
collected at ah having been ascertained, the percentage
^^ each gas is estimated by the ordinary methods of gas
^'^^Jysis. The carbonic anhydride is absorbed by potash,
[••^^ oxygen by pyrogallic acid, whilst the amount of nitrogen
^s x^presented by what remains.

(a) Blood of Sepin officinalis.

-A hundred volumes of the blood of the cuttlefish contained
*^^ following volumes of the three gases — the volumes being
^^^uced to 0° C. and 760 mm. : —

The liberation of carbonio anhydride is accelerated by preyiouslj
^^odQcing into the receiver a smaU quantity of a hot solution of tartaric

physwlogy of the jnvertf.brata.

i. 1 II-

IIL

IV. V.

V,.

Nitrogen .... 1.60 2.00

13-14
1.51

14.63 14.1 1

3ai4 »9.ia
Ml 1 1.73

14-J4

The nitrogen is simply dissolved in the blood, but th^
oxy^Q and carbonic anhydride are partly dissolved and
partly in a state of loose chemical coiubiiiation with certain
constituents of the blood. Tlie oxygen, with the h^mocyanii).
and possibly the greater part of the carbonic anhydride, ia ■
united to certain salts contained in the blood. ■

The blood was obtained from very large individuals b^-
opening the carapace, and jiassing the capillary point of tli-*^
cannltt directly into the heart.

A hundred volumes of the blood yielded the followii* 9^
volumes of oxygen, carbonic anhydride, and nitrogen t
being reduced to o C. and 760 n

PHYSIOLOGY OF THE INVERTEBRATA.

179

lygcn .

arbonic anhydride

itrogen

I.
14.62

11.
14.71

III.

14.29

IV.

■""1

14.76

3000

29.62

28.92

29.79

1.82

1.60

1.20

1-34 i

(d) Blood of Honi'iricn vnlgarU.

A hundred volumes of the blood obtained from several
"ge lobsters yielded the following results : —

■I'bonic anhydride

11.
14-81

III.

14.85

1499

31 II

28.84

29.26

1.76

1.82

1.85

itrogen

hundred volumes of the blood yielded the following
ts:—

n .

ic anhvdride

~ " 1 1 ■

- ...

II.

III.

13.33

1328

i '3.65

ZO.2^

3129

i 31.22

. 1 1.45

1.30

1.29

(/) Blood of Achnvidia atropos.

ired volumes of the blood of the larvie of this moth
le following results : —

80 PHYSIOLOGY OF THE INVERTEBRATA. ^|

^ ■

Oxygen

Carbonic an hydride

Kitrogen

16.I1
31.92
1.09

34-M ^H

^H It may be stated that the oxygen and carbonic ajifaydt^H
^H in tlie blood of the Iin-nirlirafa do not behave nciMrdinpt'^
^H the law of Dalton (the law of partial preasurea) in regaid t..
^H the absoqjtion of a mixtarp of gases by u simple fluid. .\
^H portion of each gaa combines chemically with som.- cou-
^^M Btituent or constituents of the blood. It was Magnus* vrhn
^^M first demonstrated that the oxygen and carbonic anhydrid'-
^H of the Vertebrate blood did not obey the law of Balton : and
^^M the same is true concerning the gases of the blood of the
^H Iiimirbmtti.

^^M Snrvej'ing the Iiiirrteh-ntii as a whole, we find animah
^^M like the Proioioti devoid of blood ; next, animals, as some
^H Tiriti'iCuiia and Cestouh-a, with blood devoid of corpuscles or
^^1 solid particles; then such creatures as the I'rfiiiiin/rntiat^^
^H where the blood is corpusculated. In some of these fon^H
^^1 the corpuscles merely consist of solid particles of pnm^l
^^M plasm, devoid of cell walls and nuclei; while in others the
^^M blood contains walled and nucleated corpuscles. In tlie
^H Ali/yiiqmlc the blood contains thrfe distinct corpuscles, and
duiing a portion of its course is contained in blood-vessels.
In the Crtislti'-fa the corpuscles are walled and nucleated, but
are colourless, or nearly so ; while in the Gtyhi/rca the cm^
puBcles have a limiting membrane, nucleus, and colomt^l
contents. ^H
As a mle, the colouring matter of the Invertebrate blo^^l
belongs to the plasma, and not to the corpuscles ; but there
are exceptions to this rale, which have already been alluded

• t\>(i;iri-ilorf'f Aiiimfeii, vol. 40, p. 5S3. ^^M

PHYSIOLOGY OF THE INVERTEBRATA. i8i

to in this chapter. Concerning the colouring matter itself,
it offers a greater diversity of individual pigments than the
blood of the Vtrteh^ata. In some forms we find chlorophyll
and allied pigments ; while others contain one or more of the
following pigments: — Echinochrome, chlorocruorin, heemo-
cyanin, haemoglobin, and the lipochromes.

** To contrast the various conditions of the blood corpuscles
of the Invertebrata with the stages in the development of our
own red corpuscles is not without interest. There is a time
in the history of the highest mammal when there is no
blood developed ; there is a time when only fluid blood,
destitute of corpuscles, is to be seen ; possibly our blood
corpuscles commence as minute fragments or protoplasm
derived from the digested food. These minute granules may
coalesce in the absorbent vessels and form free nuclei ; the
iiuclei may become surrounded by granules, a wall be de-
veloped on the exterior of these, and a white corpuscle (leu-
^^ocyte) would result." The colourless corpuscle, in its turn,
'^ ^mnsformed into a red corpuscle ; but the history of this
^iisformation belongs to the physiology of the Vcrtehrnta
'^ther than to that of the Invcrtrhmtn,

CHAPTER VII.

ril;Ct*LAT10N IN THE IN VKRTEBHATA.

The circulation of tbe blood in the higher animalR was di—
covered by Harvey in 1619.

In order to nourish all the parts of the body, it is oeceesark
that tbe biood should be conveyed to these parts; but tii ■
mode in which it is conveyed differs considerably in tli
lower animals. Among the InvertebrateH we find that tlir
mode of circulation becomes more and more speciabsed as
they rise in the zoological scale. From the Protozofi to the
Cixlcntmitii, the circulatory and digestive syatems are still
fused together, for they are not differentiated. In the
Echinodemi'ilii and Anuflidn we Knd the first tnie blood or
vascular system. In most worms one of the blood-vesaeU
foi-ms a pulsating tube, or so-called heart, by which the
blood is driven towards tlie j)eri]ihery of the body tbroagh
certain vessels, returning by others. In the Molluaca there
is a contractile vessel, which has a much closer resemblance
to the Vertebrate heart than the above. This heart consists
of two or three chambers ; — (") One or two auricles, which
serve for the reception of the blood, brought to them by the
veins; (/<) the ventricle which serves for the propulsion of
the blood into the ai-teries. It will be noticed from (he
above remarks that the circulatoiy system, like all othem.
was not perfected at once. Nature made numtierless
attempts, adding successively new pieces to the system, or
complicating little by little those which existed already. In
other words, the circulator)' system became more and 1

ore and mor^^

PHYSIOLOGY OF THE INVERTEIIRATA.

183

differentiated tinder the inflneiice of naturnl selection and thd
straggle for existence.

As already stated, in the lowest Invertebrates the digestive
and circulatory aystenia are not different iatfd, bat among
the higher Invertebrates these two systems liecome distinct.
The circulatory system only shapes itself after the digestive
system ; consequently one may look upon the former as an
I appendagf to the latter.

In the higher animals the blood is made to pass through
the respiratory organs in order to expose it to the oxidizing
action of the air. In certain of the lower animals thf air
penetrates into the body ; but in all the higher animals, and
in many of the lower, there exists a complex apparatus for
the circulation of the blood : (i) A system of blood-vessels to
convey the blood into the various pai-ts of the body. (2) An

I^jran (called the heart) destined to put this tluid in motion.
[oat animals, from man to the Aniirli'/", have a heart.
uric

Thk Protozoa.
Id these creatures there is no true blood, yet there is a

:uriouB foreshadowing of a circulation. In the Ehlzo^Hxla*
ly structures which may be said to have a circnlatory
function are the contractile vacuoles. The spaces are filled
with a clear fluid, and exhibit fairly regular and rhythmic
expansion and contraction (diastole and systole). During
the systoles radiating canals or vesaels extend from these
vacuoles; these widen as the vacuole lessens in diameter.
Presently the vacuole begins to expand, whilst the radiating
canals become narrower in diameter and ultimately disappear.
The contractile vacuole jierforms more than one function,
and among these Is probably that of circulation. There is a
pulsating central "organ" with conducting canals proceed-
ing therefrom . Does not this look very much like a primitive
;alatory system ?

■ The Rhizojio'la includes llie Prolo/.lattii, Funtnunlftra, flod the lUidw-

■84 FHYSIOLOGV OF THE INVERTEBRATA.

" In the Iiifiiwrifi, coDti'autile vacuoles are present. anJ
there is also a curious movemeut of the outer layer of the
sarcode in cumpany with the food vacuoles, It will br
remembered that these food vacuoles pass, aft-er quitting the
abrupt termination of the cesophagna, through the sarcode
along a ver}' definite line. They trace the outline of the in-
fusorial body as they pass along just within the contractile
layer of the animal. With them Ihe outer layer of the sar-
code is said to move."

The I*omKER.\.

In the J'ori/em or Sj>oiigiih, there is no true. blood, bnt'l
there is a circulation of water carrying food particles and
air for respiration. This circulation is brought alnut by tli«
action of cilia, which cause the cnrrents of water to t-uter
inhalent pores, and after ti-aversiqg the internal canals, finalljE
take their exit through the exhalent pores. These cun
of water containing nutritive matter act as carriers of tisst
forming materials as well as of waste products, consequently
we may regard them as representing the circulatory systt-n^-
among these Invertebrates. Although the water current* ii
the I'on/r.ra have a circulatory function, they also perforB
the functions of respiration and digestion.

The CtELENTEHATA.

inail^^l

lentiy
ystt-n^-
nt« in^

' CODi^l

In th^se animals the blood or nutritive fluid is not <
tained in any vessels, but ia free in the somatic cavity or"
enteroccele. This fluid is moved by " the contractions of th(—
body, and, generally, by cilia developed on the endodennal
lining of the enteroccele." By this means a kind of circula-
tion is constantly maintained. The movements of the body
of the animals belonging to the ''irliiilci-nla cause a move-
ment of the corpuBcuIated bloo<l in the body cavities, a flux
and reflux, a flowing and an ebbing of the nutritive fluid.
Here is the most general fonn of cii'culation. There are oOh

^^fl

PHYSIOLOGY OF THE INVERTEBRATA. 185

vessels and do epecial pumping apparatus, for the whole body
is concerned in the performance of this function. " In the
compound (jixlenitruia, this motion of the corpusculated fluid
of the body cavity affects also the fluid in those extensions of

le body cavities, throngh the common flesh or ccenosarc,
iliat place in communication the interiors of the various
Hembera of the compound animal."

^g- 35 represents the circulatory system in the ^/irfHwr.

The KCHIKODKHMATA.

All tihe Echiiwdcniiata are furnished with distinct organs
*f circulation, consisting of a " heait or corresponding organ,
tnd a complicated system of vessels. This circulatory system
consists of two vascular rings surrounding the orifice of the
ligestive tube. These rings are connected with each other,
■hey emit radiating ramifications, and one of them receives
''easels proceeding from the intestine." Such is a general
lescription of the circulatory apparatus in the £chiao(feriiiata,
ant mnce the time of Cuvier and Tiedemann " the presence
>r absence of a blood-vascular system in the Axterwkn has
seen alternately asserted and denied." The investigations of
Greef,* Hoffmann,t and TeuscherJ are in favour of "the

* itarbi'rg Silxaagiiierlchle, 1S71-2.

t XiederViiuIiirheM Arrhiv, vol. a,

\ Jtnaiidr Zeilirkrifi, vol. lo.

iB6 PHVSrOLOCV OF THE INVERTESnATA.

existence of the anal ring, and of an extensively ramified
system of canals, connected with it and with the neural
canals." But according to Prof. Huxley, " the facts, as tliey
are now known, do not appear to justify the assumption that
these canals coostitiito it distinct system of Wood-vesseW
Prof. Huxley doubts the special circntatory function of the
neural canals, and he does not consider that the ainu6 which
accompanies the mndreporic canal is in reality a heart. He
states that this sinus and canals "are mere sub- divisions of
the interval between the parietes of the body and those of

Fir., lb.-

the alimentary canal, arising from the disposition of the
anibulacral vessels and that of the walls of the peritoneal
cavity; both of which, as their development shows, are the
result of the metamorphosis of saccular diverticula of the
alimentary canal, which have encroached upon, and largely
diminished, the primitive perivisceral cavity which exists in
the embn,-o. The peritoneal cavity of the body and rays is
tilled with a watery corpusculated fluid (blood); a similar
fluid is found in the ambulacral vessels, and probably fills
the canals."

Fig. 36 represents the circulatory system in Erhin

I*' In the TnrbcUai-in, Tri-mniotln, and Ci'stoiilen, the lacnnip
the mesoderm and the interstitial flnid of its tissoes are
the only represent ativea of a blood-vascular aysteiii. It is
probable that these commnnicate directly with the terminal
ramifications of the water-vascnlar (respiratory) syatem. In
the i'l'l i/i-rii., a spacious perivisceral cavity sejiarates the
mesoderm into two layers, the splanchnopleiire, which forms
the enderon of the alimentary canal, and the somatopleure,
arhich constitutes the enderon of the integument. The ter-
BiDations of the water vessels open into this cavity.""

TirE AsNELinA.
In the Anndida there is a ijerlvisceral cavity (perienteric
:e) communicating with the segmental or excretory organs,
'his ea\ity contains a colourless flnid consisting of a coagnl-
ile albuminous plasma and numerous colourless cor^luscles.
'The perivisceral fluid is not only nutritive, but acts as a
liquid fulcrum to the muscular movements of the body. If
this Hnid is let out the power of voluntary motion is lost.
It has been stated that "the vermicular motions of the
itestine are aided or determined by its resistance and
ipport; it favours circnlation by obviating the pressure
Upon the blood-vesseis, which follow the contact of the
intestine with the integument, and is, perhaps, the source,
or one of the sources, of the blood itself." This fluid con-
tains albumin, fibrin, and certain salts. In addition to the
peri^'isceral cavity and its Huid, there is in most of the
AnHcliiffi a system of vessels with <ontriu-til<:.-w&[\i. These
lis, known as the pseudo-htomal system, are filh-d with a
id, which may be red or green, and corpusculated or non-
irpusculated. In some Annelids the pseudo-htemal system
iimunicates with the perivisceral cavity ; but in the majority
these animals it is shut off from it.

• Hoxlefs A-ialomi, ,>/ hrerteln-ata. p. $7-

PffVSfOr.OGV OF THE INVERTEFRATA. 187

The TiiKHOscoLicES,

^M r8S PHyS/OtOGV OF THE INVERTEBRATA. H

^H Professor

Hnxh-y considers that the perivisceral Hiiid ^|

^H represents ordinary blood &8 fat' as being a carrier of mdn' ^|

^H mmd to the

tissues ; and that the pseado-hiemal flaid is ^H

■

LilJ^

IP*

^^H ra

sll

^^^^^B ■

-i,'

.IJ'I-

i ^a^l ■

1HH<«

', ^^^^^^^^^ ^ ^^M

.■:

^^^^^u^^SkL ^ 1 1 '• V

^^^^^^H - ^^"-^

gjH

^^^p jyt^H"' t = i|.

^^H

mS!C!9^^%Cmf 1 i 1 ! H

•^-ipM"

^H^^HHM^^^^r \ ^ a v-^ ^L ^H

^8^

' HiPS

S"! ^1^1

^^^H

^^H vl

°l;i9

^^^I^B J^V

e ^^1

^HET ^^,

■

^1 probably only engaged in the fuuction of respiration ; heiica^|

^1 the reason that he calls it '' respiratoi? blood." ^H

H After these general remarks we proceed to detail at lengthi^H

^K the pseiido-htemal systems of li'mhi-ir-m and HirvJo. ^|

■

mhririLn, there are three principal vessels which ^|

PHYSIOLOGY OF THE INVERTEBRATA. 189

traverse the body in a longitudinal direction (Fig. 37, a, b,

C, D).

The dorsal or supra-intestinal vessel is situated on the
dorsal side of the alimentary canal. The supra-neural or
sab-intestinal vessel is situated along the ventral side of the
alimentary canal ; and the sub-neural vessel lies directly
beneath the great ventral ganglionic nerve cord. Besides
the three principal vessels, there are two lateral neural
vessels situated on either side of the nerve (Fig. 37, b). The
dorsal vessel (which is contractile, and consequently drives
the blood fh)m behind forward) is connected with the supra-
neural vessel in nearly every segment by pairs of transverse
vessels — i.e., one vessel on each side of the body connects the
dorsal to the ventral trunk.

In the anterior portion of the body the longitudinal vessels
break up into a blood plexus, consequently in this region (t.r.,
first seven segments) there are no distinct transverse vessels.
Between the seventh and tenth segments, the dorsal vessel
becomes dilated into what is known as the *' hearts " of
Lumhricus. These " hearts " contract so as to force the blood
from the dorsal to the ventral side of the body. The dorsal
vessel also sends out branches to the body wall, mesenteries,
and to the walls of the alimentary canal. The supra-neural
vessel sends out branches to the nervous system, and also
transverse vessels which unite with the sub-neural trunk
(Rg. 37, d). Certain transverse vessels also unite the dorsal
to the sub-neural vessel ; these vessels supply the segmental
organs and integument with blood.

(6) The body or perivisceral cavity in Hirmlo is only im-
perfectly differentiated from the vascular system. It is filled
with loose connective tissue in which are dorsal, ventral, and
lateral spaces (sinuses) containing blood.

The vascular system (Fig. 38) consists of a ventral blood-
vessel or sinus, and two wide lateral vessels which run along
the sides of the body. There is also a median dorsal vessel.
All these vessels anastomose with each other, and send off

190 PHYSIOLOGY OF THE INVERT EBRATA.

branches which also anastomose and give rise to a fine net-
work of blood-vessels situated on the organs of generatioD,
nephridift, and in the muscular mesodermic layer. The red
blood contained in these vessels has already been described.

Ill the PoiiicluEta the perivisceral cavity is continued into
all the important appendages of the body, consequently tioy
are filled with blood, '■ The circulation of this fluid i
efl'ected partly by the contraction of the body and i
appendages, partly by the vibratile cilia, with which a greani

or less extent of the walls of the perivisceral cavity is covere
In a great number of Poli/r/ift/n no part of the body i
specially adapted to perform the function of respiration, i
at'ration of the biood probably t-aking place wherever the
integument is sufficiently thin ; and, even when distinct
branchise ordinarily exist, members of the same family may
be deprived of them."

PHYSIOLOGY OF THE I.WERTEURATA.

1.JI

111 mauy uf the Pol n'-lutia^ the |)aemlo-lia?mal system is
entirely absent (f.;/,, Fuhiiuit s'jiininntii), while in others it
varies greatly in the arrangement of the principal vessels;
" bat they commonly consist of oae or two principal longitu-
dinal dorsal and ventral vessels, which are connect*^ in each
somite by transvei-se branches. Where branchiaa exist,
loops or processes of one or other of the great trunks enter
them." The dorsal and ventral vessels are generally con-
tractile ; and the direction of the contractions " is usually such
that the blood is prope.Ued from behind forwards in the dorsal
vessel, and in theopt)osite direction in the ventral vessel ; but
the course which it pursues in the lateral trunks is probably
^krery irregular."

The Arthroi'Oda.

The various classes belonging to the Adhmjio'lit present a
syst*-ra of vessels, partially at least, shut off from the somatic
or body cavity. But the blood-vascular system is not com-
plete in any Invertebrate animal. In some part or parts of
the body the vessels will be found to terminate, and the blood
will flow through lacume or spaces not bounded by any
limiting membrane. From this remark it will be observed
that the old form of circulation once more comes uppermost —
I.'., the blood passes into the general body cavity. This
primitive form of circulation is met with in all Invertebrates,
bnt the higher forma have partially developed a system of
blood-vessels, which is, however, incomplete, consequently the
lower the aaimal, the more extensive is the lacunar circulation.

In the I/nrrUbriili', the arteries have not the three coats,
such as are met with in the higher animals. The heart is
generally situated in a dorsal |Kisition ; and its pulsations drive
the blood at once over the body generally, and not to the
organs of respiration iirst. "The word 'pericardium,' used
hy some writers in describing the blood systems of the Iiivcr-
Ifbytit'i, is an unfortunate and a misleading one. The

Cm of the Iiistda and Crastiwat has no homology

192

PHVSIOLOCY OF THE INVERTEBRATA.

with the serous raemlirane, that invests the heart of t
Vertebrate animals. It is, in truth, a large venous sinflj
surrounding that long seginpnted vessel in the dorsal regi
of the body that is generally called thfi heart. From this
sinus, blood passes into the heart by certain lateral openings
provided with valvfs opening iuwai-d&. Yet another unfor-
tunate name has been used in this connection, f 'ertain parU
of the venous system in the Iiinertu smA Mifrinpoiltt have beep
designated portal. They represent, however, in no manner
the portal system peculiar to the Vnifhrntij."

In the Arthropiuhi, there are no pseudo-ha;mal vessels ; and
"the blood- vascular system varies from a mere perivisceral
cavity without any heart. (Ostnuvil-i, CiiTijiali'i) up to a
complete, usually many-chambered heart with well-developed
arterial vessels. The venous channels, however, always have
the nature of, more or less, definite lacunas. The blood cor-
puscles are colourless, nucleated cells."*

In all those Arthropods where a heart is present, the blood
returns to that organ by the lacunar spaces situated betweei:
the organs. These conduits, without 5])ecial walls, debouch
into ft so-called pericardiacal reyi.'r\-oir, and the blood pen(^
trates afterwards into the heart by cardiacal clefts. In the
£i-'ii-ki/ura and Murroiu-n (Fig. 39) the blood, before retnming
to the heart, is o.xidised in passing throagh the brancliia.\

In the Mi/Tinj>0'!ti, the heart has many chambers, and it ts
nearly as long as the body. The blood enters this organ by
a pair of clefts, and leaves it partly by the communication
with the adjacent chamber, and partly bythn lateral arteries.
" A median aortic trunk continues the heart forwards, and the
lateral trunks encircle the (esophagus and unite into an artery
which lies upon the ganglionic chain. The arterial system
in the ChilojHxhf ia, in fact, as complete as that of the
Scorpion s."t

In the Iitsfdd, circulation is chleflv effected by means (

• Huilej's AHOtooty of On Iiircr
t See Newport in the I'lillotophk

rbraia, p. Jji.

it TraifurlioKii of thr h'o'jal Soei'lj/.

PHYSIOLOGY OF THE INVERTEBRATA. 193.

*e heart, which is a tubular organ running along the back of
'lie insect, and hence called the dorsal vessel (Fig. 40). This

la wormed of a Beries of sacs opening one into the other, from
J~^d forwards, in Bach a manner that the folds formed by
B^jonction of the sacs serve as valves to prevent the reflux

194

PHYStOLOCY OF THE INVERTEBRATA.

of the blood. The blood enters the heart from the cavity of

the body by a seripsof valvular open in^rs, when it is gradaally
driven forwards by the successive contraction of the dirisious
of the hfart, until it escapes in the ni.'ighbourhood of the
head. After this it is no longer confined within vessels, ai
neither artenes nor veins have been observed in the /w*rfi.-

a = dorsal vesspl or hean. f - principal Interal currenli.

but the blood or nourishing fluid is spread abont in th» «*^'
lacuna; and interstices of tlie organs. Even in these lacuna^-***
the blood is still animated by the action of the heart, and IM '
ultimately forced back until it again reaches that oi^aa':*-^*''
These lacuna? all communicate with a sinus or vessel on th' «J-^
ventral side of the body. Thence the blood passes to th* *^-^
respiratory organs, and tlien to the so-called pericardium o*^* °
venous pinus surrounding the heart..

It may be mentioned that in the Lq>Uloptern, Orlkojitfifmr'^'"^'^
&c., a ventral vessel has been observed. Dr. \'. Graber^" "*"
discovered a ventral vessel in Sldhtirphyinn grosstim {gns^^*^^
hopper) and various species of lAM/vIa, and states that (
should be regarded in the light of an artery to a dorsal veui~
• Die ItuecttH, 1877, vol. i, pp. JJ8-34S.

PHYSIOLOGY OF THE INVERTEBRATA. 195

Mr. A. H. Swinton* has also observed a ventral vessel
(Fig. 41) beneath the intestines in SpJiitix Lujustn, This
vessel is contractile like the dorsal vessel, and unites with the
latter at the junction of the thorax witli the abdomen. At
this junction there is a dilatation of a flat-roundish form.
Swinton states that there is a twofold alternating pulsation
in this dilatation, that indicated a circular flow of the fluid,

A ^^

^ — -- — -r^:^^ Darsdt vessely n

Fig. 41. — Circulation in the Abuomkn of Sphinx.

{After Swinton.)

A = heart. B = dorsal vessel. C = ventral vessel, a = aiferents.

S = intestines. / = tracheae.

as shown by the double-headed arrows (Fig. 41) ; and which
appears to be a rudimentary heart, composed of an auricle
and a ventricle, such as exists in the Mollusca,

The two main vessels have, besides, several aiferents, a, a,
and those to the lower one seemed to open each time the flap
or fold spasmodically moves upwards ; while a central cylin-
drical duct (B) passes from the heart (A) ventrally into the
thorax, where its rhythmical action, says Mr. Swinton, " could
be at intervals seen extending as far as the second annulation,
although the forms of its vessels were obscured, from the fact
that circulation was already partially stayed in this position
of the body. Lastly, the ventral and flat-roundish vessels
continued to palpitate vigorously long after the valves of
the dorsal vessel had ceased to move." Mr. Swinton considers
that he has discovered, in this pulsating flat-roundish vessel
^uid its afEerents, the tirwe heart in the Lcpidoptera,

* liueet Variety: iU Propagation and DutribiUio/ij 1880, p. 39.

196

PHYSIOLOGY OF THE INVERTEBRA7 A.

The Amchnida (pulmonary) have a circulatory apparatus,
which is to a certain extent well developed. The hean
(Fig. 42), situated doi-sally, has the form of an elongalvil
vessel, and gives rise to varions art--
ries. The blood ha^nng traversed Ih.'
organs, passes to thelnngs, and from
thence reaches the heart, following a
course similar to that observed in iV
C-nis/'tcn', In those Armhnifhi v
breathe only by trachere (f-ij.,
mites), the circulator)- apparatus
rudimentary ; for there appears to %
merely a simple dorsal vessel '
arteries or veins : and it may be I
marked, that in some species the hea
or dorsal vessel ap(iears to be entiit
wanting.

Hf.akt UK A .Si'mr.H. In some of the lower CnifJorrT

a = abdomen, i = lateral the heart is entirely absent. For in-

pulmooaryveMel,. f^anle- ^^ j^ ^^^ Cop<-p,»h, there is HO

nor aorta. d = transverse

branches, c = genila] arteries, heart ; while m the OstriHOtlli there IS -
either no heart {Cifpns and Cylhrn). -
or it is only in a rndimentary form. Accordinif to ■■
Claus, the heart in Cifpriifi/itt, Ilalooypliit, and Ctme/iariv ^
consists only of a short saccular organ with one anterior oiid -t
two lateral appendages. The Cirfijietlia have no heart i
other circulatory apparatus — that is, as far as is known ]
the present state of biological science.

Dt. G. 0. Sara" has recently investigated the circulat
apparatus in Ci/cliff/in-iti hislojii (set- Fig. 11), one of the
Phylli.ipoilfi. The heart of this Phyllopod is located in th^S
dorsal part of the body, and is easily observed in Iivin{^^
specimens through the transparent shell. It has th*^
form of an elongated tube traversing no less than ibii::^^;
segments of the body, viz., the maxillaiy segment and t
• Chrittiania Videmkabi-StUlmbi Forlianillinyer, 1887,

iidt^H

PHYSIOLOGY OF THE INVERTEBRATA. 197

three first segments of the trunk, its posterior part being,
moreover, extended to the middle of the succeeding segment,
and its anterior extremity slightly projected within the man-
dibular segment. It is provided with four pairs of distinctly
defined lateral valvular openings, eacli pair occurring exactly
in the middle of the corresponding segment. Here, the
heart is connected to the body wall by slender fibres, the
intervening parts being slightly instricted, whereby the
dorsal as well as the lateral edges of the heart acquire a
regular undulated appearance. The heart of Cyclcstheria has
its greatest width across the anterior part, located within the
dorsal prolongation of the cervical division, whence it tapers
somewhat posteriorly. Its posterior extremity is abruptly
truncated and furnished with a rather wide medial opening,
whereas the anterior extremity contracts to a short aorta
tipough which the blood introduced into the heart is
©spelled. The lateral openings of the heart are each
sMrrounded by delicate concentric muscular fibres, and
-'^"xnited by two distinctly defined valvular lips. Likewise at
^-ho posterior extremity of the heart a valvular arrangement
^''^Qxald seem to occur, and the origin of the aorta is marked
pff* by two narrow lips closing and opening at regular
^^-^rvals. Of any other distinctly defined blood-vessels,
^^"^ Sars could not find any trace, the blood circulating
_*^*-^j)ly within the lacunar interstices between the muscles
the connective tissues. In the shell, .these lacunar
rstices have a very complicated arrangement, forming a
^^J:ily anastomosing network of what Dr. Sars calls **blood-
Xns." Along the dorsal line, however, the presence of a
^^ll-defined longitudinal blood-sinus may be readily de-
^ ruined.
llTie blood of Cyclesthcmi is colourless, and contains
Xneroos small rounded corpuscles, the course of which may
t:raoed with comparative ease, especially in young trans-
it specimens. By the contraction of the heart (about
^ So per minute) the blood is expelled exclusively from its

»g8 PHYSIOLOGY OF THE im'ERTEnnATA.

anterior extremity, whicli is prolonged so as to form a short
aorta, which has at its base a valvular apparatus. This
apparatus opens and closes at ivgular intervals. On leaving
the open end of the aorta, the blood tlows in two different
directions, one part anteriorly, the other poeterioriy. The
considerable quantity of blood condnctJ'd to the anterior part
of tho body is seen to flow down the sides of the head, partly
snppij'ing its several appendages, partly rnoning strwght
buck along its ventral side to the region of tho adductor
muscle of the shell. Here the blood enters the valves, being
received within the complicated system of canals occurring
between their two lamellae. The other principal arterial cur-
rent is seen running from the heart backwards along the
dorsal side of the trunk, immediately above the intestine;.
ami, on reacliing the tail, it bends round and Hows anteriorlj
along the ventral side, sending off, in each segment, lateraB
currents to the branchial legs. The blood thus conducted Vr z
the various parts of the body and shell returns to the bearV
by two different ways. The considerable quantity of bloou^*3"
introduced within the canal-system of the shell is at lasf-^g-*^
received by two longitudinal sinuses passing along its dorsa^^s^*
side, the anterior rather short, the posterior occupying th» *»'
greater part of the dorsal line. In the anterior sinns th» m:^"
blood flows backward, iu the posterior, forwai-d ; the tw*"^"^"
currents meeting at tlie place where the body is connecte*-^^-^
with the shell dorsally. Here both currents saddenly benw*^''
down, the one on the anterior, the other on the posterior sid^*^
and pour out the blood into the pericaixlial sinus, whence i* *^
passes info the heart through the lateral valvular opening^r'^^S
The remaining part of the blood, introduced into the trun' «"*'*'
and the tail, is at last received within a large sinus, occupj^l*^-
iug the upper part of the dorsal side of the trunk aii*'^*'^"
divided from the arterial dorsal sinus by a longitodin* -*^^*"
ligament extending from the lower side of the heart to tl^"^^^^
tail. This blood-sinus is apparently fed in each segment — "
the trunk by a pair of ascending currents troin the branclir' ^-«

PHYSIOLOGY OF THE INVERTEBRATA.

199

The blood contained in the above-mentioned sinus
W6 from behind forward, or in an opposite direction to
lat contained in the ni'teiial sinus, and for the most part is
jtroduced into the heart through its posterior extremity,
lOugh soiii-- would also seem to enter the posterior pair of
B lateral valvular openings.

i says that the coiii-se of the blood within the eeveral
Uibs is not easy to examine in Cydesthmn hislopi, for they
L- limbs) are concealed for the greater part by the shell,
■in the antennie, however, which at times are more or leas
completely exserted beyond the shell, the blood can be dis-
tinctly seen passing along the upper edge of each brancb to
the extremity, then turning
round, and Hewing back along
the lower edge to the scape
[|(8ar3).
, In the higher Crudacm, the
mrt and circulatory appa-
itus are far better deiined
! in the lower orders of
s class. ITie heart of Ho-
is a powerful quadrate
organ, and the arteries are
i&nite in nnmbtr and
distribution. There are
ntractile expansions (" gill-
,") at the base of the
blood-vessels conducting the

blood to the branchial. The heart consists of a single con-
tractile cavity, and the arteries in the higher Ci-itstami are
i tubes; but the venous blood passes back through the
btterstict-s between the organs of the body, until it reaches
Eiin cavities or reservoirs situated at the bases of the limbs
JFig. 43); therefore the venous blood bathes al! the organs.
a the reservoirs or sinuses the blood passes to the bran-
r, where it becomes ai' rated by contact nitli the water,

= vessels which collect Ilie

Htraled blood rrom gilK c = •
conducting venous blood to
rf = heart, c = carapace. / —
chiocarfiflc vessels. £ = ste

Kills.

3O0 PHYSIOLOGY OF THE TNVERTESRATA. '

nnd then passes through proper vessels to thp heart. It
will be seen that the circulation in the higher fonns is semi-
vascular and seiiii-lacuiiar.

The circulatory apparatus of AsCacus is well defined. The
heart is situated dorsally aud behind the stomach. It ia
surrounded by the so-called pericardium, which is in reality a
hlood-sinuE ; consequently the heart is suspended in a blood-
sinus. There are six apert,ures in this organ provided with
valves which open inwards. These allow the blood to enter
the heart during the diastole, and prevent its egress, except
by the arteries, during the systole. There are six arterial
trunks providetl with valves at their commencement, their
object being to prevent the regnrgitation of the blood.
These arteries ramify minutely, but the capillary system has
not been investigated with anything like satisfaction. So
far as is known, the blood passes from the arteries into the
lacuntD and into the perivisceral cavity. From these lacanie
it ultimately finds its way to the branchiaj and heart.

Reverting once more to the heart of the Cnistafai, Sir
Itichard Owen, F.R.S., pays that " we may trace in the heart
of these animals a gradational series of forms, from the
elongated median dorsal vessel of LiMulm, to the short,
broad, and compact muscular ventricle in the lobster and the
crab. In ail the Cru«tm:iM the heart is situated immediately
beneath the skin of the back, above the intestinal tube, and
ia retained in aihi by lateral pyramidal muscles,

" In the Eiilom<'dmi:a* and in the lower, elongated, slender,
many-jointed species of the Edriophthalmous CnnUiicfri, the
heart presents its vasiform character. It is broadest and
moet compact in the crab."

The Poi-YzoA.
The perivisceral cavity contains a nutritive Ihiid. This is
kept in constant motion by the action of cilia with which the
" The hutomo*irafa include the Pki/llajiO'la, Cladottra, Oaf rocoifa, and lb«

PHYSIOLOGY OF THE INVERTEBRATA. 201

inner snrface of the cavity and the outer surface of the
intestine are covered. This movement, which extends into
the tube of the common stock, is equivalent to a true circu-
lation of the blood. Consequently, the function of circulation
in these animals is comparable to that in the Coelenterata,
for the blood is not, during any part of its course, contained
in any system of vessels, but is free in the body cavity.

The Brachiopoda.

The sinuses met with in the Bmehiopoda are the result of
partial limitation of the general cavity of the body, for a
special purpose. These sinuses " extend into each lobe of
the mantle, and end caecally at its margins. The lobes of
the mantle are probably, together with the ciliated tentacula,
the seat of the respiratory function. The sinuses of the
pallial lobes of Lin/jida give rise to numerous highly con-
tractile, teat-like processes, or ampullae. During life the
circulating fluid can be seen rapidly coursing into and out
of each ampulla in turn."

Between the ectoderm and the lining membrane of the
sinus-like ^'prolongations of the perivisceral cavity in the
mantle, and between the endoderm, the ectoderm, and the
lining membrane of the perivisceral cavity itself, there is an
interspace, broken up into many anastomosing canals," which
Prof. Huxley considers, *'to represent a large part of the
proper blood systems." Dilatations of these canals have been
erroneously described as hearts, but they are not contractile.
" Although the existence of a direct communication between
the perivisceral chamber and the blood canals has not been
demonstrated, it is very probable that the perivisceral chamber
really forms part of the blood-vascular system."

The Mollusca.

In the Mollusca the circulatory system is more highly
diflferentiated, and *' in very many, if not all, the blood cavities

202 PHYSIOLOGY OF THE INVERTEBRATA.

communicate directly with the erterior by the organs (
Bojanus," or kidneys. The higher Mo\lu»ca have all of them
well-defined hearts, generally with auricles and ventricles
(Fig. 44), arteries and veins, though the capillary system is
still absent. The hearts of the Gnstcivpodn and C<ph'ifii/ioi
have valves and coliininiu camre ; there are also contract
expansions at the base of the vessels conducting the blood I
the branchiae.

We now describe the circulatory system in three orders d
the Mo/h'j

1 = pan of dorsal Imnk of a worm, t — hear! of .VnHli/us. 3 = licail of

a Lam ell i branch. 4 = hear! of Oclafm. 6 = heart or a GaMoopod,

V — venlricle. a — auricle. * - ceplmlic arlery. c = abdominal taUrtj.

The arrows indicate (he direction of the blood'CurrenL ■

(i) The Lttviellihranehiala. — ^The vascular Bystem consists
of a heart, anterior and posterior aortse, and other blood-
vessels and sinuses. In Aiiodm'ta the heart lies in the
middle line of the lx)dy, and is surrounded by the pericardinra
or blood sinus. It consists of a median ventricle, which is
perforated by the intestine (see Fig. i8), and of two auricles
which are situated on each aide of the ventricle. Thi"
ventricle gives rise to the anterior and posterior aortie.
The auricles are muscular sacs, and comiuunicate with the
ventricle by the auriculo-ventricular openinj^

PHYSIOLOGY OF THE INVERTEBRATA. 103

ings are each provided with a pair of valves, which project
into the ventricle, and there meet in fivnt of the openings.
These v&lvea allow the hlood to pasa from the anricle to the
ventricle, bat prevent its retnm from the ventricle to the
anricle. By the contraction of the auricles the blood is
forced into the ventricle. After the contraction of the
anricles have ceased, the ventricle contracts and forces the
Uood forwards and backwards throngh the two aortce. The
blood passes through the ramihcations of these vessels into
tiie ^stem of lacuna; or sinuses situated In the mantle and
Iwtween the viscera. From these lacunse the blood passes

a = heart. b = vesKls carrying blood from lung (o heart, f = lung,
rf =! aorta, t — gastric artery. / = " hepatic " artery. g = pedal
artery. h = abdominal cavity, supplying the place of a venous sinus,
(■ = irregular canal communicating with A, and carrying blood to lung.

*-5ito a large median venous sinus termed the vena cava,
'^hich extends between the anterior and posterior adductor
^Qscles. At the base of the branchiae are two lateral sinuses.
TThe main portion of the blood passes into the renal oi^an
^tbe organ of Bojanus) and ultimately to the branchite, and
from thence is returned as arterial blood to the auricular
portion of the heart.

(2) The Oasteropoda. — In Hiiiv the heart (Fig, 45) is

304 PHYSIOLOGY OF THE JNVERTEBRATA.

close to the pulmonary sac. It consists of au auricle and
a vt'iitricle. The aorta proceeds from the ventricle, and
divides into two branches : one of these passes forward and
ramiiieB in the head and foot, while the other passes back-
wards and dorsally to the viscera, where it also ramifift
The arterial branches terminate by openini^ into lacnnic;
from these the blood iiassea through the pulmonary arteries I
to the lung, and thence through the pulmonary veins, which I
ultimately join to form a large pulmonary vein which leads |
into the auricle. The organ of Bojanos, or kidney, "
close to the pulniohaiy sac in the course of the current of thB |
returning blood."

Fig. 46.— Bux>ii

(3) The Crjih'thixiilii. — The circulatory systeid of Sepia il
seen in Fig. 46. " The heart is placed uixin the |x>st«rior faca I
of the body, on the hfemal side of the intestine, and receives!
the blood by branch io-cardiac vessels, which correspond ia-J
number with the gills ; and, as they are contractile, might bs4
regarded aa auricles. The gills themselves have no cilia, anA I

PHYSIOLOGY OF THE INVERTEBRATA. 205

are, in some cases, if not always, contractile. The arteries
end in an extensively developed capillary system, but the
venous channels retain, to a greater or less extent, the charac-
ter of sinuses. The venous blood, on its way back to the
heart, is gathered into a large longitudinal sinus — ^the vena
cava — ^which lies on the posterior face of the body, close to
the anterior wall of the branchial chamber, and divides into
as many afiEerent branchial vessels as there are gills. Each
of these vessels traverses a chamber, which communicates
directly with the mantle cavity, and the wall of the vessel,
which comes into contact with the water in this chamber, is
sacculated and glandular." In Loligo media ^^ the sacculated
afferent veins and branchial hearts contract about sixty
times a minute. The pulsations of these veins and of the
branchial hearts are not synchronous. The branchial veins
and the lamellse of the branchisB also contract rhythmically,"
but the branchial arteries do not contract. " The portion of
the branchial vein which lies between the base of the gill and
the systemic ventricle is very short, and it is hard to say
whether it contracts independently or not. Mechanical
irritation causes contraction both of the afferent branchial
Veins and of the branchial hearts." (Huxley.)

In Medcme cin^hosus Professor Huxley has "observed vegn-
^^T rhythmical contractions of the vena cava itself, as well
^id of its divisions, the sacculated afferent branchial veins, of
^ixe branchial hearts, and of the branchio-cardiac vessels."

The Tunicata.

In the Ascidians the function of circulation differs entirely
m other Invertebrates. The peculiarity of this circulation
the reversal at regular intervals of the direction of the
lt>lood current. The heart is devoid of valves, and contracts
ith a wave-like movement. If the wave is from below
pwards, "the blood passes into an abdominal vessel, thence
ifeto transverse ascending canals that lead to the extraordinary

2o6 PHYSIOLOGY OF THE IXVERTEBRATA.

network of vessels connected with tlie reapirutory structures,
into a doraal vessel, and thence by a eomiect.ing branch I»
the posterior end of the heurt, Aft^r a ctrt-ain period, the—'*
wave of contraction through the heart, and the course of the— —
blood, are generally reversed in direction: and the blood .^B
now flows from the ventral heart into the dorsal vessel, down -^

through the branching network into the abdominal or yen-

tral vessel, and so to the anterior end of the heart."

The blood consists of a clear plasma containing colon rlesn g?"-*
corpuscles.

In Appi'niliculari't flahdlvm. Professor Huxley states tbsc*'-«0
there are no corpuscles, and " the direction of the |iiiliiiiliiiiii ii *ii
of the heart is not reversed at intervals, as it is in tJie5» .mi
Ascidians in general. M. Fol,' however, states that, in other^z-^si
Appeiidwularia- the reversal of the contractions of the beiu-LV "'-^

takes place There are no distinct vessels, bnt th^^ "e

colourless fluid which takes the place of blood makes its w»>^^^-r
through the interspaces between the ectoderm and endoderm
and the various viscera,"

Concerning the velocity of the circulation in the Invalt
hri'ta very little is known ; but it may be stated that tiia
blood ill these animals is animated by a Tiiuch slower i
nii.-nt of translation than occurs in the V-rfrhnil't.

■ 87i.

CHAPTER VIII.

RESPIRATION IN THE INVERTEBRATA.

It is well known that the presence and absorption of oxygen
is essential to the life of every tissue, and that one of the
prodncts of the action of oxygen on the tissues, «&o., is the
production of carbonic anhydride, a gas which is inimical to
life. Even the lowest members of the animal kingdom re-
quire oxygen — without oxygen, no animal life. The Amosba
and Paramceciiim, when introduced into a medium contain-
ing no oxygen, or containing an excess of carbonic anhydride,
Very soon die. In all animals there is an interchange be-
tween the gases of the organism and the gases of the medium
ixi which they live ; and this interchange, which is known as
Respiration, is continuous throughout life.

In the lowest forms no special mechanism is necessary for
facilitating the gaseous interchange ; for they absorb fluids
cx>ntaining oxygen in solution. In higher forms, canals,
^.long which the air passes, seem to be necessary ; and in still
Ixigher forms respiration is performed by the movement of
"tilie branchia?, or by tracheae (air-tubes) and lungs. The
c^l>8orption or respiration of oxygen is one of the first con-
ditions of nutrition. All organised beings absorb oxygen,
^oid this absorption goes on in all stages of the existence of
living matter.

The organs (using the word in its widest sense) of respira-
t^ion differ considerably in different animals, but they have
^U the same physiological function to perform — that of sup-
plying oxygen to the tissues and blood ; and the elimination

3oS PHYSIOLOGY OF THE INVERTEBRATA.

ul the gaseous products of decay. In fact we may deline
respiration as ''the elimination of the gaseous products of
tiasue-combustion, and the introduction of the oxygen neces-
sary for that combustion."

Tlie lower forma of the animal kingdom respire directly by
changes between the geuiTal surface of the body and thi-
mudium in which they live; but in the higher forms, respira-
tion is a twofold process: (") internal respiration, or the —
interchanges between the gases of the blood and the tissues ; .^■,
and (h) external respiration, or the interchanges between the -^^

gases of the blood and tlie gases in the air-cells of the lungs. ».

These interchanges, however, are not always confined to the -t^^^e
lungs; thus there is a trne outaupous respiration in the^^..*
fikin, an intestinal respiration in the intestine.s, and mosti*^3t.
probably interchanges of alike nature take place in otherrw^r
organs; for it may be remarked that many organs of the^»-"e

Invei-lebnila contain varions pigments, which have a res -=^^-

piratory function.

The respiratory apparatus is always in intimate relatiooK^^^ "
with the organs of circulation.

The Pro'cozoa.

In most of the I'rotuznn, respiration takes place all ovei
the general surface of the body ; but these animals differ
somewhat in the mechanism of respiration. In thf
(frrn'irinulfr the interchange of gases takes place all over the
body. In the majority of the In/iisorvj and Jthizojwtia then-
is a differentiation of the function of respiration, for even in
these low forms the interchange of oxygen and carbonic
anhydride takes place at certain specialised re^jions (con-
tractile vacuoles), but the air is not brought into direct con-
tact with the circulating fluid. The oxygen or air for res-
piration is dissolved in water. The contractile vacuoles of
these organisms perform several functions, among thes^e
being that of respiration. The contractile vacuoles contain

J
I

PHYSIOLOGY OF THE INVERTEBRATA. 209

liquids, and daring contraction send out radiating canals.
This system probably communicates with the exterior. By
this primitive respiratory organ the working tissues are
brought into contact with oxygen dissolved in water*

The Porifera.

In the Porifera (SpoTigida) respiration is effected by means
of the oxygen dissolved in the water, which permeates
through the various canals, and thereby brings it into
intimate relation with the whole mass. In the circulation of
this water through the ordinary fresh-water sponge (SpongUla)
there is a fusion of the functions of digestion, circulation,
and respiration. ''Sponges absorb oxygen and give off
carbonic anhydride with great rapidity ; and the manner in
which they render the water in which they live impure, and
injurious to other organisms, suggests the elimination of
nitrogenous waste matter." It is possible that the oxygen is
retained in the substance of a sponge by certain respiratory
3>igments — probably a histoha^matin. Sponges are rich in
^chlorophyll, bat this pigment has another function — viz., the
iformation of fatty matter.*

The Ccelenterata.

In the lower CodetUercUa the function of respiration is
Performed by the general surface of the body. The fluids in
^b>Qse animals are in close relationship to the water in which
^^^y live ; and consequently the ectodermic lining serves as an
^**8fan of respiration. In other words the lower Coelenterates
^^^pire by the skin. In some of the higher orders of this
K^Oup the respiratory function is performed in the water-
^^^Jscular tubes along with other functions performed by the
^^xjae vessels.

Sut there is no doubt that the chief mode of respiration in

* Maclfunn in Journal of Phy Biology ^ vol. 9.

210 PHYSIOLOGY OF THE INVERTEBRATA.

the Ccelenterates is by means of the ectodermic lining, fo;
this lining is very largely impregnated with reapirator^^'S
and other pigments, as shown by Prof. Moseley " and Dr" "-
MacMunn.t

The respiratory pigments are capable of existing in a 8tat» -e
of oxidation and reduction, and no doubt play an importoD ^t
part in the function of respiration.

Professor Moseley discovered a pigment called pol^ ^■^--
perythrin in various C eel eute rates, and Dr. MacMann Lh^^bs
carefully examined the brown colouring matter of jelly-fiflLes -^ss,
and various pigments in the Adinicr:

In C'kri/saorn lii/soa'Ua a brown pigment is present ^r in
" the radiating triangular areas on the upper surface of tl^KHie
umbrella, and in dark patches, thirty-two in number, ^^all
round the margin of the disc, also in the tentacles ; but ■ in
each of these situations it possesses the same properties. I'

also occurs dotted on the surface of the umbrella betWL^ "''n
the triangular pigmented areas. Mici-oscopically, it occaw:^^*"
in grannies, and is limited to the surface ; these granules b-^^""?
yellowish in colour under a high power." Dr. MacMoc^f" ""
could not extract the brown pigment with alcohol, eth^^ *''■
chloroform, alcohol and sulphuric acid, and alcohol 0^^^-'"'
]Kitassium hydroxide. But he obtained an extract by allo^""""''
ing portions of Cli ri/snora to stand, " the sea-water contain-- ™
in the tissues dissolved the pigment, forming an oran^eH?"
brown solution, showing a broad dark band at the blue e^^^"*
of the green. When more pigment went into solntion, t"^®
fluid became a dark brown colour. Boiled in fresh and p^^^*'
water the colour went into solution, but showed no banc- ***
except the shading at the blue end of the green, A der--^^T
layer of this solution only transmitted red and some gre^^^*^*
Ammonia and caustic potash precipitated the colouri:

• Qimrlfrly Journal of Microtaipleal Hocielij, vol. 17 ; and JoHntal
Phijilo'ogy, vols. 7 and 8.

t Quarleny Journal of Microteoptad StUnce, vol. 30 ; and Journat
Marint Biological Aaoeiation, 1889.

PHYSIOLOGY OF THE INVERTEBRATA. 211

matter. Hydrochloric acid did not discharge the colour at
first, although it became much lighter ; strong sulphuric acid
and nitric acid discharged it after some time. Absolute
alcohol also precipitated the pigment, the fluid becoming
floccnlent after a while. The colouring matter in the fresh
state showed no bands except some shading at the blue
end of the green; it also absorbed the violet end of the
spectrom."

Dr. MacMunn's investigations on the respiratory pigment
of Chrysaora confirms those of Dr. J. G. M*Kendrick, F.R.S.,*
who has also investigated the pigments from Cyanca and
Aurelia by allowing fragments of these organisms to
macerate in sea-water for about thirty-six hours. " In these
cases ammonia precipitated the colouring matter from its
solutions, and it dissolved in acids." Dr. M'Kendrick states
that after death '^ the body becomes slightly acid, the
protoplasm disintegrates, and the colouring matter diffuses
out."

When examined by the microspectroscope the fresh pig-
ment from Cyanea, as well as an infusion of the organism,
gave two bands, one in the orange and the other in the
iied.

The spectrum of the blue pigment of Rhizostoina Cuvieri

Consists of three bands, one in the red, a dark one

^t D, and an extremely faint band in the green. There

i^ little doubt that the same colouring matter occurs in

-fihizostoma as in Cyanca. This pigment has been termed

Oyanein by the late Dr. Krukenberg,t and he compared

ifi w^ith the blue pigment found in Velella limhosa by A. and

Co}. De Negri.$ Cyanein is soluble in water, insoluble in

benzene, ether, carbon disulphide, and chloroform. On the

^.ddition of alkalies, cyanein is changed into an amethyst

c^olour, while acids colour it red.

* JourndL of Anatomy and Physiology^ vol. 15, p. 261.

t VergL Physiol. StvdUn^ zweite Reihe, dritte Abtb., 1S82, s. 6S.

X Oazetta Chimica Itaiiana^ vol. 7 [1877].

Jia PHYSTOLOGY OF THE IIWERTEBRATA.

lu 1 884, Krukenberg stated that cyanein occurs in ('>W/'« '
Aurdia, Ci/etin'a, and Bhitosti/ma.

Dr. MacMunn' has examined the pigments (rom th '
following Ac/'iiiuv : — Acjinia intstmljrijauthainiin,, Jinrunffrrsi
craasicomis, B. balUi, Sagartia bel/w, S. dianl/nis, S. jiara^
silica, S. nduttla, S. troglodytes, and AiUhea cfri-.m

(a) When the solid irortiona from the ectoderm, endodenia
and tentacles of the red-coloured specimens oiAclhtia i/kwot ^^"
hriiaiitliemuvi were examined by tlie microspectroscope, the^-^^y
gave a band which closely resembled that of reduced hBemo^cia>-
globin, accoDipanied by two other bands nearer the viole^^»^
end of the spectrum. The extreme edges of the shading crz^ of
the band extend from X 600 to X Si5o, while its darkest par^-^^
is from X 5S0 to X 563. " These measurement-s \'ary accor^E»^'
ing to the colour of the specimen, for in brown specimen^nK 'ns
the dominant band is nearer the violet, and in some a bani .«i^cno
is also present before D." The latter spectrnm is said tz*" to
beiong to modilications of the same pigment, as the saxtm-^-^^
■ decomposition products are obtained in both cases. TLtM^*^'^
spectrum of the brown specimens of this species has a clo^s-*:^^'*'
resemblance to the histohajmatins. MacMunn hag name^^^ ■"'
this pigment actinioliairaatin.

Actiniohiematin is soluble in glycerol, bat it is insolable S '"
alcohol, ether, chloroform, carbon disulphide, benzene, &^ ri^c.
This pigment is also extracted (but in a changed condition:^'^ ")
by treating with alcohol and potassium hydroxide (either hc:^ "^
or cold). By the latter treatment a reddish solution fc "^
alvai/s obtained, which gives a band at D. generally extendin ^*S
from X 625 to X 5S9, recalling to mind the spectrum ■
alkaline hEematin. When ammonium sulphide was added t
the alkaline alcoholic extract, the band at U was replaced I
two bands which are undistinguishable from the spectrum t
hsemochroniogen. MacMunn has also observed that all tha
7'cv/ pigments in the Artinm gave after this treatment in tip

• PhilotnjAital Traaaaclioru of Royal Societg, 1885 (part it), p. 641 ; oC
QuarUrly Jotirnal 0/ Microicojiical &!eiice, vol. 30.

PHYSIOLOGY OF THE INVERTEBRATA. 213

solid state (i.e., examined in the compressorinm) the spectrum
of hflemochromogen. It may be remarked that Professor P.
Hoppe-Seyler* fonnd that when solutions of haemoglobin
are treated with potassium or sodium hydroxide in the
absence of air, the haBmoglobin is converted into haBmochro-
mogen. In the solid tissues of the Actinia^ says MacMunn,
a similar reaction occurs, but in the solution used to extract
the pigment the hsBmatin becomes oxidised as it comes out
of the tissue, and shows the alkaline ha^matin spectrum,
which, however, can be reconverted into haemochromogen by
the addition of ammonium sulphide.

MacMunn could not obtain acid haematin, but he did

succeed in converting the pigment into hsematoporphyrin.

"By digesting portions of an Actinia in sulphuric acid, and

filtering through asbestos, a purple-red solution was obtained,

which showed bands like those of acid haematoporphyrin, a

iittle rectified spirit being added to the acid solution; but

the band nearer the violet is not placed exactly in the same

position as the corresponding band of hsematoporphyrin

obtained from haemoglobin. The first band extended from

I 605 to X 595, and the second from X 563 to X 55 1, but owing

o the presence of biliverdin and proteids these measure-

cients may not be quite reliable ; still, they possess a certain

^ae when the results are compared with other cases. If

his spectrum be that of a kind of haematoporphyrin, it ought

o be changeable into alkaline haematoporphyrin, and such

s the case." From the above remarks there can be no doubt

hat in Actinia mescrtibryaTtthemmii a pigment is present

irhich can be changed into haemochromogen and haemato-

K>rpbyrin.

MacMunn has also extracted (by means of alcohol and
alcohol and sulphuric acid) the green pigment situated
>«iieath the ectoderm of many specimens of this species
>i Actinia, This pigment gives the reactions of biliverdin
[^Ci^H^NjOj ?). "Hence A, Tnescmhryanthemum contains in

* ZeiUckrtfi far PhysiologUche Chemie, vol. i, p. 138.

2T4 PHYSIOLOGY OF THE INVERTEBRATA.

its ineBodenn and eisewliere a colouring matter undistiDgciieli-"
able from bilivei-din " of the Virtclirnto. As biliverdiu i^
derived from the decomposition of ^'erteb^ate hiemoglobin- -
ita presence in Aithiin is fnrtber proof that these organisUL.^^
contain pigments closely allied to hesmoglobin.

MacMunn has proved that the h sEniati n -yield in jr pigmeu J-

of A.'"ics(7nhri/aiitJu:tiium is not the same as Prof. Moseley 8
actiniochrome, although the latter pigment is present i^rrJ
certain species of the Adiiiic: The band of actiniochrome i^Kris
nearer the red than that of MacJIuiin's pigment (actinionrra^
hii'matin), and the two pigments yield entirely differenB=»t
decomi>ositiou products under similar treatment. After *

careful examination of the glycerol extracts, MacMuna foan _^Knd
that " every specimen of Actinia inesemirryanlknanm, wheth^^ f
its colour was red, reddish-brown, brown, or green ish-bro» l-^w^'^
gave to the glycerol, after some days' extraction, a certai j««"
amount of colouring matter, which in every case could b^zi:^^
made to change into hiemocbromogen, while actiniochron^^*'^
never could be changed into it ; hence the respective pi^^?'
ments are very different. One is a ratpimlori/ coloitrin// mntti-
(actiniobsematin), the other (actiniochrome) is an omamenlM
one."

The glycerol extract made from the ectoderm of an anemoa^^^
yielded actinioha?matin, which, on tlie addition of potassinic""^*
or sodium bydroside and ammonium sulphide, was rapid!**'
changed into hipuiochromogeu. "It appears that tht^^*
ha^matin-yielding pigment does not give the same 8]>ectruiT-^«^"
in brown specimens as in red ; but the spectrum of th^^^
glycerol extract of red Actinia has a close resemblance tc^ "
that of the spectrum of the solid ectoderm and other part^
of brown specimens. This does not show that the pigmenf
has been altered by extraction with glycerol, but its mole—-
cnlar condition may be altered. It is well known that th*?"
spectrum of a pigment may differ in the solid and liqnid
state without any necessary change in its composition (Voge-I
and Kundt)."

. I

PHYSIOLOGY OF THE INVEKTEBRATA, 215

(b) Bunodes crassicamis. — ^Moseley * examined this Actinia,
md he found in two specimens the tentacula were a rose
x>loury the coloar being due to actiniochrome. MacMunn
bas more recently examined the pigments of this species of
Bunodes ; and he found that the colour and spectra differ
considerably in different cases. The conclusions arrived at
we that "in Bunodes crassicamis we find actiniohaBmatin
pnth tolerable constancy, occasionally actiniochrome and also
biliverdin, besides the lutein-like (lipochromes) pigments,
[n the ectoderm, as well as in the endoderm, and sometimes
b the tentacles, actiniohaematin is present. In none of the
specimens were * yellow cells' present, and by no other solvents
3xcept glycerol, and alkaline and acid alcoholic solutions,
x>uld any pigments be got into solution."

(c) Burwdea bcUlii, — The tentacles and mesenteries of his
nemone, when examined by the microspectroscopei gave a
amber of bands, which showed the presence of a chlorophyll^
ke pigment. In the large variety of this species the tentacles
re i>acked with " yellow cells " f lodged in part in their
adodermal lining. It appears that these '^ yellow cells "
3place the red pigment of other species, since the latter
\ present in mere traces. No " yellow cells " are present
\ the tentacles or elsewhere in the small variety of Bunodes
xllii. The inner tentacles of this variety gave the spectrum
f actiniochrome; but no hsemochromogen was produced
rom these anemones. Still, the fact is interesting, that the
^igrment of the ectoderm resembles, with regard to the first
land of its spectrum, that of A. m^semhi'yant1iemum\ and
liacMunn remarks that ^'it may have been a pigment which
s intermediate between actiniochrome and actiniohsematin.
Che replacement of this pigment by the colouring matter of
he * yellow cells ' in the large variety is of great interest,
ftiid teaches that the presence of the colouring matter has

• Quart, Journ. Micro, Soc., vol 12, p. 143.
t Symbiotic algse.

;r6

PHYSIOLOGY OF THE INVERTEBRATA,

aomething to do with the absence of 'yellow cells' in tie
small variety."

(rf) Hnym-tia difitUhvs.— T'he brown and white epecimeo*
both contain a htematin-yielding pigmpnt, which is \fO'
doubtedly actiuiohEematin.

{e) Sttgnrti/i ntlnntti. — On extracting the (Hrtoderm f*^^
twenty-four hours in alcohol and catisttc potash a yeUw""*
solution was obtained. This gave a chlorophyll-like spectmi^*^^'
but faint traces of lisEmochromogen were detected on tt^^^
addition of ammonium sulphide.

(/) Sngnrtin parasUica. — In this species MacMunn di^ -*^
covered the presence of actiniohEpmatin and anotlier pigmen-^^^ '
which is different from any other he had previously examinec^"^^'
This latter pigment is pecnliar to this species. "In it*'-*
colour-changes with acids it has a veiy remote resemblance:^ '*
to the purple pentacrinin of Professor Moseley, also to th^ciJ"'
colouring matter of Apli/aii, but differs in spectrum an-- ^^°
in some colonr-changes." ''Yellow cells" are absent it -*"
.S'. piimsiiica ; its colouring matter ia capable of anitis^^ S
with oxygen and of giving it up again ; cxmsequentlj it ha — — '
a respiratory function.

((/) Sngartin trofflodi/te". — The solid ectoderm of thi^^^B
species yielded a pigment which isi-elated toh^mochromogen— ^^|
MacMunn believes that this pigment is a histohfematin. ^H

(A) Sngartia Mlis. — The tentacles of this species were^
found packed with " yellow cells." The spectroscopic exami— •
nation of the tentacles showed a banded spectrum reminding'
one of chlorophyll, or rather chlorofucin. This spectrum
belongs to the mass of "yellow cells" which are embedded
in the endodemial linings of the tentacles. The ectoderm
and cndoderm do not contain ha?niatin.

The examination of solutioiix of the tentacles revealed the
presence of a small amount of other pigments; but it appeara
that the presence of the " yellow cells " has something to do .
with the absence or suppression of respiratory pigment*.

(i) ArUhea cems. — " In some specimens the ectoderm was

PHYSIOLOGY OF THE INVERTEBRATA. 217

a pale red, also the base, and the tentacles a pale green
tipped with violet. In the violet apices of the tentficles,
actiniochrome was detected. The rest of the tentacles gave
a spectnun resembling that of chlorophyll." The base in
some specimens of this species contained actiniohaematin.
Besides the above-mentioned pigments, there are " yellow
cells" present in the body cavity and ectoderm. The
" yellow cells " on treatment with Schulze's solution gave the
reaction for cellulose. These cells contain starch.

AiUhea certas contains symbiotic unicellular algae, and
MacJVf onn has proved that the chlorofucin in AiUhea cereics,
Bunodes ballii, and Sagnrita bdlis, is without doubt due to
the so-called " yellow cells " ; and in those anemones possess-
ing " yellow cells " there is more or less suppression of the
respiratory pigments found in other Actinia:, The extracts
of the " yellow cells," prepared by Sir G. Stokes's fractional
methody yielded chlorophyll and chlorofucin, proving that
the colouring matters of the algae are several, for there are
present at least one chlorophyll, one chlorofucin, and certain
lipochromes, and perhaps other pigments, all of which belong
o the " yellow cells."

These ** yellow cells " are parasitic algae and have not a
lepatic function as supposed by the late Dr. Krukenberg.
n no Invertebrate *' liver" are such bodies found.

The Invertebrate /urr-pigment, or enterochlorophyll, occurs
oostly dissolved in oil, or in granules, or diffused through
Izie protoplasm of the lining cells of the "liver" tubes.*
"*lie colouring matters of these " yellow cells " belong to the
lulorophyll group, and bear no relationship whatever to
'Xiterochlorophyll, which is in direct opposition to Kruken-
►^rg, who stated that the pigment of the " yellow cells " is a
i.«patochromate, which is his name for enterochlorophyll.

The ^function of animal chlorophyll is of use in the
^^spiratory processes of animals,!

* UacMann in Proc Roy. JSoc. 1885; and Pit'dos, Trann. i885, part i.
i" RegDard in CompUs Jtendus^ vol. loi, p. 1293.

PHYSIOLOGY OF THE INVERTEBRATA.

(J) Ciyniyiinrth t

■jVjs.

— MacMiinn haa examined the red

Bpecimens of this little sea anemone. On putting one oi
these animals into a compressoriuni and exnmining it b^
means of an achromatic condenser and a niicroFpectroBCOp*^'
a spectrum was obtained whose liands do not correspoii-*
with either those of actiniohrcmatin or actiniochrorae, ft>^
they are nearer the violet and differ in other respects. Y^
they belong to a pigment which is related to actiniohEeni8tL:*i'
for this pigment can readily be changed into bsem^cD-
chromogen, No " yellow cells " are present in either the t^C^
or preen varieties of C I'mifc. TluTe is no doubt that tl^^»i-'>
anenioni.' contains a respiratory pigment allied to octin^^w"-
hEematin.

