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THE LIBRARY

UNIVERSITY OF
WESTERN ONTARIO

THE J. D. BARNETT
TEXT- BOOK COLLECTION

University of Western Ontario
LIBRARY

LONDON - CANADA

Class LX\oO\

DATE DUE

uuc

UGGIST
& STATIONER,

DIPAQP

LIBRARIES
THE UNIVERSITY OF WESTERN ONTARIO

LONDON CANADA

LS-60135

HIGH SCHOOL
ZOOLOGY.

AN INTRODUCTION

TO

ZOOLOGY.

FOR THE USE OF HIGH SCHOOLS.

EY

R. RAMSAY WRIGHT, M.A., B.Sa

Professor of Biology in ttte University of Tortmto.

^Toronto :

THE COPP, CLARK COMPANY (Limited).

1889.

Entered according to Act of the Parliament of Canada, in the year of our Lord one
thousand eight hundred and eighty-nine, by Thk Copp, Clark Company (Limited),
in the Office of the Minister of Agriculture.

T6 54-

PREFACE

The present volume has been prepared with the object of aiding the
study of Zoology in the Ontario High Schools. Already, one branch of
Natural History — Botany — has been introduced with gratifying results,
and it is thought that the addition of the elements of Zoology to the
course may similarly awaken a wide-spread interest in animal life
throughout the Province.

The plan of treatment adopted is substantially that of the Syllabus
prescribed by the Education Department. Attention is first directed to
the Vertebrates as the most familiar and conspicuous animals, but the
essential characteristics of the chief groups of Invertebrates are also
given, the greater amount of space being, however, devoted to such
groups as have terrestrial or fresh-water representatives. In each of the
classes of the Animal Kingdom, some easily obtainable form is employed
as a type in which to point out the more obvious structural features of
the class, and it is assumed that these will be verified by actual exam-
ination.

A number of figures have been introduced, partly with the view of
facilitating such examination, partly to illustrate the less accessible
forms. These have, for the most part, been copied from scientific
works like the publications of the U. S. Fish Commission, Brehm's
Thierleben, etc., but a few have been drawn for the occasion, Figs. 1
and 58 with several others, being from the pen of Mr. E. E. Thompson.

Much of the educational value of Botany as generally taught in
schools results from the accurate observation necessary to employ the
terminology correctly, and to make correct diagnoses : Zoology does
net lend itself so easily to this kind of exercise, but it affords an

VI PREFACE.

equally valuable discipline — the tracing of the modifications of form
throughout less nearly allied groups. A good deal of space has, accord-
ingly, been devoted to this aspect of Zoology, although other aspects
which may excite the interest of the young student have not been
neglected. For example, the chapters on the Reptiles and Birds give
prominence to the remarkable geological history of these classes ; that
on the Mammals, to the correlation of form and habit in the group ;
while the last chapter aims at showing the connection of the various
subdivisions of zoological study.

Experience alone will show, what form zoological instruction in the
Secondary Schools ought to assume, so as not to interfere with other
departments of study : the text-books on the 4 ' type-system " seemed to
be too advanced for the present purpose, and also not to afford as wide
an acquaintance with the forms of Animal Life as is desirable, while
many elementary, systematic text-books prepared for school use dc
not demand the actual examination of types, so necessary for the
formation of clear conceptions. It is hoped that the present volume
which endeavors to combine the advantages of both systems may prove
adapted to the purpose for which it is intended.

Eorontou My, 1889,

CONTENTS.

Pagb.
Chapter I. — The Structure of Vertebrates, as exemplified in

the Catfish 9

Chapter II. — The Classification of Canadian Fishes 51

Chapter III. — The Structure and Classification of Batrachians . . 80

Chapter IV. — Account of the Organization of the living and

fossil Orders of Reptiles 90

Chapter V. — The Organization of Birds as exemplified in the

Fowl, with the Characteristics of the Orders of Birds 121

Chapter VI. — The Structure of the Cat as a type of Mammalia,

with an account of the modifications of form in the Class 142

Chapter VII. — The Crayfish, Spider and Grasshopper as types of
the Morphology of the Arthropods, with the Characteristics of
the Orders of Arthropods 190

Chapter VIII. — The Vermes, Mollusca and Molluscoidea 218

Chapter IX. — The Remaining Invertebrate Sub- Kingdoms 242

Chapter X. — General Principles of Zoology 261

HIGH SCHOOL ZOOLOGY.

CHAPTER I.
The Structure of the Catfish.

1. Botanical students will remember that plants are often
subdivided into phanerogamic and cryptogamic forms ; the
latter lack a cei'tain characteristic way of producing seeds
which is present in the former, but they really embrace several
distinct primary subdivisions of the Vegetable Kingdom, whose
only common character is the negative one referred to above.
Similarly the Animal Kingdom is often subdivided into Ver-
tebrate and Invertebrate animals, but the latter really in-
clude several distinct sub-kingdoms sharing the negative char-
acter of the absence of a backbone. Although, then, the Bo-
tanist and Zoologist regard the terms cryptogamic and in-
vertebrate as survivals from a period when less was known as
to the structure of the contained forms than there is now, yet
the terms are very convenient for every-day use, because they
separate the less important, i. e., the lower and less conspicuous
members of the Vegetable and Animal Kingdoms f.om those
which are not only higher and more familiar, but also more
economically important.

2. The history of Botany and Zoology teaches us that for
various reasons these sciences have progressed most rapidly at
first with the study of the higher forms of life : similar reasons
will render it more convenient for us to begin our study of
Zoologv with an examination into the structure of a Vertebrate

*2

10 HIGH SCHOOL ZOOLOGY.

Animal. In making our selection, however, it will be desir-
able to choose a form which shall be so far typical, that a
knowledge of the structure of its various organs will enable us
to interpret the nature and significance of the comparable Or
homologous parts in other Vertebrates. No one animal is
best in every respect for this purpose, because there is no animal
which unites in itself all the characters which we regard as
primitive or general. An example will render the meaning
of these terms plain. Most Vertebrates have five fingers on
the hand, and we regard that as a primitive or general arrange-
ment in comparison with that in a cow where there are two, or
in a horse where there is only one. Such a reduction in
number we regard as a specialization associated with the
function which the hand performs, and it is very much easier
to interpret correctly the specialized condition if we have in the
first place familiarized ourselves with the more primitive one.
Our object must then be to find some fairly primitive form,
which is common, easily obtained, and easily studied : our de-
mands in all these respects are pretty well met by the common
catfish, the angling for which is attended by no great difficulties,
which is tenacious of life and easily kept in captivity, and
which finally occupies such a place in the class of the Fishes
that we can, after acquainting ourselves with its structure,
survey the other members of the class, and proceed to the study
of the higher Vertebrates.

3. General Form. — AH Vertebrates, like most Inverte-
brates, are bilaterally symmetrical animals, i. e., the body
is divisible into right and left symmetrical halves by a plane
passing from head to tail through the middle line of the back
(or dorsal surface) as well as through the middle of the lower
(or ventral) surface. This is the median sagittal plane ;
planes at right angles to it, which are parallel to the dorsal
and ventral surfaces, are called horizontal, while those which
transect the body at right angles to both are frontal.

HIGH SCHOOL ZOOLOGY. 11

Different regions of the body have different duties to dis-
charge, and consequently differ in form and structure. We
distinguish in a fish the head, trunk, and tail, of which the first
lodges the brain and sense organs, secures food, and shelters the
gills, the last is chiefly locomotive in function, while the trunk
differs from both in being hollowed out so as to enclose the in-
testines and other viscera in the so-called body-cavity (ccelom).
The regions referred to are said to be axial, because they are
disposed round the chief axis of the body, while the two pairs
of limbs or appendages, much more developed in the higher
Vertebrates, project laterally from the trunk, to which they are
attached in the neighbourhood of the cephalic and caudal
regions respectively, and are described as appendicular.
In a fish the anterior and posterior appendages are known as
the pectoral and ventral fins, (Fig. 1) from which are to be

Fig. L— Common Catfish, or Bullhead. J.
Amiurus nebulosus.

distinguished the unpaired fins, occupying the middle line
of the dorsal and ventral aspects of the trunk and tail, and as-
sisting in locomotion. The latter are named from their posi-
tion dorsal, caudal and anal. In the catfish, part of the dor-
sal is separated as the adipose fin, which is regarded as the
rudiment of a longer dorsal, and, instead of being supported
by fin-rays, has only fatty tissue within it.

4. Apertures. — Certain apertures exist on the surface of
the body ; of these, the mouth is bounded by the upper and
lower jaws and leads into the mouth-cavity, the nostrils or

12 HIGH SCHOOL ZOOLOGY.

openings of the olfactory sacs are four in number on the dorsal
surface of the head, but there are no external apertures for the
ears. On the ventral surface in front of the anal fin is the
posterior aperture of the intestine, and immediately behind it
that of the urinary and reproductive organs. On the sides of the
head behind the mouth are certain large apertures — the gill-
slits, five in number, opening into the cavity of the mouth,
but these are ordinarily concealed by the gill-cover or opercu-
lum, a flap which projects backward over them, and by a
membrane attached to the inner surface of the flap, the branch-
iostegal membrane. In this way the gill or branchial
chamber is formed, opening by the branchial aperture along
the hinder and lower border of the said flap. Both the
branchiostegal membrane and the gill-cover have a supporting
framework of bones, the branchiostegal rays in the one case, the
opercular bones in the other.

In addition to the olfactory organs referred to above, the fol-
lowing sense organs are to be noted : the eyes ; certain holes
and slits along the lateral line and on the head leading into
canals and pits in which sense organs are situated ; and the
barbels, sensitive processes of the skin of the head, eight in
number in the catfish, but frequently absent in other forms.

5. In most fishes the skin is strengthened by bony scales,
either round in outline — cycloid — or with the hinder margin
toothed— ctenoid — (Fig. 2), but the catfish is destitute of
such, except for certain very minute ones which are in the
walls of the lateral canal. The skin is therefore soft and
slippery, and variously coloured according to the distribution
of pigment in it. It is tightly bound down to the underlying
flesh by slips of fibrous tissue, but in certain parts some loose
subcutaneous tissue is accumulated between them. When a
sharp cut is made through the skin it is possible to recognize
two layers, an outer, the epidermis and an inner, the corium,

HIGH SCHOOL ZOOLOGY. 13

which layers indeed exist in the skin of all Vertebrates. It is
chiefly but not exclusively in the latter that the pigment is
contained. If the epidermis be removed by scraping, the ex-
posed surface of the coriurn will be observed to be rough with

a. B.

Fig. 2.— A, Cycloid Scale from Lake Herring. B, Ctenoid Scale from Rock Bass. 6/1.

papillae, so that the smoothness of the surface is due to
these interpapillary spaces being filled up with the epidermis.
The papillae are of importance as the channels through which
nerves and nutriment from the blood-vessels reach the epidermis
from the corium.

6. Minute Structure of the Skin.

General Remarks ox Histology. — That branch of the.study of the
structure of animals which deals with the minute elements of the various
organs, and which requires the microscope and other tools in the course
of its investigations, is termed Histology. Each organ of the body-
is built up of tissues, and each tissue is formed of ultimate elements
named cells arranged in a characteristic way. Thus the skin, which is
a complicated organ performing very different functions, is composed
chiefly of two kinds of tissues — the epithelial tissue of the epidermis,
and the connective tissue of the corium. The former may fairly be con-
sidered its most characteristic tissue, but both are necessary elements
in its structure. It is still more complex, however, in virtue of the pre-
sence of both muscle and nerve tissue, so that this one organ of the
body contains tissues of all the four categories under which histolo£?sts
arrange the component parts of the animal body.

14 HIGH SCHOOL ZOOLOGY.

7. Animal cells have the same component parts as vegetable cells,
i. e.t they are formed of a protoplasmic cell-body containing a nucleus
and limited (frequently) by a membrane or wall. The latter, which
plays so important a part in the support of the plant, resigns this func-
tion in the higher animals to the intercellular substance, which, although
like the cell- wall formed by the activity of the protoplasm, differs there-
from in rarely exhibiting the territories belonging to the constituent
cells. All the cells of the animal body are, like those of the plant, de-
rived from the division (and the differentiation of the products of the
division) of one cell — the egg-cell, and the first results of such division
and differentiation are the formation of embryonic layers somewhat
analogous to the primary meristems of the plant-embryo. Perhaps the
most characteristic difference between the plant and animal embryo is
that in the latter some of the most important organs are developed by
the infolding of the originally superficial epithelial layer.

8. The four categories under which animal tissues fall may shortly be
characterized as follows :— (Fig. 3.)

I. Epithelial Tissue is that which is disposed in the form of one
or more layers of distinct cells on the free surfaces of the body, including
the alimentary canal, the lining of the coelom, the cavities of the nervous
system, etc. The cells may be cylindrical, columnar, cubical or scale-
like in form, their free surfaces may be covered with a resistant cuticle,
or provided with delicate continuations of the protoplasm in the form of
cilia or hairs. If their duty is to receive impressions and transmit
them to nerves, they constitute neuro-epithelium ; if they secrete
some characteristic product they constitute glandular epithelium,
and are generally turned in from the free surface for protection ; if they
serve merely to form hard structures for protection of underlying parts
or for defence, they are modified into horny epithelial scales, feathers,
hairs, hoofs, nails, horns, etc., while if they are converted into eggs,
etc., they constitute germinal epithelium.

II. Connective Tissues. — These constitute the framework of the
body, which in some organs is of the utmost delicacy, in others, the true
skeletal tissues, attains great firmness and hardness. Sometimes the
cellular elements are distinct, in which case they may be free to wander
through the interspaces of the tissues in the form of amoeboid or
wandering cells, or be more limited in their mobility like the pigment-
cells; or be fixed and flat like epithelium, or globular and filled with fat,
or branched and communicating with their neighbours. Sometimes in
the adult tissue the protoplasm is almost all converted into intercellular

HIGH SCHOOL ZOOLOGY.

15

Fig. 3.— Illustrations of the Simple Tissues of the Catfish
1. Egg, as type of an animal cell. 2. Scale-like epithelial cells from skin. 3. Col-
umnar ones from intestines. 4. Neuroepithelial and supporting cells from ear. 5.
Loose connective tissue formed of branched cells (b) with fat (a) and pigment-cells (c).
6. Blood cells ; a, colourless, b and c coloured. 7. Cartilage. 8. Bone 9. Tooth with
pulp-cavity, dentine and enamel-cap. 10. Simple muscle-cells. 11, Striated muscle'
fibre. 12. Nerve-cells. 13. Nerve fibre,

16

HIGH SCHOOL ZOOLOGY.

substance, in which case nuclei with a scant surrounding film of proto-
plasm are left embedded in a matrix which may be soft and jelly-like,
or converted into fibres, or stiff and homogeneous like cartilage, or hard
through incorporation with lime-salts like bone and tooth.

III. Muscle-tissue.— The cellular character is to be seen in the simpler
kind which is formed of much elongated cells, whose protoplasm is
highly contractile, while the higher kind of muscle-tissue is that termed

striated (from the appearance of the contractile substance of the fibres
under the microscope). In the latter, each fibre is a unit of higher
rank than the simple muscle-cell, beeause it is the equivalent of several
cells.

IV. Nerve-tissue. — Two elements are distinguished, nerve-cells and
nerve-fibres. The cellular character of the former is always evident ;
the latter are to be regarded as processes of these cells, each nerve-
fibre having for its core an
axis-cylinder continuous
with the cell protoplasm,
which serves for conduc-
tion, and is generally isolat-
ed by one or more sheaths.

9. Histology of the

Skin. — The microscopical
examination of a thin pre-
pared section of skin dis-
closes at once the two chief
component parts (Fig, 4).
Of these the horizontal fibres
of the corium are separated
from the epithelial layers by
a looser connective tissue, in
which pigment cells are
abundant and which pro-
jects into the papillae. Some
looser fatty connective tis-
sue may separate the hori-
zontal fibre-layers from the
flesh. Filling up the inter- ¥igm 4._Diagram of section of the Skin in the Cat-
spaces between the papillae fish- EP» epithelium ; pap, papillary layer of
i.u 'j-t. v i u * *ne corium, co; sc, subcutaneous connective

are tne epithelial cells of tissue, with nerves and blood-vessels. X5Q.

HIGH SCHOOL ZOOLOGY. 17

the epidermis ; these present several varieties in shape and function,
those next the corium being columnar, those on the free surface cubical,
while the intervening cells are intermediate in shape. Certain peculiar
cells stand out from the others ; these are the slime-cells present in all
fishes, which provide the skin with its covering of mucus, and the cla-
vate cells of unknown function, occurring chiefly in fishes with a soft skin
like the Eel and Burbot. A few pigment-cells wander out from the corium
into the interspaces of the epidermis. Finally certain special epithelial
cells are to be found in bud-like groups on the end of some of the papil-
lae. Each of these is provided with a delicate hair-like process at its
tip, and is connected with a nerve at its basal end ; they thus belong to
the class of neuro-epithelial cells and they constitute the simplest form
of sense-organ in the fish. It is supposed that they are affected by
vibrations in the surrounding medium, and that they are tactile in
function. That this is so may be inferred from the use to which the
barbels or feelers, which are covered with these organs, are put. Else-
where on the surface of the fish, groups of similar cells occur, not pro-
jecting freely on the surface, but retracted for protection into minute
sacs opening by slits on the surface, or projecting at intervals into the
cavities of the sensory canals of the lateral line and head, which com-
municate with the surrounding medium by distinct pores. The button-
like hillocks of neuro-epithelium are generally protected by a bony
scale, and it is the fusion of such scales which gives rise to some of the
skin-bones of the head.

10. Skeletal System. — In the course of the above para-
graphs reference has been made to bones developed and situated
in the skin. When such bones acquire no connection with the
deeper parts they are said to belong to the exoskeleton ; the
rough teeth in shark's skin, and the scales of a white-fish,
e. g.y are of this nature. It is evident from what has been said
that the catfish is very poorly provided with exoskeletal struc-
tures ; all of its bones belong to the internal or endoskeleton-

11. The skeletal system is formed chiefly by tissues of the connective-
tissue group, viz., fibrous connective tissue (in the form of ligaments and
membranes), cartilage and bone. Of these the cartilage plays onbr a
transitory part in the development of the catfish's skeleton, both it and
the fibrous connective tissue being in great part converted into bone.
Teeth are true exoskeletal structures, although they are only found ia

18 HIGH SCHOOL ZOOLOGY.

connection with the internal skeleton in the catfish : we know this by
the development of their two constituent parts, the dentine — a member
of the connective-tissue group allied to bone — and the enamel, which is
formed by the modification of epidermal cells. (Fig. 3.)

12. In the skeleton we distinguish axial and appendicular
parts, § 3 ; to the former belong the skull with the hard parts
of the gills, and the vertebral column with the ribs.

We shall study the latter first ; it is formed of a series of
separate bones, the vertebrae, which vary considerably in
form in different regions of the column, but are all characterized
by a central part (the body or centrum), which is hollowed out
like a cup, on both anterior and posterior faces, (amphiccelous.)
(Fig. 5.)

Fig. 5.— Caudal Vertebra and Caudal end of Vertebral Column in the Catfish.

Ns. neural spine ; c, vertebral centre ; hs, haemal spine ; nsh, bony sheath of the

notochord ; cr, caudal rays.

Within the space so formed is contained the gelatinous remains of the
notochord, a rod present in the youngest stages of all Vertebrates,
around which the vertebral column is built, but rarely continuous in the
adult, except in the lowest Vertebrates.

Each centrum bears on its dorsal surface an arch, the
neural arch, which terminates in a neural spine. The series of
centra constitutes a flexible rod of great importance in loco-
motion, the series of neural arches forms a canal serving to pro-
tect that part of the nervous system known as the spinal cord.

HIGH SCHOOL ZOOLOGY. 19

while the series of spines (to which the common name of
spine, spinal column, etc., for the vertebral column is due)
chiefly serves for the attachment of muscles. In higher Verte-
brates not only are the centra intimately united to each other,
but the arches have certain projections (articular processes),
forming joints with similar processes on the arches in front and
behind. These are not very much developed in the catfish,
but this mode of union permits a certain amount of rotary
movement between the vertebrae, to which the word vertebra
owes its origin.

In all fishes there may be distinguished in the vertebral column
two regions, the trunk and the tail, the former extending as far
back as the coelom referred to above, the latter behind that.
In addition to the neural arches and spines, the caudal vertebrae
have haemal arches and spines, which protect the blood vessels
running back through the tail below the centra, while the trunk
vertebrae have ribs which generally protect the contents of the
ccelom, but do not meet below nor carry spines.

The ribs are not articulated directly to the centra, but to projections
from them, transverse processes, which appear to be the real represent-
atives of the haemal arches.

Some of the anterior trunk vertebrae in the catfish and
its allies are very different from the others, being modified in
connection with the organ of hearing, and in all fishes the most
posterior vertebrae are altered in connection with the tail. The
special way in which this alteration affects the catfish may be
seen in Fig. 5, as far as appearance goes the rays of the caudal
fin seem to be equally divided above and below the end of the
vertebral column, (the fin is said to be homocercal), but in
reality the tip of the vertebral column turns abruptly upwards
so that most of the rays are really on its ventral surface. We
shall see that in certain other fishes this unequal division of
the tail-fin is much more apparent (heterocercal).

20 HIGH SCHOOL ZOOLOGY.

14. It is in the vertebral column that the segmentation or
metamery of the Vertebrate body finds its most evident ex-
pression, but we shall find that many other organs are likewise
divided into metameres, notably the muscular and nervous
systems.