The important researches of MacMunn and others ha — ^^
shown : (i) That a rcK]iiridiny pigment is largely present •"

many Actinia:. That it must be respiratory is shown by f'J'^
fact that one of its decomposition products is capable "'
existing in a state of oxidation and reduction. That it ^
closely related to Iia?mogtobin is proved by the fact that it "
capable of being converted into ha;mocbromogen (reduce^^
ha'Uiatin) and ba'matoporphyrin,* which are uudistingnist-*"
able from the same products obtained from hiemoglobi*"*-
(2) The respiratory pigment in the Adinicr cannot be looke!"*^^
upon aa a earner of oxygen, but as a means to knr it in cons '^
bination until it is wanted by the cells for metabolic pnr"^
poses. "As it is distributed all over the surface of Bom*=^
Actinia', the whole body of such an animal may, in a physic-*''
logical as well as in a morphological sense, be OOnaider^A
comparable to a single organ of a higher animal, so far, sC^
least, as intirmtl] respiration is concerned."

(3) In evei-y species of Arlinia; even in those Blmost^-
destitute of colour, the presence of respiratory pigments ha^
been detected. Tlie coloured proteids, which are concemetJ
in tisaue-respi ration, enable the anemone to abstract oxyger*

* Idoiwlry'a poljperytbrin is Uentical with MaoUn mi's haBmatoporphjPibl-
t Thai is, tisiue- respiration.

PHYSIOLOGY OF THE INVERTEBRATA. 219

the sea-water in which it lives, and to hold the oxygen
; tissues. (4) In animal tissues chlorophyll or allied
ants may be of use in furnishing oxygen to the animal ;
n those Actinicc with " yellow cells " the chlorophyll
9nt appears to replace (more or less) the respiratory
id. (5) Throughout the whole animal kingdom, in each
) and organ there are present pigments which are con-
d in the respiration of those tissues and organs ; they
the oxygen from the circulating blood, and fix it until
wanted for metabolic purposes in the cells. MacMunn*
all these coloured proteids histohsematins, and the one
I in muscle he named myohsematin. (6) Besides the
ratory pigments found in the Actinicc^ there are others
1 appear to be of use for decorative purposes, and to this
Moeeley's actiniochrome belongs. Actiniochrome cannot
langed into anything capable of being oxidised and
ied ; in other words, it is not a respiratory pigment.
; its use may be it is difficult to say. It may be intended
protective purpose or as a means of attracting prey.

The Echinodermata.

e cloacal tubes of the higher Holothuridea are most likely
"espiratory function. These tubes, which ramify in the
isceral cavity, open by two orifices into the cloaca. This
i receives the water, and projects it vigorously outwards,
1 average three times a minute. Analogous systems
in many other Echinoderms, and often they are bedecked

cilia.t

e ambulacral vesicles of other Echinoderms constitute
lal respiratory organs. Besides these organs, tissue-
ration (by the aid of pigments) is well developed in the
loderms,

■

Researches on Myohscmatin and the Histohsematins," in PhUotophical
lettons of Boyal Society ^ 1886, pt, i. p. 267.
Dgis in his Physiohgie Compart, t. 2, p. 355.

aao PHYSTOLOGY OF THE INVERTE^RATA.

MacMuim* has digcovered rarious pigment's in the tissue*
and organs of thp Echinoderms ; and in most of them th^
appearances differ in no respect from thoso seen in Vraii^'*

ruhens.

A portion of tlie tissue or organ is examined in a corapre^*" I
sorium, by means o£ which any required thickness can fc^*!
examined : it is illuminated by a strong light condensed upc^"!! 1
it by means of a substage achromatic condenser, and
examined by a microapectroscope (see Fig. 32J, or by laetiM:^^
of a chemical spectroscope.

The generative organs (^ and 9) and ova of JTra^^
contain a typical histohtematin. The spectrum of thia pi^
ment gave the following n

X 613 10X591. or 593.

X 569 „ X ^60.

^ 556 „ X 548-5-

^ SJ7 .1 X 5'^ (about).

A spectroscopic examination of the stomach-wall and tfci ^
ampullaa of Unuykr showed the presence of hremochromoge*^^^^^

"In the integument of Urader nibens, when it has
brownish tint, the presence of hsematoporphyrin t can b
easily proved, and as the only pigments present in the animd
are enterochlorophyll in the radial catca, histoba^matius in th^
tissues, and a lipochrome here and there, and as htemat«
porphyrin cannot be obtained from enterochlorophyll or trott
the lipochromes, it is highly probable it is a metabolite of th*
hiatoh as matins, or, what is less likely, that these pigments ma^^
be derived from the same radicle."

il. Fcettinger states that he found hiemoglobin in Ophiaeti^^
tnrtJtji and MacMunn's researches tend to support Fcettinger*^^
idea of the passage from a histohtematin to a hsemoglobin. J

• Philotoph. JVan*., 1886, pt. i. p. 369 ; Qaarterli/ Juum. Jlierot. A^unc^i '
vol. 30, p. 51 ; Journal of I'hyiiiAogy. vol. 7, p. 24X.
t This pigment can be isolated b; digegtln;; the lategameat in lienhol

PHYSIOLOGY OF THE IN VERTEBRA TA.

221

The integament of Asterias glacicdis does not contain
li89matoi)orphyrm, but there is present at least one rhodo-
phan-like lipochrome. The radial cceca (so-called liver) con-
tain enterochlorophyll and a lipochrome.

MacMonn has also examined many other species of
Echinoderms, and the following table gives a partial summary
of the pigments present in various tissues and organs of
these animals : —

Integument.

Orariei.

Digestivd gUnd.

Badi U ceca.

JBolotkuria nigra

—

lipochromes

;

GenuM hrunneus

lipochromes

entero- '
chloro-

-^tUrias glaeialU -^

lipochromes , —

phyU and

lipo-

chromes.

'^Uterina gUboia

lipochromes lipochromes

^hmioHer equestrii .

1 ^

—

<«

■Qblotter pappoBa

«*

'^~ ♦»

^^^ribeUa oadata

lipochromes

—

MacMunn says that the respirator^/ proteids ** are as im-
f:>rtant as haamoglobin, if not more so in some animals, and
bey have the right of priority in time, as they were developed
1; an earlier period than hssmoglobin, speaking from a phylo-
'enetic i)oint of view." Even in the lowest of the Metazoa —
he Sponges — ^MacMunn * has met with histohaamatins where
hey are also capable of oxidation and reduction, and are
herefore respiratory. ** It is not improbable, but indeed
Ikely, that by a process of physiological selection these
espiratory proteids may have become more complex, and
Iieir molecular instability therefore greater, as the animal
>ody became more elaborated, and a necessity arose for the

Proceedings of Physiological Society, i886.

212 PHYSIOLOGY OF THE INVERTEBRATA.

setting apart of respiratory proteids for abstraction of oxygen
from the air. In this way htEmoglobia may have arisra, and
although it is usually said that the mere colour of hiemoglobia
is of no use, yet the fact cannot be denied that 77i(»rf rexpxmtorii
pToteuh an' coloured IjoiHcx. The molecular complexity of the
bistohfematins is certainly not so great aa that of lieemoglobin.
and their respiratory capacity is apparently far inferior to
that of htemoglobin, for the hiatohiematins do not take up the
oxygen in a loose combination, although they certainly do
unite with it in a more stable combination. At the same
time, one must remember that the myohiematin
bistobijomatin procurable from dead tissues differs in fipectrum,
and therefore probably iu chemical composition, from that of
the living tissues. It is well known that no free oxygen cm
be obtained fi-om muscle, and if myohiematin be the body
with which it unites, then myohfematin must certainly 1«'*
something to do with the storing of oxygen in muscle ; and
if this be the case in mnscle, it must be the case in oUi^r
tissues, and in the organs in which the histohce matins o^
found."

In studying the chromatology of many Invertebrates.
il^Munn "has been struck by the fact that while some "
their colouring matters can be reduced by such reduci**^
iigents as ammonium sulphide, yet by shaking with air. *^^
by passing a stream of oxygen into them, they cannot be *"*^
oxidized ; iu this point tliey aflfurd a jMirallel to the his*'*'"
hiematins. Krukenberg has noticed the same thing, and »

has justly concluded tliat the respiratory processes of mau^'
these animals is not as simple a matter as it is supposed
be. There can be no doubt that the union of these resp» *^*'
tory coionring matters with oxygen is a ranch more st^ *-^
one than is the case with basmoglobin. It is in the obaar*^^
tion of such facts as these that the spectroscope comes to
of value, for if these bodies did not show absorption baw^^:
one could not determine whether they were in the oxidi
or reduced state."

PHYSIOLOGY OF THE JNVERTEBRATA, 223

The Trichoscolices.

The water-vascalar systems, which are often ciliated, con
stitute internal respiratory organs. The water which per-
meates these tnbnles contains oxygen. Respiration in many
of the organisms belonging to this class is also performed by
the external sarface of the body ; and no doabt internal or
tisane respiration takes place by means of various respiratory
pigments.

The Annelida.

In the Annelida the principal seat of respiration is the
psendo-hadmal system. For instance, in both the Hirivdinea
and OligocJueta this system of vessels is well developed, and
has been alluded to in a previous chapter.

The blood which these vessels contain consists of a coloured
plasma, and it is stated to possess no nutritive properties.
The pigment present in this fluid is haemoglobin.*

In reality the fluid contained in these vessels has a respira-
tory function and contains air in solution. The pseudo-
•i^aemal systems are in communication with the external
^i^edium. This communication of the respiratory system
Vrith the air or water in which the animal lives probably
swerves the purpose of the gaseous interchanges which are so
^^ssential in animal life. There must be a constant accumu-
lation of carbonic anhydride in the respiratory fluid, and
therefore a constant diminution of the quantity of oxygen.
"!lhe oxygen must be restored, the carbonic anhydride excreted.
I^oth these important ends are attained by means of this
^ver-recurring communication between the water-vascular
^^stem and its homologues on the one hand, and the animal's
^nviix)nment on the other. Hence in the lowest as well as in
the highest forms of the animal kingdom, cutaneous respira-
tion is an important adjunct to the various organs or devices

* HacMann has proved that the integament of Luinbriais terrestrU con-
'^jdns bsBmatopoiphyrin {J<mrn. of Physiol, vol. 7, p. 248).

r-
hioh ■
sbuI

214 PHYSIOLOGY OP THE INVERTEBRATA.

which are usually called respiratory ; and certainly this forni
of respiration is wel! developed in llinulo.

In the Ptili/ckala there are simple or branched cirri or
branchiie which have ciliated walls and contain blood-ves«el&
These branchiit, situated on the dorsal walU, are usuallj^fl
appendages of the parapodia, and have a respirator^' fnncti(».""
In the lower Invertebrates the brauchiie are mostly situated
externally (('..7., ATeiiicola), 30 as to tloat freely in the sop-
rounding water; whilst in the more highly organised, as the
Molluscs, these organs are enclosed in a cavity into whitji J
the water has free access, and may easily be renewed.

In the Gephi/rc'i there appears to be several devices e
aiding in the function of respiration.

(rt) A respiratory function is attributed to the tentacnl
in these marine vermiform animals.

{h) In Fnnjnilus and SliT»a.ipis there are certain fila-
mentous appendages given off at the posterior end of the
body. These are said to be branchiat.

(d) " In &/iiurus, Bonclliay Thalasseina, a pair of tabular,
sometimes branched organs, which are ciliated internally,
and communicate by ciliated apertures with the peri-
visceral cavity, open into the rectum. These appear Co
represent the water-vessels of the lioti/era and the respiratory
tubes of the Hoiothui-i(v."

Although the above devices represent the actual organs
of respiration in the Anncliila, supplementary respiration,
by means of pigments, also occura in this class of animals.

In Phi/UoihHX viriilix there occars a green pigment which
is not chlorophyll.' This pigmL-nt is soluble in alcohol and
benzene. MacMunn examined a living specimen of this
Polychiete AhikHiI in the compressorium, nnder the micn>-
spectroscope, but he could not detect any bands ; in fact, h^^

* Prof. P. Geddeg in Proc. Hoy. Hoc. Edin., xol. n. |
MacMunn in Quart, Journ. Micros, fi'c'carr, vol. 30, p. 70.

. 379; and I>2S

PHYSIOLOGY OF THE INVERTEBRATA. 225

says : '^ No cUoTOcrnorin, no hssmoglobin, no chlorophyll was
present, and no discernible lipochrome. The solid pigment
became reddish-brown with sulphuric acid, and red-brown
with nitric acid." MacMunn simply names this colouring
matter phyllodoce-green, as it is impossible to refer it to any
class of animal pigments.

In PoTUobdella, a pigment, bearing a remote resemblance
to chlorophyll, has been extracted from the integument
where it occurs in large pigmented cells of a green colour.
This worm, belonging to the Hii^udinea, although it lives
on fish-blood, is capable of manufacturing from its food a
oolooring-matter allied to chlorophyll. This pigment is
soluble in alcohol and ether.

Mr. F. E. Beddard, F.R.S.E.,* has examined the glandular

cells in the integument of JEolosoina tenebraricm and other

species of this genus. In the species mentioned these cells

are nucleated, and in the centre is a large globule of oily

appearance impregnated with a green colouring-matter.

Yejdovskyt states that this globule is stained black with

osmic acid; but Beddard found that this acid stained the

globule a brown colour. Various reactions given in Bed-

dard's paper show that the green colouring-matter of this

worm is not chlorophyll. In its behaviour with acids and

alkalies it resembles certain pigments described by Prof.

Mo8eley4 I^r- MacMunn, and others ; and there is little

doubt that it has a respiratory function. This pigment is

different from bonellein and chlorocruorin, two pigments

present in certain Annelids. The blood of jEolosoma tcTie-

harum is colourless, and there are no special respiratory

pigments in other parts of the body ; therefore, as Beddard

justly remarks, 'Hhe pigment of the integumental glands

may perform the function of respiration."

* Proceedings of the Zoological Society ^ 1889, p. 51; and AnnaU and
MiMgazine of Natural ffintory, 1889, p. 262.
'^ ^ieriiche Organiimen der Brunnenwdsser von Prag^ p. 61 [1882].
i Quart, Jovm. Microe, Science, vol. 17.

226 PHYSIOLOGY OF THE INVERTEBRATA.

Other species of j^oloxowa contain various coloured oil-
globules, showing the pre-sence of different pigments in each
case. These pigments differ considerably in their capacity
for oxygenation and deoxygenation — hence the reason of
Beddard's remark: "That the orange-brown pigment of
^olonmna quaicrvarium and the bright green pigment of
^olosomn variegatum and Headlcyi may be less perfect as
respiratory pigments, and therefore in course of degenera-
tion."

Although chlorophyll is absent in Phi/lMore, PontobdrUa
and ^olosoma, certain Annelids contain this pigment.

Clta-ioptems is one of these animals containing chlorophyll^
as shown by Prof. Ray Lankester, whose investigations have
been subsequently confirmed by Dr. AlacMunn. The alco-
holic solution of this pigment possesses a red fluorescence,
and gives all the chlorophyll bands, and yields "modified"
and "acid" chlorophyll, as well as phyllocyanin, by snitabl
treatment. There is no doubt that C/M-foptrrm i'iiaV/rm
contains a true chlorophyll, although it may be remarked
that Prof. P. Geddea could not detect any evolution of
oxygen on exposing Cha-toptcnut Ynh-runeniif^ii to sunlight;
but this is not to be wondered at, since the chlorophyll u
shut up within the animal's body (MacMunn),

A large number of the Aniuiula cont^n hietnoglobin,
as shown by Lankester and others : among these may be
mentioned the following: Arcnie^a. Lumhrii-us, Tm^lia,
t'irraiuhts, Kcrcis, and Aphruditr. In the la^t-mentioned
genus the haemoglobin is limited to the ventral ganglia. In t
J'olyniic, the area round tlie cerebral ganglion is of a red M.
colonr. According to Macilunn this pigment showed a band^jG
which somewhat resembled that of reduced ha-utoglobin. .^
Many of the .*l/(/((7(V?(t are also rich in the pigments kuowiix—i
as lipochromes.

There is no doubt that in this class of animals respiratJc^^^a
is greatly aided by various respiratory pigments.

>l>7l«

have

alco-

Mce,

led-J

taUsfl

iV/RM I

PHYSIOLOGY OF THE INVERTEBRATA. 227

The Nematoscolices.

Very little is known concerning respiration in the Ncma-
touleaj but the investigations of Dr. G. Bunge* have thrown
a certain amount of light upon the subject. He has shown
that Ascaris mystax (infesting the intestine of the cat) and
Ascaris actis (from the intestine of the pike) will live four or
five days in media quite free from oxygen. In the ultimate
respiratory processes of these animals there must be a forma-
tion of energetic reducing substances (nascent hydrogen and
easily oxidisable organic matter), which unite with one atom
of the oxygen-molecule, even to a greater extent than
in animals which breathe oxygen. These animals possess
no respiratory apparatus, but, a priori^ there may be present
in their bodies one or more of the respiratory pigments which
retain oxygen within the system ; and this retention of
oxygen may be for a considerable time.

In order to investigate this important question more fully,
Bunge employed larger species of Ascaris, The parasite of
the horse, Ascaris megaloccphala, was found unsuitable, as it
only lived for two days after removal from the intestine ; but
Ascaris lujiibricoules of the pig lived from five to seven days,
and it was therefore used in the investigations. In boiled
salt solution it gave off abundance of gas, which was collected
over mercury. This gas was completely absorbed by potash,
and consisted of pure tarbonic anhydride. The quantity of
gas obtained in this time was from 5 to 10 cc. per gramme
of the animal's body-weight. In three experiments a small
measured quantity of oxygen was added to this gas artificially,
but there was no diminution in its volume after the ad-
mixture ; thus not only hydrogen, but other reducing sub-
stances are absent.

♦ ZeiUchrift fUr Phyiiologische Chemie, vol. 8, p. 48 ; and vol. 14, p. 318.

2is physiology of the invertebrata.

The Myrupoiu.

The respiratory organs of these Arthroijods are trachta'-
The trachea? form a branched series of tubes spreadin^r
thronghoat the body and conveying oxygen to the variouft
organs-, tissues, and blood-vessels. The tracheat communicate
with the exterior by openings called Etigmata, which are
situated on " the lateral or ventral surface of more or fewei"
of the somites. In Smliff^a " the stigmata are situated in th^
median dorsal line of the body."

In this class of animals the function of respiration is of m^
much higher order than in any other air-breathing animal
alluded to in the present chapter. We find in the Mifriajif/dt^
a special set of tubes set apart for respiration and by niean^
of these tubes the air is brought into contact with the blood- — -
vessels distributed over the walls of the tubes. Although^
these animals breathe principally by means of a tracheal or:*^
air-tubes, they also breathe in lesser degree by their general-
surface ; but this kind of respiration is more marked in thos^?^
animals whose integument is unprotected by epiderma-3-
developments.

The introduction and expulsion of the air in the tracliea*?-
appear to be helped by regular movements of the abdomin&l
walls.

The Insect*.

In the Insecta the systems of tracheie or air-tubes are
further developed. The ultimate ramifications of these tubes
constitute a fine network, analogous in many respects to the
capillary networks.

As in the Myriapoila these trachea3 communicate externally
by means of stigmata. These stigmata are restricted to the
Bomites of the abdominal region of the body ; and very
frequently these openings are occupied by perforated plates.
The perforated plates act as sieves or filters, and thus free
the air, as it passes through them, of mechanical impurities.

• Siec nlso Sinclair in Proc. }toy. Soc., 1871 ; anil Kature. Dec. 17, 1851,
p. ifi^i.

PHYSIOLOGY OF THE INVERTEBRATA. ii<)

As a general rale, each stigma does not open directly into a
tracheal tube, bnt into an ante-chamber whence the trachea
takes its origin. This ante-chamber is frequently provided
with a series of little plaits, folds of its lining membrane.
These plaits or epiglottides also act as filters.

The principal trunks of the tracheal system have three
coats. The internal one (in contact with the air) is a con-
tinuation of the integument. The middle one is a spiral coat
of chitin, which serves to keep the tube open. The external
coat is of connective tissue.

As in the Myriapoda the air in the tracheaa is kept in
motion by the movements of the abdominal walls. These
rhythmical movements are frequent ; on an average twenty-
five in Zucanus cerviis (the stag-beetle), eighty in Apis* and
from fifty to fifty-five in the Locusta viridissima of Linnaaus.
Notwithstanding the high development of their respiratory
apparatus and the activity of their lives, insects resist
asphyxia for a long time. The author kept a stag-beetle for
six days in an atmosphere containing 60 per cent, of chlorine,
with the result that it was still living after the expiration of
that time ; and many insects resist the action of an atmosphere
containing from 40 to 70 per cent, of carbonic anhydride.
This may account for the fact that insects and other cold-
blooded animals were able to withstand an atmosphere so
laden with carbonic anhydride as was that of the early ages
of the world's history. And if the descendants of the primi-
tive insects are now cfkpable of living in an atmosphere con-
taining only SIX volumes of carbonic anhydride in io,CXX)
volumes of air ; it is but one of many instances where natural
selection (the survival of the fittest) and the direct action of
the environment have worked hand in hani} together.

Concerning the vitality of insects, it may be remarked
'that M. Lyonnet states that certain caterpillars revived after
^ing submerged in water for eighteen days.

* In ApU (the bee), Newport observed forty in a state of rest, bnt they
to one hundred and twenty with muscular exertion.

330 PHYSIOLOGY OF THE JNVERTEBRATA.

Kespiration in the aqnatic larvse of certain insects U
perforaied by means of tracheal gills or branchia?. These
branchice are delicate folds of the integument, and are richlj
supplied with minute trachete. The oxygen dissolved m
water, wherein or whereon these larva; flit to and fro, passes
into the tracheie. This phase of respiration among the
Iitsixbi is suggestive of the brtiDchise of certain forms of the
Aimd'uhi, into which the vessels of the pseiido-hfcmat systenis
enter.

The larvffi of Lih-lhihi and j-B.ie/tna present yet another
form o£ respiratorj' organ. "Although they possess a pair
of thoracic stigmata, these appear to have little or nn
functional importance, but respiration is effected by pumping
water into and out of the rectum. The walls of the latter
are produced into six double series of lamellfie, in the intenor
of which trachea) are abundHntly distributed, and which play
the same part as the tracheal branchiae jnst mentioned.
These rectal respiratorj- organs, in fact, appear to be a com-
plicated form of the so-called ' rectal glands' which are so
generally met with in insects."

Besides the systems of tracheal tabes, tiasue-respiration is ^ii
well marked in the InseHa, for MacMunn has met wifL x^-jf
myohiematin in abundance in these animals; and it is ^_g^
probable that histohiematm is also pivsenl, and both of tleM «Sk^g
pigments hare a respirator^' function. ^^H

TuE Abachkida. ^^I

In these animals "tracheie may exist alone, or be accoo^^i-
panied by folded pnhnonarj' sacs, or the latter may eK.^^BM
aloue. as in the Scorpion. In this case these lungs* t» ■ re
supplieil by blood which is returning from the heart."

"Tiie tlow of air into and out of the air cavitiess is

governed by the contractions of muscles of the bo*^~^yi
disposed so as to alter its vertical and longitudinal dins ^^?n-

* 6«a alMllHlMtd-i paper in fait Jlcat^Aiy.&'^ea. &«^., rol. 3. p. ■^'7^

-1

PHYSIOLOGY OF THE INVERTEBRATA. 231

sioDS. In the higher forins the entrance and exit of air is
x^gulated by valves placed at the external openings (stig-
xnota) of the tracheas, and provided with muscles, by which
tihey can be shut." (Huxley.)

In some of the lowest orders of this class there is no higher
^orm of respiration than that by the general surface of the
1x>dy. In the Acarina (represented by Aoarvs), Araneina
^represented by Epdra), and the Arthrogastra (represented
"by Scorpio)y we have simple tracheal respiration in the tirst-
Tnentioned order ; in the second, respiration is performed by
Xiwo stigmata opening into tracheae, and several others opening
Into pulmonary sacs ; and in the third order, all the stigmata
open into pulmonary cavities or sacs.

In Scorpio, which is the highest of the Arachnidu^ there
are no tracheal tubes, the animal breathing wholly by pul-
monary sacs. This rudimentary lung consists of a vascular
lining membrane extended into several folds, which are in
close relationship to the margins of the openings, and thus
aflford an increase of surface for the contact of blood and
air.

Tissue-respiration,* by means of pigments (myohsDmatin
and probably histohsematin), also occurs in the Arachnida.

The Crustacea.

These animals breathe by means of branchiae, which are
highly developed in the Crustacea.

These organs contain true blood-vessels of a venous nature.
The carbonic anhydride from tissue-combustion passes out
into the water around, whilst the oxygen dissolved in the
water passes into the blood. **The access of fresh water to
the branchiae is secured by their attachment to some of the
limbs ; and in the higher Crustaceans, one of the appendages,
the second maxilla, serves as an accessory organ of respiration.
Although especially adapted for aquatic respiration, they

• MacMuDD, in Fhilof. Traiw, of Rcyal Society^ i8f 6, pt. i, p. 272.

PHYSIOLOGY OF THE INVERTEBRATA.

(branchiro) are converted into air-breatUin^ organs in tlir
land craba, being protected and kept moist in a large
chamber formed by the carapace," These branchi» are
aupplied witb blood which is returning to the heart.

The gills or branchlEC are composed of either broad lamella',
or these lamellse are divided into filaments, giving the gill its
plume-like appearance. As already stated, it is essential thftt
the water in contact with the branchitc should be constantly
changed. This change is effected by various devices. Thus,
in AiAiuus, ffomainis, and the higher Cmsiacca the branchi^
are placed in a chamber, which is bounded externally by the
branchiostegite. and internally by the lateral walls of the
thoracic segments. It is open below and behind, between
the bases of the thoracic limbs and the free edge of the
branchiostegite. Behind the anterior opening of the chamber
(on each side of the body) lies the scaphognathite (a broad
fringed organ), which moves continually backwards and
forwards, baling out the impure water of the chamber {U^
the water impregnated with CO,), and thus compelling freali I
or oxygenated water to flow in through the posterior apei
and over the branchiie.

The number of branchiae varies considerably in differ
Cmstaceana (c.;/., in Asiaeits there are eighteen in i
chamber, and in Xi-]ihrops there are twenty).

The respiratory function in all Branchvypotla is perfon
by the branchial feet; but according to Dr. G, 0. Sar8,4
there is, however, another part of the body in the Phyllo}
{i.e., in C'ychstheria hishjii) that apparently can lay cla
to a true respiratory function. Sars, as well as others, s
that the valves of the shell, which receive a considai
able quantity of blood, and their, inner delicate coatinj
seem highly calculated to produce an exchange of
with the water. The necessary renewal of the water i
effected by the well-nigh uninterrupted movements of the
legs, whereby a continual current is produced within th«

■ ChrUtiai'la Vi-Undalu-yehkob' Forhar.

tS)iJ. ^_

PHYSIOLOGY OF THE JNVERTEBRATA. 233

shell, bathing not only the legs themselves, but also the
inner coating of the valves.

Dr. MacMnnn has discovered the presence of histo-
liaamatin, myohaematin, and enterochlorophyll in the organs
and tissnes of the following Crustaceans : Homaras, Cancer^
^stacuSj CarcinuSy and Pagarus ; consequently tissue-respira-
tion* is well developed in these animals. No doubt this
Jsind of respiration plays an important part in the land
c^rabs; and, d, priori, the respiratory pigments should be
xnore largely developed in these animals than in other
Crustaceans.

The Activity of Respiration.

We owe to MM. Begnault, Beiset, and Jolyet nearly the

"^Krhole of our knowledge comceming the ratio between the

c^arbonic anhydride exhaled and the oxygen absorbed in

"^Jie Invertebrata. The animals employed in these inves-

"fcigations were allowed to remain under a bell-glass for a

^i^ertain time ; and as the oxygen of the air was absorbed, a

g=^niilar volume of carbonic anhydride was admitted into

"die apparatus. For an illustration and a description of

"C^^e apparatus used in these experiments the reader is

ferred to Secherches CJiimiqius S7ir la Respiration des

ninumx des diverses Classes by Regnault and Beiset, or to

le late Dr. A. Wtlrtz's Traits de Chimie BiologiquCy pp. 422,

-^^349 and 440.

The table on p. 234 represents the results obtained by
*lese French savants.

Ck>noeming the figures it may be remarked that among
^ bivalve Mollusca the weight of the shell naturally
iixdniflhes the proportion of oxygen absorbed, when this is
^^"^JE^rted as the gross weight of the animal.

See also a recent paper on " The Respiration of Cells in the Interior of
'^^ses of Tlsrae/' by M. H. Devanz, in Compter Jiendw, vol. 112 [1S91].

PHYSIOLOGY OF THE INVERTEBRATA.

ill

ISO

12.S

<">S47

o.»

Gammarui 2ivlex .

■IS

0.1 901

0.7*

395

ai8co

aSj

Cancer pos,irv$ . . .

470

aiS4i

a84

Sbmonii valgarit

315

•s

0-0979

aSo

Pdtinvrui qiiadricorniii

•s

00636

aS8

Oelopui vu!i/ariti .

2310 1 15.S

0.0636

ajoo

0x1636

afis

S .' Cardmm tilule

127

'317

•5

o.oai3

a84

1 1 Slgtlh, tMU . .

1500

0.0176

aT*

[OttTta tdulit

i83S

'3-S

0.0193

aj9

■ iSirvdo medicinalu

104

*35

'3-5

0^33'

a86

S ' I. .< 5 days after j

^ i blood ]

104

235

0.057a

a*)

Zoo- 1

,».(-'"""°"*"'"'"' •

9CO

0.0461

a79

The next table represents the results of a further s
experiments by the same authorities :

I III

nil

°ii

40 40.3 0.0472 j 0.0434 ;
18 1 42.5 0.0388 j 0.0357 I

43—1 0.0478 ' O.046S

— I 0.00446 1 0.00508'

.1:1

'I"'

PHYSIOLOGY OF THE INVERTEBRATA, 235

Among the results which have been observed by MM.
fiegnanlt, Reiset, and Jolyet are (i) that the amount of
oxygen contained in the carbonic anhydride exhaled is
smaller than that of the oxygen absorbed. (2) The respira-
bion of insects, when these animals are in full activity, has
;lie same energy as that of the higher Vertebrata ; while the
^rthworms do not respire more than reptiles. (3) Respira-
ion in the Invertebrata diminishes (as a rule) in proportion
ks the temperature is lowered. This is because these animals
bre incapable of producing a safScient internal warmth, and
K^nsequently they become gradually colder until the move-
laent when they fall into a state of hibernal sleep, or die.
^) After feeding, most Invertebrates (and particularly the
Wnsectd) respire more energetically than, at other times.
^5) All animals subjected to habitual regimen always expire
^ little more nitrogen than is contained in the air inspired.
^6) In inanition, the absorption of oxygen and the exhalation
^f carbonic anhydride are greatly diminished. The fewer
bhe functions exercised by an animal, the less carbon it
expends.

Dr. Moleschott* has shown that the action of light upon
fche skin notably augments the intensity of the respiratory
phenomena.

In general terms it may be stated that "behind every

Ibiological activity there is an oxidation of the anatomical

elements. No organ escapes this law, and the nervous

centres are as much in subjection to it as the other organic

mpparatus. Every thought, eveiy volition, every sensation,

<X)rre8pond8 to an oxidation of the living substance, as well

as every secretion, every movement, &c."

The Polyzoa.

In this Class we have probably the representative of the
fi^t stage in the evolution of the respiratory apparatus of

* Wie-Rtr Medicinitche Wochenachriftj 1885.

23& PHYSIOLOGY OF THE TNVBRTEBRATA.

the lower Vcrtcbrala. In these aniinals the stractnre (»*■
special interest is the dilated pharjiix (see Fig. 17).
amstant stream of water enters the mouth and passea inlt^
the pharynx, whose walls are richly supplied with blood — "^
vessels, and it ia throngh the walls o£ the pharynx tha^^^
absorption takes place. The tentacula serve as an acceesoij "^"^
organ of respiration.

In the Polyzoa the protruaible parts of the body alfo*^^^^*
absorb oxygen from the surrounding water, &[acMunn haoM'^"^^
examined LcpraOa. foliacca and finds that it contains saM-^^
abundance of chlorophyll mixed with a lipochronie. The^^-**
chlorophyll is also accompanied by a second pigment,,,-^*''
probably chtorofucin. Fhistrri foUarca also contuns a chJoro-— ^^J
phylloid pigment. ^^^

The BitACPnoPODA. ^H

In these animals the blood is contained in branched .^&**

sinuses in the perivisceral cavity. In the sinnseB of the^*-*^
ciliated tentacle-bearing arras and of the inner wall of thft^*-*"
mantle, the blood is purified by being brought into close eU*^
osmotic relation with the water in which these animals live.

\'ery little is known concerning the presence of respiratory 1^^
pigments in the Brarhiopoilu. ^H

The Mollusca. ^H

The aquatic Mollusca have weli-developed branchiie nsnally "^C-
enclosed within branchial chambers. These branchiae are brood ^^^
and plate-like ; and the water in contactwi-ith them iachanged M-*^
by means of vibrating cilia. In the Branchitujaslcropoda the ^^-*
branchiio are dendritic, instead of plain and plate-like.

The Crplttdopodn are divided into two distinct orders

the Dibraiu'hiatii with two gills, and the TctmbraiwhiaUi-^c:*'^^
with four gills in the mantle cavity. The water is condnctedt* "^
to the branchial chambers of the Dihraiiehiata (which ia tL^»-*^
highest of the two orders) by means of the infundjbulunc*::*''''
whose opening is situated beneath the head.

PHYSIOLOGY OF THE INVERTEBRATA. 237

In the Pteropoda " the delicate lining membrane of the
pallial cavity serves as the respiratory organ."

The mantle is also ^* an accessory organ of respiration,
being so modified as to direct, or to cause, the flow of currents
of 'water over the branchiae contained in its cavity."

In the Pulmogasteropoda (air-breathers) *' the lining wall
of the mantle cavity becomes folded and highly vascular,
aixd subserves the aeration of the venous blood, which flows
tl:unotigh it on its way to the heart. The lung is here a
miodification of the integumeut, and might be termed an
o^rfcemal lung The lungs of the air-breathing Verteh^ata^
00. the contrary, are diverticula of the alimentary canal;
• • • . and the blood flows from the heart."

Ihe membranous respiratory sac of the Pvlmogastvropoda
^ not morphologically a true lung, as it is developed from
*»^e integument ; but it may be physiologically regarded as
^ Yadimentary lung performing a similar function to the
*^^e Vertebrate lung which first appears in Pisces*

^' Many animals are truly amphibious, combining aquatic
^^d aerial respiratory organs. Thus, among Molluscs, ^???-
^'^^Maria and Onchidum combine branchiae with pulmonary
^^^^fians." (Huxley.)

The Polmogasteropod lung is the simplest form of lung to
met with in the animal kingdom. It has been compared
"a single so-called air-cell of the Mammalian lung. In
case there is an internal cavity lined by a delicate
*-^embrane supplied with impure blood, and having air in
^^^>ntact with its free surface."

l^ae-respiration is wonderfully well developed in the
ToUuseOj for MacMunn has discovered an abundance of
^^spiratory pigments in these animals.

In Ostroea, Uhio, Anodonta, Mytilus, Limnccus^ Paludina^
^"^^atellaj Purpura, Zittorina, HelijCy Limax, and Arion, histo-

* In Lepidonren (mud-fish) there is a transition from the piscine air-
T^^adder to the Reptilian form of lung. The air-bladder of the fish appears
be chiefly a hydrostatic organ, or rather an accessory one of respiration.

.3 }

238 PHYSIOLOGY OF THE INVERTEBRATA.

lieematins have been discovered in various parts of the bodj \
and hemoglobin occurs in the pharyngeal muscles of ih*
following Molluscs: I^irpitm lupillim, lAVoriim littorfC*-^
Trochus cinerarius, Paidla vuhjuta, LimncEiiS sUtgiutlu, an^
Pdlici/ina vivipara.

MyohiEmatin is the histohfematin charaoteriatic of la. ■ —
vei*tebrate maacle, bat in the above-mentioned species Aij^*
pigment is replaced by hiumoglobin.* This proves tha- ^
the histoh;tniatina are connected with hfemoglobin and it=- '
derivatives.

ityohitmatin occurs in all the Pidmoiiasleropoda esamise^^
by JIacMunn. " JlyobKuiatin is the true intrinsic colounn^^EK
matter of muscle, and the hiatohseinatins the intrinsic colour -^-
ing matters of the tissues and organs ; both may be reinforcec^^^
or replaced at times by hajmoglobin when extra activity o
internal respiration is required; probably the same radici -
may be made use of for building up all these pigments, fo^
they seem to be related, since the same decomposition prridnts:
— hEomatopovphyrin— is probably yielded by all of thei
The J'act that in the lower animals pigments of less compie=:^'^
molecular structure than hasmoglobtn and identical 1
decomposition products can function like it, forces itsel-'
on anyone's attention who studies the pigments of th^
Invcrttbrata."

MacMunn has extracted htematoporphyrin from the in--
tegument of TAinax Jlarus, Limtu rarii\gatu8, Arian aicr, aac*
SolixiirUis strigillatus. With the exception oi SuifcuTttis,'a.
all these Molluscs enterohasmatin is found in the so-callfO*"'''^
liver (pancreas), and histohiematina in various tisanes ant^ *^
organs, and there can be no doubt, as MacMunn states, ihu ^~"'
here also the ha;matoporphyrin is a metabolite of ties»-^* *
pigments.
iThe 80-oailed livers of the : following Molluscs contaii*-*-^
euterochlorophylls which are identical with Kru ken berg' ^^'^Sf
hepatochromates: OsCrwa, Bitccinum, Fitsii.t, Mtftiliis, Cardiunf
* The blood of Saien Uyumen cotttaiDS bamoglobiii (LanlcMter}.

PHYSIOLOGY OF THE INVERTEBRATA. 239

nod(mJta^ UniOj Octopus, Paltidina^ Limnoeus, Patella, Helix ,
urpura. Avion, Limax, and Littorina.

The enterochlorophyll occurs dissolved in oil globules, also
. the granular form, and it is sometimes dissolved in the
rotoplasm of the secreting cells of the so-called liver. In
bemating snails, these pigments occur in greater abundance
. the winter than in the summer time.

In concluding these remarks on the principal colouring
attera of the Molltisca, we may state that enterohsematin*
xmrs in the " livers" of Helix, Liviax, Arioii, and Patella;
id MacMunn believes that enterohsematin is probably the
jother-substance of those histohiematins, which are found in
limals in whose " livers " it is built up.

The Tunicata.

In the Pharyngopneustal Series (Enteropneustra and Tuni-
Ua) a new form of internal aquatic respiratory organ
ppears. The dilated pharynx of the Polyzoa is farther
eveloped in these animals, being perforated by lateral open-
igs. These openings are ciliated, and a constant stream of
ater enters at the mouth or oral aperture, which passes into
le pharynx through the openings (branchial cleflbs), then
ito the atrial chamber (which is developed round the
harynx), and out of its aperture into the air in which the
nimal lives. As in the Polyzoa, the walls of the pharynx
pe well supplied with blood-vessels.

The Tunicata have been called sea-squirts, for if they are
rritated they suddenly contract the muscular walls of the
ody, and this contraction causes the water contained in the
trial and branchial cavities to squirt out in two jets. It may
e remarked that the late Mr. Darwin considered the Tunicate
s the representative of the point at which the Vertebrata
i^an to work off from primordial forms common to it and to
he Mollusca,

* Enterohscmatin is synoDTmous with hscmochromogen and helico-rubin
f Krokenberg.

PHYSIOLOGY OF THE INVERTEBRATA.

BrG. MocMuDn and Krukenberg have extracted eevenl
lipochromes from these animals.

In conclnding our account of the function of respiration in
the InvcrUhrata, we may summarise the contents of this
chapter in the following mannerr — (r) There is respiration
by the gensral aurface of the body, (2) Heepiratioa by
air dissolved in water. In this mode of respiration the
respiratory organs are either internal (contractile vacnoles.
water- vascular systems, pseudo-hEDmal vessels), or external
(gills). (3) Respiration of air directly; this mode bein;!
performed by three distinct mechanisms, of which the first
is the respiration of air (not dissolved in water) by the
general surface— i.e., cutaneous respiration. The second is
by means of the tracliece or air-tubes ; and the third by
pulmonary sacs or rudimentary lungs.*

In addition to the above modes of respiration there is also
tissue-respiration by means of various pigments. These
pigments are capable of retaining oxygen within the system, .
and no doubt they play a most important part in the respira-
tion of the Ijirertebraia ; and possibly they play a more s
important part in these animals than in the Verkbrafa, where ^
the respirator}' apparatus becomes highly differentiated into ■«:
powerful and special organs.

* Gills lirst appear in the FtAyAuita, tracheal tabes in the Stpiapoda. ^-m
andarudlmcutary "long" Srat makeB its appearance Jn the iWnnfiutnw- ^

CHAPTER IX.

SECRETION AND EXCRETION IN THE INVERTEBRATA.

Jlll living organisms assimilate and disassimilate incessantly^
l>at the conditions of assimilation become more complex as
^we ascend in the zoological scale. For the accomplishment
of the function of assimilation in the higher forms, auxiliary
apparatus, such as those of digestion, circulation, and respira-
t^ion, are needed. The last three mentioned functions have
sJready been described, but in addition to these there is
another, for the waste products of the cells, tissues, food, &c.,
liave to be eliminated from the system. It does not matter
Iiow low the organism is in the scale of animal life, there
mre always waste products formed, and these have to be
eliminated, or they act as poisons. The function of elimina-
^on of matters hurtful to the animal organism is spoken of
CIS excretion. Excretion is partly mechanical — as in the
evacuation of the faaces — partly dependent upon the physical
X>roces8 of pressure forcing fluid matters through thin-walled
'tiubes, and partly upon cell development and growth, as in
secretion. In the higher animals secretion is performed by
:five separate mechanisms — the kidneys, the intestines, the
lungs or branchidB, the liver, and the skin. The excretion
of carbonic anhydride and other gaseous products by respira-
tion has already been alluded to in the last chapter. The
function of excretion by means of a liver does not occur in
'the Invertebrata, as a true liver (similar to that occurring in
'the Vertebrata) is absent in these animals. From these
xemarks it will be seen that, so far as excretion is concerned

242 PHVSiOLOGy OF THE INVERTEBRATA.

the present chapter will be vMrfly confined to a description
of excretion by means of renal or urinary apparatuses.

Besides the waste products there are several useful prodncts
of katabolism termed urcniions — such as saliva, digestive
juices, &c. The principal secreting organs' of the Inrtrtr-
brafa have already been described in the chapters on diges-
tion; but it may be remarked that in reality the secreting
glands are at the same time organs of excretion. All of
them take from the blood, or nutritive fluid, water and salts,
substances to which they offer a passage without in any '

respect changing them. In addition, however, they form, ^^"^^1
the expense of the sanguineous materials, a special nitro- *J

genous product, the principal agent of these chemical tntna '

formations being the epithelial cells. Such a product is 8^^»*
secretion.

When neither the epithelial cells nor the walls of a glani^^^'-^
exercise any modifying action on the materials of the bloo^^^^
or nutritive fluid, but simply act as a filter, offering a pBssag^^"^^
to certain substances and refusing it to others, there ismerelj^^-"/
excretion.

The excretory organs are never closed, for they a]w«y»"^Cf*
pour externally the humour which they filter. This hnmoni: *^*''
is a dead product — the residuum of nutrition— whose expul— -^^ *'
sion is necessary to preserve life. The excrement it ioos «=*"
humours, of which the urine is a typical examjile, are solel*^ ^"3
constituted of water holding in solution certain salts, anc^ *-"
crystallisable nitrogenous substances, which, formed in ti» *-*'
anatomical elements themselves by disassimilation, pass firs** -"
of all into the blood or its representative, whence they ar*"^*-^
extracted and excreted by various mechanisms which in th*-*^*''
higher forms are known as glands.

The organs specially ctmcemed in the elimination tfc^^ **

excretion of nitrogenous substances are t«rmed kidney^^"^'

and in the IiLcertchruta the form of these organs vari^^ -"^

* Special orgtuu of this nature will be alladed lo later in the prete*^'^^''

PHYSIOLOGY OF THE INVERTEBRATA. ' 243

considerably. In the Protozoa they are represented by the
contractile vacuoles, which perform other functions besides
that of a renal organ.

In the Porifera the waste materials of each cell are thrown
into the body cavity, and collectively expelled through the
exhalent aperture, or osculum ; a somewhat similar mode of
excretion is observable in the Codcntcrata.

The renal organ of the Eddnodernuita, represented by the
Asteridea, is the five pouches of the pyloric sac (see later in
this chapter). Here there is a fusion of digestion and excre-
tion. The water-vascular system, which in other forms
performs the functions of excretion and respiration, has a
locomotor function in the Asferidca.

In the Cestoidea and allied orders the water-vascular
system opens into the blood system on the one hand, and
communicates with the exterior on the other. The water-
yascalar system is in these animals the representative of an
excretory organ.

The segmental organs, or nephridia, of the Annclidit are
true kidneys, and form a medium of communication between
the circulatory apparatus and the environment.

In the air-breathing Arthropods, as well as in some
Crustacea {Orchcstia)^ the kidneys are represented by the
Malpighian tubules — appendages of the intestine.

The shell glands of the lower Crmtcicea have a similar
function to the segmental organs of the Annelida; conse-
<)U6ntly they are renal organs.

The organs of Bojanus in the Lamdlibranchiata are more
or less complex sacs or tubes, joining the blood system on the
one hand with the exterior of the body on the other. They
Tesemble the [segmental organs of the Amuiida^ and perform
<a similar function — namely, the elimination of waste nitro-
^nous matters from the system.

The renal organs in the Lamcllihramihiata form a paired
Udney ; in the Pidmcgastcropoda, represented by Helix, the
kidney is unpaired, being a single renal sac ; but in both

244 ■ PHYSIOLOC-Y OF THE INVERTEDRATA.

of tbeee orders of the Motlnsca the renal organs conmmnicale
by means of an internal opening with the pencardial divisioa
of the body cavity.

Finally, in all the Inreftebrotf the blood syatem is not
completely separated from the general cavity of the body,
and the general cavity of the body has openings placing it in
communication with the exterior medium.

In the VerUhrata the urinai-j- organs consist essentially of
a number of coiled tnbes, and open to the exterior by specia)
openings, which are usually common to the generative organs.
■■The individual tubules of which the Vertebrate kidney is
composed do not open dii'ettly to the exterior, as do the
segmental organs of the Annelids, but there is present on —^
each side of the body a duct- — a kidney duct — which receivev-i_3"
the tubules of its own side, and opens posteriorly into the^^i^*
cloaca. They also possess an important structure peculiar:*"-^
to the kidney of the Vertetirctn, known as the Malpighian«i:«'-o
body, which consists of a capsular widening of tie lumemi»^^*
of each tubule, into which projects a coil of arterial blood— -^3"
vessels known as the glomerulus."

Besides the excretory or urinary organs, there is anotJiew^»w
class of secretorj' apparatus which must be alluded to — w^"^^^"*
refer to the unicellular and multicellular ijitrifumeniari/ organssa *"•
These are found largely represented in the Insecfu, and thejC.^^*^
belong to the category of oil and fat glands, whose function:* ^^^
is to lubricate the integument and its special coverings.

" Aggregations of cells whose function is to secrete cal--^-^^'
careous matters and pigments" are especially widely preseuf -**^^'
in the integument of the Mollvmi, and serve for the building. *^*'f
up of the beautifully coloured and variously shaped shells o<=^* "
these animals."

' Dr. MBcMnDUbBs ttownlhat whcneverba;aiochrom<^enispresent ir-* •"
the fluids and organs of the body, it hfts been produced by eicretfon : it-*"
other words, it is an exrretory pigment. But there is one exccrplioD
namclj, in a, beetle (Staj)li<ill«ia o/iNt), as ita testes i
substance with haemoglobin.

PHYSIOLOGY OF THE INVERTEBRATA, 245

But this power of secreting exoskeletons is not confined to
the Mollusca; even in the Protozoa calcareous and siliceous*
exoskeletons are secreted by the cells acting in the first
instance on the calcium carbonate and silica dissolved in the
water in which these animals live. " The hard protective
skeletons in all Invertebrate Metazoa, except the Porifera^
the ActinozoUf the Echinodennata^ and the Tunicata, are
cuticular structures, which may be variously impregnated
with calcareous salts formed on the outer surface of the
epidermic cells. In the Porifcra, the calcareous or siliceous
deposit takes place within the ectoderm itself, and probably
the same process occurs, to a greater or less extent, in the
Actinozoa, In those Tunicata which possess a test it
appears to be a structure sui (/enerisy consisting of a gela-
tinous basis excreted by the ectoderm, in which cells
detached from the ectoderm divide, multiply, and give
rise to a deposit of cellulose."

*' In the Actinozoa and the Echinodcrmata the hard skele-
ton is, in the main, though perhaps not wholly, the result of
calcification of the elements of the mesoderm. In some
Molluscs, portions of the mesoderm are converted into true
cartilage, while the enderon of the integument often becomes
the seat of calcareous deposit."

Besides the various glands, cells, and devices secreting
and excreting calcareous, siliceous, and gelatinous materials,
integumentary glands and aggregations of glands may also
acquire a relation to the acquisition of food ; as, for in-
stance, in the spinning glands of spiders. Finally, mucous
glands are very widely present in the integument of animals
which live in damp situations (snails, &c.), and in water
(Annelids, Medtcscc, &c.).

At this point we intend to describe in detail the excretory
or renal organs, as well as to allude to certain important

• See alBO Murray and Irvine's paper in Froc. Jioy. Soc Edlnb., vol. i8,
p. 229 (1S91).

PHYSIOLOGY OF THE INVERTEBRATA.

secretory organs
forms of the //(i'(

as we pass from the lower to the hi^er

Thk Protojioa.

The author" has shown that the contractile or pulsating
vacuole of the Protozoa performs the function of a tme
kidney, or, in other words, its secretion is capable of yielding \

microscopic crj'stals of uric acid.

Three organisms were used in the author's experiment*^
namely, Amahi, VorCiaHu, and Pintimaci/'w.

(i) Arruehfi. — ^By observing a number of these or^anisiu^^^
under the higher powers of the inicroscope.t there is seen .^m-
within the structure of each, a small cavity or vacuole fille*-^ '*
at certain times with a transpareiit fluid, ITiere is littW -^'-'
doubt that the fluid which collects in the vacuole is drawer -sn
from the surrounding protoplasmic substance, and is retnme*— ^**
to it, or forced out to the exterior on the contraction of tb .«iA'"
walls of the vacuole.

The author has shown in his paper, "Further Researclie^^ -•*
on the Physiology of the Invertdn-ala,"^ that the fiv —'■^' ■*"*
pouches of the Astrni/ra also perform the function on* •"
kidneys (/.;■., the digestive apparatus performs a dni^ •^*'
function); and whatever may be the multitudinous fimci:^*^'''
tions of the Protozoan contractile vacuoles, one thing ii ^
certain, that they excrete periodically a waste nitrogenoK^^ *— ""
substance. This nitrogenous substance was proved to hcf '"
uric acid.

A number of Aviabf were placed on a microscopii^^^'
slide and covered by a thin cover-glass. Alcohol was ro:*^* '"'
in between the slide and cover-glass, so as to kill IIl***-*
organisms. It was found that in many cases moderatel i^^^'J
weak alcohol caused no contraction of the vacuole. Tli«^ .'
alcohol was followed by nitric acid ; the slide gentl
■ Proaediiigt 0/ Jtoyal Socleti) 0/ Eillaburgh, rnl. 16, p. 131,
f Zeisa'fi S and uc. v j F and oc. iv and v.
{ Profeeiliiig* of Si<yal fhcirti/ 0/ London, vol.44, P- S^i-

PHYSIOLOGY OF THE INVERTEBRATA, 247

wanned, and finally, ammonia introduced between the slide
and cover-glass. In a few minutes prismatic crystals of
murexide,* of a beautiful reddish-purple colour, made their
appearance. After the addition of alcohol (as already stated),
minute flakes were distinctly seen floating in the fluid of
certain contractile vacuoles. Bearing in mind the murexide
reaction, there is every reason to believe that these flakes were
minute crystals of uric acid.

It may be stated that there are times when the fluid of the
contractile vacuoles does not contain the least trace of uric
acid. These vacuoles perform mor^ than one function, one
of these being that of an internal respiratory apparatus (see
last chapter) ; and now we find the same organ performing
the function of a kidney. There is little doubt that the
contractile vacuole of Amceba is the primitive representative
of a series of organs which become gradually differentiated in
the higher forms of the Invertehrata,

(2) Vorticella, — ^The contractile vacuole of Vorticella ex-
hibits during life fairly regular diastolic and systolic move-
ments. The fluid which it contains is drawn from the
surrounding protoplasmic matter, and is ultimately forced
by the contraction of its walls towards the periphery of the
bell, and finally ejected ii\to the water in which the organism
lives. The contractile vacuole of Vorticella performs the
function of a true kidney. Its fluid contents yield micro-
scopic crystals of murexide and uric acid when submitted to
the same chemico-microscopical reactions as those just de-
scribed.

(3) Faramomum. — The cx)ntractile vacuoles of this organism
are situated in the ectosarc almost at each end of the long
axis of the body. These cavities are filled with a transparent
fluid. During the systole fine radiating canals are produced,
which probably communicate with the exterior. The con-
tractile vacuoles of Paramecium are at times the renal

* The crystals had a green metallic lustre when seen by reflected, and a
reddish-purple colour by transmitted light.

248 PHYSIOLOGY OF THE INVERTEBRATA.

organs of this organism. By the same reoctioaB as those
described in connection with Awitha the tioid of these
\acnoles yields crystals of nmrexide and uiic acid. Thew i*
little doubt that these vacuoles eliminate tha waete nitro-
genons products during the systoles which take place
periodically.

In these three primitive forms of the animal Hngdoin
there are the rudiments of a true renal system. The con-
tractile vacuoles peri'orm the same function (among otherfi)
as the kidney of higher forms, by yielding the same nitro-
genous substance which is present in the renal organs c^^
the highest Vertebrates. By the agency of living prott^ — '
plasm, even these insignificant microscopic cells bring aboi^^^
chemical metamorphoses in albuminoid molecules, with th -**
production of uric acid and possibly other substances. Ic^ -^
these lowly creatures there is present the same power cn:^^
chemical metamorphosis as is present in the more complei^'
cells of the highest Vertebrate. But the contractile vacnote ■
do not represent solely the renal organs in these forms, fo*
it is by their agency that the mechanisms of respiration an^-*^
nutrition are performed. The Protozoan cell performs man^-*^^?
functions, and in this respect it does not altogether diffe^^^^'
fram specialised cells of the higher animals. It should b»-*^"*
borne in mind that " there is no perceptible relation betwee*
the nature of the fluid and of the cell or gland secri.'ting it
iiud secretions, as pus, for example, are formed by structur*-^
where no such secretion previously e.xisted ; they alter als«
without any visible change iu ihe structure of the gland o
cell " (Milne Edwards).

The CtELENTERATA.

As the means of eliminating the waste products in
roriftra and the C'tdtiiUraiii have already been referred to
this chapter, we now proceed to describe the secretion
carbonate of lime in the Ccelenterata.

PHYSIOLOGY OF THE INVERTEBRATA, 249

'' The vast organic accumalations known as coral reefs are
nndoabtedly among the most striking phenomena of tropical
oceanic waters. The picturesque beauty of coral atolls and
barrier reefs, with their shallow placid lagoons, and their
wonderful submarine zoological and botanical gardens, fixed
at once the attention of the early voyagers into the seas of
equatorial regions of the ocean."

What delight and pleasure a '* Captain Nemo," with his
submarine boat,* would have in visiting these zoological and
botanical gardens, witnessing (among a hundred or more
interesting phenomena, not dreamt of in man's philosophy)
the Holothurio} and Scari feeding upon coral-polypes, &c.,
and grinding the coral into such a fine mud that it may be
more easily re-dissolved in sea wat^r, and thus furnish a
new generation of lime-secreting animals with the necessary
lime.

It is not our object to describe the theories of Darwin t and
Murray t on the origin and formation of coral reefs and
islands ; but to give the chief points of interest concerning
the recent investigations of Dr. J. Murray and Mr. R. Irvine §
on the *' function of corals and other lime-secreting organisms,
and the accumulation of their shells and skeletons on the
floor of the great oceans." The conclusions arrived at are
the following : —

(a) " Coral reefs are developed in greatest perfection in
those ocean waters where the temperature is highest and the

animal range is least Throughout the temperate

and polar regions there are no coral reefs. This is all the

more remarkable, seeing that organisms belonging to the

same orders, families, and even genera as those which build

Up coral reefs, flourish throughout colder, and even in polar,

seas. In these colder seas the representatives of the reef-

• Jules Verne's Tuyenty Thousand Leagues under the Sea^
t The Structure and Distribution of Cored Beefs.
J Proceedings of Hoyal Society of Edinburgh^ vol. 10, p. 505.
I Ibid., voU 17, p. 79.

250

PHYSIOLOGY OF THE im'ERTEBRAtA.

builders either do not secrete carbonate of lime in their bodj-
walls, or, if they do so, the skeletons are mnch less maaayf
than in tropical waters." No doubt this difference in lie
fnnction of lime- secreting is partly due to the direct action
of the environment, and partly to natitml selection. Mr.
Herbert Spencer, iu his I'rinnph's of Biology, has point«d
out the influence of the environment on the simplest tmi-
cellular organisms, tracing it up to more and more complex
organisms, and he has further shown its struggle with
atavism, or the principle of heredity, so strongly possessed
by all animal and vegetal cells. There is everj' reason to
believe that the direct action of the enviroument has in-
fluenced the protoplasm of the representatives of the coral-
polyps living in cold seas, so that it no longer possesses th^
same power of secreting carbonate of lime.

(i) ''In descending into deep water in equatorial regitai^s
the amount of carbonate of lime secreted by the anlma^B
living on the sea bottom becomes less with incressin -*
depth,"

(f) "The number of species and individuals of lim^
secreting organisms decreases" with the distance from ll*-*
equator. It appears that these organisms "secrete mor:
lime in regions where there is a uniformly high temperatnr"
of the ocean water than in those regions where there ar"* ^ .
great seasonal fluctuations of temperature, or where there ■
a uniformly low temperature of the water, as in the polaj
regions and in the deep sea." ,

((/> " In temperate seas more carbonate of lime is secrete*-^*"*!
in the warm summer months than during the winter month» **
Indeed, a high temperature of the sea water is more favonr*-*-^
able to abundant secretion of carbonate of lime than higr*;^^ *
salinity."

(f) " The average percentage of carbonate of lim

K0&t

nth'*:*-

v-holr of fill- ilrjiosif.^ covering the floor of the ocenn is 36"8^
and of this carbonate of lime, it is estimated that fully g^
per cent, is derived from the remains of pelagic oi^nisir*

r ^3-

PHYSIOLOGY OF THE INVERTEBRATA. 251

that have fallen from the Burface waters, the remainder of
the carbonate of lime having been secreted by organisms
that live on or are attached to the bottom."

(/) Sea water collected among coral atolls contained
nearly twice as much salts of ammonia as water from oceans
where the coral polyp does not live. It appears that the
carbonate of ammonia present in sea water arises from the
decomposition of animal products, and in the presence of
sulphate of lime of sea water becomes carbonate of lime and
sulphate of ammonia :

(NHJ,CO, + CaSO, = CaCO, + (NH,),SO,.

^' The sulphate of ammonia is in turn absorbed by the
marine flora which form the food of the marine fauna, and is
in part resolved into nitrates and free nitrogen."

*^ The whole of the lime salts in sea water may be changed
by the above reaction into carbonate, and may in this way
be presented to the coral and shell builders in a form suitable
for their requirements. The temperature of the water is of
great importance in this reaction. In cold water, of which
the great bulk of the ocean consists, the decomposition of
nitrogenous organic matter is greatly retarded ; whereas in
tropical surface waters it proceeds with great rapidity.
Here, then, we have probably the explanation of the massive
structures formed by lime-secreting organisms in the coral
reef regions, which are also the regions of highest and most
uniibrm temperature in the ocean. In the same way we may
account for the great extension of lime-secreting pelagic
organisms in the tropical surface currents that flow north and
south from the equator. Thus the coral reef-builders and
pelagic organisms may not only benefit by the decomposition
products arising from their own effete matters, but also from
the undecomposed nitrogenous matter carried to equatorial
regions from the cold water of the deep sea or from the polar
regions."

{g) As the quantity of carbonate of lime in sea water is
exceedingly small, it was supposed that the lime-secreting

aja PHYSIOLOGY OF THE TNVEfiTEBRATA.

organisms pamped enormous qaaatities of sea-n-ater tliroQ);h
their bodies so as txi be able to separate ont a snfficiem
(luantity to form their shells and skeletons.* But there is no
doubt that we have a correct explanation in the rfsetiona
indicated above wliich have been so ably investi^t^d by
MuiTay and Irvine, " In higher animals, like hens, the
carbonate of lime is secreted from the blood ; bat in coral
polyps, in which there is no true circulatory system, and
where the animal is immersed in the sea water, it is most
proljable that the reaction above referred to — the formation
of carbonate of ammonia — is in eveiy way advantsgeoas lo
these lime-secreting organisms, and facilitates the depositidu
of carbonate of lime by the protoplasm. In the case of »"
the lower classes of lime-secreting organisms this change in
the constitution of the limo salts may take place withiu the
tissues of the animals." In fact, Murray and Irvine have
shown, in their experiments with oysters, that " the excess of
carbonate of lime observed in the liquor or diluted Ijmpt*-
was clearly due to the decomposition of the sulphate of lim^'^
in the sea water by carbonate of ammonia secreted as snct^^-^
Ijy the protoplasm of the animal,"

It may be stated that when sulphate of lime, urea, an^^^j
water are heated together to about So° F., carbonate of lim«^
and sulphate of ammonia are formed : — ■■ ■

CaSO. + CH.N.O -f 2H,0 - CaCO, + (NH,)^0,.

It is possible that the excretions of marine Invertebrates, .
as well as those of the higher animals, ultimately yield car-
bonate of lime and sulphate of ammonia due to the action of^^^
the sulphate of lime in sea water,

(/() Murray and Irvine have also shown that the rate of^^^
solution of dead carbonate of lime shells and sfceletous bytbe^^-*^
action of sea water " varies greatly according to theconditions*-*^
in which these dead remains are exposed to the solvent' ^*-^
power of the water." The following table gives a few o^z:^^
their results : —

* fiiuhofi Chtmieal and PMygica! Oedeiry, *ol. I, p, t8o>

PHYSIOLOGY OF THE INVERTEBRATA. 253

nd . • .
* mud, Bennada
a dip$aeea •
a ramoia
tra (upera
rafolio$a
'tea mvitilobata
iavaria . •
coronalit .

H
is

Amount lolable.

In grammes,

lime carbonate

per litre.

0.0320
0*0410
0.0410
0.0360
0.0730
0.0430
0.0730
0.0930
0.0237

In parta of sea

water.

One part in

32,000
25,000
25,000
28,000
14,000
23,000
14,000
11,000
42,600

:periments prove that '* there is very great diversity
) amount of carbonate of lime that will pass into solu-
sa water from various calcareous structures in a given
The more dense varieties of coral are less soluble
e porous varieties. " The rate of solution is also
reater when the water is constantly renewed than
e same water remains in contact with the coral, and
bion approaches to saturation."

•cm the investigations and observations of Murray
ne ** it is evident that a very large quantity of car-
f lime is in a continual state of flux in the ocean, now
in the form of shells and corals, but after the death
animals passing slowly into solution, to go again
the same cycle."

the whole, however, the quantity of carbonate of lime
tecreted by animals must exceed what is re-dissolved
iction of sea-water, and at the present time there is a
amulation of carbonate of lime going on in the ocean,
leen the same in the past, for with a few insignificant
»ns all the carbonate of lime in the geological series
ocks has been secreted from sea water, and owes its
o organisms in the same way as the carbon of the car-
ms formations. The extent of these deposits appears

254 PHYSIOLOGY Oh THE INi'ERTEBRATA.

to have increaaed from tUe earliest down to the present
geological period."

The Echinodermata.

We have already alluded to the secretion of the protoctiw
skeleton in these animals ; conaeqaently we proceed %i
describe the excretory organs of the Astcridea, being an im-
portant order of the Ei-MiUMlcrnMta, -

The autboi' • has shown tliat the five sacs of the stomajli
of Untatf}- rnlfn-'i sometimes act as renal oi^aos. With »
<|uantity of the flaid obtained from a large number of staf '
lishes the following experiments were performed : —

(i) The clear liquid from these sacs was treated with ahc^^
dilute solution of sodium hydroxide. On the addition of pur""^
hydrochloric acid a, slight flaky precipitate was obtainec::;^^^*'
after standing seven and a half hours. These flakes, whe*-" ^
examined beneath the microscope (i in. obj.) were gqen t-^^^"^
consist of varioiia crjstalline forms, the predominant forro*^^*'^
being those of the rhomb. On treating the excretion alon».^^**^
with alcohol, rhombic crystals were depodt«d which •Kfim"^
soluble in water, Wlien treated with nitric acid and thee* ^^^
yently heated with ammonia, these crystals yielded reddish— **'
purple murvxide crystallised in microscopic prisms.

(2) Another method was used for testing the flnid contenti^'-*^
of the sacs of the stomach of t'mstfr. These flnid con ten t*^;*'-*'^
wen.' boiled in distilled water, and evaporated carefnlly fa^^*' *
dryness. The residue obtained was treated with absolut^>-^ ^
alcohol and filtered. Boiling water was ponred upon th»-*^'
residue, and to the aijueous filtrate an excess of acetic acic^-* '"'
was added. Aft*r stauding some hours, crystals of une («*»-S**'
were deposited, and easily recognised by the chemio-miero ^r"^
soopical tests mentioned above.

The nbove-inentioiied alcohcJic filtrate was tested for ore^^^*-

* Sm Dt. A. B.arialUw' paiwr iafVM*(J^«'AjyW jfxMTy. ToLf

PHYSIOLOGY OF THE INVERTEBRATA. 255

0 this, the alcoholic solution was diluted with distilled
r, and boiled over a water-bath until all the alcohol had
rised. The warm aqueous solution (A) remaining was
tested for urea in the following manner : —

) On the addition of mercuric nitrate to a portion of the
e solution, no white precipitate was obtained.

1 To another portion of the solution (A), a solution of
im hypochlorite was added. No bubbles of nitrogen

disengaged.

I No crystals of urea nitrate were formed in a small
itity of the solution (A) [concentrated by evaporation]
* the addition of nitric acid.
) The distillation of a small quantity of the solution (A)

pure sodium carbonate in a chemically clean Wtirtz's
; attached to a small Liebig's condenser, failed to produce
16 distillate any coloration with Nessler's reagent.
lie above tests clearly prove the entire absence of urea
16 excretion under examination. No guanin or calcium
iphate could be detected in the excretion, although the
or has found the latter compound as an ingredient in
renal excretions of the Cephalopoda and the Zamdli"
4^icUa*

rem these investigations, the isolation of uric acid proves
renal function of the five pouches or sacs of the stomach
he Asteridca.1[ There is no doubt that the stomach of
Kshes performs a dual function : it is an excretory
tn as well as a digestive gland, and separates the nitro-
308 products of the waste of the tissues, &c., from the
d or nutritive fluid in the form of uric acid, which is at
ain times to be found in the five pouches of that organ,
ihe Invertebrata there are numerous examples where an
m performs a dual and even a triple function.

* Proceedingi of Royal Society of Edinburyhj vol. 14, p. 230,
t See also Durham in Quart, Journ, Micros, ScUtice, 1891.

PHySIOLOGV OF THE hWERTEBRATA.

The Annelida.

(i) The Hh-udinm. — The author* has examined tic
nephridia of Hii-nda incdiciiialin. These tiephridia are in
pairs, extending from the second to the eighteenth segmenU
(somites). Each nephridiumt consists of a much -convoluted
cellular tube. The cells of the tube are perforated by smalL
ducts. The nephridia (segmental organ,s) open externally o*^'
the ventral side of the body.

In Lnmhriais the nephridinm communicates internally t^^l
a wide funnel-shaped aperture (which is ciliated) with tfc^^^*
perivisceral cavity, but in Hii-mIo it opens intemalT'^S
by a "cauliflower-headed" portion (the analogue of (^■h«
funnel-shaped aperture in Lnmhricus) into the perlnephrw^:^;;^*'
tomial sinus. Each nephridium consists of five princip^c:^'
paits—(«) posterior lobe, (i) anterior lobe, (c) apical Inh — ^^-
(d) the testis lobe, (f) the vesicle, with its dnct, which oper =^db
externally.

The nephridia of Hii-udo are covered with a pigment-;::*'tM
connective tissue. These pigments are no donbt t-i^^''*
histohfematina of Dr. C. A. MacSIunn, for he says : " I ha-*^"^^^
found that throughout the whole animal kingdom in ea.^*^''-''
tissue and organ there are present colouring matters," %

In examining the physiology of the nephridia or segment' ,*^ti"
organs of the Minidlnca, the author obtained the excretio^^^**''*
from a large number of freshly killed leeches. These exci«r=^'*"
tions were examined by the same chemical and niicroseopi^ .«3Cal
methods used in the examination of the segmental organs ^^ of
the Oligocha-ta and the renal organs of the Asleritiia.

The nephridia of Rirudo contain uric acid and sodiui^c:— *™ •
and it may be that the uric acid is in combination with sodlt^ -"'"
as sodium urate.

* Proowtiogi of Jioyal Socitty nf Bilinbvrgh, vol. 14, p. 346,
t I'rom H'pp6i. a Itidney.

J Proc, BiriHinghaBK I'hUoKoplK'd Soeitly, vgl. 5, p. an; 1
l8iS6; and I'hiloioph. Travi., iS8li,

PHYSIOLOGY OF THE INVERTEBRATA.

257

|i2) The Otigochcda. — The renal Bj-stem of Lnmhricuscarm^ts
of a large number of coiled tubes (Fig- 47) distributed in pairs,
one pair in each somite of the body. Each tube or segmental
organ (nephridium) consists of three distinct parts — {a) A
much-convoluted thin portion, terminating in a funnel-shaped
opening; (h) a tliick-walled glandular portion; (c) a thick

opening o[
ucpbiidium.

-V

. ^-tariv cord.

tFic. 4;
Hmlar portion (the outer loop), which opens externally by
aperture near the ventral side of the body. The nephri-
dium as a whole lies on the posterior side of the septum, but
the funnel-shaped aperture opens on the anterior surface ;
that 13 to say, into the cavity of the segment in front of that
in which the main body of the nephridium lies. This is the
case in every segment containing these organs. Tlie septa,
r mesenteries dividing the body into segments, are richly

^pt m

3S8

PHYSIOLOGY OF THE INVERTEBRATA.

supplied with blood-vessels, many of which are intimately con-
nected with the folds of the nephridia^ There is little doubt
that the nitrogenous waste matters are absorbed by it*
glandolar portions of these coiled tubes, and ejected by <h^
contractile parta to the exterior.

The author " has isolated nric acid from the excretion ^
the nephridia or segmental organs of £itmbricu£ tcrrrxtr^-
Tlie contents of these organs do not contain guanin, urea, *>'
calcium phosphate.

The segmental organs in the Oligochtrta are therefore rets*'
in function, eliminating the nitrogenous waste matters od*!*'
tained in the blood, in the perivisceral cavity. The iarjC"**'
amount of uric acid was found in the excretion contained. •"
the muscular part of the segmental organ (Fig, 47, om. "ter
loop of nephridium).

The following table is a summary of the constituent^^ 0>
the nephridia or segmental organs of the Annelida : —

ffir«ti««.

P.<inM^-

Urie acid . .

prewnt
absent
absent
absent
present

present
absent
absent

sbsent

,„ 1

Sodlom . .

The minute structure of the excretory organs in the Ot •"i/""
chft'fa, especially those of Zumhricm ierrestriSy have ly^^''
worked out by Dr. E. Clapar^tle, and detailed in his "Hi^***"

logische Untersuchungen iiber den Regenwurm,"t and*-*®"
by I'rof. C. Gegenbaur. }

* Froctetliniji of Roi/al SotUtij of BdiiAurgh, vol, 14, p. JJJ,
t Zaiidirifi/Ur WiiMnichaflUtAt Zoo^ogit, \oL 19.
Z lUil, vol. 4,

PHYSIOLOGY OF THE INVERTEBRATA. 259

The Nematoidea.

In a paper read before the Royal Society of Edinburgh on
July I, 1889, the author stated the results of his examina-
tion of the renal organs of the Nematoidea.

The body of the " thread- worms " is elongated, round, and
thread-like, tapering (more or less) towards the anterior and
posterior ends. The Nematoidea are not divided into segments,
and they have no segmental organs.

In the species (AnffuUUda brevispinics) selected for investi-
gation the renal organ is a glandular mass situated in front
of the gizzard. This organ has a well-developed excretory
duct, which opens externally by a tranverse slit (the vascular
pore) on the ventral side of the body.

When a section of the glandular organ of Angidllula ia
examined under the microscope, the epithelial lining is seen to
consist of nucleated cells, similar to those of the Malpighian
tubules of the Insecta (see later in this chapter).

The organ contains a clear fluid, which can be made to yield
microscopic crystals of uric acid. The author has extracted
iric acid from a large number of these organs (obtained by
iissection under the microscope) by boiling them in distilled
^ater. The filtrate, tested by the methods already described,
ielded uric acid and murexide crystals.

A fresh " glandular organ " was placed upon a microscope
iide and crushed ; then a drop of dilute acetic acid added, and
tie whole covered by a cover-glass. On examining with the
microscope it was observed that rhombic plates and other
rystalline forms had deposited. The cover-glass was slightly
seised, and on the addition of a drop of nitric acid, followed
y ammonia and gently heating over a spirit lamp, prismatic
trystals of murexide were formed.

No urea, guanin, calcium phosphate, &c., could be de-
leted in the excretion of this organ.

These reactions prove that the so-called " glandular organ *'
f the Nematoidea is physiologically a kidney.

s£o physiologv op the invertebrata.

The Prototracheata.

This order is represented by the genua Peri2)ntit.t, whic"
contains several species. These animals have the power "'
" throwing out a web of viscid filaments when handled <^^
otherwise irritated." This viscid mattt-r is secreted by t»*^ ^
large ramified tubular glands situated on the sides of tt^^
digestive tube, and open externally by the perforations of tfc;^*
oral papillie. Pi-ri/mhis breathes by means of tracLese, hen^^"*
the reason that I'rof. Huxley has referred the order to whicz^"
Fc-ipalus belongs to the Arihmpoda.

From these remarks it will be observed that respiration zi^^i"
Pci-ipatus is on the insect-type — U., by means of trEche-=^
tubes ; bnt the other excretory organs differ from those of tl^SiP
Inseda. In the Insrrta the renal organs are the Malpighi^^^Q
tnbules, but no sucli appendages to the alimentary canal a z^^
present in Peripaius.

The kidneys are segmental organs or nephridia, like tho«^sc
of the worms, but of a more highly complex type. There
a pair of these organs in each segment. They open \
temally into the body cavity, and externally at the base
the limbs.

The MvRiAroDA.

The intestines of the animals belonging to this class s
provided with Malpighian tubules which perform an e:^^
cretoiy function ; in other words, they are physiologically i.
kidneys.

The Issecta.

Before describing the excretory organs, it is perhs'
desirable that we mention certain secretions, and the oi^'
(as far as possible) which give rise to them.

((') The poison which certain insects secrete is a fli«- ■
strongly impregnated with formic acid. In many cases tt^
fluid is secreted by a special gland, and poured into a W~'
ceptacle connected with the sting (f.;/., in A^ns and F(jj«^^

TO :>^H

PHYSIOLOGY OF THE INVERTEBRATA, 261

The larva of Dicranura vinula possesses a gland which
ecretes formic acid. The duct of this gland opens in a
lorizontal slit on the red margin below the true head, and is
hus placed in such a position that its contents are ejected
Q an anterior direction. Disturbance causes the larva to
withdraw its head still further, and to inflate the red margin,
specially in the region of the gland duct, and at the same
ime the head is always turned in the direction of the dis-
urbance. Thus the fluid is thrown towards the cause of the
Titation, and the terrifying appearance of the larval fuU-
%ce is also brought to bear upon it (Poulton). The acid
jected by the larva of JD. vinula is a defensive fluid, and no
oubt is a means of protection against enemies.

This defensive fluid is ejected from a transversely placed
perture on the ventral surface of the prothorax, immediately
Blow the head. Mr. E. B. Poulton, F.R.S., Prof. R. Mel-
^la, F.R.S., and Prof. W. R. Dunstan have proved by
lemical tests that this fluid secreted by the larva of D,
Inula is formic acid. '* The smell is also quite characteristic,
nd affords an indication of the large proportion of acid
resent in the secretion. It is also an interesting fact that
le freshly-made and moist cocoon of D. vimda is powerfully
3id to test-paper."

The secretion consists of a pure aqueous solution of formic
3id, containing an average of 33 per cent, of anhydrous acid.
. mature larva will eject 0.05 gramme of the secretion, con-
lining 40 per cent, of acid. The rate of secretion is slow ;
^arvation lessens its amount and decreases the quantity of
3id; but there is no difference in the nature of the acid
hen the larva is fed on poplar instead of willow.*

" The larva appears to depend entirely upon tactile stimidi
)r the direction in which to move its terrifying full-face,
nd towards which to eject the irritant acid secretion. Visual
9iisations appear to play no part as guides in the assumption
f the defensive attitude."

* See Meport of British AstocicUion, 1887, p. 765.

a62 PHYSIOLOGY OF THE INVERTEBRATA.

The larva of Dicravura /inTulii does not eject an irritont
Becretion, but it possesses an eversible "gland'' as a defensiw
organ. A similar structare is present in the larva of D. Hmil^
but it is unable to evert its prothoracic " gland " Toloiitarily»
This structure is eversible in the larvse of Melitcta nrtewii
Ori/ifia jntdihuiidu, Orgyia avtv^ua, and Liparis aurijtua;
there is no doubt that these defensive structures are of con*
atant occurrence in Lepidopterous larva?.

The power of everting the "gland" in the larva of J5. nnW"
has been lost, due to the fact that the " larva has acfjuired the
remarkable power of ejecting the intensely irritant secretion
to ft considerable distance by forcing it through the narrow
chink, with its closely approximated lips, which constitnW
the mouth of the duct leading to the sac. Such a formidaW*'
means of defence may readily have supplemented the mt
usual method of eversiou, a method which can only give
to the discharge of vapour into the air, instead of a wi
directed stream of Quid, which, if volatile, as it is in tbi
lai-va?, of course produces abundance of vapour."

The eversible glands of the larva of Liparis avrijlua
not often completely evert.ed, out they are very senaitivR
tactile impressions, and on "stimulation a clear, transparenl
Becretion appears in the lumen, being probably raised by
partial eversiou. The secretion is not acid to litmus ]iaper^
but it possesses a peculiar and penetrating odour."

The ejection of defensive fluids and vapours are not
fined to the anterior parts of insects, for in the Bombard!
Beetles, according to Dr. Lran Dufour. a jjungent vapour,
resembling nitric acid in its properties, is ejected from the
anus. Bravhinm ditplosor will furnish twelve such discharges,
but subsequently explosion with uoiae is replaced by the
emission of a yellowish or brownish fluid, which readily
vaiwrises. These discharges aR' meant to arrest the onset of
larger predacious beetles. Bmehinwi rrqrUani is sometimes
gregarious, and when one individual is disturbed the whole

lion
■row

ren*

PHYSIOLOGY OF THE INVERTEBRATA. 263

discharge in unison, but after about twenty exploBJons they
only emit a whit« fluid.

M. F. Pouchet * aays : — " L'lnatinct de la dilfense eat telle-
ment inherent h. la triba des Uombardiers, qn'aii bcuI coup de
canon d'alanne de I'nn d'eux, tous lea autres cr(5pitent en
in^me temps : c'est iin feu roulant sur toute la ligne."

There is something in these insects discharging the fluid
in itni^m which aei/ma to point out tliat they are guided not
merely by instinct, but by that which is the equivalent of mind.
LThe chief enemy of if. erepitaiis, which inhabits Great
pitain, is Cnlusojiia inquvntirr (Fig. 48).

The secretory glands o£ the Bugs are situated exterior to
the insertion of the posterior legs, and emit fcetid effluvia on
Seizure.

The ground bettlea of the genus Carabus, when disturbed,
^j(^t a fluid which is caustic if applied to the skin.

In conclusion, it may be remarked that a very large
dnmber of insecta eject liquids or vapours as a means of
■ L'Unireri,-p. 137.

PHYSIOLOGY OF THE INVERTEBRATA.

or less, from the attacb o^

264

protecting themsi^lves, 1

various enemies.*

{h) There are two pairs of salivary glands of the kn&l
Lcpidoptcrn (see Fig. 7). The posterior or second pair kzk^
the viscous substance, which hardens on exposure lo ti*
atmosphere and forms silk. This ailk is the material in
which the larvce or caterpillars invest themselves. Tlie ris-
C0U3 substance from these glands is made into threads anJ
spun into cocoons by means of a slender tubular organ chIIm
a spinneret, which is situated on the labium.

Most caterpillars spin silken threads to secure themaelTa
from falling, and many of them, as already stated, spio >■
cocoon in which to pass the pupal state.

In Mj/rnucoles and the Honcrohiila: the silk is fumiahrfl
by the rectum.

(f) The glow-worm, or Lamjn/ris .tplauHihUa, and 1
other insects have the power of emitting light.
to Schulze.t the males of the glow-worm have a pairfl
photogenic organs, " which lie on the eternal aspects of •*
penultimate and ante-penultimate abdominal somites.
is a thin, whitish plate, one face of which is in contact *
the transparent chitinous cuticula, while the other is in
tion with the abdominal nerve-cord and the viscera.
sternal gives out much more light than the tergal face,
photogenic plate is distinguishable into two layers, (
occupying its sternal and the other its tergal half,
former is yellowish and transparent, the latter white l
opaque, in consequence of the multitude of strongly refra^'
ing granules which it contains. Trachea; and nerves entw
the tergal layer, aiid for the most part traverse it *"
terminate in the sternal layer, which alone is luminon»-

* For lurther intormation oa tho defensive flaiiis and Iha eTeft'l*
glands oC Lepidopterous larve, see the papers by Ur. E. B. PoDlton, FJi'^^ _
In the Tratuatiion* of Jintomologieat Hotiely oj' Lmulon, 1SS5, J
1886, p. 156; ibid., 1887, p. 395; Jle/iort of Sriliih Amociution, iSSJ.f. 7*
~. -- . lofAttimaU.

sod his excellent book, Tlie Colour
t ArchicfUr Jfilro«to(ii»c7ie Ana

', "855.

PHYSIOLOGY OF THE INVERTEBRATA. 265

Each layer is composed of polygonal nucleated cells. The
granules are doubly refractive, contain uric acid, and
probably consist of urate of ammonia. Hence the cells of
the layer which contain them are termed by Schulze the
^ urate cells/ while he calls the others the 'parenchyma
cells.' The branches of the tracheae which ramify among
the parenchyma cells end, like those of other parts of the
body, in stellate nucleated corpuscles, one process of the
corpuscle passing into a ramification of the trachea. Schulze
is inclined to think that the other processes end in paren-
chyma cells. The nerves of the photogenic plates are derived
from the last abdominal ganglion ; they branch out between
the parenchyma cells into finer and finer branches, which
eventually escape observation." (Huxley.)

Lanripyris can vary at will the intensity of the phosphoric
light. It has been stated that the light is connected with
the action of oxygen upon a fatty material secreted by the
photogenic organs, and the light so produced is reflected by
means of the granules already alluded to.

The function of the Malpighian tubules of insects were not
Sefinitely established until a few years ago. Some zoologists
itated that they represented the '* liver,' while others main-
tained that they were renal in function.

The Malpighian tubules of Blatta (Fei^iplancta) have been
shown by the author* to contain uric acid and urea.

Dr. C. A. MacMunnf has confirmed the author's investiga-
tions, for he has extracted uric acid from the Malpighian
jubnles of Periplaiieta orientalis. These tubules were crushed,
boiled with distilled water, the extract evaporated to dryness,
svashed with hot alcohol, and again dissolved in boiling water
^nd filtered. To the filtrate excess of acetic acid was added,
and in some hours uric acid crystals of various forms, and
giving the murexide test, were formed.

* Chemical News, vol. 52, p. 195.

t Journal of Fhysiolojy, vol. 7, p. 128.

266 PHYSIOLOGY OF THE INVERTEBRATA.

The author" has also examioed the Malplghian tnbnlMof
Libiihda deprcssa (Figs. 49 and 50), and has proved that tier
have a renal function.

Lihdlvla depressa (the dragon-fly) ia a voracious insect, wb
lives in water, during its earlier stages, where it undergoe^^ '
imperfect raetamorph*^^^
the pupa finally creep ^^^b
out of the water, and cba^^'*
ing into the imago. By -■'**^*
periinenting with a la::^^^^
number of the larval foi""""™
..r LiMhila. the author *^=^

■xtracted (from the Ii

uric acid crystals, by nscr^-^^
similar methods to th -^*^
already described in t:::^^
chapter.

In the im^o or mats
form of the dragon-fly
Malpighian tubules number from sixty to seventy, and
branched. Under the microscope, a Malpighian tnbal^
' Proc. Boy. Soc. Eilinb., vol, I5,p.40i.

tbe

PHYSIOLOGY OF THE INVERTEBRATA. 267

ten to consist of a cx)nnectiye tissue layer, a delicate
tracheal tube," a basement membrane, and an epithelial
yer of comparatively large nucleated cells (Fig. 50). The
itemal cavity of one of these tubules is very irregular, as is
)en by examining various parts of it in a transverse
action.

The uric acid contained in these tubules can be extracted
jT boiling a large number of them in water, filtering, aud
len evaporating the filtrate to dryness. The residue is
'eated with alcohol, filtered, aod the residuQ so formed is
isaolved in boiling water to which acetic acid is added,
iter standing for several hours, crystals of uric acid
DjH^N^O,) are deposited. These crystals are readily con-
erted into murexide.

Then, again, if a fresh Malpighian tubule is placed upon a
ide under the microscope, and crushed, a drop of dilute
36tic acid added, and the whole covered by a cover-glass,
lombic and other crystalline forms are deposited. These
rystals are also readily converted into murexide by the
:tion of nitric acid and ammonia.

No other substance besides uric acid could be detected in
le Malpighian tubules of Libdlxda dcpressa.

From the above-mentioned reactions it is evident that the
lalpighian tubules of the Insecta are physiologically true
inal organs.

As already mentioned some zoologists of the older school
ated that these appendages of the alimentary canal repre-
Qted the " liver," and this statement has been recently
vived by Dr. B. T. Lowne in his work on Calliphora, But
e Malpighian tubules of the Diptera (including CallipJwra)
adily yield uric acid when the proper tests are skilfully
^plied ; and they do not contain the least trace of biliary
ids, glycogen, or even ferments.

The Malpighian tubules of the Insecta are undoubtedly true
dneys, although they are developed from the alimentary
nal.

PHYSIOLOGY or THE INVERTEBRATA.

The Aiuf'HKiRA.

(rt) In the Scorpion tlie posterior extremity of the abduroeu
ia armed with a sort of hooked claw, which, when tJie animal
is in motion, is always carried over the back in a most
threatening attitude. This claw-like organ is the sting, »iid
at its base are situated two poison-glauda whose duets pass
into the point of the sting, so that when tlie animal strikts
with its weapon, a small portion of the poison or veinon w
instilled into the wound. The sting ia a weapon of offenM.

(?') In the Araiu-iim the poison gland ia lodged in the
cephalo-thoras, and the duct of it opens at the summit of
the terminal joint. It will be noticed that in the Aruw'H"
the poison gland is situated in the anterior part of tl'*
body, whereas in the Arihmriaitira it is in the postenor
part.

But " the moat characteriatic organ of the Arannna is ui6
arachnidium, or apparatus by which the fine silky threwi
which constitute the web, are produced,"

In Epcira dimkma this apparatus contains a thousan*^'
glands with separate ducts. These ducts secrete the vifc*"
material which ultimately hardens into silk. "The glan**®
are divisible into five different kinds (aciniform, ampulla^*'
aggregate, tubuliform, and tuberous), and their duels nit*"
mately enter the six prominent arachnidial mammillai, wlu*^
in this species project from the hinder end of the abdoffl*"'
The superior and inferior maramillEe are three-jointed; t**^
middle one ia two-joiuted. Their terminal faces are tm**'
cated, forming an area beset with the minute arachnid**
papillae by which the secretion of the glands is poor*^
ont."

The Spider usually commences its thread by applying t***
spinnerets to some fixed object ; to this the viscoofl eecreO*'*'
attaches itself, when the movements of the animal '^
sufficient to draw out the materials necessary for the wi*'

PHYSIOLOGY OF THE INVERTEBRATA.

269

lation of the thread. This power of BpitmiDg threads
ai the secretion of these glands is of the greatest import-
e to all these animals (i.e., those belonging to the
entai7 class), as it not only serves many of them for the

stroction of dwellings, and of webs for the capture of
f, bat is constantly employed in securing them from falls
1st in motion, or in descending in a direct line from an
-ated position to some object below them. Many spiders

370 PHYSIOLOGY OF THE INVERTEBRATA.

have tlie power of emitting this secretion in the form q!
' threads, one end of which floats freely in the air tintjl it
meets with some object to which it adheres. By this menni
spiders often form natural bridges, by means of which they
can pass over brooks and rivers, in some cases twenty und
even fifty feet wide.

Another purpose to which this secretion is applied bj «1)
spiders is the formation of silken cocoons for the reception
of the ova, which a few species (i.f., wandering spideis) oury
about with them.

-"■+.=

Q/0'

'l-zX

Km. 5J, a AND *.— Crvstals ui- Umc Acid and Murexidk.
a = the uric add crystals, t = murexide ciyslals.

Concerning the excretory apparatus in the Arartriiui,
A. Johnstone, F.G.S., and the author" have examined
Malpighian tubules of Tajcnai-ia domtstiea fFig. 5 1, A an*-.-
The intestines of this s|)ecies form a tube-like body, w!
dilates into a short rectum, and into this recttuii the I
pighian tubules open.

An aqueous extract of a large number of these tat
yielded uric acid (Fig. 52). The secretion is neutral to
papers.

• Proe. lio'j. Soe. EdUb., vol. 15, p. ill.

lel

the
Iiick

((•St

PHYSIOLOGY OF THE INVERTEBRATA. 271

The uric acid was extracted by both of the methods used
for testing the pyloric sacs of Uraster (see p.) 254.

The uric acid is present as sodium urate, for sodium is
easily detected in the secretions of these organs. No doubt
some sodium compound is a normal constituent of the blood
of Tegenaria.

No urea, guanin, or calcium phosphate could be de-
tected in the secretion. But it may be stated that
Dr. C. Weinland* has recently extracted crystals of gnanin
from the excrements of certain spiders. The guanin so
extracted is stated to have answered to all the reactions of
that substance as described by Capranica.t

There is no doubt that the Malpighian tubules of the
Arachnida are renal in function.

The Crustacea.

Among the lower Cncstacea the renal organ is represented
by the so-called shell-gland. It consists of a coiled tube
^nth clear contents. In Apus (belonging to the Phyllopoda)
this gland opens by a duct '* on the base of the first pair
3f thoracic appendages, immediately behind the second
naxilka"

In his paper on Cyclestheria hislopiX ^^' ^* 0. Sars says
tat the only organ to which an excretoiy function has been
attributed is the so-called shell-gland (see Fig. 11). Its
tmcture is glandular, but of what nature the secretion is,
.nd in what manner performed in this species, has not yet
fteen satisfactorily ascertained. Some naturalists state that
Ids peculiar organ secretes the material of which the shell is
feuilt up, but it is far from evident that such is its real
miction. On examining the organ, Dr. Sars failed to detect
la. this species any secreting orifice, the whole organ appear-
oig to constitute a convoluted canal or duct recurring in itself.

♦ ZeUschrififUr Bidlogie, vol. 25, p. 390.

t Zeitachrift fUr PhysiologiacJie Chemie^ vol. 4, p. 233.

X Chriatiania VtdensktUfs-Selskabs Forhandlinger^ 1887, P 43*

e whitens
t of t«(^H

272 PHYSIOLOGY OF THE INVERTEBRATA.

Bat there is no doubt that in other forma of the
orders of the Crustacea the secretion of the shell-gland does
contain nric acid, proving the renal fnnction of the oi^n in
question.

In the Decapod Cmslact-a • the excretory organs are re-
presented by the so-called green glands. Dr. Rawitz has
recently examined the anatomical structure of these glands
in AstncKs/liieiaii/is, and bis results may be summarised as
follows : — The gland is uniformly green on the ventral side,
but on tlie dorsal side only at the periphery ; elsewhere white
with a round yellow-brown speck in the centre.
examined microscopically the gland is seen to consist of t
tubules closely interwoven. The cells of the gr^eo part ■
contain a round grass-green drop of protoplasm, and the •
yellow-brown cells a unifonuly ""
yellow-brown coloured nac1eu». —
The tubules anastomose, the*^
yellow -brown cells being the-^
terminal portions of tubule^^
and secretory.t

The author t has made a com

plete study of the function ©•:
the green glands of Astnfit^^
fiitruitilis, and the results ot-^
these resi?arches may be stated as follows: — The BO-calle<S»
green glands of the fresh-water crayfish lie in the cavity o^
tho head below the front part of the cardiac division of th^
stomach (see Fig. 13), The openings of these organs iw
situated at the base of each antenna. The organ, carefur_
dissected out of the head of a fresh-killed crayfish, is seen t —
consist of two principal parts (Fig. S3)- a dorsal or uppec^

• The Dfcoptxla includes tbo Brnchi/iira and the J/nrr.

t See Dr. Hawlti'e paper, read berore Ihe Berlin Plijsiological Society i|
January a8, 1887.

; Dr. Griffiths' paper iu Proeeedinffi 0/ Rogal SocUtu of Lo»do», vi^ J
(i8Ss),p. 187.

Frc. 53.

GStEN Gl.AND Of ASTrtCL'5.

e = glanduiar ponion. i = s
like ponion. c = opening of

cations, x a (about).

274 PHYSIOLOGY OF THE INVERTEBRATA. ^H

most one which is a transparent and delicate sac-like body ^^
filled with a clear fluid, and a ventral or au underlying
portion of a gmen colour, glandularin appearance, containing —
granular cella.

As is well known, these green glands were formerly -r
believed to be the auditory orf^ans of Astaats; but in 1848 ^S
Drs. Will and Gorup-Besanez * stated that this org&n pmbafjli/ "v/
contained guanin, and from this supposition the green glands «^ 9
have been considered as excretory organs.

The secretion of these glands is acid to litmus paper, and JEW
on treating the secretions, obtained from a large number of^^of
green glands, with hot dilute sodium hydroxide solution, audC=»jd
then adding hydrochloric acid, a slight Saky precipitate r-nrT a^n
obtained, and on examining these flakes under the micro3cop^»«:^
they were seen to consist of small crystals in rhombic plates ^^;ss.
On treating the secretion with alcohol these rhombic rryntalr f^^'
(Fig. 54 A) were deposited; they were soluble in boilin^.K3Dg
water.

When these crystals were moistened with dilute nitri'-i~*nt
acid, alloxan thine (C^H.N^O;) was produced, and on heating -■=*''£
this substance with ammonia, reddish -purple murexid .E» jd*
(Fig, 54 B) or the " ammoninm purpnrate " [C,H,(N'HjSjO„.^I^(U
of Prout was obtained. The murexide so obtained 1 ij iliilli 11 1 ■ iii'i'
in prisms, which by reflected light exhibit a splendid gree^^^^*"
metallic lustre, and by transmitted light are a deep reddiskJ^^'
purple. On running in a solution of potassium hydroxiE» -i"^^
upon a microscopic slide containing some of the m«rexicE»ii<'8
crystals they were dissolved.

It is evident (from the above reactions) that these rhomh*:.^' ''"'
crystals are deposits of uric acid (CjHiNjOj) from the secretic»-i ioo
of the green gland of the crayfish. Tiiese deposits of uc^ 'nc
acid crj'stals were covered more or less with a very thin tx-.^nd
superficial coating of some brown colouring matter, probat^PT)//
one of the pigments already described.

* See Munduii Gtlekrle Aiatigen, No. 233, t848>

PHYSIOLOGY OF THE INVERTEBRATA. 275

The secretion of the green gland otAstactis contains gaanin,
which is proved by treating the secretion with boiling hydro-
chloric acid. A solution is obtained containing flakes of uric
acid in suspension, these are filtered off, and the filtrate set
aside to cool, when a few crystals (guanin hydrochlorate)
separate which are soluble in hot water. On the addition of
ammonia to this hot aqueous solution a precipitate is obtained
of guanin (C^H^NjO), the precipitated guanin being composed
of a number of minute microscopic crystals. On running in
warm dilute nitric acid (on to the slide), these crystals dis-
appeared, but they where precipitated again on the addition
of a drop of silver nitrate in the form of the nitrate of silver
compound (C4H4N5O, AgNOj) of guanin.

This investigation proves that the so-called green gland
of Astacvs fiuvicUUis is a true urinary organ, its secretion
contuning uric acid and traces of the base guanin. The
green gland is, therefore, physiologically the kidney of the
animal.*

The nerve, which comes off from the supra-cesophageal gan-
glion, passes to the neck of this gland (see Figs. 13 and 53),
and ramifies over its surface between the outer and inner
xaembranes of which it is composed.

In the Edriophthalmic Cntstacea, there are occasionally
present one or two tubules which open into the posterior
part of the alimentary canal. These are renal organs and
contain uriq acid. They are analogous to the Malpighian
-tubules of the Insecta. In this respect the Amphipoda and
Jsopoda differ from other Crmtacca.

The Brachiopoda.

The shell of these animals is " a cuticular structure secreted
l>y the ectoderm, and consists of a membranous basis, hardened

• For further details see Dr. Griffiths* papers in Proceedingt of Royal
Society t vol. 38, p. 187 ; Cliemical Xews^ vol. 51, p. 121 ; Journal of Chemical
JSocieiy, 1885, p. 680 ; Science Oossip, 1886, p. 57.

276

PHYSIOLOGY OF THE INVERTEBRATA.

by the deposit of calcareous salts, sometimes contamisg t
large proiwrtion of phosphate of lime {Lhiffiila)."

In Ji'a/t/htimia and other Brachiopods, "the periviscera
cavity communicates with the pallial chamber by at least two^ - -^
and sometimes four, tubular organs, tvhich have been deacribett-. ' ^
as hearts, but are now known to have no such nature,"

These organs are funnel-shaped, the wide parts of "birl * i
open into the perivisceral cavity. The narrower parts of thes^^— ^^
organs pass through the anterior wall of tJie visceral chambei— ^^=^~,
and terminate in small openings in the pallial cavity.

According to Dr. Morse, the ova pass through these oi^an - -ss

in Tcrebratulina seplmh-ionali^. The so-called p
have a double function, being renal organs and genital dact^
They are the homologues of the organs of Bojanus of th.
Molhisca, nnd of the segmental organs of worms.

The Mollusca.

The excretion of carbonate of lime is an important fnnctJo^
in a large number of Mollnsca.

In Anodonta, which is taken as a tj-pical example of th**
Lainellibramlnata, the shell is a " cuticular excretion from
the surface of the mantle," and consists of variously disposed
lamellse of organic matter impregnated and hardened by the
deposition of calcareous salts (chiefly carbonate of lime,
mineralised as arragonit*). The shell has no cellular Btnuv
tnre; "but from the disposition of its lamellae, and from the
manner in which the calcareous deposit takes place in them,
it may present varieties of structure which have been distin-
guished as nacreus, prismatic, and epidermic " (Fig. 55).

In the young Lamellibranch shell there is a mnch lat^r
percentage of calcium phosphate present than in the adnlt
shell: the calcium phosphate being gradually replaced by
calcium carbonate as the animal arrives at maturity.

The ligament which unites the valves together is an nncal-
ci£ed chitinous material. This material is continnous with

PHYSIOLOGY OF THE INVERTEBRATA. 2?7

'the lumiy cuticle wUcli BpreadB over the external earface of
"fthe Talres, and ib reflected over the ventral edges into the
xnamtle or palliiun.

Qlte pearly or nacreiiB layer has a laminated textnre, and
:m8 aeoreted by the mantle. The prodnction of pearls (e.^., in
.JideagrvMi margariiifera, the
"^' pearl oyster ") is as follows :
_A. grain of sand, or other hard
substance, gets in between the
'pallium and the shell. Con-
sequently the external surface
of the palliom becomes irri-
~tAted, and the laminated mo-
-theiHjE-pearl layer (nacreus j,.,^.

layer) is secreted ly the pal- Section of Shell of Gapbr.
liam, during the remainder of a = cwicula. i = prismaiic layer.
tie animal's life, aronnd this ' = ""creus layer, d = epiibeUum.
_ . , , , - e = mande.

3mtant nncleua.

The ezoskeletons of the Braehy^ara and Macroura have a
similar stractare to the Lamellibranch shells ;t and it has
~fceen shown that the particular combinations of lime requisite
:Xor tlie formation of these shells, &c., are calcinm chloride,
«»lciam carbonate, or calcinm phosphate. The sulphate of
lime present in sea water cannot be utilised for shell formation
^nnleas it is first converted into one of the above forms. The
a«seaiches of Irvine and Woodhead> prove that " shell formfr-
~ftion in the crab is somewhat different from egg-shell formation
:an Che hen, and occupies an intermediate position between

• According to Dr. Q. Hurley, F.R.S. {Proc. lioi/. Soc., iSSE) peada bav«
'Uw^foUowing cotnpositioii : —

Calcinm carbonate 91.72

Orgknio matter (animal) .... 5.94

Water 2.33

99-fS9
t See Tition'e paper In AreAtv lit Biologie, lome 10, p. 659.
i Amv ^oy- ^^ Edin., vol. 15, p. 308 ; voL 16, p. 334.

378 PHYSIOLOGY OF THE JNl'ERTEBRATA.

sucli egg-shell formation and bone formatioD, as the carbonate
of lime is deposited in the chltinoas portion of growings
epithelial cells in the crab aliell."

" In the secreting layer of the mantle of certain Mollnsc^
the lime in the epithelial cells ia principally phosphatei^
whilst the fluid bathing its outer surface and the shells them— _
selves contain the lime, principally in the form of a carbonat^^
If there is a definite interval between the secreting aarfac~-
and the area of deposition, or if much chitin or other tissiu^
ia developed between the actively secreting cells and tl^^
tissue in which the lime is deposited, there is always a great^^
tendency to the formation and deposition of carbonate ^^
lime."

Phosphates of the alkalies and alkaline earths occar in tfc —
blood or nutritive fluid, and the latter acts as a carrier -^
lime, &c,, to every part of the body where carbonic anhydri^^::
may be given off; thus carbonate of lime is formed, and tTK
phosphoric acid re-enters the circulation.

As already stated, the embryonic aod young shells of t-"^
/.amellilnuTtchiiita are richer in phosphate of lime than fc-^
shells of the fully-grown animaL No doubt as greai
activity goes on a larger amount of carbonic anhydridt
produced, and by this means more carbonate of lime is
posited than phosphate of lime.

When alkaline phosphates, associated with lime and album 3
preponderate in the blood, the lime so separated is in f •
form of phosphate, as in bone formation ; when these ^
partially replaced by an excess of alkaline carbonates, as
the majority of marine animals, the lime is secreted as (?,^
bonate.

The corals have a secreting layer of cells which, accordi
to Irvine and Woodhead, produce chitin— chitin infiltro.'*
with calcium carbonate, and almost pure calcium carbon^*
with a small quantity of cementing oi^anic material.

The carbonate of lime is formed by the ammonium «^^
bonate produced by the decomposition of the effete prod«^ *

PHYSIOLOGY OF THE INVERTEBRATA. 279

of animals, as urea, &c., decomposing the calcium sulphate
dn the sea water with the formation of calcium carbonate.

In the blood of the lime-secreting Invertebrates there are
3>ho6phates of lime and soda, along with alkaline chlorides,
<;arbonates, and sulphates associated with albuminous matter,
carbonic anhydride and oxygen being also present in varying
<jiiantities. This blood is alkaline, which is due to the pre-
sence of alkaline phosphates and carbonates.

Dr. Schmidt found that the blood of Anodonta cygnea was
slightly alkaline; and on evaporation it yielded crystals of
calciam carbonate resembling gaylussite. '^ These could not
have been present originally in the alkaline fluid, and it is
probable that they were produced by the formation of ammo-
nium carbonate from the decomposition of urea* and nitro-
^genons organic matter."

The membrane which secretes chitin also brings lime to
the surface, and in performing its protoplasmic function car-
bonic anhydride is set free ; this readily forms calcium car-
bonate after decomposing certain lime salts. ^' But it must
be noted that the chitin is directly in contact with the upper
secreting cells, in fact, the younger layers of chitin still form
the upper or older portion of the cell." Irvine and Wood-
head " maintain that the direct contact allows of the dialysis
into the chitin of a portion of the phosphate of lime before it
is completely transformed into the carbonate. As the car-
bonate of lime is formed the free phosphoric acid is apparently
reabsorbed and utilised afresh. In proof of this fact, and as
bearing on the whole question of lime secretion, we refer to
the investigations of Schmidt, who, in speakiug of Unio,
Anodonta, and Helix, describes the structure of the secreting
membrane of the mantle as a layer of hexagonal cells on which
is a structureless transparent membrane in which the lime is
deposited, and ascribes to it the function of decomposing the
blood, of secreting a compound of albumin with phosphate of

* Urea and nrio acid are present in the excreta of Anodonta , see the
author's paper in the Chemical News, vol. 51, p. 241.

aSo PHYSIOLOGY OF THE INVERTEBRATA.

lime next the shell, wLich is decomposable even by the carbonB
anhydride of the air or of the water, bat of retaining the
phosphoric acid and returning it to the organs which requa*
it for the process of cell formation. In proof of this he gi**
the following analysis of the ash of the secreting layer of ***
mantle :

1. I II.

Calciam pbospbaU i4'85 U"?)

Calciom carbonate, sodium phosphate,) 1 ,

sodium chloride.Biid calcinm gulpb&t«| i

showing how large a proportion of the lime salts mtist>»'^
this secreting layer, be in the fonn of phosphates. "*
farther proof he gives analyds of the mucas which is fofc*"^
betwi-en the shell and the mantle, in which he finds m**'^
albuminate (basic) of lime, a small proportion of carbc^***
anhydride, but not a trace of phosphate. In the delie**
membrane in which the lime is deposited we have an anwJ-
gous membrane to that of egg-shell membrane (of birti^'"
separated from the secreting layer of cells by a fluid contain£ ^^-^^
albumin, carbonic anhydride, and lime salts, in whatever w^ ^^J
combined, and deposited in the structureless niemhra*^^^
According to analysis of the ash, the lime salts present ^■- ^^^
in the following proportion : J

Calciam c&rbouate
Cslcinm phosphate

0.55

99-'*
0.94

So that Schmidt was able to trace the transition sta^"
through the excess of phosphate in the mantle, the alb ^
minate in the intermediate bathing mucus, and the carbontU'
in the Bhell."

Irvine and Woodhead believe that the carbonic anhydri^
in this t^ase was tlie result of metabolic processes going c:^
in the mantle, and tiiat the carbonate of lime formed w -
gradually passed on in this condition from the lime-mac&
solution (if present in that condition) into the meml
again by dialysis.

PHYSIOLOGY OF THE INVERTEBRATA, 281

'' As the process of shell-formation muBt necessarily go on
lowly, it is not at alLastonishing that such a small propor-
i.on oi carbonic anhydride should be found in the mucous
doterial. It is used up as it is formed in laying down the
arbonate of lime of the shell.

'^ As regards the proportion of the lime salts and chitin,
Ichmidt found that the amount of earthy phosphate increases
:a proportion to the quantity of chitinous tissue present in
be basement structure :

CMUn .
Lime salts

Crayfish. Sqailla.
46.73 ... 62.84

53.27 ... 37.17

Lobster.
22.94
77.06

100.00

Calcimn phosphate
Calciom carbonate

13.17
86.83

47.52

52.48

12.06
87.94

100.00

" He argued from this that the calcium (lime) phosphate
^ in intimate relation with cell-formation." But Irvine
:xid Woodhead think that as the chitin becomes older and
Kiieker the cellular layer becomes less active, less carbonate
^ formed, and that there is thus a more direct passage out-
b^ards of the phosphate. In their papers already mentioned,
onmie and Woodhead give the following analyses as showing
lie comparative amount of calcareous and organic matter in
lie common edible crab :

Water, blood, salts, &g. 6,646 grains

Flesh (gave 14. 56 of ash containing 4. 94 lime phosphate) • 295 „

Cater calcareoos structure 2,956 „

Inner calcareoas structore 103 „

10,000 „

E?he calcareous structure consisted of :

283 PHYSIOLOGY OF THE TNVERTEStt'ATA.

Tot.,.

Oil Ho.

LItM

ph."". 1 "^

1 ^
1 **

1 *"
1''

Carapace .

Oheto . .
AmbulaioTj* limbH
Abctominnl ,

817
1184
736

\ 63

150.32
236,80
147. ZO
31.20

:2.6o

656.80
933.00
579-97
122.93
49.64

9.87
14. 30
8.83
1,87
0.76

OUTKB.

Chitia . MM
CaCO, . Tl(&

Outer strno-l,
tore weight! '

2956

S8Ma

3342.34

35-53

Inner a true-)
tnre weight \ '

103

35«J

66.98

,.0=

Chitin . 34.00
CaCO, . 65J»

(Teeth {mandibles) weighed . 17 grains.

-1 titomachical teeth (honif mat-

1 ter) weighed . . . il „

Ca.P.O. ._LM

lOttOO

The nutritive fluid (blood) of an edible crab WM^iin^
about 8000 grains contained : —

Cttluinm phosphate iMOgralns

Phosphoric acid 15.7S „

Having alluded to the secretion of the sheila and «o--^|^
skeletons in tlie Mollmca and Crustacta, we now proceed ^^^^
describe the organ of Bojanus in AnodmUa cy<pua and other "^^
LavidUhram-JiiaUi. The function of this organ has been ^^*
investigated by Mr. Harold Follows, F.C.S., and the author.* ^
It is a paired, elongated, oval, glandular eac with folded walls. '^^
It is situated beneath and behind the pericardium, and in ■'^
front of the postenor adductor muscle (see Fig. iS). This ^^^
organ is composed of a yellowish or brownish spongy tissue, «
which is covered with a closely ciliated cellular layer. Its ^~
secretion is acid to litmus paper, and it contains uric acid, *■ *^
urea, and calcium phosphate. The presence of these com- "^"^
pounds were proved by the methods already described in X*"
this chapter.

• Chtmicat Nivit,Yo\. si,p.3i\; Jmimalcf ChemiealSoeitty,t8&i,'p.ail ■" "*'

PHYSIOLOGY OF THE INVERTEBRATA. 283

Mr. Fcdlows and the author also examined the blood (of
Anodonid) contained in the vena cava before it enters the
organ of Bojanns, and it was proved that the blood contains
me acid and urea. After leaving the vena cava the blood
passes into the organ of Bojanus and thence to the branchiad.
The blood in the branchiao does not contain uric acid or
nrea.

The investigation proves — (a) that the organ of Bojanus
is physiologically the kidney of the animal, eliminating the
nitrogenous waste matters (in the form of uric acid and
nrea) contained in the impure blood as it is brought to this
organ by the vena cava ; (b) that after the blood has passed
through the organ of Bojanus, it is freed from urea and uric
acid.

The secretion of the organ of Bojanus in Mya arenaria
[see Fig. 18) contains uric acid, urea, and calcium phosphate.

I>r8, Will and Gorup-Besanez* stated that they found
jaanin in the organ of Bojanus of the fresh-water mussel,
Dut subsequently Yoit could not detect the least trace of this
^ase in the organ in question. Mr. Follows and the author
dntirely agree with the conclusions of Yoit, for we also could
dot detect guanin in the organ of Bojanus in Aiwdonta
n/gneay although it may be remarked that guanin is present
ji the green glands of Astacus and HmnariLS,^

The organ of Bojanus appears to be well-developed in the
majority of the Zamellibranchiata, but in Ostrea and Teredo
Lt seems to be present in only a very rudimentary form 4

The nephridia of Hdix aapersa and Lwmx fiamis contain
aric acid, and were proved by MacMunn § to have a renal
Exinction.

* Ann, der Chtm, und Pharm., vol. 59, p. 117; and 3IUnehen Gelehrte
^nz^.igen, 1848.

t See Dr. Griffiths* papers in Proc. lio\j. Soc, of London, vol. 38, p. 187 ;
^nd Proc Roy, >Stoc. of Edinburgh, vol. 14, p. 233.

X See the papers of Lacaze-Dathiers in Annates des Sciences NatureUe^,
K854-1861.

5 Journal of Physiology, vol. 7, p. 128.

284

PHYSIOLOGY OF THE INVERTEBRATA.

The anthor has confirmed MacMunn's investigations, &nd
he has also proved the renal function of the nephri^ft in
LimcKc miui-imris, JTelij- ■pomatia, Limax varUgatiig, Am*
ater, and other Gasteropods. They contain, in addition to
uric acid, urea and calcium phosphate. Many of these
organs also contain some of the histohsematins ; and in the
case of ^^ Ariirn ater the nephridium showed a spectram
resembling that of myohEematin, and this spectrum a
remarkable for its resemblance to that of the kidney of
Vertebrates." (MacMuun.)

The Gasteropoda are provided with numerous glands wbidi
secrete mucns. The epiphragm of Sclit is secreted by
mucous glands, but it tecomes hardened and streBgthfflied
by the deposition of calcareous matters. This epiphragm
(perforated) is secreted before hybernation (i.e., the wintef
sleep), and closes the shell-opening when the animal i
retracted. The epiphragm is cast off iu the spring when ti
animal awakes.

The secretion of the raucous glands of slugs is of value W
the animals as a means of protection against the attacks of
enemies. The mucus secreted is oftien pigmented, and it
gives a polished appearance to the pigments which rea
certain metallic hues ; such pigment^s are spoken of as p
live colours.

Having referred to certain secretions of the Puiiiwgmtero-^'
poda, we have now to consider those of the BrnnchiogasUropoda.

The author* has investigated the nephridia of PattUai^
rtihjtUa. These organs consist of two parts — left, and right-*
lobes. The left nephridiam is very small in comparison to '
the right. The anatomy and histology of these organs faavo^
been fully described by Professor E. Hay Lankester, FAS^f^
J. T. Cunningham,^ and Har\-ey Gibson.^

* l\ontiliiigt of Royal Sotirlg, vol. 41, pL 392.

t Atnalt aitd MagaiiiK 0/ Xatural HiHory. vols. 30(1867), and 7 (18

; (^arlirif/ JtmrHal 0/ 31icro*o>piettl Sdmft, vol ai, p. 369.

i r>'uiu<Kt>uiH u/ Aoyu; i&ricfj ../ Edinbitryh, voL 31, p. 6I7.

finter ]
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aspFot^H

PHYSIOLOGY OF THE INVERTEBRATA. 285

After diasecting the nephridia from the bodies of a large
namber of fresh limpets, the secretions of the left nephridia
were examined separately from those of the right nephridia.

Both secretions were examined chemically by two separate
methods as follows :

(a) The dear liquid from the nephridia was treated with a
hot dilute solution of sodium hydroxide. On the addition of
HGl a slight flaky precipitate was obtained after standing
for some time. These flakes when examined microscopically
were seen to consist of small rhombic plates and other
forms. On treating the secretion alone with alcohol,
rhombic crystals were deposited, which were soluble in
water. When these crystals were treated with nitric acid
and then gently heated with ammonia, reddish-purple
murexide was obtained.

(&) The second method for testing the secretion of the

sephridia of Patella was as follows : The secretion was boiled

in distilled water, and then evaporated carefully to dryness.

The residue so obtained was treated with absolute alcohol

and filtered. Boiling water was poured upon the residue,

ted to the aqueous filtrate an excess of pure acetic acid was

added. After standing about seven hours, crystals of uric

^cid (CjH^N^O^ were deposited, and readily recognised by

the chemioo-microscopical tests mentioned above.

The secretions of both the lefk and right nephridia yield
itoc add. It has been suggested by Professor R. J. Harvey
oribson (in his masterly memoir on the *' Anatomy and Phy-
liology of Patella vulgata"*) that the secretions of the two
nephridia may be chemically distinct. The author could not
^:xtract or detect (after a most searching investigation) the
presence of any other substance besides uric acid in the
secretion of either nephridium. The isolation of uric acid
Proves the renal function of the nephridia of Patella v^U-

The nephridia of the Cephalopoda have also been examined

♦ TramadionB of Royal Society of Edinburgh^ vol. 32, p. 601.

286

PHYSIOLOGY OF THE INVERTEBRATA.

by the author.* Taking Sf/iiir offinndtvi as a type of llif
Cepiudopodu, it was proved that the nephridia of the aniniiil
are true renal organs. The venoos blood, as it passes from
the vena cava, is distriboted by a number of afferent
branchial vessels which communictite with the aaccnlated
and glandular nephridia; it then passeg into the branchifc,
and hence it is sent back to the heart.

The secretion of the nephridia contains uric acid aud
calcinm phosphate, but urea, guauin, calcinm carbonate, and
magnesium carbonate are absent.

Uric acid is also present in the blood of the vena' csvi
before it enters the nephridia, but the blood after passing
into the branchiaj contains no uric acid.

The nephridia of the Cephtilapoda are true renal orgsnt^.
eliminating the nitrogenous wastt matters in the form of
nric acid, contained in the impure blood as it is bronght lo
these organs by the vena cava.

As already stated no urea could be detected in the nephridii
of Sepia, and the same remark applies to those of Ortnpiit-
The muscular tissues of these animals do not yield urea; but
it may be remarked that the muscnlar tissues of certaf
Lamellibrancha do contain this base. For instance, \CO
grammes each of the adductor muscles and foot of #/**
urenona (Urge individuals) were chopped into small tm^
ments and were allowed to remain in contact with alooht^
for twelve hours. The alcohol was then squeezed cot an *
evaporated on a wat-er-bath. The residue obtained *^*
dissolved in water, placed in the receiver of a mercury pumpS
and treati-d with sodium hj-pobromite. By this method tib'
following results were obtained : —

Adductor mascles

• Proc. Hoy. Soc Ed!

PHYSIOLOG Y OF THE INVERTEBRA TA. 287

These resiilt» are expressed in milligrammes of urea per
100 grammes of muscular tissue.*

It is most probable that the formation of urea takes place
in the muscles. It is certainly present in the blood of Mya
ind AnodorUa. Milne-Edwards states that '4t is probable
bhat in all cases the secreted matter exists in the blood
ilready formed. It was thought, for example, that the urea
found in urine must be formed by and in the kidneys, since
it could not be detected by chemical analysis in the blood ;
bat if these organs be destroyed in a living animal, or re-
DEioved, urea will, after a certain time, be formed in the blood,
bhns clearly proving that the kidneys do not form it."

In the higher animals an abundant alimentation gives rise
bo a greater excretion of uric acid and urates. On the con-
trary, in abstinence the uric acid and its salts disappear, but
urea is excreted in greater quantity. This applies not only
o Vertebrates but also to many Invertebrates. Urea is a
>roduct of more or less complete oxidation of organic sub-
tonces, and is formed, as already stated, in muscular tissues,
ry the disintegration of the anatomical elements. Uric acid,
Q the other hand, is the result of an incomplete oxidation,
nd is produced for the most part in the bood or its equivalent,
rhen such fluid is surcharged with peptones which the tissues
re unable to assimilate. Secretion and excretion can be
raced back to the phenomena of nutrition — that is to say, to
he molecular acts effected in the midst of glandular cells,
rhich means that it can be accomplished without the iuter-
ention of the nervous system. Such is the case with the
owest Invertebrates ; but in the higher forms, possessing a
nore or less complete nervous system, secretion and excretion
ire largely influenced by nerves. It may be probable that
f the commissural cords connecting the supra-oesophageal
vith the sub-oesophageal ganglion were severed nervous
Ktimulus would not be supplied to the green glands of

* See also Smithes new method for estimating urea in thePharm, Journ^
Trans, [3], voL 21, p. 294.

'Z^

;88 PHYSIOLOGY OF THE INVERTEBRATA.

Astncvs, and consequently the secretion o£ urine wonH be
most probably influenced. At any rate, this is a qnestioB
for research. In the Vrr/i'hrn/a there is no donbt that th^
nervous centres do greatly modify the secretions. Forty-s»
years ago, Schiff demonstrated that lesions of the cerebia^
peduncles rendered thi.-' uriue albuminoua and acid. Clanii^
Bernard* proved that punctures of the roof of the fonrtl»
cerebral ventricle gave rise to the formation of glucose sagaC^
in the urine. Lesions of the isthmus and of the lower part^^^
of the cervical marrow can prevent the urinary excretion, or"
in other words, produce anuria.

There is no doubt that in the Intrrtfbrata the nervee play
an important part in the phenomena of eecretion,
even in the lower orders, where there are no traces of nervotia
elements, the protoplasm of the cells, being irritable, ie
capable of bringing into play the phenomena which we h
been discussing in the present chapter, £]xperimental evi-^— *
dence shows that the Amoiba, for instance, excretes, digests.^- -^i
and respires ; but so far at least as present microaoopic:^^*
expedients reach, this organism appears to be simply a smalF -^'

mass of protoplasm, nevertheless it has the power of adjust' ''

ing its low organisation to the environment. " In th^^-*
organism lies the principle of life ; in the environment attf.-^"^

the conditions of life. Without the fulfilment of these eon^ *"

ditioDS, which are wholly supplied by environment, there cai»— **'
be no life."

The wonderful adaptations of each organism, and of e»cl«=^^
part of every organism to its environment, inspire ua with m.^ *
sense of the boundless resource and skill of Nature in perfect- — ^^*'
ing her arrangements for each single life. The causes ot^cis'
these adaptations are to be sought in the numberless structtiral^^*'
modifications brought about by means of natural selectioE*''^'''
and by the ilin-d action of the environment.

As already stated, not only au organism as a whole, bo^c^wtt

each organ is also capable of undergoing modification. Hene^:^*''

• Ltfont de Phytiologie Opcraloire.

PHYSIOLOGY OF THE INVERTEBRATA. 289

t)he reason that there are strange facts to confront in deter-
mining the nature of an organ. For instance, the Malpighian
tabnles of the Insecta are diverticula of the alimentary canal,,
consequently they have been described as livers, and morpho-
logically they ought to have the function of a liver. But
iv^hen physiology, aided by chemical methods, steps in, we
find that these organs have solely a renal function. Is it
possible that the Malpighian tubules had originally the
fonction of a liver ? This is improbable, but it is well known
that an organ may lose its original function, and yet persist
l>ecaase it is of use for some other purpose : one of these
predominate at one time, another at another, and the organ
undergo structural modification in consequence.*

The variety of modifications or forms of the renal organs in
the Invertebi'ata may be illustrated by the table on pp. 290-1.

The table on p. 292 is a summary of the constituents
^present and absent) in the renal organs of the higher
Jhvertebrata.

In the lower InvertebrcUa the kidney performs other
Sanctions besides that of a renal organ ; but in the higher
iforms a special organ is set apart for that function, and it
3!e8embles in many respects the Vertebrate kidney.

On this point Prof. Huxley says : '* In the Vertebrata, the
-wetkal apparatus is constructed on the same principle [as the
Tenal organs of the Mollvsca] .... The Vertebrate kidney
is an extreme modification of an organ, the primitive type
^f which is to be found in the organ of Bojanus in the
Iklollusc, and in the segmental organ of the Annelid ; and, to
fp still lower, in the water-vascular system of the Turbellarian.
JLad this, in its lowest form, is so similar to the more com-
plex conditions of the contractile vacuole of a Protozoon, that
St is hardly straining analogy too far to regard the latter
ms the primary form of uropoietic as well as of internal
xespiratory apparatus."

* In the higher animals, for example, we hare the formation of a lang
Mnm a swimming bladder, and of the ear passage from a gill cleft.

390

PHYSIOLOGY OF THE INVERTEBRATA.

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CHAPTER X.

THE NERVOUS SYSTEMS OF THE INVERTEBRATA.

SfEBVOUS tissue consists of two distinct structural parts:
[a) nerve-cells and (6) nerve-fibres. The nerve-cells are
isnally found in aggregates termed ganglia or nerve-centres ;
ind ganglia are united to ganglia by nerve-cords or bundles,
v^hich consist of many delicate nerve-fibres. The latter act as
she conductors of nervous force ; in fact, " the characteristic
Function of nerve-fibres is that of conducting stimuli to a
listance. The function of nerve-cells is diflTerent, viz., that
3f accumulating nervous energy, and, at fitting times, of dis-
charging this energy into the attached nerve-fibres. The
aervouB energy, when thus discharged, acts as a stimulus to
:he nerve-fibre ; so that if a muscle is attached to the end of
i fibre, it contracts on receiving this stimulus. When nerve-
sells are collected into ganglia, they often appear to discharge
Dheir energy spontaneously; so that in all but the very
lowest animals, whenever we see apparently spontaneous
iction, we infer that ganglia are probably present." There
A another important point, viz., the difiEerence between
nuscles and nerves under the influence of a stimulus. " A
itimulus applied to a nerveless muscle can only course through
he muscle by giving rise to a visible wave of contraction,
'hich spreads in all directions from the seat of disturbance
s from a centre. A nerve, on the other hand, conducts
xe stimulus without sensibly moving or undergoing any
bange of shape. Therefore muscle-fibres convey a visible
"»ve of contraction, and nerve-fibres convey an invisible^ or

2g4 PHYSIOLOGY OF THE INVERTEBRATA.

molecular, wave of stimulation, Neire-fibreB, then, ar^
functionally distiuguished from muEcIe-fibres — and also froO*
protoplasm — by displaying the property of condncting itt-'"
visible, or molecular, waves of stimulation from one part <^ ^
an organism to anotber, so establishing physiological con —
tinuity between such parts, without the necesEary passag^^*
of waves of contraction." (Romanes.)

Nerve-fibres may be functionally divided into five gronpi»- ■ '^
— motoi;, sensory, vascular, secretory, and inhibitory. Whei^^ni
a nerve-fibre is stimulated from some nerve-centre, it tna^ ''
give rise to the contraction of a muscle or a blood-vessel, in- -»•
creased secretion from a gland, or a diminution or arrest o-^«3f
some other kind of nervous action.

In all these cases, " the nervous influence travels outward^^fc
from a ganglion or nerve-centre towards the periphery, tba— ^hs
presenting an analogy to ordinary motor nerves." Perhapi^ess
the best classification of ■iierec-Jilircs, from a physiolopie^E^aJ
point of view, ia the following ;

_ . . (a) Motor (efferent), excite contraction of moscle;.
e, g I (6) Fuicvlar (vaso-iDOtor), excite contraction of blood-vetoclB.
(<) &erttory, excite secretion.

{d) Inhihilory, affect other nerve-centres so as lo moderate m
"C V I destlo; their action.

§ V(e) VomKcting, which connect motor-cells in nerve-cent ce».

(i) Genera}, "convey to nene-oenttes in brm;
f inlluencea which caase seamtions of

vague cimracter {not permanent^"
— (n) Stniori/ -J {2) Sptciiil, ''convey I

% ^ I influences which ,

S E; gustatory, olfactory, or tactile

% £ 1 (6) ^jfcewi, "convey to nerve-oenl res influences whieli cause t:^*^/"'
^ g sensation, and which mBj'ormaynot be followed by fnrth^-***^

S I nervo OS activity."

O \c) Connccling, " which connect sensory cells in nervous cenlrw." " —

The centrifugal nerve-fibres convey influences ontwarc^ "^
from a nerve-centre ; while the centripetal nerve-Bbres cot*
vey influences inwards towards a nerve-centre. It should b

]

PHYSIOLOGY OF THE INVERTEBRATA. 295

borne in mind that the different nerve-fibres merely act as
condnctors, the effects depend upon the arrangements or
apparatuses at the end of the fibres.

It is the totality of the properties which nerve-cells and
nerve-fibres are capable of giving rise to, which constitutes
innervation.

When nerve-centres or ganglia are excited the activity or
energy produced is not the same in each case. Some produce
the sensations of light, sound, pain, &c. ; others are the cause
of secretion or locomotion; others are associated with
psychical states ; while a fourth exerts an influence over
other nerve-centres. These nerve-centres may be classified
as follows : (a) ** Receptive eentres, to which influences arrive
which may excite sensations or some kind of activity not
associated with consciousness. (6) Discharging ceiUres^
whence emanate influences which, according to structures at
the other ends of the nerves connected with them, may
cause movements (muscles), secretion (glands), or contractions
of vessels, (c) Psychical centres, connected with sensation, in
the sense of conscious perception, feeling, volition, intel-
lectual acts, and will, (d) Inhibitory centres, which inhibit,
restrain, or even arrest the action of other centres."

In the majority of cases there are terminal organs at the
commencement of sensory, and the terminations of motor
nerves. Such organs are seen in the rods and cones of the
retina and the terminal plates of muscle ; but in some few cases
nerve-fibres may terminate in loops towards the periphery of
the body or in the interior of organs.

We now proceed to describe the nervous systems in the
Invertebrata,

The Protozoa.

In none of these animals has any trace of a nervous system
been discovered; nevertheless, as nervous elements are nothing
more than the products of the diSerentiation of protoplasm,
it is logical to assume that certain parts of the protoplasmic

396 PHYSIOLOGY OF THE INVERTEBRATA.

cells of the Protoma, are the means of conveying nervou 1
energy. K no nervous system is anatomically differentiated,
there is every reaaou to believe that the protoplasm contaiua
a " diffiised nervoas system " (Gruber).

In these organisms innervation is rudiraeotary ; aud t^e
nei-vous function devolves uiion the protoplasm, which is the
cause of the phenomena of contraction, secretion, Ac, and
according to M. Binet, of certain psychical acts.

Certainly no definite nerve-tracts have been discovered il
these animals; "but any one who has attentively watchdj
the ways of a Colpocla, or stii! more of a Vortiedla, i
probably hesitate to deny that they |3oaaess some appi
by which external agencies give rise to localised and cfr "
ordinated movements. And when w© reflect that the essential
elements of the highest nervous system — the fibrils into wbich
the axis fibres break up — are filaments of the extremest
tenuity devoid of any definite structural or other cliaraoteri,
and that the nervous system of animals only becomes con-
spicuous by the gathering together of these iilaiuents in*^
nerve-fibres and nerves, it will be obvious that there are ^»*
strong morphological, as there are physiological, grounds fc
suspecting that a nervous system may exist very low i
in the animal scale, and possibly even in plants," (Hux3ey.^ )

Tl!E PORIFERA.

No differentiated nervous system has been discovered, 1
there is little doubt that nervous function is traceable in th-rf
protoplasm of these animals.

The nervous system of the homy sponges has beer^
recently examined by Dr. R. von Ledenfeld.' He gives a:^^^
account of Euspoit'/la avfracUiosa, which differs in aom*^
particulars from Euspmtgia officiiiaVts (the bath sponge^
The fine membrane which extends from the tips of the bora

■ Sitzimg$btrlchte der Sgl, Prtauiteiitn Akadtmii da
Berlin, i88s, p. 1015.

PHYSIOLOGY OF THE INVERTEBRATA. 297

fibres consists of parallel spindle-shaped cells, which are set
perpendicnlarly to the outer surface of the sponge ; they end
in extraordinarily fine tips. The protoplasm contains small,
bat highly and doubly refractive, granules embedded in a
aingle refractive substance. The grannies are so arranged as
to give the appearance of a kind of transverse striation. These
are muscle-fibres.

If the investigations of Ledenfeld are correct, we have in
these animals the beginning of a true nervous system.

The Ccelenterata.