1 5. A study of the development of the catfish shows that not
only is the vertebral column built around the notochord, § 12, but
also that the same is true of a considerable part of the skull,
and that the notochord in the head is related in the same way
to the nervous system and alimentary canal as it is in the
trunk. It was at one time thought that it should be possible
to distinguish constituent vertebrae in the skull, but this is
impossible, for the very different functions which the anterior
part of the axial skeleton has to discharge are associated with
corresponding differences in form. Thus the fact that the
anterior end of the central nervous system is dilated into the
brain, is associated with the development of a sheltering box,
the cranium, which is further modified by the apposition or
incorporation with it of the protecting hard parts of the higher
sense-organs, and the fact that the anterior end of the alimentary
canal is devoted to securing food and to respiration is associated
with the development of certain hard parts in connection there-
with— the visceral skeleton. Of these we shall study first —

16. The Cranium. — The cranial box has certain openings,
one (the occipital foramen or foramen magnum) to permit of
the spinal cord joining the brain, others to allow the escape
of nerves and the entry or egress of blood vessels. Although
originally in the young fish largely cartilaginous in its texture,
the box afterwards becomes partly converted into bone, and
the bones formed in the cartilage are related in a definite way
to these openings. Other bones are formed in the skin for the
protection of the sensory canals ; still others (especially in the
roof of the mouth) for the support of the teeth, and both of

HIGH SCHOOL ZOOLOGY.

n

these kinds may be closely incorporated with those of the first
category.

17. An inspection of the cranium from the upper surface
(Fig. 6) discloses in the middle line two slits (the anterior and

pm
a

Fig. 6. — Cranium and Anterior Vertebras of Catfish from above.
M. mesethmoid ; pm. premaxilla ; a. antorbital ; n. nasal ; e. parethmoid ; fr.
frontal ; s. sphenotic ; p. pterotic ; ep. epiotic ; t. supraclavicle ; so. supraoccipital
spine ; 4. transverse process of fourth vertebra.

posterior fontanelles) which separate the two frontal bones
except for a short intervening bridge, where these bones (which
form a considerable part of the cranial roof) articulate by a
serrated suture. In front of the anterior fontanelle is the
mesethmoid bone; behind the posterior, the supra-occipital^

22

HIGH SCHOOL ZOOLOGY.

the former terminating anteriorly in a notch, the latter posteri-
orly in a bifid spine. Four projections mark each lateral border
of the skull, belonging to the mesethmoid, the parethmoid, the
sphenotic and the pterotic bones, while the hinder border pre-
sents a projection from the epiotic on either side of the supra-
occipital spine. Thus twelve bones enter into the formation of
the cranial box, for all of the above-mentioned bones are in
pairs with the exception of the mesethmoid and supra-occipital.

18. On the floor of the skull (Fig. 7) the mesethmoid still forms

Fig. 7. — Cranium and Anterior Vertebrae of Catfish, from below.
Pm, premaxila ; m, mesethmoid; v, vomer; pa, parethmoid; o, orbitosphenoid; f,
frontal; ps, parasphenoid; a, alisphenoid; pr, prootic; h, articular surface for hyoman-
dibular on sphen- and pterotics ; b, basioccipital with exoccipitals on either side ;
s, supraclavicle ; in, "malleus;" 4, 5 and 6, transverse processes of 4th, 5th and 6th
vertebrae.

HIGH SCHOOL ZOOOLGY. 23

the anterior boundary, while the posterior is occupied by another
unpaired bone, the basi-occipital. The latter articulates with
the centrum of the first vertebra, and also ** fiords support to a
bone of the shoulder-girdle (the supraclavicle or post-temporal)
which abuts against the strong transverse process of the fourth
vertebra and rests by two other prongs on the epi- and pterotic
projections. Between the mesethmoid and the basioccipital
the following bones are to be noticed ; the vomer, a T-shaped
bone, the transverse bar of which lies across the ventral surface
of the parethmoids, and the parasphenoid which continues back
the leg of the vomer in the middle line. All of the lateral projec-
tions seen from above are also to be seen from below. Certain
foramina furnish landmarks for the recognition of the other
bones to be seen on this surface : on either side of the basi-
occipital are the exoccipitals each with two foramina for the
escape of the 9th and 10th nerves. The sutures between the
basi- and exoccipitals, and the epi- and pterotics are occupied by
cartilage and are thus very distinct, and the pro-otics (which
are wedged in between the exoccipitals and the pterotics) are
similarly marked out. In front of the pro-otics are the large
apertures by which the 5th and 7th cranial nerves escape, but
these apertures are also partly bounded by the sphenotic above,
the alisphenoid in front and the basisphenoid (an unpaired
bone partly concealed by the parasphenoid) towards the middle
line. Between the alisphenoids and the orbitosphenoid, are
the optic foramina for the escape of the optic nerves ; the latter
bone is unpaired, and it forms a considerable part of the side
walls of the skull and also of its floor, where, however, it is
covered by the parasphenoid : it is also channelled by the
olfactory tracts on their way to the nasal sacs. Thus eleven
additional bones are to be seen from this aspect, of which five
are unpaired; viz., the basioccipital, the basi-, orbito-, and oara-
sphenoids, and the vomer.

24

HIGH SCHOOL ZOOLOGY.

19. The shape of the cranial cavity will be better under-
stood after a description of the brain and ear, but the cavity
is narrower and shallower in front where the olfactory tracts
are alone to be accommodated, and wider and deeper behind
where the brain and ear are situated.

20. Reference was made above to some scale-like bones in
connection with the sensory canals. Several of these form an
infraorbital chain below the eye ; two of them, the antorbital
and nasal, are in the roof of each nasal sac, while others have
been incorporated with the underlying frontals, parethmoids,
etc. ; for these and several other bones of the roof shelter
sensory canals.

21. The Jaws and Visceral Skeleton.— Immediately

below the lateral edge of the sphenotic is a groove lined with
cartilage, which extends on to the pterotic, and is the articular
surface for the hyomandibular, an important bone suspending
the jaws and the visceral skeleton to the skull. (Fig. 8). Inti-

Fig. 8.— Jaws and Hyoid Arch of Catfish, from the side.
Mx, maxilla; pmx, premaxilla ; pi. palatine; hmd, hyomandibular; op, oper-
culum ; mpt, metapterygoid ; qu, quadrate ; pr, preoperculum ; sop, interoperculum ;
d, dentary ; ar, articular ; h, hypohyal ; gh, glossohyal ; ch, ceratohyal ; eh, epihyal :
br, branchiofitegal rays.

HIGH SCHOOL ZOOLOGY. 25

mately united to it by an intervening symplectic cartilage
is the quadrate, a bone which furnishes the articular surface
for the lower jaw or mandible. Wedged in between the hyo-
mandibular and quadrate is a flat bone, the metapterygoid,
to the anterior end of which (by means of an intermediate
scale-like bone,) the palatine is related, a rod-like bone articu-
lated to the parethmoid and anteriorly carrying the maxilla.
In most fishes this bone forms part of the gape ; here it acts
merely as a support for the large maxillary barbels, while the
premaxillae attached to the ventral surface of the horns of the
mesethmoid, and connected with each other in the middle line,
bear most of the teeth of the upper jaw.

22. The mandibles also bear teeth on their so-called dentary
part, while near the " angle " of the jaw is the articular part ;
on the inner surface of both the remains of the cartilage
(Meckel's) on which this jaw is built are to be seen.

23. Closely united to the hinder border of the hyomandibular
and quadrate is the preoperculum through which a sensory
canal runs to reach the lower jaw. Behind it is the moveable
operculum, the chief bone of the gill-cover, which however
articulates separately with the hyomandibular. Between the
operculum and the mandible, and united with both, is the third
bone of the gill-cover, the interoperculum. In most fishes, but
not here, there is a fourth bone, the suboperculum.

24. By means of a short interhyal piece of cartilage the
hyoid arch is connected with the lower end of the hyoman-
dibular ; it is itself divided on each side into three pieces, the
epi-, cerato-, and hypohyals, which are united in the ventral
middle line by an unpaired bone, the basihyal or glossohyal,
which gives attachment to the retractor muscles of the arch.
Articulated to the pos'erior border of the cerato- and epihyals
are eight branchiostegal rays, the uppermost of which occupies
much the same position as the suboperculum of other fishes.

26

HIGH SCHOOL ZOOLOGY.

25. Very similar in construction to the hyoid arch are the
succeeding five branchial arches, the upper ends of which curve
in beneath the skull, to the base of which they are attached by
muscle and ligaments, while the lower ends meet in the floor of
the mouth. Epi- and cerato- branchials form the greater part
of each arch, but the upper ends are formed of pharyngo-
branchials, and the lower of hypo-branchials, united by certain
unpaired pieces, the basi-branchials. (Fig. 9).

Fig. 9.— Visceral Skeleton of Catfish.
H.hypohyal; oh, oeratohyal; eh, epihyal; i, interhyal; b1, first basibranchial ;
hbl, cb1, eb1, hypo- cerato- and epibranchials of first arch ; o, oesophagus; ep and hp,
epi- and hypopharyngeal tooth plates.

26. The teeth on the premaxillae and mandible have been
referred to above, but the catfish has also a formidable array of
teeth further back in the cavity of the mouth. The four plates
which carry these are known as the superior and inferior
pharyngeal plates, the former of which are attached below the
upper ends of the third and fourth arches, while the latter are
co-ossified with the ceratobranchials (the only parts present) of
the fifth arch.

27. Appendicular Skeleton.— The pectoral fin is sup-
ported by a bony arch known as the pectoral arch or girdle,

HIGH SCHOOL ZOOLOGY.

27

(Fig. 10) which in its turn finds a firm basis of resistance in the
skull and vertebral column by means of the supraclavicle or
post-temporal described above. This bone is firmly wedged into
a socket in the clavicle proper which lies very close to the skin,
(especially immediately above the fin where a rough process
projecting backwards from it may be felt), and is regarded as a
skin-bone, formed on the substructure of the primary arch
which it conceals and with which it is closely united. The

aepfiSSej^^

Fig. 10.— Pectoral Girdle of Catfish from behind.
Co, coracoidal, s, scapular portion of primary shoulder-girdle ; cl, clavicular,
sc, supra-clavicular portions of secondary shoulder-girdle ; b, basal elements, r, rays of
the fin -skeleton.

latter is at first cartilaginous, the former never so. Both the
clavicle and the primary shoulder-girdle are divided into upper
and lower parts by the fin, the lower parts uniting in the
ventral middle line and thus completing the arch. The upper
part of the primary arch is known as the scapula, the lower
as the coracoid, and the region where the fin unites with it the
glenoid region.

2 . Let us now examine the skeleton of the fin itself. It is
made up of fin-rays of which the anterior is bony throughout,
and toothed on its posterior margin ; it is a hard i*ay or

28 HIGH SCHOOL ZOOLOGY.

spine, in contradistinction to the other six rays which are
jointed and fringed and are therefore known as soft or branched
rays. The spine alone is jointed directly to the shoulder-girdle,
while the other rays are fixed to it by intermediate pieces of
which the hindmost (metapterygial basale) is the largest ; the
spine in fact is a ray, plus the foremost intermediate piece,
(mesopterygial basale) and their union is to be explained by the
use of this ray as a weapon, which may be firmly set (by means
of a peculiar joint) and used for offence or defence.

29. The structure of the ventral fin is similar to that of the
pectoral. It has eight rays, of which one is hard. There is no
pelvic arch, what is generally termed so, being the metaptery-
gial basalia of both fins, united in the middle line.

30. Considerable resemblance to the above will be seen in
the fin-rays of the unpaired fins. They are for the most part
soft, but some are hard, and they articulate with the interspi-
nals, which again fit into the cleft neural and haemal spines
of certain of the vertebrae (§ 13). Of these rays the defensive
spine of the dorsal fin deserves mention, as, from the peculiar
arrangement of the interspinals with which it is connected, it
may be " set " like the pectoral spine.

For the purpose of distinguishing different species of fish it is often
desirable to count the number of rays and express them in a formula,
(Roman numerals being employed for the hard, Arabic for the soft rays),
e. g. for this species : —

ID. I, 6 A. 22

\P. I, 6 V. I, 7

31. Muscular System. — The muscles of an animal are
what we ordinarily call its flesh ; their function is to contract
on a stimulus received from the nervous system, and thus to
bring nearer together the parts of the skeleton to which they
are attached, or to narrow the tubes round which they are dis-
posed. Those surrounding the blood-vessels and intestinal
canal form the bulk of what is called the involuntary muscu-

HIGH SCHOOL ZOOLOGY. 29

lature of the body. They reply slowly to a stimulus, and are
not under the influence of the will, while those which unite the
various parts of the skeleton are called voluntary, because they
are controllable by the will, and reply rapidly to a stimulus.

Both kinds of muscles are formed of fibres, which contract on the
receipt of a stimulus through motor nerve-fibres which terminate in
them. The involuntary are formed of bands of simple muscle-cells—
the voluntary of bundles of striated fibres, but in both the muscle-tissue
has a framework of connective-tissue which suspends the vessels and
nerves distributed to the muscle-tissue.

32. The voluntary muscles are a7so called " skeletal," for it is
obvious that a very important relationship must exist between
the skeleton and the muscles. Where muscles are of large size,
they must have a sufficient surface for their origin and in-
sertion, and where they cause two parts of the skeleton to
move upon each other, the nature and extent of the movements
must determine the character of the joint. Thus those parts of
the body where the most complicated movements are carried
out will have the more differentiated muscles, and those where
the movements are simpler, will have the less specialised
muscles. In the catfish the more specialised muscles are those
which work the jaws, the parts of the visceral skeleton, the
gill-cover, and the spines of the pectoral and dorsal fins, while
the less specialised are those which form the fl shy mass of the
trunk and tail. The latter exhibit the same metamery which
we have seen to characterize this region of the skeleton, for the
muscles are divided into myomeres, separated by membranous
partitions which are attached to the ribs and vertebrae, but
the planes of these partitions are not vertical ones, as we
may see from a cut through the tail, or from the curved form
of the myomeres or fla\es into which the flesh of the fish sep-
arates when boiled. Special muscular slips extend into the fins,
and serve to depress or erect the rays, but these fin-muscles do
not attain the size which the limb-muscles have in higher Yer-

30 HIGH SCHOOL ZOOLOGY.

tebrates, where the limbs are of greater importance in connec-
tion with the support of the body and with locomotion.

33. NerVOUS System. — Here we recognize two constitu-
ent parts ; the central nervous system, and the nerves which
course from it to their endings in the various organs of the
body, and which indeed are developed as outgrowths from it.
The nerves either carry impulses from the central nervous
system to the muscles, glands &c, or they transmit impulses to
it from the various sense-organs ; they are thus either efferent
or afferent in function. Tiiey originate from both parts of the
nervous system — the brain and spinal cord, and are distinguished
therefore as cranial and spinal nerves.

34. In our study of the skeleton we have seen that the brain
and spinal cord are protected in bony canals, perforated for
the escape of the nerves. The canals are not entirely filled
up by these organs, for certain membranes are present which
assist in the protection and nutrition of them. The cranial
cavity for example is much larger than necessary to hold the
brain, and the interspace is filled up with fatty matter which
it is necessary to remove before the brain is exposed. When
this is done, it is seen to have the form represented in Fig. 11
composed of alternately dilated and constricted parts. In front
are the olfactory bulbs close against the nasal sacs, connecting
these with the rest of the b: am are the olfactory tracts, and
then come in order the cerebral hemispheres, the epiphysis
projecting from the concealed thalamic region, the optic lobes,
the cerebellum partly covering these and the medulla oblon-
gata, with two pairs of secondary swellings upon it. From
the under surface will be seen the cerebral hemispheres, with
the optic nerves crossing behind them after their descent from
the optic lobes, the thalamic region in the form of the hypo-
physis and inferior lobes, and the medulla oblongata with the
other cranial nerves springing from it.

HIGH SCHOOL ZOOLOGY.

31

i viii

A.

35. Transections of the
brain show that it is a
tube, the walls of which
are thick in some parts
and thin in others, and
the cavity of which is
dilated into ventricles,
communicating with
each other. The roof of
the cerebral region is so
thin that the functions
that are discharged by it
in the higher animals,
must have their seat else-
where in the fish. A
similar condition is ob-
served in the thalamic
region, and that of the
medulla oblongata, (ex-
cept anteriorly where
the cerebellum is extra-
ordinarily developed), so that it is chiefly the floor of the cavity
which is thickened in these parts. On the other hand it is the
roof which is thickened to form the optic lobes and the cere-
bellum.

36. The various regions of the brain or encephalon have received the
above names as they appear to be comparable to similiarly named
regions in higher forms ; but the regions and ventricles are also named, by
comparative anatomists, rhin-,pros-,thalam-,mes-,ep- ami met- encephalon
and the ventricles rhinocoele, prosoccele, thalamocoele, mesoccele, epicoeJe,
metaccele. Of these ventricles the thalamocoele is the most complicated
as it projects above into the epiphysis, and below into the inferior
lobes and hypophysis. The hypophysis and epiphysis are not formed of
nervous matter like the rest of the brain, for the former is glandular
in its nature, while the latter is supposed to be the rudiment of an un-
paired eye.

Fig. 11.— Brain of Catfish.
A— From above. B — From below.
Rh, olfactory lobes ; Ot, olfactory tracts ;

cerebral hemispheres ; Mes, optic lobes ; Cb, cere-
bellum ; Met.-medulla oblongata ; a and c, trigem-
inal and vagal lobes of medulla; b, inferior lobes of
thalamic region ; II-X, cranial nerves ; Sp1, first
spinal nerves.

32

HIGH SCHOOIi ZOOLOGY

87. like the brain, the spinal cord is also a tube, its cavity,
the central canal, being, however, more uniform, and its walls
of similar thickness throughout, except that the side walls are
more developed than either the roof or the floor (Fig. 12). The
metamery of the nervous system is much better seen here than in
the brain, for at regular intervals corresponding to the vertebrae,

a pair of spinal nerves is at-
tached to the cord. Each
nerve originates by two
roots, which from their
places of origin are known
as dorsal and ventral ; the
dorsal roots have a knot or
, ganglion upon them, and
they contain only efferent
fibres, the ventral on the
other hand are formed of
afferent fibres : both kinds
n$ of fibres are, however, soon
associated in the mixed
nerves of the body.

38. Of the two elements of

nerve tissue distinguished in

Fig. 12 —Section through Spinal Cord and D 00 ,, n i u j

surrounding parts, in young Catfish. X40. § 33» the nerve cells, also called

No, notochord, with its sheath ; n, the neural ganglion cells, are most abund-

arch; d, dorsal, v, ventral nerve-root; g. gan- „ . _ n ,-i ... m » ,•■

ghon of dorsal root; d*, v\ dorsal and ventral ant round the cavities of the

mixed nerves; s, sympathetic ganglion; ao, brain and spinal cord, but are

also found in smaller centres
or ganglia, while the fibres are found both in the nerves and in the
centres. The function of the fibres is to transmit impulses, and this is
effected by the axis cylinder, while the function of the cells is to store
up or modify the impulses that arrive through the afferent nerves, and
to originate those which are discharged through the efferent nerves.

39. It is easy to understand the way in which the spinal
nerves are distributed in the body. Each pair supplies chiefly

HIGH SCHOOL ZOOLOGY. 33

the parts of its own metamere, although for purpose of coordi-
nation, as e. g., in the various movements of the pectoral fin,
the nerves of contiguous metameres communicate with each
other in plexuses. The parts above the level of the spinal
canal are supplied by the dorsal division of the spinal nerves,
those below by the ventral divisions, and finally the contents
of the coelom are supplied by special intestinal branches which
are provided with ganglia, communicate intimately with each
other before supplying the viscera, and constitute the Sympa-
thetic system. The arrangement of the cranial nerves is
however much more complicated, first, because their metamery
is not so evident, and second, because the nerves as they emerge
separately from the brain, are not each composed of a dorsal
and ventral root, but some seem only to be ventral, others to
be composed of several dorsal and ventral roots. Two of them,
the 1st and 2nd pairs, olfactory and optic, go to the nose and
eyes respectively, the 3rd, 4th and 6th, are motor nerves which
control the muscles of the eyeball, the 5th and 7th supply the
greater part of the head with sensory and motor nerves, the
8th is distributed only to the internal ear, while the 9th chiefly
ends in the 1st gill arch, and the 10th is distributed to the re-
maining gills, but does not confine itself to the head, and sends
branches to the heart, air-bladder and stomach. A separate
branch of this widely-distributed (Vagus) nerve supplies the
sense-organs of the lateral line. The fifth nerve is also not con-
fined to the head, but communicates wi h the dorsal branches
of the spinal nerves by a long branch which pierces the back
of the skull on either side of the supra-occipital spine.

40. We must now turn our attention to the endings of these
nerves, especially to those of the afferent nerves, which trans-
mit impulses to the brain and spinal cord from the sense-organs.
Certain of the latter have been already referred to (§ 9), there
remain for discussion the higher sense organs, or the nose,, eye
and ear.

34

HIGH SCHOOL ZOOLOGYo

41. Olfactory Organ. — When the roof of the nasal sac
is removed (§ 4), the floor will be seen to be formed of a reddish
mucous membrane, presenting a median groove and a series of
transverse ridges running towards it. A current is established
from one nostril to the other, and the odoriferous particles con-
tained, are detected by special olfactory cells, which are situated
between the ridges, and are directly connected with the olfac-
tory nerve-fibres. In some fishes the ridges are arranged in
such a way as to suggest to anatomists that the nasal sacs are
altered gills, which have been confined to this sensitive func-
tions, but the examination of the catfish alone would not
suggest this view.