Kleinenberg has shown that in Hydra the cells of the
ectoderm terminate internally in delicate processes from
which fine longitudinal filaments are produced. These fila-
ments form a layer between the ectoderm and endoderm.
According to Kleinenberg, these filaments are the represen-
tatives of both muscle and nerve ; in fact, he regards them
as neuro-muscular elements in an undifferentiated state.
Bat Prof. Huxley believes that Kleinenberg's fibres " are
solely intemuncial in function, and therefore the primary
form of nerve. The prolongations of the ectodermal cells
liave indeed a strangely close resemblance to those of the
cells of the olfactory and other sense-organs in the Vcrtebrata ;
«nd it seems probable that they are the channels by which
dmpulses affecting any of the cells of the ectoderm are con-
veyed to other cells and excite their contraction."

Dr. G. J. Romanes, F.R.S.,* has shown that in the Mcdusoo.
^^e find phenomena similar to nervous transmission sent along
definite tracks, or sometimes diffused from one part of the
Tx)dy to the other, without any histological trace of differen-
tiated nerve-fibre. As in the- Protozoa, we have in these
cuiimals the early stages of the evolution of a nervous system.

* Philosophical Traniactions of RoifcU Society ^ 1875, p. 269 ; ibid, 1877,
JP> 659 ; ibid. 1879, p. 161 ; and his book, JeUyfish, Starfish and Sea

293 PHYSJOLOGY OF THE INVERTEBRATA.

Prof. E. Haeckel ' has described the nervous system of the
Gcryonidc.: It fomiB a circle all rouDd the margin of tho
nectiOCalyx (umbrella), " folio wiug the course of the radial
(notrient) tubes throuffhoat their entiro length, and pro-
ceeding also to the tentacles and marginal bodies.'' Then-
is a ganglion at the base of each tentacle from which ih^
above-mentioned nerves take their origin. These ganglia
contain fusiform and nucleated cells of high refractive
power. " The nerves that emanate from the ganglia air
composed of a delicate aud transparent tissue, in which no
cellular elements can be distinguished, but which is longitu-
dinally striated in a manner very suggestive of fibrillation.
Treatment with acetic acid, however, brings out distinct
nuclei in the case of the nerves that are situated in tlie
marginal vesicles, while in those that accompany the radi»l
canals, ganglion-cells are sometimes met with." Haeclcel's
i-esearches have been confirmed by AUman, Claua, Usrtiog.
Romanes, and others.

According to Dra. 0. and R. Hertwig,t the nervous syatefn
of the naked-t^yed Afccluxw consists of two parts, a centra'
and a peripheral, " The central part is localised in tU^
margin of the swimming-bell, and there forms a nerve-rin^^-
which is divided by the insertion of the veil into an upp^^^
and a lower nerve-ring, .... In all species the upp^^^'
nerve-ring lies entirely in the ectoderm. Its principal mu
is composed of nerve-fibres of wonderful tenuity, amoi
which are to be found sparsely scattered ganglion-cell -*^
.... Tlie fibres which euianate from them are very deL^f-
cate, and, becoming mixed with others, do not admit of beiiE:^^"''^
further traced."

"Beneath the upper nerve-ring lies the lower nerve-rio .^k^?'
It is inserted between the mnscle-tissne of the veil a^c— ""
umbrella, in the midst of a broad strand wherein muset -'^
fibres are entirely absent." The lower nerve-ring belon^c:^^

iK^er J/.

' PHYSIOLOGY OF THE INVERTEBRATA. 299

to the ectoderm, and consists also of nei:\re-fibres and
ganglion-cells. In these respects there is no difference
between the lower and upper nerve-rings; but it may be
remarked that a difference is distinguishable between the
two. In the former there are many nerve-fibres of con-
siderable thickness, whereas in the latter the nerve-fibres are
exceedingly slender, and there are few ganglion-cells. ''The
two nerve-rings are separated from one another by a very
thin membrane, which, in some species at all events, is bored
through by strands of nerve-fibres which serve to connect the
two nerve-rings with one another."

"The peripheral nervous system is also situated in the
ectoderm, and springs from the central nervous system, not by
any observable nerve-trunks, but directly as a nervous plexus
composed both of cells and fibres. Such a nervous plexus
admits of being detected in the sub-umbrella of all MedHsce,
and in some species may be traced also into the tentacles."

This nerve-plexus is situated between the muscle-fibres and
the epithelium. " There are also described peculiar tissue
elements, such as, in the umbrella, nerve-fibres which pro-
bably stand in connection with epithelium-cells ; nerve-cells
which pass into muscle-fibres, similar to those which Kleinen-
berg has called neuro-muscular cells ; and in the tentacles
neoro-muscular cells joined with cells of special sensation.
No nervous elements could be detected in the convex surface
of the umbrella, and it is doubtful whether they occur in the
veil." (Romanes.)

The nervous system of the covered-eyed differs from that
of the naked-eyed Meduscv. In the former the central
nervous system consists of separate centres unconnected with
commissural cords. There are eight, twelve, or sixteen (but
generally eight) of these nerve-centres situated in the
margin of the umbrella. They consist of cells of special
sensation and a thick layer of delicate nerve-fibres. These
nerve-fibres are merely prolongations of epithelial cells, as
true ganglion-cells are entirely absent.

30O PHYSIOLOGY OF THE INVERTEBRATA.

Professor K A. Schiifer, F.R.S.,* lias shown the presence
of " an intricate plexus of cells and fibres overspreading the
Bub-umbrella tissue " of Aurdia aurila. Dr. Clans has nlso
described the presence of nnmerous ganglion-cells in the
sub-umbrella of Chnjsiium,

It appears that as far as the nervous system is concerned.
the naked-eyed are more highly developed than the covered-
eyed Mcdu.'ifc.

It is now our intention to briefly allude to the important
researches of Dr. G. J, Romanes.f which have been ma(l<
from the stand-point of experimental physiology. He hM
studied — (n) the effects of excising the entire margins of tJw
nectocalycea of both the naked-eyed and the covered-ej"<4'
Mrihisa: ; (h) the effects of excising certain portions of
margins of the nectocalyces ; (c) the effects upon the
brium of excising the margin of a nectocaiyx (swimi
organ); and he has arrived at the following conclnsions :—

" With a single exception to hundreds of observatiiio*
upon BLt widely divergent genera of naked-eyed Moiutcr^ I
find it to be uniformly true that the removal of the extreme
periphery of the animal causes instantaneous, complete, w"*
permanent paralysis of the locomotor system. In the geoo*
Salvia, my observations point very decidedly to the coaclo-
aion that the principal locomotor centres are the raargii*
bodies, but that, nevertheless every microscopical portion "
the intertentacular spaces of the margin is likewise endowed
with the property of originating locomotor impulses.

" In the covered-eyed division of the Mciiii!<a. I find tl»*
the pnnripal seat of spontaneity is the margin, but that ^^
latter is not, as in the naked-eyed Meilinvi; the rsdusirt sett
of spontaneity. Although in the vast majority of cax* ^
have found that excision of the margin impairs or deBtrty
the spontaneity of the animal for a time, I have also fo>n>*
that the paralysis so produced is very seldom of a

t- hu
}f the I

''' V

ltt()B*^|

■ Pliilo<oplilral Tfaiii

I have also fpa"* j
>m of a permsiK'^^l

PHYSIOLOGY OF THE INVERTEBRATA. 301

nature. After a variable period occasional contractions are
usually given, or, in some cases, the contractions may be
resumed with but little apparent detriment. Considerable
differences, however, in these respects are manifested in
different species, and also by different individuals of the
same species. Hence, in comparing the covered-eyed group
as a whole with the naked-eyed group as a whole, I should
say that the former resembles the latter in that its repre-
sentatives usually have their main supply of locomotor centres
situated in their margins, but that it differs from the latter
in that its representatives usually have a greater or less
supply of their locomotor centres scattered through the
general contractile tissue of their organs. But although the
locomotor centres of a covered-eyed Medusa are thus, generally
speaking, more diffused than are those of a naked-eyed Medusa^
if we consider tlu organism as a whole, the locomotor centres
in the margin of a covered-eyed Medusa are less diffused
than are those in the margin of a naked-eyed Medusa, In
no case does the excision of the margin of a swimming
organ produce any effect upon the movements of the
manubrium."

Romanes has proved the effects of various stimuli upon the
Medusee. After the removal of the locomotor centres (ganglia)
all these animals invariably respond to stimulation, but the
degrees of irritability in responding to stimuli differ con-
siderably in different species.

The covered-eyed, and a few of the naked-eyed Medusae
respond with one or more contractions to the action of light.
In the case of Sarsia tuhulosa, a flash of light causes it to
respond ; in fact, light acts as a stimulus. It has been ob-
served that the marginal bodies of Sarsia are organs of special
sense, adapted to respond to luminous stimulation ; in other
words, they perform the function of sight — in fact, the marginal
bodies are rudimentary eyes.

Romanes has shown that when these marginal bodies are
excised, the mutilated animals did not seek the light, ** but

302

PHYSIOLOGY OF THE INVERTEBRATA.

swam liither and thither without paying it any ref»rf.'
Saisifi (iihitloi^t and Tiaropfdn polydiadrviata are probably th»
only two naked-eyed Malii-st spnaitive to light. But thf
action of light on Sarsi/i and Tuirojm'.f differs cx>n8iderablT.
In the case of the latter, sunlight causes it to go into a kind
of tonic sjiasm — the whole of the nectocalyx being drawn to-
gether. The period of latency * in i^ai-jtia is instantaneout
with all stimulations (mechanical, electrical, luminous, 4c.);
but in 7'i'/iro}>sirf the period of latency i.s not iiiatanlaueous
with luminoua stimulation, for a little more than a second
elapses after thi? first occurrence of the stimulus. With all
other stimulations, in Tiaro]>M-x, the period of latency is in-
stantaneous. Romanes has shown "that the enormously lonii
period of latent excitation in response to luminous etimuli
was not, properly speaking, s period of latent excitaticia »'
all ; but that it represented the time during which a eertnin
summation of stimulating influence was taking place in tin-
ganglia, which rec[uired somewhat more than a second t"
accumulate, and which then caused the ganglia to oricritis^
an abnormally powerful discharge." The ganglionic matl*^
of Tiaivp^iis represents, according to Komanes, the most rnd*'
mentary type of visual organ.

All the excitable parts of the Medtiaec are highly seneiti^*
to electrical stimulation, but the most sensitive partd are th(^**
which correspond with the diatribntion of the main nertr ■^
trunks. The external or convex surface of the nectoca!^"^ '
and the whole of the "gelatinous substance to '
the neuro-muscular sheet is attached," are inBeoBitivt
'Stimulation.

The extreme sensitiveness of the tissues to electrical stimid
tion suggested to Komanes the idea of ascertaining wbetl^^
there is any localization of definite excitiii'le tracts in th^^*
animals. In the case of Sarsia, " the apex of the swimmii^^
hel! is much the least excitable portion of the animal: fc— ^

PHYSIOLOGY OF THE INVERTEBRATA. 303

QEi this point downwards to the margin there is a beantifnl
I nninterrapted progression of excitability, the latter being
atest of all when the electrodes are placed upon the
ing of cells described by Agassiz as nerve-cells." In regard
^ the marginal tract of excitable tissue, the degree of ex-
ibility differs slightly in different parts." In other parts
ihe nectocalyx there is '' a marked difference between the
itability of this organ when the electrodes are placed upon
r one of the fonr radiating canals (and so upon the ascend-
; nerve-chains described by Agassiz), and when the
Ttrodes are placed upon the tissue between any of
canals. The ratio is generally about 9 centims. to
centims."

}onceming the action of electrical stimulation the following
.dosions have been arrived at by Romanes : —
i) '* The excitable tissues of the Medttsw, in their behaviour
'ards electrical stimulation, conform in all respects to the
es which are followed by the excitable tissues of other
mals. Thus closure of the constant current acts as a
eh stronger stimulus than does opening of the same, while
reverse is true of the induction-shock.
2) "Different species of the Meclusce manifest different
prees of sensitiveness to electrical stimulation, though in
cases the degree of sensitiveness is wonderfully high.
'3) " When the constant current is passing in a portion
the strip of a severed margin, the nectocalyx sometimes
nifests uneasy motions during the time the current is
sing. It is possible, however, that these motions may be
rely due to accidental variations in the intensity of the
rent.

4) " When the intrapolar portion of the severed margin
^urophora laciniata happens to be spontaneously contract-
prior to the passage of the constant current, the moment
I current is thrown in, these spontaneous contractions
m cease, and are then seldom resumed until the current
in is broken, when they are almost sure to recommence.

304 PHyS/OLOGV OF THE INVERTEBRATA.

This effect may bo produced a great number of times *^
succesBion.

(5) " Exlianation of the excitable tissue of the nectocaly^ '^
may be easily shown by the ordinary methods. Exhanstf'^ ^
tissue is much less sensitive to stimulation than is fiv^^"
tissue. Moreover, ao far as the eye can judge, the contrac:^^'
tion is slower, and the period of latent stimulation prolongecr^.

(6) " The tetanus produced by faradaic electricity is nf ^'

of the nature of an apparently single prolonged contractio— b
(except, of course, such among the naked-eyed Medusa ^^mi
respond to all kinds of stimuli in this way), but that of i
number of contractions rapidly succeeding one another — ^^9B
in the heart under similar excitation."

Romanes, in his important papers {lor. cit.), has shown ttr^e
amount of section which the neuro-muscular tissues of itr^e
Afmlusa: will endure without suffering loss of their physiol^cn-
gical continuity : and this is in the highest degree astonishin ^■
He has also investigated the rate of transmission of RtimoL i :
as well as the regeneration of excitable tissues in the-^=^
animals (i.e., after injur}'). It may be remarked that if t*=3e
contractile sheet, which lines the nectocalyx is complete- ^y
severed throughout its whole diameter, it again reunites, ^Dr
heals up, in from four to eight hours after the operation.

The nervous system of the naked-eyed J/n/w.w is mc^^'*
highly developed than it is in the covered-eyed Mediistr ; aK=^^
Itomanes has demonstrated the occurrence of reflex ■cti^^*"'
in the Methi.'^t. This reflex action occurs " only between i^^^*
marginal ganglia (in •^rsia) and the point of the hell frc^^^'"
which the nianuhrium is suspended — it being only the p^*"^''
which is exerted upon this jjoint when the manubrium cc^^^^^'
tracts and acts as a stimulus to the marginal ganglia."

Romanes has brought much physioh<jical evidence to be—'*^*'"
on the distribution of nerves in Sarsia and it may be staC::^**'
that his researches prove " that nervous connections unite U^S*"^
tentacles with one another and also with the manubrinm ; *""
perhaps more precisely, that each marginal body acts a— ^*

PHYSIOLOGY OF THE INVERTEBRATA, 305

co-ordinating centre between nerves proceeding from it in
four directions — viz,^ to the attached tentacle, to the margin
on either side, and to the manubrium."

" The nervous connections between the tentacles and the
mannbrium are of a more general character than those between
the tentacles themselves ; that is to say, severing the main
radial nerve-trunks produces no appreciable effect upon the
sympathy between the tentacles and the manubrium.

"The nervous connections between the whole excitable
surface of the nectocalyx and the manubrium are likewise of
this general character, so that, whether or not the radial
nerve-trunks are divided, the manubrium will respond to
irritation applied anywhere over the internal surface of the
nectocalyx. The manubrium, however, shows itself more
sensitive to stimuli applied at some parts of this surface than
it is to stimuli applied at other parts, although in different
specimens there is no constancy as to the position occupied
by these excitable tracts."

Bomanes has examined the distribution of nerves in
Tiaropsis (especially T, iyuhcans*), Stauropliora^ Aitrclia, and
other Medusce. In all these forms primitive nerves are well
developed. By the word " nerves " is meant certain physio-
logically differentiated tracts of tissue, which either stimu-
lation or section prove to perform the function of conveying
impressions to a distance.

Romanes has also studied the subjects of co-ordination
and natural and artificial rhythm in the Mcdiisce ; but it is
not our object to detail these important investigations, as a
full account of them will be found in the Philosophical Trans-
adiojis of the Royal Society^ to which our readers are referred.
Nevertheless, the following may be taken as a general
summary of the results : —

(i) That in the covered-eyed Mcdusm the lithocysts are

* This species was first described by Romanes ; see Journ. Linn. Soc,
{Zooi.), vol. 12, p. 524-

306

PHYSIOLOGY OF THE JNVERTEBRATA.

the exclusive seats of spontaneity, so far as tlie"|>ri[
movements " are concerned.

(2) The rate of the natural rhythm has a tendency to
an inverse ratio to the size o£ the individnal, though, it nay
be remarked, that size is not the only factor in detormiini^
ancli rate.

(3) The cutting off the manubrium (polyprite) or a portion
of the nectocalyx (swimming-bell), causes, first acceleration
of the rhythm, aud then a progressive decline to a certain
point below the original rate. The rate then remBins
stationary at this point, but may again be made temporarily
to rise and permanently to fall by removing another portion
of the nectociilyx. " In theee experiments the rhythnii
besides becoming permanently slowed, is also olt«Q rendered
permanently irregular. Again, paring down the contractile
tissues from around a single lithocyst" has the effect, when
the tissue is greatly reduced, of giving ri^e to enormonslj
long periods of inactivity. During such period, bowew,
stimulation may initiate a bout of rhythmical contraction*,
to be followed by another prolonged pause. These facta Und
to show that the apparently automatic action of the lithe
is really due to a constant stimulation supplied by
parts of the organism."

(4) " Temperature exerts a profound influence on the
of rhythm. This inHuence may be best observed within
moderate limits of variation ; for water below 20° C. SBSpenns
spontaneity and even irritability, while water above 70
permanently slows the rhythm after baring tem|
quickened it. But water between 50''and6o'C.
quickens the rhythm during the time that the Mfdi
have been removed from colder water, are exposed to
influence. In verj- cold wat*r the loss of spontaneity i*
gradual though rapid process, as is also its return in wi
water. After having been frozen solid, Aurdia will

■ The tnaz^inftl bodiee iu Ihe coyered-eycd iledunr occmi in Uie (oi**|
little bags of crystals ; hence they have been termed lithocyslsi

PHYSIOLOGY OF THE INVERTEBRATA, 307

on being thawed out, but the original rate of rhythm was
not observed fully to return."

(5) Oxygen accelerates the rhythm, while carbonic anhy-
dride retards it, and in strong doses destroys both sponta-
neity and irritability. Deficient aeration of the water in
which the Mediisoe are living, causes iiTegalarity of their
riiythm, as well as the occurrence of pauses ; until at last
spontaneity altogether ceases; but on now removing the
animals to fresh sea-water, their recovery is surprisingly
sudden.

(6) As regards stimulation, Romanes has shown that a
few drops of hot water allowed to run over the excitable
tissaes of these animals cause a responsive contraction.
Single mechanical or chemical stimuli applied to paralyse the
nectocalyces of covered-eyed Mcdusce frequently produces in
response a small series of rhythmical contractions.

(7) Light acts as a powerful stimulus to some species of
Medusce; and it may be stated that the stimulus has been
proved to be light per s€y and not the sudden transition from
darkness to light.

(8) The period of latent stimulation in the case of Aurdia
aurita is greatly modified by certain conditions. Of these,
temperature exerts the greatest influence, but the most im-
portant influence, from a physiological point of view, is that
of the summation of stimuli. At the bottom of a '' stair-
case" the latent period is | of a second, while at the top
of a " staircase " it is only J of a second. Summation of
stimuli also greatly increases the amplitude of the contrac-
tions ; so that it both develops in the tissue a state of ex-
pectancy and arouses it into a state of increased activity.

(9) The excitable tissues of Aurelia may be thrown into
tetanus by means of strong faradaic stimulation ; and Romanes
has proved that the the tetanus is due to the summation of
contractions.

(10) Beflex action occurs in various species of Medusce,
In Sarsia definite nervous connections of constant occurrence

308 PHYSIOLOGY OF THE INWERTEBRATA.

have been sliown to exist between the teotacula, but aoi
between the tentacula aud polj'pite. Section of the i
muscular sheet proves that in the cose of this genus phyot
logical harmony may. as a rule, be easily destroyed, althong. ~^t
it occasionally happens that such is not the case.

(11) Romanes has shown that the essentially nervoic^ .m
function of maintaining excitiitiorMl coiUinvity is ablii t^^^o
persist in. these primitive nervous tissues after they ha't^^Mre
been subjected to the severest forms of section. This fa^^^it
" cannot be explained by Kleinenberg'a theory of donbl- -^
function Cells; for sometimes contractile waves wU! becon^^e
blocked by section before the tentacular waves, and sometim^ ■*»
vice versd. We seem, therefore, driven upon the theory of s
nerve-plexus, whose constituent elements are capable -«'
vicarious action in almost any degree."

(12) Contractile waves in Aurdia travel at the rate of
18 inches per second, if the temperature of the water is
normal ; but the rate is greatly modified by temperata '*v<
straining, anaasthetics, and various foreign substances. Sti '^-
ulus-wavea only travel at the rate of 9 inches per second .^ "
the stimulus wiiich starts such a wave is not strong enougl»- ^
the same time to start a contractile wave ; but if the stimu ^"i
is strong enough to start both waves, they both travel *'
about the same rate.

(13) There appears to be no further co-ordination amc^^^E
the lithocyats of the covered-eyed Mediisct- than such as ari- ^*
from contractile waves coursing rapidly from one of ^BE"^
number, and, as it passes the others, causing them snipes-'- **"
sivfly to discharge ; but, in the case of the naked-©^^™
Mtdnsa, true co-ordination has been proved to occur betw^^^"
the marginal ganglia, and the tracts through wliich iC::*- "
effected have been proved to be the marginal nerves. Sligfc^' ■
cutting the margin of a naked-eyed Mediisa exerts a r ^^
deleterious influence upon the vigour of the animttl; ^^o"
violent nervous shock, while it always suspends t^*""
spontaneity and irritability, will sometimes also desf".*^

PHYSIOLOGY OF THE INVERTEBRATA, 309

co-ordination for a considerable time after spontaneity
returns.

(14) Bomanes has ascertained the effects of the following
poisons — chloroform, amylic nitrite, caffein, strychnia, mor-
phia, curare, veratrinm, digitalin, atropin, nicotin, alcohol,
and potassiom cyanide — upon the Medicscc,* He has shown
"that there is a wonderful degree of resemblance between the
actions of the above-mentioned poisons on the Mcdusce and
on the higher animals. This is a most important discovery,
especially " when we remember that in these nerve-poisons
"we possess so many tests wherewith to ascertain whether
nerve-tissue, where it first appears upon the scene of life,
presents the same fundamental properties as it does in the
liiglier animals." In fact the primitive nervous tissues of
"the Medusce adhere to the rules of toxicology that are followed
"by nervous tissues in general. " In one respect, indeed, there
is a conspicuous and uniform deviation from these rules;
for it has been observed that in the case of every poison
mentioned, more or less complete recovery takes place when

* Fresh water acts as a deadly poison to the Afedusa^; and brine acts as
an anaesthetic. The fresh-water 3Jedusa {Limnocodium JSorbii) is even more
intolerant of sea water than are the marine species of fresh water; and
brine acts as a poison to the fresh- water form. "We have thns a curious
set of cross relations. It would appear that a much less profound physio-
logical change would be required to transmute a se£|.-water jellyfish to a
jellyfish adapted to inhabit brine, than would be required to enable it to
inhabit fresh water. Yet the latter is the direction in which the modifica-
tion has taken place, and taken place so completely that the sea water is
now more poisonous to the modified species than is the fresh water to the
unmodified. There can be no doubt that the modification was gradual —
probably brought about by the ancestors of the fresh water Medusa pene-
trating higher and higher through the brackish waters of estuaries into the
fresh water of rivers — and it would be hard to point to a more remarkable
case of profound physiological modification in adaptation to changed con-
ditions of life. If an animal so exceedingly intolerant of fresh water as is
« marine jellyfish, may yet have all its tissue changed so as to adapt them
to thrive in fresh water, and even die after an exposure of one minute to
their ancestral element, assuredly we can see no reason why any animal in
«arth or sea or anywhere else may not in time become fitted to change its
dement. " (Homanes. )

3IO PHYSIOLOGY OF THE INVERTEBRATA.

the influence of the poison has been removed, even thon^*
thia has acted to the extent of totally suspending iiTitabUit-.^S'
In other woi-ds, there is no poison in the above list, which h^^
the property, when applied to the J/ec/usw, of destroying li^Es
till long after it has destroyed all signs of irritability." ^

an explanation of this peculiarity it should be borne in min id

"that in the Mahisa' there are no nervoua centres of 6DC^:^b
vital importance to the organism that any temporary sm '-
pension of their functions is followed by immediate deatl^li.
Therefore, in these animals, the various central nerve-poisoi^:^i8
are at liberty, so to speak, to exert their full intluence on ^^all
thL- excitable tissues without having the course of their actic^zz)n
interrupted by premature death of the organism, which inn
higher animals necessarily follows the early attack of t ^Be
poison on a vital nerve-centre." Then, again, the mode of
administering the poisons to the Mcduscr was different frr — mm
that which is generally used when administering them to t-^e
higher animals.

(15) Romanes' researches prove that the phenomena of
mascnlar tonus, as they occur in Surnia, tend more in favc:i:"Dr
of the exhaustion, than of the resistance, theory of ganglior^mc
action. " The exhaustion theory supposes that the rhythic^ '=
largely due to the periodic process of exhaustion and recov^^"?
on the part of the responding tissues."

Besides the researches on the nervous systems of ^K"*
Malusa, Dr. Eimer* has investigated the nervous system '^''
the Ctnwph'jm. In these animals the mesoderm contft- '^"^
numberless fibrils, varying in diameter from soj^nt to 15^^'^
of an inch. " These fibrils present numerous minute vaji_- '^
sities, and, at intervals, larger swellings which contain nuc^ ''''■
each with a large and refracting nucleolus. These fibrils t^^^''^
a straight course, branch dichotomously, and end in still fi"^^*"""
filaments, which also divide, but become no smaller. T^tJ''/
terminate partly in ganglionic cells, partly in muscular fib'***
partly in the cells of the ectoderm and endoderm. Man^^"'

• Zoaltylidie Sludirii auf Copr-', 1873.

PHYSIOLOGY OF THE INVERTEBRATA, 311

the nerve fibrils take a longitudinal course beneath the centre
of each series of paddles, and these are accompanied by
ganglionic cells, which become particularly abundant towards
the aboral end of each series. The eight bands meet in a
central tract at the aboral pole of the body ; but Eimer doubts
the nervous nature of the cellular mass, which lies beneath
the lithocyst, and supports the eye spots."

Professor Huxley says that **the nervous system of the
Ctenophoran is, therefore, just such as would arise in Hydra^
I the development of a thick mesoderm gave rise to the
separation and elongation of Kleinenberg's fibres; and if
special bands of such fibres, developed in relation with the
jliief organs of locomotion, united in a central tract directly
H>iinected with the higher sensory organs. We have here, in
ihort, virtual, though incompletely difierentiated brain and
serves."

In the Adinozoa, there is a plexus of fusiform ganglionic
sells connected by nerve-fibres at the base of the body ; and
^t the base of the tentacula of the Actinicv^ near the pigment-
3ells (eyes ?) isolated nerve-cells have been discovered.

The Echinodermata.

Among these animals the nervous system consists of a
number of ganglia, connected by commissural cords, so as to
form a ring, from which nerve-fibres pass to various parts of
the body.

" The internal nervous system of Echimis consists of five
radial trunks, which may be traced from the ocular plates
along the ambulacral areas, external to the radial canals to
the oral floor, where they bifurcate and unite with each other,
80 as to form a pentagonal nerve-ring. This ring lies between
the oesophagus and the tips of the teeth, which project from
the lantern. Small branches leave the ring and supply the
oesophagus, and lateral branches arise from the several trunks
to escape with the pedicels through the apertures of the pore

312 PHYSIOLOGY OF THE INVERTEDRATA.

plates. Each trunk lies in a sinns (Fig. 56, c) ataab
between the lining membranB of the shell (Fig- 56,'f)aDdtli
aTubolacral radial canal (Fig. 56, e) ; the lateral braocb

a — ampulla:,
of ihell. I
^ = pedicel, h = spine, i — pcdicellaria. i = layer of fibres ei

nerve-plexus. / — plcius cjilendiog ova k

!' = plexiii eilendirg over pedicellnria lowards base of muidiblea.
mis. H = laleral branch from nervc-trunlt. a = continualioaoTIia
f = porlion of lateral branch, r = ambutacral plate,

which accompany the first series of pedicels tlirougl the
floor are large and deeply pigmented; the other brancM
within the auricles are small; those external totheaurics

PHYSIOLOGY OF THE INVERTEBRATA. 313

gradually increase in size until the equator is reached, and
from the equator to the ocular plates thej again diminish."
The nerve-trunk is enveloped by a fibrous sheath containing

Fic. 57.— Sthuctuhe of a Nerve.

(^Aficr Romanes and Ewai

pigmented cells. The nerve-trunk consists of deticato fibres,
and of fusiform cells (Fig. 57). The cells are nucleated,

" The lateral branches of the nerve-trunk escape along with,
and are partly distributed to, the pedicels ; the remainder
breaks up into delicate filaments, which radiate from the base
of the pedicel under the surface epithelium (Fig. 56, V),
When one of the large branches is traced through the oral fioor
after sendbg a branch to the foot, it breaks up into delicate
fibres, some of which run towards the bases of the adjacent
spines and pedicellari^, while others run inwards a short
distance towards the oral aperture."

There is also an external plexus situated under the surface
epithelinm, and extending from the shell to the spines and
pedicellaria3. "The fibres (Fig. 58) of this plexus closely
resemble those of the lateral branches of the trunk ; but
i^nerally they are smaller in size, and have a distinct con-
nexion with nerve-cells. The cells consist of an oval nucleus
uid of a layer of protoplasm, which is generally seen to
sroject in two, or sometimes in three, directions — the several
jroceases often uniting with similar processes from adjacent
Mils, 80 as to form a fibro-cellular chain or network."

Bomanes and Ewart * have succeeded in tracing the plexus
:iTeT the surface of the shell between the spines and pedi-
• PiibnifiAtcaf 7VaiMiic(ion», 1881, pt. ili. p. 836.

j[4 PHYSIOLOGY OF THE INVERTEBRATA.

cellariffi ; and from the surface of the shell to the capi
masclea at the bases of the spines (Fig. 59).

—EXTERNA!, NBRVE-PI-EXUS OP EdtlHUS.

{A/icr Romanes and Ewaht.)

" In the case of the pediceUarire, the plexns on readiiV
the 3tPm runi along between the calcareous axis and "W

suiface epithehum, to reach and extend orer and between fl

ma'ciilar and connective tissne-fibrea between tht calca

PHYSIOLOGY OF THE INVERTEBRATA. 315

uds and the bases of the mandibles (Fig. 56, V, and Fig. 60).
rbe plexus, now in the form of exceedingly delicate fibres
wnnecting small bipolar cells, reaches the special mnacles
A the mandibles Altbongh this plexus is especially

iAfttr Romanes und Ewaht.)

related to the mascalar fibres — lying over and dipping in
between them — it is also related to the surface epithelium,
and delicate fibres often extend from it to end under or
between the epithelial cells."

Bomanea and Ewart have shown that the Eckinodermala
respond to all kinds of stimnlation. The period of latency
TuieB considerably in different species, and in different parts
of the same animal.

" The external nerve-plexus supplies innervation to three
lets of oi^ns — the pedicels, the spines, and the pedicellarite ;
ibr when any part of the external surface of Eckinva is
kiached, all the pedicels, spines, and pedicellari^e within
•each of the point that is touched immediately approximate
md close in upon the point, so holding fast to whatever body
nay be need as the instrnment of stimulation. In executing
:ihis combined movement the pedicel]aria3 are the most
u^ive, the spines somewhat slower, and the pedicels very
mach slower. If the shape of the stimulating body admits
sf it, the forceps of the pedicellariss seize the body and hold
it till the spines and pedicels come up to afisist."

The function of the pedicellaria} is to aid locomotion by

316

PHYSIOLOGY OF

THE INl'ERTEBRATA.

cUmhil

grasping hold of sea-weeda, Ac, when an Etkh
perpendiculnr or inclined surfaces of rock.

Starfishes (with the exception of Brittle-stars) andi
are attracted by light, but when their eye-spots are remw
they no longer are so. Romanes and Ewart have demOf
strated that severing the ray-nerve destroys all pbysiolog
continuity between the pedicels on either side of the divi
Severing the nerve at the origin of each ray, or sereringd

nerve-ring (Fig. 6i) between each ray, has the effect of
totally destroying all co-ordination among the rays ; " the""
fore the animal can no longer crawl away from injnries, ""^
when inverted it forms no definite plan for righting itsel'"
each ray acting for itself without reference to the otbe'*'
there is, as a result, a promiscuous distribution of spirals W'
doublings, which as often as not are acting in antagomsBi
one another. This dirision of the nerves, although eo

]

PHYSIOLOGY OF THE INVERTEBRATA. 317

I7 destroying physiological continuity in the rows of
^Is and muscular system of the rays, does not destroy, or
jptibly impair, physiological continuity in the external
3-plexus ; for however much the nerve-ring and nerve-
bs may be injured, stimulation of the dorsal surface of
animal throws all the pedicels and muscular system of
rays into active movement. This fact proves that the
^Is and muscles are all held in nervous connexion with
mother by the external plexus, without reference to the
:rity of the main trunks."

le function of the spines and pedicellaria) in Echinus are
ndent upon the external nerve-plexus ; for if the latter is
ed they have not the power of localising and closing,
i a seat of stimulation. But *^ other nervous connexions,
which another function of the spines depends, are not
e smallest degree impaired by such injury. This other
:ion is that which brings about the general co-ordinated
n of all the spines for the purposes of locomotion. That
function is not impaired by injury of the external plexus
oved by severely stimulating an area within a closed
)f injury on the surface of the shell ; all the spines over
rhole surface of the animal then manifest their bristling
>ments, and by their co-ordinated action move the
al in a straight line of escape from the source of irri-

will be apparent from the above remarks that there is a
reflex function of the spines and pedicellariaD, which is
ely dependent upon the external nerve-plexus. There
10 the universal reflex function of the spines, which con-
in their general co-ordinated action for the purposes of
lotion, and which is entirely independent of the external
3-plexus.

le nerves which give rise to the universal reflex function
istributed over the internal surface of the shell — that is
form an internal nerve-plexus,
le internal nerve-plexus of Echinus has been recently

3iS PHYSIOLOGY OF THE JNVERTEBRATA.

discovered by Dr. J .0. Ewart, of Edinbargb Universitj. Ee
has found that this " internal plexus spreads all over the
inside of the shell, and is evei'ywhere iu communication with
the external plfxua by means of fibres, which pass betwMn
the sides of the hexagonal plates of which the shell of the
animal is composed."

The nerve-centres in Ediinm are to be found in the nerve-
ring, for as scton as the latter was removed, the animal lost,
complettty and permanently, all power of co-ordination among
its spines^-i.(\, thu function of locomotion was entirely lost.
Although locomotion was destroyed, the spines were uot
entirely paralysed or motionless, for they still retained (hf
power of closing round a seat of irritation on the esteninl
Burface of the shell. This is due to the fact that all tbe
spines and pedicellariEe are connected with the extenuil
plexus, and when it is irritated, all the spines and pedicelltinii.'
in the vicinity move over to the seat of irritation. " On the
other hand, it is the internal plexus which serves to unite lU
the spines to the nerve-centre which surrounds the monlii,
and which alone is competent to co-<irdinate the action of »ll
the spines for the purposes of locomotion."

Dr. Romanes* has shown experimentally that the md-
bulacral feet of Echinus are co-ordinated by the neive-ceutrei
quite as much as are the spines. The nervous system «
Echinm consists of the following parts (Table, p. 319).

Dr. L. Fredericqt has also investigated the nervous Bjatem
of Eckiniis. He finds that the pentagonal nerve-ring and it^
five radial nerve-trunks are contained in as many sheatlu.
which are expansions of the lining membrane of the sIk'"'
The lateral branches of these nerves are also contained U"
similar sheath ; the latter pass out of the ambnlacr&l pore* '"
company with the pedicels, which they serve to enervatei *
delicate nerve running along the whole length of each peaWJ*'
to terminate at its distal end in a tactile organ. T'"'

• See JelluM; Stur/uli, and Sea-Urehini, pp. 307-317.

+ Archil', de Zool. Kxperi. et Gin^alt, tome 5, pp. 419-440.

PHYSIOLOGY OF THE INVERTEBRATA.^ 319

Nenrooi System.

Situation.

External nerve. ]

plexus.

External to shell.

Function.

Internal nerve-
plexns.

Nerve-centre.

Over internal sur
face of shell
is in communica
tion with external
plexus.

sur- /
and I
ica- < I

Mainly round mouth.

Unites feet, spines, and
pedicellariae together, so
that they all move over
to a seat of irritation in
that plexus.

Brings feet, spines, and
pedicellarisQ into rela-
tion with co-ordinating
nerve-centre.

Presides over co-ordinated
action of spines and feet.
It gives rise to nerve-
trunks.

pentagonal nerve-ring sends off, in addition to the am-
balacral trunks, the nerve-cords to the intestine.

The physiological experiments of Fredericq (see p. 436 of
his paper, loc. cit,) are almost entirely in accordance with
those of Eomanes and Ewart.

Dr. H. Prouho* has investigated the nature of the external
nerve-plexus in Echinus acutus; and Dr. 0. Hamannf has found
EUid traced nerves in the various pedicellarisD of the JSchinidca,
GKnd he finds that from the main nerves branches are given off
bo sense organs and glandular sacs. All the pedicellariaa are
tactile organs, as the nerve-terminations indicate; the tri-
foliate ones seem to remove sand, Protozoa, &c. The large
pedicellarias serve to keep off layers of living bodies — €.[/.,.
wonnSj and therefore act as weapons, as well as for organs
of attachment when the animal is moving about. There i&^
no doubt that the latter function is the most important ; in
other words, the pedicellariaB aid locomotion.

In Echinus microtubercvlatu^ the gemmiform gland-bearing
pedicellarias hold fast sea-weeds, &c., when the animal is at

* Comptes Benduty tome 102, p. 444.

t JSiUung$hcrUhte Jenaitch, GeteU.filr Med, und Naturwiss, 1886.

320

PHYSIOLOGY OF THE INVERTEBRATA.

rest ; these help to hide it, and tlie secretion from the gUi
is therefore of the greatest service.

It will be noticed that the nervous system of the Echvf4
dermata is much more highly developed than that of tl
CcdeTUefrata.

The Triciioscolices.

According to De Quatrefages the nervous system of tlw!
Twrbdlanti consists of two ganglia sitnated in the anterior
end of the body, from which, in addition to other branches, % j
longitudinal nerve-cord extends baokwards on each side el
the body. As a general rule, the lateral trunks exhiUt-^
ganglionic masses, and from these ganglia nerves are ^v«i
off. These "may become approximated on the ventral sitie
of the body, thereby showing a tendency to the formatioa
of the double ganglionated chain characteristic of h^hciil

ee,> M

leetH

hibJtf

fivcn

side
matioa |
higiMjH

trochil I

In the Rotifera, the nervous system consists of a ti
ganglion situated on one side of the body near the trochJ
disc. This ganglion, sometimes divided into two portions,
gives off nervous filaments.

The nervous system of the Cesioidca consists of two
longitudinal lateral nerve-trunks, which run down the bodj
externally to the main canals of the excretory system. I"
the so-called head of the animal, where they are sWIen
(ganglia), they are united by a transverse commissure.

Dr. G. Joseph* has recently examined the nervoas BysWOJ
of the Cesioidca. The results arrived at are — (a) That the
two cerebral ganglia are in many cases (^Ta-nia tritHSverfii'*-
T. Toplmtoccra) connected, not by a single dorsal commisSDi^i
but by two, separated by a matrix and muscle-processes; {*)
that each cerebral ganglion is triple, consisting of a medi*"
and two smaller (dorsal and ventral) ganglia separated by
muscle -processes, as is best seen in Taenia crassi/x)llis ; (c) w»
in tlie bladder-worm, before evagination of the hooks, t^e
• SiologlirJies CenlralUatl, vol. 6, j

• 733- ^Hj

PHYSIOLOGY OF THE INVERTEBRATA, 321

central system exhibits six equatorial ganglionic masses,
which afterwards form a nerve-ring by the growth of bipolar
processes.

The Annelida.

The nervous system of the Gephyrea surrounds the oeso-
phagus, and from it a simple or ganglionated nerve-cord
proceeds backwards in the ventral median line. This nerve-
cord gives off branches. The nerve-ring surrounding the
oesophagus usually has a ganglionic mass. This mass is
connected with rudimentary eyes.

The nervous system of the Hirvdinea, and of Hirvdo in
particular, is highly developed. It consists of large supra-
oesophageal ganglia, which send off five pairs of nerves to the
five pairs of eyes. These ganglia are connected with a sub-
ossophageal ganglion by a circum-oesophageal nerve-ring.
They also communicate with the buccal gauglia situated
over and in front of the mouth. From the sub-oesophageal
ganglion two longitudinal, ventral, and ganglionated cords
proceed along the median line of the ventral aspect of the
body.

The ganglia of the two ventral longitudinal cords are
united together in pairs by transverse commissures. Each
pair of gauglia sends off, to the right and left, two nerves.
There are twenty-three pairs of ganglia on the ventral cords,
in addition to the sub-oesophageal ganglion, which is com-
posed of three or four pairs which have coalesced, and the
Caudal ganglion, which lies in the region of the posterior
aucker, and is composed of seven coalesced ganglia.

There is also a system of visceral nerves, consisting of a
^erve, which proceeds from the supra- oesophageal ganglia,
^jid runs above the ventral ganglionated nerve-chain, giving
off along its course branches to the caeca of the stomach.

The nervous system of the Oligochceta^ as represented by
JjumlyrictiSf consists of two cerebral ganglia situated on the
dorsal side of the pharynx in the third segment. These

332

PHYSIOLOGY OF THE hWERTEBRATA.

1 each of the CCTcbral

ganglia are connected by two nerves, which embrace
pharynx, with the Hub-cesophageal ganglia. The latter gsn{

are the first of the ventral g

ventral nerve has a double ganglionic enlargement in every

segment posterior to the third. A large nerve, which divide*

and sab-divides, proceeds forward froi

ganglia.

Four or five nerves run backward from the upper pert
each half of the circura-pharyngeal ring, and are distribol
in the muscular walls of the pharynx. Nerves are also givai
off from the lower portion of this ring to the muscles of the
foarth segment. Two pairs of nerves from each bilateral
ganglionic enlargement of the ventral cord, proceed tfl tie
viscera and muscles of each segment. Two nerves, one from
each side, pass off from the ventral nerve at a point hmtI
half-way between the double ganglionic masses, Thi
supply the posterior sides of the mesenteric septa.

When examined under high power the nerve-rods

lAi/mhriciis are seen to contain a large number of ^^^
cells along with the nerve-fibres. This is a characWn*
feature of ZHmtm'^s and Pcrifalux. In Hiruilo the nef^J

PHYSIOLOGY OF THE INVERTEBRATA, 323

cells are confined to the ganglia ; in this respect the nerves
of the leech are like those of Astacus and the spinal cord of
the VertebrcUa.

" The nervous system of the Polychceta usually consists of
a chain of ganglia— one pair for each somite— connected
together by longitudinal and transverse commissures, which
diverge between the cerebral ganglia and the succeeding
pair, to allow of the passckge of the oesophagus. The most
important differences presented by the nervous systems of
the Polychceta result from the varying length of the transverse
commissures. In VermUia, Serjnda, Sdbella, these commis-
sures are very long, so that two distinct and distant series
of ganglia appear to run through the body, while, in Nepthys^
the two series of ganglia are fused into a single cord
enlarged at intervals. .... In most Polychceta a very
extensive series of visceral nerves supplies the alimentary
canal."

The Nematoscolices.

In HiQ Nemaioidea the nervous system consists of a nerve-
ring surrounding the oesophagus. From this ring proceed
six nerves in an anterior, and two in a posterior direction.
Two of the anterior nerves proceed in the lateral lines — ^that
is, one in each — and four in the interspaces between the lateral
and median lines. The posterior nerves proceed to the tip
of the tail — one in the dorsal, and the other in the ventral
median line of the body. Near to the nerve-ring, in front
and behind it, arranged in dorsal, ventral, and lateral groups,
lie certain ganglia. These are respectively known as dorsal
or supra-cesophageal, ventral or sub-cesophageal, and lateral
ganglia. In addition to these, there are groups of ganglia
in the median and lateral lines, in the posterior part of the
body ; these are known as caudal ganglia.

In the Acantfiocephcda, represented by EchinorhyncuSy the
nervous system consists of a simple ganglion, which is situated

324 PHYSIOLOGY OF THE INVERTEtiRATA.

at, the base of the proboscis. Nerves are given off from tl
ganglion k> the proboscis, and through the retdnacla to tl

muscular wall of the bodj.

The Ch^tognatha.

This class contains only one genus— S'lgl/M. The nervot
system consists of a cerebral franglion (brain) on which the
eyes are placed, and a ventral gang^lion aituated near tlie
middle of the body. These two ganglia are united by
commissures. Near the mouth there are a pair of snb-
oesophagea! ganglia, which are uuitsd to each other, and to
the cerebral ganglion by commissures which embrace tteH
(esophagus. H

The Prototracheata. "

The nervous system of Peripalus consists of two large
Bupra-cesophageal ganglia, and two imperfectly-gangHonated,
widely -separated nerve-trunks, which proceed to the poakrior
part of the body. From these two trunks many later*!
nerves pass outwards and inwards; and, according to G robe,
the latter act as commisBures between the two nerve-tranluu

The Myiuapoda,

robe,* I
eot otH

The nervous system of these animals forms a ventral
with a pair of ganglionic enlargements for each Begment
the body. The anterior pair is united by commisfliir*^
with the cerebral ganglia. The ventral chain gives off O*
each side n number of lateral nerves. The nervous system *^
the Myriopoda has been compared to that of the larvte *^
the Iiutecla. The cerebral ganglia furnish nerves to certa^^^^*^
sense organs, such as the eyes.

The ganglia are constituted of cells, and the
fibres.

• Archiv/Ar Anatome, 1853.

PHYSIOLOGY OF THE INVERTEBRATA. . 32$

* The Insecta.

In these animals there is always a well- developed cerebral
ganglion or brain connected by nerve-trunks with a series of
ventral ganglia. One of the reasons of the great develop-
ment of the brain is assuredly the greater perfection and
the more importent office of the organs of the special senses
in the Insecta. According to Gegenbaur, many Dipteray
Hymenoptera, Lepidoptera, and the large-eyed LibelliUce, have
powerful cerebral ganglia. The cerebral ganglion or brain of
the ants, of bees, and of the spinning spiders (among the
Arachnida)^ is remarkable for its size, and even for its
conformation. Though Apis is a much smaller insect than
MelolorUha^ it possesses a cerebral ganglion more highly
developed, and relatively three times larger, if we take into
consideration the difference of size. The cerebral ganglion
of the ant is proportionally larger still. Besides, the surface
of these ganglia or brains is mammillated ; and there are
convolutions. According to M. Dujardin,* the brain of Apis
has a very singular form. *' We perceive a disc with stel-
lated strife surmounting like a hood the superior ganglion ;
and from certain experiments of M. Faivre,t the cerebral
ganglion has, like the cerebral hemispheres of the Vertebrates,
the property of being insensible to punctures and lacerations."

The nervous system of the Insecta (speaking in general
terms) consists of a cerebral ganglion connected to a gan-
glionated nerve-trunk or trunks, which passes backwards along
the ventral surface of the animal. Lateral nerves are given
off from these gangUa to the organs of sense, limbs, viscera,
Ac. Fig. 63 represents the nervous systems of various in-
sects ; and numbers 4 and 5 of the same figure represent the
nervous system of Pcriplaneta.

The nervous system of Pciiplancta consists of supra-
cesophageal ganglia (brain), which are connected by short,

* AnneUesdeB Sciences NaturetteSt 1850.
t Ibid, 4 s., tomes 8 et 9.

326 PHYSIOLOGY OF THE INVERTEBRATA.

thick commiasurea with the sub-CBsophageal ganglioo, which
oorreaponda to several pairs of ganglia fused together. This

snb-cesophngeal gaDglion leads into a rentr&l gangHonsCet^'
chain, which has three pairs of coalesced ganglia in tb^^
thoi-ax, and six pairs of closely connected and smaller ganglia

PHYSIOLOGY OF THE INVERTEBRATA. 337

in the abdomen. The brain gires o£F nerves to the Benea
oi^ans (eyes, anteniue), the sub-cesophageal ganglion snppliea
the month, and the other ganglia the rest of the body.
The visceral nervous system is
well developed in the Imeda,.
(Fig. 63. 4)-

In the Inweta, "the ner-
TOns ^^stem varies very much
in the extent to which its com-
pcment ganglia are united to-
gether. In most Ortfwptera
and Nearaptera, and in many
Coieoptera, the thoracic and
abdominal ganglia remain dis-
tinct and are onited by double
oommisenres as in Blaila {Peri-
planeta). In the Z^ndoptera,
the thoracic ganglia have coa-
lesced into two masses united
by double commiBSu res; whUe
in the abdomen there are five
ganglia, with single or partially separated commissural cords.
The concentration goes furthest in some Diptera and in the
Streptiptera, in which the thoracic and abdominal ganglia are
fased into a common mass." Iq many insects there are respira-
tory nerves, whose branches are distributed to the muscles of
the stigmata. The inner ends of these nerves form a plexus,
which is sitoated " over the interval between two of the
ganglia of the central nervous cord, and they are connected
by longitudinal cords with one another, and with these
ganglia."

The AitACHNiDA.

In the Artkroffostra, there is a bilobed cerebral ganglion
or brtun connected by commissures with the sub-cesophageal
ganglion : from this passes a nerve-trunk (consisting of two

338 PHYSIOLOGY OF THE INVERTEBRATA.

closely-applied commisBaral cords) to the three gangUi
sitnated ia the region of the twelfth to the fourteenth Bomitofl
of the body. The abdomen contaiDS four ganglia, from the
last of which leads two nerves terminating in the extremity
of the body. The cerebral ganglion, as in the InsectUy giTW
off nerveB to the eyes and other sense organs ; while brancbes
from the sub-assophageal ganglion are distributed to ihe
maxilliE and following somites.

The visceral nervous system ia well developed in thea]
animals.

In the Arancina, the nervous system is more concentrated
than in the last-mentioned order. It consists of cerebral and
Bub-cesophageal ganglia with branch-nerves, which procet- d to
the organs of sense and other parts of the body. In fart it
will be observed that in the Arnneina the ganglia are con-
centrated round the cesophagus. The same arraugenjeot
occurs in the Acannn.

The Chpstacea.

As a representative of the lower Cnistacea we describe the J
nervous system of Cyclcsihcria hidopi, belonging to thaJ
JPhytlaptxla. The nervous system of this animal has \
recently worked out by Dr. G, O. Sars," The i
ganglion or brain (see Fig. 1 1) is located within the pre-oral.
part of the head, posterior to the '■omiKtund eye and im-
mediately below the anterior part of the alimentary canal
It is rather large and of a somewhat irregular form, but very
difficult to examine minutely on account of its being to a
great extent concealed by the acape of the antennie. From
the upper part of this ganglion, and somewhat in front, the
strong optic nerves originate. These nerves are not united,
but quite separate throughout their whole lengt.h, each giving
rise, at the end, to a ganglion, lying at a short distai
posterior to the eye and sending off to this organ nomei

FideiukalM-Sclikabi J-'orluutdlimjef, ISS?.

distanoaS
Qomeroa^l

PHYSIOLOGY OF THE INVERTEBRATA. 329

fine nerve-fibres. The anterior comer of the cerebral ganglion
is exBerted to a narrow point, appliedagainst the posterior angle
of the ocellus. The antennnlar nerves, apparently originat-
ing from the posterior part of the cerebral ganglion, may
be easily traced as a delicate stem raDning along the axis of
the antennute and dividing at their extremity into a number
of nerve-fibres, which end with numerous ganglionic cells,
filling up the dilated terminal part of these organs at the base
of the sensory filaments. The nerves of the antennsa do not
seem to arise from the cerebral ganglion itself, but from the
strong commissures encompassing the oesophagus. The closer
structure of these nerves, and the mode by which they
innervate the several parts of the antennae, Dr. Sars has not
succeeded in tracing out.

The ventral nervous system, and especially its anterior
part, is very difficult to examine. By carefully dissecting
the trunk, and spreading it out in a ventral aspect after the
intestine had been removed. Dr. Sars has succeeded in partly
tracing out the double nerve-cord, which seems to agree in
structure precisely with that in other known PhyUopoda^
exhibiting the peculiar ladder-like appearance characteristic
of those animals.

In the Cirripediay " the nervous system consists of a pair
of cerebral ganglia situated in front of the oesophagus, and
connected by long commissures with the anterior of five pairs
of thoracic ganglia, whence nerves are given off to the limbs.
In the middle line, the cerebral ganglion gives off two slender
nerves, which run parallel with one another in front of the
stomach and enlarge into two ganglia, when they are con-
tinned to a double mass of pigment, representing the eyes.
!Prom the outer angles of the cerebral ganglion arise the large
serves, which proceed into the peduncle and supply the sac.
These api)ear to correspond with the antennary and frontal
serves of other Crmtacm; and Mr. Darwin describes an
extensive system of splanchnic nerves."*

* Huxley's Invertebrata, p. 295.

^^H

DO PHYSIOLOGY OF THE INVERTEBRATA. ^^

.■■'

Id some CnuMi'cra. soolr^B

Wli'?

as the Bhore-crab {Cartinu
nnniwi), there is a large cere-

•^\r\

^' iM/Al,

bral ganglion whicii give*

off nerves to the eyes and
antennie ; while the ventral
chain of ganglia (of oUier

isTV

■ Xy ■ ^^ — **

forms) is fnsed into onn

mass (Fig. 64). From tiw

^ ^^U '•■■

mas8 radint« the nerve-cords.

The nerve-cords connecting

f -P^ '-■■

the cerebral ganglion with

ill '

the nervous mass form the

t\ \ ^.

cesophageal ring or oolW.

"^ V \ <

There is in Oarcinv^t a degrw

of concentration of the gan-

, ^

glionic cells, greater, in eome

'' ^

resjiecta, than iii the Vertt-

^ .^ '

. <

■^

^ /

The nervous system of

__,

Astonu'i Jtu>--mtili» (Fig. 65.

L i

and see also Fig. 1 3) con-

•^

sists of thirteen ganglia

joined together by meaoBiif

i J

commissures. These gaogli*

,. ;

are divided as follows: OM

S>^

c ..'-.

cerebral, one sub-ceaoiAa-

'■Tr!?l>-'

geal, Eve thoracic, and sa

abdominal ganglia. Tlw

Fig. 65.
Nek^ous Systkm op Astacus.

cerebral ganglion or br«in

gives off nerves to the ey»;

J = aub-OBophttgeal ganglian.

to the auditory orgJins; W

nenw. ^= "bepatic" nerve.

the antennae ; to the caw

Ttw Momoch te lutned on one side to show

pace in front of the cer-

its nerves.

vical snture; to the green

^ """"l

PHYSIOLOGY OF THE INVERTEBRATA. 331

oesophageal ganglion. The latter nerves form the oesophageal
collar. The sab-oesophageal ganglion supplies the somites, from
the fourth to the ninth, and their appendages, and gives off
also delicate nerves to the oesophagus. The five anterior ab-
dominal ganglia supply the muscles and the appendages with
nerves ; while the sixth and last abdominal ganglion sends
nervous branches to the telson (tail). The sixth abdominal
ganglion also sends out two nerves, which unite into one
common trunk, and from which nerve-fibres are given off to
the intestine. The genital organs are supplied with nerves
from the third, fourth., and fifth thoracic ganglia.

^'The size of the ganglia is in direct ratio with the
development of the segments and their appendages, to which
they belong " (Von Siebold).

The physiology of the nerves of the Macrmira (under
stimulation) have been investigated by Drs. L. Fredericq and
6. Vandevelde.* They experimented upon the nerves of the
flexor muscles of the chelse of Homarus. The nerves of
Hbmarus when dissected out of the body very rapidly lose
their excitability. When a nerve is submitted to section the
excitability disappears progressively from the surface of the
section to the extremity of the periphery. Concerning
HomarvSy Fredericq and Vandevelde state : *' Ainsi, sur une
pince s6par6e du corps de I'animal, il arrive un moment oil
Texcitation ^lectrique du nerf pr^s de la surface de section ne
produit plus de contraction musculaire, alors que la meme
excitation appliqu6e sur un point plus rapprochc du muscle
y provoque de violentes secousses."

These experimenters have shown that the nerves of Hmnants
present the same distribution of electric tensions, and the
same negative variation, as those of the frog {Rana),

They have also ascertained the rate of transmission of
motor nervous influx in the nerve connected with the flexor
muscle of the dactylopodite. In these experiments they had
recourse to the graphic method employed by Helmholtz. By

* BvUetin9 de VAcadimie Raya'e de Belgiyucj 2 serie, t. 47 [1879].

PHYSIOLOGY Of THE INVERTEBRATA.

exciting tlie nerve at a point near the muscle, and noting the
moment of excitation and the moment of contraction, one b
able to aacertain the time which, elapses between the two
phenomena : the same experiment is then repeated on a point
of the nerve further from the muscle. The difference in the
time observed in these two experiments — that is to say, tie

FtG. 66.

— Appwatu
Ej[C[t.%t

^o^rN

THB NeHV

iieT

hTc»ZT '"

MOTM

= myograph carrying

lawo

fJoman,.

1 =

St; If allached

a ihtdMf

opodile.

spnng

which holds ihe <

acly [opodile.

a = t^rc:

* - anolhor pair of rlecttodes.

C =

P=b«tHJ*

E = regist

alion cylinder. BB

= [he two

coils.

.A =slei:l needles for dosiBi

Ihc drcuil

al each rcvol

lion of

the cyUnde

lapse of time between the second contraction and the first-
gives the time employed by the motor excitation to mn tht
distance between the two excited pfiints. Knowiog this
distance, one can calculate the rate of transmiasiou.

Fredericq and Vandevelde exposed the nerve (in a livii
lobster) which leads to the claw by two openings. A styl<

* The Btjle used was that of Dr. Marey , the diEtingnishod Profeww
Experimental Physiology in the College of France,

PHYSIOLOGY OF THE INVERTEBRATA. 333

s attached to the daob7lop3dLte of the chela (Fig. 66), and
firmly fixed, by the aid of bands, apon the horizontal plate
the myograph. The dactylopodite was held by means of a
rizontal elastic spring; the object being to keep it away
•m the other portion of the claw. A pair of platinum
ctrodes were applied upon each of the two portions of the
posed nerves. The four wires from these electrodes were
itened to the wires of the induction coil by means of a
nmutator, which allowed the changing of the electric shock
K> one or other of the pairs of electrodes, and of exciting
3 nerve in its nearest or furthest point from the muscle.
g. 66 shows the arrangement of the apparatus used in these
periments.

After ascertaining that the muscle reacts sufficiently to the
citation of the nerve, and that the point of the style marks
operly on the smoked paper of the registration cylinder,
■edericq and Vandevelde arranged the commutator in such
manner that the induction shock could not act upon the
}rve, and then allowed the cylinder to turn until it attained
} normal velocity. The point of the style traces upon the
^per a horizontal line, an absciss of which the turns are
produced exactly. The cylinder continuing its revolutions,
,6 commutator was so arranged as to excite the point b of
le nerve at the moment when the two points of the needles
hich close the circuit touch each other. The muscle con-
acted, and the style gave a graphic tracing (a curve) of the
mtraction. In a similar manner the commutator was arranged
> as to excite the point a ; this gave a second curve, situated
little in front of the first. The distance from the beginning
I the two curves compared to the length of the nerve enabled
le experimenters to determine the rate with which the
(citation was transmitted. They then marked on the cylinder
le part where the nerve was excited. For this purpose, the
>mmutator was closed in such a manner as to permit excita-
.on, when contact was made, between the two needles. At
[lis moment a contraction was produced, which inscribes itself

334 PHYSIOLOGY OF THE JNVERTEBRATA.

aa a simple line raised above the absciBS wfail&t the cyUnder
was at rest. In these experiments, it had been previouriy
ascertained that the cylinder had a unifonn rat© of roUtion
in inscribing by the Md of the "signal Marcel-Desprta " the
interruptions of an electric current produced by a timing-forlt
of 1 oo vibrations per second. It was also ascertained that th"
contact between the two steel points always took place at ti*
same moment of the rotation of the cylinder. Fig. 67 is •"
example of a grajjiiic tracing obtained with Homarus.

The nerve was excited at A. The curve CD represents the
curve inscribed by the muscle when the nerve was exdtedat
the point a (Fig. 66). The curve EF was obtmned by eici^
the nerve at h (Fig. 66). The distance between the n
points of the two curves represents about lOOth of a »

Fredericq and Vandevelde measured the distance oftbell
excited points of the nerve, putting the points of the OOB^MI
at each pair of electrodes, with those of the wire whidi were
turned to the side of the muscle. This distance = S6
millimetres. The rate of transmission waa conae(|DeDtJ}'
100 ■• 056 = 56 metres per second. The following raolta
were obtained in these experiments : —

A lobster (9) weighing 559 grammes (without blood); th«
right chela being used ; and the length of the nerre ""
59 mm.

A lobster ( 5 ) weighing 487 grammes (without blood); 1
left chela being used; and the length of the nerve '
56 mm.

B. iotorva] in bundredths uf a second . . t.t or 5.04 m,

1 PHYSIOLnOY OF Tf

The mean of these eight de
1 round figures 6 metres, per
The motor nervous excitati
finitely more slowneBR in the

In Fig. 67 the distance AC,

■ the curve CD from the p
DOths of a second. This di

le two periods: lat, the time
on produced at the point n to
tr as the termination of it in
f latent excitation of the niu

■ 'FlO. 67,— A GHAPiric. THACINIf V

f T,.».»,„„.» ,., V
= moment of exciution of nen-e,
the excitalion of ihe nerve al a {y\g.
Uined by Ihe excilation of ihe nerve at

etermined, among other thing
ufiices to obtain a graphic tr
ions by directly placing the
exor muscle of the dactyiopc
e I. sooths of a second, and t
second. There remained, th
eoond, which represented the
xcitatioo to travel from the p
nterior of the muscle. The ler
onld not be directly determi
ess than 500ths in these e.xpe
each 1000th- That gave a ve
he first hypothesis, and t,.ii r

IE INVERTEBRATA. 335

^rminations is 5-95 metres, or
econd.

3n is transmitted, then, with
lobster than in the frog or

which separates the beginning
oint A, corresponds to about
ration represents the sum of
which is lost from the excita-
run the length of the nerve as
he muscle ; and 3nd, the time
ele. Tlie latter is known and

OH Determtbikg the Rate oir
oTOR Excitation.

3). EK = curve of conlraclior. ob-
(Fig. 63). IHundiedlbsofaseeond.)

3, upon the same mnacle. It
icing of the muscular contrao-
exciting electrodes upon the
idito. This time was found to
at it did not exceed 300th8 of
•a, at least 5 - 3 = 300ths of a
necessary time for the motor
int T along the nerve to the
gth of this portion of the nerve
led ; but it was very probably
iments, and did not certainly
locityof 1.66 m. per second in
n. in the second. From these

336

PHYSIOLOGY OF THE INVERTEBRATA.

invoatigationB it is evident, that the rat© of t:

the motor nervoua influx in its passage from nerve to moBclfl

iiada in the last nervous ramifications considerable dela;.

The following couclusiouB have been arrived at by Fredericq
and Vandevelde : — -

(1) There appears to be a complete identity in the pro-
perties of the muBclea of Hoinarns and those of Bona.

(2) The motor nerves of Hoiiiimtn present, from a /lAyw-
logical jxruU of view, great points of resemblance to tbosed
Jicma. The moat charact(?ristic differenct- consists in the
slowneBB with which the motor excitation travela the leogti
of the motor nerves. In Homarus it is 6 metres, aod is
liana 27 metres per second. The slow rate of transniiaaioii
of the motor excitation proves in Homarus a conudenb!^
slackening in the muscular terminations of the motor neires.

The difference in the rate of transmission may be dae l"
the difference in the composition of the nervoua matter of Ih^
two animals. The following table represents the chemical com-
position" of the nerves of Hoviarus aia& ^Tiarespectdveiy:-'

X«H.

...

I-

AlbDminoids .

„.6.

...

ag.ao

j«.

Lecithine . . .

779

S.11

9.9a

♦90

CholeBtrine and hta

58.34

57-6?

47-13

CerebrinB

8.a6

8.03

y.78

>«

ether) ... J

4.10

4,36

3.50

Salts ....

0.90

0.9a

a47

a45

,<».«.

100 A)

MOM j

* Dr. A. B. Griffiths' aiuljMS.

PHYSIOLOGY OF THE INVERTEBRATA.

337

3 composition of the askes of the neirous matter in each
8 represented in the following table : —

lesia

oxide

phoric acid (combined) .
phone acid (free) .
tinric add

tine

llomanu.

3300
11.98
1.87
0.99
0.16
41.51
6.81
0.90
1.96
0.82

Bama,

100.00

36.24

ia87

1.30
a8[

0.21

40.32

7.92
a72

1.21

C.40

100.00

e first table gives the chemical composition of the ner-
matter in a dr^ state ; the following table gives the
osition of the nervous matter with its accompanying

r:-

nomaru$.

JSaittf.

70.21
29.79

66.42
3358

100.00

le last two tables represent the averages of six analyses
ch case.

338 PHYSIOLOGY OF THE INVERTEBRATA.

The difference in the composition of the nervoas matterfl
the two animals, may possibly account for the difiera
in the rates of transmission as obsen-ed by Fredericq i

Vandevelde.

The Poltzoa.

The nervous system of these animals is very simple, ai
consists of a ganglion, situated between tiie mouth and ll
anus (see Fig, 17), which gives off many nerve-fibres to ll
teiitacula and the ahmentary caiiaL

The Brachiopoda.

The uervons system of the CUstentfrata consists of a ganglio"
on the ventral side of the oral aperture. From t
proceeds a commiasore, which surrounds the cesophagus, 1
bears two small ganglia. "The latter probably aosvrer to tk
cerebral, the former to the podal, ganglia of the Lam<lliiraift
chiata. Immediately behind the peda! mass, from which '"O
large nerves to the dorsal or anterior lobe of the mantle
given off, are two elongated gangUa, connected by a coinnii*"
sure of their own, which possibly correspond with the poncM
splanchnic ganglia of the higher Molluscs. The nen-rs to ti
ventral lobe of the mantle, and those to the peduncle ft
from these ganglia."

The nervous system of the Tretenterata baa not been 4
thoroughly worked out as that of the Clistcnterata ; hot fl
Lingula, Sir Richard Owen, F,ll.S.,has shown that the viscBi*'
nerves are more developed than those of T'creinifu^o.wlii'^
belongs to the latter order, " Filaments to the muscles »re
also more distinct: a pair, which come off from the snt^
oesophageal gangUon, diverge as they pass backwards ftlo'ig
the visceral chamber, then converge to their insertion in 1^ ■
anterior muscles ; a second pair, also from the sub-oesophag
ganglia, run more parallel as they pass along the veiitl*
aspect of the anterior muscles to go to the posterior masc'**

ngliou
iiglioii I

to AM
Pratt's
■h t«» '
le are
ainmii- J

"°S

leen i^|

PHYSIOLOGY Of THE INVERTEBRATA. 339

IdnffuJa has alsa the paUIal and brnchial Bystems of nerves as
well developed as in Terebratuia."'

The Mollusca.

In the Mdhtaca there are uaually at least three ganglia with
radiating nerves — one in the head, one in the foot, and one
posterior and above the alimentary canal.

♦X'

Fig, 68.— Nervol-s Svstkms nf the

A = diagiam of nervous lyslem oiAnodonla. a — cerebral ganglia.
t = pedal ganglia, i — parielo-splanchnic ganglia.

B = neivoiB ayslem of Lim.ix. ,1 - cerebral ganglia. A = pedal
parido-aplanchnic gangba. d = nerves 10 fool.

C = nervous sysiem of Sefiii. li = pos-erior buccal ganglion.

b — anierior buccal ganglion. < — pedal ganglion, d = paiielo-
spUinctiDic ganglion, e = cerebral ganglion. / = optic nerve and
ganglion, g ^ splanchnic ganglion. h — ganglion stellalum.

As an example of the JximdHh-mirhidfa, we describe the
nervoQS system of Anoilonta. There are three pairs of
ganglia, (a) The cerebral ganglia, which are united by a com-
missnre, are situated at the sides of the mouth. They send

■ Owen's ComjMralift Aiialoiiit/ and Phi/iioloijj/ 0/ the Invertebrate JnimciU,
p. 492 (2Dd ed.).

34°

PHYSIOLOGY OF THE ISVERTEBRATA.

off nerves to the anterior pfjrtion of Ihe pallium; to the
anterior adductor muscle ; to the labia! palps, he. ; aud to the
brauchise. (6) The pedal ganglia are situated in the foot, or
in the corresponding part of the body when the foot is absent,
as is the case in some of the Lamdlihranehiata. These gaiiplia
are fused together on the median line of the body, and are
connected by commissures with the cerebral gau<j;lia. The
pedal ganglia send off nerves to the foot.(c) The parieto-
splanchnic or visceral ganglia lie on the ventral side of the
posterior adductor muscle. They are united with the cerebnl J
ganglia by commissures (Fig. 68 A), which traverse the org
of Bojauus (kidney). These ganglia send off nerves to tl
branchiie ; to the posterior and middle parts of the palliai
to the posterior adductor muscle ; to the heart ; to the siphotu
— as iji MijH ; and to the viscera generally.

In the Gasteropoila, represented by Helix, the nervos
system consists of the following parts : (n) The cerebral i
supra-cesophageal ganglia, lie on the dorsal side of the C
phaguB, and are joined close together by a transverse n
band (Fig. 68 B). Each ganglion sends off a commlssore \
the pedal ganglia, which are situated close together on t
ventral side of the ccsophagus. Commissures also join the
cerebral ganglia with the so-called pari eto-s plan chnic gangha
(a group of paired ganglia), which come into close relationsh'
with the pedal ganglia ; in fact, they are fused together wM
the latter ganglia. The cerebral ganglia supply nerves \
tiie eyes, tentacula, &c., aud also give ofl' a pair of nerves
oneon either side of the oesophagus — to the buccal ganglia
The pedal gauglia are closely united, (c) As already state
the paiieto-aplanchnic ganglia are fused with the pedal ganglia.
TTiey send off nerves to the nephridia, heart " lung," sexual
and olfactory organs, and pallium. ((/) The small paired
buccal ganglia ai'e .situated above and below the buccal mass.
These regulate the movements, &c., of the mouth ; and they
have been regarded by some investigators as sympatlietic in
fonctioD.

aneto-

of the I

irobnl^H

org>^

lliam;
[photu

sore ^^H
on tbV

PHYSIOLOGY OF THE INVERTEBRATA. 341

In the Cephalopoda^ the nervous system consists of a cerebral
or supra-cesophageal, pedal and parieto-splanchnic ganglia
situated around the oesophagus, and connected by commis-
sures. " In addition to these, buccal, visceral, branchial, and
pallial ganglia may be developed on the nerves which supply
the buccal mass, the alimentary canal, heart, branchias, and
mantle."

In the Dibranchiata (Fig. 68 C), the cerebral ganglia send
off nerves to the eyes, &c., and to the buccal ganglia ; in the
Tetrabranchiata, the same ganglia supply nerves to the eyes,
Ac., and to the buccal mass. The pedal ganglia, in the
Dibranchiata, supply the arms, funnel, and they are connected
with the auditory nerves. In the Tetrahranchiata^ the pedal
ganglia supply the branch iae and the funnel. In both sub-
orders of the Cephalopoda, the parieto-splanchnic ganglia
supply the branchia?, but in the Dibranchiata they also send
nerves to the pallium and sexual organs. In the last-men-
tioned sub-order, " each parieto-splanchnic ganglion gives off
a nerve, which runs along the shell-muscles to the anterior
wall of the mantle, and there enters a large ganglion — the
ganglion stellatum." The anterior and posterior buccal
ganglia give off nerves to the oesophagus and stomach. The
nervous system of the Cephalopoda is characterised by its
great concentration and high development.

Notwithstanding the apparent irregularity of its general
arrangements, the nervous system of the Mollusca is modelled
upon the same plan as that of the Arthropoda, In the
Molhcsca, we still find the oesophageal ring, giving off from
its central portion a ganglionic peripheral nervous system,
distributing itself to the various organs, but without sym-
metry, as, however, the general conformation of the body
demands. The cerebral or super-oesophageal ganglia are very
small in the LamellibraTichiata ; but are not exceptionally so,
as these animals have no head provided with sense-organs.

The cerebral ganglion is, however, very large in the
Cephalopoda, due to the highly developed sense-organs.

342 PHySIOLOGV OF THE IXVERTKBKATA.

Tlie cerfbral or supra-cesophageal ganglion of tlie MoBuxa
appears to have special functions. According to M. Vulpian,'
if this ganglion in ffcUr is removed, the animal aarvives the
operation four or five weeks, but remains completely motion-
less. On the other hand, the removal of the sub-cesophage^
ganglion kills the animal in twenty-four hours. Mechanial
or electrical stimulation of the supra-CEsophageal ganglion of
the Molbisca produces little or no effect ; but with the snb-
ojsophageal ganglion, hoth kinds of stimulation cause vigorous
muscular agitation. Electrical stimulation often causes the
heart to Stop, in the state of diastole. Exactly the same
phenomenon occurs when electrical stimulation is applied to
the pueumogastric nerves in the Vertrh-ata,\

These facts would seem to confirm the theory of the
Genuan school of evolutionists, who connect the geaealc^ of
the Vertchrata with the Mo/hmcti ; but this theory has hai
its day, and the latest embryologicai researches exphun (h*
origin of the Vertebrate brain and spinal cord as the outcome
of the nervous system of the Arlhropofin, The nervous
system of the acranial A'ertebratea can be considered as
coaleacent ganglionic nervous system. The central nei
system of Awj'/iiatii^ (one of the acranial Vertebrates) is ^^*,
spinal cord with a series of ganglionic enlargements, each o^^^
which corresponds with the origin of a pair of nerves. Ac::^^
enlargement, which is comparable to the central ganglion o"-
the Artkropoffa, tenninates (anteriorly) the spinal cord 0^^*^
the acranial Vertehmfn, It does not perceptibly differ froa-^*^
the others, but gives off five pairs of nerves, among whicfc^^"^
are the optic and auditory nerves. The great differenc^^"'^'^
between the Arlhropui/n and the VrrtrbruOi is the complete ^
absence in the latter of nn resophageal uen'ous ring; am
that the nerve-cord has a dorsal aapect in the Vfrttbmti

* Lefoni «ur la I'liyiioltujU Ginfrtde tt Gim/iaroe rfu tylimt Xi
pp. 757-761-

t From tbcso investigations it is dlfficnlt to decide whether the
or iticsub'ixaoiibageal g:ang1iou rcpreitents the brain id tbe MeUvtca.

PHYSIOLOGY OF THE INVERTEBRATA 343

whereas it is situated ventraliy in the Arthrapoda^ Never-
theless there is a certain amount of homology between the
spinal cord of the cranial and aci*anial Vertebrata on the one
hand, and the ganglionic chain of the Arthropoda on the
other. In both the Vertebrata and the higher Invertehrata^
there is a special nervous network, which supplies the
alimentary canal, the respiratory and urino-genital organs,
and the circulatory system. In both of these sub-kingdoms
this system has its origin, or at least its roots, in the great
nervous centres.

In concluding these remarks, it may be stated that on the
whole, every nervous system, whether Invertebrate or Verte-
brate, resolves itself into a number of cells, and into a number
of fibres, which connect the cells or terminate therein. The
parts of the system where the cells accumulate in great
number are the nervous centres. The parts are almost wholly
composed of fibres from the nervous cords, and if we look
at the animal kingdom as a whole, we see that where the
cellular centres are the more voluminous and the less
numerous, the higher the animal is in the zoological scale.
In fact, the mammal has been said to be '' a sort of summary
of the entire kingdom. In him are combined all the tissues,
all the apparatus scattered through the entire series : he has
a special nervous system, but he possesses, nevertheless, a
portion of the ganglionic system of the Invertebrates, and
in him, as in them, this ganglionic system is constituted
essentially of fibres," derived in the first instance from a
protoplasmic basis.

The Tunicata.

The nervous system of these animals consists of an
elongated cerebral ganglion situated on the dorsal side of the
pharynx. Nerves are given ofi* from this ganglion to the
entrance of the pharyngeal sac, &c. ; nerves are also sent out
laterally and posteriorly. In the Ascidian larva the nervous

344

PHYSIOLOGY OF THE INVERTEBRATA.

system is compoae<i of a cerebral ganglion, which has Rt fir^
the form of a cord containing a cavity. This ganglion is
constricted into three parts, and is connected with ganglii
in the tail. The first or anterior part; of this ganglion girra
off nerves to the margin of the pharyngeal apertnre. Th*
middle portion of this ganglion has on it the auditory vesicle,
the optic organ, and a stalked ciliated olfactorj' organ. The
optic and auditory organs degenerate just before the adoit
condition is reached. The third or posterior portion of the
ganglion is continued into a long nen-e, which at the base
of the tail forms a ganglionic enlargement. This ganglion
gives rise to a nervous cord, which passes into the tail, where
it forms a number of email ganglia. Just before the animal
reaches maturity, the tail aborts, the muscles and notochordal
sheath degenerate, and the notochordal axis contracts. The
nervous system and sense-organs also degenerate, and the
cavity in the nerve-cord and cerebral ganglion disappears.

In concluding Ihe chapter it may be stated that Prof. E.
Eay Laukester" states that "the structure and life-histotj
of the Ascidians may be best explained on the hypothecs
that they are instances of ilc^cjicrntion ; that they are the
modified descendents of animals of higher, that is, more
elaborate structure, and, in fact, are deffena-ate Vertdrrata,
standing in the same relation to fishes, frogs, and men, aa do
the barnacles to shrimps, crabs and lobsters. "f

* DegtneratioR, p. 41.

t For fnrther information relative to the above-Bobject see the p
Dr. A. Giard in the Archira dc Zoologir Erjiirimmlale, I. i (i873l;
tion Fran^iUr pour t'Avanttmait det Sdenea, t. 3 [I874): JieeueS
du It juillet 1S74; Urine ifm Scirma Kiilvre.Hn, scptembre 1
Complei Jtendut, 1874-5 1 »'"' also Dr. W. A. Hculman's paper* in I

CHAPTER XI.

THE ORGANS OF SPECIAL SENSE, ETC., IN THE INVERTEBRATA.

As we have already seen, all nerves have not the power of
transmitting sensations to the brain or its equivalent ; some,
on the contrary, are clearly nerves of motion, whether acted
on by will or excited by other means. Some nerves, as the
optic, transmit only the impressions received from colours— -
i.e.y due to the action of light ; to other stimulants this nerve
is insensible. The olfactory nerve is sensible to various
odours, but it is insensible to the action of light or sound.
To these modifications of the sensibility of nervous elements
are due the phenomena of special senses. The senses of
touch, taste, smell, hearing, and seeing, are so many distinct
faculties putting the animal kingdom in relation with the
various quaUties of the external world.

The apparatus or mechanism of the sensibility is not com-
posed only of the different parts of the nervous system, whose
use we have already alluded to ; for the sense-nerves do not
terminate freely in the exterior, so as to receive directly the
contact of the producing agents of sensations, but terminate
in various mechanisms destined to collect the excitation, and
to prepare it in such a way as to assure its action. These
mechanisms are the sense-organs, and it is essentially by the
intermedium of these organs that the sensations reach the
brain or its equivalent ; but it may be remarked that they are
not indisx)ensable for the exercise of all the special senses ;
the tactile sensibility may be called into play everjrwhere,
where nerves exist adapted to conduct the ordinary sensa-

346

PHYS20L0GV OF THE INVERTEBRATA.

tions, and it is only by tbu senses of tast«, smeU, beuing
nnd sight, that this intermediate organ between the ner
and the external world is a necessary condition.

We now proceed tx> describe the sense-organs in tb»^
principal divisions of the Inveriehrota.

The Protozoa,

As these organisms are destitute of auy true nervon*'
system, it would be consistent, on d priori grounds, to assume
that they have no special sense-organs. But would it be
consistent to assume that these lowly organisms do not digest.
respire, and excrete, because there are present no speciil
organs set apart for tlie functions of digestion, respiration,
and excretion ? Certainly not, and there is every reason lo
believe that one or more of the special senses are repreaenled
in the Frolozua.

Tactile sensibility is generally distributed over the whole
surface of the body; frequently, however, it is concentrsWJ
on processes and appendages of it. This is more or leas tnii'
in the whole animal kingdom. In the Protozoa, the whole
surface of the body is exceedingly sensitive ; but it maj be
stated that the protoplasmic expansions called pseudopod'*
have been regarded as fulfilling the function of org&iis "'
touch as well as of locomotion. In other forms {e.g., P"''"'
mifitim, see Fig. 3) the vibrating cilia are considered by
Dr. Stein to be organs of touch ; and the long rigid bristle
in Criiptochihm, according to M. Maupas, has a similar
function, its principal nse being ■' to advise the animal of tbf
approach of other Infiisiiria."

In touch, sensibility is brought into play by simp'*
shock, or contact of bodies: it is spoken of as the le*"
perfect of the senses, and is also the one, which offers the
least variety in the different animal classes, compared among
themselves.

Of all the sense-organs, the eye is the one which

PHYSIOLOGY OF THE INVERTEBRATA. 347

differentiated ; and a large number of the lowest organisms
possess an ocular spot, which is a differentiated organ having
the function of sight.

In the Protozoa^ this organ is chiefly found in the group of
Monads or Magdlatay and is generally coloured red. IClebs
has studied the structure of these ocular spots in the Euglenee.
When one of these organisms is treated with a solution of
sodium chloride (i to ico), the contractile vesicle, which is
in close proximity to the ocular spot, dilates enormously, and
consequently causes the same thing to occur in the ocular
spot itself. By this means Klebs observed that the spot *' is
a small discoid or triangular mass, of jagged and irregular
outline (see Fig. i); it is formed of two parts: for a base it
has a small mass of reticulated protoplasm, and in the meshes
of the protoplasm there are small drops of an oily substance
coloured red."

" What is the physiological significance of these spots ?
Ehrenberg considered them as eyes ; hence the name Euglena
(word for word, pretty eye), which he had given to a species
of the Flagdlata provided with ocular spots. This interpre-
tation had been questioned by all the authors of his time,
and especially by Dujardin." At the present day, however,
many distinguished French naturalists hold the same opinion
as Ehrenberg — viz., that the so-called ocular spots of the
Protozoa are true visual organs. According to M. Pouchet,
the ocular spot of Glenodiminn polypJiemus (one of the Pen-
dinece) has without doubt the function of an eye. It always
occupies a fixed and definite position in the cell, and it is
composed of two parts — a crystalline humour and a choroid.
" The crystalline humour is a strongly refractive, hyalin,
club-shaped body, rounded at its free end, which is always
directed forwards, while the other end is immersed in the
mass of pigment which represents the choroid. The latter is
clearly determined ; it forms a sort of hemispherical cap,
enveloping the posterior extremity of the crystalline humour.
In fact, the visual organ of this organism is composed of

348

PHYSIOLOGY OF THE l.WERTEBRATA.

exactly tlie same parts aa the eye of a Metazoon, with
exception, thi' absence of the nerve-element."

The ocular spots of other FlufjcUata had been previoc!
investigated by KUnstler, Claparede, and Lachman, and tbi
found crystalline humours and pigmented capsules (a chonndj
but what their true function was, they did not know, as
nerve-apparatus fitted to perceive the impressions received
was, in the least, demtmstrable in these organisms. On llie
other hand, certain French savants state that " the
existence of a pigment and of a crystalline humour amply
Boffices to characterize a visual organ. Aa to the nerve-
apparatus susceptible of perceiving impressions, it is re-
placed by the protoplasm, which, as is well known, is
tive to light." It has also been stated, by some observe)
that the red pigment in the ocular spots of the Troh
ejfhibits similar reactions to the pigment, which is present
the rods of the retina of the Virtthrnla, But it should
borne in mind that pigment is not indispensable for
sensation of light, because there are many eyes of complicated
structure from which pigment may be altogether absent.
Therefore the only reasons which those observers, who st«t6
that a visual organ is present in certain Prototoa, hare for
euch an assertion is, that the ocular spot has a definite
position, and it posse^es a crystalline humour. Are th«
facts sufficient to speak of it as an eye ? The Rev. W.
Dallinger, F.ll.S,, and Dr. J. Drysdale,' who examined tl
ocular spots in various Monads, failed to discover the fu&ctii
of these bodies after a most searching inquiry.

In concluding this account of the sense-organs in i
}'i-otozo<i^ it may be stated that the vesicles of Muller
iMivth's roa/rinn (one of the Ci(iata) have been considered
possessing an auditory function.

• T/t ilvttlhhj JlkroiOJiical J-'iri-/il, vol, 1

rve-

tWH

PHYSIOLOGY OF THE INVERTEBRATA. 349

The Porifera or Spongida.

In these animals the sense-organs are not farther differen-
tiated than those of the Protozoa.

The Ccelenterata.

The sense of touch in these animals is believed to be chiefly
located in the tentacula, which surround the mouth, but in
Hydra^ as well as in other forms, every cell is sensitive to
touch.

The small pits in connection with nerves, and provided
with an epithelial lining of hair-bearing sense cells, in the
Medusce, are regarded as the simplest olfactory organ. They
are situated round the margin of the bell ; in fact in all the
Medusce the sense-organs are marginal. The small pigmented
spots are undoubtedly eyes ; and according to some writers,
otolithic sacs or simple auditory organs are also situated on
the edge of the bell.

The rudimentary eyes of the Medusce are much better
developed than those which are supposed to exist in the
Protozoa ; for in certain species, nerves penetrate manifestly
into the capsule (Gegenbaur). But the exact function of the
ocular spots in these animals was not understood until
Dr. G. J. Eomanes, P.R.S.,* investigated their nature from
a physiological standpoint. His mode of investigating this
subject was to put two or three hundred Sarsice into a large
bell-jar, and then to completely shut out the daylight from
the room in which the jar was placed. By means of a dark
lantern and a concentrating lens, he cast a beam of light
through the water in which the Sarsice were swimming.
** From all parts of the bell-jar they crowded into the path of
the beam, and were most numerous at that side of the jar
which was nearest to the light. Indeed, close against the
glass they formed an almost solid mass, which followed the
light wherever it was moved. The individuals composing

* Philosophieal TransactionSf 1875, P* ^95 » tW., 1879, p. 189.

PHYSIOLOGY OF THE INYERTE/iRATA.

this mass daeKed themselves against the glass nearest tii*
light with a vigour and determination closely resembling the
behaviour of moths under similar circumstances. There caii
thus be no doubt alxjut tkirMn possessing a visual sense."

To prove that the ocular spots of these animals are really
eyes, Dr. Roniaiies experimented in a like manner with a
dozen vigorous Bpecimens ; nine of which had previously hid
their ocular spots removed, while three specimens were left
intact. The difference in the behaviour of the mutilated and
the immutilated individuals was very marked. The thre*
unmutilated individuals sought the light as before, while tli*'|
nine blind or mutilated individuals swam hither and thithflC;
without paying it any regard.

It was suggested by Professor L. Agae^, that it was tib*]
heat, or ultra-red rays of the spectrum, which was the red'
cause of the above phenomenon, but Dr. Romanes has shown
that when a heated piece of iron ("just ceasing to be red")
was placed against the bell-jar containing the apecimeua of
tinmiu, not one of the organisms approached the heated metal.
These investigations prove that in Siirnin the faculty of
appreciating luminous (but not heat) mys is present, sii^
that this faculty is lodged exclusively in the ocular spots.

Dr. llomaiies has also shown that the lithocy&ts of its
covered-eyed Mfi/iim.- resemble, in function, the marginal
bodies of the naked-eyed Medrntw — that is, they are niili-
mentary or incipient organs of vision. The lithocyets are
stimulated by the approach of a candle or the access of day-
light, but if the lithocyats are removed, the ai^rooch of a
luminous object pi-oduces no stimulating effect.

The ocular spots in the Artinozoa, and especially in,
Adinia iifHcmhryantlicinum, have been investigated by
Schneider, ItBttekeu, Duncan, and MacMonn, These
coloured bodies are situated in the oral disc onteide the
tentacula ; and they are diverticula of the body wall. Bfr
ueath the surface "lies a layer of strongly refractiDg
spherules, followed by another layer of no less strougly

PHYSIOLOGY OF THE INVERTEBRATA. 351

refracting cones. Subjacent to these, Professor P. M.
Duncan, P.R.S.,* finds ganglionic cells and nerve-plexuses.
It would seem, therefore, that these bodies are rudimentary
eyes."

The colouring matter of the blue ocular spot of the
above-mentioned species of Actinia has been spectroscopically
investigated by MacMunn,t and these investigations have led
him to believe that it is possible that this pigment is capable
of absorbing certain rays of light, so as to enable the animal
to distinguish light from darkness.

The Echinodermata.

The sense of touch is well developed in the EchiiwdcrmoUa^
and seems to have, its seat in the ambulacral feet, pedi-
cellarise, and tentacula situated in the neighbourhood of the
buccal orifice. Bomanes and Ewart state that ** all the
Echinodei'niata seek to escape from injury. Thus, for in-
stance, if a starfish or sea-urchin is advancing continuously
in one direction, and if it be pricked or cut in any part of an
excitable surface facing the direction of advance, the animal
immediately reverses that direction." There is no doubt that
the sense of touch is present in these animals.

The sense of smell also appears to be developed to a certain
extent in starfishes. If several of these animals (contained
in a tank) are advancing in the direction of a luminous
portion of the water,J they immediately retract their steps, if
a small quantity of bromine or sulphuretted hydrogen water
is gently poured into the luminous portion of the water.
This fact appears to support the idea of a sense of smell in
the Asteridea,

According to Ley dig § certain Echinodermata appear to be
provided with auditory vesicles, in which float powerfully

* Proceedings of Royal Society ^ 1873.

t Philosophical Tranaactiont^ 1885, pt. 2, p. 660.

X The water was illaminated by means of a small incandescent lamp.

§ Hiitologie Comparie^ p. 316.

35=

PHYSIOLOGY OF THE INVERTEBRATA.

refracting homogeneous granules. These vesicles i
nerves, anil sometimes even rest on the central ganglia <S
nervous system.

The eyea or ocalar spots in the Adcridta are five r
nnmber, and they are situnted at the end of each ray.
These organs are spheroidal, pedunculated, and pigmented
prominences ; being expansions of the ectoderm, and con-
tinuous with the ambulacral or radial nerve (see Fig. 6l).
Each eye contains a number of clear oval bodies surrounded
by a pigment. These are said to represent the crystalliiie
cones of a compound eye.

In the Echinidcn the five ocular spots are situated on a
similar number of small plates, which form the apex of each
ambulocral segment. The ocular along with the five genitai
plates surround the anus.

The true function o£ the ocnlar spots in the Ec/iintxirrt
have been ascertained by Drs. Komanea and Ewart.*
Asferi(fea and Hckinidca (but not the Ophivridea) cran
towards, and remain in, the light ; but when their ocnll
spots are removed they no longer do ao. On the other ban
if only one of the five ocular spots were left intact,
animal crawled towards the light as before. It may also bl
stated that when their ocular spots are left intact, thai
animals can distinguish light of very feeble intensity.

The Tkichoscolices.

In the Turbellarict the organs of touch are distribnted ov«
the whole surface of the body, but the cilia are the c
tactile organs. Some of these animals have auditory t
provided with otoliths; and most of them possess eye
Many Plaruiria- have first of all in the embryonic slat*
pigmented spots in the place where, at a later period, eya
with crystalline cones are developed.

In the Hoii/cra, the tactile organs are cutaneons, and liart

• Fkilotophkol TV

I, pt. 3, pp. 8s6. 873. 877.

PHYSIOLOGY OF THE INVERTEBRATA. J5S

the form of papillae or prominences covered with hairs, or of
tubular prolongations of the skin. In some of these animals
there is a sac filled with calcareous granules attached to the
ganglion. This sac is most likely an auditory organ.

One or more ocular spots are sometimes situated on the
ganglion in the Rotifera.

In some of the Trematoda, ocular spots have been observed,
but no other sense-organs.

The Annelida.

In these animals the sense-organs are variously distributed.
The organs of touch are cutaneous, and they have the form of
bristles (setae), &c., in connection with sensitive fibres.
According to Leydig, these tactile organs are sometimes, in
the Hirudinea^ grouped in large numbers at the bottom of
cup-shaped depressions. In Hirudo, there are about sixty of
the cup-shax)ed depressions in the head, and others in the
posterior part of the body. They are in connection with the
terminations of nerves given off to those in the head from the
supra-CBsophageal ganglia, and to those posteriorly situated,
from the caudal ganglion. These organs are also of an
olfactory function (Leydig).

In the Gephyrea rudimentary or incipient eyes are some-
times connected with the cerebral ganglion. Simple eyes
are usually present on the anterior segment in the Hinuiinea.
These are supplied by nerves from the supra-oosophageal
gang%.

Iri Hvnuio the eyes are situated on the dorsal surface of
the first three segments.

In Lumbricus (one of the Oligochmtd) no eyes or other
special sense-organs are present. Although devoid of sense-
organs, LuTribricus " possesses a generalised sensitiveness, due
to the plentiful distribution of nerve-fibres through the body,
and which, in many respects, takes the place of a series of
specialised organs, corresponding to the senses of touch, taste,

3S4 PHYSIOLOGY OF THE INVERTEBRATA.

Bight, hearing, and smell. Its sens itdven ess to touch and it^
dishke to suulight are well known ; and, though not possessed
of organs of sight or smell, it is able easily to find its way X^^
stores of food, and to retreat from sources of danger into ^
barrow " (Gibson).

la Ah\opt (one of the Pohfhn-la) the eyes are large aik^
well developed.

Aa already stated the visual organs in the Anrulida ae~*
usually situated in the anterior part of the body ; bat in "tlm-«
remarkable geiina Pol>fopht/niliiiits, De Quatrefages discoverec^.
besides the oi-dinary cephalic eyes, a double series c^f
additional visual organs, one pair being allotted to eac=li
somite. In JBraiwhioviina, eyes are situated at the ends «3«f
the branchial plumes. Ehrenberg has described two cauJ g^l
eyesj in Amphieorn, and De Quatrefages has shown th^^
aimilarly placed eyes exist iu three other species of I'dychtrt'^S,
two of which are closely alhed to Amphicora, while the oth^er
is au errant form, related to Lumbnutrcis. Auditory sat^s^
containing many otoliths, liave been observed upon ea^z^
side of the oesophageal ring in Arrnicola, and similar org&.rsi9
have been noticed in other Tiiiiieola ; but hithmto tb^^r
existence has not been certainly determined in the ErraiUi^at*
(Huxley).

The Nematoscolices.

In the AV!;i«(oi'(/r«, thepspilliB and hairs situated chiefly h
the region of the mouth are organs of touch.

In n on -parasitic Nematodes (e.g., Eiioplus) ptgmen'ted
ocular spots are present on the oesophageal nervous ring.

The CflJfiTOGSATHA.

The eyes in Saijitta are situated on the supra-aisophageil
or cerebral ganglion.

PHYSIOLOGY OF THE INVERTEBRATA. 3S5

The Myhiapoda,

Concerning the sense of touch in these animals, there are
on the antennae and other appendages, filiform prolongations
— these transmit the eflEects of mechanical pressure, &c., to
the nerves attached to these organs.

Although some species of the Myriapoda are blind, the
majority have eyes; and these organs are either simple or
com])ound eyes. Prof. H. Grenacher has recently investi-
gated the eyes in this Arthropod class. He distinguishes
those of (i) ScolopendHdcc, (2) Litlwhius^ (3) Jul'm, (4)
Glomeris^ and (5) Scutigerai all except the last are stemmata.
JScutiffera has compound eyes of a very anomalous type, in no
wise resembling those of the Tnseda and Cncstacea. The
eyes of the Cliilopoda are more polymorphic and more com-
plex than those of the Chilogiiatha (Diplopoda), Physiologi-
caUy, the simple eyes of at least some of the Myriapod<i must
be very unlike the ordinary stemmata of spiders or insects.
These are true eyes. In the Myriapoda^ on the other hand,
each stemma has its retinal elements, or their representatives
so disposed in regard to the axis of the cornea-lens, and there-
fore to the incident rays of light, that it seems very doubtful
whether such eyes can do more than distinguish between
degrees of light and darkness.

The sense of smell appears to be feebly developed in the
Myriapoda,

The Insecta.

" The sense of touch appears to be seated in the Insecta in
very different parts of the body. It is chiefly located in the
palpi of the mouth, which, for this purpose, are usually
terminated by a soft surface. The antennae also serve as tactile
organs, but in a very variable manner, according to their
forms, the degree of their development, and the habits of the
species. These organs receive, each, directly from the cerebral
ganglion, a nerve; these nerves perceive the slighteat dis-

3S6

PHYSIOLOGY OF THE INlERTEnHATA.

turbsDces occurring in ihe antennal integament..-;, which are
solid and often provided with haira and bristles. Among
those Inmda in which these organs are very long, filiform, and
movable in various directions, they serve, like the vibrtass ol
many Mi'inmali'i, to announce the presence of external bodiet
With very many other Insect", they are very movable, and
are distinctly nsed as tactile organs, like the fingers of thp
human hand. It is also by means of these organs that insecta
perceive the varion.s conditions of the atmosphera, especially
the temperature, aud thereby regulate their movement* and
actions. With those Irutfctn, where the parts of the month aw
modified into organs of suction, it is quite evident that the
extremity of the proboscis is the seat of a very delicate wn»
of touch. Also with those female insects having an ovipositor.
which is used to deposit their eggs in holes of various depth.
the ape.v of this organ must ba endowed with the same
power."*

The estremities of the limbs in many Iiisecta are al^ tadi^^
organs. Besides these special devices, the skin of the In-vdf
is sensitive to touch. In spite of the chitiitons covering, thi>^*
animals fee! strongly the contact of external objects at an-J
point of their own bodies. This is due to the eensitiveneK "
the underlying membrane.

The sense of taste is confined to the mouth and phaiyi^^-''
This sense is, as a general rule, connected with the tact-"S-^^
sensation of the buccal cavity, and also with the olfacU^^'J
sensatiou.

In the Iiisteta, as well as in other Arthrapodu, a sped- ""
sensory epithelium is present at the entrance to the bocc^:^^
cavity : this is stated to possess a gustatory function.

In the Inaecta the cuticular appendages of the antenute,
which the gangiionated extremities of ner\'es occur, are
sidered to be olfactory fibres. Dr. G. Hauserf has recrnl
e.-camined the olfactory organs of the //tserfa. In all

• Sfebold'H Analumij nftht In'fruhrata (American edition), p. 414.
t ZeiWhriflftir WwrnsehafltUhe ZotJegU, vol 34, p. 36;,

PHYSIOLOGY OF THE INVERTEBRATA. 357

Orthaptcray l}ij)tera, Zcpiclopteray Neuropteray ffymenopteray and
Coleoptera^ a strong nerve arising from the cerebral ganglion
passes into the antennae, and there is a sensory terminal
organ, formed by cells developed from the hypodermis, with
which the nerve-fibres are connected. The function of this
organ was ascertained by extirpating the antennae, and the
insects which tamed away from carbolic acid, turpentine, &c.,
before the antennae were cut off, now showed no repugnance
at all in the presence of these compounds. It was also found
that when the antennae were removed the insects did not rush
to food.

The author has entirely confirmed Hauser's investigations ;
and there is no doubt that in the antennae of these animals,
there resides the sense of olfaction ; but it should bQ borne in
mind that the antennae are also tactile organs — i.e., they have a
dual function.

The sense pf hearing is somewhat well developed in the
Iiiscctff* " The only organs which can safely be regarded as
auditory in insects, are those which occur in grasshoppers
(^Acriflida), crickets (AcJietida^, and locusts (Locmtidcc), and
which were first accurately described by Von Siebold. They
have since been studied by Leydig, Hensen, Banke, and Oscar
Schmidt, but it must be confessed that much obscurity still
hangs over their, minute structure. In the Acrididw, the
chitinous cuticula of the metathorax presents on each side,
above the articulation of the last pair of legs, a thin tympani-
form membranous space surrounded by a raised rim. On its
inner face, the cuticular layer of the tympaniform membrane
is produced into two processes, one of which is a slender stem
ending in a hollow triangular dilatation. A large tracheal
vesicle lies over the tympanic membrane, and between its
wall and the latter, a nerve derived from the metathoracic

* The weevils {Sitona crinita and Sitona lineata)^ which feed upon the
leaves of beans and peas, are very sensitive to sound, and if approached
they usually drop from the leaves to the ground. (See Dr. Grifliths* The
Diseases of Crops, p. 26.)

358

PHVSIOLOGY OF THE INXERTEBRATA.

ganglion, pftssee to the reglou occupied by the processes, and
there enlarges into a ganglion, the outer face of which, besel
with nnmerona glassy rods arranged side by side, is in contart
with the tympanifonii membrane. A nen^c anting from thf
ganglion passes along the groove to the ' stem,' and ends in
a ganglion in its dilatation. From this ganglion certain finp
filaments proceed. In the Ackttidir and Loc\tafiil<r, tie tilMff
of the fore-legs present similar tynipaniform membranes,
which are easily seen in the common cricket, but, in otler
forms, become bidden by the development over theni of folds
of the cuticle of the adjacent region of the limb. Twu
spacious tracheal sacs occupy the greater part of the cavity of
the tibia, and a large nerve ends in a ganglion in the remuD-
ing space. Upon this ganglion a aeries of peculiar short rod-
like bodies are set."

i'or a tolerably full r^sumt' concerning the anditoiy organ
in the Tiiscdn the reader is referred to Mr. A. H. Swinton'*
Insect Varifiy : lis Propagation nnd Dislyilmlion, pp. 230-
252.

As a general rule, the Inseda have a pair of compound evt*.
which are sessile and are situated upon the sides of the bi^fld.
The compound eyi- is literally an agglomeration of aimplf
eyes, having each a cornea, a vitreous humour of conical form,
a pigmented layer, and a nervous filament. In some inset*
a compound eye contains upwards of twenty-five thon^iand
these simple eyes. All the small cornea." are hexagonal,
unite together so as to fomi a kind of common cornea, wh<Ml
surface presents a vast number of facets. The retina of
such eyes has a hemispherical form, the convex surface beii^
directed outwards, and consists of large compound nerve-nidE,
and retiuulre, which are separated from each other by
men ted sheaths. Iti front of these rods are placed the stroii
refractile crystalline cones, and in front of these again
lens-shajjed corneal facets. The compound eye is encli
by a firm chitinous layer, which following the sheath of

)nii.
*<* I

hota

PHYSIOLOGY OF THE INVERTEBRATA, 3S9

entering optic nerve surrounds the soft parts, and reaches as
far as the cornea.*

Almost all the Insccta have a pair of these compound eyes;
but they are sometimes replaced by simple eyes, and at other
times both kinds are present. In a few cases there are
neither compound nor simple eyes ; among these are certain
species of Ftilium, that live under the bark of trees ; the
Nycteribiay which is parasitic on the skin of certain animals ;
the Anophthalmiis,^ which livt^s in dark caves; and the
Claviger, which dwells in the nests of antn. The larvaa of
the Diptei*a and Hymcnoptera^ and most of the apodal larvas
of the Coleoptera are also blind.

The second form of eye occurring in the Insecta is the simple
eye, ocellus, or stemma. It contains the following parts : —
sclerotica, cornea, lens, vitreous humour, and choroid ; and it
is of globular form. " But the lens appears to be always a
mere thickening of the cuticle, which constitutes the cornea,
and the so-called vitreous humour is partially or wholly made
up of crystalline cones, analogous to those which are found in
the compound eye. In this respect the ocellus of the insect
resembles the simple eye in the Arachnida and Cricstaceu"

The larv8D of the Lepidoptera^ Neuroptera, Coleoptera^ and
some Hymenoptera and Diptera have only ocelli. Two or three
of these ocelli remain, but with superadded compound eyes,
in the majority of the winged orders except the Coleoptera^ in
which only compound eyes are present in the perfect state.
Simple eyes are present in the following Iiisecta: — PediculicUe,
Cocddce, Poduridw, Nirmidw, and the larvae of the Phryganida:^
HeToerdbidije, Myi^neleonida:, and Raphididw,

The sense of sight must be keen in the Insecta^ but their
mode of vision is essentially diflFerent from that of the higher
Vertebrata. On this point, Professor C. Lloyd Morgan} says :
*' Remember their compound eyes, with mosaic vision, coarser

* Clans' Lehrbuch der Zootogie, t See Darwin's Origin of Species^ p. 1 1 1.

X Animal Life and Intdligence (1891).

360

PHYSIOLOGY OF THE INVERTEBRATA.

by far th&n our retinal vision, and their ocelli of problematic

valne, and the complete absence of muscoiar adjustments in
either one or the other. Can we conceive that, with orgaiu «
different, anything like a siinilar perceptual world cah be
elaborated in the ineect mind ? I, for one, cannot. Admitting,
therefore, that their perceptions may be fairly surmised to be
analogous, that their world is the result of constmction, I <io
not see how we can for one moment suppose that the percep-
tual world they construct can in any accurate sense be said to
resemble ours,"

" The sounds produced by insects are, in a great proportion
of cases, effected by the- friction of the hard parts of ths
integument one against the other .... Landoia, however,
found that the thorax of a bluebottle fly continued to bus
after the separation of the head, the wings, the legs, and
the abdomen. . . . The acoustic apparatus, in fact, lies in
the immediate neighbourhood of the tJioracic stigmata. . ■ ■
The vocal organ of the fly appears to be a modification of the
occluBor apparatus of the stigmata, just as the organ of V(nH
of mammals is a modification of the occlusorspparatusoftliaf
respiratory opening."

In ApU the voice organs are three-fold, the vibrating winf^,
the vibrating rings of the abdomen, and the true vocal apparatni
in the breathing aperture or spiracle ; the first two prodooe
the buzz ; while the hum — surly, cheerftd, or colloquial];
significant — is due to the vocal membrane. Some of the bee's
notes have been interpreted. " Huumm " is the cry of con-
tentment;" "wnh-wuh-wnb" glorifies the incessant acoonche-
ments of tlie queen ; " shu-u-u" is the frolic note of young
bees at play; "sBss"means the muster of a swami ; "brrr"
the slaughter or expulsion of the drones ; the " tu-tn-tu " of
newly-hatched young queens is answered by the " qna-qus-
qua " of the queens still imprisoned in their cells,

- * The poet ItjroD sajR \a Don Juan (c. \.

PHYSIOLOGY OF THE INVERTEBRATA. 361

The Arachnida.

The palpi are the principal seat of the sense of touch, being
in connection with nerves arising from the cerebral ganglion.
The feet are also very sensitive tactile organs.

The eyes are always simple, like the ocelli of the Tnsccta ;
and there are usually from two to twelve* in number. Audi-
tory organs have not been discovered in the Arachnida^ but
we have many proofs of the existence of this sense in these
animals, and it would even appear that some of them are
sensible " to the charms of music." The parasitic Acarina,
and allied groups, are entirely devoid of organs of vision.

The Crustacea.

The sense of touch is well developed in these animals.
Its principal seat is in the antennas, which also contain
nerves from the supra-cesophageal ganglion. Often the
mouth organs have one or more pairs of tactile appendages ;
and no doubt the limbs, especially the anterior ones, are also
the means of giving rise to tactile impressions.

In the lower Crustacea, Dr. G. 0. Sars has shown that the
principal seat of the sensation of touch is in the antennsB.
The antennulaB have no such function.

The olfactory organ is situated in the antennula?. In
'AstaciiSj this organ is situated in the delicate seta3 of the
endopodite of each antennule (Fig. 69, A) ; these set«e are
provided with nerves. A similar arrangement occurs in
many Crustacea besides the Dccapoda. If the antennulaB of
Antaeus are removed, the animal will approach a small cup
containing bromine placed at the bottom of the tank in
which the animal lives. On the other hand, if the antennulaB
are left intact, the animal will not approach the cup. Other
obnoxious liquids of high density give rise to similar results.

* Scarpionidoi (Von Siebold)

363

PHYSIOLOGY OF THE JNVERTEBRATA.

This proves that the sense of smell is developed in AsUmt
and that the olfactory organs are the antennulse.

Auditoiy organs have been observed in the higher
CrtisCaaa, especially in the Uccnpoda. In Asttttus (Rg.
69, D), there is an auditory sac lodged in the basal joint
of each antennnle. The upper face of the basal joint has »
small oval aperture, the outer lip of which is invested bj
hairs directed inwards. This aperture leads into a wide
delicate sac, which contains a fluid in which minute sandy
jiarticles (otoliths) are suspended. A ridge, formed of thsj

ilargnl, sliowing olfadary
g — wAaorj

■enw-

posterior and inferior wall of the sac, projects into its inteiin-
Each side of this ridge is covered with a series of del
setffl (auditory sette), which project into the 6nid.
auditory ner^'e, which enters the sacs, breaks up into
fibrils that are distributed to the setie. A fibril pi
through the base right up to the summit of each seta, whrrt
it terminates in a peculiar rod-like body. The sononrn!*
waves, transmitted through the water in which AMactu lii
to the fluid and sandy contents of the auditory sac, are
up by the delicate nerve-endings and conveyed through
auditory nerve to the brain or KU])ra-0Dsophageal gangli

et&lM
lion. ^H

PHYSIOLOGY OF THE INVERTEBRATA. 365

In Astaeics, HomaruSy and other Dempoda, it may be re-
marked that both the olfactory and auditory organs are
lodged in the antennulsD.

The eyes of the Crustacea are formed on a plan very
similar to those of the Insecta, Sometimes they are simple ;
bnt generally they are compound eyes, and in all the higher
Crustacea they are carried on movable peduncles, an arrange-
ment not met with in any of the other classes of the
Arthropoda,

"The Chripediay the Fenellina, and the Lernn'mlra alone
are without an organ of vision ; and even here this deficiency
occurs only during the last phases of their retrograde meta-
morphosis, when these animals remain fixed to foreign
bodies.* There is, moreover, in the other orders, here and
there a genus, which contains blind individuals : such is the
case with the females of certain parasitic Ifnipoda ; f and the
same remark applies to some subterranean Mymapodar %

The eyes of Astacus and other Dccapoda are two in number
— one seated at the extremity of each of the ophthalmic
peduncles, the cuticle of which is continuous with the
transparent cornea. The corneal membrane is divided into
numerous minute square facets, each of which corresponds

• The adult Cirripedia^ notwithstanding the absence of eyes, are very
sensitiTO to light (Von Siebold).

f BopyruSf Jone, Phri/xus (t.c., the 9).

Z PaiydesmuSt Cryptops^ Qeophilus, and Blanitilua, The blindness of
these and other animals is generally attributed to the effects of disuse.
Concerning the blind cave-crabs, Darwin in the Origin of J^teeies (p. 1 10)
says : " In some of the crabs the foot-stalk for the eye remains, though the
eye is gone. • • • • As it is difficult to imagine that eyes, though useless,
could be in any way injurious to animals living in darkness, their loss may
be attributed to disuse." On the other hand, Mr. W. P. Ball says : '* The
cave-crabs which have lost their disused eyes, but ttot tJte disw*ed eye-ntaJkn,
appear to illustrate the effects of natural selection rather than of disuse.
The loss of the exposed, sensitive, and worse-than-useless eye, would be a
decided gain, while the disused eye- stalk, being no particular detriment to
the crab, would be but slightly affected by natural selection, though open
to the cumulative effects of disuse." (See Ball's book : The Effects of Use
and IHswfef p. 17.)

364

PHYSIOLOGY OF THE INVERTEBRATA.

with the base of a crystalline cone. Each cone paeaeR
inwardly into a nerve-rod, and then thickens into a striswd
Bp in die-shaped body. The inner extremities of the striata!
Hpindlea become narrow again, and then pass into the c
neire (Pig. 70).

A = Eyeof^i^ifiii. B = Eye of //flmj.-uj,
CODES. c — nerve rods. d — sirinled bodies. t = oplic
/= lenlicular bodies, g - feneslrated membrane, k - lajfer noC |il«W* ^
in Ailaiui. k — pigment cells between cones. C = cornea o( /Ara/nte

There are certain species of crayfishes nkich are blinJ;
among these may be mpntioned Cawhnms 'Hioxiis (Faxon),
which lives in the caves of south-western Missoori, kA
Camharua ■ptUvckliix, the well-known species from the Mam-
moth Cave. Mr. G. H. Parker* has recently examined tde
question of degeneration of tliese organs. He states thkt

* BuUttin of the ituieum of Con^ntratirx Analomy al BarP^rd CU9*>

vol. 30 (tSgo).

PHYSIOLOGY OF THE INVERTEBRATA. . 365

not only has the finer structure of the retina been affected,
but the shape of the optic stalks has been altered. The
optic stalks are not only proportionally smaller than those of
crayfishes possessing functional eyes, but they have in these
two cases characteristically, different shapes. In crayfishes
with fully developed eyes, the stalk is terminated distally by
a hemispherical enlargement ; in the blind crayfishes it euds
as a blunt cone. In both forms of crayfishes the optic
ganglion and nerve were present, the latter terminating in
some way undiscoverable in the hypodermis of the retinal
region. In C. setosics this region is represented only by
undifferentiated hypodermis, composed of somewhat crowded
cells, while in C. pdluddus it has the form of a lenticular
thickening of the hypodermis, in which there exists multi-
nuclear granulated bodies ; these are shown to be degenerated
clusters of cone-cells.

The Mollusca.

The sense of touch, according to Gegenbaur, is chiefly
confined to certain cutaneous cells with setiform prolonga-
tions, disseminated where the body is not covered with hard
pieces. These cells are provided with nerves, which offer here
and there ganglionic expansions. In the Laindlihranchiata^
there are frequently tentacula around the branchial and anal
openings of the pallium, and the orifice of the siphon. These
and similar devices receive nerves from those of the pallium.
The tentacula and the ciliated labial palps are the tactile
organs of the Lamellibranchiata.

In the Gasteropoda, represented by Hdix^ all the parts of
the body (excepting the shell) are capable of feeling when
touched. The tentacula, the edges of the lips, and the lobes
of the pallium and foot, however, have the sense of touch
developed in a specially high degree.

In the Cepludopoda^ the sense of touch is well developed.
It is situated in the arms, the fringed labial membranes, and
in the whole of the cutaneous covering.

been .

366 I'HVSIOLOGY OF THE INVERTEBRATA. ■

In the Mdhisva- there appears to be special oi^ans of tuMi
in the form of a specific seiiEoiy epithelimn at tlie entnn^^

of the bnccal cavity. fl

In the C'p/iiilopoda, "the fleshy point of the tongue b
undoubtedly a gustatory organ. It is coiic<?aled in the
anterior angle of the lower jaw, and its roonded saiiace ii
covered with numerous soft Wllosities, which very probabl;
serve as gustatory papillae."

The olfactory organ of the Bi^nehiognxtiyropoiia has be*B
examined by Ur. J. W. Spengel.* He finds that in IWM_
Turbo, and Veniidus, the so-called "rudimentary gill,"
4Xilour gland of T. Williams, is an olfactory organ.
organ consists of a large mass of nervous matter, investel
& layer of epithelium, into which uerve-fibres distinctly
Spengel has also proved that the ciliated organs of fiegenl
in the Pkropodn have an olfactory function.

Dr. D. Sochaczewerf has also examined the olfactorj
orgaiiB in the Fidmogn.'itercpoda. In these animata, the
tentacula, the organ of Semper, and the pedal gland hire
each been considered to have the function of an olfactory
oi^n. Sochaczewer has tried the following experiment*'
(«) Having cut off the tentacula of JJrlUjjiniuttia,ihev/oaoi
was allowed to heal. The snailin were tlien placed on a fiW
jtlate, the edge of which was smeared with turpentine. Botli
the mutilated and uumntilated specimens turned away (rom
the edges. This shows that the tentacula are not the seat of
the olfactory organ, (i) The organ of Semper is amall Jo
Hciij; Ariori, and Limna-iis; but is well developed in Ztiftt.
Here it has the form of four or five glandular lobat© processesi
which are set at the sides of the mouth. This organ i>
supplied with four nerve-fibres. The two median are mi*
cular iu character, while the lateral branches are the propff
labiales, which give off, one on either side, a fine nerve-bnnoli
to the glandular branches of Semper's organ. The cells »

• ZeiUiJtTlfl far ir"i»«. ZooliMfit, »oL 35, p. 333.
t Jbid. p, 3a

PHYSIOLOGY OF THE INVERTEBRATA. 367

the constituent lobes resemble the glandular cells of the
salivary glands; in other words, this organ has not an olfactory
function, (c) The pedal or foot gland is looked upon by
Sochaczewer as an olfactory organ. It is well supplied with
nerves; but experiments are difficult to try in such an
organ.

The olfactory organs of the Ccplicdopoda are situated near
the eyes. They are either depressions or papillae of the
integument. The nerves which
supply these organs arise from
the optic ganglion of the oeso-
phageal nerve-ring.

The auditory organs (Fig. 71)
of the Zamellibranckiata con-
sist of a pair of vesicles or sacs.
These vesicles are filled with a
fluid (endolymph) containing
otoliths ; and they are attached
by short nerves to the pedal

ganglia. In the Mollusca generally, a delicate sensory epi-
thelium marks the percipient portion of the inner wall of the
auditory sac.

The auditory organs of the Gasteropoda^ as represented by
Helix^ are in pairs, close to and connected with the pedal
ganglia. Each auditory organ or otocyst consists of an in-
ternally ciliated vesicle or sac containing a fluid and otoliths ;
an auditory canal which may communicate with the exterior ;
and an auditory nerve from the cerebral ganglia.

A pair of auditory vesicles are always present in the
Pteropoda.

In the ]}ibranchiata^ the auditoiy organs are situated in
the cavities of the cephalic cartilage. The internal walls of
the auditory vesicles in the Octopoda are smooth ; but in the
Loligina they are raised into papillae.

In the Tetrairanchiata, represented by Nautilus, the
auditory organs are attached to the pedal ganglia, and are

I'kj. 71.

Tin: Auditory Organ ok Cyclas

a — capsule or sac.
epithelial cells. <• -

b = ciliated
= otolith.

368

PHYSIOLOGY OF THE INVERTEBRATA.

not situated in the cranial cartilage. In both orders, I
auditory nerve gives rise to nerve-filaments within the saojl
and in the Dihranrihiain there is a angle, irregalar, whiMl
otolith of a cryBtalline texture (CaCO,). On the other I
the auditory sac of the Tetrabranchutta contains nunjl
otoliths.*

In the Molhisca, organs of sight are met with in variutu 1
degrees of development. They are absent in tlie fited j
Molli'.scn. Certain of ihese, which in the state of mobil''
larvse had eyes, lose them bj
degeneration when they have
becomeimmobile. Certainsp^
cies of the lAimtdihranehuiit J
have as eyes sometimes otiju
pigmented spots, and some- "
times brilliant organs, dissemi-
nated on the edge of thf
pallium.

In Prdai, there are a larjir
Qunibei' of simple emersM-
green coloured eyes sittiat*^
round the edge of the pallinni'
Each eye (Fig. 72) consists of a cornea, lens, sclerottea,
retina, choroid, and vitreous humour. The eye is pedanco- .
lated, and it has a double optic nerve.

The table on p. 369 gives the colour, &c., of the eyes ^
various Latneliibranchiaiu,

The Scajihopoda and Polyplatophora- have no eyes.
In the FulTnogastcropoda ie.g., Helix) there are a pair (*
simple eyes situated on the summits of the large tentacQlw
The eye of Helix consists of the following pails : scleniti
choroid, lens, cornea, vitreous humour, and an optic i
which expands into an outer and inner retina, The eyii ^
these animals is much more highly developed than the ampl^

' Dr. J. D. Macdonalii in Proc. Roy. Soe.,

■85s- ^H

PHYSIOLOGY OF THE INVERTEBRATA. 369

of other Invertebrata. Highly-developed simple eyes
bJso present in the JBraTichiogasteropoda,

COLOVS.

BllCAKKB.

iUu .

yellowish-brown

non-pednncnlated.

ten .

1 green

pedunculated.

tUf .

yellowiah-brown

non-peduncnlated.

etra

reddish-blue

non-pedunculated.

:a .

reddish-brown

non-peduncolated.

sn .

yellowish-brown

non-pedunculated.

na ,

brownish-yellow

short peduncles.

iuneidus

reddish-brown

non-pedunculated.

Una

reddish-yellow

pedunculated.

omia

brown

non-pedunculated .

na .

green

pedunculated.

mdyluM

green

pedunculated.

eattda

green

pedunculated.

■rea .

brown

short peduncles.

a the Ptcropoda the visual organ is either absent or it is
mentary.

1 the Cephalopoda the organs of vision are large and
ily developed ; in fact, the eyes of the typical Dibranchiate
kalopodu are more highly organised than those of any
T Invertebrate animal. A pair of eyes are situated in the
tal cavities at the sides of the head in all the Dibranchiata.
eye (Fig. 73) is more or less of globular form and con-
\ of the following parts : cornea, tapetum, ciliary body,
talline lens, vitreous humour, sclerotica, retina, white
idular body, and the optic ganglion* and nerve.

* A great part of the eyeball is occupied by the optic ganglion.

2 A

370

PHYSIOLOGY OF THE INVEflTEBRATA.

In the Tci-rabriinfhiaia, as represented by Xnulilu* and &•
allies, the eye has no cornea, lens or vitreoaB hiUDOor. Itu
a mere cup or cavity lined by the retina.

T\a. 73.— KVE Of Skpia.
'1 = Btilerior chamber, r = cor
'' — sclErotica. g — lapetnin.

t — while glandular body,
rs Ot relina. f — opiic nerve.

i^/ter GEGENBAUTt.)

d = dliaty bodjr. /
= cephalic canlbi^.
- pigment layer. d =

In OnychoteutMs, OntmnstrepJus, and allied genen, H*
crystalline lens is exposed to the aea water ; this is doe it'
the entire absence of the cornea.

The eye of the Dihrnnekiota has been stated to resembl'
the Vertebrate eye, but this resemblance is merely superfi<i»l-
In fact, " the rods and cones of the Vertebrate eye eiactlT
correspond with the crystalline cones, &c., of the Arthrop'"
eye ; and the reversal o£ the ends, which are turned towards
the light in the Verlehynta, ia a necessary result of the eitr*-
ordinary change of position which the retinal surface nnd*-
goes in them." The aljove is an additional fact substantia

uitiatil|^H

PHYSIOLOGY OF THE INVERTEBRATA, 371

the theory, that the Vertebrata have been developed from the
Arthropoda rather than from the Molhisca. (See Chapter X.).
In this chapter we have seen that many of the lower
animals have tolerably well-developed organs of sense, and
as such organs are the means of awakening conscionsness, it
is reasonable to conclude that, on the whole, every nervous
system, however little developed, in the Invcrtebrata as well
as the Vertebrata^ may be traced to a conscious cellular part,
in continuous relation with two nervous systems, the one
afferent, through which sensory excitation is conveyed, the
other efferent, by which motor incitation is transmitted. The
mode of action of such a mechanism is evidently reflex action,
and, in fact, there is not a central nervous act, from the
Protozoa to the highest Vertebrata, which cannot be traced to
reflex nervous acts. First of all, the reflex action is absolutely
unconscious ; but in a later phase the nervous cell becomes
conscious of vibration of its molecules; it experiences the
sensations of touch, t^ste, smell, &c., more or less varied ac-
cording as the organ or organs are more or less differentiated.
At the same time it has impressions of pain, but in the lower
animals these impressions are only momentary — there is no
memory. Later still, however, this faculty becomes mani-
fested ; which is followed by the co-ordination of impressions,
sensations, &c., in other words — understanding, intelligence,
or reason, comes into play. But behind all this labyrinth of
psychical phenomena there are simply reflex acts, transformed
sensations and impressions. It has often been stated that
«nimal " intelligence " is merely due to instinct and not to
reason; that instinctive actions are not the result of ex-
perience or of previously acquired knowledge through the
senses, whilst those of reason can be readily traced to these
sources. Many acts of the Insccta and the Arachnida, for
example, such as slave-making, cell-making, web-making, &c.,
are described as due to instinct ; but there are many actions
among these Invertebrates which appear to come under
the head of reason. Among these may be mentioned the

372 PHYSIOLOGY OF THE INVEKTEBRATA. ■

following : ((() Certain moths formerly entered the hires of tie
working-bee, and thereby caused great damage to the ootiib,
&c. To prevent this nuisance the bee buiit a barrier, whicli
now prevents the entrance o£ the larger intrnders, yet at the
same time allows the entrance of the rightful owner. (6) Oa
the authority of un American naturalist, a pastrycook in
Chicago found his shop invaded by a colony of ants, wlii>
feasted nightly on the delicacies deposited on a certain shelf-
After cudgelling his brains for some time in order to discover
a plan for stopping the depredations of the active insects, he
resolved to lay a streak of treacle around the tray coDtatnb^
the coveted food. In due time the ants came forth in their
hundreds, and were led towards the feast by their cbiei On
reaching the line scouts were then sent out to survey, and
eventually " the word of command "' was passed around, and
instantly the main body of the ants made for a part of the
wall, where the plaster had been broken by a nail. Here
each snatched up a tiny piece of mortar and returned to the
spot indicated, where their burdens were deposited upon the
molasses. By this uieans, and after an infinite amouot of
labour, a bridge was formed, and the triuinphant army
marched forward to partake of the fruits of victory, the pwtrj*
cook meanwhile standing by filled with wonder, (c) The
dens or burrows of the trap-door spiders having been entered
by large predacious insects, these spiders constructed smaller
lateral burrows, provided with trap-doors, into which they
can now retreat in case the dens are forcibly entered. I"
this way these spiders protect themselves agmnst eneiHie*"
(</) The modes of building webs across various streants; the
strengtliening of webs by buttn-ss-like dericea, when ih^J
are constructed in gorge-like and windy situations: die»'
facts, combined with the power of the spider to adapt i'*^
to every possible circumstance, seem to point out that "^^
spider (as well as many other Invertebrates) is noi guided
merely by " blind instinct," but by that which is the eqiUTS-

PHYSIOLOGY OF THE INVERTEBRATA, 373

lent of mind, and which is capable of developing with every
generation— i.e., according to the Darwinian law.

But it is not our intention to go folly into the subject of
animal intelligence as displayed in various groups of the
InvertehrcUa ; such information the reader will obtain by con-
sulting special treatises devoted to this fascinating subject/.*

* yioT^v^s AmmaL Life and InteUIgrnce ; Romanes' -4 7i/maZ Intelligence;
and Lnbbock On the Senses, Instincts, and Intelligence of Animals, with special
reference to Insects,

CHAPTER XU.

MOVEMENTS AND LOCOMOTION IK THE Uf\TJtTElJK4T4.

In tills chapter we give ac account of locomotion and otbsrfl
movementa in the Inrertfbi-ata,

There ia scarcely any siieciea in the animal kingdom, wbidiS
is not more or less endowed with the power of movement CpI
motility ; but it is not essentially a property inherent i
organised matter ; for many histological elements are destitute
of it, and when an animal is only dLfrerentiat«d in a smtll
degri'e, motility is the attribute and the function of a spectal
tissue, at least in its most perfect mode.

In the lowest animals, where there is no diiferentistioa
of parts, the whole body is constituted of a substance wtiidi
is contractile and which changes its form perpetually —
emitting and retracting pseu doped ia unceasingly. The
pseudopodia are the first organs of motion ; but ihey i
simply expansions of tJie substance of the body — viz.,
sarcode. The first effort of differentiation appears to be t]
formation of cilia and flagella. In this case these expaosioiu
are no longer transitory ; for they have a fixed and definite
form. They are persistent organs, constituting the principal
organs of locomotion in the Iv/imn-iT. As we ascend in tlttj
zoological scale muscles become differentiated ; and by thtl
alternate shortening and lengthening of these muscles, niO?»" J
ments of the body are brought about. Muscles are preeeot
in all but the simplest animals — i.e., in iJl animals higher
than the Protozoa and Pori/era.

! UQH

u
te
al

PHYSIOLOGY OF THE INVERTEBRATA. 37 S

The Protozoa.

In these animals a distinct muscular tissue has not beeu
demonstrated, but the sarcode of their bodies is contractile.
It may be mentioned, however, that the contractile stalk or
pedancle of VoHicella contains a differentiated, longitudinal
muscular fibre, which is capable of contracting so as to give
the stalk the form of a spiral.

The organs of locomotion in the Protozoa are the pseudo-
podia, fiagella, and cilia.

In the Avueha it is by means of pseudopodia that the
animal moves ; ** it emits them in the direction in which it is
going, then it retracts them, while other parts of the mass
are in their turn elongated. The whole body moves by
creeping. This organism in moving has the aspect of a
drop of oil moving along. To ex|Dlain the mechanism of this
movement, it must be supposed that the extended pseudo-
podium seizes some point of support with its free end, then,
in contracting, draws the entire mass of the body up to this.*'

According to M. Rouget the retraction of the pseudopodia
is the analogue of muscular rigidity, the emission of these
organs being due to internal pressure ; and that the hyaline
substance or the pseudopodia is a kind of hernia of the
ectosarc, " resulting from a diminution of the elastic resistance
at the point where each pseudopodium appears, with an
increase of elasticity in those parts of the ectosarc where
pseudopodia are not produced. When the elastic tension of
these parts diminishes, and returns to its original state the
pseudopodium re-enters into the mass." M. Rouget further
states that in Amceba tenicola, the most external portion of
the ectosarc shows '* striaD of a granular appearance which
may be identical with the striae or contractile fibrils of the
ectosarc of the ciliated Infusoria — Stcntor, Spirostomuiriy
Paramosdum, &c."

The Gregariim moves in a worm-like, gliding, fashion, but

376

PHYSIOLOGY OF THE INVERTEBRATA.

very slowly. This movement, which only occurs occaaotu%,
18 due to the contractile nature of its bodj.

The Flagellate Infusoria are provided with Sagella ; the»
are appendages which have a daal function, being organs of
locomotion as well as of prehension. " The Protonxm.
its llagellum executes the most varied movements,
first in one direction, then in another, and in different
planes ; sometimes the animal curves about entirely ; bat
most frequently, when it uses the flagellum as an organ of
prehension, it extends the whole length of the organ ; the
basal part remaining completely immovable and ri^d, while
the free end alone executes movements destined to drive food
to the mouth, which is generally situated at the base of the
flf^ellum," In certain genera of the Ftiujeliata (among these
the Pa'tdinett), there are organisms which have the power of
throwing off their Hagella before entering into a doi
state ; and they can as readily regenerate these im]
organs. (BiitschJi.)

"In Aiithophi/xa, there are two motor organs — ^tbe ondi
stout and comparatively stiff flagellnm, which mmeB
occasional jerks, and the other a very delicate eilium, wl
is in constant vibratory moHon."

Drs, Dallinger and Drysdale* (who have Be tboronghly
worked out the life-history of several species of Monads or
Flagdlala) state that in some of these organisos there is a
peculiar structure, which is intimately connected with the
bases of the flagella, this ap))ear3 to be muscular and is the
probable cause of movemeut in the llagella. Thej also state,
" that in every instance where there was only one fiaf^llum,
or where the two arise and move from the same ]ioint, their
insertion in the body-sarcode was always in from; so that
the flagellum or llagella liad a pulling motion like that of the
paddle of an ancient coracle ; never the pushing mdion frOBi
the stern like the sculling or rowing of a modem bcBL

' JfonlAJjf ifieroteoiiiaJ Jourittil, 1S74. p. 364 : uod 1875, p. 19a.

]

PHYSIOLOGY OF THE INVERTEBRATA,

yjr

evidently arises from the complete flexibility of the flagella,
by which a propelling motion plainly could not be ap-
plied."

The diameter of the flagellum of some forms is only
O.OOCXX)488526 or the -^jTrnns^ ^^ *^ inch.*

In the Ciliata, the outer surface of the body is provided
with vibratile cilia. These are organs of locomotion, touch,
and prehension; and they may also aid in the function
of respiration by causing a renewal of the water, which
furnishes the necessary air for the function of respiration.

The cilia of these animals are homogeneous structures con-
tinuous with the ectosarc.