42. The Eye. — In higher Yertebrates the eye affects the
shape of the skull considerably more than it does in the catfish,
for there is no orbit in the latter, and the eye is simply situated
in some fatty tissue between the overhanging frontal bone, and
the great muscle of the jaw. It is small in size and unprotected
by lids, the skin being thin and transparent where it passes over

the surface of the bulb, and
sufficiently loose to allow
the latter some independent
movement. This is effected
by six muscles, four of
which, the straight muscles
or Recti, are grouped above,
below and on either side of
the optic nerve, as it courses
from the optic foramen to
the bulb, and two others, the
oblique muscles, cross trans-
versely to the eye from the
skull. All the muscles are at-

Fig. 13. —Vertical Section of Eye of Catfish. X 30
S, skin; co, cornea; sc, sclerotic; ch, choroid; tached near the equator of

tSr^%ittoaSumoreol,tionerve;',lri8; thebulbtothescleroticcoat.

HIGH SCHOOL ZOOLOGY.

35

43. The examination of the bulb itself (Fig. 13) discloses three
coats, the outermost of which is subdivided into an anterior trans-
parent part the cornea, and a posterior hard fibrous and opaque
part the sclerotic. Within this is the second coat, the choroid,
which chiefly serves to distribute the blood within the bulb,
and to form a dark background for the retina, but anteriorly
forms a muscular screen — the iris, perforated by the pupil,
through which the amount of light admitted to the sensitive
part of the eye may be regulated by the iris. Suspended from
the junction of the choroid and iris by a special ciliary muscle,
is the leas a globular transparent body which changes the

course of the rays of light
admitted to the eye, and
casts an inverted image on
the retina or nervous coat,
which lines the whole of the
choroid coat, and is separat-
ed from the lens by the fluid
and transparent vitreous
humor. The optic nerve
which terminates in the re-
tina, must therefore pierce
both the sclerotic and chor-
oid coats to do so, and in-
deed it perforates the re-
tina also, for its fibres form
the innermost of the several
layers of which the retina
is composed.

44. Study of the develop-
ment of the eye shows that the
retina is really an outgrowth of
the brain, which like the brain
has a cavity, one wall of which

Fig1. 14.— Diagrammatic Section of Retina of
young Catfish. X400.

1 , layer of optic nerve fibres ; 2, of ganglion
cells ; 3, internal molecular, 4, internal granu-
lar or ganglionic layer (containing nuclei of Miil-
ler's fibres) ; 5, external molecular, 6, external
granular layer, containing nuclei of the rod sand
cones, 8. but separated from them by the ex-
ternal limiting membrane, 7 ; 9, pigmentary
retinal epithelium.

36 HIGH SCHOOL ZOOLOGY.

is formed by the single layer of tall columnar cells — the pigmentary
epithelium of the retina, while the other, the retina proper, is formed of
several layers, of which that toward the cavity is the layer of the rods
and cones, while that towards the vitreous humor is the layer of optic
nerve fibres. Between the two are various layers of nerve-cells, sup-
ported by other elements which are not nervous in their nature.
(Fig. 14). The rods and cones are the neuro-epithelial cells of the re-
tina, and the original space between them and the pigmentary epithe-
ium is obliterated by the close contact of the two layers. The lens on
the other hand is shown to be developed from the epidermis, and the
fibres of which it is composed are really altered epidermal cells.

45. The Ear. — In man the ear consists of three parts, the
external ear, the middle ear or drum-cavity, and the internal ear
or labyrinth : only the latter exists in the catfish. The two
former in man are concerned with the concentration of sound-
waves on the latter ; how then in the absence of these, do
sound-waves reach the labyrinth in the catfish ? In some fishes
a rudimentary gill-cleft between the hyoid arch and the jaws,
appears to be the channel through which the vibrations reach
the internal ear, but no such gill-cleft exists in the catfish, so it
is probable that they are transmitted through the bones of the
head, and above all through the comparatively loose ones,
which are suspended to the ear capsule, by the hyomandibular
(§ 21). Another possible channel will be referred to after-
wards. In all animals the labyrinth is the essential part of the
organ of hearing, as it is in it, that the auditory nerve termin-
ates. In most forms the labyrinth is enclosed in a complete
cartilaginous or bony capsule, (forming in the latter case the
iprootic, epiotic bones, &c.,) and only perforated by small aper-
tures towards the outside and towards the cavity of the skull,
but in the group of fishes to which the catfish belongs, the side
of the capsule towards the brain is very deficient, and conse-
quently the greater part of the labyrinth can be seen by opening
the cranial cavity.

HIGH SCHOOL ZOOLOGY.

37

Fig. 15.— Right Ear of Catfish, from within. X*.

Asc, hsc, psc, anterior, horizontal and posterior semi-circular canals ; aa, ha, pa,
their ampullae ; ut, utriculus ; ru, recessus utriculi ; VIII, anterior and posterior
branches of auditory nerve ; co, lagena cochleae ; s, sacculus ; tr, opening of transverse
duct communicating with the left ear.

46. Of the two parts into which the labyrinth is divided,
(s'ig. 5) the lower is largely concealed by a little shelf project-
ing from each ex-occipital bone, and meeting in the middle line
over the basi-occipital. This part is known as the saccule and
lagena cochleae, each of which is a delicate membranous sac, con-
taining fluid (th-^ endolymph) and an ear-stone or otolith and
receiving a considerable part of the auditory nerve, the fibres of
which terminate in certain cells of the lining membrane. The
upper part is more easily seen ; it is connected with the lower
by a narrow duct, and is formed of a central tube, the
utriculus, with a large membranous sac projecting forwards
from it, and containing a very large otolith and corresponding
branch of the auditory nerve. Into the utriculus and its
recess there open the thre? semi-circular canals, anterior
posterior and external, which are respectively situated approx-
imately in sagittal, frontal and horizontal planes. Their lower

38 high school zoology.

openings into the utriculus are dilated into ampullae each of
which receives a twig of the auditory nerve.

47. Reference was made to the communication between the
air-bladder and the ear of the catfish ; this is brought about in
the following way. Near the narrow tube between the
upper and lower parts of the labyrinth, there is a cross duct
connecting both, and projecting backward into a little pear-
shaped sac, which lies in a groove on the upper surface of the
basi-occipital bone. The whole labyrinth, and especially this
part of it float comparatively freely in the fluid contents of the
cranial cavity (perilymph); if currents should be caused
in this perilymph it is obvious that currents would also be es-
tablished in the endolymph, and thus excite or disturb the
terminal cells of the auditory nerve-fibres which project into it.
Such an arrangement for causing currents in the perilymph
exists ; it consists in the fact that each half of the neural arch
of the first vertebra, can be pressed closer into the neural
canal or pulled out by means of a lever (m, Fig. 7), the hinder
end of which is attached to the front end of the air-bladder ;
consequently any changes of pressure in the air bladder are
transmitted through this lever to the perilymph, and so to the
auditory nerve. Whether sound-waves can affect the density
of the air in the air-bladder (there is a spot behind the shoulder-
blade where it comes immediately underneath the skin) or
whether some other function is performed by this singular ap-
paratus, cannot be decided with the knowledge at our disposal.

48. Considerable resemblance will be detected in the microscopical
structure of the ends of the nerves of special sense. The labyrinth is
lined with epithelial cells which here and there present a different
character (neuro-epithelium) where the auditory nerve terminates within
them. Two kinds of cells are to be seen, the supporting cells and the
hair-cells, the latter alone being connected with the nerves. In the
ampullae the hairs of the hair-cells are very long and delicate, in the
other sensitive spots, short and stouter, for they carry on their
tips the otoliths referred to above. The ampullae are supposed to be

HIGH SCHOOL ZOOLOGY.

39

concerned in the sense of equilibrium and direction, for which purpose
the arrangement in space of the semi- circular canals would appear to lit
them.

49. The Intestinal System. — To this belongs the Ali-
mentary canal, with its appendages, the liver, air-bladder, <fec;
the gills, which also come under this category, we shall, how-
ever, reserve for separate treatment.

We have already studied the osseous boundaries of the gape,
and seen the distribution of teeth on these. There are no soft
flexible lips, although the skin in this position is more richly
provided with the tactile organs described in § 9 than elsewhere.
In other respects except in the distribution of pigment and
thickness, there is little difference between the mucous mem-
brane which lines the mouth-cavity and the external skin.
There can hardly be said to be a tongue in the same sense as in
the higher vertebrates, but the mucous membrane which clothes
the hypo-hyal bones is certainly thicker than it is elsewhere in
the mouth. In the living fish the action of the superior and
inferior pharyngeal tooth-plates can be seen ; the presence of
any foreign body causes them to close reflexly on it, and the
muscles in connection with them enable them to pass it down
into the oesophagus. This is the begining of the alimentary
tract proper, in which we recognize three chief divisions, the
oesophagus and stomach, the small intestine, and the large in-
testine. The latter terminates in the anus, in front of the anal
fin, and is separated from the small intestine by an ileo-coecal
valve, while the small intestine is separated from the stomach
by the pyloric valve. The limits of the various regions are
therefore distinct, but there is no such limit between the oeso-
phagus and the stomach, although considerable structural dif-
ferences exist between these two organs.

50. The whole intestinal tract is constructed on the same gene-
ral plan throughout j where it lies free in the ccelom, it is cov-
ered by a serous coat which is continous with the ccelomic

40

HIGH SCHOOL ZOOLOGY.

or peritoneal lining by means of a double fold thereof, known
as the mesentery. If, as in most animals the intestinal canal
be longer than the coelom, it is evident that the mesentery must
be longer along the line of its intestinal attachment than along
that where it is continuous with the coelomic lining. If then
the intestine be thrown into coils, so as to be accommodated with-
in the ccelom, the mesentery must likewise be complicated in its
form. Between the two folds of the mesentery the blood-vessels
and nerves which pass to and from the intestine are accom-
modated. Immediately within the serous coat of the intestine
is the muscular coat, in which two layers are recognized, an
outer of longitudinal, and an inner of circular fibres. These
fibres are of the involuntary order, except in the oesophagus
where the inner circular coat is wanting and the longitudinal
fibres are surrounded by voluntary or striped fibres. Within
the muscular coat we find more or less submucous tissue,

answering to the subcutaneous tissue
of the skin, and finally the mucous
coat which forms the lining of the
intestine, and in which, as in the
skin, we recognize two layers, a con-
nective-tissue and an epithelial. The
latter is the characteristic tissue of
the intestine, and forms the bulk of
those glands which contribute the
various digestive juices. (Fig. 16).

51. Although there is no marked
boundary between the stomach and
oesophagus,' the former is decidedly
wider, and much more abundantly
supplied with blood. This is neces-
sary for the proper discharge of the

Fig. 16.— Longitudinal Section of
Intestinal Wall of Catfish.

Ep, epithelium ; m, mucosa ; j. • i j a -U

cm, circular, lm, longitudinal mus- function of the gastric glands, tubes
cles.

HIGH SCHOOL ZOOLOGY. 41

lined by a continuation of the lining epithelium of the stomach,
which dip down into the submucous coat, and consequently
make the gastric mucous membrane of considerable thickness.
The stomach forms a blind projection beyond the pyloric aper-
ture ; it is therefore said to be of the ccecal type, whereas in
many other fishes its long axis is directly continued into the
intestine. After the food has been subjected to the action of
the gastric juice, which renders some of its ingredients more
capable of being absorbed, it passes through tbe pyloric valve
(which is simply a local thickening of the circular muscular
layer) into the small intestine. Here it is at once mingled with
the secretion of two important glands, the liver and pancreas
to be afterwards described, further altered thereby, and finally
for the most part absorbed by the walls of the tube and partly
propelled further into the large intestine.

52. In most higher animals there are folds or projections of
the mucous membrane which facilitate this absorption by the
small intestine ; except for longitudinal folds, the mucous mem-
brane in the catfish is smooth, and the amount of epithelial sur-
face is increased by tubes projecting into the submucous tissue
which are however shorter and wider than the gastric tubes.
The chief difference in the structure of the large intestine is in
its greater size, and more developed musculature.

53. Of the glandular appendages of the small intestine, the
liver is the most important. It is formed for the most part of
hepatic cells which are continuous with the lining epithelial
cells of the intestine through the bile-duct. The cells are sus-
pended in a delicate frame- work of connective tissue, penetrated
by blood-vessels, and the liver is therefore very soft in its texture.
It has two lobes, a right and a left, each divided into subsidiary
lobes, and on the under surface of the right of these is the gall-
bladder, a reservoir communicating by several ducts with the
liver, but only by one with the intestine. Side by side with the

4

42 HIGH SCHOOL ZOOLOGY.

last-mentioned duct, is the duct of the pancreas, a gland of
different structure and function, which is independent of the
liver in higher animals, but in many fishes, is either wholly
or partly concealed within it, entering the frame work of the
liver beside the portal vein, the chief blood vessel of that organ,
through which, as we shall hereafter see, a considerable amount
of the blood of the body passes on its way to the heart.

54. The liver like the intestine, is within the peritoneum and
covered with a serous coat like the intestine, but the air-bladder
which we have now to examine is only covered by the pe-
ritoneum on its ventral surface. It is therefore an extra-
peritoneal structure ; it communicates with the hinder end
of the oesophagus by a narrow tortuous duct which lies between
the folds of the mesentery, and enters the air-bladder a little
in front of its middle. As the air bladder is a recess or diverti-
culum of the intestine, we should expect to find a similar arrange-
ment of its coats. As a fact however, the muscular coat is
merely represented by a stout white opaque layer, in which only
connective and no muscular tissue is present, while this sepa-
rates with great readiness from the inner mucous coat on
account of the scantiness of the submucous tissue. When the
air-bladder is first exposed it appears to be undivided, but when
the outer coat is removed there is seen to be a partition sub-
dividing the hinder part into two cavities, and narrowing the
apertures by which these communicate with the single anterior
cavity. The inner coat can readily be removed without ruptur-
ing it, and then the three communicating compartments are
readily seen : it is at the junction of these that the duct
enters. As for the structure of the mucous coat, it is
very unlike that of the intestine, for its connective-tissue layer
is very delicate, very poorly supplied with blood-vessels, and its
epithelial layer, is formed of thin pavement-like hexagonal
cells. Only the outer coat is connected with the altered verte-
brae and their processes as described in § 47.

HIGH SCHOOL ZOOLOGY.

43

55. As we shall see hereafter, the air-bladder in some fishes
is so well supplied with blood, and communicates so freely with
the oesophagus that it can act as a breathing organ. Such is
obviously not its function in the catfish. Again there are fishes
which live in deep water, and can by altering the amount of
air in the air-bladder, accommodate their specific gravity to that
of the water at any particular level. But such an hydrostatic
arrangement must be of less service to a catlish than to many
other groups. The connection with the ear renders it likely
that the functions discharged by the air bladder are of a complex
character, but they are not yet well understood.

56. Respiratory System.— We have

already studied the skeleton of the gill-
arches ; there remain to be examined the
soft parts which clothe these. Within the
cavity of the mouth there may be observed
certain tubercles which fit into each other
when the gill clefts are closed, these are
the gill- rakers ; they are sometimes of con-
siderable size in other fishes, and may act
as strainers of the water which flows out
through the clefts, over the gills. On the
convex side are the gill-filaments, disposed
in two rows. (Fig. 17).

51. The vessels which supply the gill-
filaments ascend the arches in a groove,
which is easily seen on their convex side in
the dry condition. Of the four arches, the
arte'ry^aa^^fe'rent artery ; last is decidedly the shortest, and the same
n' nerve- is true of the slit behind it. All the slits

open freely into the branchial cavity, and this by a very wide
aperture to the outside, the apertures of the right and left sides
being only separated from each other below by a narrow isth-

17— Diagrammatic Sec-
tion of Gill-arch.

44 HIGH SCHOOL ZOOLOGY.

mus. In some fishes by the union of the gill-cover to the skin
over the pectoral arch, this aperture may be much reduced in
size.

58. In the roof of the branchial cavity in front of the pectoral girdle,
an organ, the tliymus, is present in the fishes which attains a considerable
size in some forms, and is difficult to make out in others. It is seen in the
young catfish, but not in the adult. Again, below the floor of the mouth-
cavity, round the origin of the vessels which ascend the gill-arches, is
another organ, the thyroid, which is of some size in the adult. The
functions of both of these structures are obscure, but the organs are
found in similar positions in all Vertebrates.

59. Vascular System. — In all Vertebrates two subdivi-
sions are present, the blood- and the lymph-vascular system.
The former embraces the heart and blood-vessels and their
contents, the latter the lymph-vessels and spaces and the
lymph-glands in which certain elements of the lymph are formed.

60. Both, the circulating fluids contain corpuscles, which in
the blood are of two kinds, coloured and colourless, while in the
lymph only the colourless corpuscles are present (Fig. 3, a). The
coloured corpuscles while passing through the fine vessels of the
gills, have a remarkable power of combining with the oxygen
contained in the water which bathes the gills, but they just as
easily give up this oxygen to the other tissues which require it.
This power they owe to the haemoglobin, which they con-
tain, and which also is the cause of their colour. The amoe-
boid colourless corpuscles have, on the other hand, a faculty
which the coloured ones do not possess to any extent, that of
changing their shape and incorporating foreign particles.

61. The centre of the blood- vascular system is the heart;
from it in front are given off the arteries, through which the
blood is distributed by way of the gills to the body generally,
and towards it behind, the veins converge, through which the
blood is returned to the heart to be again sent on its course.
Between the arteries and the veins are the finer capillary

HIGH SCHOOL ZOOLOGY.

45

vessels, the walls of which are so thin that
the blood while flowing through them is
enabled to effect exchanges with the sur-
rounding medium. Thus in the gill-capil-
laries it readily gives up the carbonic acid,
which it has accumulated in the tissues,
and combines anew with the oxygen in the
water, and, while flowing through the
capillaries of the rest of the body, gives up
to the tissues the food they require, and
receives from them the accumulated refuse
which has to be removed through the inter-
vention of the glandular cells of the liver
and kidney, with which the hepatic and
renal capillaries enter into intimate con-
nection. (Fig. 18).

In the catfish the heart is situated be-
tween the floor of the hinder part of the
mouth-cavity, and the ventral part of the
pectoral girdle. A strong partition
stretches from the hinder border of the
girdle up towards the back bone, and
bounds the coelom anteriorly ; it is per-
forated by the oesophagus and several
veins. In front of this partition is the pericardial sac, which
contains the heart, and between the partition and the pericard-
ium is the venous sinus, to which the various veins converge
before they enter the heart. The venous stream is received
from the sinus into the atrium or auricle, a thin-walled
chamber, which (when the heart is inspected from below) is
largely concealed by the ventricle, a thick-walled muscular
chamber, which drives the blood through the gills to the body.
Connected with the ventricle by a narrow neck is the bulb-like
beginning of the great trunk artery, which lies below the copu-

F'\g. 18.— Diagram of the
Circulation in a Teleost.
(After Claus).
Ba, bulbus arteriosus;
Ab, branchial vessels ; V,
ventricle ; ao, aorta ; Lk,
capillaries of liver; N, kid-
ney ; D, intestine.

46 HIGH SCHOOL ZOOLOGY.

lse of the gill-arches, and gives off the vessels to these. These
various divisions of the heart are separated from each other by
pocket-like semilunar valves, which prevent the reflux of the
blood after the contractions of its cavities.

62. The blood-supply of the gills is one of the most interesting
parts about the vascular system, because, as we find that the
embryos of the air-breathing animals have gill-arches and gill-
clefts which disappear as development goes on, so we find that
gill -vessels are present also, which afterwards, however, become
much altered. These vessels, partaking of the shape of the
j arts they accompany, are called the aortic arches, and they
are uninterrupted tubes which arch on either side from the
arterial trunk below the alimentary canal, to another arterial
trunk above it, which from its position is called the dorsal
aorta. Before joining the dorsal aorta, some of the anterior
arches give off branches which supply arterial blood to the head.
A similar condition obtains in the adult fish, only instead of an
uninterrupted aortic arch, there are two vessels to every gill-
arch, one which distributes the blood to the gill-filaments, the
other which collects it from them. These are known as the
afferent and efferent branchial arteries. It is therefore the
latter which unite to form the dorsal aorta, after the foremost
one has on each side given off the carotid arteries to the
head. In its course backwards underneath the vertebral
column, the dorsal aorta gives off various branches both to the
contents of the ccelom, and to the other parts of the trunk and
tail, but the venous streams, which collect the blood from these
various parts, undergo some delay in their return to the heart.
For example, the venous blood from the tail, is in part subjected
to the action of the kidney, before it reaches the heart through
the posterior cardinal veins, (situated immediately underneath
the trunk vertebrae,) while the rest of it, with the blood col-
lected from the other contents of the ccelom, enters the liver
through the portal vein, and is there subjected to the action of

HIGH SCHOOL ZOOLOGY. 47

that gland, before it emerges through the hepatic veins. The
venous blood from the head is returned more directly through
the anterior cardinal veins, whiclj join the posterior cardinal
on each side before they enter the venous sinus.

63. The lymph presents a contrast to the blood in this
respect, that it is not contained in well-defined vessels.
There are however a series of thin-walled channels, by which
the system is put in communication with the cardinal veins.
As for the lymph-glands referred to, the most important of these
is the spleen, a deep red body of considerable size near the
stomach, while the second almost equally as large and similar
in appearance, but very different in origin, is the head-kidney,
which lies between the anterior end of the air-bladder and the
partition which walls off the pericardial cavity.

64. Excretory System. — The structure of the head-
kidney is in the embryo catfish similar to that of the
kidney proper, which occupies the posterior part of the
ccelom, but in the course of growth the excretory tubes
which it possesses are replaced by lymphatic tissue, and
consequently it has no excretory function in the adult. On
the other hand the kidney proper which is separated from the
head kidney by the entire length of the air-bladder, is a true
excretory gland, which selects by filtration and otherwise from
the blood subjected to its action, certain nitrogenous excreta,
which have to be removed from the circulation. The excretion
is carried off from each half of the kidney, by a separate ureter,
the only indication here that the kidney is a paired structure,
and that consequently the right and left organs have coalesced.
The ureters join on leaving the kidney, and dilate into an urin-
ary bladder before opening exteriorly.

65. There is little external difference between the sexes in
the catfish, but there is one notable difference in habit which
appears to be common to several allied forms. The eggs after

48

HIGH SCHOOL ZOOLOGY.

they have been laid and have begun to develop into the young
fry, are carefully guarded by the male, who keeps them together
and swims over them, returning pertinaciously even after he
has been pushed away. A tropical form, the large eggs of
which are hatched in the mouth-cavity, and a Southern species
allied to our catfish, have been observed to take the fry into the
mouth, and allow them afterwards to escape.

Fig. 19.— Diagram of several stages in Development of Catfish.
(Modified from Ryder).

1, ovarian egg ; 2, egg in which formative yoke has separated to upper pole ; 3, em-
bryo of second day; 4, section through such an embryo, showing epiblast with nervous
system above, hypoblast below, and between them the mesoblast and the notochord ;
5 embryo of sixth day.

HIGH SCHOOL ZOOLOGY. 49

Little more need be said about the habits of the catfish. It
is remarkable for its tenacity of life, is regarded as a fair food
fish, and has accordingly received some attention from pisci-
culturists who have found that it prospers also in ponds and
streams of other regions besides that in which it naturally
occurs.

66. The artifical hatching of fish-spawn with the object of stocking
depleted waters and increasing the food supply is now being carried
on very vigorously in Canada and the United States, as well as in some
European countries. In Ontario the chief hatcheries are at Newcastle
and Sandwich, whence vast numbers of the fry of White Fish, Lake
Salmon, Pickerel, etc., are distributed for replenishing the waters of
the Provinces. The eggs are hatched out in troughs supplied with con-
stantly renewed water at a certain temperature, and thus many of the
causes which, under ordinary circumstances may lead to the arrest of
the development of the eggs are obviated. Some notions as to the
gradual development of the body in a catfish may be gathered from
Fig. 19.

The egg while still within the ovary of the mother, (1) is about one-
eighth of an inch in diameter ; it has two coats, the outer of which is
penetrated by minute canals through which the necessary nutriment for
the growth of the egg passes inwards. When the egg is laid, the space
between the two coats increases in size, and the two constituents of the
yolk (the formative yolk which gives rise directly to the body of the
embryo and the food-yolk which is utilised as food by the embryo),
formerly evenly distributed, now tend to accumulate at opposite poles (2).
The formative yolk with its contained nucleus begins to segment, the
result being a disc of small cells lying upon the surface of the food-yolk.
These cells gradually extend over the whole of the egg, those at the
pole arranging themselves into the three layers of the embryo, which
already, during the second day assumes a fish-like form (3). It is from the
three embryonic layers (epiblast, mesoblast and hypoblast) that all the
organs of the body are developed (4) ; a similar arrangement of these
exists in all vertebrate animals. The embryo does not escape from the
egg membranes until the sixth day, when, although only one-third of an
inch in length (5), development has advanced to a considerable extent.
Thus the heart is seen in front of the yolk-sac, from the vessels of
which it collects the blood enriched by contact with the yolk, and pro-

50 HIGH SCHOOL ZOOLOGY.

pels it by way of the gills throughout the entire system. The sense-
organs, fins, myotomes, and heterocercal tail are all evident, and event-
ually the yolk is all absorbed and the young fish begins to feed for itself.
At the end of three months the form of the adult is attained, although
the fish is hardly an inch in length. Teleosts differ very materially as
to the length of time of hatching of the egg, and the rapidity with
which the developmental processes run, but there is always less food-
yolk than in certain other groups of fishes to be afterward referred to,
where the development is much slower.

HIGH SCHOOL ZOOLOGY. 51

CHAPTER II.

Common Forms of Canadian Fish and their Classification.

1. The common small Catfish, Bull-head or Horned pout
which we have been examining is known to zoologists as Amiu-
rus nebulosus (Le Sueur). Zoologists as well as B >tanists use the
Linnaean binomial system of nomenclature, which involves the
use of a generic and a specific name for the purpose of indicating
to what species any individual animal belongs ; of these the
generic name stands first, the specific second, and both are
followed by the name of the author who first described the kind
of animal in question under that specific name, and (if that
should be necessary) by the name of the author who first refer-
red the species to its proper genus. The necessity of appending
the author's name to a species will be realized when it is under-
stood that two different authors may have described individuals
of the same species under different names. Thus A. nebulosus
has a host of synonymes, one of the most current of which
A. catus (Linn.) Gill, is given on the assumption that Linnseus
had already named our Catfish Silurus catus.

It is very hard to find a satisfactory definition for the term
"species." In nature we find only individuals; certain groups
of individuals resemble each other so closely that we have no
hesitation in asserting that they belong to the same species,
others may vary so much in colour or in the proportionate size
of different organs or in other ways, that zoologists may hesitate
whether or no the individuals exhibiting any constantly associ-
ated variations should have a separate specific name accorded to
them or merely rank as a "variety." The absence of interme-
diate forms between two or more such groups of individuals is

52 HIGH SCHOOL ZOOLOGY.

generally considered a sufficient ground for regarding them
as distinct species. Varieties are often the result of local
conditions and are therefore spoken of as geographical varie-
ties or sub-species, but they may be also brought about artifi-
cially by man, in which case they are generally spoken of as
"races."

2. Ceitain groups of species resemble each other so much
that they are grouped by naturalists under the same "genus."
Some genera are large, embracing a number of species, others
small with only one or two; when they are large it is con-
venient to arrange- the species in smaller groups, which may be
designated by sub-generic names. In this way instead of the
binomial system, a polynomial system may be adopted in which
the name of an animal may have four parts, the generic, sub-ge-
neric, specific, and sub-specific names. Although too cumbrous
for general adoption this system has the merit of requiring a
close attention to variation, which is one of the most inte-
resting questions in Natural History.

3. In regard to the species we have been studying, the
generic name Amiurus embraces a large number of different
kinds of catfish from different parts of North America. Of
these different kinds three occur within our region, viz.:
A. nebulosus, A. natalis (Le Sueur) Jordan, (the yellow catfish),
and A. vulgaris (Thompson) Nelson, (the long-jawed catfish)*
some six other species are more southerly forms. The genus
is a " difficult " one, the species being hard to characterise and
it is doubtful whether all the species are " good." For example
there is a southern form which is sometimes regarded as a dis-
tinct species [A. marmoratus (Holbrook) Jordan], sometimes
merely as a mottled variety of our northern form, and conse-
quently named by the zoologists who hold this view A. nebulosus
var. marmoratus.

HIGH SCHOOL ZOOLOGY. 53

4. Those characteristics which the individuals of a species
possess in common, and which serve to distinguish them from
individuals of another species are expressed together with th ir
habitat, or range of geographical distribution, in a specific
diagnosis ; as examples the following diagnoses of the species
which occur in Ontario may be copied from a recognized
authority : —

A. nebidosus (Le Sueur) Gill.

Colour dark yellowish-brown, more or less clouded, sometimes yel-
lowish, sometimes nearly black. Body rather elongate ; depth contained
4 times in length (measured to the base of the caudal fin). Anal fin
usually with 21 or 22 rays, its " base contained 4 t'mcs in the length of
the body. Dorsal fin inserted rather near the adipose than the end of
the snout. Upper jaw usually longer than lower. Humeral process
more than half the length of the pectoral spine. Length 18 inches.
Great Lakes, Ohio Valley, and Eastward. The common bullhead or
horned pout of the North and East, abundant in every pond and stream,
also introduced into the rivers of California, where it has rapidly multi-
plied.

A. natalis (Le Sueur) Jordan.

Yellowish, greenish or blackish. Body more or less short and chubby,
sometimes extremely obese (var. natalis), sometimes more elongate
(var. Hindus). Head short and broad. Mouth wide, the jaws equal
(var. Hindu*), or the upper jaw longest (var. cupreus). Anal rays 24-27.
Great Lakes to Virginia and Texas ; generally abundant. Extremely
variable, and running into several varieties.

A. vulgaris (Thompson) Nelson.

Dark reddish-brown or blackish. Body moderately elongate ; depth
4-5 in length. Head 3-4. Barbel long. Mouth wide. Head longer
than broad, rather narrowed forward. Profile rather steep, pretty
evenly convex. Dorsal regions more or less elevated. . Lower jaw
strongly projecting. Anal rays 20. Length 18 inches. Vermont to
Minnesota and southward ; rather common.

It will be observed that the distinguishing features of these
three species are to be found in the shape of the body, the length
of the anal fin, and the relative length of the jaws»

54 HIGH SCHOOL ZOOLOGY,

5. The generic, specific, and varietal names are generally
Latin or latinized Greek words in form, the generic name
being always a noun, and the specific and varietal names either
adjectives agreeing therewith, or nouns in apposition. Although
these names often refer to some characteristic of the form de-
signated, yet this is not always the case, and there is no definite
understanding among zoologists as to the principle on which
such names shall be selected. For example the name Amiurus
has been formed to express the fact that the tail-fin is not notch-
ed in this genus, whereas the name of the most nearly allied
genus Ictalurus or Ichthselurus, where the tail is notched, is
simply a Greek translation of Catfish. Again the specific
adjectival name nebulosus is formed to express the peculiar
clouded colouration of our Catfish, while its synonym catus, a
noun in apposition with Amiurus is another reference to its
common name; further, the varietal names marmoratus, lividus,
cwpreus are adjectives expressing some colour-peculiarity of
the forms designated, while the specific name of our great fork-
tailed Catfish /. lacustns refers to its occurrence in large bodies
of water.

6. The species last referred to attains a large size, reaching
occasionally a weight of 100 pounds; it is abundant in the
Great Lakes and St. Lawrence, and is much used for food.
Another allied form the Channel Cat (/. punctatus) is found in
the channels of the large streams but does not reach the size
of the great Catfish. In contrast to these are several species
of Noturus — Stone-Cats, (Fig. 20) which are rarely more than
4 or 5 inches in length, have the habit of lurking under stones,
and are marked by the long adipose fin which is almost con-
tinuous with the tail -fin.

7. These three genera are the representatives in Canada of
a very large group or " family " of Fishes, the members of which
abound in the fresh waters of the tropics of the old and new
world, but are only represented in Europe by one species the

HIGH SCHOOL ZOOLOGY, 55

Fig. 20.— Stone Cat. Noturus gyrlnus.
(After Jordan).

Sheat-fish (Silurus glanis) of the Danube. By adding the
patronymic ending " idae " to the stem of the generic name of this
fish, the family name Siluridae is formed which thus includes all
the genera of the group. Family names are generally formed
in this way from some typical or well known genus, and if it
is considered desirable to arrange the family into sub-families
the termination "ina" is generally employed for such smaller
groups. But, as in the case of species and genera, zoologists are
by no means at one in recognizing the same limits to the classifi-
catory sub-divisions employed. Nevertheless the divisions of
various rank are always sub-ordinated to each other in a definite
way, thus each of the great primary divisions of the Animal
Kingdom or Sub-Kingdoms is divided into Classes, each Class
into (Sub-Classes and) Orders, each Order into (Sub-Orders and)
Families, while each Family (sometimes sub-divided into Sub-
Families or Tribes) includes one or more genera according as
the species belonging to it are more or less nearly allied to each
other.

8. Thus the Siluroid family as generally understood is one
of the largest of the class Pisces ; it is also a very heterogeneous
one, embracing such different forms as our Catfish and the
curious mailed Siluroids of the South American Rivers, so that
certain authorities consider it to have the rank of an Order
(Nematognathi), and it certainly does contain forms which are

56

HIGH SCHOOL ZOOLOGY.

structurally far more diverse than is the case in other Families
of Fishes. All of its members possess the barbels, the well
developed premaxillaries, and the rudimentary maxillary bones
of the Catfish, they lack the sub-operculum, but they all have
the curiously modified anterior vertebrae and air-bladder, although
sometimes these are difficult to detect. They are for the most
part fresh- water forms, but a few are marine.

As we have studied a representative of this group in detail,
some account of its most striking tropical forms may be of
interest.

Reference has been only marie to the fresh-water catfishes above ; there
are, however, representatives of the family on the sea coast extending
from Cape Cod southwards. These belong to two genera, Alius and
■ffilurichthys, which agree in having the head armed above with bony
shields; in this respect they are less like our cattish thin the large cat-
tish of the Nile ( Bagrus) and of the S.nith American rivers ( Pimelodus)
are, and they more nearly approach certain othjr South American forms —
Doras and its allies, where the head is completely mailed, but where the
branchial aperture is reduced to a mere slit so that water can be retained
in the gill-cavity. This latter condition also occurs in the Electric Cat-
fish of the Nile ( Malapterurus, Fig. 21) which has no exoskeleton, but
has the superficial layer of muscles converted into an electric organ.

Fig. 21.— Electric Catfish of the Nile. M lapterurus electricus. &.
(After Brehm>

HIGH SCHOOL ZOOLOGY. 57

A great many of the South American Siluroids have a very complete
exoskeleton. Callichthys and Loricaria (Fig. 22) are representative
genera ; they all appear to be very tenacious of life out of water, their
gill-cavities being arranged as in Doras. Aspredo is a singular genus
in which the female carries about the eggs attached to papillae of the
skin of the ventral surface, until they are hatched.

Certain old-world tropical forms are provided with arrangements
better adapted than those referred to above for living out of water.
Clarias, Saccobranchus and others have a recess projecting backwards
from each gill-cavity which can be filled with water.

Fig. 22.— Mailed Siluroid, from South America. Loricaria cataphracta. J.
(After Brehm.)

9. A very large number of our fresh-water fishes belong to a
%mily nearly allied to the Siluroids, that of the Cyprinidae,
embracing the suckers, carps, goldfish, minnows, shiners, etc.,
of which the suckers are sometimes reckoned as an independent
family (Catostomidae). Although very different externally
from the Siluroids (for they are generally scaled fishes and often
brillantly coloured), yet they share the peculiar struc ure of
the anterior vertebrae and air-bladder, which is present in
that group. The gill-cover has all the four bones, but there is
no adipose fin. There are no teeth on the jaws, but the
pharyngeal bones are well provided therewith. On the roof of the
mouth in front of the first gill there is a rudimentary fifth gill
called a pseudobranch, through which only arterial blood
5

58 HIGH SCHOOL ZOOLOGY.

circulates; its meaning will afterwards be explained. This
family is characteristically a fresh-water one, the section of the
Catosomidae being nearly confined to North America, and in-
cluding our suckers, lake-mullet (Fig. 23), carp and carp-suckers,
while the rest of the Cyprinoids are abundantly represented in
the Old "World as well as the New. The suckers and their allies
attain a large size, but the rest of the group are small and very
similar in form and colour, so that they are difficult to diagnose,
and much remains to be found out as to their distribution in
Canada. Two further peculiarities of the family may be re-
ferred oo, the bright colouring of the males at breeding time in
the spring, and the division of the air-bladder into two or three
compartments by transverse constrictions.

Fig. 23.— The Red Horse. Moxostoma macrolepidotum. \.
(U. S. Fish Commission.)

10. The Siluroids and Cyprinoids, like several other fami-
lies of Teleostei, have an open duct between the air-bladder
and the oesophagus; all the families which possess this are
known as the Physotomous Teleosts, while those in which the
air-duct is absent are known as the Physoclystous Teleosts." We
shall find some familiar forms among the remaining Physostomi,
which have the anterior vertebrae separate from each other and
unconnected with the air-bladder. Foremost in importance,
from an economical point of view, is the family of the Salmon-
idse, which contains so many valuable food-fishes. Chief among
these is the Atlantic salmon, {Salmo solar, Linn.) (Fig. 24)

HIGH SCHOOL ZOOLOGY.

59

which ascends rivets on both sides of the Atlantic for che pur-
pose of spawning, and is consequently described as migratory
or anadromous, although it is able to live also permanently in
fresh water. Such " land-locked " salmon used to be abundant
in Lake Ontario.

Fig. 24.— The Atlantic Salmon. Salmo salar. fj.
(U. S. F. C).

The Pacific salmon, which are canned in enormous quantities in Brit-
ish Columbia, belong to an allied genus Onchorhynchus.

11. Our common Lake Trout and Brook Trout belong to a
genus Salvelinus differing from Salmo in the absence of teeth
on the vomer ; the former (S. namaycush) attains a large size,
and is abundant in the larger lakes, the latter (S. Jbntinalis) is
found in ponds and streams, and is well known by its brilliant
colouring, except in those individuals which have access to the
sea, and which replace the red spots and dark bars by an uni-
form silvery dress. Hardly less important are the common
Lake species of White fish {Coregonus clupeiformis) and Lake
Herring or Ciscoes (G. artedi) (Fig. 25) which differ from the

Fig. 25.— The Cisco, or Lake Herring. Coregonus artedi. $.
(U. S. F. C.)

60

HIGH SCHOOL ZOOLOGY.

Salmons by their large scales and toothless jaws. Both Salmon
and White-fish have certain appendages of the intestines which
are not present either in the Siluroids or Cyprinoids ; these are
situated at the junction of the stomach and intestine and are
known as the pyloric coeca. They serve to increase the digest-
ing and absorbing surface of the intestines. They are small
and few in number in certain smaller marine Salmonidae such
as the Capelin (Mallotus villosus) (Fig. 26) and Smelts
(Osmerus mordax) (Fig. 27), which in spite of their size are of
some importance as food-fishes. All of the Salmonidae have
cycloid scales, a pseudobranch and an adipose fin.

Fig. 26. — The Capelin. Mallotus villosus.
(U. S. F. C.)

Fig. 27.— The Eastern Smelt. Osmerus mordax.
(U. S. F. C.)

12. Another important family is that of the Clupeidae or
Herrings which are nearly all marine fish with a much com-
pressed body, a serrated abdomen and no adipose fin. The
commonest species are the herring, C. harengus L. and the Shad,
C. sapidissima ; the former spawn in the sea, the latter ascend
rivers to do so. One species of Clupea the Alewife (C. verncdis)

HIGH SCHOOL ZOOLOGY.

61

is land-locked in certain inland- waters, and the same is tnie of
the allied Gizzard-Shad (Dorosoma cepedianum) (Fig. 28).
The latter is of no value as a food-fish nor is the Moon-eye
(Hyodon) also allied to the Herring- family, but the Anchovies
(Engraulus) are much esteemed for their flavour.

Fig. 28. — The Gizzard-Shad. Dorosoma cepedianum — var. heterurum. \.
(U. S. F. C.)

13. More familiar to inland residents is the family Esocidae,
a group which is found in the fresh waters of the northern
parts of both hemispheres. The largest representative is the-
Muskallunge, Esox nobilior, Thompson (Fig. 29), but the corn-

Fig. 29.— The Muskellunge. Esox nobiUor. -fa.
(U. S. F. C.)

mon species is the Pike, E. lucius, which is marked with light
spots on a darker ground. All the species are voracious and
are provided with a large mouth armed with strong teeth. The
body is slender and elongated, there is no adipose fin, the pseudo-
branchs are concealed and there are no pyloric cceca. As

62 HIGH SCHOOL ZOOLOGY.

allied to the Esocidae may be mentioned the Umbridae, one
species of which, the little mud-minnow {Umbra limi), is to be
found widely distributed in muddy ditches. The mud-minnow
is in some respects allied to the Blind-Fishes of the Southern
states (Amblyopsidae ), the best known of which and the largest
is A. spelceus from the subterranean waters of the Mammoth
Cave, Kentucky. In accordance with the subterranean life
the Blind-fish is colourless, the eyes are extremely rudimentary,
but the sensitiveness of the skin is increased by tactile organs
like those described in § 9, which are elevated on rows of papillae
above the general level of the skin. In all this family the
intestine turns forward and opens underneath the throat.

14. The last Physostomous family to which reference need be
made is that of the Anguillidae, chiefly marine forms, but
represented in our inland waters by the common Eel (Anguilla
rostrata). The absence of ventral fins, the confluence of the
unpaired fins round the tail, the absence of hard rays, and the
rudimentary scales embedded in the soft skin, are some of the
chief superficial peculiarities of the group. Allied families are
those to which the Bengal Amphipnous belongs, which has an
air-sac communicating with the gill-cavity, and the Brazilian
Gymnotus or Electric Eel, in which as in Malapterurus the
muscles of the tail are converted into an electric organ.