The CUiata are divided as follows —

Cilia.

Hcilatricha

Heterotricha .

Hypotrtcha .

Peritriclia

( They are of eqaal length and distributed

( aU over the body.

[ They are of nneqnal length, but cover

( the whole surface of the body.

( They are situated only on the ventral

side of the body.
They form a zone round the anterior

part of the body.

As already stated certain Infusoria have a portion of the
protoplasm differentiated, so as to suggest a body comparable
to the muscular fibres of the higher animals. This filament,
or myophane, occurs in the peduncle of the Vorticellce ; and it
ifl by this means that the stalk or peduncle is capable of
forming a spiral, when the animal is disturbed.

• See the paper by the Rev. W. H. Dallinger, F.RS., in the Tramactiotut
of the Boyal Microsccpi^ Society , 1878, p. 174.

PHYSIOLOGY OF THE INVERTEBRATA.

The Porifera or Sposgida.

Movements Id these ammals are caaaed b^ the coni
materiai of the body-substance and of the flagella ; the
being uaed to aid respiration, &c. The embryos of cert«n
Porifcm are richly ciliated, and tliereby become frfe-Bwimming
larval.

ThH CaiLENTERATA.

The iHovenienla of Hydva are performed partly by true
muscular fibres, and partly also by the contractionH of the
body-wall. The tentacula are used for locomotion as well as
for prehension. In the Actlaia; locomotion ia brought about
by the contractions of the disc of the foot.

Dr. G. J. Romanes * has made a thorough examinfttioa ttf
the locomotor system of the Mcdum-, from the standpoint of
experimental physiology. As these researches would fill a
volume in themselves, we must refer the reader desirous of
information on the subject to the original memoirs mentioned
in the foot-note. However, ''it is known to every one that
the Mcduxcv are naturally locomotive animals, the variou
species swimming more or less rapidly by means of
alternate contraction and dilatation of the entire swimnii
organ. It niay not be bo generally known that
swimming-movements, although ordinarily rhythmical, are,
any rate in the case of some species, to a limitecl e]
voluntary — using the latter term in the same sense asitii
applicable to invertebrated animals in general. For instancy,
if StnviaoT Aurelia, &c., bo geiUl;/ irritated, the swimming-
motions immediately become accelerated, and the acceleration
persists for some time after the irritation has been withdrawn:
but to secure this result, the irritation must not be of snch a
character as an inanimate object might supply. Again,
individuals belonging to some discophorous species of tht

• See Phlltuaphi'-'il Tr/inioctioa
^659; 1879. p. 161.

nf lie- Sogal Socittg, 1S75, p, a6g ;

PHYSIOLOGY OF THE INVERTEBRATA^ 379

naked-eyed Medn^cc exhibit peculiar movements on being
alarmed ; but I am not sure whether these are, as is most
probable, purely involuntary, or performed with the view of
affording protection to the more vital parts of the animal.
Possibly the object may be to decrease the buoyancy of the
nectocalyz, and so escape from the source of injury by sinking
in the water. At any rate, these ]>eculiar movements consist
of a sudden folding together of the entire nectocalyx, con-
sequent on an abnormally strong contraction of the swimming-
muscles; and this contraction, besides being of unusual
strength, is also of unusual duration. Thus the last idea of
this movement will perhaps be gained by regarding it as a
sort of spasm. The time during which this spasmodic con-
traction lasts is pretty uniform in different individuals of the
same species ; but it varies in different species from three to
six seconds or more. In all cases the disappearance of the
spasm is comparatively gradual, the nectocalyx re-expanding
in a slow and graceful manner, instead of with the rapid
motion characteristic of ordinary swimming. These move-
ments only occur when the animal is being injured, or
threatened with injury." (Romanes.)

Romanes has shown that the lithocysts are the exclusive
seats of spontaneity, so far as the so-called " primary move-
ments " are concerned ; aud he has failed to detect the slightest
evidence of spontaneity on the part of the contractile zones, as
asserted by Dr. Eimer.

The tentacula of the Medviio- are prehensile organs capable
of seizing upon and destroying animals of far more complicated
structure than themselves.

The ECUINODEKMATA.

In these animals the muscular system is well developed ;
its fibres are flat and without transverse stria).

The natural movements of the Ednnoihrmata have been

38o PHVSIOLOGY OF THE INVERTEBRATA.

studied by Drs. Romanes and Ewart;" and tbey have shown
that the ambulacra! system is instrumental in the locomotioa
of all these animals, except the Ophiurvha.
- The Astei-Ulcn. — (ic) The common starBsh {Urai^i-r ruhfn^)
crawls upon a flat horizontal surface at the rate of two inches
per minute. " The animal usually crawls in a detertninate
direction, and, while crawling, the ambulacral feet at the end
of each ray are protruded forwards as feelers ; this is parti-
cularly the case with the terminal feet on the ray, or r»ya,
facing the direction of advance. When in the course of their
advance, these tentacular feet happen to come into contact with
a solid body, the animal may either continue its direction of
advance unchanged, or may deflect that direction towards the
solid body." UroMer riibnix has the power of ascending per-
pendicular surfaces, and also of attaching itself to solid bodies.
The ambulacral feet are so strong in holding on to a perpen-
dicular surface, that the feet of one or two rays are suflGdCDt
to support the animal when its body is distended in a hori-
zontal position (Fig. 74). If Vronfir is turned over on it*
dorsal surface upon the flat floor of a tank, it does not occupy
more than half a minute in nghting itself. This is done by
a number of the ambulacral feet of three rays getting a firm
hold of the floor o£ the tank ; this being done, the animal
turns a complete somersault — the disc and inactive rays being
thrown over the active ones with considerable rapidity.

('■) The sun-stars (So/iin/it) move about in a similar manner
to Umsttr ; but the method of righting themselves is slightly
different from that just described.

((') Aslropcctnt Hiiiitnli'inin. — Romanes and Ewart state
that the ordinary locomotor movements of this species txtm
highly peculiar. The general form of the animal rescmblefl
UrnMcr, although its disc is proportionally larger, and tksV
whole animal smaller. Its ambalacral feet are pointed tubef,
about a quarter of an inch long, and unprovided with uy

' P/ii'/ojo/A'Voi Trnn'aaiBiU, iSSl. p. Sjq.

H PHYSIOLOGY OF THE IXVERTEBRATA. 381 ^|

sucker at the tip. "When tlie animal is uot walking, these ^|

feet are nevertheless in a constant state of movement, and ^^|

their movements are then of a peculiar writhing, almost ^^|

L f"-" i\ 1

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vermiform character — twisting about in various directions,

and frequently coiling round each other. When fully pro-

truded, however, they are perfectly straight and stifl'." A

■. J

382 PHYSIOLOGY OF THE INVERTEBRATA.

number of tliese feet are continually being retracted, whilf
others are being protrnded, and this state of affairs goes on
alternately.'

These animals can crawl up perpendicular surfaces, bat
are very soon tired. This is due to the absence of any dif-
ferentiated strnctures in the form of sucking discs.

The mode of locomotion of Astrojuclm is peculiar. Vpon
a dry, flat surface, it ■' points all the feet of all the rave in
the direction of advance, and then simultaneously distends
them with fluid ; they thus become so many pillars of anpporl.
which raise the animal as high above the flat surface as their
own pei-peiulicular length. The fluid is then suddenly with-
drawn, and Astmpcctoi falls forward flat with a jerk. This
manoHUTre being again and again repeated at inter\-als of
about a quarter of a minute, the animal progreaaea in a uni-
form direction at the rate of about an inch per minnte. In
this mode of progression, all the feet of all the rays are co-
ordinated in their action for determining one definite direction
of advance — those in the ray facing that direction acting
forwards, or centrifugally. those in the hinder rays backwnrds,
or centripetal ly, and those in the lateral rays sideways."

When Astropedm is walking along a flat horizontal surface
under water, its mode of locomotion is the same as the above.
only the motion is very rapid, " It appears, however, as if
the feet, besides being used as walking poles in the manner
just described, are also used to sweep backwards along the
floor of the tank, and so to assist in propelling the animal
forwai-da after the manner of cilia. Therefore, while walking
in water, Astropeclcu is kept stilt-high above the surface on
which it is walking, by some of its feet, while others of it»
feet are engaged in these sweeping movements,"

Astropectcn has a rapid rate of movement, being be!
one and two feet per minnte. When placed upon ita back,
has the power of righting itself very rapidly.

' The teet usually ro
very snddenl; collapse.

u extended for a quarter to half a mlanle, bi

PHYSIOLOGY Of THE INVERTEBRATA,

383

((Q The Opkiuridea. — In the brittle-stars the ambnlacral

feet are only mdimentaty, although ezceedmgly active; they

- are devoid of enokers ; and their mode of protrusion and re>

traction ie exactly like that of Astropecten, but more rapid in

i; O

action. These animals are much the most actively locomotive
of all the starfishes ; " and the reason is, that having discarded
the method of crawling by the ambulacral system, which is
common to nearly all the other Echinoderms, they have
adopted instead a completely new, and a much more effectual

384 PHVSIOLOGV OF THE INVERTEBRATA.

method. The muscular system of the rays is very perfectly
developed, enahling these long and snake-like appendn)^ to
perform with energy and cjuickneas a great variety of snake-
like writhings. As the movement of all the arms ia co-ordi-
nated, the animal is able by these writhings to shuEBe itself
along flat horizontal surfaces at a considerable speed. Bnt
when it desires to move still more rapidly, it adopts aikother
plan. If the animal is advancing in the direction of the
arrow (Fig. 75), one of its rays, r, is pointed straight in that
direction ; the two adjacent rays, 2 and 3, are thrown for-
wards as far as possible, and then, by a strong contraction
downwards upon the floor of the tank, these two rays partly
elevate the disc, and, while keeping the disc so elevated,
throw themselves violently backwards into the form of
crescents, as represented in 2' and 3', The result of this
movement is to propel the animal forwards — ^ray i being
pushed into the iX)siti on i', while rays 4 and 5 are dragged
along into the position 4' and 5'. As soon as the rays 2 and 3
have assumed the position 2' and 3', they are again, without
an instant's delay, protruded straight, to be again instantly
thrown into the form of the curves 2' and 3'. Thus the
animal advances by a series of leaps and bounds, which vaiy
between i^ and 2 inches in length, and which follow on"
another with so much rapidity, that a lively Ophiura can
easily travel at the rate of .6 feet per minute. While thus
travelling, the ray, i, is usually kept straight pointed and
partly uplifted — doubtless in ordi-r to act as a feeler ; bat
sometimes the animal varies its method of progression, so as
to use two pair.s of arms for the propelling movements, and
in this case the remaining arm is, of course, dragged behind,
and 30 rendered useless as a feeler. Ophiura is able to nse
any pair, or pairs, of its arms as propellers indifferently, and
in all cases it so uses them by resting their outer, or distal,
thirds upon the tank floor, and at each leap raising tbeir
remaining two-thirds, together with the anterior part of the
disc, off the floor ; at the end of each leap, however, the

awever, the ■

PHYSIOLOGY OF THE INVERTEBRATA. 385

whole animal (except, perhaps, the elevated feeler-ray) lies
flat apon the floor." (Romanes and Ewart.)

Ophiura when placed on its back has the power of righting
itself; bat it is unable to ascend perpendicular surfaces
owing to the rudimentary condition of its ambulacral ap-
paratus.

(e) The Echinidea. — Unlike the rapid movements of the
starfishes, the Echini have a slow rate of locomotion. Along
a horizontal surface it is six inches per minute, while up a
perpendicular surface it is only a quarter of an inch per
minute. The ambulacral feet or pedicels have a greater
power of anchorage than the same appendages of the star-
fishes. In Echimcs the pedicels are also used as feelers.
When a perpendicular surface is reached, the animal may
either ascend it or crawl along for an indefinite distance,
feeling it all the way with its pedicels. When an Echinus
is inverted upon its aboral pole, it has the power of righting
itself, although it is a much more difficult task than is the
case with the starfishes. This is due to the formation of its
body — for it is a rigid, non-muscular, and globular mass,
whose only motive power available for conducting the evolu-
tion is that which is supplied by relatively feeble pedicels.

The spines and lantern* are also used in locomotion.
When the animal is taken out of the water and placed upon
a table, Romanes and Ewart observed that it began to walk
in some definite direction — i,e,j in a straight line, and in doing
so the only organs used for the purposes of locomotion are
the spines and the lantern, the ambulacral feet under these
circumstances not being protruded at all. The rate of
locomotion is very slow — viz., about one inch per minute. The
so-called " Aristotle's lantern "is capable of being protruded
and retracted ; and these movements are perfectly rhythmical,
at the rate of three or four revolutions per minute. The
pedicellariaB of Echinus assist in locomotion. It is by means

• '< Aristotle's lantern," or dental apparatus, in Echinus Is worked by
thirty muscles.

2 B

386 PHYSIOLOGY OF THE INVERTEBRATA.

of these gmall forceps or grasping organs, that the animal
capable of "climbing perpendicular nr incliued surfaces
rock, covered with waving sea-weeds," In the AderiiJro
the Jfo/oihuridea, the pedicellarite arc only rudinientsry-
changed habits of life on the part of these animals h«l
caused the inherited appendages to dwindle from disnW
For instance, "'the Opkiitriiica never climb sea-weed covered
rocks at all, and those starfishes which do so have their
ambulacral feet restricted to the ventral surface; it would
therefore be useless for these animals to have well-developed
pedicell arise, adapted to hold sea-weeds steady in the
which may be of so much use to the globular JSi/ii
throws out on all sides feet feeling for attachments,"

Spatamjus (one of the EJnm lea) crawls about somewhat
slower than £i:hinu'< and it is incapable of climbing per-
pendicular surfaces. When placed upon its back it has even
a greater difficulty in righting itself than Eckiniis. It rights
itself entirely by its long and mobile spines.

(/) The Holothuridea,— These animals " crawl slowly.&ixl
indulge in prolonged periods of quiescence They are, hoir-
ever, able to climb perpendicular surfaces."

wouJd

eloprfj
Latmd^l

The Trichoscolices.

The TurhfUnHa. — Although the parenchyma of these
animals is contractile, they have only a veiy feebly-developed
muscular system. The muscular fibres appear to be iffl- i
striated. The Tiirbdlaria are divided into (a) the lihahdoci
and (6) the Dendroc&Aa. The smaller species of the fir*
mentioned sub-order swim by means of their ciliated epithe-l
lium ; whereas the larger species appear " to tloat from plan a
to place by means of their epithelium." The Dauirofalu,
the other hand, crawl along somewhat in the manner of tl
Oastavpoda. Sometimes the tentacle-like processes (situat
at the anterior end of the body) are used as oars when theitl
animals move upon the surface of the water. According tl

PHYSIOLOGY OF THE INVERTEBRATA. 387

Martens,* Flanaria lichenoides moves by means of tha pro-
truded lobes of its muscular pharynx.

The Rotifera. — The muscular system of these animals is
composed of unstriated fibres. The most characteristic ap-
paratus is the so-called *' wheel." By its agency these
animals swim freely about, or, when at rest, create certain
water currents. The ** wheel " or trochal disc and its append-
ages vary in different genera. The edge of this disc is
generally ciliated, but in some forms {e.g,^ Stephanoceros) it
is produced into ciliated tentacula. Besides being organs of
locomotion, the appendages of the trochal disc are indirectly
prehensile organs.

The Trematoda and Cestoidea. — The movements of the
body are due to sucking-cups and cavities (i.e.j suctorial
organs), homy hooks and spines.

The Anneuda.

Muscular tissues are highly developed in the Annelida,
In HiTicdOy the muscular system into which the integument
is continued, forming a dermo-muscular tube, consists ex-
ternally of a circular muscular layer, and internally of a
longitudinal muscular layer. Both these layers are traversed
by radial muscle-fibres, which run from the interior of the
body to the surface. At the lateral edges of the body, the
radial muscles pass directly from the dorsal to the ventral
surface. Certain muscle-fibres run obliquely. In Hirudo,
locomotion is chiefly effected by means of the suckers, which
contain both circular and radiating muscle-fibrea The
posterior sucker is attached to something, then the animal
stretches itself forward to its fullest extent and fixes its
anterior sucker. After releasing the posterior sucker the
body is powerfully contracted. The posterior sucker now
attaches itself close to the anterior sucker, which is then
loosened and thrust forward as before. Hirudo can also

• JUimoires dt VAcadimie Impirialt des Sciences dt St. Pitersbourg^ tome 2.

38«

PHYSIOLOGY OF THE INVERTEBRATA.

Bwiin, though its motion in water is rather slow, '■ Whilst"
Bwiuiming, the body becomes flattened by the contraction of
the vertical muscle-fibres, which pass from the dor&al to thr
ventral surface; and then by perpendicular quick serpentine
undulations, it progresses like a wavy ribbon."

The mnscle-fibres are developed, as in the higher aniuials,
out oE uncleated, spindle-shaped, inuscle-cells. The fibres
are not transversely striated, but they are enveloped in a
structureless sheath.

In the Oliffocha-ta, represented by Linuhricux, the moacaiar
BjEtem is somewhat similar to that already described.
Beneath the cuticle and hypodermis there is an txteraal
layer of circular muscle-fibres and an internal one of longi-B
tudinal muscle-fibres ; there are also radiating and oblique^
intertwisted fibres. On the ventral surface of each som:
(in f.uiiiliricm) four pairs of minute pita occur, from eacho
which projects a long hook-like seta or bristle. The set» a
bristles can be projected or retracted at will, and they mM
locomotion in a somewhat similar manner to the suckers of
Hirndo. Both these devices are the means of anchorage,
while the subcutaneous muscles produce the vermionlar
motions of the body.

The Polyc/iaia, or marine worms, are usually proridecl with
parapodia (rudimentary limbs), having numerous chilinoii''
seta} embedded in thetu. In the body-wall the circidar and
longitudinal muscle-fibres are well developed. The suli-
order Eirantia contains the free-swimming PoJyehata. The
head of these animals contains teutacula, and geuerall;
cirri, and the anterior portion of the pharj-nx is like s pro-
boscis, being eversible. The parapodia are well developed in
the Errantia.

The Ttihieola, or sedentary Polt/rhrda, have no cirri, and
the parapodia are only slightly developed. None have B
proboscis or eversible pharynx. Tlie Tubieol't arw not tree
and actively locomotive animals like the Urinntia, They
live in tubes, which they construct either by gluing togelbcfj

^S togelbcf^l

PHYSIOLOGY OF THE INVERTEBRATA. 389

sand and pieces of shells, or ** by secreting a chitinons or
calcified shelly substance."

Locomotion in the Annelida is aided bv means of aciculi
and setaB. These are used as fulcra when they creep, or as
oars when they swim.

The Nematoscolices.

The general movements of the body in the NenuUoidea
are due to a subcutaneous circular muscle-layer; and its
longitudinal and transverse muscles are quite distinct from
each other. In most of the Nematoidea the longitudinal
muscles form four large bands — ^two on the ventral and two
on the dorsal surface. These animals are devoid of limbs,
though they may sometimes be provided with setiform spines
or papillas.

The Myriapoda.

Great advance is observed in the mode of locomotion in
the Arthropoda. There is no longer any contractile envelope
like the Anndida and their allies, for here the muscular fibres
are all grouped into distinct masses or individual muscles,
which are inserted into such and such a limb or part of the
body by means of tendons. In the Arthropoda all the muscles
are transversely striated.

Locomotion in the Myriapoda is produced by means of the
limbs. Almost all the segments bear at least a pair of
articulated limbs terminated by claws.

The Chilopodu (centipedes) usually live in the earth or
under stones ; they run with considerable swiftness in pursuit
of their prey, and can even progress backwards by the aid of
their tail-like posterior limbs, which at other times are
dragged helplessly behind them.

The Diplopoda or ChUognatha (millipedes) possess two pairs
of limbs on each segment except the posterior segment, which
is devoid of these organs. The movements of these animals,

390 PHYSIOLOGY OF THE INVERTEBRATE.

uotwithstandiBg tlieir immense namber of limbs, art- alwsjal
very alow, and they generally try to escape danger by rollinga
tliemaelves up into a ball.

The Insecta,

In tbis class the thorax always bears the organs of loc
motion, which, in viod insects, consist of six ambnlatoi
limbs and four wings. The form of these organs ia v^yj
various, but their general anatomy is always similar. Thi]
centre of the ventral surface of the thorax is occopied by ■
narrow piece termed the sternum, which frequently projec
as a ridge externally, and generally gives off an intemsll
process for the insertion of muscles. On each side of this
an' the sockets for the legs, of which each segment of the
thorax bears a pair. The first joint or coxa of the legs is
sometimes immovably attached to the thorax, snmetim
articulated with it by a sort of ball-aud-socket joint. Thw^
next four joints are termed respectively — ^the trochanter,J
femur, tibia, and tarsus. The tarsus or foot sometimes (
sista of one, but generally of from three to six joints. Th«
terminal or sixth tarsal joint is furnished uith two cnn
and pointed claws or ungues, often toothed, and in i
cases accompanied by a pair of soft membranous organs O
pulvilli, which are very distinct in Muaci (house fly). Tboasl
adhere, like suckers, to any object against which they may b
applied, and thus enable their possessors to walk securely'
even in a reversed position.

Tlie ambulatory limbs and their various joints undergo veiy
many modilications in the different orders and groups of the
JiiM-rltt ; always, however, in exact coincidence with tie habite
of the individuals — ^in leaping or jumping insects, such ts
Miiptfri/.!,* lAX-iittti, and UnflU-x^ the posterior limbs are maoh
lengthened and the femora very thick, forming ]
juuipiug orgao)^. In M'ltitis, the anterior limbs are a

> See Dr. GrUHthi' Tlit DUta*tt of CVopt. p. 51 (UeU * Sou].

powerM^H

PHYSIOLOGY OF THE INVERTEBRATA. 391

three. When the tripod which is moviDg has come to the
developed as to give the insect a praying attitude — ^these
limbs are used as prehensile organs. The anterior limbs of
(xryllotcdpa (the mole cricket) are modified to suit this insect
to its burrowing habits. In those insects which swim, such
as Di/tisctiSy the tarsi are generally flattened, ciliated, and
disposed like oars. In fact, Dytiacus possesses organs of
natation, of burrowing, of reptation, and of flight. This Cole-
opterous insect is, in a sense, comparable to the great epic
poet's fiend in the nature of its various movements, and
also the different elements in which it is capable of living : —

" Through strait, rough, dense, or rare,
With head, hands, wings, or feet, pursues its way.
And swims, or sinks, or wades, or creeps, or flies.

n •

These wonderful modifications of a general plan are certainly
strong points in the theory of natural selection. *' It may
metaphorically be said that natural selection is daily and
hourly scrutinising, throughout the world, the slightest
variations; rejecting those that are bad, preserving and
adding up all that are good ; silently and insensibly working,
whenever and wherever opportunity offers, at the improvement
of each organic hcing in relation to its organic and inorganic
conditions of life. We see nothing of these slow changes in
progress, until the hand of time has marked the lapse of ages,
and then so imperfect is our view into long-past geological
ages, that we see only that the forms of life are now different
from what they formerly were." f

Mr. H. H. Dixon, of Trinity College, Dublin, has recently
made some observations on the locomotion of various insects,
and he finds that in the case of those which move quickly, the
best method for observation is instantaneous photography.
Instantaneous photographs of moving flies show that they
move the front and hind legs of one side almost simultaneously
with the middle leg of the other, while they stand on the other

* Milton's ParadUe Lost,

t Darwin's Origin of Hptciet (6th ed,), p. 65.

393

i>HYSIOLQGY OF THE INVERTBBRATA.

ground, the other tripod is nused, and so on. Dixon'i

observations show, However, that while no leg of one tripod
ever moves simuItaneonBly with any leg of the other, y«l
there is a succession in the movements of the legs of eftdl
tripod. The hind leg on one side is ^-st moved, then the
middle on the other, and when the hind leg ho* been moved
forward and almost reached the ground, the front lepf of that
aide ia raised. The middle leg and the front leg of the
opposite sides come to the ground almost simultaueoualy. It
is usually just when the hind leg is reaching the ground, anil
the front leg is being raised, (hat the lrii>od on which th»
fly is resting thrusts the body forward. After the movemeDE
of each tripod there appears to be a short pause, during whidi
all six legs are on the ground together.

Dixon has also observed the tripodicwalk in earwigs, water
scorpions, aphides, and some beetles. In the case of some
slowly moving beetles and aphides, which can be observed
without photographic means, quite irregular movements haVf
been observed. By cooling aphides, they can be made to
move very slowly. In this condition one was observed lo
move its legs in slow succession in the following order: —
{a) Right hind, (6) right middle, (r) right front, {A) left hiod,
(c) left middle, (/) left front. This walk was continued Ust
some time, occasionally interrupted by the following order, oc
some other quite irregular walk : — (ft) Hight hind, (6) right
middle, (c) left hind, (r?) left middle, {() left front, (/) right
front.

In caterpillars the le^s forming a pair seem to move simul-
taneously ; the motion begins at the posterior end of
body, and proceeds regularly forward till the moat antei
pair of legs are moved.*

According to Darwin, f Fapilw/eronhi, of Brazil (one of

nol- J

tbafl
iric^H

Mr. Dixon kindly sent tho author seTeroI photographs UlngtiKliiig th*
«bove movements, but unfortnnately thej cannot be repmdoced aa woo*

Journal nf Heaearclitt (CllSp, li.).

PHYSIOLOGY OF THE INVERTEBRATA. 393

Zq(ndoptera)j uses " its legs for mnninff,'' this being an ex-
ceptional habit among butterflies.

The wings of insects are appendages attached to the meso-
thorax and metathorax. They are composed of a double
membrane, supported internally by a variable number of
nervures. These serve to keep the wings extended. There
are never more than two pairs of wings, sometimes only one,
and they vary in form. When they really serve for flight
they are thin, translucent, and covered with microscopic
scales as in the Lepidoptera; but the anterior wings often
become hard and opaque, and becoming useless as organs of
flight, form elytra — i.«., protecting sheaths, for the posterior
pair of wings : such an arrangement occurs in the Coleoptcra.
Although the wings of insect^ are usually four in number, the
posterior pair is frequently absent, and, in fact, the Diptera
is characterised by the possession of only one pair of wings.
In these insects a pair of small knobbed filaments, situated
on the sides of the thorax behind the wings, and which ai*e
called halteres, have been regarded as the representatives of
the posterior wings.

In almost every order of the Iiisecta there are genera, species
and individuals, as certain female aphides, which are apterous
or wingless.

" The movements of the wings are produced by two
extensor and several smaller flexor muscles,* which arise
from the middle and posterior thoracic segments, and are
inserted on the tendinous process at the base of each wing.
The size of these muscles is proportionate to the size of the
wings and their mode of use in flight. They are, consequently,
all equally developed when the four wings participate equally

* Dr. Allen Thomson has measared the diameters of the mascular fibres
in the Insecta with the following results : —

Greatest diameter 7^ inch.

Xjeast ,,..... ... ToB" >»

Average ,1 •••••.. • tttt i»

Distance of transverse striae v^Vtt >»

394 PHYSIOLOGY OP THE INl'ERTEBRATA.

in the act of flying, as ia the case with the Lcpiilopltra, JfynitM-
optrrti, the majority of the Mctiroptfra, the Libflludiiin; FeHiAa,
and finally, the Cieadulai, and the A^kididtc. The mneclFC
of the anterior wings are comparatively smaller than those of
the posterior, when the first are not used, properly spei
except to cover the latter, as is tlie case with the Coleopli
the Bnga, and many of the Orl/'opfi-ra." (Von Siebold.)

There are also certain accessory organs which aid in tlie
phenomenon of flight. Prof. Huxley says that " the
doubtless assist flight by the diminution of the specific graritf '
of the insect, which followa upon their distention."

Concerning the phenomenon of flight- Sir Richard
}]aBi justly remarked that " in no part of the animal kingdom
is the mechanism for flight so perfect, so apt. to that end, *s
ill the class of insects. The swallow cannot match the dn^^-
fly in its atrial course ; this insect has been seen to outstrip
and elude its swift pursuer of the feathered class : nay, it cm
do more in the air than any bird — ^it can fly backwards and
Bideloiig, to right or left, as well as forwards and altt
course on the instant without turning." "

The Arachnida.

In tlie Arnehniihi the organs of locomotion art- all fixed
the cep halo-thorax, and consist of eight pairs of limbs, strongly
resembling those of the In-fu-tn ; and almost always terminftted
by two hooks. The length of these organs is generally coil'
siderable, and they easily break ; but, as in the Cruxtocen.
Btnmp, after having cicatrised, reproduces a new limb, wl
increases by little and little, and ends by becoming similar
that of which the animal had been deprived,

* Tho fligbt of the bee exceeds twelve milea an hour, and it will'go
miles in search of food. Its wings, braced together in flight bj a
booklets, bear it forward and bBCkward, upward, downward, or id
arioHted course, bj a beantif ul mechapioal adaptBtion. (See Cowao'i
Bi-e.) For a. full eipoaicion oC the fliglit of iosccts the reader i*
to the worlc of Chabrier io Mini, ilii .)fiii(fani, ton

]

._.ed
con-

■jM

Mid

PHYSIOLOGY OF THE INVERTEBRATA. 395

The Ara^hnidavixe entirely devoid of wings, and the organs
of locomotion are never inserted on the abdomen.

The Araneina may be conveniently divided into two groups
— ^the wandering and the sedentary spiders. In the former
group belong the swift-runner, the side-walker, and the vault-
ing or leaping spiders. All the wandering spiders trust to
their swiftness of movement in securing their food ; and some
of them can run in any direction.

The Crustacea.

In the lower Crmtacea, represented, for example, by the
Phyllopoda, Dr. G. O. Sars states that there are two modes of
locomotion. In the case of Cyclesth^ria hidopi, one of these
is accomplished when the animal is freely suspended in the
water ; in the other it takes place while it is at the bottom
of the water ; in the former case, it is a swimming motion ;
in the latter, a creeping or more generally a burrowing,
motion. The swimming motion is performed exclusively by
the aid of the antennaD, the repeated strokes of which propel
the animal through the water. During this motion, the
antennae, together with the anterior part of the head, remain
exserted from the front part of the shell, being moved laterally
to a greater or less extent. The locomotion effected by this
means is not very rapid, nor abrupt or jerking, but a perfectly
even run through the water, whereby the animal as a rule
turns the dorsal part uppermost. Not rarely, however, this
attitude becomes changed, and the animal is often obsened
to revolve several times before breaking oflF the motion and
sinking to the bottom. On the whole, the swimming motion
appears to be eflfected with considerable effort, especially
when the individuals arc carrying a young brood ; and hence
this motion is never continued for any length of time, but
takes place at intervals, the animal being more frequently
found resting on the bottom or affixed to some submerged
object.

396

PflVSIOLOGY OF THE INVERTEBRATA.

The creeping or burrowing mode of locomotion, whicb
takes place while the animal is on the bottom, is eff«t«l
partly by the antennse, but more especiaily by the flexion and
powerful extension of the trunk, the caudal plat-e being tbiif
exserted from the shell inferiorly and moved rapidly behind,
ag it strikes against the bottom. This mode of loconiotion
has sometimes a distinctly jerking character. Often, by
repeated strokes of the tail, the shell will be turned rounJ
several times in snceession, and may thua get rather deeplj
buried in the loose muddy deposit at the bottom of the water.

Dr. Sars, in his important paper (/(«■. v'lt., p. 33), also
describes the movements of the shell, head, trunk, tail, eye,
antennnlET, antennte, &c., but it is not our object to refer to
tJiese separate movements.

In the higher Ciin^tacea the organs of locomotion or limbs
are connected in pairs with the different thoracic segments;
there are fretjucntly seven pairs, as in the /so^Jcrfo (c.y.,
(hiisnis), the prawns, and the T"/ilri (sand-hoppers) ; but in
other Crii-'itiirea — -c.r/., the ci-abs, crayfishes, and lobstt^ra — ther
are only five pairs of limbs. The structures of these append-
ages differ considerably : in some forms they are wholly
foliaceous, membranous, and exclusively adapted for swim-
ming ; in others they have the form of small flexed colnmn)',
articulated, and disposed only for walking; in others, still,
besides remaining adapted for this mode of locomotion, they
become suited to act as so many small spades wherewith to
dig the earth, and in that case they are enlarged an^ lamel-
lated towards the extremity; and still, finally, in others thej
terminate in forceps, and l^ecome prehensile organs, perform-
ing at the same time the function of locomotion. In tbf
swimming Criistni:m, such as A^ti'ms, Homni-ux, Palauum, Ac,
the abdomen terminates in a tail-fin, which is the principal
organ of locomotion ; but in those individuals which wnlk
more than they swim, the tail-fin is, as a rule, very small, and
folded under the thorax : in the crabs, for example, thii

PHYSIOLOGY OF THE INVERTEBRATA, 397

portion of the body is reduced almost to nothing, and con-
stitutes then a movable apron placed on the lower surface
of the body between the limbs.

In AniarMS the ambulatory limbs are composed of seven
separate joints : the basal joint being the coxopodite which
is followed in succession by the following joints : — ^the basi-
podite, ischiopodite, meropodite, carpopodite, propodite, and
dactylopodite.

The Mollusca.

The movements in these animals are, as a rule, executed
by means of a muscular organ, termed the foot, which varies
greatly in its form, in accordance with the habits of the
animal. The foot consists of a mass of muscular fibres, run-
ning in various directions, by the contraction of which its
movements are effected. In many of the Mulli(>ica, the foot
forms a flat disc, which adheres to any substance to which it
may be applied, and thus, by the alternate contraction and
dilatation of its different parts, enables the animal to crawl
slowly along. In other forms, the foot is bent upon itself, so
that its sudden extension causes the animal to perform a con-
siderable leap {e,g,, Cardhnn and Trirjonia), This organ is
also the means by which the burrowing species bury them-
selves in the sand or mud ; and in those species which boro
in the solid rock, the foot is also called into requisition ; its
surface in these cases being covered with minute silicious
particles, which assist greatly in the enlargement of its owner's
stony dwelling.

But although most Molht^a possess a greater or less power
of locomotion, others are confined to a single spot, during all
but the earliest period of their existence, when they are free-
swimming organisms. In the non-locomotive Molhmca the
foot is either wholly undeveloped (c.^., Ostrea), or serves
merely to support a glandular organ, from which a chitinous
or shelly substance is secreted, which serves to attach the

398 PHYSIOLOGY OF THE INVERTEBRATA.

animal to submarine objects. This modification occurs in
MytUus^ Pinna, &c.*

In the Pteropoda the function of swimming is performed
by the flapping epipodia, which are muscular expansions, bat
it may be remarked that in these Mollusca ** the rest of the
foot is always small, and often rudimentary, in correspondence
with the small size of the neural face of the body."

The locomotive organs of the Cephalopoda are the tentacula,
which are arranged round the head, and furnished on their
inner surface with numerous sucking-cups, which enable the
animal to take a firm grasp of any object. By means of the
tentacula t the Cephalopoda creep along the bottom of the sea
with the head downwards. These animals also swim rapdij
by the expulsion of the water from the branchial chamber.

^ For an account of the movements of varions parts of certain bivalve
Mollascs, see the papers by D. M*Alpine in the JFVoe. Boy, Soc, JSdiHh^
vol. 15, p. 173; voL 16, p. 725.

t The tentacula are also prehensile organs.

CHAPTER XIII.

REPRODUCTION AND DEVELOPMENT IN THE INVERTEBRATA.

Every living organism possesses the power of reproducing
its kind. The process by which this reproduction or pro-
creation is maintained may be either asexual or sexual ; and
some scientists* assert a third mode of '* reproduction " — viz.,
by spontaneous generation, abiogenesis, or heterogenesis, i.e.,
the origin of living organisms dc novo] without parents. It is
not our object to discuss the arguments for and against the
theory of spontaneous generation, suffice it to say that the
researches of Pasteur, Tyndall, Dallinger, and others, point
out that *' no definite instance of life originating de novo has
been proved," and their experiments appear to negative its
possibility.! Yet, it has been stated that the facts adduced
against the theory " do not appear to invalidate the possibility

* See Dr. Bastion's Btginninga of Lift (1872) ; Bennett's Physiology ^
p. 421 ; Pouchet's NouveUes JExp^riencea sur la Generation Spontanieet nur
la Bdsistance Vitale, p. no; and also the works of Prof. P. Mantegazza
and MM. Bernard, Pennetier, Jolj, and Musset.

t Concerning the controversy on spontaneous generation, Prof. Huxley
states that biogenesis (life from previous life) has been " victorious along
the whole line;" but at the same time he remarks **that with organic
chemistry, molecular physics, and physiology yet in their infancy, and
every day making prodigious strides, it would be the height of presumption
for any man to say that the conditions under which matter assumes the
qualities called vital, may not some day be artificially brought together."
And further the great biologist remarks, " that as a matter not of proof but
of probability, if it were given me to look beyond the abyss of geologically
recorded time, to the still more remote period when the earth was passing
through chemical and physical conditions, which it can never see again, I
should expect to be a witness of the evolution of living protoplasm from
non-living matter."

400 PHYSIOLOGY OF THE INVERTEBRATA.

of abiogenesia occurring in cert^ain conditions, and it ia u»-
philosopbical to assert the impossibility of ita occurrence now
or in some past time. The intimate relations known to exist
between physical, chemical, and vital phenomena, depending
on the lawa of the conservation and transmutation of energy,
and the theory of evolutional development, indicate the pro-
bability of abiogenesia, and it is one of the problems A
biological acience to ascertain the conditions in which tliii<
may occur."

" 111 the domain of science any logical and necessary de<
duction or induction ought to be admitted, though it may
shock old ideas and shatter old dogmas. The same relifpona
and metaphysical prejudiMs, which have been so deeply di»-
qaieted by the doctrine of evolution are still more . alarmed
and annoyed by the idea of spontaneoas generation. But
this may be changed as time rolla on, as has been the case

with the Uaiwinian theory Not- many years ^o the

majority of naturalists believed in the immutability of all
organised beings, and, as every epoch had its special fauna
and flora, it was necessary to recognise, as did the immorlal
Cuvier, a series of successive creations. When God, irre*-e-
rently compared to the machinist of an opera, whistled ono-.
an implacable cataclysm annihilat<'d all the living worid;
when He whistled a second time, but creatively, a new fauna
and a new flora rose to life. Thus had things to go on at
every geological epoch. From the trilobite to the mammoth
every species had thus to be formed by ' magical crystAlUe^
tion,' Assuredly there was here sponiai\eou» r/enrratioti of
moat aatonisbing kind, but it shocked no one, because it '
in more or less tacit accordance with metaphysical
religious ideas." But all this is now changed, for the mnjoril
of, if not all, naturalists firmly believe in the doctrine
evolution, or the mutability of organised beings, as revealed
the genius of Darwin.

Although spontaneous generation is, at the present ti
" not i)roven," we mention the fact that it is still

PHYSIOLOGY OF THE INVERTEBRATA. 401

upon by some scientists as one of the " modes of reproduc-
tion."

Asexual reproduction includes the processes of gem-
mation, fission, endogenous cell formation ; and a variety of
asexual reproduction is known by the name of partheno-
genesis.

(a) Gemmation. — In this mode of reproduction a small
portion of the body enlarges and gradually increases in size.
When fully developed this bud may either become detached
from the parent and develop into a free organism (like the
parent), or it may remain permanently attached to it, giving
rise to a colony,

(6) Fismn.— This mode of reproduction, common in the
lower animals (and of special importance in the formation of
new cells), consists simply of a division of the animal into
two or more parts. Each part then grows and ultimately
assumes the same form as the parent ; and possesses the same
power of reproducing its kini Should the division, how-
ever, remain permanently incomplete, colonies of the animal
will be produced.

(c) Endogenmis cell formation. — ^This mode of asexual
reproduction or agamogenesis occurs in the Protozoa. The
animal becomes encysted — i.e., it surrounds itself with a cover-
ing or cell-wall. After this, the nucleus becomes constricted
and ultimately may be divided into many portions. The
protoplasm then divides in a similar manner, and there may
result two, four, eight, &c., cells, in each of which there is at
least one nucleus.* These cells finally rupture the parent-
cell and are set free.

(d) Parthenogenesis. — As already stated parthenogenesis is
a variety of asexual reproduction. In this, case the whole
development of the embryo is effected without the succour of
fecundation. Parthenogenesis is the production of young,
api)arently without any previous congress with the male

* Sach a process is termed segmentation, and may be seen in the earlj
stages of the development of the embryo of higher forms,

2 C

40I

PHYSIOLOGY OF THE INVERTEHRATA.

organism ; and it is illustrated by the development of Tariovt
formB of Mt'difia; Taiiiu, and of Aphides.

Sexual reproduction. — This mode of reprodoctaon,
gamogenesis, is the resnlt of the fusion of two diBtind
elementa — a male element, or sperm atosuxin, and a female
element or ovum. Thpse are differentiated cells, prodaced
in special organs, of the parent or parents, and by their
coalescence a series of changes take place, which nltimately
give rise to a new organism. These elements ( S and 5 ) may
be produced in the same individual (aa in many A-nvrli»ia and
MuUitsfo) : such a condition is termed hermapLroditi^n ; bat
in the majority of the Inccrkhmta the male and female or^asi
are on different individuals, in other words, the aexes are
completely separate.

Prof, Huxley states that it is probable tliat hermaphro-
ditism " was the primitive condition of the Bexual apparatus,
and that unisexuality ia the result nf the abortion of lb',
organs of the sex, in males and females respectively,"

Although some Invertebrates have both sexual organs
the same individual, these organs are often so arranged
self-fertilisation is almost , impossible. As already
certain Molhinca and Annelkia are hermaphrodites, but
all pair. Darwin* states that he had "not found a ^\
terrestrial animal which can fertilise itself. This remarkidilB
fact, which offers so strong a contrast to terrestrial plants, ia
intelligible on the view of an occasional cross being indispens-
able ; for owing to the nature of the fertilising element then
are no means, analogous to the action of insects and of the
wind with plants, by which an occasional cross could be
effected with terrestrial animals without the concnrrenoe <ti
two individuals. Of aquatic animals, there are many
fertilising hermaphrodites ; bat here the currents of
offer an obvious means for an occasional cross." Darwin
remarks that he failed "to discover a single hermapbi
animal with the organs of reproduction so perfectly

, * Origin of Sptcio (6th ed.), p, 79.

PHYSIOLOGY OF THE INVERTEBRATA. 403

that access from without, and the occasional influence of a
distinct individual, can be shown to be physically impossible."
Darwin concludes, from a large number of observBtions
and facts that ''an occasional intercross between distinct
individuals is a very general, if not universal, law of nature."

The male element or spermatozoon varies in form and
size in different animals, but consists of a head and filiform
appendage or appendages.* The spermatozoa move by
vibrations in a fluid called the semen, where they exist in
large numbers.

The female element or ovum is a nucleated cell developed
in the ovary. In all animals the ovum is nearly identical.
It consists of a vitelline membrane, a protoplasmic contents
or vitellus, a germinal vesicle (nucleus), and a germinal spot
(nucleolus).

As already stated it is the union of these two elements
which give rise to offspring. Fecundation is brought about
by various methods in the animal kingdom. But as far as
the Invertebrata are concerned, these methods will be described
more in detail later in this chapter. Suffice it to say that in
the majority, of the unisexual Invertebrata copulation or the
union of the sexes takes place. In animals higher in the
zoological scale — ^for instance in fishes, the male discharges
the semen over the spawn or ova of the female, for there is
no act of copulation. In many of the Amphibia and RcptUia^
the male clings to the back of the female, and then discharges
the seminal fluid or semen over the ova as they pass through
the uro-genital aperture.

In the Aves and Mammalia; and also in many of the
Invertebrata, the semen is introduced by the penis into the
genital organs of the female.

By any one of the above acts the ovum becomes fertilised ;
a series of changes occur which result in a more or less
complete segmentation. If this segmentation or division is
complete — i.e., involves the whole vitellus — it is called

* In Astacus there are many appendages.

404

PHYSIOLOGY OF THE INVERTEBRATA.

holoblastic. Holoblaatic segmentation occurs in the Mm
via/ia, Batrachians, the lower Crustaeea, Vermes, &c. ; but ifth^l
segmentation is incomplete or involves only a portion of tiisfl
vitellus, so that the remaining portion may be atilised ■
nourishment during the early stages of the development <
the embryo, it is termed merobtastic. Meroblastic segmeDt*^^
tion occurs in the ova of Avcs, Amphihia, Crphahrpwi/i, ■
higher Crustacea, and the Instxta.

The detailed description of the changes which occur m t
ovum after fecundation belongs to embryology, conseqnently
it is beyond the province of this volume, which treats of the
functions of animals after birth. Nevertheless, we shall allude.
in passing, to the broad outlines of the development of the
fecundated ovum.*

Besides the above-mentioned mode of serual t^productioD
(viz,, that of the fusion of two different elements), there i
another mode tenned conjugation, or the union of twostnttA
protoplasmic masses. These may be derived from diffen
parts of the same individual, or from two individuals of ti
same species. The union of these similar masses ultimat«
results in the development of a new organism. This n
of reproduction occurs in some ProloKia.

The I'rcjtozoa.

The mode of reproduction in the Momra and ProtoptnOa %
either by fission or by endogL'uous cell fomiatioa, Intl
former the cell divides into two portions, each portion gin
rise to a perfect organism. In the latter mode of i
duction a cyst is formed, and within this the protoplasm rf •
the original cell divides into a nnraber of segments which
ultimately rupture the parent cell and escape as separate
individuals.

* For further details cia the subject of embryolo^ the render i» referral
lo Balfonr'fl Treatift on Oomparalive Embryoloyg; and Faster and BoUooi'i

J'ractlcat /.'nilri/ofci/y.

PHYSIOLOGY OF THE INVERTEBRATA. 405

In the Gregariiuc reproduction occurs by endogenous
division of the encysted body. Sometimes two full grown
organisms come together, adhere, and then surround them-
selves with a cyst. The result in each case is the forma-
tion of segments, which become spindle-shaped cells, called
pseudo-navicellao. These grow and finally rupture the cyst,
and thereby are set free. The pseudo-navicellae are sur-
rounded by cell- walls, but these burst, and the protoplasmic
contents of each escapes as a moner-like cell resembling
Protamceba. The moner now becomes differentiated into
ectosarc and endosarc, and the young Gregarina is now
amoebiform. In this stage of the development two arm-like
projections appear: one of these lengthens and separates,
forming a perfect GregaHna, The other elongates and absorbs
the rest of the mass and also becomes a perfect Gregarina*
This elongating stage has been termed by Van Beneden, the
pseudo-filaria phase. Afterwards the body becomes shorter
and broader, and a nucleus appears, the animal then passes
into the adult form.

The Infusm^i propagate by fission, endogenous division,
gemmation, and conjugatioji.

In the Infusoria fiagdlata multiplication by longitudinal
fission occurs in several genera. For instance, in Codosigay
the flagellum is first retracted and then fission .takes place ;
in Anthophysa the cell becomes encysted before the division
occurs.

Drs. Dallinger and Drysdale have investigated the life-
cycle of many genera and species of the Infusoria flagdlata*
Many of these forms multiply by —

(a) Fission (with or without encystment).

(6) Conjugation*

In the case of conjugation, the body which is formed
becomes encysted for a time, but ultimately the contents of
the cyst divide into either large or small bodies, which are
destined to assume the parental form.

The complete life-history of Amphipleicra pdlucida is

4o6

PJiVSIOLOGY OF THE INVERTEBRAl A

deacribed by Drs. Dallinger and Dryednle' as follows-
" development from a germ or sporuli? of extreme minnt^Qess,
and on tbe attainment of maturity multiplication by fisaioDgt
constantly nnd for an indefinite time ; but the vital power
at intervals renewed by the blending of the genetic element'
effected by the union of two, when both itre in au amteboct'
condition, from which a still sac results, in which germs or
sporules are formed, which eventually escape, and agniu
originate the life-cycle,"

Drs, Dallinger and Drysdale have shown that the in-
vestigations of Baatian, Groa, and others, on heterogenesis
and the transformation of living forms, are erroneoua. They
state that as far as their researches on the Monads go, they
are bound to say that not the slightest countenance is ginttj
to the doctrine of heterogenesis. " On the contrary, tbe lift
cycle of a Monad is as rigidly circumscribed within di
limits as that of a mollusc or a bird. There is no indi
of any unusual or more intense methods of specific tuutat
than those resulting from the secular processes involved
the Darwinian law, which is held to fumiah tbe only legil
theory of the origin of the species."

The Inf'Mxoria lentaeulifera multiply by (i) longitndinal
fission, (3) "the development of ciliated embryos in the interior
of the body. These embryos result from the separation of a
portion of the endoplast, and ita conversion into a globular
or oval germ, which, in some species, is wholly covered with
vibratile cilia, while in otbera, the cilia are con6ned to a tout
around the middle of tbo embryo. The germ makes
escape by bursting through the body wall of its pareaL'
This free swimming organism rapidly assumes the adi
form. (3) Conjugation takes place in these organisms, '

* 7yanniei!oiu 0/ Jioyal 2Iicrofo>pical iSiicitt ff, 1 87 5, p. 195.

t In the case of TelramUus rantrataa, fission proceeds for from
eight bows ; and in that of DaUiageria Ihymlali there are from seten to
eight acts of fieaion in an hour, for the first four hours, and about Ave po
hoar during the next two honra, after which acts are petformed at longer

with
taut H

PHYSIOLOGY OF THE INVERTEBRATA. 407

is followed by endogenous division. (4) Gemmation, as in
Vorticella.

The Infuscyi^ ciliata multiply by division or by conjugation.
The first mode of reproduction is effected by a constriction of
the adult cell in a transverse direction. The cell ultimately
becomes divided into two portions which separate ; each
portion finally developing into separate organisms.

Faranuecium bursaria conjugates in pairs when the anterior
ends of two individuals unite and remain united for five or
six days. According to-Balbiani,* the nucleolus and nucleus
of each organism, at this period of their life-histories, become
converted into sexual organs. The nucleolus i is converted
into an oval body which acquires a striated structure ; ulti-
mately it divides into two or four parts. These parts again
divide, giving rise to capsules containing rods which are
pointed at one end. These rods represent the spermatozoa
of higher forms. The nucleus 9 gives rise to bodies
analogous to ovules. The result of conjugation is the forma-
tion of cells which escape as young Parairuecia. During the
act of conjugation the two organisms, as already stated, are
always united together at their anterior ends ; in other words
at the apertures which form the mouth. "It has been
thought that this aperture must play the part of a sexual
orifice through which the two organisms in copulation effect the
exchange of reproductive matter ; it has also been suggested,
moreover, that a special sexual orifice is present close to the
mouth ; but these questions of structure are still doubtful." .

Balbiani's investigations have been confirmed by Clapardde,
Lachmann, KoUiker, Stein, Biitschli, Griiber, and others.

It should be borne in mind that in these low organisms the
nucleus of the cell is the all-important agent in producing
many physiological functions — without it, the above mode of
reproduction cannot take place. In fact, it has been stated
that " the nucleus plays the primordial rdlc in the cell ; if, to
use an old comparison of Aristotle's, we compare the proto-

* Journal de la Physiohgie^ tome i (1858)

4o8

PHYSIOLOGY OF THE INVERTEBRATA.

plasm to the clay, we must compare the miclens to the potter
that fashions it. The nucleus comprehends all the physio-
logical properties, the totality of which goes to constitnte life."
Concemiug the first mode of reproduction — viz., that of
tnuiBrerse fission, Balbiani states, that in forty-two days
Parameedum can produce 1,384,116 young, that is to say
that a single individual organism measuring 0.2 mm. longt
grows 277 metres in bulk."

The PoRiTEiu.
Reproduction takes place aseKualiy — by fission and bj
gemmation ; and sexually— by the production of spermatozM
and ova. The needle-shajjed spermatozoa lie in small pockets
lined with cells until required. The ova, derived from the
cells of the mesoderm, are naked amoeboid cells with a
germinal vesicle and spot. They are fertilised before leaving
the parent. The impregnated ovum divides into two, four,
eight, and more cells, and thereby passes into the morula
condition. The cells of the morula anbsecjuently become
separated into two layers — an e pi blast, and a hypoblast.
These layers give rise respectively to the ectoderm and endo-
derm of the young animal. The embryo sponge is a free
swimming larva, and in such a condition it is stated to be in
the planula stage of its life-history. After a time the ciliated
cellular portion or hypoblast of the free swimming embryo
invaginates, and the dark granular cells or epiblaat grow ovaf.
it. The latter form the ectoderm and the mesoderm is also
derived from them. The invaginated cells (ciliated) give
rise to the eudoderm of the gastric cavity. This constitutes
the gaatnila stage in the development of the Pori/e
After a time the young sponge becomes more or less cyl
drical, and an osculum and inhalent pores are produced; uict>i
calcareous spicules appear in the mesoderm.

* FoT farther infonnation on the reproduction in tha Infiitoriat, Me
Mantegazaa'fl ttkerda: mlla jjenrrnziont ilegli Inftttorii, e dtaeriaotu tU
nliMnt imort fjiecir (1S52) ; nnd W. SaviUo Kect's Manitnl of l,,fvfor!a.

PHYSIOLOGY OF THE INVERTEBRATA. 409

The Ccelenterata.

The modes of reproduction in Hydra are by gemmation,
fission, and sexual reproduction.

Gemmation is the most common mode of multiplication.
The buds may remain attached, or may become separated from
the parent ; and consequently lead an independent life. The
bud of Hydra *' consists always of a simple fold of the wall of
the stomach and the skin, so that the stomach of the young
individual is in direct communication with that of the parent,
and the chyme (nutritive fluid) can pass freely from one to
the other." When the foot of this new being has acquired a
proper development, it is completely detached at its inferior
extremity.

In regard to the second mode of reproduction — by natural
fission — it may be stated that it is comparatively rare. Fission
takes place longitudinally or transversely, and each part
repairs itself, and ultimately develops into a new Hydra
identical with the parent. In some forms of the Ccelenterata
the fission may or may not be complete. ** When it is com-
plete the cells of the corallum are definitely limited, as in
Astrceaj Favia, and Caryophyllia, but when incomplete, the
cells are branched, lobulated, and of irregular contour, as in
Agaricia, Mcearulrina^ Mo^Uictdaria, &c."

Sexual reproduction takes place in Hydra ; but the animal
is hermaphrodite. In the summer, testes are developed at the
base of the tentacula ; and one or more ovaries at the base of
the column near the disc. The testis is simply a mass of
inner ectodermal cells, by the division of whose nuclei, sperma-
tozoa are formed. A spermatozoon consists of a small oval
head and a long filament. This filament by its rapid move-
ments enables the spermatozoon (when liberated) to swim
about in the water ; and in this medium it retains its fertilis-
ing properties for many days.*

* The retention of the fertilising properties of spermatozoa after expul-
sion from the body, varies in different animals* In trout the property is

4IO PHYSIOLOGY OF THE hWERTEBRATA.

The ovary iu Hyiha is a small group of ectodermal orl
interstitial cells. One cell, however, lying in the centre o
the group is larger and clearer than the rest ; from this4
central cell the naki.'d amceboid o^Tile is produced.

In Hydra, as already stated, the sexes are united in tie
same individual ; but in other Vn-ltnteratu they are distinct;
" with the colonial polyps the sexes are separate, and each
colony may be composed of individuals which an- andragynona,
or of one sex alone. Some species are sexleEs, and remain
so ; but they produce by gemmation imlividuals of a partictUaFl
character, which have sesual organs."

In Hydra when gemmation takes place there ia idtimate
a complete separation of the buds, bat in some Caimierata
there is gemmation without separation of the young; t
occurs, for example, among the Cornlligena.

Concerning the development of Eyiira, the following is a
outline of the process : After the ovule or egg-cell eacapai I
from the ovaiy it is fecundated by spermatozoa, which are ,
discharged from the testes into the surrounding water. There
is no act of copulation. As the result of fecundation the
naked egg-cell acquires a cell-wall, and segmentation of its
mass follows; that is, a morula or blastosphere is formed.
After this a chitiuoiis shell is elaborated which envelopes the
embryo. The embryonic cells fuse together, giving the embtyo
the appearance of an unsegmented egg-ceil. In the centre
of this mass a small cavity (the beginning of tlie body cavity)
is produced. This gradually widens and lengthens so that
the embryt' becomes a closed sac. After eeveral weeks tbfl
above-mentioned shell is ruptured, and the hollow germ
escapes enveloped in a thin membrane. The protoplasmic

lost in a few minutes. SpennatoKOa in the Hemtnal rMerroir ot Ihe b
bee reiain their powers for several jeara. In msDimBlB tl)« scmiH)
elements retain theii powers of fertilisatloii for Bone lime in
passa^s of tbe femalu ; in ibe female rabbit Balbiani found tliem twd
font hours after cuitiou ; and Urs. E, van Beneden, Benecke, Einier, a
Fries have observed speriuatozou in (he uterus of bat^ for several months; |

PHYSIOLOGY OF THE INVERTEBRATA. 4"

mass which surrounds the body or somatic cavity differentiates
or divides into an ectoderm and endoderm. During all this
embryological development, the embryo has been growing in
length. At one end of the elongating embryo, a mouth is
formed by rupture of the tissues. "It first appears as a
star-shaped cleft which gradually becomes more or less round.
The tentacula next appear simultaneously. The animal then
bursts the thin membrane, comes out of it, and starts life on
its own account as a perfect Hydra, There is no meta-
morphosis in the development of Hydra (no invagination,
and no ciliated planula as in many other Hydroids). The
young Hydra passes into the adult condition by continuous
growth,"

In the Medusce the sexes are separate ; the females have
yellowish-coloured ovaries, while the males possess rose-
coloured genital glands. The ova undergo their embryonic
development in the oval tentacula. The embryonic develop-
ment, of these animals presents the following phases: —
(a) egg ; (6) morula (blastosphere) ; (c) gastrula (by invagi-
nation) ; {d) planula (ciliated larva), this stage is formed by
the closing of the gastrula mouth and the "ciliabing" of
the ectodermal cells; (c) next appears the hydra-'form or
scyphistoma, which is produced by the planula becoming fixed
and developing tentacula and a mouth at the free end. During
the scyphistoma stage there is at first multiplication by gem-
mation, but afterwards fission occurs, and the animal then
reaches the strobila stage; (/) the detached segments of the
strobila swim away in the ephyra form; {g) the ephyra
form after some weeks is converted into the adult animal
(in this case, Aicrclia), In the "development of Aurclia it
will be observed there is an alternation of generations ; the
asexual generation T)eing represented by scyphistoma and
strobila.

In the Actiniae the sexes are united. The testes and
ovaries form closely convoluted tubules and the generative
products are discharged into the somatic or digestive cavity.

412 PMYSIOLOGY OF THE INVERTEBRATA.

The embryo arises from the fecundated ovum witJiont i
metamorphosis. The ovum (Fig. 76,/) undergoes BegmeDt^l
tion within the ovaiy, and the embryo is bom 0
ciliated lai-va, possessing a somatic or digestive cavity and a
mouth. After thia two mesenteric tissues are produced which
divide the internal chamber into two uneqnal parts. Two
new mesenteries subsequently arise in the larger or antt

Fi<;. 76.-3

PKHMATomA

.\y.\) Ova •.•f LtKiAiN Inv.

Lumbricus.

* = Tdgunis.

c =- Pisa, d = Grapsui.

/=.\ct

inia. g = Aslaciu (!).

chamber. A third pair are next developed iu the posterior
chamber, and then a fourth pair in the lateral spaces. Next
the tentacula an- developed ; and afterwards four new mesen-
teriea appear, these are situated one on either side of the two
primary mesenteries, so that in all twelve somatic cavities ore
formed which ultimately become of equal siae.

The Actinw are also reproduced by gemmation or budding.

For fuller details the reader is referred to special boob
and memoirs on the subject.*

The ECHlNODEKMATi.

These animals propagate by sexual organs, and the sezai^
arfl distinct ; hermaphroditism is very rare. The ova UB 1
* See niao Prof. A. Ginrd's paper in Cotnplrt JltHdut de PAnuUmt

PHYSIOLOGY OF THE INVERTEBRATA. 413

covered by a delicate chorion, and contain a variously coloured
vitellus with germinal vesicle and spot ; the ova also contain
a little albumin. The spermatozoa are nearly always com-
posed of a round or oval body and a delicate hair-like filament,
" With a few exceptions, the embryo leaves the egg as a bi-
laterally symmetrical larva, provided with ciliated bands, and
otherwise similar to a worm-larva, which may be termed an
EchiTwpcBdium. The conversion of the Ecliinapcedium into an
Echinoderm is effected by the development of an enterocoele,
and its conversion into the peritoneal cavity and the ambu-
lacral system of vessels and nerves ; and by the metamorphosis
of the mesoderm into radially disposed antimeres, the result
of which is the more or less complete obliteration of the
primitive bilateral symmetry of the animal." (Huxley.)

The external appearances of the sexual organs in the
EcliinoderTnata are somewhat similar, but at the period of pro-
creation they frequently diflFer in colour. They are composed
of either simple or branched tubules with or without excretory
ducts. In the latter case, the contents of the organ, male or
female as the case may be, are discharged by rupture into
the body cavity, from whence they pass out through the
respiratory openings.

The EchiTiodermata are devoid of copulatory organs; the
ova being fecundated by the spermatozoa in the water in
which these animals live.

In the Hohthuridca^ there is only one testis and ovary in
male and female respectively.. Both are com]X)sed of a tuft
of highly-branched tubules, which unite to form a common
duct, which opens externally near the mouth. The early
stages in the development of Holothuria are like those of the
Asteridea^ which will be described later in this chapter. The
free-swimming larva is called an Auricidaria. The larva is
transparent, vermiform, and has four or five bands of cilia ;
and while still growing, the young Holothurian begins to
bud out by the side of the larval stomach. The larva
or Auricularia is gradually absorbed by the developing

4U PHYSIOLOGY OF THE INVERTEBRATA.

Holothurian ; and the adult form of the animal is attained'!
without any further changes,

Altliough the sexes are distinct, there is one exceptiov>]
among the Hofothuridca, and that is the ^nus Sifiui^
These animals are hermaphrodites. According to De Quati
fages," the testes ftnd ovaries are nnited so aa to form ouaJ
organ. This organ consists of branched tubules and
both spermatozoa and ova ; its excretory duct opens near
oral end of the body.

In the Astcriiica, the sexes are separate. The genital
organs are very similar in ajipearance, but the colour of the
ova is either yellow or red and the seminal fluid is white.
The ova are fecundated in the water. There are five pairs of
genital glands, one pair lying in each ray. They are aaccn-
lated or racemose orjrana, whose ducts open externally by «
narrow orifice on the dorsal side of the body. Dr. G. O. San
has shown that in BrUituja cruhcacncmos the genital orgBJU
consist of many distinct glands forming two well-miirked
series, which are situated one on each side of the middle
of the central half of each ray.

Concerning the development of Ai>fcrias (a typical exam]
of the ^-(sfcrw/ca), the following may be- taken as an outlii
of what occurs : — («) The ovum, after fecundation, becomi
totally and equally segmented — thus forming the moruht
stage, (h) The segmented ovum gives rise to a spheroidal
embryo consisting of an external ciliated cellnlar wall and an
internal gelatinous substance- (c) A depression of the ex-
ternal wall now makes its appearauce, and gives rise to the
first rudiment of the alimentary canal. The opening of tias
depression ultimately becomes the anus. This is the gastrnU
stage. (<!) Tlie ciliated embno lengthens and four sorfaoM
can now be distinguished. There is a continuous band of
cilia whicli has a locomotory function. The aliment«ry
canal, which in this stage acquires a mouth, becomes modifii "
into three jwrtions — (i<»>phagns, stomach, and inl

* AHHoiM drt Sc'cHta Xaturtlltt. lome 17, p. 66.

-ked

upkH
JineH

>ma^H

PHYSIOLOGY OF THE INVERTEBRATA. 415

Before the formation of the mouth, two lobe-like bodies are
formed from the upper part of the alimentary canal. These
lobes ultimately separate and form two distinct cavities.
These develop into two water-tubes which elongate until
they surround the alimentary canal, extending on the other
side of it beyond the mouth where they join, giving rise to
a Y-shaped canal, (c) Tlie ventral ridge containing the
band of cilia becomes prolongated into processes of various
shapes. These processes are arranged with close regard to
bilateral symmetry (Bipinnai^ and Brachiolaria, or bilateral
larval stage). (/) At this point the body of the future
starfish begins to develop from the larva. " On one of the
branches of the united water-tubes the feet or tentacula are
produced as a series of lobes, while on the opposite branch
of the water-vascular canal many small calcareous rods are
elaborated* These rods afterwards form a regular network,
and indicate the dorsal side of the young Adcrias^ (g) At
this stage the larva Brachiolaria shrinks and drops to the
bottom of the water, where it fixes itself by means of its short
arms, (h) That portion of the larva which is more developed
into the true starfish form than the remaining portion, now
absorbs the latter and acquires a conical and disc-like form,
with a crenulated edge. In this stage the organism remains
for two or three years. Then the rays or arms lengthen and
the mature form is assumed.

According to Greef,* parthenogenesis appear to occur in
Urdster rvbcns.

In the Ophiuridea^ the sexes are distinct,! and the genital
organs consist of lobular, pedunculated sacs, which are
situated, in pairs, in the inter-radial spaces of the disc.
These organs pour their secretions into the peritoneal cavity ;
the latter, however, is in communication with the external
medium by narrow apertures situated inter-radially on its
margins. The ova are fecundated in the water, and in that

* Marburg Sitzungsherichte^ 187 1.

t OphioUpU squamata is hermaphrodite.

4l6 PHYSIOLOGY OF THE INVERTEBRATA.

medium the embiyos are developed ; bat in the case f
Oji/iioli'pin riliata, the embryo ia developed within the 1
cavity of the parent. The early stages of the embryolof
development of most Opliiuriderf. are similar to those of otlur ■
EchinodcrviaUi ; nevertheless, in some forms the embryo
passes directly into the adult condition without first beooni'
ing an Echiiiopwiliiini. " Where an Jii:liirwj}{ril.ium stage
exists, the larva is a Pluteus. The dorsal wall of the
body of the embryo exhibits a medium conical outgrowth;
along the course of the ciliated band symmetrically disposed
processes are developed ; and these outgrowths are supported
by a calcareous skeleton, which is also bilaterally sym-
metrical."

In the Echinidea* there are five unpaired ovaries or testes,
which are situated inter-radially. As a rule, they project far
into the body cavity, and are composed of ramified tabnles.
The ducts of the genital glands open externally by five
apertures in the genital plates which surround the apical
pole. The early st-ages in the embryological development of
Echinus are similar to those of the starfish. The iree-
Bwimming larva, however, assumes the Ph'ki's form, and in
this respect it is similar to the Op/iita-iih-a. Tba Flutau
form has eight long slender arms, which are supported byj
calcareous rods extending from the body. The adult form
of Echhius is developed within the body of the larva, the
alimentary canal and dorsal sac (the commencement of
the ambulacra! system) alone persisting. The lar\'al body is
gradually absorbed by the developing and growing Eekiiuu,
the spines and pedicels of the latter increasing in size aodg
number "until the animal assumes the adult form.

It may be remarked that Professor A. Giard t has shdi
that at certain times the genital glands of tJie EcJnnidea
secrete small crystalline concretions of a brownish colour.
These concretions consist of calcium phosphate, which ia._

' Tbe seics are diet i net.

+ CompUa Jlendiu de VAcariiinle ilts .

>f
is

PHYSIOLOGY OF THE INVERTEBRATA.

417

destined to famtBh tlie vitellns and spermatozoa with phos-
phorns — an element which la present in large quantitiea in
the genital products.*

In the Crinoii/fii, the aexes are distinct; and the tubular
genital organs are situated under the perisoma of the
pinnulas. In Ankdoii the ovaries open externally on the
pinnula?, and the ova are discharged by the dehiscence of
the integument of the piunula ; but before leaving the
female Antedoii the ova remain attached to the opening of
the integument for a few days; during that time they are
fecundated. " The testis develops no special aperture, but
the spermatozoa appear to be discharged by the dehiscence of
the integument." The development of the embryo Antcdon
is as follows: After the ovum is impregnated it undergoes
total segmentation — i.v., a morula is formed. It then passes
into a gastrula stage, hatching as a barrel-shaped larva with
four bands of cilia. This larva pasaes through a metamor-
phosis, and ultimately becomes a fixed pentacrinus-like foim
- — i.e., Aiitetioti is stalked when young. After some time,
however, it separates from its stalk and moves about inde-
pendently.

Professor Huxley says that " on comparing the facts of
structure and development, which have now been ascertained
in the five existing groups of the Echiiioihrmata, it is obvious
that they are modifications of one fundamental plan. The
segmented vitellua gives rise to a ciliated morula, and this,
hy a process of invagination, is converted into a gastrula,
the blastopore of which usually becomes the anus. A mouth
and gullet are added, as new formations, by invagination of
the epiblast. The embryo normally becomes a free Ecliino-
pii:diiim. which has a complete alimentary canal, and is
bilaterally symmetrical. The cilia of its ectoderm dispose
themselves in one or more hands, which surround the body ;
and, while retaining a bilateral symmetry, become variously
modified. In the Holothurulea, Aatcrvha, and Crin-oidca,

kBimilar coDcretions are found in the renal organs of man; Inveitebnitef .

4iS PHYSIOLOGY OF THE INVERTEBRATA.

the larva is vermiform, and has no skeleton; in tbe^iAf-'
nidm and the Ojihuiri'lea it becomes ploteiform, and derelope

* special spictilar akeletoD.''

The Trichoscouces.

The Turbrllaria multiply by two methods, (a) transrerse
■fission; (h) by sexual organs. In the smaller H/iaMootla,
the first mode of reproduction is the rule, for no geniul
'Organs are present. These animals are both moncecioos and
■dicEcious ; and the " genital and copulatory organs of both
se:ces are situated upon one and the same individaal so that
they are capable of aelf-impregnation; but there ia generally
a reciprocal copulation." •

In the higher TurhtUaria the female genital organs consis'
■oi the following parta : a germarium which develops ova :
a vitellarian gland in which the vitsllus or food yolk is
formed ; an ovidnct ; a uterus and vagina ; and a spenna-
theca — the function of which is to store the semen after thr
act of coition. The male genital organs consist of a testis.
vas deferens, and penis ; the latter " is often eversible anil
■covered with spines." The impregnated ova are enclosed
within a hard shell. In some genera the hard shell is only
formed on the winter ova, while the summer ova are only
covered by a soft vitelline membrane. The rhabdocceloos
ovum undergoes complete segmentation and tJio emluyo
passes directly into the adult form.

In the marine Ftmiari^, there is no vitellariom, and in
some of these animals the embryo after leading the ovum
■differs considerably from the adult. The Flanarttr are
hermaphrodites, but Flanarin dioiea is unisexual. The Piw-
inchn are nearly always hermaphrodites, and tJie ova and
spermatozoa ai'e discharged externally by the dehiscence of
the integument.

^cnu-rtes is dicecious, and the genital organs (^ and 9)

have the same structure, being sacs filled with spermatosoa

■ Cuitioti has beec obsened in Planari'a, J

PHYSIOLOGY OF THE INVERTEBRATA. 4^9

or ova according to the sex of the animal containing them.
The genital organs are sitaated in the lateral part of the
body between the pouch-like diverticula of the intestine.
They are arranged in pairs along the body and open externally
by paired apertures. The development of Nemertes occurs
with metamorphosis. The following are the stages through
which the embryo passes : (a) Before hatching — egg, morula,
and planula. (6) After hatching — a ciliated larva or PUidium
is formed ; and the adult condition is attained by direct
growth, or by budding out from the PUidium,

In the Rotifera the sexes are distinct, and the male animals
are much smaller than the females. The genital apparatus
of the male consists of a testis, in which the spermatozoa are
produced and stored; the testis opens by a duct situated
near the posterior end of the body, usually on a muscular
protruberance or penis. The male Rotifera are short-lived,
and are only bom into the world to impregnate the ova of
the females. The genital apparatus of the female consists
of a round sac-like ovarium or ovary, filled with ova in
various stages of development, and a short oviduct which
opens into the cloaca. The female produces both summer
and winter eggs. According to Prof. Huxley the winter eggs
are produced parthenogenetically — i.e., without previous im-
pregnation. In fact, he says in regard to LacimUaria that the
winter eggs appear to be " segregated portions of the ovarium."
On the other hand, Cohn believes that it is the summer eggs
which are produced parthenogenetically, while the winter eggs
are impregnated. The egg undergoes complete and irregular
segmentation; then a two-layered embryo is formed. An
involution of the epiblast occurs, giving rise to the primitive
mouth, which remains permanently open. The trochal disc
grows out of the walls surrounding the epiblastic depression ;
and the nerve-ganglion is also produced from the epiblast.
At the bottom of the primitive depression, the true mouth is
formed ; while the oesophagus and the remaining portion of
the alimentary canal are developed from the hypoblast.

A20 PHYSIOLOGY OF THE INVERTEBRATA.

The Tmnaloiffi are nearly always hermaphrodites; aai
the genital apparatus consists of the following parts: the
ovajy, vitellarinm, oviduct, uterus, vagina, common genital
vestibule, testis, vasa deferentia (internal and external), and
the penis and its aac. The ovum, as it passes into the oviduct.
is dovoici of a vitelline membrane, aud the vitellus or yolk is
clear : but after fecundation, which takes place in the oviduct,
a shell is developed and the accessory yolk is added by the
action of the vitellarium. The oviduct, which is ciliated
internally, communicates with a duct which proceeds from
the testis; it also receives the \-itellarLan duct. The oW-
duct then passes into the uterus, which terminates by the
vagina and common genital vestibule in close proximity to.
the male organs. The oval-shaped testis, situated posteriori
to the ovary, does not contain spermatozoa, but sioiply
erauular mass. The external vas deferens comes into contact
with the ovary, and then passes, after several bends, into
the anterior part of the body, terminating in the peni^,
which occupies, in common with the uterus, the geaital
vestibule.

In the case of Aspidcgasli-r (the alrave being an acconot
of its reproductive organs), the embrj-o assumes the Euiult
form without any metamorphosis ; but in other species, the
development ia either direct * or accomplished by a com-
plicated metamorphosis.t accompanied by attematioii of
fjenerationa.

The ova of Afpidtii/aster, as they pass down the oviduct,
ai-e impregnated, " either by the spermatozoa conveyed by
the internal vaa deferens, or by those received by the ^-agina,
when copulation with another individual, or possibly sel^'
impregnation, occurs."

As already stated, nearly all the Trematodn are hi
phrodites, but among those that are dicecious is the parasltio
iiiUiama, which lives in the blood-vessels of man. The
female Bilkarzvi is much smaller than the male ; and a

he
rt

' IVi/ntornvm. Oi/rodacli/tia.

t Diiloma, Stonottomtin.

' seit-'^H

rasitio

The

nd a

J'HYSIOLOGY OF THE INVERTEBRATA. 421

carious mode of pairing occurs — ^for the male, not content to
unite with the female, retains the latter in a gynsecophore
or canal; but it may be stated that very little is known
concerning the reproduction and development of this Tre-
matode.

So far we have seen that the Trenuiioda only multiply
sexually ; but some of these animals also multiply by conju-
gation and by a kind of gemmation. For instance, in the
genus Diporpay two individuals . (devoid of sexual organs)
conjugate, and the result is . a double-bodied ZHplozoon
paradoxum^ which ultimately develops sexual organs.

In the case of (h/rodactyhcSy a kind of internal gemmation
occurs.

The Cestoidea are hermaphrodites in the mature condition,
but in the earlier stages of their growth they are devoid of
sexual organs (i.c, in the cystic form). Some, like Caryo-
phi/llants, have only a single set of hermaphrodite organs ;
and Ligida is an unsegmented form with many sets of these
organs. The Tape-worms are segmented animals, and in
each proglottis or segment there are male and female organs.
The male organ consists of innumerable pear-shaped vesicles
or testes, scattered in the parenchyma of the body. The
vasa efferentia open into the common duct — the vas deferens ;
the latter lies in the cirrus sheath. By the contraction of the
cirrus sheath, the vas deferens (*' cirrus") can be forced
through the vagina.* In this case the vas deferens acts as a
copulatory organ or penis.

Tne female organ consists of the following parts : -:\n
ovary leading into a single oviduct, which has an enlarged
portion or pouch, termed the receptaculum seminis. Branch-
ing out from the oviduct are the vitellaria or yolk glands,
whose efferent tubes ultimately coalesce with the oviduct
forming a common duct. At the point where the ducts of
the vitellaria unite with the oviduct, the shell gland is

* The vagina and vas deferens open into a cloaca or genital vestibule,
which is situated on the lateral margin of the proglottis.

422 PHYSIOLOGY OF THE INVERTEBRATA.

attached. This gland secretes a substance which becomes
the investment of the ova. The tenninal portion of the
ovidnct passes into the ntems. The vagina is usnally a long
canal, and at its inner end is the receptaculnm seminis.
The small ova are either oval or round. They are formed
by three glands — ^the ovary, vitellarium, and shell gland.*

As already stated, the Tape-worms are composed of many
segments or proglottides, and at the end of the body the
segments become detached. In this condition they retain
their vitality for some time. The uterus of the prc^lottis
contains very many ova; and the embryo (ciliated or
hooked) is developed in a similar manner to that of the

The Tape-worms live a portion of their life in one animal
(cystic condition), and the other portion in an entirely different
one (cestoid condition). For instance, the following diagram
illustrates the life-history of Taniia solium, which infests
man : —

Taenia id man
(sexual condition).

Cystic form in pip /_ _\ Six-hooked or ciliated

(measly pork). embrjo.

*' The Tape- worms are rarely met with in both the cystic
and cestoid conditions in the same animal ; but the cvstic
form is found in some creature which serves as prey to the
animal in which the cestoid form occurs."

The A>'>elida.

The Mi/Zi\^o}th*t an? small unsegmented worms, parasitic
on Coiiwtula (Antuion). These animals are hermaphrodites.
The two oviducts open into the cloaca ; and the male organ

• The m-anr forms the nnclens, the viteUariam the yolk, and the shell
gland the external corexing of the egg.

PHYSIOLOGY OF THE INVERTEBRATA, 423

opens externally by separate dacts — the vasa deferentia — on
each side of the ventral surface of the body.

The Oephyrea are also unsegmented worms, but they are
dioecious (i.6., the sexes are distinct), and the spermatozoa and
ova are developed from the epithelial cells, which line the walls
of the perivisceral cavity, or they are developed in simple
caacal glands. The earlier stages in the development of these
animals are similar to those of the Oligochccta and Polychceta^
The adult state is attained from the embryonic condition by
a metamorphosis. In the genus Bondlia, the males, which
are minute, rudimentary, and Planarian-like, live in the
uterus of the female.*

The Hirvdinea are hermaphrodites.! The male organs of
Hirudo consist of nine pairs of testes, situated in successive
segments. The first pair are in the segment behind that
which contains the eversible penis ; and the others are in the
following eight segments, a little in front of the nephridia or
segmental organs. From each testis a duct passes into the
vas deferens (situated laterally), which, in front of the anterior
pair of testes, becomes much coiled, forming the vesicular
seminalis. The latter opens into a duct, which passes for*
ward to the ventral median line, and, along with the same
duct of the vas deferens of the other side of the body, opens
into the prostate gland. A duct proceeds from the prostate
gland, which forms a sheath of the eversible penis, and opens
in the twenty-fourth segment. The spermatozoa are enclosed
in a case, called a spermatophore. The female organs are
situated in the segment behind that which contains the penis.
They consist of two small ovaries provided with oviducts ; the
latter open into the uterus, which is surrounded by an albumin
gland. The uterus proceeds into a vagina, which opens by a
small orifice situated between the twenty-ninth and thirtieth
segments. It will be noticed that the external orifices of the
genital organs are unpaired.

* This is different from BiUiarzia (one of the Trematoda), for the male
retains the female within its own body.

t Except HiitrichddLa and McUacobdeUa, which are dioecijus.

424 PHYSIOLOGY OF THE mVERTEBRATA.

The impregnation of the ova takes place within the body;
and the ova, when laid, are enclosed in a cocoon which is
secreted by the integument. Although these animals are
hermaphrodites, copulation between two separate individuals
takes place. "The female copulatory organs are upon the
ventral surface of the anterior part of the body, and behind
tlie male organs — so that two individuals, by placing together
their anterior ventral surfaces in an inverse position, can be
mutually impregnated." (Von Siebold.)

The ovum of Hirudii passes through a metamorphosis, Uls
raesoblast undergoing division into segments, which altiiiiat«ly|
give rise to the characteristic structure of this and other eef^ J
mented animals.

The UUgocliaita are hermaphixxlites ; and the genital organil
are situated (like HiTudii) in the anterior part of the bodf*l
In the fresh-water OHijiKhivtii (aVfj-fand ri^^'i/V-r), these organi I
Lave no genital ducts, but the o\'a and spermatozoa are can- 1
veyed outwai-ds by the nephridla. which are situated in tboas J
segments of the l»ody containing the genital glands. "In*
JVdi-s and Ck(f(oi/((stcr, agamic multiplication occurs by t
development of posterior segments of the body into zooida^ '
which may remain associated in chains for some time, but
eventually become detached and assume the parental
form."

In Lumhrkiis, the testes are two pairs of white sacs sitnated
on the posterior sides of the septa, separating the ninth and
tenth, and the tenth and eleventh segments. The spermatozoa
are not fully developed on leaving the testes, and they are
known in this condition as spermospores. The spermospores
are further developed by a process of budding, which takes
place in the veeiculEO semiuales (two pairs of reservoirs). The
fuily developed spermatozoa (Fig. 76 «) are conveyed out-
wards by four ducts — the vasn deferentia ; but the two vasa
deferentia on eitlier side of the body unite, forming one duct,
which opens on the ventral side of the fifteentii segment.
The female genital organs consist of a pair of small ova:

ovan^^

PHYSIOLOGY OF THE INVERTEBRATA. 425

(^ in. long), sitaated in the thirteenth segment. The ova
when fully developed rupture the walls of the ovaries, and
pass into the body cavity. Ultimately the ova find their
way into the oviducts, which are quite distinct from the
ovaries. The pair of oviducts are small, funnel-shaped,
ciliated tubes ; the funnel-shaped portion opens internally
in the thirteenth segment, whereas the opposite end opens
externally by a small aperture on the ventral side of the
fourteenth segment.

Although Lumhricus is hermaphrodite, copulation takes
place between two separate individuals, the impregnating
seminal fluid being stored in four small spherical sacs or
spermathecae, which open externally between the ninth and
tenth, and the tenth and eleventh segments. The ova are
impregnated externally by the seminal fluid from the sperma-
thecsB. Groups of these ova become surrounded by mucous
and chitinous secretions termed cocoons. These cocoons
sometimes contain forty or fifty ova, an albuminous substance,
and packets of spermatozoa. In the development of the
Oligoc'hrrta, the segmentation of the ovum is total and nearly
regular, giving rise to a flattened ciliated blastosphere. The
latter invaginates, and a gastrula is formed; and between
the epiblast and hypoblast in this stage of the development a
mesoblast is formed. " On the ventral side of the embryo,
the mesoblast divides into a row of quadrate masses, which
are symmetrically arranged on each side of what becomes the
median line of the adult body. This series of symmetri-
cally placed quadrate masses resembles the protovertcbraD of
the embryo of a Vertebrate animal." After this '* a cavity
forms in the interior of each quadrate mesoblastic mass,
making it into a kind of sac. The adjacent anterior and
posterior walls of the row of sacs unite, and this union gives
rise to the dissepiments of the somites, while the cavities
become the body cavity or perivisceral chambers." (Johnstone.)
The epiblast now thickens inwardly, along the median
line, ultimately giving rise to the ganglionic nervous

426

PHYSIOLOGY OF THE INVERTEBRATA.

system.' The nephridia or segmental organs bej

growths from the posterior face of each septnm ; and finally

the adult form is attained just before the hatching of the egg.

The Polychcria are ditecious and rarely herm aphrodite. t
Some of these animals multiply by fission and gemmation. 1
In ^ylHn, transverse fission takes place; while in MifrianiJimim
gemmation occurs giving rise to zooida. In some otbccJ
Polycbietous forms reproduction is produced by a oombinstiaa 1
of fission and gemmation.

The genital organs of the Folyehfi:ta are very simple
structure, aud the genital products nltiniately float about in J
the perivisceral cavity, probably passing outwards through tb». J
apertures at the bases of the parapodia. In some PoiyehaiaM
the nephridia act as genital ducts. The ova of these &
undergo a somewhat similar metamorphosis to those of t
Oligocjutta and Hh-udinea ; " but the embryos of the Pdyc
differ from those of the Oligochcda and Hirudinea in 1j
ciliated."

The Nematoscolices.

The Nanatoidm are nearly all dicecious, unsegmented
worms.! These animals and their genital products are poe-
eessed of great vitality. According to M, Devaine, the ova
of Ascaris luvihricoidcs^ are capable of withstanding
action of a solution of chromic acid (2 per cent.) for
years; and Mr. W. Carmthers, F.R.S,, states that vitalil
was restored in some Nematodes, after they had been in the
botanical department of the British Museum for more than
thirty years. ||

• The nersons system, almost Ihroogbont Iho animal bingdu
epiblastit^ origin.

f Protvia is hermaphrotlite.

t Ptlodi/tet is hermaphrodite ; awl A/earli nlgrovenota, which .
dnces Epermatoxoa, afterwarda only produces ovtL

S The ft/Jii'c arpoyyiXne at Hippocratea.

I See Dr. Griffiths' iJ/.rn.t* of C^op., pp. iS and 119.

PHYSIOLOGY OF THE INVERTEBRATA. 427

As a rule, the male organ consists of a single caecal tube
opening on the ventral side into the cloaca or the posterior
end of the intestine. The spermatozoa,* which are amoeboid
in shape, are developed from the blind end of the caDcal tube,
whose remaining portion has the function of a vas deferens.
One or two, sometimes long, chitinous spicula are developed
in the cloacal region of the male. These spicula are used by
the male during copulation — the object being to distend the
vulva of the female, in order to allow the seminal fluid to
pass freely into the vagina and uterus. The spermatozoa
undergo further changes in the female organs of reproduction,
but ultimately fuse with the ova.

The female organ consists of a single or double tube, which
is blind at one end. The blind end of this tube contains
internally a protoplasmic substance or rhachis, from which
the ova are developed ; this portion of the tube is, therefore,
physiologically the ovary of other forms. The tube then
becomes difEerentiated into an oviduct, and later into a
uterus. The ova are free in the oviduct, and they are im-
pregnated in the uterus, where they become surrounded by a
hard shell. The uterus then passes into the vagina, which
opens on the ventral surface, usually near the centre of the
body.

The vitellus of the fecundated ovum becomes segmented,
and gives rise to a single row of cells, which ultimately
become indented on one side — i.e,, the ovum forms a kind of in-
vaginated gastrula.f The body wall and the alimentary canal
are developed from two layers of cells, which are produced by
the invagination of the above-mentioned single layer. At
this point the embryo rapidly assumes the adult form ; and
is found rolled up within the shell. After hatching, the
young Nematode casts its cuticle, which is shed a second
time when it acquires its sexual organs — i.e., there is a period

* In the Nematoidea^ the spermatozoa retain the character of ceUs.
t The ova of Ascaris dentata and Oxyuris ambigtta are unsegmented after
fecundation.

438

PHYSIOLOGY OF THE ISVERTEBRATA,

in which the Nematoulta are sexlesB woiins. In the genen
Mermis and Gonlius, the anterior onda of the embry<M are
provided with Bpines— the spines being used to pi<«"ce holes
in the bodies of insects, in which tbege Nematodes live a
portion of their life-history. According to Sir John Lubbock,
the male of Sp/iwritlaria beconiPS permanently Cxed to the
female. Many of the Nematodes are only parasitic in tbe
sexless stage of their t-xistence ; but some are free in the
larval or sexless stage ; and some again are parasitic both io
the sexless and sexual condition.

In the Aranthocephfda — represented by EchinorhynehiU—
the genital organs are attached to the pc®terior end of the
proboscis sheath by the ligameotum suBpensorium, whicli
traverses the body cavity. The sexes are distinct. The
female organ consists of a tubular ovary ; a uterine bell — the
mouth of which opens into the body cavity, while the upper
portion leads into the uterus; the uterus then pasee
into the vagina, which opens externally at the posterior
end of the body. The ova, discharged from the ovajy into
the body cavity, are ultimately taken up by the mouth of the
uterine- bell, which is continually expanding and contractiaff,
and thence the ova pass into the uterus. The male organ
consists of two oval testes provided with vasa deferentia. which
proceed to the posterior end of the body. At this jmint the
vasa deferentia fuse together, forming a bulb-like structure,
called the ductus ejaculatorius, which ia usually provided
with six or eight glandular sacs. The ductus ejaculatorius ia
furnished with a long penis placed in the centre of the
bottom of a bell-shaped bursa situated at the posterior end of
the body. The development of the fecundated ovum com- ■,
mences with an irregular aud a complete segmentation,
gives rise to an embryo, which is enclosed in the membra
The embryo, at this stage, is provided anteriorly with '
small spines. The ova (containing the embryo) are usually
"swallowed" by various Amphipotla, Isupala, and Intecia
(larvae); in this stage the membranes are dissolved by t

■u cum- ij

ibrftneaJH
y wit* "
usually
Intuia
ed by th^H

PHYSIOLOGY OF THE JNVERTEBRATA. 429

secretions of the alimentary canal, and the embryos becoming
free, bore their way throngh the walls of the intestine of
their host. While in the alimentary canal of the host, the
embryo loses its spines, and develops into an elongated larva.
In this condition, the skin gives rise to the muscular body
wall, the dermal vessels, and the lemnisci of the adult ; all
the other organs are developed from the " embryonic nucleus,"
which makes its appearance early during the embryonic
development — i.e., before the ovum is " swallowed " by one of
the above-mentioned Invertebrates. Finally, the embryo finds
its way into the alimentary canal of one of the Verteh^ata
(e.g., fishes, aquatic birds, pigs, &c.), and while there, it
develops sexual organs.

The CHiETOGNATHA.

This group contains only one genus — Sagitta, These
animals are hermaphrodites ; and the male and female
organs are situated at the sides of the posterior end of the
body. There are two tubular ovaries, the ducts of which
open externally on each side of the anus. The tubular testes,
situated behind the ovaries in the caudal region of the body,
open by short ducts at the sides of the tail. The fecundated
ovum becomes completely segmented, giving rise to a blasto-
sphere. By invagination, the hemispherical, two-layered, cup-
shaped gastrula is formed. The primitive opening now closes,
and a permanent mouth is formed at the opposite end. At
this point the embryo has an oval shape, but it finally elon-
gates and acquires the adult form before leaving the egg.

The Onychophora.

Professor H. N. Moseley* has shown that in Peinpatvs the
sexes are distinct. The testes are egg-shaped ; and they are
provided with coiled vasa deferentia, which ultimately unite,
forming a common duct. This duct opens on the ventral

* Phxlo9ophical Transaeiions of the Royal Society , 1874.

430 PHYSIOLOGY OF THE INVERTEBRATA.

side of the rectum. Like the testes, the ovary is sttnoted in
the posterior end of the body. It ia k small, single, bilobed
organ provided with two long oviducts, which unite brfon
passing into a short vaginft. The vagina opens externally on
the ventral side of the rectum. The oviducts are provided
with uterine dilatations, and in these the ova are developed.
PcripcUus being a viviparous animal. For details conoeming
the development of 2'cnpatiie, the reader is referred to
Moseley's original paper, already cited.

The Myriapoda.

The Myriapofia are dicecious. The testes, in the ChiU^li,
assume various forms ; but in most of these animaU, the test^
are said to be " fusiform acini united by delicate ducts wilh a
median vas deferens ; and two, or four, pairs of acceMoir
glands are connected with the opening of the male apparatus."
According to Favre," the testis, in Ll/fiohiu,s, is a single tube
connected with the vas deferentia, the latt.er being situated
on each side of the rectum. A veeicuta aeminalis opens into
each vas deferens.

In the ChiJot/natha (Diplojxida), the tnbnlar testes are
situated between the alimentary canal and the nervons
system. The testes are provided with lateral tubnh-a, the
former being connected with the latter by transverse ducts.
There are two penes connected with the bases of the seventh
pair o£ legs. In Scolopemlm (centipede), Get^/iHun, and
C'ri/ptops, the spermatozoa are enclosed in spermatophoreit.

In both the Cliihpoila and Ckiloi/nnJJdi , the ovary is a Ii
single tube. It is situated above the alimentarj- canal ii
Chili/poilii, and between the alimentary canal and the nervous
system in the Chilo'/nntka. The female organ in each order
is provided with double va^nie, which open beneath the anu?
in the Chilopmln, and behind the bases of the second pair of
legs in the ChiingnfitJia. Two spermalhecie are genej»lly
present in the Mt/rifijxxfn,

• Anniittii<le» Scitncf XiUurtUa, 1855,

PHYSIOLOGY OF THE INVERTEBRATA. 431

"The ChUogncutha copulate. In Glomeris and Polyxenus^
the genital apertures of the two sexes are brought together
during copulation ; but in Julus^ the penes of the male are
charged with the spermatic fluid before copulation takes place,
and it is by their agency that the female is impregnated.
The ChUopoda have not been observed to copulate, indeed the
female shows a tendency to destroy the males, as among the
Araneina. The male GeophUtcs* spins webs, like those of
spiders, across the passages which he frequents, and deposits
a spermatophore in the centre of each."

The development of the embryo of the Myriapoda has
been worked out by Metschnikoff,t whose papers the reader is
referred to for important information.

The Insecta.

The iTiscda multiply by means of genital organs, and the
sexes are distinct. According to M. Lacaze-Duthiers, { the
copulatory organs in these animals present wide and manifold
variations. Among the colonies of ants, bees, and wasps,
besides the males and females, there are large numbers of
neuter individuals. The sexual organs of the Insecta are
developed chiefly during the pupal stage ; but the rudiments
of these organs exist in the larvae — e,g,, the female genital
organs exist in the larvae of Apis, and it is due to an increase
in the quantity of nourishment that the larvae become females
or queens.

Among the Aphidce, parthenogenesis occars; for many
successive generations of females are bom viviparously with-
out copulation with the males.

As a typical example of the genital organs in the Insecta,
we describe in detail those of Feriplaneta (the cockroach).
The male organ consists of numerous short testicular sacs
attached to a short vas deferens. It is situated above the

* Belonging to the ChUopoda,

t Zeitschrift fUr Wtsaensehaftiiche Zooiogte, 1874-5.

X Annates de$ Sciences Naturelles, tomes 12, 14, 171 18, and 19.

J'HYSIOLOCV OF THE JNVERTEBRATA.

posterior abdominal ganglion. The anterior end of the vw
deferens ia dilated ; and this dnct in the adult male alwayx
containa siwrniatozoa. The spermatozoa appear to be formecl
in the testis or mushroom -shaped gland of the young, and
then accumulate in the vas deferens, for in the adult cock-
roach the testis atrophies.

The two ovaries, each of which consists of eight tubnlf
are situated in the posterior part of the abdomen.
ovarian tubes or the contracted portion of the ovaries
into two short oviducts. The two oviducts unite in the
middle line of the body, and open externally by a verj- abort
but wide vagina. Behind the union of the oviducts with the
vagina, there is the spermatheca or seminal receptacle ; and
behind the latter are two much-branched tubular colleterial
glands which secrete the chitinous substance of the e^-cases.
There are sixteen eggs enclosed in each case, " The feini
carries the egg-case about for a week or more, bef<
depositing it. The young leave the eggs as minute actii
insects, colourless, except for the large dark eyes." P<
plaiiftri does not pass through any pupal stage ; but undei
seven ecdyses or moultings of the skin ; and attains
mature condition during the lifth year.

The penes or male copiilatoiy oigans in the Insecta
often very complex in structure. "Kraepelin,* who
examined the development of these parts in the Drone,
the modifications found in hermaphrodite Bees, is led to the
conclusion that they are developed from the eighth and ninlh
somites of the abdomen, and therefore are the homologues of
the parts of the sting in the female. In the male Bl<Uta
(Periplanela), however, it is obvious that the male copi
apparatus belongs to a more posterior somite than that
which the female gonapophyses are developed.

In most Insecta, the vitellua of the ovum undergoes only

partial segmentation ; but in some Poihiriiia segmentation is

complete. During the development of the embryo, there are

• Zt!tKhrift far Wit: ZotAoqie. 187J.

TbH
pai^

liat nptjjH

ws only
itation is
there are

PHYSIOLOGY OF THE INVERTEBRA7A. 433

certain parts * which are comparable to the ammon of the
VertebrcUa. This amniotic investment is not, however,
universal among the Irisecta, although it is present in the
Orthoptera (Idbellula), Diptera^ Lepidoptera, Hymenoptera^
ColeopterUf and Heniiptera.

As material agents in the propagation of the Insecta, the
following may be mentioned : their odonrs, colours, dances,
and music. For instance, (i) in some Lepidoptera^ there are
two glands, situated near the opening of the vagina, which
secrete an odorous substance that excites copulation; and
one could give many examples where odours play an
important part in the amours of various insects^ (2) Female
Libellvlce and flies with bright metallic colours may often be
noticed reposing on plants in the sunshine, " attracting ever
and anon the attention of some passing male, who, staying
his course, remains for a while, as seized with an ecstasy,
suspended over their charms like a hawk marking his
quarry, and seeming as if dazed by the glow of pigment
beneath him. This is very characteristic of the Libellvlce
and SyriphidceJ^ In other insects it is the males which have
the gorgeous colours. (3) The aSrial dances of certain
IHptera, Lepidoptera^ Neuropteraj &c., are said to be means
favouring copulation. The males of some Neuroptera dance
and collect, and when joined by their attracted females they
pair. (4) Stridulation or instrumental music is a character-
istic phenomenon in many insects. " The musical organs
sexually common in most beetles, butterflies, and moths, as
in a grasshopper genus, assume generally masculine differ-
entiation in the Orthoptera^ indicating dermal alteration and
induration ; they are either duplicate, paired, and similarly
situate as regards the bodies' median line, or their develop-
ment is single, as the alar organ of leaf-crickets, or quasi
unique, as in the family of bugs, and the longicom beetles.
Reciprocating stimulatory friction of articulate parts to

* The lamina of the sternal band,
t Argynnis, Zygnasna, Meiitcea.

2 E

434 PHYSIOLOGY OF THE INVERTEBRATA.

express emotion postulates aijaptive acquisition, conseqaent
on asaumed integumental tendency under attntion to
determine a smooth undulatory surface, and propagation bv
hereditary transmission ; a rudimentary structure of ttis
description exists in t!ie Stag Beetle at the inferior and pos-
terior extremity of the head ; and whenever a number or
group of insects is capable of music, we may establish a
degradation of the organs almost invariahly in mute indi-
viduals of the opposite sex, or in other members of the genus
or family, Practically, the microscope establishes the essentild
constituent, the file (lima), to be a dermal or stin excrescence,
with a systematic exaggeration or coalescence of extemi^
callosities, wrinkles, tubercles, or a protrusdon of the spiral
thread of the wing-veins or other tracheal organ. Theo-
retically, this active or passive source of sonorous vibration
is a variously-placed more or less /-shaped tumour, provided
with denticulationa more or less regular, which are vibrated
and sounded diagonally over a narrow raised callosity or
ridge, on the chitinous integument or modified alar vein.
These latter, constituting the passive or active clasping organ,
assnme the function of a violin bow or plectrum.'' Many of
the musical sounds emitted by insects are said to express
fear, anger, and " the more complex emotions nf love and
rivalry, causing, at certain seasons, the music to assume the
character of a stimulus to reproduction and migration,"

"The action of stridulation with the majority of beetles
and one of the bee group is a more or less rapid protTDEion
and contraction of the abdominal segments, a respiratory
movement which we shall show results from tracheal dis-
position in the Inscda. In some moths and grasshoppCTS,
music ia implicated with a bladdery inflation of the d;iii
but in other insects it is not directly dependent
tion. With some the action is a sharp nid-nodding,
performed by the elevator and depressor muscles of the
prothorax or head, .Many butterflies and the crickets pro-
du<« their music by wing friction, resulting from a

loppera, J
respim^^B

>m a rapld^H

PHYSIOLOGY OF THE INVERTEBRATA, 435

movement of the extensor and deflexor muscles; and the
grasshoppers to the same end employ the subtile elevator
and depressor muscles of their agile leaping legs."

The following table gives the orders of the Iiisecta which
possess the power of emitting musical sounds : —

SiXKB, &c.

Certain genera of the CoUoptera

both sexes stridulate

! „ „ „ Orthoptera

(male stridulates, the
1 female is mute

„ „ „ Hemiptera )

(ffeteropterd))

both sexes stridulate

1 „ „ „ Ifeinipttra* )
1 {Homoptera) !

vocal music

j „ „ „ Hymenoptera

both sexes stridulate

' „ „ „ Lepidoptera

both sexes stridulate

„ „ „ Diptera (7)

male stridulates (7)

Many sounds emitted by insects are certainly not musical
to the human ear ; nevertheless, as the latter is only capable
of appreciating sonorous vibrations within narrow limits, the
sounds produced by the Insecta may be musical to them ; at
any rate these sounds have their uses, or the organs which
produce them would not be so well developed as they are in
the Insecta, If many of us are incapable of appreciating
insect music, the ancients, and especially the Greeks, appear
to have regarded it with feelings of great satisfaction ; and
the Cicada is often referred to by certain Greek poets.
Anacreon, for instance, has devoted an ode to singing the
happiness of this insect. An element of this happiness,
according to Zenachus, is, that the Cicadas f *' all have
voiceless wives," an opinion which will probably find sup-
porters in the present day.

Besides stridulation, many insects produce sounds by
means of their wings (wing-beating), and stigmata, spiracles,

* Various Oicadce^

t For a fuU description of these insects, see Buckton's Monograph of the
British CicacUe or Tettir/idcs.

436

PHYSIOLOGY OF THE INVERTEBRATA.

or "breatliing-slits." These aonnde are said to giveriaeto
various emotions — fear, anger, and love; consequently tLi-
musical sounds produced by '" wing-beatiug " and tlie " vocal
organs " are material agents in the reproduction of many
Itt^rHa; for it should be borne in mind that those females
which are mute always "alight near"* the musical males,
and many insects (of either sex) know the particular oMee
of their kind.f

From what has been said in the last few pageB, it will be
seen that odours, colours, dances, and music are important
agents in bringing about »cj:ual reproduction in many ordei*
and genera of the Inncda,

We now consider the subject of parthenogenesis or virginal
reproduction, which occurs in certain insects. In Chtnitt*
abictis and Coccus heiqKndum, the females produce ova whidi
give rise only to females, for no males have been discovered.
In the Aph ido: both sexes are developed in the antnmn ;
these copulate, when the females lay eggs, which are batched
in the following spring. But instead of producing individuals
of both sexes, these eggs give rise only to female insects,
which produce living young (vithout any congress with the
male; the brood thus brought forth again produces living
young in the same manner, and this goes on throughout the
whole summer, without the appearance of a single male
insect. In the autumn again, male and female individuals
are produced, the latter lay eggs which are to continue the
species until the following summer. The production
par then ogenetic females has no definite limit, but is regnli
to a certain extent by temperature and food supply,
retain the part hen ogenetic function, the Aphiiia- reqnt
warmth and a plentiful sujiply of food ; for on the faili
either of these conditions the parthenogenetic females gi'
rise to both males and females. The genital organ of k'

" Darwin's Bcteeni of Map, vol, i, chap. lo.

+ For farther JnfonuatioD, se« Snictoa'a tnirpl Variety, pp. 101-339; "'^
Von Siobold's Jni-erltlrata, ]>. 406.

.PHYSIOLOGY OF THE INVERTEBRA7 A. 437

paithenogenetic or viviparous female is different from the
oviparous form; for in the former the spermathecae and
colleterial glands are entirely absent, whereas these organs
are present in the latter.*

"The unimpregnated, apterous, caterpillar-like females
of the Lepidopterous genera Psyche and SoleTiohia^ lay eggs
out of which only females issue. The males occur but rarely
and locally, and, from the impregnated eggs, males and females
issue in about equal numbers." Among ants, wasps, and
humble-bees, the ovaries of the neuters often contain ova ;
and in the two last-mentioned insects these ova give rise to
young (sex ?).

In PolistcH fjcdlica the so-called neuters (?) lay ova,
which develop only male insects; and the unimpregnated
females of Nematus ventrkosus lay ova which give rise to
males.f

Parthenogenesis among hive-bees is an established fact;
the young unwedded queen-bee lays ova profusely, but all of
them give rise to males or drones. The impregnated ova,
however, give rise to females, which become either queens or
neuters, according to the supply of food given to them. If a
queen-bee dies, the inmates of the hive feed a selected
female larva on " chyle-food," elaborated in the so-called
chyle-stomach of the nurses, until it assumes the pupal change,
from which it emerges a perfect female. The future worker
or neuter is weaned on the fourth day, and fed henceforth on
honey and digested pollen, with the result that its ovaries
are rudimentary and sterile, while its further genital struc-
ture renders it incapable of mating. The fecundation of the
queen-bee takes place within a few days of her quitting the
cell, and lasts for life ; the millions of spermatozoa dis-

* See Prof. Huxley's paper in Transactionn of the Linnean A^i'eti/, 1857 ;
Halbiani's paper in Annales den jSciences Naturcttest 1869-72; and Von
Siebold's Anatomy of tfte Invertebrata,

t Parthenogenetic females which produce male young are termed arren-
tokous, while those which produce female young are termed thelytokous*

438 PHYSIOLOGY OF THE INVERTEBRATA.

obarged by the males are retained in tlie spermathecs of the
qneen-bee, and they only escape one by one to fertilise each
omin as it is laid.

Insects in their most complete character pass throogh four
stages of existence — -the ovum, the lan-a, the pupa, and the
imago. In none of these, except the larval stajje, does the
insect increase in size. Some insects {Aftcrn) pass only
three stages — the ovnm, tlie "younger stt^e," and the
imago ; and in others the perfect state or imago, is attuned
without passing through more than two. The ova of insects
are usually deposited externally (this deposition in many
cases being assisted by an ovipositor), but in some few cases
they are hatched in the body of the parent. In the larval
stage, the insect moults several times, and after each ecdyais
attaining a sudden and rapid increase in size. The larva
does not always take the form of a grub or maggot ; for in
the Aptrm, Hi^mipti-rn, and OrthopttTn, it assumes a good
deal of the appearance of the perfect insect. In this imperfect
metamorphosis it changes its skin as the maggots do, and it
does not assume a different form for the pupal stage. In
the jyiptrra, Hymcnoptern , ^ritnyplrro, Lrpi<loj)tera, and
Colfoptrrf, the larva", on their last change of skin, assume
the pupal stage, in which they remain dormant until the last
change takes place, when they come out as perfect inaects.
In some cases the pupce remain on or in the earth ; while ia
others, cocoons or cases are made by the larva? in which they
pass the pupal stage.

In concluding our remarks couceming the modes of rft-
production and development in the Inseclx, it may be stated
that a very full account of the genital organs and their
countless modifications in the various orders, genera, &c, ar»
given in Von Hiebold's Anatfivii/ of the Iiivertehrota,' to which
the reader is referred,

" This is one of tbu best books on tbe snbjetl

PHYSIOLOGY OF THE INVERTEBRATA. 439

The Arachnida.

In the Pentastomida, the ovary of the female is a large
sac-like organ, with oviducts which pass off from its anterior
end. The oviducts terminate in an aperture situated near
the anus. The ova are developed in the ovary. The testis of
the male is situated on the ventral side of the intestine. It
is provided with two vasa deferentia, which pass in an
anterior direction, and terminate in two dilatations, which
contain long, chitinous penes (i.e., a penis in each dilatation).
These animals are parasitic, and the parasitism is almost
similar to that of the Cestoidea — e.g,y Pentastomum denticvla"
turn, which is sexless, inhabits the liver of rabbits and hares ;
but in the sexual state this parasite, known as Pentastomum
tceniaideSy infests the nasal cavities of wolves and dogs.

In the Ardisca or Tardigrada, the sexes are not distinct,
for these microscopic animals are hermaphrodites. The
ovary is a sac-like organ, situated oil the posterior half of
the digestive canal, and opens into the cloaca, which is a
dilatation of the rectum. The ova of Emydium^ Milnesium^
and Macrobiotus nrsdliis are invested by a chorion, and they
are deposited in an ephippium, which is in reality the cuticle
of the parent. The vitellus undergoes complete segmentation,
but there is no metamorphosis.*

The Pycnogonida are dioecious, and *'the testes and ovaria
are lodged in the legs and open upon their basal joints. The
embryo emerges from the egg as a larva provided with a
rostrum, and with three pairs of appendages, which represent
the short anterior three pairs in the adult. (A. Dohm.) The
four pairs of great limbs of the adult are produced by
outgrowths from a subsequent posterior elongation of the
body."

In the Acarina^ the sexes are distinct. The male organs
are formed on distinct types. The testes of Ixodes, for

♦ See Kanfmann's paper in ZeiUchriftfUr H ?>»)». Zoologle, 1851.

440 PHYSIOLOGY OF THE INVERTEBRATA. ■

instance, conBiat of a group of five pairs of follicles wlua^
unite in the abdomen. There are two vasa deferenfia wUicli
terminate in the base of the so-called chin-like process. The
male introduces this process, together with tbe chelicpw,
into the vagina of the female daring copulation. In Tnm-
Mdiuiii, the testis consists of twenty follicles attached to a \i«
deferens which opens between the posterior legs. AlthoDgh
there are twenty follicles comprising the testis of TromJruIium,
that of Gamastis has only two ; but each of these litis its own
vas deferens. Many Aearinn (c.;/., Orihaies, BdcUn, Gtrtiuttiu)
possess a penis, which is situated in a similar position to that
of the vulva of the females. As accessory oi^ans of repro-
duction, some of the legs are usi-d by the males to retain tie
females during coition. The female organ consists of a paJr
of ovaries, whose duets opf-n in a common vulva situated, a» *
rule, in the middle of the abdomen on the ventral wdo o(J
the body. In Gama-iu-f and Ixodes, the genital aperture i
situated on the thorax. The two oviducts of Lrrx/rs rirint
open into a pyriform uterus, whose neck, according to Vol
Siebold, communicates laterally with a large caBcum com
from the vulva. The ctccum is a rt'ceptacle for the spem
fluid during copulation ; which, after the act, flows into thfl
uterus and oviducts. This cajcnm is also in connection «
two small glands, filled with transparent cells, which secretdtl
substance for enveloping the ova.

The oviduct of many Aenrina opens into a protractile
ovipositor^an organ used in depositing the ova under tic ,
epidermis of animals or plants. Most of the Acarii
oviparous, but the Oribn/uh- are viviparous. (DajardiikllQ
There is no metamorphosis in these animals, except f
HydrndiiKi and TromhuHvvt. In the latter genus, '
hexapod larvfO are attached to flies, grasshoppers, plant-llM
and various other terrestrial insects."

In the Arnneiiui the sexes are distinct. The testis of t
male consists of two long creca situated between the so-caQc^
"hepatic" lobes; and from them lead two vasa deferentis|

PHYSIOLOGY OF THE INVERTEBRATA. 44i

which terminate in an aperture situated at the base of the
abdomen. There is no penis, for these animals use their
palpi * to introduce the spermatophores into the vulva of the
female. The female organ consists of two ovaries, situated
(in the female) in the same position as the testis in the male.
They open by two oviducts into a vagina situated between
the pulmonary sacs ; and the vagina opens externally
" after having previously received the excretory ducts of the
two contiguous receptacula seminis. The females surround
their eggs in groups, with a web." The Arancitm^ are
oviparous and, according to Clapar^de, there is no metamor-
phosis.

As already stated, the male spider applies his palpi con-
taining spermatophores to the genital apertures of the female ;
this is due to the fact that the female spider is prone to slay
and devour the male. " The young and inexperienced male,
always the smallest and weakest of the sexes, has been known
to fall a victim, and pay the forfeit of his life for his too rash
proposals. The more practised suitor advances with many
precautions, carefully feels about with his long legs, his
outstretched palpi being much agitated; he announces his
approach by vibrating the outer border of the web of the
female, who answers the signal, and indicates acquiescence
by raising her fore-feet from the web, when the male rapidly
approaches; his palpi are extended to their utmost, and a
drop of clear liquid exudes from the tip of each clavate end,
where it remains attached, the tips themselves immediately
coming in contact with a transverse fleshy kind of teat or
tubercle protruded by the female from the base of the under
side of the abdomen. After consummation, the male is
sometimes obliged to save himself by a precipitate retreat :
for the ordinary savage instincts of the female, ^ ctiam in

* The palpi take up the spermatophores from the genital aperture.

t Concerning the development of the Araneina^ see Kamakichi Kishin-
ouye's paper in Journal of College of Science^ Imj)erial Univernity of Jajmn
(Teikoku Daigaku), vol. 4.

442

PHYSIOLOGY OF THE INVERTEBRATA.

autwihus saia,' art' apt to return, and she has been known tl
sacrifice and devonr her too long tarrying or dallying Bpouse." *
In the Artkrogirslrn the seses are distinct. There M*
three (?) ovaries consisting of many tubules united hy tran^
verse anastomoses ; and two o\-iducts which unite in a short
vagina opening near the base of the abdomen. According:
to Meckel, the oviducts dilate into a receptaculum Bemiuis
before uniting with the vagina. The testes terminate in two
vasa deferentia, which unite before opening at the gvnital
aperture, the latter being situated at the base of the abdomen.
Just before the vasa deferentia unite, they receive two kmg
and two short aeca ; these organs have the function of
vesiculffi seminales. There is a rudimentary penis, in the form
of a small papilla which projects out of the genital apertnre.f
Unlike the Araneiii", the palpi of the Artlirofja^ra take no
part in coition. The ArUirogasim are viviparous, the embijoj
being developed in the ovaries ; and in Sfirfih there is onlw~
a partial segmentation of the vitellus, but in C/teli/er andj|
C^nmtttn the segmentation is complete. In the Artkrogtrtlri
there is no metamorphosis. ^

The Crustacea.

.\mong the Cninlncen there are hermaphrodite as well ■
dicecions animals.

In the (>■*? (■'((■[)(/((, the ovaries are situated in " the vain
of the carapace, and terminate in oviducts, which open 1
distinct apertures in front of the caudal appendage,
diately anterior to them are the openings of tiro I

* Sir Riohud On-eo's Compnratii'e Aaaiong ami Fkifialoyjf t/UmJMtitf
htalt .iH'Mott (lad eA.), p. 462.

f Like the genital organs of the AraikOtia, thOM of ths Artttr«g<mlT* an
tituated between ibe stx^ed "bep«iic" lobes.

Z OancemiDg thagtoapof marine t^viiBit{l)feingonidtn), ateDea Sortii
A'onOtart-Eijiedilimt [u] bv Dr. G. O. Sara; and Dr. T. H. MorgaB'i Bm-
krfatofy aaJ /'iyJo^njr of' tie P^rmogvmiU (iSgt). These animals do not
belong to the.lrocAawla otto the Cnutaira ; bat the;, along with tfas.lntsL
■nto and CVmUm". Ltavv ooue down tiie atream of eTolntion in r*wt'k'

PHYSIOLOGY OF THE INVERTEBRATA. 443

canals, called vaginse by Zenker, each of which is continued
into a long convoluted transparent tube, and eventually ter-
minates in a large vesicle, the spermatheca, in which the
spermatozoa of the male are received. In the males, the
antennae, the second maxillsB, or some of the thoracic limbs,
are modified in such a manner as to enable them to seize and
hold the females. The testes are elongated caeca in Cypris,
globular vesicles in CytlierCy and communicate with a long
vas deferens, which opens into the copulatory apparatus."
(Huxley.) The development of Cypris (taken as a type of
the Ostracoda) consists of a complicated metamorphosis, but
begins with a Nauplius larva, which is furnished with a
bivalve shell.

In the Branchiapodu the sexes are distinct, and sexual
reproduction occurs ; but in Ajptcs, Dajyhnia^ and other
genera, parthenogenesis occurs, along with sexual reproduc-
tion. In Zimnadia gigas no males are known to exist.

The Cirripedia are, as a rule, hermaphrodites. The ovaries
are situated in the peduncle ; and the oviducts pass into the
body and open on the basal joint of the first pair of cirri.
The testis consists of numerous ramified follicles, which are
united to two long vasa deferentia; the latter unite, and
then pass into the penis. The penis is situated in, and opens
at, the extremity of the tail. The tail can be used as a
copulatory organ, being brought into contact with the aper-
ture of the oviducts. Self-impregnation may take place in
the Cirripedia. It was Goodsir* who first proved that all
these animals were not hermaphrodites, for in Balamcs
hcUcenoides the sexes are distinct. Darwin f proved that
Scalpellum and Ihla are both dioecious and hermaphrodite
Cirripedia. The males of Ihla lie within the sac of the
female ; as these males are supernumeraries, Darwin termed
them complemental males.

After impregnation the segmentation of the vitellus is

* Edinburgh New Philosophical Journal^ 1843.
t Nature, 1873, p. 43>-

444 PHYSIOLOGY OF THE INVERTEBRATA.

complete, '■ and tlii' embryo attains to its earliest InrvAl
dition within the egg." *

In the AinphijHida and fs&podn, the male organ
a testis, which opens on the first abdominal somite
are eitli^r one or two pairs of penes. The female organ con-
sista of two ovarian tubes ; and the ducts open on the rentral
aide of " the antepenultimate thoracic Bouiiti' or on the bases
of the limbs of this somite." The ova, after being laid, are
deposited in an incubating pouch or chamber, situated
" beneath the thorax, enclosed by the oostegites of the
thoracic appendages." No true metamorphosis takes
place, except in the young of certain parasitic fonus. The
vitellua in some forma undergoes complete segmentation,
whereas in others it is only partial.

In the Stomapoila the st^xes are distinct. The tt'stMJ
of the male consist of ramified giands. from which pass
two vasa deferentia, which terminate in penes projecting
the base of the last pair of feet. The ovaries consist also
ramified glands, situated in the lateral |x)rtions of tlw
posterior abdominal segments. These glands are united in %
long tube, which envelopes the alimentary canal. "The
portion of the ovary, contained in the three segment£ to
which are attached the ambulatory feet, sends towards the
ventral surface three branches, which join, upon the medl
line beneath the abdominal cord, with those of the op]
aide, and form, in the middle of each of these three segmi
a round sinus. These sinuses are connected by longiti
anastomoses, and the anterior one is prolonged into a common
papillary vulva, situated in the middle of the iii-at abdomtOkl
segment, beneath a homy process." (Von Siebold.)

The genital organs of the Anomuiim and Braektiura^
so little in structure from those of the Mnciimrrf, that
describe only thoii-e of the latter order, with the addition
few general remarks on the first two mentioned orders,

» For fiirtber informniion sec Clans' Gnndziinge iltr Zoologit: andDu*

, Monajrnph vflke f'iiT'peiliii, 3 vols.,

riie
cm,B

at
■he

media^^

gmenl^H
itudini^^
~?nunon
omtokl

udDu> I'

'PHYSIOLOGY OF THE INVERTEBRATA. 445

As a type of the Macrouraywe describe in detail the genital
organs of Astaciis. The sexes are distinct ; and in external
form the testis and ovary have each the outline of a gland
composed of three lobes (Fig. 77). They also occupy a similar
position in the body — viz., behind the stomach and below the
heart. There are two vasa deferentia which are united, one
on each side of the junction of the three lobes of the testis.

Fig. 77.— Reproductive Organs of Astacls.
a = testis or spermarium. d = vas deferens, c = coxopodite of fourth
ambulatory limb, d = cells of vas deferens which secrete the sper-
matophores. c = ovary. / = oviduct. ^ = coxopodite of second
ambulatory limb.

These ducts are long and coiled, and terminate in apertures,
situated on the coxopodites of the fourth pair of ambulatory
limbs.* Each lobe of the testis is composed of small caeca in
which the spermatozoa (see Fig. 76, e) are developed. The
spermatozoa are united into masses, which become invested
by a iine membrane secreted by the cells of the vasa deferentia
(Fig. j^j d) ; thus forming the spermatophores. The ovary
is composed of three large cseca, and the ova are developed in
this organ. The oviducts are short tubes, which open on the
coxopodites of the second pair of ambulatory limbs. The
internal walls of the ovary are lined with epithelial, nucleated

* Id the land crabs the male genital aperture is situated on the last seg-
ment of the body.

446

PHYSIOLOGY OF THE INVERTEBRATA.

cells, wHcIi give rise to ovisacB. (See Pig. 76,^). An ovisac
consists of a mass of cells; a central ceil, howt-ver, grows
until it forms an ovnm (containing a ^rminal vesicle and
spot, viteUns, and vitelline membrane). The ovisac oltimatelj
bursts, liberating the ovnm, which falls into the carity of
ovary. It then pasaes down the oviduct to the exterior, wl
it becomes attached by a viscons matter (covering the vitellintfl
membrane) to one of the swiramerets. The v
hardens, and consequently encloses the egg in a tough i**,-
which is sus]Jended from the svrimuieret by a jiedancle, whicli
is in reality a prolongation of the substance of the case. The
ova are fecundated while in the feuiale. The fecuadatrti
ovum undergoes partial segmentation of the vitellus; ami
after the formation of a short, round, primitive streak, ili
limbs develop, and the embryo passes through the ^''ifijrii«
stage. After this the embryo develops further, and is hatchi-il
in the general form of the adult, the Zo'i''i or Cojirjiul stage
being rapidly assumed and discarded during the embryonic
existence. After moulting, the abdominal feet are dereli
and the young Aducus becomes altogether similar to
adult form.

In the Mftcivurn and Fn^u.rii1<r, the male genital apertotv*
are "surrounded by a soft sphincter, without any trace of*
penis, but out of which the ductus ejaculatorius is perhaps
protruded during copulation. But with the Bracfit/um auii
short-tailed Anvmrntm, on the contrary, there are two longer
or shorter tubular penes, always covered by the tail, which
is pressed against the abdomen. In many Dix<tpoda, the
feet of the first caudal segment are transformed into
cellated processes (secondary penes), the extremity of wl
is sometimes grooved. In some short-tailed Anomoura,
feet of the second post-abdominal pair take part also ii
act of copulation, and, for this purpose, are prolonged into
stalk-line organs." *

yonic

otta

* The forms asEDmed bj the s[iermatozoa of Pagnriu, ISta, ai
0 illustrated iu Fig. 76, p. 411.

PHYSIOLOGY OF THE INVERTEBRATA. 447

The Polyzoa.

Beprodaction in these animals takes place by gemmation,
parthenogenesis, and gamogenesis. Where gemmation occurs,
the buds produced usually remain adherent to the stock ; but
in Pedicellina and Loxosoma, they become separated. Gem-
mation occurs throughout the whole colony of polypides. In
the fresh water Polyzoa, a kind of parthenogenesis is the mode
of reproduction. In these animals, gemmules, statoblasts, or
unfecundated ova, are developed in the funiculus. A stato-
blast is usually biconvex in form, covered by two chitinous
shells, and gives rise to an animal which, when hatched,
resembles the adult. It soon becomes fixed and produces
(by gemmation) a new colony of organisms. Sexnal repro-
duction or gamogenesis always takes place in the Polyzoa,
As a rule they are usually hermaphrodites. The male and
female organs are groups of cells, the former being developed
either in the upper portion of the funiculus or at its base ;
and the latter on the internal surfape of the anterior part of
the endocyst The ova fall into the perivisceral cavity, where
they are fecundated by the spermatozoa, which are also
present in the same cavity. The fecundated ovum (in marine
Polyzoa) passes into the ovicell — a dilatation of the body wall.
The ovum becomes segmented in the ovicell, forming a
morula, and subsequently a blastula. Finally, the embryo is
hatched as a ciliated free swimming larva (Trochosphere).
After swimming about for some time, the larva becomes
stationary and develops a tentacular crown and "cell."
New zooids are then produced by gemmation, and so a new
colony is gradually formed.

The Brachiopoda.

Most of these animals are dioecious ; and the genital organs
are situated in the body cavity or its prolongations. They
consist of paired, glandular bands ; and the spermatozoa and

448 PHYSIOLOGY OF THE INVERTEBRATA.

ova pass into the body or perivisceral cavity, and from tiienw
they pasa to tht^ paliial chamber by the excretory dnccs.
iUter fecundation the ovum becomes completely segmitntrti
and a I'ree swimming gastnila is formed by invagination.
AftiT this a free swimming, si-gmeutod, ciliated lan-a, liki"
that of the AiuulUhi, is pi-odiiced. This larva is composed
of three segments- — the cephalic, thoracic, and caadal; it
ultimately becomes fixed, and the shell develops from tbf
thoracic segment.

The MoLLLTSf^A. ■

In the Lamdlihranch'UUu, the sexes are usually distinct, boifl
these animals are sometimes hermaphrodites.* The geuital
organs in both sexes are somewhat similar to each oliier.
They are paired, lobed, or racemose glands ; and occupy the
upper portion of the foot. Taking Aiwiionin as a typical
example of the Lamdlibraiichiata, these glands vary in siie
with the season. In the spring and winter, they are largfr
than at any other season. The genital ducts (of both sexee)
open into the cloaca. The testes are white or yellow (due to
the spermatic fluid), and tJje ovaries are red (due to the colour
of the ova). The fecundation of the ovum takes place in the
branchial chamber of the female; it then )msses into the
branchial spaces of the external gills. The segmentation i^m
unequal, and the embryo passes through a morula (bla
meres), a gastrula, and a free-swimming, ciliated, or veligeni
condition.

The Gasteropoda are either dia-cious or bermaphi
As a typical example of the PulvtwfiulcTopodit, we deficribe tf
reproductive organs of Sdv:. This animal is hermaphrodite;
and its genital apparatus consists of a single gland — ^the
ovotestis (Fig. 78} composed of branched tubules. In this

* Cj/clai, Cardiam (some species), itefen (some cpecies), Ottr^ra, J^iailirm,

f The Seophopoda and i/iSsroporfa aiediooions, while the iUjipfafftpAon
are hermophrocJites.

PHYSIOLOGY OF THE INVERTEBRATA. 449

gland the spermatozoa and ova are developed, but never at
the same time. In terrestrial snails the maturity of the
spermatozoa precedes that of the ova ; the object of this
arrangement being to prevent seK-impregnation. The narrow,
common, hermaphrodite duct leads from the ovotestis, but

Fic. 78.— Reproductive Oku.

= Rag or sperm gland, b — tetractor nnwcle of penis, i — penis,

rf = genital veslibule. r = darl sac. / = dart. g — vagina.

h = mucous glands. 1 = spermalbeea. * = ovolealia. mo — her-
maphrodile duel. « = albumin gland. fi = proslale.

soon dilates. In this dilated jwrtion it receives the secretion
of a large albumin gland. Beyond this point it divides into
two ducts — one for the spermatic fluid, and the other for the
ova. The oviduct passes into the vagina, while the narrower
branch of the comuion duct is continued into a separate vas
■deferens, the extremity of which leads into a long penis.

^vaeier<

450 PHYSiOLOGV OF THE INVERTEBRATA.

Projectiug from the vaa deferens is the flag or flagelinm.
The vagina and the male aperture (at the end of the jienis)
open into a common cloaca, which bears tilamentous gland-
ular appendages or mucous glands. These secrete albomin.
The muscular dart-sac (which contains a "calcareous" or
'■ chitinous '' dart or rod ") also opens into the common
cloaca. In connection with the female genital aperture, there
is a receptaculum seminis or spermatheca. Although IhVu
is hermaphrodite, cross-fertilisation takes place. When two
individuals copulate, the dart or spiculum amoris is protruded;
and no doubt acts as a stimulating organ. The dart is nsually
broken up during copulation, but ia afterwards replaoeJ.
During coition, the semen of one individual, after being dis-
charged, is stored in the s])ermatheca of the other individual.
The ova are impregnated in the duct, and are invested in
albumin, which is enclosed within a calcified choi
development is direct, and the young is hatched in the fiw
of the adult.

" The Brancliwgasteropoda fall into two distinct series, d
which the one is hermaphrodite (the genital gland being ii
ovotestis), and invariably opistLobranchiate ; while tLe a
is unisexual, and usually prosobranchiatfl."

In some genera the penis is not developed it.,g., MwrthitOHiA
PImivti/maria), while in others the organ is developed (<^
Jv'atica, Turritdla, Votulii, Cypraa).

The Pltropoda are hermaphrodites, provided with an o
testis, which develops spermatozoa and ova. As in Htlil
these two generative elements are not mature at the saine
time. The ovotestis has a single duct, the termination of
which may be provided with a receptaculum seminis, and
connected with a penis. Cross-fertiUsation takes place, and
the ovum gives rise to yonug, provided with a radimentAiy
shell, velum, and probably an operculum. In some fat
{Hi/alaa) the shell is retained, while in others (6'/io) it d
appears.

• In some species the dart c

PHYSIOLOGY OF THE INVERTERRATA. 45"

The C(p}m\apoda are diocoioua, and the genital organs are
nnJike those of other Molhisca. " They consist, in both sexes,
of lamellar or branched organs, the cellular contents of which
are metamorphosed into ova and spermatozoa, and which are
attached to one point or line of the wall of a chamber, which
coramonicates with the pallial cavity by two symnietrieaJly

Ftti. 79.

[ Mai£ Rei'boductivk Organs d

Sepia.

lA/kr Dk. A. vcs Mojsisovccs.)

I = leslii. p = penis, fd — vi

defereiu. fir = prostali

isp — receptacle or spermalophoreE

lAfttr M [LS B-EliWAHPS. )

a — aaaa. oil — ovary, gn — nida-

mmT«l glands. gi' = accessory

glands. i<J = oviducnl gland.

0}f = oviducal apenure. i ~ in-

disposed oviducts, in the females of some species ; but in
most female and almost all male Cephalopoda it has only one
duct, the termination of which is situated on the left side,
but may be near the middle line (male Ntiutilm), or even on
the right side (female Nautilus)."

I In the male Stpin (Fig, 79) the genital organs consist of a
well-developed testis, a vas deferens, which passes into a

4S2

PHYSIOLOGY OF THE ISVERTEBRATA.

veeicala seminalis, at the termination of which is the prostate.
The prostate forme the sperm atophores, which are discharged
into a receptacle (Fig. 79). The receptacle or sperm-sac
then leads into a muscular penis, at whose extremity is
situated the genital aperture. " The projection of the Bperm-
8ac occurs at the moment when, daring coition, the Epenoa-
tophorea pass from the penis of the male into the sac of the
mouth of the female. A true intromission of the penia into
the female genital openinfT appears impossible in these
animals, so that coition consists only in a ^mple joxtapoeition
of the genital oi^ns."' (Von Siebold.)

In the female Sepia (Fig. 80) the genital organ consists of
an ovary, with an oviduct which opens near the anns. The
oviduct presents an enlargement called the oviducal gland.
In addition to these, there are nidamental and accessory
glands. These glands secrete a substance which invests the
ova as they pass from the oviduct, and which serves to ^oe
them to foreign bodies. The fecundated ovum ttndei^oee
partial segmentation ; but for the further development of thft
embryo, the reader is referred to Professor Lankester'a paper
in the Qxiaria-ly Jouitial •>/ MicruscopUal S<-u-iur, 1875
Grenacher's paper in the Zcitschrifl /ht Wissawtlu^i
Zooloffif, 1S76; and Mojsisovics's CftjthnJcpodcn iter Me
raaen.

The Tr:ncATA.

These animals are hermaphrodites; but cross -fertilisation
takes place as the spermatozoa and ova reach maturity at
different times. The testes and ovaries are racemose glands,
which usually lie among the \-iscera in the hinder portion of
the body. In many simple Ascidians, however, these organs
are situated in the lateral walls of the atrium, into whidi
their ducts* open more or less in the vicinity of the anus.
The imprt'gnated ovum becomes completely segmented, and
passes through the morula and gastmla stages. Afterwards

* Tbe ovaries aod testes of Apf^nJicalaria are devoid of donta.