15. Physoclysti. — In this division of Teleosts the ventral
fins are usually in the course of their development shifted for-
ward till they attain a position either beside or in front of the
pectoral fins : they are then said to be thoracic or jugular. The
unpaired fins have generally hard rays. This is especially the
case in the Acanthopteri, the largest of the orders of Teleosts,
to which a vast number of marine forms belong, but which are
also represented in fresh-water by the bass and perch tribes.
Although the air-bladder never communicates with the ali-
mentary canal in the adult, yet it is developed from it in the

HIGH SCHOOL ZOOLOGY. 63

young, and is only afterward closed. It is filled with air from
certain blood-vessels which are so arranged as to allow an in-
terchange between the gases of the blood and those of the air-
bladder. However great the difference in this way between
Physostomousand Physoclystous Teleosts, yet there are some of
the latter which are transitional in other respects. The family
of the Scomberesocidae recalls both the Pikes (Esocidae) and
the Mackerels (Scombridae). In addition to the long-billed
marine Gar-fishes, several interesting species of Flying-fish,
Exocoetus (Fig. 30), belong to it, marked by the great size of the
pectoral (and ventral) fins. These creatures throw themselves
out of the water by means of the strong muscles of the tail, and
sustain themselves in the air by spreading the fins.

Fig. 3 . — California Flying Fish. Exocoetus Californiensis.
(U. S. F. C.)

16. Before discussing the typical Physoclystous fishes a passing refer-
ence may be made to certain aberrant forms which attract attention by
the peculiarity of their shape. The Pipe fishes (Syngnathus), and Sea-
horses (Hippocampus) (Fig. 31), agree with each other in the structure of
their gill-filaments, which are arranged in tufts (Lophobranchii), like the
teeth of a comb. The snout is much produced, the mouth toothless and
the gill-cover a single plate. The Tobacco-pipe fishes (Fistularia) have
the ordinary gill-structure, but share the elongated body and produced
snout of the pipe-fishes. Allied to them are the Sticklebacks (Gasteros-
teidse) of fresh and brackish waters (Fig. 32), a group of tiny pugnacious
fishes which live on the fry of larger fish, but take care of their own in a
nest which is constructed and defended by the male. Some of the
species have regular bony plates on the side of the body : these however,
are absent in our common nine-spined and Brook Sticklebacks.

64 HIGH SCHOOL ZOOLOGY.

Fig. 31.— Syngnathus (Pipe-Fish) and Hippocampus (Sea-Horse).
(After Brehm).

Fig. 32.— Two-spined Stickleback. Gmterosteus aculeatus.
(U. S. F. C.)

17. The most characteristic group of Acanthopteri in our
region is that of the Sunfishes, Centrarchidse, as a type of which
family the common Rock Bass, Ambloplites rupestris (Fig. 33),
may he examined. It shares the short compressed body of the
rest of the family, the mouth is large and well provided with
teeth, for all are carnivorous and voracious forms. The preop-
ercle is serrated, the opercle ends in two flat points. The dorsal
fins are confluent, there being eleven hard rays in front and

HIGH SCHOOL ZOOLOGY.

65

ten soft behind (written D, XI, 10), while the anal fin is VI, 10.
Like the other members of the family the colouration is some-
what brilliant olive-green, tinged with brassy hues and mottled
with darker colours. Ctenoid scales of considerable size clothe
the body ; there are 56 of these along the lateral line in this
species. The pseudobranchs are small, and the intestine short
and provided with 7 pyloric coeca.

Fig. 33.— The Rock Bass, jimbloplites rupestris, $.
(U. S. P. C.)

Besides the Rock Bass several other species of larger size and
gamey habits attract the sportsman. These are easily diagnosed
by the fin-formula, which for the Grass Bass (Pomoxys sparoides)
is D.VII, or VIII, 15; A. VI, 1 7 or 1 8: for several species of Sun-
fish, (Lepomis auritus and gibbosus) D. X, 1 1 ; A. Ill, 9: and for
the large- and small-mouthed Black Bass (Microplerus salmoides
and dolomieu) D. X, 1 3 ; A. Ill, 11. The two latter are well
known game-fishes, and apart from the size of the mouth, may
be distinguished by the scales of the former being 65-70 along
the lateral line and 7-8 in a vertical row above the lateral line,
while in the latter they are respectively 72-75 and 10-12.

18. In the nearly allied family of the Percidae, the dorsal
fins are not confluent, the a*al spines are less numerous, the
pseudobranchs are smaller, and the pyloric coeca fewer. Two
well marked groups, distinguished alike by size and habit, are

66 HIGH SCHOOL ZOOLOGY.

recognized, the Percina (including the common perch \Perca
americana] and the larger Pike-Perches or Pickerels [Stizosted-
ium] as they are generally called in Ontario, and the Etheostom-
atina or Darters. The pickerels attain a greater size than the
perch, and are valued food-fishes. The larger species, S. vitreum
has three pyloric cceca, its fin formula is D.XIII — I, 21; A. II, 12,
while the smaller S. canadense (Fig. 34) has 4-7 cceca, and the
soft dorsal is shorter by three rays. Like the perch the picker-
els have a good deal of brilliant yellow colouring on the sides
and are called" dorees " in the Lower Province.

Fig. 34.— The Pickerel. Stizostedium canadense. |.
(U. S. F. C.)

19. Little is known with regard to the distribution of the
Darters in Ontario. They are a characteristic American group,
being amongst the smallest of the Fishes,, and distinguished
further by their bright colours, rapid movements, large fins,
and the rudimentary condition of the pseudobranchs and air-
bladder. Some of them conceal themselves under sand, the eyes
alone remaining uncovered, the better to pounce rapidly upon
the active insect larvae on which they feed. The largest of the
group, the Log- Perch (Percina caprodes), attains a length of
6-8 inches, and may be recognized by its black, banded sides,
the smaller forms are the Sand-dartei (Ammocrypta), Tesselated
darter (Boleosoma ) and the Striped darter (Etheostoma).

20. Among the marine families allied to the above that of
the Serranidse requires mention. It embraces the so called Sea-

HIGH SCHOOL ZOOLOGY. 67

bass, one of which, the Striped bass {Roccus lineatus), is much
valued as a food fish, and is represented in our inland waters
by the white bass R. chrysops (Fig. 35). Both of them are

Fig. 35.— The White Bass. Roccus chrysops. |.
(U. S. F. C.)

marked by blackish longitudinal lines, which are more distinct
and continuous in the former species. The pseudobranchs are
large and the dorsal fins nearly or quite separate.

21. Of the other numerous marine forms of Acanthopteri,
the following may be mentioned as of interest, the Mackerel
Scomber scombrus (Fig. 3o) with its numerous dorsal and anal

Fig. 36.— The Mackerel. Scomber scombrus. $.
iV. S. F. C.)

finlets, the Tunny Orcynus thynnus (Fig. 37) one of the largest
of Teleosts, the Sword-fish (Xiphias gladius) (Fig. 38) with its
upper jaw prolonged into a sword, and the Sucker (Echeneis
remora) (Fig. 39) whose dorsal fin is converted into a sucking
disc by which the fish attaches itself to moving bodies. A

68

HIGH SCHOOL ZOOLOGY.

Fig. 37.-- The Horse Mackerel, or Tunny. Orcynus thynnus. &.
(U. S. F. C.)

Fig. 38.— The Sword Fish. Xiphias gladius. 4V
(U. S. F. C.)

Fig. 39.— Sucking Fish. Echeneis remora. J.
(After Brehm.)

HIGH SCHOOL ZOOLOGY. 69

similiar method of adhesion to rocks, &c. occurs in the lump-
suckers (Cyclopterus) (Fig. 40) where the ventral fins form the
centre of the sucking disc.

Fig, 40.— Lump Fish. Cyclopterus lumpm. \.
(U. S. F. C )

In addition to the Flying-fish above mentioned, one of the
Gurnards (Triglidae) possesses the power of flight. (Fig. 41).

Fig. 41.— The Striped Sea Robin. Prionotus evolans. \.
(U. S. F. C.)

22. Of all the families of Teleosts mentioned, few can com-
pare in economical importance with the Gadidae and Pleur-
onectidse, which differ very much from each other in their general
appearance, but agree in the absence of hard rays from the fins,

70 HIGH SCHOOL ZOOLOGY.

whence they are sometimes called Anacanthini. They are
marine forms for the most part, the first family including the
Cod-fish and Haddock (Gadus callarias and ceglefinus) with a
host of less important food fishes, and being represented in our
inland waters by the burbot, Lota maculosa (Fig. 42). The

Fig. 42. -The Burbot. Lota maculosa. |.
(U. S. F. C.)

latter genus has two dorsal fins and one anal, the former three
dorsal and two anal; in both the ventral fins are jugular in
position. To the second family belong the Halibuts, Flounders,
and Soles (Fig. 43) which are generally spoken of as Flat-fish.

Fig. 43.— The Smooth Flounder. Pleuronectes glaber. J.
(U. S. F. C.)

from the fact that at an early stage of development they swim
upon one side, which becomes colourless and blind from the eye
moving towards the upper surface of the head.

HIGH SCHOOL ZOOLOGY.

71

24. Any account of the Teleostei would be incomplete with-
out a reference to the Plectognathi, a group which includes some
tropical fish of very bizarre appearance. The File fishes (Balistes)
(Fig. 44) receive their name from the form of the first dorsal
spine, the Trunk fishes (Ostracion) (Fig. 45) are enveloped in

Fig. 44— The File, or Trigger, Fish. Balistes captistus. §.
(U. S. F. C.)

Fig. 45'-The Trunk Fish.— Ostracion quodiicorms. J.
(U. S. F. C.)

a complete box formed of bony plates, the Porcupine-fishes
(Diodon) (Fig. 46) are covered with long sharp spines, but all
agree in the firm union of the bony elements of the jaws to
which they owe their name.

72 HIGH SCHOOL ZOOLOGY.

Fig. 46.— The Porcupine Fish. Chilomycterus geometricus. J.
(U. S. F. C.)

24. By far the greater number of the Fishes of the present
day belong to the Sub-Class Teleostei, but in past geological
times such was not the case, and large numbers of fossil forms
are known which indicate that the other sub-classes, which are
but sparingly represented by living forms, were at one time as
abundant as the Teleosts are now. One of these Sub-Classes,
the Ganoidei, we have exceptional opportunities for studying on
this Continent, because out of the nine genera six are American.
The peculiarities which distinguish the Ganoids from the
Teleosts may be best learned by comparing any one of them
with a catfish, which of all the Physostomi comes nearest to the
Ganoids. As to its skin the Ganoid is rarely smooth, but
generally covered with bony plates or scales which may be rough
with teeth or smooth with enamel ; the skeleton is cartilaginous
in the Sturgeon, but as well ossified in the Garpike and Amia
as it is in the Catfish. The heart has a muscular arterial cone
with several rows of valves; the pseudobranch of the Teleosts
may be either present as such, or, as in the Sturgeon, as a
functional half-gill on the hyoid arch. A gill-slit without any
functional gill persists in the form of the " spiracle " in the
Sturgeon between the hyoid and the mandibular arch, and is
more or less complete in the other forms, but the other gill-slits
are concealed as in the Teleosts by a gill -cover. The air-bladder
opens by a wide duct into the oesophagus and is very richly
supplied with blood, so that in some forms it acts as an accessoiy

HIGH SCHOOL ZOOLOGY.

73

breathing organ. A fold of mucous membrane which serves to
increase the internal surface of the intestine and known as the
"spiral valve" occurs in all. Finally the vertebral column
evidently turns up at the tip in such a way as to divide the
caudal fin unequally or heterocercally

The American Ganoids fall naturally into two groups accord-
ing to the nature of the skeleton : in the Chondrostei it is
cartilaginous, in the Holostei osseous. To the former gro ip
belong the two families Polyodontidae and Acipenseridae, of
which the former includes the Paddle-fish, P. spatula (Fig. 47)

Fig. 47— .The Paddle Fish Pulyodon spatula. ^.
• (U. S. F. C.)

of the Mississippi, the latter the ordinary Sturgeon of our
Lakes (Acipenser rubicundus) (Fig. 48) and the Shovel-nosed

Fig. 48— The Lake Sturgeon. Acipenser rubicundus. ^j.
(U. S. F. C.)

Sturgeon of the Western and Southern States (Scaphirrhyn-
chops). In all of these forms the skull is a cartilaginous box
adapted to the shape of the brain and sense-organs, and covered
with regular bony plates of the same nature as those further
back in the body. Polyodon is remarkable for its paddle-shaped
snout by means of which it stirs up the mud in the river bottom,
on the minute organisms contained in which it feeds. These
are sifted out by means of the long and close set gill-rakers
which form a very efficient sieve for the muddy water which
flows out through the gill-slit. In many respects Polyodon
6

74

HIGH SCHOOL ZOOLOGY.

resembles the Sharks in its structure, as indeed do all the
Chondrostei, while the Holostei on the other hand approach the
Teleosts. The skin is comparatively smooth in the Paddle-fish,
but, in the Sturgeon, it is provided with five rows of bony keeled
shields, one row on the back and two on the sides, between
which shields, the skin is roughened with minute teeth.

25. Of the Holostei we have two genera, each representing a
separate family, Lepidosteus and Amia (Figs. 49 and 50). The

J***^!?^?^^^

Fig. 49.— The Garpike. Lepidosteus platystomus.
(U. S. F. C.)

Fig. 50.

-The Bowfin, or Mudfish.
(U. S. F. C.)

Atnia calva. i.

latter at first sight looks more like a Teleost, but a closer examin-
ation shows the dermal bones of the head, and the unequal divi-
sion of the tail. The superficial resemblance is chiefly due to
the regular rows of cycloid scales, while Lepidosteus is at once
marked out by the oblique rows of rhombic enamelled plates,
which encase it in a coat of mail. It is to this (and its voracity)
that it owes its name of bony-pike, while it is also called garpike
on account of the prolongation of both jaws into a beak, a
peculiarity present in the marine gar-fishes (§ 81). In many
cases where such complete protection is afforded by the exo-
skeleton, the endoskeleton is incompletely developed ; such is

HIGH SCHOOL ZOOLOGY. 75

not the case in Lepidosteus however, for here all the parts of
the latter are completely ossified, the vertebrae being in fact
more so than in other fishes, for their bodies are joined together
by a ball and socket joint, (the socket behind — opisthocoelous)
instead of having a cup at either end as in Amia and the Teleosts.
The commonest species is L. ossetis, but this is replaced in the
Southern States by a larger form which reaches a length of
eight or ten feet and is known as the Alligator gar.

26. Superficially very unlike the garpike, Amia nevertheless
resembles it very closely in internal structure. Its snout is
short and rounded, the lower jaws peculiar in being separated
by a flat skin bone, the jugular plate, but otherwise the skeleton
of the head is very similar to the garpike's.

The dorsal fin is long and low, whereas in the garpike, it is very
far back and short and high. The caudal fin is not so unequally
divided, and it is marked out in the male by an eyelike spot
which stands out against the general dark green hue. There
is only one species of Amia, A. calva ; it is known in different
localities by different popular names, among which Mud-fish
and Lake Dog-fish are the commonest.

27. In addition to the Ganoid genera already enumerated
there are two other living forms confined to the rivers of Africa.
These have scales like the garpike and gular plates like the
Dog-fish, but their paired fins differ in structure, being composed
of a disk-like part containing the skeleton surrounded by a
fringe. The commonest species is the Polypterus bichir of the

Fig.51. — Polypterusbichir. &.
(After Claus.)

Upper Nile (Fig. 51) the generic name of which refers to the
division of the dorsal fin into a series of finlets.

76 HIGH SCHOOL ZOOLOGY.

28. Reference was made above to the fact that of all Ganoids
Polyodon is most nearly allied to the Sharks. This is not
merely a superficial resemblance depending on the position of
the mouth but it is seen also in other organs. The gill-arches,
for example, bear between the two rows of filaments, a mem-
branous partition which is hardly present in any of the other
forms but which in the Sharks is much more developed, and
bears the gill filaments. Thus in the Sharks the gill-arches are
not separated by mere gill-slits, but by pouches, the anterior
and posterior walls of which are formed of the aforesaid parti-
tions. The pouches are, at least outwardly, always five in
number (sometimes seven), and they open by a series of slits
uncovered by any operculum (except in the genus Chimaera).
This disposition of the respiratory organs has conferred on the
Sub-Class the name Elasmobranchii.

It embraces marine forms familiarly known as Sharks and
Rays ; the former have elongated bodies with the gill-slits on
the sides of the head, the latter are flattened from above down-
wards, and as broad as they are long, from the enormous develop-
ment of the pectoral fins, which form the greater part of the
body. Their gill-slits are to be found on the lower surface of
the head. Certain forms are intermediate, in respect to the
size of the pectoral fins, between the Sharks and the Rays ;

Fig. 52. — The Saw Fish. Pristis pectinatus. ^j.
(U. S. F. C.)

the Sawfishes e.g., (Pristis) (Fig. 52), which are further dis-
tinguished by the enormous development of the rostrum or
snout and the formidable lateral teeth of that organ. Again

HIGH SCHOOL ZOOLOGY.

77

Fig. 53.— The Torpedo or Electric Kay. Torpedo occidentalis. &.
(U. S. F. C.)

the Electric Rays (Torpedo) (Fig. 53) are singular in that the
muscles of the pectoral fin are largely converted into an electric
organ. The Sharks (Fig. 54) are all carnivorous and voracious

Fig. 54.— The Horned Dog Fish. Squalus acanthias. £.
(U. S. F. C.)

forms of great strength and activity ; some of the smaller ones
(Mustelus) live on Shell-fish, but the largest species are often
dangerous to man and attain a length of thirty to forty feet
(Carcharodon, Selache). In all the Sub-Class the skeleton is
cartilaginous, and the skin either smooth or roughened with
minute teeth which are similar in structure to the more for-
midable teeth of the jaws. They resemble the Ganoids in
the structure of the heart and intestine, and in the unequal

78 HIGH SCHOOL ZOOLOGY.

division of the caudal fin, but they have no air-bladder. The
eggs are of large size and are either laid covered by a peculiar
horny shell or else the young are born alive.

29. Only another sub-class remains to be discussed, that of the
Dipnoi, so called on account of the fact that they breathe by the
modified air-bladder as well as by gills. Three genera belong
here, widely separated geographically, but all similarly situated
in that, during the dry season they may have to depend wholly
or partly on their lungs for the oxygenation of the blood. They
are named Lepidosiren, Protopterus (Fig. 55) and Ceratodus

Fig. 55.— The African Lung Fish. Protopterus annectens. j^.
(After Claus.)

and they are found respectively in the Amazons region of South
America, on the west coast of Africa, and in Queensland. As
regards the structure of the air-bladiler they resemble Lepidos-
teus and Amia, but in respect to the opening place of the air-
bladder into the oesophagus as well as to the skeleton and fins,
they more nearly resemble Polypterus. The group is of special
interest on account of the amphibious habits, and the changes
in the respiratory and vascular system rendered necessary there-
by. A point in which they resemble the true Amphibia is that
the nasal chambers open into the mouth, which is not the case
in any of the other fishes.

30. Two :: >e rrant groups of Vertebrates are generally associ-
ated with the fishes on account of their fish-like appearance,
although in structure they are very unlike them. These are
the Lampreys and the Lancelets. The former no doubt owe
some of the peculiarities of their structure to their parasitic
habits. They attach themselves by their round (Cyclostomi)

HIGH SCHOOL ZOOLOGY.

79

sucking mouths, which are armed with horny teeth but not
supported by jaws, to the bodies of other fish and prey upon
them. In general shape they are eel-like : several species are
known, some of them marine, but the
commonest inland species is the silvery
lamprey, Petromyzon argenteus (Fig. 56).
Apart from the structure of the mouth,
they are singular in the respiratory
organs, which have seven separate aper-
tures on each side, but only one opening
into the gullet. The marine genus
Myxine has similar habits, but different-
ly arranged gills. In all the forms the
skeleton is cartilaginous, and the noto-
chord forms the bulk of the vertebral
column.

31. A still further departure from the ordinary vertebrate
type is seen in the Lancelets, (Amphioxus or Branchiostoma)
(Fig. 57) little fish-like creatures which burrow in the sand of

Fig. 56.— Mouth of River

Lamprey.
Petromyzon argenteus.

Fig 57-

-Amphioxus lanceolatus.
(After Clan*,)

C, oral cirri; ch, notochord ; rm, spinal chord; ks, gills; ov, ovary; 1, liver:
N, kidney ; P, branchial pore ; A, anus.

the sea coast. They lack the brain, skull, and heart of the verte-
brates, but the spinal cord and notochord are present, and the
anterior part of the alimentary canal is employed for respiration.
32. The same is true of the marine Tunicata, so called on ac-
count of the tunic containing cellulose, secreted by the skin
around the body They pass through a larval tadpole-like phase,
but afterwards lose the tail, and with it the notochord and over-
lying nervous cord, adopting for the most part a stationary life,
during which many of them form colonies by budding.

80 HIGH SCHOOL ZOOLOGY.

CHAPTER III.

The Canadian Amphibia or Batrachia.

1. Among the Dipnoi the genus Protopterus is the most
truly amphibious, as during part of the year it lives in a torpid
condition in the dried mud of the river-beds and is entirely
dependent upon its lungs for respiration. It therefore deserves
to be called amphibious, far more than do certain members of
the Class Amphibia or Batrachia, such as the common Mud-
puppy or Menobranch of our Lakes {Necturus macnlatus)
(Fig. 58), which can live but a very short time out of water. It

Fig. 58.— Canadian Lake Lizard, or Menobranch.
(Necturus maculatus.)

is important to compare such a fish-like Batrachian with a true
fish, to find out the precise structural differences between the two.
The head in the Menobranch is flattened as it is in the catfish,
but a distinct neck separates it from the trunk, and here are
situated the three pairs of external gills attached to the outside
of the corresponding gill-arches and separated by two gill-slits.
It has been found that these slits correspond to those between
the first and second, and second and third branchial arches in
the fish.

HIGH SCHOOL ZOOLOGY.

81

No adult fish has external gills of this character, although the embryos
of various Elasmobranchs have, and Protopterus has three filamentous
gills attached to the pectoral arch.

Perhaps the greatest external difference is in the form of the
paired limbs, which no longer resemble the unpaired fin as they
do in fishes, but are jointed into the same divisions as they are
in the higher Vertebrates, and divided at the ends into fingers
and toes, of which there are four to each limb in the Menobranch.
But these limbs are not able to support the weight of the body •
the chief organ of locomotion is still the tail, and that is flatten-
ed and provided with an unpaired fin as in the fishes. It is
however not furnished with any skeletal support such as the
fin-rays of the fish.

2. At first sight the skin
of the Menobranch is very
like that of the catfish, but
care will be required to
make out the system of
sensory canals in the head
and along the lateral line,
and no traces of bony scales
will be found in the skin.

Microscopically the most im-
portant difference is in the pre-
sence of numerous cutaneous
glands which furnish the
abundant mucus which lubri-
cates the skin.

3. Important differences
will be detected in the
skeleton, but more in the
skull than in the vertebral
column. In the latter the
individual vertebrae are am-

phiccelous, and bear short ribs in the trunk region which do not
encircle the body cavity. There are no interspmous bones.

-Skull of Menobranch, from above.
(After Huxley.)
Pmx, premaxilla ; vo, vomer ; pi, palatine ;
sq, squamosa] ; pro, prootic; st, stapes ; epo,
epiotic ; fr, frontal ; ant, antorbital cartilage;
q, quadrate ; pa, parietal ; e, exoccipital.

Cartilage dotted ; cartilage-bones heavily,
membrane-bones lightly shaded.

82

HIGH SCHOOL ZOOLOGY.

Fig. 60.— Skull of Menobranch, from below. (After Huxley).

pmx. premaxilla ; vo. vomer ; mck. Meckel's cartilage ; pi. palatine r>s. para,
sphenoid ; hy. hyoid ; sq. squamosal ; pro. prootic; st. stapes ; epo. epioti<^

#

4. The skull retains more cartilage than does that of the cat-
fish, and there are fewer bones to be recognised in it. (Figs. 59
and 60). Of the twenty-seven cranial bones present in the catfish
(I, 17-20), only thirteen are represented, viz.. — paired exoc-
cipitals, epiotics, prootics, frontals, parietals and vomers, and an
unpaired parasphenoid. Some of the other bones are represented
by cartilage such as the mesethmoid and parethmoid \ the nasal
capsule also is a fenestrated cartilaginous capsule, but the
other regions are only membranous. Two new bones are pre-
sent, the squamosal and the suspensorium on each side, which
lie on the outside of the otic capsule, and thus occupy somewhat
the same position as the pterotic and preoperculum.

As to the jaws, Meckel's cartilage is furnished with a dentary
and an inner splenial bone, and it is hung to the skull by the
Suspensorium, a cartilage which corresponds to the hyomandi-
bular and quadrate of the catfish. Part of- the hyomandibular

HIGH SCHOOL ZOOLOGY.

83

may be represented by a small stapes or columella which fills
up a gap or window (the fenestra ovalis) in the outer wall of
the auditory capsule, present in all Vertebrates except fishes.
A pterygopalatine rod and premaxillse are present on each side,
but the maxilla is even more rudimentary than in the catfish.
There is no gill-cover nor branchiostegal rays, but the visceral
skeleton is well represented, although the hinder arches are
reduced in comparison with the catfish. (Fig. 61).

Fig-. 61.— Visceral Skeleton of Menobranch.
(After Huxley).

h. hypohyal ; ch. ceratohyal ; bb. first, bb2. second basibranchial ; cb1, cb2, first
and second ceratobranchials ; eb1, eb2, eb3, 1st, 2nd and 3rd epibranchials ; gl. glottis.

5. Great difficulty will be met with however, in com-
paring the limbs and the girdles which support them with the
corresponding parts in the catfish (Fig. 62). There the cora-
coids are bony and articulate in the middle line ; here they are
cartilaginous and overlap the middle line ; they furthermore
each give off a process jutting forward, the precoracoid, some-

84

HIGH SCHOOL ZOOLOGY,

times called the clavicle, but a very different structure from the
various parts so called in the catfish. Again, the scapula is of
much greater size, is ossified and has a cartilaginous leaf-like
part above, which nearly reaches its fellow of the opposite side
near the middle line of the back. Still the limb is attached to
the girdle at the junction of the coracoid and scapula, just as
it is in the catfish, only the method of its attachment and the

*. 62.— a, Skeleton of Anterior, b, of Posterior, Extremities of Menobranch.

pc. precoracoid ; s. scapula ; ss suprascapula ; co. coracoid ; gl. glenoid cavity for
h, humerus ; u. ulna ; r. radius ; u-f i. ulnare + intermedium; r1. radiale ; c. centrale ;
1 — 4, distal carpal row. m. metacarpals; I — IV. digits.

p. pubis ; i. ilium ; is. ischium ; a. acetabulum for fe. femur ; f. fibula ; t. tibia ; f +i,
fibulare -f- intermedium ; t. tibiale ; c. centrale ; 1—5. distal tarsal row j m. metatar-
sals ; I— IV. digits.

HIGH SCHOOL ZOOLOGY. 85

nature of its component parts are very different. Only one
bone, the humerus, effects the attachment and forms the skeleton
of the upper arm ; two, the radius and ulna, are in the fore arm,
carpal or wrist bones intervene between these and the skeleton
of the fingers, which consists in each of a metacarpal bone
and three phalanges. How are we to compare these parts with
those in the catfish 1 It is only possible to do so by studying
fishes more primitive in this respect, but investigation appears
to show that the humerus is comparable to the metapterygial
basal in the catfish, and the other bones to rays in connection
therewith. Still greater difference is to be found in the
pelvic arch, for what is called so in the catfish is nothing more
than the united basals of the fin, whereas in the Menobranch
we have a partly cartilaginous and partly osseous pelvic
girdle, writh the three constituent regions which we shall find in
all the higher forms. Of these the uppermost (ilium) enters into
intimate union on each sido with the transverse processes of
one of the vertebrae. A similar arrangement exists in all
Vertebrates except fishes, and the vertebra (or vertebrae) in
question, by which this additional stabili'y of the posterior
extremity is secured, is called sacral. Corresponding to the glen-
oid cavity for the attachment of the humerus is the acetabulum
for the hip joint. The structure of the skeleton of the hind
limb is very similar to that of the fore, and the corresponding
parts to those enumerated in the last paragraph are, 1. femur,
2. tibia and fibula, 3. tarsal bones, 4. the metatarsals and
phalanges.

6. As the greatest difference in the bony framework is in
the limbs, so also the greatest difference in the muscles is to be
met with there, but the limbs are of course more differ-
entiated in the higher Amphibia, where they have to perform
more complicated duties in connection with support and
locomotion.

86

HIGH SCHOOL ZOOLOGY.

Fig. 63.— Brain of Menobranch.
A. From above. B. From below.

7. Ill regard to the nervous sys-
tem of the Menobranch, the most
notable difference from the catfish
will be found in the brain (Fig. 63).
Here the olfactory lobes are united
with the larger and thicker- walled
cerebral hemispheres ; the inferior
lobes are not present, the optic lobes
not so distinctly divided into right
and left halves, the cerebellum
quite rudimentary, and the medulla
oblongata destitute of those swell-
ings present in the catfish.

8. The teeth in the Menobranch
are not only less numerous, but
they are confined to smaller sur-
faces within the mouth. There are

Rh. Olfactory lobes; Pr. Cerebral . . ,, . n . . ,

hemispheres ; Thai. Thalamic region ; two TOWS m the Upper jaw, 01 which
Mes. Optic lobes ; cb. cerebellum ; h. , , , ,, ,

hypophysis; Met. Medulla oblongata ; the posterior (on the Vomer and
2nd, 5th, 8th, 9th. Cranial nerves. • i \ • xi i i -i xi

pterygoids) is the longer, while the
mandible has only a single row fitting in between the two of the
upper jaw. Unlike the fish there is a fleshy tongue free in
front and at the sides, and the tubercles on the concave surfaces
of the gill-arches are not so prominent as in the catfish. The
intestine hardly departs from the tubular form, the liver is
more elongated, and the pancreas quite independent and much
subdivided.

It is interesting to compare the lungs with the air-bladder of
fishes. The glottis is supported by two slips of cartilage which
occupy nearly the position of the fourth branchial arches; it
opens into a common chamber whence the thin-walled lungs
project backward and two short blind sacs forward ; the latter
remind one of the similar points which are present in the air-
bladder of Amia.

HIGH SCHOOL ZOOLOGY.

87

Fig. 64.— Diagram of Heart
and Great Vessels of right

side of Menobranch.
Co. Arterial cone ; v. ven-
tricle ; a. auricle ; i, ii, iii, af-
ferent branchial arteries; G1,
G 2, Gs, the three gills; ce, ci,
external 4 internal carotids ;

9. A comparison is more easily effected
between the heart and great vessels of the
Menobranch, and those of Amia and Lepi-
dosteus or one of the Dipnoi, than those of
the cattish, because the ventricle has a
muscular cone in these forms which is ab-
sent in the catfish. From this the arterial
trunk comes off in front (Fig. 64) and di-
vides into two right and left branches,
which afterwards subdivide to form the
three afferent branchial arteries for the
three gills. The blood which is aerated
in the foremost and largest gill is partly
sent to the head, but partly joins that
from the efferent arteries of the second
Pa. Pulmonary artery; o. and third gills, so as to form the dorsal

branch to oesophagus and c P ., , , , P ', ,

stomach; L. lung ; d. dorsal aorta, fcome ot the blood ironi the second
and third aortic arches reaches the lung
(only, however, in a partially aerated condition) through the
pulmonary artery, a modified fourth arch ; its aeration is com-
pleted in the lung, whence through a separate vessel, the
pulmonary vein, it reaches a special compartment of the
atrium, not quite separated off from the rest, but partly so by
an imperfect partition. In higher Amphibia this partition is
perfect, so that the blood within it is not mixed in the ventricle
with the returning venous stream, until some of it has been
already sent on to the head through the modified first arches
(carotid arteries).

10. The kidneys are narrow ribbon like structures which
extend through the greater part of the length of the body
cavity. It is supposed that the Menobranchs spawn in spring,
and that they lay eggs nearly of the size of a pea, but further
information is desirable as to their habits in this respect.

88

HIGH SCHOOL ZOOLOGY.

11. Class Batrachia or Amphibia. This class is subdivided
into several orders of which three are represented by living
forma, the Urodela, Anura, Gymnophiona, the others being
known merely by their fossil remains. The first order contains
the Menobranch and forms allied to it ; the second, the frogs and
toads ; and the third, certain tropical earthworm -like forms.
Tt is, therefore, the first two which we have to examine more
closely, the ordinal names of which refer to the most striking
character, the presence (Urodela) or absence (Anura) of a tail in
the adult.

12. Among the nearest Urodelous allies of the Menobranch
are some which like it retain their gills throughout life : they are
said to be perennibranchiate forms, and in this respect are unlike
some other Urodeles which lose their gills at a later stage ;
these are caducibranchiate. Undoubtedly the nearest relative of
our Necturus is the Proteus (P. anguinus) (Fig. 65) which is
found in underground waters in Carinthia and Carniola. Like
the blind-fish of the Mammoth cave it has suffered the almost
complete loss of the eyes and the loss of the pigment of the

Fig. 65.— Proteus anguinus. (After Brehin);

HIGH SCHOOL ZOOLOGY.

89

skin ; the gills, therefore, with the red blood coursing through
them, stand out very conspicuously from the colourless body.
Instead of the four toes of Necturus, there are three on the front
and two on the hind limbs. The only other genus of this
group is the Siren, of the rice-swamps in the Southern States,
S. lacertina (Fig. 66) which is eel-like in shape, and lacks the
hind limbs. It is less aquatic than either of the other genera,
and is able to live out of water for a longer time.

Fig. 66.— Siren lacertina. (After Brehm.)

13. Of the caducibranchiate Urodeles two genera, Amphiuma
and Menopoma, must be regarded as nearest to the foregoing, on
account of the fact that in spite of the loss of the gills, one gill-
slit on each side (that between the third and fourth gill-arches)
persists, whereas in the other forms all. trace of these disappears
in the course of development. Amphiuma (Fig. 67) is an eel-
like form from swamps in the Southern States ; both pairs of
legs are present, carrying in one species two, in the other three,
toes. Menopoma comes further north, being abundant in the
Ohio Valley where it is known as the Hellbender ( M. alleg/iani-
7

90

HIGH SCHOOL ZOOLOGY.

Fig. 67. — Amphiuma tridactyla. (After Brehm).

ense). It attains a length of two feet and has better developed

limbs (with four and five toes) than the foregoing.

A nearly allied form, destitute of the gill-slit, is the giant Salamander
of Japan, which grows more than five feet in length.

14. All the other Urodeles are aquatic only in their young
stages, and afterwards leave the water for the land where
they live either in moist or dry places. As a general rule
the tail is rounded in those which have most completely
abandoned the aquatic life, in the others it is somewhat com-
pressed. When the new habit of life is adopted, the gills are
discarded and all traces of them disappear, the respiration being
entirely effected by the lungs. This change, which also involves
changes in the vascular system and in the skin, is spoken of as
a metamorphosis, and it may occur when the creatures are still
very small, or it may be postponed till they have attained their
adult size, and have even laid eggs. Such is the case e.g., in a
large Salamander from Nebraska, Ambly stoma mavortium,
which attains the size of a Menobranch before it loses its gills.
It was thought at one time that our Necturus might be such a

HIGH SCHOOL ZOOLOGY. 91

larval form, but such is not the case. Another example of
arrested metamorphosis is the Mexican Axolotol. A few years
ago, this was only known to naturalists in its larval stage, but
it has been caused to undergo metamorphosis experimentally,
and has been found to do so naturally in some of the localities
in which it occurs.

Several Urodeles belonging to this division occur in our re-
gion ; they belong chiefly to the genera Amblystoma, Plethodon
and Diemyctylus. The largest of these, Ambly stoma punctatum,
the spotted Salamander, attains a length of six inches of which
two and one-half belong to the tail. The gills disappear when
the creature is two inches long, the colour is purplish black,
and each side of the back is ornamented with two rows of
bright yellow spots. Of the Plethodons, P. erythronotits, the
red-backed Salamander, Is perhaps the commonest ; this species
attains about half the size of the foregoing, but loses its gills
much earlier than the former does. It lives in moss and under
decayed trees where the eggs also are laid. Some allied species
are more aquatic in their habits. The newt, eft, or crimson-
spotted triton, Diemyctylus miniatus, is very common under
stones, generally near pools. Its dorsal surface is olive or red,
the ventral surface yellow or orange, but the sides are spotted
in both varieties with eye-like markings, red with a surround-
ing black rim.

15. Of the Old World forms allied to these, one of the most
striking is the European spotted Salamander (S. maculosa) (Fig.
68) which is black with golden yellow blotches. Certain cuta-
neous glands secrete a milky irritating fluid which appears to
be poisonous to small animals. It was thought in ancient times
to be most deadly poison, and to have the virtue of extinguish-
ing fire when thrown into its midst.

10. While many Urodela undergo a metamorphosis chiefly
characterised by the loss of the gills, the frogs and toads lose
at that period not only the gills, but the tail, whence their

HIGH SCHOOL ZOOLOGY.

/^&&^

m*^^'

m

Fig. 68 — Salamandra maculosa. (After Brehm).

ordinal name Anura. Any of the common species of frog will
serve as a type for the recognition of the peculiarities of the
order. As to the general form, the absence of the tail, and the
great development of the hind-legs along with the webbing of
the toes indicate what an entire change in the method of loco-
motion is to be observed in them. The short plump body also
strongly contrasts with that of the Urodela. Most of the forms
are somewhat brillantly coloured, and have the power of
altering their colour so as to suit it to the prevailing surrounding
hues. This is not the case in the common toad (Bufo lentigin-
osus) which remains concealed generally during the day time,
but it is very marked in the Wood and Green frogs (Rana tem-
poraries and clamitans), and in the Tree Toad (Hyla versicolor)
which, indeed, is very difficult to detect on trees or fences
owing to this faculty. The changes in colour are due to the pre-
sence of contractile pigment-cells in the skin which are con-
trolled by the nervous system.

17. It can easily be conceived that the change to a new
medium must be accompanied by changes in the skin. These
chiefly consist in the greater richness of glands which keep the
skin moist and allow it to discharge its subsidiary function as a

HIGH SCHOOL ZOOLOGY. 93

respiratory organ, and in the disappearance of those nerve-
endings which are only adapted for a watery medium. Accu-
mulations of cutaneous glands are best seen in the toad, behind
the ear (parotoid) and elsewhere ; they secrete an acrid fluid
which must be regarded in the light of a defensive provision.
Horny changes in the epidermis or bony plates in the skin,
which are common in the Reptiles, are rare in the Anura.

18. As in the Urodela, the skull of the Anura rests upon
the vertebral column by two condyles ; it presents in other
respects important differences, e.g. the girdle-like ossification of
the cartilage in the orbital region, and the great reduction of
the hyoidean apparatus brought about by the disappearance
of the gills. Again, the vertebral column is very much
shorter, and its end together with the pelvis have been much
modified, in such a way as to offer a solid basis of resistance to
the legs in leaping. The shoulder-girdle is very different from
that in the Menobranch, chiefly in the median meeting of the
precoracoids and coracoids, and the presence of an episternum in
front, and of a sternum behind that symphysis. In the skeleton
of the limbs, likewise, we find much change, chiefly in the fusion
of the bones of the fore-arm and lower leg, in the great length
of the proximal bones of the tarsus, and in the incompleteness
of its distal row.

19. In accordance with the gait of the Anura, the muscula-
ture of the hind-limb is extraordinarily developed, and the
muscles of the trunk are no longer the chief locomotive organs.
Apart from the fact that in the frog the brain is somewhat
shorter, its olfactory lobes fused, and the optic lobes larger, there
is little difference between the central nervous system in the
Urodela and Anura. The ear, however, presents a well-marked
difference, for there is a tympanic membrane, bounding on
the outside a tympanic cavity, which communicates with the
mouth by an Eustachian tube. This tube is comparable to the

94 HIGH SCHOOL ZOOLOGY.

spiracle of the sharks and Ganoids, and is closely related to the
internal ear even in these forms. A columella longer than that
in the Menobranch stretches between the tympanic membrane
and the fenestra ovalis.

20. As regards the intestinal apparatus, the Anura pre-
sent many differences from the TJrodeles. The tongue, which
is little developed in the latter, becomes in the former the
chief organ for securing the insects on which they feed, as it
is free behind and can be shot out with great rapidity. It
is only absent in two tropical forms, Aglossa. The males of
some species are furnished with air-sacs, which serve as resona-
tors to reinforce the sounds produced by the larynx, which is
better developed than in the Menobranch. Although the adult
Anura are carnivorous and their intestine is comparatively
short, yet the larvae or tadpoles have a very long coiled-up
intestine. They are omnivorous, but chiefly live on vegetable
substances which they gnaw with their temporary horny jaws.

21. It will be at once realized that the metamorphosis
of the Anura brings about greater changes both in the form of
the body and the habits of life than in the TJrodeles. The
period of development at which it occurs may be very different,
the tadpole phase being sometimes very brief and in other cases
much longer. It may in certain cases be retarded by external
conditions where it ordinarily occurs early. Most of the forms
lay their eggs in water, surrounded by a quantity of gelatinous
substance forming the frog's spawn, but other forms which have
not free access to water, adopt other plans. In one of the
Aglossa for instance, the Surinam toad — Pipa (Fig. 69), the
eggs are placed in enlarged cutaneous glands on the back of the
mother, where they are hatched out and pass through their tad-
pole-phase. The common toad, again, requires only very small
pools in which the larvse pass their short aquatic life.

HIGH SCHOOL ZOOLOGY.

95

Fig. 69.— Pipa Americana. (After Brehm).

Structurally the tadpoles (Fig. 70) differ from the adult chiefly
in the presence of the tail, the want of limbs and the nature of
the respiratory and circulatory organs. They possess adhesive
discs near the mouth by which they attach themselves to aquatic
plants and other objects for support. The first gills are
external, but these soon disappear, and give place to internal
gills on the four gill-arches ; these are concealed by a gill-cover,
which grows over them in such a way as to leave only a single
aperture on the left side. Underneath this gill-cover the fore
limbs are first budded out and the hind limbs make their ap-
pearance immediately afterwards ; both are fully formed before
the tail shrivels up. Eventually the gills disappear, and the
heart and vessels undergo such an alteration that the venous
blood is sent to the lungs and skin to be aerated and the arterial
blood to the body generally.

96

HIGH SCHOOL ZOOLOGY.

Fig. 70. — Stages in the Development of an European toad. (Pelobates).

o. the gelatinous spawn containing developing eggs, o'; a. a group of tadpoles adhering
to a weed ; b. one of these enlarged showing the external gills ; c. stage in which ex-
ternal gills are lost, the spiral intestine is represented ; in d, the hind, and in e, all four
limbs are developed, while the tail is shrivelled up in f amd lost entirely in g.