PHYSIOLOGY OF THE INVERTEBRATA. 453

a free-swimming tailed larva is developed. Just before
reaching maturity, the larva attaches itself by means of
papillae, and undergoes a series of changes, of which the
following are the most important: The tail aborts, the
muscles and notochordal sheath degenerate, and the noto-
chordal axis contracts. The nervous system and organs of
sense degenerate, and the cavity in the nerve-cord and
cerebral ganglion disappear. The pharynx increases largely,
and the branchial slits become visible. After this the adult
state is reached.*

At this point we give a diagram (Pig. 8i) which indicates
roughly the evolution of the InvertebrcUa.

CoNCLUDma Remarks.

This chapter has its moral — that like ahoays begets like.
It does not matter by what mode of reproduction it has
been produced, the offspring is always of the same kind
as the parent. It appears that transformation or pleo-
morphism does not exist in the animal kingdom. The life-
cycles of the lowest as well as the highest animals repeat
themselves according to a well-known law. " To one who
has fully comprehended the meaning and the operation of
the Darwinian law, it will be at once apparent that there
must be error somewhere in the matter of pleomorphism."
How can Bacilhis mtbtilis be transformed into Bacillus
anthrads ;^ or an amoeba into a gregarina by the experi-
mentalist? "If the law of actual variation," says Dr.
Dallinger, **with all that is involved in the survival of
the fittest, could be so readily brmight into complete opera-
tioTiy arul yield so pronounced a result, where would be the

* In some of the Thnicata, the development of the embryo takes place
within the parent, and there is a placenta. See also Giard's papers in
Jievue jScUntifiqu€f 1874 ; Compte* Jitndus, 1874-5; -Archives de Zodogie
Exp^rimentaUj 1872.

t See Dr. Griffiths' book : JResearehes on Micro- Organisma, p. 41
(Bailli^re & Co.).

454

PHYSIOLOGY OF THE INVERTEBRATA.

N
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PHYSIOLOGY OF THE INVERTEBRATA. 455

stability of the organic world ? Nothing would be at one
stay.

" There could be no permanence in anything living. The
philosophy of modem biology is that the most complex forms
of living creatures have derived their splendid complexity
and adaptations from the doxo and majestically progressive
variation and survival from the simpler and the simplest forms.
If» then, the simplest forms of the present and the past were
not governed by accurate and unchanging laws of life, how
did the rigid certainties that manifestly and admittedly
govern the more complex and the most complex come into
play ? If our modem philosophy of biology be, as we know
it is, true, then it must be very strong evidence indeed, that
would lead us to conclude that the laws seen to be universal
break down, and cease accurately to operate, where the
objects become microscopic,* and our knowledge of them is
by no means full, exhaustive, and clear. Moreover, looked
at in the abstract, it is a little difficult to conceive why there
should be more uncertainty about the life-processes of a
group of lowly living things, than there should be about the
behaviour, in reaction, of a given group of molecules. The
triumph of modem knowledge is a knowledge — which
nothing can shake — that Nature's processes are inamutable.
The stability of her processes, the precision of her action, and
the universality of her laws, are the basis of all science, to
which biology forms no exception. Once establish, by clear
and unmistakable demonstration, the life-history of an
organism, and truly some change must have come over
Nature as a whole, if that life-history be not the same to*
morrow as to-day ; and the same to one observer, under the
same conditions, as to another.

*' No amount of paradox would induce us to believe that
the combining proportions of hydrogen and oxygen had
altered in a specified experimenter's hands in synthetically

* Biichner, Sattler, Grawitz, and others state that certain microbes are
capable of being transformed into other microbes.

456

PHYSIOLOGY OF THE INVERTEBRATA.

prodncing water. We believe that the melting-point of
platinum and the freezing-point of mercury are the same u
they were a hundred years ago, and as they will be a
hundred years hence. Now carefully remember that, bo far
as we can see at all, it must be ao with life. Life inheres m
protoplasm ; but just as one cannot get ahsiraet matter — thrt
is, matter with no properties or modes of motion — ao one
cannot," aaya Dr. Dallinger, " get abstract protoplasm.
Every piece of living protoplasm we see has a history : it
is the inheritor of countless millions of years. Its properties
have been determined by its history. It is the protoplasm
of some definite form of life which has inherited its speciSc
history. It can be no more false to that inheritance than an
atom of oxygen can be false to its properties. All this, of
course, within the lines of the great secular processes
of the Darwinian law, which could not operate at all ^h
caprice formed any part of the activities of Nature." ^M

In addition it may be remarked that pleomorphism 4^|
entirely opposite to the Darwinian law, but abiogenesis ^^
already stated at the commencement of the present chapter)
is not' in opposition to evolution. It is one of the theories
which have been brought forward to explain the origin of lif?
in the world. Protoplasm consists of carbon, hydrogen,
oxygen, nitrogen, with a little sulphur ond phosphonis. and
still fainter traces of other elements, combined in extreme
complexity. " Given the matter which composes it, and the
play of forces and energies of which that matter is the
vehicle, wherein lies the difference which gives as one result
non-living substance, and as another result living snbstance ?
The answer obviously is that, the ingredients being the same,
the difference must lie in the mixing;" and it is this
"mixing" which the scientist has to find out to explain the
oriffin of life, or, before abiogenesia can be considered to be
more than one of the theories which have 1
during historic times to account for it.

' been pat ft»ti|H

APPENDIX.

* ♦ I

I. The Composition op HiEMOCYANiN.

The author '^ has ascertained the approximate composition of
hsemocyanin (see p. 1 42 et aeq,). The haemocyanin derived from the
blood of HomaruSy Sepia^ and Cancer respectively was submitted,
after purification, to chemical analysis. The percentage composi-
tion of this important substance is very constant. In this respect
it differs from haemoglobin. We are, therefore, justified in calcu-
lating an empirical formula for hsemocyanin as follows : —

The blood of the lower, and some of the higher. Invertebrates is
a watery fluid, called the hydrolymph. But in the majority of
the higher Invertebrates, the blood is less watery and much richer
in albuminoids ; it is sometimes termed a haemolymph.

II. Invertebrate Cartilaoe.

Invertebrate cartilage is very similar, chemically and histo-
logically^ to that of the Vertehrata, Dr. W. D. Halliburtonf has
recently examined the head cartilage of Sepia, and the entosternite
of L%mvlu8, " The basis in both structures is chrondrin ; there
is, however, in addition, a certain proportion of chitin, in the case

* Comptes Bendtis de VAcad^iit dea JScienceSy tome x 14, p. 496.
t Proceedings of RoyaL Society, vol. 38 ; and Quart. Jour, Micro. Science,
vol. 25.

4S8 APPENDIX.

of Limvhii i.oi.nndinthatof .Sffpio \.%2 perceat. Tliese resulU
are eepeciall; interestiDg, as ebowing that chitin is cot a siibstiuii.«
wlitt;h is exclusively epiblastic in origin, but here, at least, we
hare it oct;uri'ing in mesoblastic structures."

III. C'UITIN AND OTHElt SlBSTAKCEB.

CAih'jt.— This substance, which is frecjueutly impreguated witb
salts (calcareous salts ia the Cniataeta, silica in the lingual ribbon
of certain Mvlluaca), "has a very wide distribution among ih*
Invtrtebrata. It is io the Arlhrojitxla that it is found to tht
greatest extent; it foiinB the membrane of the ovum, the cnttd*
of the adult, with it« appeniloges, the supporting Gubstance in the
tntcbete of insects, &c. It is also found in the Mollu«ea (jaws and
odontophore) ; and in worms {e.g., the setie of the AnnelkUt). It
forms the menibrane of the ova in other groups, and the cyst-mil
in encysted forms of the Protozoa, Ac."

Chitin ia readily prepared by treating tiie shells of crabs and
lobst«r8 with IICI, so as to dissolve out the raloireons salte. II
is also obt^ned by digesting the wings of beetles and other insect*
in a solution of NaHO. In both cases the chitin remains uudi*-
solved. The residue is then dissolved in strong HCl, and re-
precipitated from tliis solution by the addition of water. This
operation is repeated two or three times, when the chitin
obtained in a state of purity.

Chitin is a colourless subetonce, devoid of crystalline struct!
and \s only soluble in strong mineral acids. When heattd
strong acids, it is decomposed into acetic acid and glucosaouDe
2C,^H„N,0„ + 2H,0 = 30,H,0, + 4C.H,^0..

Conchiolin (CjuH„N,0„) ia the sheletln or basis of the shells
the GaHeropoda.

Comein (f»H„N,0[,) is the skeletin of Goryonia and otbar
corals.

Spongin is the skeletin of the Pori/erct, Its composition »
unknown.

Fibrorin is the substance of which the webs of spidi
posed.

in b
llstfl

imposition »^J
iders ore cont^H

APPENDIX. 459

These four substances all jield leucin and glycocine on decom-
position.

Uyalin is allied to chitin, and is found in the Echinodemiata
and other Invertebrates. It has the following composition: —
0 = 45-3 to 44.1; H = 6.sto6.7; N = s.2to4.s; 0 = 43 to 44.7 per
cent.

Tunicin is the carbohydrate found in the Tunicata, Ophn/-
dium, &c. It is represented by the formula {C^'H.^fi^)^.*

IV. The Ink-bag op Sepia.

The secretion of the ink-bag (see p. 73) is used to colour the
water and cover the flight of the animal. It contains from 70 to
87 per cent, of solids, of which the black or brown pigment is the
chief constituent ; it also contains mucin, magnesium carbonate,
sodium sulphate, calcium carbonate, and sodium chloride. Accord-
ing to Nencki and Sieber,! the pigment contains an acid, which
has been termed sepiaic acid.

It has been suggested that the ink-bag corresponds to a liver ;
but its secretion contains neither biliary acids nor glycogen, and
it has no digestive properties.

V. Wave-lengths.

The sign X (p. 1516^ aeq,) denotes wave-lengths. For instance,
X506 means a wave-length equal to 506 millionths of a millimetre.
Sometimes the letters W.L. are used instead of X.

* For further information, see Gautier*s Chimie Bidogiqut (1892), pp. 163,
165, 188 ; and Halliburton's Chemical Physiology and Pathology.
t Chem, Centralblatt, 1888, p. 587.

INDEX OF AUTHORITIES.

- ■ » ♦«

AOASSiz, L., 303, 350
Allman, G. J., 298
Anacreon referred to, 435
Aristotle, 108, 407

Backs, 137

Baejer, A. von, 13

Balbiani, 407, 408, 410, 437

Balfour, F. M.. 404

Ball. W. P., 563

Barforth, 108

Bastian, H. C, 399, 406

Beddard, F. E., 225

Benecke, 410

Beneden, E. Van, 146, 405, 410

Beneden, P. J. Van, 36

Bennet, 399

Bernard, Claude, 140, 288, 399

Bert, Paul, 168

Bibra, Von, 167

Binet, A., 4, 296

Bischof, 252

Blundstone, 115

Bokomy, T., 11, 12, 14

Bradj, G. 8., 55, 56

Brandt, 81

Buchner, 455

Buckton, G. B., 435

Bunge, G., 227

Butschli, 376. 407

Byron quoted, 360

Cahoubs, id

Capranica, 271

earlier, E. W., 126

Carruthers, W., 426

Cbabrier, 394

Chandelon, 76

Ci&okowsky, 27, 81

Clapar^de, E., 258, 348, 407, 44 1

Glaus, 298, 300, 359, 444

Cohn, F., 419

Cowan, 394
Cu6not, L., 141
Cunningham, J. T., 284
Cuvier, 72, 75, 108, 185, 400

Dallinger, Rev. W. H., 27, 348, 376,

377, 399, 405, 406, 453, 45^
Dalton, J., 180
Darwin, C, 4, 56. 85, 239, 249, 329.

359, 3631 391, 392, 400, 402, 403,

436, 443, 444
De Bellesme, J., no, 116
Delle Chiaje, 130
De Negri, G., 211
De Quatrefages, 320, 354, 414
Devaine, 426
Devauz, H., 233
Dixon, H. H., 391, 392
Dohm, A., 439

Drysdale, J., 27, 348, 376, 405, 406
Dufour, L., 262
Du^ds, 219

Dujardin, 325, 347, 440
Dumas, J. B., 10
Duncan, P. M., 350, 351
Dunstan, W. R., 261
Duthiers, Lacazc-, 45, 283, 431

EURENBEBG, 347, 354

Eimer, 310, 311, 379.410
Engelmann, T., 172
Erman, 167

Ewart, J. 0., 312-319, 35ii 352, 380,
383, 385

Faivre, 325

Favre, 430

Fisher, 97

Follows, H., 282, 283

Fol, M., 206

Foster, M., 15, 102, 404

463 INDEX OF AUTHORITIES. ^^k

Frederioq, L., Si, 85, S7, SS, S9, 91,

1 RviNE, R, 63. 245. *4ft as*. »SJ^H

10,. 107. no. 116, 135, 137.139,

282 ^H

141, 143. '44. 166, 168. 3'8, 319.

331-336

JOHNSTOKB, A-, 100. 270, 42; ^^H

Fremy, 137

Joly. 399 , ^H

Files, 410

Jolyet. 116, 333,335 ^H

Joseph, G., 330 ^H

Gautikb, a., 175, 459

Kent, W, 8., U^a^ H

Geddea, P.. 105, 149, 224. 226

Gegenbaur, C, 193, 158, 325, 365,

Eisbiaoaye, K.. 441 ^^H

366. 370

Kisser, 14 ^H

Genth, 166

Kisttakowsky, no ^H

Giard, A., 344, 412, 416.453

Kl(,b», 347 ^H

Gibson, R. J. U.. 2S4. 285, 354

Gmelin, 90

K6mker. A., 407 ^H

GoodEir, 443

S:Eir»«i„.,,„s ■

Gornp-BesaoeE. 168, 274, 283

Graber, V.. 194

Kretsschmar, 13 ^

Gratiolet, 190

ErakenberK, 106, no, 116. ijo, ri:

Grawlu, 455

143.157. 16S, 169, 170, 211, ;i:

Oreet..lSs, 415

217.322.338-240,244

Grueowood, 79

Kuhne, W.. 148, 157

Grenadier, H., 255. 461

Kundt. 214

GriffllliB, A. B., 4, 10, 13. 27, 30, jS,

KiinsUer, 348

S3, as. 88, 89, 92. 94, 95, 100, 102.

103. los, ioa-112. n6. 141. 143.

Lachmas, 348, 407

144-147. 175-180, 229, 346-248,

landois, 360

2S4. 256. 257. 259. 26s, 266, 270.

Lanke<ter, K. R., 77.80, 81, !*»

272. 275, 279, 282-2S7, 336, 351,

131. 144. M6. ISS. 16S, 167,

357.361.390,426,4531457

238. 284. 34». 453

GrDS, 406

Ijitham. P. W., 15, 17

Gtuber, 296, 334. 407

Ledenfeld, R. von. 196, 397

Gnckelbergei, 15

Letoajnean. C, n6

Leookart, K., 97

I-es-y.M. 106,1.5

HAiCKiiL.E., 80, 8..82, 166, 298

Levdig. 3S1. 353, 357

Hallibarton, W. D., .48, 167, 457'

LieberkObD, 10, n, 17

Hamann, 0., 319

r^Sw, 0., n, 12. 14

Harless, 167

Lowne. B. T., 9S. 267

Harlcj, G., 277
Harting, 298
Harvey, 182
Hauser, G.. 356. 357

Lnbboot 8ir John. 373, 418
Lyonnet, 229

Macdonald, J. D., 368

Hayoraft. J. B., 126

Msflleod. 230 ' ^

Helfflholti, 331

UacMunaC. A., 81. 81,85,91,

Hansen, 357
Herdman, W. A., 344

105, 127, 139. 131, 146-157.
169, 174. 309-216, 230, 331,

Hertwig. 0., 298
Hertwig, R., 298

M^^i%''-'^'-'^^^'

M'Alpine, D,. 39S

Hoffmann, 18s

Mantegaiia. P., 398, 40S

Hoppa-Seyler, P., n. 116, 213

Huxley. T. H., 2, 5, 9, 19. 26, 31, 36.

Marey, 333
Martens, 387

39, 43, 56. 61. 129, 186, (87, 18S,

Hanpaa, 346

192, 201, 205, 206, 230, 237. 3&3.

McC^k. H. C„ ,00

265, 189, 296, 297, 311. 329, 394,

Meokel, H., 99. 44*

399, 403, 413, 417. 419. 437, 443

Meldola. r!,^.

INDEX OF AUTHORITIES.

463

Merejkowskj, 148, 149

Metschnikoff, E., 431

Milne- Ed wards, 130, 248, 287, 451

Milton quoted, 391

M'Kendrick, J. G., 211

Mojsisovics, A. von, 451, 452

Moleschott, 235

Morgan, C. L., 359, 373

Morgan, T. H., 442

Mori, 12, 13

Morse, 276

Moseley, H. N.,40, 210, 215, 216, 218,

225, 429
Mulder, 10
MOller, 348

Murray, J., 245, 249, 252, 253
Musset, 399

Nencki, 459
Newport, 192, 229

Owen, Sir Richard, 200, 338, 339,
394,442

Palladin, W., 14

Palm, R., 84, loi

Papillon, 166, 168

Parker, G. H. , 364

Pasteur, L., 399

Pelouze, 137

Pennetier, 399

Pettenkofer, 84, 90, loi

Pfluger, 15

Planta, A. von, 97

Plateau, 93, 1 16

Pouchet, F. A., 263, 347, 399

Poulton, E. B., 126, 132, 133, 134,

146, iS7i 158, 160-165, »7o, 261,
264
Prouho, H., 319

QUATREPAGES, J. L. A. de, 320, 354,
414

Rabuteau, 166, 168

Ranke, 357

Rawitz, 272

Regnard, 166, 217

Regnanlt, 233, 235

Reinke, 12, 13

Reiset, 233, 235

Richet, 120

Robin, C, 5

Romanes, G. J., 120, 294, 297-320,

349-352, 373. 378-385
Rotteken, 350

Rouget, 168, 375

ROling, 10

Sabs, G. O.. 34, 5i» 53. 54. 55. 57.
196, 197, 199, 217. 232, 271, 328.

^ 329, 361, 395. 396, 414. 442
Sattler, 455

Savigny. 48, 113

Schafer, E. A., 300

Scherer, 10

Schiff, 288

Schmidt, 169, 279, 280, 357

Schmiedeberg, 106

Schmitz, 22

Schneider, 350

Schonfeld, 97

Schorlemmer, C, 1 1

Schiilze, 14, 217, 264, 265

Schiitzen, P., 17

Schiitzenberger, P., 10, 13, 14

Schwalbe, G., 130

Schwann, 3

Sieber, 459

Siebold, L. von, 331, 356, 357. 361,

363, 394. 424. 436, 437. 438, 440,
444. 452
Smith, 287

Sochaczewer, D. 366, 367
Spencer, Herbert, 18, 250
Speugel, J. W., 366
Stamati, 103
Stein, 29, 346, 407
Stokes, Sir George, 131, 174
Swinton, A. H., 195, 358, 436

Teuscher, 185
Thomson, A., 393
Tiedemann, 90, 185
Tyndall, J., 399

Van der HoXven, 51

Vandevelde, G., 331-336

Vejdovsky, 225

Verne, Jules, referred to, 249

Vierordt, 172

Vitzou, 277

Vogel, 214

Voigt, 81, 283

Vulpian, 342

Watts, 170

Weinland, C, 271

Will, 274, 283

WUliams, T., 366

Wittich, no

Witting, 168

Woodhead, G. S., 63, 277-282

Wurtz, A., 10, 233

Zaleski, M., 103
Zeiss, C, 157, 171 246
Zenker, 443
I Zonachus referred to, 435

SUBJECT INDEX.

-*-^^-

Abioqenssis, 399, 4cx), 456
Absoiption in Annelida^ 122

ArcLchmda^ 123

Brachiopoda, 124

Cestoidea, 122

CcelentercUa, 120

CfrustaceOj 123

Bichinodemiata^ I2I

Insecta, 123

Tnvertehrata^ 1 17-124

MoUuica, 124

Myriapoda, 123

Fwi/zoa, 124

Porifera^ 120

Protozoa^ 119
Acanihocephalay 38, 39, 323, 428
Ocarina, 47, lOO, 231, 328, 361, 439,

440
AcaruSf 231
Acherontia atropos, 179
AchetidtK, 357, 358
Acinetv.^ 26, 28, 29
Acrididce, 357

^c^iHMc, 34, 77, 81, 83, 210, 212, 213,
214, 217, 218, 219, 311, 351, 378,
411, 412
Actinia mesembryanthemunt, 212, 213,

214, 350
Actiniochrome, 214, 215, 217, 218,

219
Actiniohnraatin, 212, 214, 215, 216,

217, 218
ActinqphrySf 24, 26
Actinosphttriutrtf 24, 26
Actitiozoa, 32, 33, 121, 122, 128, 245,

311. 350
Activity of respiration, 233
jEolosonui Headleyi, 226
quarternariunif 226
tenebrarum, 225
variegatum^ 226
./£«cAna, 230

^tiolo^y, I

Agaricia., 409

Albumin, 10, 11, 13

Aldehydic nature of albumin, 12

Alimentary canal of Acarina^ 47

Amphipoda, 56

^rri7teina, 48, 99

-4rciMca, 47

Arthrogaatra^ 50

Urachiopodaf 66

Brachyura, 58, loi

Ctphatopoda, 72-75, 1 09

ChUopoda^ 41

Cimpedia, 56

Cladocera, 54

Coleoptera 46

C(^epoda, 55

Dipiopoda^ 41

Dipiera, 43

Echinodermata, 34, 82

Gasteropoda^ 70-72, 105

Gephyreay 37

Hemtchordata^ 75

Jlirudinea, 38, 87

Bymenoptera, 45, 96

hopoda^ 57

LameHAranchiata^ 67, 104

Lpmloptera, 43, 44, 95

Macroura, 59-63, 103

Nematoidea, 39

Neuroptera^ 45

Oligoausta^ 38, 87

Ortltoptera^ 4i» 92

Ostrucoda^ ^5

Pentastomiaay 47

PeripfduSj 40

PhylUmoda, 51

PoiycnaUa, 38, 91

Potyplacophora, 69

Polyzoa, 64-66

Pteropoda^ 72

PycnogonidOf 47

2 G

SUBJECT INDEX.

Alimentary canal of IthiiMhoUi,

Sagttta, 40
Scaphojixla, 69
Stoino}ioda, 57
Thgianura. 41
JHinieata, 76
Jdphomra, 50
Anuria, 33-36, 31, ao7, 146, 288
jiniirfra lerricola, 375
jtmofia. the sarcode of, 3
Ampkieora, 354
Ampkilina, 36
^n^ibaiw, So, 342
jlmyAipfaura peUun'ila, 405
Atnphipoda, 56, 428, 444
jlflijiAiufyc^i, 36
>4mj»uO«r;o, 137
Anatomy, 5

AtigttiUviia lirenapiiiiu, 259
Animal physiology, I
Anndida, 37, 113, 115-128, I30, 143,

152, 157. "82, 187, 223, 224, 226.

243. 245, 2S6. 258, 353. 354. 387.

3S9, 402, 422, 448
^nntilDiia, 5
.4>UN&infn, 67. 104, 105, I4li '^i ^°'-

^33. 237-239. 376. -279, *82, 287,

339.44s
Anomourii. 57. 444, 446
Am^liChabiitit, 359
j^nrf^on, 417, 422
Antliea eerat, Si. 212, 216, 2:7
AntAopla/ia, 376, 405
Anua, improvised, 30
Apertnres, exhali^nt, 31, 32

inhalent, 31, 120
Apltidtt. 43, 394, 40Z, 431, 436
Apkroditt, IS3, 226
JjiM, 96, 2211, z6o, 325, 360, 431
j^gtia depiUmf, 141, 143, 169

puKntnla, 14Z. 216
Apj^juliealurui ^abellani, 206, 452
AppeQdia, 457
■^P'^Qi 43S
Apui.^i. 167,271,443
^roMina, 48, 99, 101, 230, 23:, 16S.

270. 328, 395, 440. 44a
Aradinida, 40, 47, 48, G4, 9t, 123,

142, 166, 196, 230, 26S, 325, 327.

359. 361, 394. 439
ArHchnidinm of spider, 99, 268
AregUa, 25
Arclliea, 47, 63, 439
Artnicoh, 146, 153. 124, 326, 354

plicalorum, 152
Argonaula, 72
Jrgynaii, 433

Arton nttr. 23S. 284, 366

rufiu. 107, 108. 168, 237, S»
Aristotle's laQters, 3S5
Arlhrogiulra, 50, 63, 331, 36S, 3!]^ 1

.lr(/irqporfo, 9, 40, 63. 64, 191. 19I, I

360,341,342.370,371.389
^ifciri* aau, 227

denlata, 247

luniJff-WDu'cf, 227, 426

morpi'iKifa, 86

iMgaloetpktda, 337

m^max. 217

nijrrOCC><0''<i, 426

Asexual reprodactioD, 401, 411

jt^Klowutn-, 420

Assimilation, 2,10

Atlaml Jhu^iatHii. 59. 60. 61.
•OS- "39. 167, 200, 332, 234, I
274, 27s. 2S3, 323, 330, 361, J
364.396.412,445.446

Aitofiu, gastric juice of, 103
■lomach of, 61

Atttrticanlhion rubeni, 234

Alttrini gtaeialii, 221

Atleridta, 4, 34, 83. 85, 132. iB

243, 246, 354, ass, 256, 3'7. 3Sg

3S'j 380. 386. 4»4- 4
Ailmiut gihbota, 221
.i<(r(M, 409
Aalri'paitn auranfunu, 380, 383
.Itfnnta, 70
Auflilory orgfrns, 349, 351, i^ Jj

357. 36'. 36*. 363. 367.368
.4HreIiu, 211, 212, 3oc^ 30s. 306, J

378.411
AiiricHlitria, 413

BaeiHv anthrarit, 453

fu6ti7u, 4S3
Biiclcria, 21, 37
BuIanoglmniA, 75
Biilanat halimuulet, 443
Barnacles, 56

food of, 56
afcHo, 440
Bees, food of, 98
BrtoHtui, 56
Bilhartia, 410, 413
ililiaiy acids, 89. 90, 101,
Bilirubin, 73

BiUverdin. 73, 213. 214, 1
Biogenesis, 399
/(ipiniio™, 41S
ItlaatocoEle, 36, 37
Blastomeres, 3
Blaila^ alimentary canal ot, 93, ij
Blatlas, 41, 42, 93, 3i6s

SUBJECT INDEX.

467

Blind crustaceans, 363
insects, 359

Blood, chromatology of, 146-170
copper in, 145
gases of, 175-180
in 7n&«rf«&rato, 125-181
of LepidopteronslazTSB, 157-166
of various worms, 153
saline matter in, 139, 141, 144

Blood- vascular systems, 185, 187,
191, 192, 201, 231

Blood-vessels, 123, 124, 155, 180, 182,
186, 190, 197, 199, 200, 224, 228,
236. 239

Bojanus, organ of, 68, 143

Bombardier beetles, 262, 263

BoinbyXj 64

Boneilein, 225

BoiteUia, 224, 423

Bopyrus, 363

Brachiolaridf 415

Brachiopodn^ 64, 65, 66, 201, 236, 275,

338^ 447
Brachinus crepitatiH, 262, 263

dispiosofy 262

Brachifiira, 58, 60, loi, 192, 444, 446.

BranchisD, 56, 140, 192, 193, 199, 200,

202. 207, 224, 230, 232, 236, 237,

240, 286
BrarwJiiogoAteropoda^ 70, 72, 236, 284,

366, 450
BrancJtiomma, 354
Branchiopoda, 50, 53, 124. 232, 443
Buccinuniy 72, 105, 109, 238
Bugs, the, 43, 263, 433
Bunodes haUd, 212, 215 217
crass icor 1118, 212, 215

Calciferous glands, 87, 88
Calcium phosphate, 255, 282, 284,

416
CcUliphoray 96,^ 267
Calosoma inquisitor, 263
Ccdyptrfi'a, 70
Camoarus pelluciduSf 364, 365

setoMus, 364, 365
Campodea, 41
Camer, 167, 178, 233, 234
CapitellOy 146
Carabusy 263
CarcinuM mwruis, loi, 103, 104, 138,

139, 142, 167, 233, 320
Cardmm, 67, 104, 105, 234, 238, 397,

448
Cartilage, Invertebrate, 245, 368,

457
CaryophjUia, 409

Cntauaeta, 26

Cell theory, 3
Centipedes, 41

Oephalcpoda, 70, 72, 109, 142, 143,
202, 204, 236, 255, 285, 341, 365,

369* 398, 404,451
Cestoideti, 35, 36, 85, 86> 122, 127,

180, 187. 243. 320, 387, 421
Chcerocampa JElpetwr, 162
Cheetifera, 37
ChcBtogaster, 424
Chatognatha, 39, 324, 354, 429
Chcetoiwtus, 39
Cheetopterus, 153, 226
CluHura, 39
Cheiroceplialus, 146
CheUv, 50, 102
Chelicer<tf 48
Cfidifer, 442

Chemistry of protoplasm, 10-19
Chermes abietis, 436
ChiloffHfUhii, 41, 355, 389, 430, 431
Ckifopodn, 40, 41, 192, 355, 389, 430
Chironomus, 146
Chitin, 39, 56. 63, 278, 279, 458
Chitlnous spines, 40, 42
Chiton, 69
Chlorocruorin, 130, 131, 153, 155,

156, 157, 181, 225
Chlorofucin, 217, 236
Chlorophyll, 21, 80, 81, 82, 90, 132,

134, 152. i53» 165, 181, 209, 217,

225, 226, 236
Cholesterine, 13
Chorion, 412
Chorology, i
Chromatophores, 21
Chromophanes, 157
Chromophylls, 21
Chrysaora hysoceUa, 210^ 300
Chylific ventriculus, 42-46, 93
Cicadic, 43, 394, 435
Cilia, 29, 39, 65, 67, 352, 374, 375,

377
(Miata, 28, 30, 348, J77

Circulation in Annelida, 187

Arthropod a, 191

BrnrJihc^yoday 201

delent^rcUa, 184

Echinodermatcu, 185

Jnvertebrata, 182-206

JJoUusca, 201

Polyzoti, 200

Porifira, 184

Protozoii, 183

TrichoscoliceSf 187

Tunicate^ 205
Cirratulus, 153, 226
Cirri, 56, 224

^H 468 Si7RJECT I.VDEX. ^H

^H Clrr!pedia, 56, 192, 196, ilO- 3^3.

CgcIeXheria, food of, 53

^^H 443

mode of feeding in, 54

^H Cliulocero. 54, 55

kiitop!. 51, 53, 196, 197, 332, X}

^^H 01aBiiSca,tioii, 5-8

3^8, 395

^^H ClasBiflcatioQ of nertes, 294

Ciidop: 9. SS

^H CU^n. 4S

^^T*" '''' ^^

^H Claviger, 359

^H Cfi'o, 450

C'jpnt, 196. 443

^H Coi^Qlktioa of blood, 136, 13J,

CyHuleo, 34

^^1

r^^ieri". 69, 196. 443

^B otftef. 85

^H Okvui Af>wniluffl, 436
^^H CoclcToaulieB, 41, 431

DaBingtria Drgidall, 406

Dalton'slaw, iSo

^^K Cmliaiga, 405

Dapkni'i, 54, 146, 443

^V Co^eiKBrntu, 32. 33, 79. 80, 120, 181,

Darwinian law, 453. 456

^B 209, 243, 348. 197, 320, 149, 37S,

Dil^yrliliM, 39

^m 409. 410

^m CiJropUTii, 46, 63, 326, 317, 357. 359.

Dead protoplasm. 13

/>tc«iJo. 72, 272, 361. 363, 3«fc
Degeneration, 36, 39, 56. im, m

■ d&e,s "'■«',

^H C^pcda, 396

Z^ta^^l6

DtnlaUuul, 69

^H OinfA'Pcm, 196

Diaptomiu ortttilatii, 56

^^H Concluding remarkB. 453-45''

Diaal«o,89

^H Conjugation, 405, 407. 4ii

Dthrandiialii. 73. 336, 341, 367. Jl

^H Conatituent-s of so-called liver of

370
PicriiHura /urfuln, 361

^H ^elu:, 106

^^1 Contiactilc vacuoles. 25. 26, 28, 30.

niMU^, 132, 162, i6t, 362

^H 32. 183, 184. 20S, 340. 343, 246.

/),j?(«ff;„. 35

Diffused nervonfl Sfstom. a. 396

^^B Conco/uCn, 35, 36

Digestion in C</^n(ffr.tf«. 8o-S»

^H Cbp^p«ja, 50, 55, 196

E-^hinoJa-mnlt. Sj-8s

^m Coramgena. 33. 410
^H Coral recto, &o., 250-154

general, 20-78

llvudinea. 87

^H CamjiKaorft irfru/i't, 3lg

InDtrtebrata, 30-11&

^H Cotpuacles, blood, 135, 136, 133, 149,

^H iSi

particular, 79-lt6

^^1 CorrelaliTe functions, 2, 3

2V.VAo.roKa*, 85-87

^^1 Covered-ejed Medii'a. 299-305

^H Crajfish, etomaoh of, 61

types of. 21

^H Creatine, 13

Digestive cavities, 33, iai-133

^H Oreatioine, 13

H CVi&tJfo 0^a, 331

^V CriQketg, 41

DllalabU sacs, 31

^ Onnoidea, 34, 417

Ourtocin, 40, so, SI. 59, 60. 63, roi,

y)iV™oJ«, 63
i).>J>;win,4f,3SS.389,43Q

"3. "S. "37. 14a, 166. 180, 191,

196, 199. 200, 331. 271, 272, 282,

-£■>»?". 43 1

cviJ^-.^t^V'"'"'"*'^

ajrfera, 43, 96. 267, 3*5. 3*7,3

359. 393. 433. 435. 43^

Cryptom, 363, 430
Cl&nophorii, 33, 310, 31 [

Disc, trocbal, 35
Ditloma, 420

Cyinca. 311, 213

Dorii lahtradato. 143, 169

Cfanein, 311

Dmgon-lly, larva of, 4, 85, j66

(V^. 367. 448

Dra«on-flj. the, 4], 260. 394

DyiUeuM, 326, 391

SUBJECT INDEX.

469

Kddnidea, 34, 319, 352, 385, 386, 416,

418
Echinochrome, 149-152, 181
EchiDochromogen, 151
Echinodermitta^ 9, 34, 82, 121, 122,

128, I47i 149, 180, 182, 185, 219,

243, 245, 254, 311, 320, 351, 379i

412,413,416.417
Echi7wp(edium, 413, 416
Echiiiorhynchus^ 39, 323, 428
Echinua, 149, 186, 311, 315, 317, 385.

386, 416
Echinus acutuSf 319

microtuberctuatust 319
gphanraj 149
Echiurus, 224
Eledone cirrho8\t8^ 205

inwchcUa^ 168
Embryology, 404
Endogenous cell formation, 401, 404,

405. 407
Endolymph, 367

Entiomus Angidaritt, 162, 163

EnopluSf 354

Enterochlorophyll, 85, 90, 91, 104,

105, 106, 217, 220, 221, 238

Enterocoele, 37, 184, 413

Enterohsematin, 105, 238, 239

Eiittropnewstra^ 239

Entomostraceaj 79, 200

Entozoa^ 86

Epeira diademuj 99, 166, 231, 268

Apheuiera, 64

hphyra, 41 i

Anffidaria, 132

punctaria, 112, 162
Epiphragm of Helix, 284
Epipodia, 72
Errantia, 354, 388
Euffle.tKE, 22, 347
Eunice^ 146
Ewfjponffia anfractuosa, 296

ojficiiudis, 296
Eupteryxj 390
Eurt/pteridUf 50
Eversible glands, 262
Evolation of Invertebrata^ 454
Excretion in Invertebrata^ 30, 41,

241-292
Exbalent apertures, 31, 32, 184
Exoskeletons, secretion of, 245, 277
Eyes, the, 52, 301, 311, 316, 321, 328,

341, 346,348* 349» 35o» 352-355. 358,
361, 363, 364* 368, 369

Fat GLANDS, 244
Favia, 409
Feet, thoracic, 57

Fission, 401, 401;, 408, 409, 426
Flagella, 27, 28, 29, 32, 374, 375»

377
FtageOata, 21, 22, 27, J47, 348, 376

Flagell(it€tt chromatophores of, 21

Flagellate cells, 31, 32

Flustra foUacea^ 167

Food of larval drones, 98

working-bees, 98

queen-bee larvae, 98

vacuoles, 29, 30, 120
Foraminifera, 25, 26
Formica, 326
Formic acid, 45, 260, 261
Formulae of albumin, 11-17
Fresh-water worms, 38
Functions, correlative, 2, 3

generative, 2, 3

6ust<entative, 2, 3
Fusiu, 238

GamasuSf 440

Gammarus, 167, 234

Ganglia, 298, 301, 302, 304. 320-344.

352, 357
Gras apparatus, 176

Gases of blood, the, 175-180

Gasteropoda, 70, 105, 108, 141, 142,

202, 203, 340, 364, 367, 386, 448
Gastric juice of Astaeus, 103
Gastroliths, 61, 63
Gastrotricha, 39

Gastro-vascular spaces, 30-33, 120
GastrulsB, 37,408, 411, 4i4.4i7i 429.

448
Gemmation, 33, 401, 405, 407, 409

410,411,421,426,447
Generative functions, 2, 3
Genital organs, 411, 412, 414, 416-

424, 427-453
Gw^iUuB, 363, 430, 431
Gephyrea, 37, 129, 180, 224, 321, 353,

423
Geryonidir, 298

Gills, 155, 157, 168, 199, 230, 232,

236, 240, 448
Glands, pedal, 367
rectal, 42

saUvary, 38, 40-42, 47, 49, 50,
60, 63, 64, 70, 73, 87, 91, 92,
94, 95, 97, 100, 105, 107, 108,
112, 114
Glandular organ of NenuUoideti, 259
Glenodinium polypfiemus, 347
Ghmeris, 355, 431
Glow-worm, 264
Glycera, 131, 146, 153
Glycochohc acid, loi, 103, 112

SUBJECT mVEX.

Glycogen, 96, 97, loi, 103, 104, 112,

"5
Gljcogeoio fnootion in MoRwca,

Quolliopodti, 50

OoniiiUtr equttlri*. all

Oanioitrtca mvlliUibiii'i, 353

OordihJi, 438

Oraptiit, 41Z, 446

OraashoppiirK, 41

Green glandi, 172, 174, 387

Oregiirhia, 21, 23. 34, 119, ao8. 375.

401,405
Qrt/ualaljia, 351
GrgUiw, 390

Giianin, 13, 255, 271, 274. 275, 283
Gustatoi; oigans. 3561 366
(Ij/Bmoltanala, 66
Vifrti^ncli/Uti, 420, 421

BnlfKTiiptvi, 196

Hnmatin. 155, 157, 213, 316

H:tmiitopoq>hjrin, 155, 213, 21 S,

230, 221, 233. 23S
HEEmerTthrin, 130
UKmerTthrogeii, 130, 156
Hiemochromognn, cfi, 131, 212, 213,

215, 216. 21K, 220.339,244
Hteroocysniti, 143, 143, 147. 166, 167,

168, iSi, 457
Hemoglobin, go, 129, 130, 13], 142,

143. '46. 147. 152-157. 167, 181.

213,218. 223, 225, 226, 238

Hi'iBophtit vorii-x, 87

HromoibodiD, 142

Hearts, 6S, 123, 182, 185, 1S9. 192-

206, 237, 286
Hcliaiithu, anau,, 12
Helicopepsin, 106
Helicorubin, 239
Jltlix, 70-72, 10s, 108, 167, 168, 203,

237. 239, Hi, 279, 283, 340, 365,

366, 368, 448, 449
ffeliJ! aiperta, 105, Iq6, 169

pomaiia, 106, 127, 167, 169, 284,
366
Hemeroladir, 359
Hemirhorilata, 75
St«i<ptera. 433, 435. 438
Hepatochromates. 317, 238
Hepsto-pancraafi, a, loS
Hermapbroditea, 56, 409, 414, 415,

418, 420-439, 439, 442, 443, 448-

451
Hermaphrotiitism, 402, 413
Hermit 'flrabs, the, 58
Heterogeaesis, 399, 406
Hetwopoda, 70, 448

Jtelcrolrleka, 377

Htxapodit, 46

Hirwliiitii, 37, 87, 213, 125,256, J2I,

Btrudo mtdicinalU, 37, 87, 136, ijl.

146. 153, 1S8. 189. 190, 214, *34.

256. 331, 353, 387, 38S, 4)4
Hiiler, 46
HJEtalismatins, 139, 155, 167, 21^

216, 220, 322, 231. 337, 338.15(1

284
HliiTioliddia, 423

Hotolhuria niffru, 147, 148, sal
Jlolothuridea, S4. 219, 324, 249, j».

413, 414. 417
Homtirvt, 59, 104, 137. 166, 167, 179.

'93. 199. 232, 233, 283. 3Ji-33^

363. 3*4. 396
Hone7<bag of bees. 46. 97
^l,ra, 72, 450

flW'-", 3», 34, 81, 297. 37R 409. 4
Bvdrachna, loO, 440
Bylra/atr,^ 79, 80

•driilU, 80, Si
Bwlnaoa. 31-33, l2^ ..,
By-KiKgiUra, 45. 96, 325. 357. ;

394, 433- 435. 438
H^pophatjDs, 42
Bypotricha, 577
Hvpoxai] thine, 14

m..„,

Ityt^crnplMi toHQireiKtu, 5;
Imbibition, 23, 36, 1 17
Imperjwala, 25, 36
Indol, 90, 91
Infandibulaiu, an. 236
Infvtorltt, 12. 26, 34, 81

, ao8, 375, 277, 40s, 406, 407

Injvtona ethala, 36, 29, 41^
^gdlata, 26, 27, 31, 405
tentaeulij'erii, 26, 27. 406
Ingluvies, 43

Inhalent aperture^ 31, iso, 184, 40S
Infe-bag ol .*j..<., 73, 459
Ineeria, 40-43, 64, 91, ia3, HJ, IJl,

«37. 157. 191-195. 3*8. ajot 344,

359. 167, 3*5. 3^. 355- 3Sr ""

393. 404. 42B, 431, 433
Integumeotat^ oraanB, 244
Intermeseuteric chuubers. 33
lotestinal canal, a rnditneniaiTt, yt
luteBtinea, 40, 43. 44. 5tt S«, S3, SS-

56, 65, 87, 270
Intrnductioli, t-9

Invtrtdimta, absorption in, 117-114
blood in, 115-181
ciTcnlatloQ iu, 182-206

SUBJECT INDEX.

471

Invertebrata^ digestion in, 20-1 16
excretion io, 241-292
locomotion in, 374-398
nervoas systems in, 293-344
organs of sense in, 345-373
reproduction in, 399-453
respiration, 207-240

Invertebrate kidney, the, 290-292
liver, so-called, 115

l9ophyUia dipsacea^ 253

hupoda, 67, 363, 396, 428, 444

Ixodes, 47, 439, 440
ricinus, 440

Japyx, 41

Jaws, 40

Jellyfishes, 210

/one, 363

Juice of working bees, 97

•^«^««, 35S» 431

Kidney, Invertebrate, i, 30, 42, 55,
96, 242, 243, 245-248, 254, 256, 257,
259, 260, 266, 275, 283, 286, 290

King-crabs, 50, 457

Lacinxdaria^ 419

Lamdlibranchiatay 67, 1 04, 141, 202,
243. 255» 276, 278, 282, 338, 339,

365» 367, 3^» 448
LampyrU splendidula, 264, 265

Larvae, Lepidopteroas, 162, 165, 262

Phytophagous, 132

LatonopsU^ australis, 54

Leeches, 37

LepaSj 56

2>€pufop^era, 43, 44, 45,63,95, I94.325>

327, 357, 359» 393» 394, 433. 438
LepidopterOj heart of, 195
Jjepidosiren^ 237
LepisomOf 41
Leprcdia foliacea, 236
Lerrueodea, 363
Leuce'in, 13
Leucin, 13, 14, 73, 82, 90, loi, 102,

III
Libellida depre88ay^2j 94,95, 194, 230,

.266, 325, 394, 433, 435
LiheUudidiey 394
Ligula, 45

Limaxflavus, 106, 238, 283, 366
maximu8, 106, 237, 284
variegatuSf 238, 284
Lime carbonate, secretion of, 244,

248, 249, 250, 276-282
Limnadia gigas, 443
Limnams atctgnaliSf 169, 170, 237, 238,

239, 366

Limnocodium Sorliiy 309
LimuluSy 50, 457

eydops, 166, 200
Lingua, 42, 44

Lingula, 67, 201, 276, 338, 339
Liparis aur^fiua, 262
Lipochromes, 148, 149, 152, 153, 157,
167, iSi, 215, 217, 220, 221, 226,

2^6

lAthohiuSy 355, 430
Lithocysts, 306, 308, 350, 379
LUtorinoy 237, 238, 239
Liver pigments, 89, 90
Liver, so-called, 49-51, 53, 57-^3» 67*
68, 72, 73, 88, 91, 100-108, 111,115-
117,217, 238
Living protoplasm, 12 ^
Locomotion in Arachnida, 394

Crustacea^ 395

Jnaeeta. 390

Inverteorata, 374-398

MollMca, 397

Aiyriapoda, 389
Locomotor system of Echinodermntc^

379
Locomotor system of Jleduscf:^ 379

Ijocusta, 390

viridUsimay 229

Locustidce, 357, 358

Loligina^ 367

LoUgo mediUf 205

Lophophore, 65

Lophyropoda, 50

Laxodea rostrum^ 348

Loxosoma, 447

Lucantis certmSf 229

Lumbricun, 87-91, 122, 126, 131, 146,

153, 188, 189, 223, 226, 257, 258;

321, 322, 353, 388, 412, 424
LumbnnereiSf 354
" Lungs," 207, 230, 237, 240
Lutein, 148

MacrobiotuSy 47, 48

ur8eUu9t 439
Macrothrix sninosa, 54
MacrourOy 58-60, 103, 104, 192, 331,

444,446
Madrepora aspersa^ 253
Maqospliosray 24, 26
3Iaja squinado, 138, 139'
Malacobdettay 38, 423
Malacoscolicea, 64
MalacoBtrac(i-y 50
Males, complemental, 56, 443
Malpighian tubes, 41, 42, 44-49, 57,

94-96, 243, 259, 260, 265, 266, 270,

27I1 275, 2S9

472

.SUBJECT INDEX.

Mandibles, 40-43, 45, 51, 58, 60

MantiSy 390

Manubriam of Medusa:, 304-306

Mastax, 35, 39

Material agents in reprodnction, of

Insecia, 433-436
Hazillae, 41-45
Maxillary apparatus, rudimentary,

67
Maxillipeds, 57

Mayflies, 41

Meduscp, 185, 245, 297-310, 349, 350,

378.379, 402, 4". .^
MeUagrina margarittfera, 277

JUelita'at 4J3

artemi8, 262

JUeldontha, 325

Mermitf 39, 428

HeroitomatOj 50

Mesenteries, 33

Metastoma, 50, 58, 60

Metazoa, 9, 30, 32, 221, 245

Micrococci^ 27

Microspectroscope, the, 153, 155, 157,

169, 170-175, 215, 218
Millepora ramosa^ 253
Millipedes, 41
MUnesium, 439
Mimicry, 82
Mopatidrina, 409
Molar motion, 2
MoUusca, 5, 9, 67, 105, 124, 125, 141,

167, 201, 233, 236, 244, 276, 278,

282, 339, 341, 342, 365, 367, 397,

402, 448
MoUusca, glycogenic function in, 1 15

salivary secretions in, 109
Monads, 26, 29, 347, 348, 376, 406
Mona4 vulgaris^ 27
MoHcray 404
MonogtoiHuniy 420
Monticularia, 409
Montijktra foliosa^ 253
Morphological units, 2
Morpholojjy, i
Morula\ 37. 40S, 410. 411, 417, 429,

448
Mucous glands, 245, 2S4
J/wrrA !,<<>« i<i, 450

Mun»xidt\ 247, 24S, 254, 259, 270, 274
J/hjn^i, 326, 390
Musouliir fibrils, 375, 3S7-3S9, 393

pharynx. 35. 40
Mu^oal organs of insects, 433-436
J/yii, 07-09, 104, 105, 2$^ 2S6, 2S7,

Jl/j^i/f, 48

MyohMmatin, 210, 222, 231, 238, 284

MyrianidUf 426

Mtfriapoda^ 40, 41, 46, 123, 127, 180,
192, 228, 260, 324, 355, 363. 389,

430
MurmecdeSy 264

Myrmdeonidaey 359

MytUuSy 67, 104, 105, 141, 234, 237,

238, 398
MgzostomataSf 37, 422

Nais, 79, 424

Naked-eyed Medusae, 29^308

Naticay 450

Natural selection, 250, 288, 391

NautUuSy 74, 202, 367, 370, 451

Nectocalyx of Medtuce, 298, 300^ 302,

304-306, 379
Kemato8coliceSf 38, 39, 227, 323, 354,

389, 426
Nematoideay 38, 39, 86. 127, 227, 259,

323, 354, 389. 426, 428
Nematorhynchay 38, 39
XemaUu veniricotuty 437
Nemertesy 418, 419
I^qphdUy 131, 146
Nephridia, 204, 243, 256, 257, 260^

283-286
Nepkroptty 232
Nepthysy 323
Xereisy 38, 9i».i53» 226
DumerHUiy 152
regioy 322
Nerve-ceUs, 293. 299, 303, 313,

322
Ner\'e-centres, 295, 310, 319
Nerve-fibres, 293, 294, 299, 322,

353
Nerve-plexuses, 299, 313, 317, 319,

327, 351
Nerve-poisons, 309

Nen-e-rings, 311, 316, 318, 321, 323,

342
Nerve-tracts, 296, 302
Nerves, inhibitory, 294
motor, 294
of i/omaru4, composition of, 336-

secretory, 294
sensory, 294

transmission of motor excita-
tion in, 33J-336
N'ascular, 294
Nervous systems, 292-344
Neuro-muscular elements, 297, 299,

302,304,308
ymrofttcray 45, 327, 357, 359, 394,

^.433. 438
.A trMMirr, 359

SUBJECT INDEX.

473

Noctiluca, 27

Naclein, 22

Nacleolns, 403, 407

Nacleus, 22, 24, 180, 310, 401, 407

Nutrition, types of, 21

Nycteribick^ 359

Ohmum^ 442

Ocelli, 329, 359, 361

Ocnua hrunneus, 221

Oculina coranalis, 253

OctopodOf 72, 367

Oct^ma, 72, 105, 142, 144, 168, 179,

202, 234, 239, 286
OdoHtcphora, 70
Odontophore, 69, 72
(Esophi^eal glands, 38
(Esophagus, 34-36, 38-44, 47, 49-52,

55-60, 65, 70, 87, 92
Olfactory organs, 349, 35 'i 352, 356,

361, 363, 366, 367
OtigodiaUa, 37, 38, 87, 90, 223, 256,

257, 321, 388, 424
Omentum, an, 60
OmmttstrepheSf 370
Onehidum, 237
Oniscus, 57, 396
OnychopliorcL, 40, 429
OnychoteuihUj 370
Operculum, an, 155, 157, 45°
(^hiactU viretis, 220
(^hioiepis cUiata^ 416

tqtiamtUaf 415
Ophiura, 385
(^hiuridea, 34, 352, 380, 383, 386,

415, 416, 418
Opkrydium^ 81
Ordiestia^ 243
Organ of Bojanus, 68, 143, 202, 204)

243, 276, 282, 283
Organ of Semper, 366
Organs of special sense, 345-373
Orgyia antiqua^ 262
pitdibundaf 262
OrioateSf 440
Oriffin of life, 456
Orthoptera, 41, 42, 46, 63, 194, 327,

357, 394, 433. 435
Oryctes nasicornis^ 135, 136

Oscula, 31, 243, 408

Oatracoda^ 55, 63, 192, 442, 443

Ottrea, 67, 69, 104, 105, 234, 237,

238, 283, 397, 448

Ovipositor, a modified, 45

Ovipositors, 356, 438

Oxychlorocruorin, 154

Oxyhemoglobin, 131

OxyurU amhigua^ 427

207, 240,

Pagarui, 233, 412, 446
PaauridcPf 58, 446
Paueodictyoptera, 43
Palcemorif 59, 104, 396
Pallium, 66, 70, J65
Palinurus qtutdricornUf 234

tndgaris, 138, 178
Palpi, 42-45. 67, 361, 441
PatvdiceUa, 66

Paludina vivipera^ 169, 170, 237-239
Pamphagus, 25
Pancreas, the Invertebrate, 35, 38,

40, 49-51, 55-58, 60, 64, 67, 72, 73.

76, 88, 91, loi, 103-108, III, 116,

238
Pancreatin, 82, 89, 96

Pandora^ 448

Pantostomate being, a, 26

Papilio feronia, 392

Machaon, 162

Paraglossse, 45

Paramceciay 20, 30, 81, 120,

346, 375, 407, 408
. Parapodia, 224, 388, 426
\ Parenchyma cells, 265
Parthenogenesis, 401, 415, 419, 431,

436, 437, 447
PateUa vulffota, 72, 105, 108, 237, 238,

239, 284, 285

Pearls, formation of, 277

Pectetif 67, 104, 368, 448

PectoMtraca^ 50, 56

PetliceUinay 447

Peilicidida', 359

Pelagic organisms, 250, 251

Pelodtttetf 426

Peneliina, 363

Pentacrinin, 216

Pentattotnida, 439

Pentadomum^ 47, 439

Peptones, 93

Perforata, 25

Pericardium, a, 191, 193, 282

Peridineo', 347, 376

Peripatus, 40, 260, 322, 324, 429

Penplaneta, 265, 325, 326, 327, 431,

„432. ,
Peritric/uty 377

Perivisceral cavity, 122, 127, 128
129, 189, 200, 224, 236, 256, 276

Perlidw, 394

Phallusia menttda^ 76

Pharynx, a, 35-40, 48-50, 65, 87, 236,
239, J87. 388

Ph<ucolosma eUmgatum^ 130

Phiogophora nuticulosa, 1 58-16 1

Pholas, 6 J

PlioLcus rtvulatuSf 49, 166

SUBJECT INDEX.

I'Uoromi. 37. 146, '53
Pbospborescence and digesCioD, 27
Pbotogenic organs, 264
Fhryganlilie, 359
Fhrifxtfii. 363
Phylaiiotitninia, 65
PbrUocyBitin, 236
Phjllodoce-^^D, 335
Phyliodore viridin, 234, 236
PhgUopoda, 51-54, 167, 196, 231, 371,

328, 395
PhjBiolDgi(^ labour, divIsioD «f, 8

Fhysioloo;;. animal, I
Phyeopoda, 42

Pbjtophagoua larvie, 133, 133
PignieQti<, liver. S9, to8

respiratory, 210, 314, 316, 318,
22J, 315. 337, *33. 236, 337
Pililiinm, 419
Pinnx, 398

iquamotn, 143
fill'. 411, 446
i-to-ona, 352. 387,418
Ftaaaria UAenoidet, 3S7
Planorbii, 146, 170
Flannta, 41 1

Plalyairriniii pngnna. 138
Pleoinorphism, 453, 455. 456

1,450

Foisoiiii. a

Phu

Phtc , .
I^ollinnata, 64
PoJ«rid.r. 359, 433
PoisOD'clawB, 41, 268
of Hymrnoptera, 45

'-- "ction of, on JfeJunc, 309
JWta tanguiniliTa, 146
JUittti gnllica, 437
Pagchu^e, 37, 38. 91, 131. IS*. 190.

191. 334, 333, 333, 388, 436
Pblydatmui, 363
Po/yii**, 38, 153. 191. 226, 322
PaiyoplahiJmuM, 354

PolyperjthriB. 210, 218

I\iypUicophora, 69, 70, 368, 44S

l\ily»lem«m, 420

iWjweiiin. 431

Pilfyaia, 64, 65, 134. 127, 167, 200,

^35, 338. 447
Ponlia-brauioi; alimentary canal of,

94
PaHiobiklla, 153, 225. 326
ibj-i/frn. 30, 32. 79, Si, 120, 137, 184,

209, 243. 245. 248, 396. 349, 378,

40S
iWi(M rfdpnri'rt, 353
Btnn'la, Si
iViapw/M, 334

Proboscis, 37, 38, 42. 44, 76. 91. pt,

.156
PrKlmAa, 418
' Prolamoibii, 405
Protoplasm, cnemistty of, to-19
ProtniAuta, 24-26, 41^
Prolotradieata, 40, 260^ 324
Prolula. 426

ProventricoluB, a, 38, 43, 70* 93
iVo((Kw),4,8,3i, 33.31,79, iiftlfT,

182, 183. 208, 243, 245, M6. m-

346. 347,375.401.404
Pseado-fitana, 405
P&eudo-luemal ve««els. 133, 129, 15;,

187. 191-103, 223, 224, 240
Fseodo- hearts of Bnchiopodi, 270
Psendo-navicelisB, 405
Fseudopodu, 25, 36, 38, 39. 119,346.

374. 375
J^rA*. 437
Ftcropoda, 70, 73, 337. 367. 367,

398.450
Plyalin, 93

PiUmonary sacs, 204, 240
Pultnor/aileripoda, 70, Jl, XJJ,

Mi. 366. 368. 44S

Pupre, 45, 46, 438

1 Bucfjiluiiur, 133, 134, I

QuEi

BE larvB, food of. 9S
I, 36, 28, So

JtaJiolarii

Badola, a.

Rapkiiliilix, 359

RsiuoD in Araehnuta, 371-373

In4fiia, 371-373
Rectal glands, 42, 43. ajo
Rectum, 42-45, 60, 70, 94, 270
Renal organs, 30. 68, 143, lOi. 1
243, 245, 247, 248, 154, 357. i
360, 266. 275, 276, 2S6
Reproduction in AHoeHila, 421

Araehmda, 439

Itraehiopoda, 447

Cirimlerala. 409

Cnulaeta, 442

EcKincdennrila, 412

/nM«fo, 43 (

lara-Ubrata, 399-453

J/oflwca. 44S

llgriapoda, 430

.Veina(oMU<*Gr<, 426

OnueJiapiuira, 429

iWi/ioa, 447

SUBJECT INDEX.

475

Reprodaction in Porifera^ 408

Protozoa^ 404

TrichoicoUees, 418

Tunicata, 452
Respiration, activitj of, 233
Respiration in Annelida^ 223

Arachnidaf 230

Brachiopoda^ 236

CtelenUratOj 209

Ou«toeea, 231

EcUinodermata, 219

InsectOf 228

InvertthratOy 207-240

MoOwcaj 236

Myriapoda^ 228

.NemcUoscoliceSt 227

^3(«>«» 23s

Iiarifera, 209

Proinotif 208

TV/c/Mwoo/iioet, 223

Tunicata ^ 239
" Respiratory bloo<l," 129, 188
Respiratory piemen ts, 210, 214, 216,

218, 223, 226, 227, 233. 236, 237
Reversions, 36, 39, 56. 112, 205, 344,

Bhabdocffla, 386, 418
Bhabdopleura, 64, 65
Jihizocephala, 56
Bhizopoda, 34, 119, 120, 183, 208
Bhizostoma^ 212
Cuvi'eri, 211
Rhodophan, 148
Bhf/Hchota^ 43
Bciifera, 35, 36, 39, 187, 224, 320, 352.

, 387,419

Rudimentary digestive system, 32
intestine, 30

^6eW«, 130, 153, 154. 155, 322, 323

ventriUtbrum, 130
J^igarlia hellU^ 212, 216, 217

dianthvH^ 212, 216

parasitica ^ 212, 216

troalodytes, 212, 216

induatat 212
HafiiHa, 39, 40, 324, 354, 4*9
Salivary glands, 38-50, 60-70, 73, 87,
91-116

secretions in Molln^ca, 109
Barcode of ^fii<e6a, 3
^fer*ia, 300, 302, 304, 310, 349, 350,

378
tubuiosa^ 301, 302

Savigny tnbales, the, 76, 113
Scalpellum, 443

ornatumj 56

rostrattim, 56

Scafjpellvm,mdgaref 56

JScaphopoda, 69, 70, 368, 448

iSban, 249

Scohpendra, 430

ikoiwpendrida^ 355

Scorpio, 166, 192, 23a 231, 268, 361,

442
JScutigera, 228, 355
Scyphistomaf 41 1
Secreting glands of bugs, 263
Secretion in InvertebrcUa, 241-292
Secretion of lime carbonate, 244, 24S,

250, 276-282
Secretion of silk, 264
Segmental organs, 243, 256, 257. 258,

260
Segmentation of vitellus, 403, 404
Sense-or^jans, 345 373
Sepia offtciiMUs, 72-74, 109, I ID, 112,
142, 143, 168. 177, 204, 286, 339.
370,451,452
Serpula, I53-I57» 523

oofUortuplioatUf 155
Setae, 40, 353, 361, 388
Shell-glands, 52, 55, 243, 271
Shells, structure of, 277
Siphonophora, 433-435
Siphonoatoma, 130, 153
SipunctUus, 129

balanorophus, 130

echinorhf/ndiWt 130

nudus, 129, 130
Sitona criiiitq, 357

lineata, 357
Smerititfius oceUattiSy 162, 16^

pomdi, 162

tiUce, 162, 163
Sodium urate, 256, 271
Solaater^ 380

papjx)8a, 221
Solecurtus ttrigiUahtSf 238
Solen legumen^ 146, 238
SolenobiOf 437
Somatopleure, 187
Sounds produced by insects, 360,

, 433 436
Spatangiu, 386

Spectra of Invertebrate blood, 150,

I54» 161
Spermatozoa, various, 412
Sphasrularia^ 428
Spluerozoum^ 26
Sphiiix Liguitri, 132, 134, 135, 161,

163, 195
Spider, heart of, 196
Spines, chitinous, 40
Spinning glands, 44, 48, 245, 268
i^iroggra, 12

476

SUBJECT INDEX.

Spirotlonum. 37S
SplancbDoplenre, 1 67
lix/nilida. 30, 184, 209, 349, 378
Spongilln, 31, Si, 209
SpoDtaneous generatian, 399, 40a

Stenlfir polymarph
&^haiioetroi, 3S7
&ernarpit, 224

Stelheophytna i/rottum, 194

Stigmata, 22S, 331

Btiing, bee's, 45

Stomach of Antaewi, 61

Stomacha, 40, 42, 44, 48, 51, $6, 58,

59, 65, 66, 67, 70, 72
NtomapiKla, 44
lSfI^l»(lpCe^a, 317
Stridnlation, 433, 435
^roj^i/d, 411

iStroiu^ioMntrotui fiuiJtu, 149, 150
Svokerg, 38, 36
Boetentative fanctjons, 2, 3

t«M, 426
napra, 414
Ejntnesis of albumin, 1 1
Si/riphidit, 433

Taaiu, 36, 320, 402
rranfiaiUu, 320
ropAn^DCfro, 320

■HTTiail, 85

(raHweraii^Tf, 32a
Tuitirt, 396

Tape-worms, 36, 37, 320, 402
Tanligardo, 47, 439
Taurocbolic acid, 101, 103, 112
leetb, cbitinoua, 37, 38, 42, 5$, 68
T^geaaria domtUica, 49, 100, 166,

Telson, 50, 331, 396

Tentacula, 2*^ 29, 37, 40, 64, 65, 366,

379. 3S7. 39S
TcnlacidifeTa, aS
TtrtMUt, 153, 216
TtrAratvlii, 33K, 339
Ttrebralidiiui stjitenirloiialU, 276
leredo, 283

Ttthj, fimbria. 143. 169
H^rabraiidiinta, 72, 74, 236, 341, 367

368. 369
relramilm roilratiu, 406
TetroDerjthrin, 14S, 149, IJ7
TctHgida, 435
T^aloMema, 224

TluiluMiaiBa, 80
Thoracic feet, 57
I Thread- worms, 39

Thript, 41
' Thyiaaaro, 41
'Aarepfi» indieam, 305
iydijdiademata, 3O2
, Tiasue-respiration, 108.118,331, 1J7|9
240
TrachefB, 40, 137, 207, arf, 229. 1;

240, 260, 264, 365

Trcmalala, 35, 36, 86,

4K^ 411, 4". 413

352, 386, 418
TrtomiH. 397
Tr!MiUa, 51, 400
Troohal disc, 35. 387, 419
TVotAw. 366

ci'iMraniM, 238
7V<nii6«liun>, 440
Trypdn, 81. 86, 89, 96
Tiibieol'i, 354, 388
Tabiftx. 424
7\ini«Ua, 7S. 1 13. aos. ^39. 145. J4i J

Tnrtiaiiella, 39, 1

7>irW/ar(.t, 35. 36, 320, 352, J

».■«'''

IWio, 366

Turril^a, 450

Types of nuirition,

Ijphloaole, 69, 70. I ,

Tyrosin, 13, 14, 73, Sa, 90, 101, 1

UUBHBLLA of Maliua, 298, 299

Vnio, 105, 237. *39. ^79
Units, morphological, 3

phjaiologiciO, 3
Vraiter mbent, 4, 83, 85. 220, 2S4i

380,41s
•■ Urate cells," 265

Urea, 13. 252. Z65. 279, 2S2, 2S4, 286
Urio acid, 13, 96, 246, 247, 34S, i}*,

^56. 257, 259, 265, 266. 267, ija,

271. 274, 279, 281, 2S3-186
Vrochonlaln, 75

Vascular systems, 35, 182, tfic, 189

Veil of i/eJuw, 298

VdfUa, 81 ^H

SUBJECT INDEX.

477

Vtrmfy 404
FJermrfti*, 366
Fermt/ia, 323
Vertebrates, cranial, 89
Vttpa^ 260
Voice*organ8, 360
VcluXa^ 4^0
VoTiex viridiSf 81

Varticella;, 28, 29, 249, 247, 296, 375»
377» 407

Waldheimia, 276
Water- vascular systems, 35, 187, 223,

240,243
Web-spinning, objects of, 99

Wheel-animalcules, 35
Worms, blood of, 153

Xanthine, 14

Xanthopbjll, 132, 134, 135, 163, 165
Xanthoproteic acid, 101
Xiphoiura, 50, 63

" Ykllow cells," 80, 81, 215-219

ZOANTHODEMES, 33

Zoophytes, 234
J^gnama, 433
Zyynema^ 12

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