22. In III, 16, three genera of Anura are mentioned which
form the types of so many families of Anura. The Ranidae are
characterized by the great length of the hind limbs, by the
presence of teeth in the upper jaw, and by the smooth skin —
the Bufonidae on the other hand, have shorter legs, a warty
skin and no teeth, while the Hylidaa are specially marked out by
the adhesive disks with which the fingers and toes are provided,
and which permit the climbing habits of the genus. Two
species ©f Hyla, one of Bufo, and five of Rana occur in our
region. The largest of the latter is the bull frog (E. catesbyana)

HIGH SCHOOL ZOOLOGY.

97

one of the most completely aquatic species. R. clamitans, the
green or spring frog, rarely leaves the water for any distance,
while the wood frog R. temporaries var. sylvatica is found
among the fallen leaves of forests, with which its colour is as-
similated, while the two remaining species, R. palustris, and ha-
lecina are both found in marshy places and are more varie-
gated in colouration, for there are four or two rows of black
spots on the greenish ground of the back.

An interesting case of adaptation to an arboreal life is
offered by a species of Ranidaa from the Malay Archipelago —
Rhacophorus Reinhardtii — (Fig. 71) — in which the webs of
the toes are used as a parachute in leaping from tree to tree.

Fig. 71.— Rhacophorus Reinhardtii. (After Brehm;.

23. The remaining orders of Batrachia are only represented by fossils
from the coal measures and the overlying Permian and Triassic strata.
The teeth are generally complex in structure whence the name
Labyrintliodontia. In form they resembled the Salamanders, but some
attained a gigantic size, and others, such as those found by Sir W. Daw-

98

HIGH SCHOOL ZOOLOGY.

son in the hollows of fossil trees in the coal-measures of Nova Scotia,
were as small as many of our Salamanders. Many resembled the Ganoids
as to the skin-bones of the head, but the notochord was persistent
throughout life as in the Dipnoi.

Fig. 72.— Siphonops mexicanus. (After Brehm).

24. The remaining living order, the Gymnophiona, is inter-
esting, because it embraces forms which, through adoption of a
burrowing habit, have undergone the loss of limbs and eyes, and
have acquired a hardened skin provided with horny rings.
They are represented both in the tropics of the Old and New
Worlds (the most northern form is Siphonops mexicanus, Fig.
72.), and they appear to be most nearly allied to Amphiuma,
which they resemble in depositing necklace-like strings of eggs.

HIGH SCHOOL ZOOLOGY, 99

CHAPTER IV.

The Reptilia.

1. Our study of the Catfish and Menobranch has taught us
that in addition to the aquatic habits which these creatures
share, there are certain anatomical features in which they are
alike. The Classes Batrachia and Pisces are not separated from
each other by any gulf such as meets us when we advance to
the study of the Reptilia. It was possible to point out the
existence of living forms intermediate in many ways between
the Batrachians and Fishes, but we have no such living forms to
bridge over the gap between the Batrachia and the Reptiles.
Nor do we know any fossil remains which do so ; on the other
hand, the Reptiles and Birds, at first sight so entirely unlike
each other in structure as well as habits, are, nevertheless,
closely allied by fossil forms which present all the important
stages of transition between the two groups. Zoologists give
expression to these relationships by uniting the Classes Pisces
and Batrachia into a group Ichthyopsida, and the Classes Rep-
tilia and Aves into a group Sauropsida. The proof of the
reptilian affinities of the Birds we shall postpone until we have
studied the structure of some of our common Reptiles. In the
meantime it is necessary to remark that the two Classes Reptilia
and Aves are of very unequal rank, as far as the structural
characteristics which mark them out are regarded. The Birds
constitute a very homogeneous group, the different orders of
which are chiefly remarkable for structural features associated
with minor differences of habit, but the Reptiles are a very
heterogeneous group, and the various families, into which the
living orders of Chelonia (Turtles), Lacertilia (Lizards), Ophidia

100

HIGH SCHOOL ZOOLOGY.

(Snakes), and Crocodilia (Crocodiles) are divided, frequently
differ more from each other anatomically, than do the orders of
the Birds. The orders themselves, therefore, present still less
in common with each other, so that the study of a type of each
is necessary to enable the student to grasp the structure of the
whole Class. Much attention has been devoted of late to a
New Zealand. Lizard-like animal, Hatteria, because of all the
living Reptiles it is the most primitive form, and most nearly
allied to some of the oldest fossil representatives of the Class.
Some reference may afterwards be made to this interesting
species, but we are obliged to select a more accessible form as
an introduction to the group.

2. Although the Turtles in respect to their skeleton are really
a very highly-specialised group, yet we shall find in the soft
parts many structures which will remind us of the Urodela.

Fig. 73— Snapping Turtle. Chelydr a serpentina. £.
(After Brehm).

The common Snapper (Ghelydra serpentina, Fig. 73) one of
the least specialised, is a convenient starting-point for the study
of the others, but the following description will apply almost
equally well to the little painted turtle (Ghrysemys picta).

HIGH SCHOOL ZOOLOGY. 101

The most remarkable point in regard to the skin is the
development in it of certain bony plates, which, however, are
so closely related to the internal skeleton, as to be more properly
dealt with in connection therewith. In other respects we have
to notice here as well as in all the other Sauropsida the great
development of the horny layer of the epidermis, no longer
confined to the extent of one or two layers of cells, or locally
thickened here and there, but developed into the characteristic
clothing of scales, scutes, shields or feathers. In the Snapper
we distinguish two kinds of these epidermal appendages, the
regular shields which cover the dorsal and ventral surfaces
of the trunk, and the smaller and less regular scales and tuber-
cles of the rest of the surface. In addition to these are the
formidable claws with which the distal or ungual phalanges of
the digits are provided. Although all of these structures are
formed of horny epidermal cells, yet the underlying mucous
cells replace them from below as they are worn off above, and.
the corinm likewise partakes in their formation. The dorsal
surface has three rows of larger carinated shields (five unpaired
vertebral, and four paired costal) surrounded by twenty-five
smaller ones, of which eleven at each side are called marginal,
while that in front is nuchal, and the two behind caudal. These
shields are separated by very scanty connective-tissue from the
underlying bones of the exoskeleton. Similarly, on the ventral
surface there are six paired shields named from before back-
ward, gular, postgular, pectoral, abdominal, preanal and anal,
of which the abdominal are the largest. It is these large epi-
dermal shields, which in one of the marine turtles, furnish the
tortoise-shell of commerce. (Fig. 74). As in the other mem-
bers of the order, the jaws are provided with horny sheaths
like a parrot's beak instead of teeth, and the terminal hooks of
these are of considerable size in the Snapper.

After the epidermal shields have been removed, it is seen
that their outlines do not correspond to those of the bony

102

HIGH SCHOOL ZOOLOGY.

Fig. 74— Tortoise-shell Turtle. Eretmochelys imbricata. <&.

plates beneath. The latter belong to the exoskeleton and are
arranged in the form of a box, which shelters the greater part
of the trunk, and which is divisible into two parts, the dorsal
carapace, and the ventral plastron, connected laterally with
each other for but a short distance in this species. In the former
we recognise a median row, of which the foremost, the nuchal
plate, is the largest and is unconnected by bone with the verte-
bral column, while the eight neural plates which succeed it are
co-ossified with the spines of the underlying eight (second to
ninth) dorsal vertebrae, and the three pygal plates which term-
inate the median row, are again free from the vertebrae beneath.
Extending laterally from the neural plates are the eight pairs of
costals, which overlie the second to ninth ribs, and extend out-
ward for the greater part of the length of these ; however, the
free tips of the ribs alone are seen to join the bony marginal
plates. From this point they are not continued towards the
ventral middle line ; the bones of the plastron have, therefore,
no relation to them.

HIGH SCHOOL ZOOLOGY. 103

In contrast to the immobility of the dorsal region of the
vertebral column is the great mobility of the cervical and caudal
regions. Two vertebrae support by their ribs the ilia, and are
consequently spoken of as sacral. With the exception of the
mandible and hyoidean apparatus, all the bones of the skull are
intimately united, the quadrate is firmly connected with the
others, and two bones (which do not occur in the Ichthyopsida),
the quadratojugal and the jugal, unite it to the maxilla. The
hyoidean apparatus is interesting because it has undergone the
reduction which we would have anticipated in an animal where
there are no gills. The arches which persist serve for the origin
of the muscles of the tongue.

3. As to the appendicular skeleton it has many points of
resemblance to that of the Menobranch, the hands and feet are
even more primitive, and the shoulder girdle resembles it in the
free termination of the coracoids, but the pelvic girdle is some-
what more complicated, presenting a large perforation between
the pubis and ischium on each side.

4. The chief points in which the brain of the Snapper differs
from that of the Urodela is in the greater development of the
cerebral hemispheres and the cerebellum in contrast with the
other parts.

5. In the intestinal canal the absence of teeth and the great
length of the short intestine are noteworthy, while that we have
to do with an air-breathing Vertebrate is sufficiently evident from
the large size of the lungs. In most air-breathing animals the
change of the air in the lungs is aided by respiratory movements
of the thorax, but as the thorax here permits of no such move-
ments, this function is undertaken by the thin wall of the body-
cavity in front of and behind the bridges which join the cara-
pace and plastron. The circulatory system is also adapted to
the change of the m thod of breathing, for not only is the
blood returned from the iungs into a different chamber from

104 HIGH SCHOOL ZOOLOGY.

that returned from the body, but there is also a tendency
towards the sub-division of the ventricle, so that the blood
which has been aerated is kept towards one side of that
chamber, and sent chiefly towards the head.

6. In an important respect the Snapping Turtle resembles
the other Sauropsida and differs from most of the Ichthyopsida,
viz., the large size of the eggs, which is due to the large quantity
of food-yolk present. The eggs are like a bird's, except for the
less calcareous shell and the scantier white, and the embryo is
gradually developed in it at the expense of the yolk. The
period of oviposition is June, some twenty or thirty eggs of
the size of a pigeon's being then laid by the mother in a hole
scraped out by the hind feet, and not far from a stream or
pond. The sun's rays beating on the sandy soil generally
selected offer the requisite amount of heat for hatching the
eggs out about October.

7. Chelydra is the type of a family named from it which
occupies a central position in the order of the Chelonia, and it
is easy to proceed from it to the wholly aquatic turtles on the
one hand, and the wholly terrestrial forms on the other. At the
two extremes are forms which differ very materially from each
other in the adaptation of the form of the body to the sur-
roundings. The Marine turtles are very much depressed, their
feet are converted into flippers, and the carapace is not adapted
for the protection of the retracted head and limbs ; on the other
hand, the purely terrestrial forms have a very convex carapace
within which the head, tail, and limbs can be sheltered, and in
some forms (the box-turtles) the plastron is hinged in such a
way as to close effectually the anterior and posterior apertures
into the shell.

8. We may first proceed in the direction of the more aquatic forms,
of which the soft-shelled turtles, Trionychidse, are fresh- water animals.
There are two common species Amy da mutica and Aspidonectes spinifer,
abundant in streams opening into the great lakes from the South, and in

HIGH SCHOOL ZOOLOGY.

105

both the edge of the carapace, and the whole of the plastron are of
leathery consistence. These forms lie buried in mud and may remain
for hours under water ; their respiration is then effected by water
taken in and rejected through the nostrils, in such a way that the
mucous membrane of the pharynx, which is provided with vascular
papillae arranged on the arches of the visceral skeleton, is constantly
bathed with fresh water. This is an interesting point of contact with
the Urodela.

9. The feet of the Trionychidae are broadly webbed, but not converted
into flippers as they are in the marine turtles, the Chelonidse. In these
the anterior flippers are largest, and the claws are much reduced. One
of the genera, Dermatochelys, has a leathery skin in place of the horny
shields which are present in the other genera, the green or edible turtle
(Uhelonia mydas), and the Tortoise-shell turtle (Eretmochelys imbricata),
(Fig. 74), in which latter form the horny shields overlap each other.

10. Proceeding from Chelydra towards the turtles of more terrestrial
habit, in all of which the plastron is much more complete than it is in
that genus, we come first to the Cinosternidae in which the carapace
is more vaulted, although the feet are still webbed, the creatures living
for the most part in muddy ponds. The most northerly American form
is the Musk turtle (Aromochelys odoratus), the secretion from the
cutaneous glands of which has a somewhat offensive musky odour.
Closely allied are certain more southerly mud-turtles, which are able to
close the shells.

11. Most of our species
of turtles, however, be-
long to the Emydidse, all
of which are aquatic
when young, some like
the painted turtle ( Chry-
semys picta), and the
spotted turtle (Nanemys
guttata) throughout life,
while others like the
Wood turtle (Chelopus
insculptus) are found in
dry places away from
water. The most ter-
restrial of the family is the common Box-turtle (Cistudo carinata), in
which the plastron can be shut up over the retracted extremities. It

lives in sandy hills, and forms burrows into which it retreats during rain.
8

Fig. 75.— European Land-Tortoise.
(After Brehm).

Testudo graeca. |.

106

HIGH SCHOOL ZOOLOGY.

12. Finally the Testudinidse embrace the truly terrestrial tortoises
represented by one species in the Southern States, but occurring abund-
antly in the warmer parts of the Old and New Worlds. (Fig. 75).

13. The genus Hatteria (Fig. 76), referred to above is most
nearly related in its habits and form to the Lizards, Lacertilia,
but there are some respects in which its structure is much
more primitive ; e.g., its vertebrae are amphiccelous and its
pineal body (I. 36), presents more nearly the structure of an
eye than does that of any other living reptile. Unlike the
Lizards its quadrate bone is united firmly with the skull, and
by an arch below the eye with the maxilla.

Fig. 76. — Hatteria punctata, f.
(After Brehm).

14. In spite of the difference in habit between the extreme
forms of the Chelonian series, there is not so much difference in
external appearance as we meet with in the second order — the
Lacertilia. A few aquatic forms belonging to the Yaranidse,

HIGH SCHOOL ZOOLOGY. 107

like the large water-lizards of the Nile, do not exhibit any special
adaptation for locomotion in water. Most of the forms are
terrestrial in their habits while some are arboreal, and others
lead a subterranean life. In accordance with such differences
in the surroundings, we find great differences of external form.
The members of the order are especially abundant towards the
tropics, only two families being represented further north by
the Blue-tailed Skink {Eumeces quinquelineatus) and the Brown
Swift or Pine-tree lizard (Sceloporus undulatus). Both of
these lizards are of small size and very active creatures, the
last mentioned belonging to a large family the Iguanidse, which
embraces most of the New -World lizards. The forms which
lead an active arboreal life are generally compressed in shape,
while those which creep about in sandy places depending on
their colour for protection, like the Horned Toad of the Southern
States {Phrynosoma cornutum, Fig. 77), are depressed. Among

Fig. 77 — Horned Toad. Phrynosoma comutum.
(After Brehm).

the largest members of the family are the great Iguanas of the
Brazilian forests, which are alike remarkable for their size and
for the singular crests and combs with which the skin is adorned.
An old world family the Agamidae contains forms which

108 HIGH SCHOOL ZOOLOGY.

resemble in habit and appearance some of the Iguanidse.
Thus there is an Australian species (Moloch) in which the skin,
as in the Horned Toad bristles all over with spines, while
again there are many active arboreal forms. Among the
most interesting of these is the Flying Lizard (Draco volitans)
(Fig. 78), a curious little Indian form in which the foremost

Fig, 78— Flying Lizard. Draco volitans.

false ribs, which do not reach the breast-bone, project straight
out from the body, and have the skin stretched between them
in such a way as to form a serviceable flying membrane, which
enables them to drop obliquely through the air in their hunt
after the insects on which they live.

15. Scarcely less well adapted for an arboreal life are the
Chameleons and the Geckos, the former confined to the Old
"World, the latter found in the tropics of both Old and New
Worlds. In the former the feet are shaped something like
those of a climbing bird, the five toes being arranged in opposite
groups of twos and threes, the better to grasp the branches on
which they perch, while in the latter (Fig. 79), the toes are
provided with adhesive discs, which enable them to climb up
vertical surfaces such as walls and rocks. Both families are
insect-eaters, but the Chameleons secure their prey by shooting
out the long worm-like tongue, while the Geckos spring upon
theirs from a distance. While the Chameleons are strictly
arboreal forms and are protected in the foliage in which they
live by assimilating their colour to that, the Geckos are also to

HIGH SCHOOL ZOOLOGY.

109

^

Mill B»n|ilwMrf , ?r%

Fig. 79— Geckos. Platydactylus mauritanicus. |.
(After Brehm).

be found in treeless districts, running over rocks and living in
inhabited houses.

16. In several families of Lacertilia on the other hand we
meet with a form of body adapted for creeping rapidly through
underbrush and underneath stones, as well as for burrowing in
the ground. In such creatures the body is cylindrical, almost
snake-like, the limbs being either rudimentary or entirely
absent. Generally the hind limbs are indicated even when
the fore are absent, but in one Mexican genus (Chirotes),
it is the latter which are alone present. In the

110

HIGH SCHOOL ZOOLOGY.

Snake of the Southern States, Ophiosaurus ventralis, as
in the European Blind-worm, Anguis fragilis, (Fig. 80),
there are no limbs; both of these are extremely fragile

Fig. 80— European Blind-worm. Anguis fragilis. \.
(After Brehm).

creatures, the tail being readily cast off in violent efforts to
escape from a capturer. The most completely adapted for an
underground life is the Amphisbaena, (Fig. 81), of South

m

'U.-A

Fig. 81— Amphisbaena alba. J.
fter Brehm).

America. This curious lizard is cylindrical in form, the head
and tail both abruptly rounded off; they live in ants' nests
and feed on their larvae.

HIGH SCHOOL ZOOLOGY. Ill

17. From such footless lizards to the true snakes, Ophidia, the
transition is sufficiently easy. Among the latter, indeed, are
some forms which retain rudimentary hind limbs ; such are the
Pythons, Boa Constrictors and Anacondas of the Old and New
World ; again there are other smaller forms like the blind snake
(Typhlops), which show the burrowing habit and the external
form of the Amphisbsena, but lack the peculiar arrangement of
the jaws which we see in the typical snake. All our Ophidia,
however, belong to two families which exhibit considerable dif-
ference from the structure of any lizard. Not only are the fore
and hind limbs absent, but there is no trace of the girdles sup-
porting them, nor of a sternum. Locomotion, being effected
by the ends of the ribs and by shields of the ventral surface
whose hinder edges are free, presents a great contrast to the
clumsier movements of the footless lizards. In the latter, certain
of the organs are affected by the length of the body, the ten-
dency being for paired organs like the lungs and oviducts to
become unequal in size, one of thein assuming the function of
both, but this tendency is carried further in the snake, so that
one lung or one oviduct may alone be present.

18. The absence of the pectoral and pelvic girdles makes it
impossible to recognise any but the trunk and caudal regions of
the vertebral column. A neck may be present in the form of a
constricted part of the trunk behind the head, as in the Rattle-
snake, but its vertebras do nob differ from those of the region
behind it. So heterogeneous an order is that of the lizards, that
we meet with the greatest variety in the epidermal coverings of
the body, but the Ophidia constitute just as homogeneous a
group on the other hand ; nevertheless, in spite of the apparent
similarity of the scales and shields, slight differences in the form
and arrangement of these are used by system atists in the
diagnoses of the species. (Fig. 82). The epidermis is cast off
several times a year in the form of a slough, the first moult
taking place immediately after the escape from winter quarters.

112 HIGH SCHOOL ZOOLOGY.

fig. 88 -Scales of the head in Coluber (Bascanium) constrictor.

(After Garman.)

1, Rostral. 2, Nasals. 8, Loreals. 4, Preoculars or Antorbitals. 5, Postoculars oi
Postorbitala 6, Temporals. 7, Internasals. 8, Prefontals. 9, Frontal, 10, Supracili-
anes or Supraoculars. 11, Parietals. 12, Occipitals. 13, Labials. 14, Infralabials. (Be-
tween the infralabials are the submentals, and clothing the tip of the lower jaw the
mental). 18, Ventrals. 19, Dorsals.

19. One of the chief peculiarities of the Ophidia is their
method of securing their prey, and bolting it undivided. Some
of the larger forms are dependent entirely on the flexibility of
the vertebral column and the power of the trunk and intercostal
muscles for strangling their prey, but the smaller snakes either
seize their victims with their teeth, or first inflict a fatal wound
with their poison-fangs. The poisonous snakes must be re-
garded as the most specialized of the Ophidia, for the teeth are
not only reduced in number in comparison with the harmless
forms (where they may be as numerous as in the Teleosts), but
the poison-fangs (which are confined to the maxillaries), are
either provided with a groove on the anterior surface, or with a
canal connected with the duct of the poison-gland, — a special-
ized part of the glands of the upper lip, which is compressed
by the muscles which close the jaws. That the snakes may be
enabled to swallow their booty whole, a process which is often
a very gradual one, the parts of the mouth are provided with
extraordinary mobility. The pterygo-palatine bar is capable of
greater movement than is even possible in the fishes, where it
will be remembered its bones are not incorporated with the
cranium, and not only is the quadrate bone freely moveable,
but the squamosal which supports it, is hinged to the skull.

HIGH SCHOOL ZOOLOGY, 113

from which it projects backwards. Thus the articulation, of
the lower jaw, which is composed of two movable halves, is
situated behind the head, and the gape is consequently ex-
tremely wide.

20. The Ophiclia are destitute of the Eustachian tubes and
tympanic cavities, the outer ends of the columella merely
abutting against the quadrates.

Most of the snakes lay eggs, which are hatched without the
aid of the mother, but some of the venomous snakes, as well as
fresh-water forms, bring forth their young alive, and these are
in certain instances taken care of by the mother.

21. Apart from the narrow-mouthed Typhlops and its allies,
and the Pythons, Boas, etc., with rudimentary hind-limbs, the
Ophidia fall into three groups, the extremes of which are
formed by the poisonous rattle-snakes on the one hand with
few canaliculate poison-fangs, and the harmless Colubridsa with
numerous non-perforated teeth, on the other, while the various
poisonous snakes with grooved teeth, like the brilliantly-coloured
-Bead-snake of the Southern States (Maps), the spectacled snake
of India (JVaja), and the flat-tailed sea-snakes of tropical seas
(Hydrophis), occupy an intermediate position. In this region
only the extreme forms are represented, the Crotalidse and
the Colubridse — the former embracing the rattlesnakes and
copperheads, the latter all our numerous harmless snakes.

22. Crotalus horridus, the banded rattlesnake, is marked by the head
being covered with scales instead of regular shields, and by its alternate
bands of two shades of brown. As in all the more venomous snakes the
head is sharply marked off from the body by a neck. The movements
are much more sluggish than in the Colubridse, the greater agility of
which compensates them for the absence of the peculiar weapons of
the rattlesnake. One of the most characteristic features of the genus is
the rattle formed of singular epidermal scales, the function of which has
been much discussed. Observers are not agreed whether it is used to
attract prey or to frighten away enemies. It is possibly useful for both

114 HIGH SCHOOL ZOOLOGY.

purposes. Snakes which are destitute of a rattle have been observed to
make a rustling noise with the tail, and it is interesting in considering
the origin of the rattle to recognize that each successive ring is merely
the retained slough of the tip of the tail.

By the absence of a rattle, the presence of cephalic shields, and the
smaller size, the Copperheads, Ancistrodon contortrix, are readily dis-
tinguished from the Rattlesnakes, which they resemble, however, in
being very venomous. They are found in less rocky ground than the
foregoing, are somewhat more active in their habits, but seek similar
prey, viz., small animals, birds and frogs.

Of the Colubridse the Garter Snake, Eutcenia slrtalis, is certainly the
commonest. Its dorsal scales are carinated, and arranged in nineteen
rows, while those of the ventral surface of the tail are undivided. An
allied species, E. saurita, the Swift Garter Snake, is much slenderer,
and has a longer tail.

The Garter Snakes affect damp swampy places, take readily to water,
and are gregarious in their winter quarters. They are viviparous like
most aquatic snakes. The commonest Water Snake is Tropidonotus
sipedon, which is to be seen basking on the shores of streams, to which
it takes when startled. Another common form is Storeria Dekayi, the
Little Brown Snake. It is also aquatic and insectivorous in its habits ;
its dull colours present a strong contrast to the bright green of the Grass
Snake, Cyclophis vernalis, a form which lives in marshes, and attains a
length of eighteen inches. Two larger species, the Black Snake, Bas-
canium constrictor, and the Fox Snake, Coluber mdplnus, prey upon
larger animals such as mice and frogs, and attack birds' nests. Both of
these species attain a length of five or six feet. The one is to be recog-
nized by its uniform black colour, while the other is light brown with
darker blotches. Finally the Milk Snake may be mentioned, Ophibolus
triangulus, a whitish snake with oval brown blotches edged with 1 lack,
found in dry situations, and visiting dairies for the milk ; the Ring-
necked Snake, Dladophis punctatus, with its characteristic yellow ring,
and lastly the Hog-nosed Snake, Heterodon platyrhinus, a peculiar form
generally supposed to be venomous, which has the habit of distending
its neck with air so as to look formidable, and then emitting the air
with a hissing sound, whence it is also called Blowing Viper. In the
poisonous genus Naja, a similar formidable appearance is secured by the
stretching out of the foremost free ribs at right angles to the vertebral
column, so that the neck is converted into a flattened disc.

HIGH SCHOOL ZOOLOGY.

115

23. The fourth and last order of living Reptiles is that of the
Crocodilia, aquatic forms of large size which are found in tropi-
cal rivers over the whole world. There are three families
represented by the Gavial of the Ganges (Fig. 83), characterized

Fig. 83.— Gavialis gangeticus. (After Brehm.)
by its very long snout, the Crocodile of the Nile and the Alli-
gator of the Mississippi. Most of them are fish-eating forms, but
many of them lie in wait for the smaller Mammalia when they
come to drink. Their aquatic habit is associated with a power-
ful compressed tail, and completely or incompletely webbed
toes, but the legs are, nevertheless, strong enough to enable
them to leave one pond and drag themselves to another. As in
the other Reptiles, the horny epidermal covering is well de-
veloped and characteristic, but there exist also in the cutis bony

116 HIGH SCHOOL ZOOLOGY.

shields on the back and behind the breast bone, which encase
the creatures in an almost continuous coat of mail. Important
differences from the Lizards exist in the endoskeleton ; the
great elongation of the skull, e.g., with the formidable teeth
lodged in sockets, the form of the nasal cavity, with the anterior
nostrils at the tip of the snout and the posterior far back in the
mouth, the intimate union of all the cranial and facial bones
with each other, etc. Many peculiarities of the other organs
point to a greater specialisation than exists in the other Reptiles,
thus the brain is of a higher type, and the heart is subdivided
into four compartments, although there is still a certain mixture
of the venous and arterial blood immediately outside it. The
order is oviparous like most Reptiles, the eggs, which are very
fragile from the small percentage of lime in the shell, being laid
in the sandy banks of the streams in which they live.

22. Although the Crocodilia hardly number more than twenty
species at the present day, yet the Fossil species are far more nu-
merous than is the case in any other of the four orders of living

Fig. 84— Restoration of Plesiosaurus. £g.
Reptiles. The earliest of them had amphicoeJous vertebra, and
a much more complete exoskeleton than the living Crocodiles,
probably for protection against the gigantic aquatic Reptiles

HIGH SCHOOL ZOOLOGY.

117

which inhabited the seas along with them. These arrange
themselves under several orders of which the Sauropterygia
(Plesiosauria) and the Ichthyoptergia [Ichthyosauria) are the
best known. To the former (Fig. 84) belonged huge forms from
10-50 feet in length, with nippers something like a seal's, and
an extremely long swan-like neck, which must have allowed
great freedom of movement to the head with its formidable
teeth. To the latter belonged short-necked forms resembling
in shape the whales of the present day, but provided with, a
long and powerfully toothed snout. (Fig. 85).

Fig. 85— Restoration of Ichthyosaurus, ifo.
25. Among the fossil orders are likewise forms which attained
a huge size, whose limbs, more lizard-like in form (Sauropoda),
attest to a terrestrial or amphibious life, but whose teeth indicate
that they were herbivorous animals feeding either on aquatic
or marsh plants or on the forest vegetation. (Fig. 86.) Some

Fig. 86— Restoration of Brontosaurus. ?fej.
(After Marsh).

of them (Atlantosaurus) measured 100 feet in length by 30 in
height, the locomotion of such enormous masses being only
rendered possible by the fact that the skeleton was extremely
lipht, the bones being filled with air. The Sauropoda were
-Without the protection of an exoskeleton, whereas Stego

1 18 HIGH SCHOOL ZOOLOGY.

saurus had bony shields in the skin and projecting horns from
the back which must have afforded a very complete defensive
armour. This genus also is interesting from the fact that the
fore legs were shorter than the hind, and consequently that the
latter along with the tail supported the weight of the body. A
transition is thus afforded to the Ornithopoda or bird-footed
Dinosaurs, a remarkable group, of which the best known is the
genus Iguanodon of the Cretaceous period. (Fig. 87.) Recent

Fig. 87— Skeleton of Iguanodon in the Brussels Museum, ^j.
discoveries in Belgium have disclosed complete skeletons of this
reptile, which is characterised chiefly by the strong bird-like
three-toed legs, the short fore legs used only for prehension, the
lizard-like tail and the compressed body. The foot prints of this
Iguanodon, which are also preserved, show that its gait was
erect, and this is confirmed by examination of the sacral region
of the vertebral column, which is formed of five or six united
vertebrae, evidently for the purpose of transferring the weight of
the body to the hind legs. The Iguanodon was herbivorous, but
there were carnivorous Dinosauria likewise, some like Compso-
gnathus (Fig. 88) of such small dimensions that they hardly

HIGH SCHOOL ZOOLOGY.

119

deserve the ordinal name,
others, like Megalosaurus, rival-
ling the largest herbivorous
forms in size. Many of these
carnivorous forms present fea-
tures in their limbs and teeth
which remind us of the carni-
vorous mammals, but the
Compsognathus had an erect
gait like the Iguanodon.

26. In many respects the Ig-
uanodon and its allies resemble
the Ostriches, and, indeed, as we
shall see there are fossil toothed
birds which help to fill up the
gap between them.

Fig. 88— Restoration o Compsognathus. $.

So far the fossil reptiles we have considered have been either
aquatic or terrestrial forms ; some of the latter indeed walked

Pig. 89- -Restoration of Pterodactyl. §.

120

HIGH SCHOOL ZOOLOGY.

erect, their forelegs being used for prehensile purposes. "We
now come to certain forms which lived an aerial life, being pro-
vided with organs of flight of a character peculiar to themselves*
In this order, the Pterosauria, (Fig. 89) the limbs were approxi-
mately of the same size, but the little finger of the anterior
extremity was enormously long and strong compared with the
others. It had four joints, and between it, the arms and the side
of the body, a web of skin was stretched out, somewhat similar
to the web between a bat's fingers. Some of them (Fig. 90)

Fig. 90— Restoration of Rhamphorhynchus phyllurus. (Marsh). $.

had a long tail terminating i i a rudder-like membrane supported
by the spines of the terminal vertebrae. But none of them had
anything similar to the plumage of the birds, and we shall
afterwards see that the skeleton of the bird's wing is constructed
on quite a different plan from that of the Pterosaurian. Al-
though many members of this group were small, others attained
a gigantic size, one found in Kansas having a stretch of some
twenty feet.

HIGH SCHOOL ZOOLOGY. 121

CHAPTER V,

The Birds.

1. From what we learned in last chapter it is neither the
power of flight nor the supporting of the body by the hind
limbs which constitutes a bird, for both these characteristics
were present in certain fossil reptiles. It is the peculiar epider-
mal clothing of feathers, which we must regard as marking off
the birds from the flying reptiles to which they are allied.
Yet there is not so much difference between the reptilian scales
and the avian feathers as might at first sight appear. If we
watch the development of the feathers in a bird, we may see
that they arise at first very much like scales, along regular
tracts, and that they are simply thickenings of the epidermis
over papillae of the cutis. But as the feather is developed it is
retracted into a follicle in the skin, and the epidermis gives rise
to the feather proper, the dried-up cutis-papilla to the pith.

2. In most birds we distinguish two different elements in
the plumage, the feathers proper or contour-feathers and quills,
and the down-feathers; but in certain birds destitute of the
power of flight down-feathers alone are present. Both kinds
resemble each other in having a quill by which they are in-
serted into the feather-follicle, a shaft, and a vane which is
composed of two rows of barbs, each provided with projecting
barbules. If the barbules are so arranged that those on con-
tiguous barbs interlock with each other, then we have a contour-
feather, or if it is of special use in flight, is a quill-feather, but
if the barbules are soft, and do not interlock, we have the
down-feather. It is obvious that a creature only possessed
of the latter cannot fly ; the interlocking of the barbules is neces-

9

122

HIGH SCHOOL ZOOLOGY.

sary to give to the feather the requisite strength to encounter
the resistance of- the air. The feathers, however, are not to be
merely regarded as organs of flight, but as a warm clothing for
the body, necessary to prevent the great loss of heat which
would otherwise attend the quick flight and rapid change of air
round their owners.

3. A great many technical terms are necessary in systematic
ornithological descriptions ; some of these may be studied from

Fig. 91— To illustrate the topography and the plumage of the Sparrow.
(Passer domesticus). (After Thome).

1, Upper mandible with nostril ; 2, lower mandible ; 3, culmen ; 4, gonys ; 5, lore in
from of the eye ; 6, forehead or frons; 7, crown or vertex; 8, occiput; 9, malar or cheek
region; 10. throat; 11, breast; 12, abdomen; 13, back; 14, rump with the upper tail
coverts ; 15, rectrices or tail feathers ; 16, tarsus ; 17, primaries ; 18, secondary and
tertiary remiges, or wing quills ; 19, alula or bastard wing ; 20, greater ; 21, median and
lesser wing coverts.

4. Premising then that the plumage is to be regarded as
the essential characteristic of a bird, let us see, in continuation
of the subject of the close of the last chapter, how early
the remains of true birds are to be met with in the geo-
logical history of the earth. Fortunately the feathers aro
well known in the earliest fossil bird which has been fourd,

High school zoology.

123

because the remains are preserved in a very fine textured stone of
Upper J urassic, Age found at Solenhofen in Germany, and used for
lithographic purposes. The last found of the two specimens is very
perfect, the carcase of the bird having been bedded in the fine sedi-
ment of the sea-shore, in such a position that all the parts are very
plain. From these we recognise that the Archceopleryx, as it is

called, is in many res-
pects more like a reptile
than a true bird, especi-
ally so in the fact of its
tail being formed of a

large number of distinct
vertebrae, so that the
ordinal name Saururse,
was formed for it on
this account. (Fig. 92).
No other bird-remains
hitherto found show
this peculiarity, so that
Archseopteryx stands
alone with its lizard-
like tail, while all other
birds, living and fossil
show some union of the
caudal vertebrae. In
respect to its plumage and organs of flight, however, Arch-
seopteryx is a true bird, and not a flying lizard Two other
fossil birds have been found in the Cretaceous rocks of the
Western States which share with Archseopteryx another rep-
tilian character, that of toothed jaws, but in other respects
more closely resemble the birds of the present day Of these
two genera, one, Hesperornis, appears to have been destitute of the
power of flight, because the bones of the anterior extremity are
much reduced and there is no keel upon the sternum, such as

Fig. 92— Berlin specimen of Archseopteryx, £,

with leg from London specimen.
UF. Tibia. MP. Tarso-metatarse. Z. The toes.

124 HIGH SCHOOL ZOOLOGY.

there is in all birds which have that power, while the other,
Ichthyornisy had a wing fashioned in the same way as the great
majority of our birds, necessitating a keel upon the sternum.
Thus at a very early period of the history of the birds, the
distinction which we draw between those with a raft-like and
those with a keeled sternum (the Ratitae and the Carinatse)
was already established. But this distinction is of a compara-
tively unimportant character, because it would appear that at
various periods of the world's history, members of different
families of birds have lost the power of flight (and along with
this, to a greater or less degree, the keel on the sternum,) by
taking exclusively to some other method of locomotion, such as
swimming or running. Nevertheless, when we realize how the
structure of a bird is connected with its power of flight, we
shall more easily understand how the absence of that power
may produce a superficial resemblance.

5. If we study, then, the structure of any typical carinate
bird, we shall soon learn that apart from the plumage there are
many other features which are evidently adapted to its mode of
locomotion and habits of life, and that the whole structure of
the body is, indeed, modified in connection therewith. Although
the common domestic fowl belongs to a family of poor fliers, yet
a knowledge of its structure forms a key to that of all the
Carinatse. Numerous races are known but all belong to a
single species, Gallus domesticus, the nearest wild ally of which is
the Gallus bankiva of India. With the pheasants, pea-fowl and
guinea-fowl they form the family Phasianidse of the order
Gallinacei, all of the birds included under which (prairie-fowl,
partridge, turkey, etc.,) are indifferent fliers, seeking their food
on the ground, partly by scraping, for which purpose the feet
are provided with strong claws.

6. Let us now proceed to examine the skeleton of a fowl with
the object of seeing in what respects it differs from that of the
fossil birds and reptiles The vertebral column presents the five

HIGH SCHOOL ZOOLOGY.

125

Fig. 93.— Skeleton of Fowl.

cv. cervical vertebrae ; h. humerus ; r, u. radius and ulna ; ca. carpus £1. pollex ; II
index ; III. middle finger ; co. coracoid : sc. scapula, cl. clavicle ; cs. crest of sternum;
s'. one of the processes of the body of the sternum ; it ilium ; .s. ischium ; pu pubis;
py. pygostyle; f. femur; t. tibia and fibula ; tin. tarso metatarse.

126 HIGH SCHOOL ZOOLOGY.

regions present in all the higher Vertebrates ; of these, the cervi-
cal contains thirteen vertebrae, and it alone retains any freedom
of movement between the individual bones, for the vertebrae of
the trunk and the greater part of the tail are for the most part
so united by bone that no such movement is possible. The last
few vertebrae are, however, movable, and the terminal one, the so-
called pygostyle (which is really formed by the fusion of several
centra) serves to support the tail-feathers. The chief charac-
teristic, then, of the bird's vertebral column is that the iliac bones,
instead of being united with a few sacral vertebrae as in the
reptiles, have acquired a union with the vertebrae in front and
behind these, so that the whole region is stiffened into one mass.
It is obvious that such an arrangement is well calculated to
transmit the whole weight of the body to the hind limbs.

A conspicuous difference between the higher and the lower Vetebrates
is in the nature of the union between the skull and the vertebral column.
In the fish the basi-occipital closely resembles and forms a part of a
series with the vertebral centra ; in the Amphibian, on the other hand,
the ex-occipitals form two surfaces of contact (occipital condyles) with
the vertebral column, but in the higher Vertebrates greater freedom
of movement is conferred upon the head by the specialisation of the first
two vertebrae for this purpose. The anterior or atlas possesses surfaces
for receiving the one (Sauropsida) or two (Mammalia) occipital condyles,
and it itself rotates on a pivot (the odontoid process — which is really
part of the centrum of the Atlas — ) attached to the centrum of the
second vertebra or axis.

As for the skull, the chief thing to notice is the early fusion of
its component parts in such a way as to make it impossible to
distinguish the limits between the cranial bones, although the
sutures between those of the face are easily seen. The premax-
illae are of large size, and chiefly support the upper beak, (which
is movable 10 a certain extent on the skull behind), while the
maxillae are insignificant and are united to the outer surface of
the movable quadrate by a slender bar formed of the jugal and
quadrato-jugal. The quadrate moves partly on the skull and

HIGH SCHOOL ZOOLOGY. 127

partly on the pterygopalatine bar, and it supports the man-
dible, which in the adult is formed of a single piece inclosed in
the lower horny beak.

It is to be expected that the possession of the power of flight
should be associated with alteration of those parts of the
skeleton concerned, so that in addition to the rigidity of the
thorax conferred by the immovability of the dorsal vertebrae,
it is not surprising to find other conditions adapted to offer a
solid basis of resistance to the stroke of the wing; and protec-
tion to the delicate parts contained within the thorax. So the
true ribs are not only bound to each other by uncinate pro-
cesses, but their sternal ends, instead of being cartilaginous,
are bony. Again, the sternum does not only afford protection
to the thoracic organs by its great size, but by its keel offers
a large surface for the attachment of the muscles of flight.
Although the scapula is small, the ventral parts of the shoulder-
girdle are both strong and connected with the sternum ;
especially is this true of the coracoid, through which the strain
of the wing stroke is chiefly transmitted to the trunk. The
chief peculiarity of the humerus is its strong crest for the
insertion of the muscles of flight, while the ulna differs from
the radius in its strong curvature, the convexity of which is
roughened by the attachments of the secondaries. It is the
wrist and hand that are most peculiar, however, for we see only
two proximal carpals, the distal carpals being fused with the
three metacarpals into one perforated bone, while the three
fingers are independent. The second finger is the most im-
portant, the third being rudimentary, while the first, which
supports the spurious wing when it is present, and like the
second is sometimes provided with a claw, is also short.

Reference was made to the singular method of union of the
pelvis to the trunk; the other parts of the pelvic arch are
chiefly remarkable for their backward direction and for their
not meeting in a symphysis, except in some of the more reptile-

128 HIGH SCHOOL ZOOLOGY.

like Ratitse. Another peculiarity of the hinder extremity is
that only the proximal end of the fibula is present, and that
the ankle joint, as in many reptiles, is situated between the
proximal and the distal rows of tarsal bones, the former of
which becomes fused with the tibia, into a tibio-tarsus, while
the latter and the metacarpals of the second, third and fourth
toes become fused into one tarso-metatarse. When the first
toe is present, its metatarsal is generally rudimentary, but it
has two joints, while the second toe has three, the third four,
and the fourth five. The spur of the cock is simply a bony ex-
crescence attached to the metatarsus.

7. It is to be expected that the greatest peculiarities of the
muscular system of the birds should be connected with their
mode of locomotion. From what has been said above, it will
be gathered that the great muscles of flight take their origin
from the sternum, and thus the centre of gravity of the body is
shifted towards the most favourable position for flight. Not
only the depressor of the wing, but also its elevator muscle
arise from the sternum, the necessary change in the direction of
the latter being acquired by its tendon passing through a pulley,
at the junction of the three bones of the shoulder-girdle, to its
insertion in the upper surface of the humerus. In reptiles and
mammals where the full number of fingers is present, and the
joints of these are freely movable upon each other and on the
wrist hones, muscles are necessary for carrying out these move-
ments, but the consolidation in the region of the hand of the
bird dispenses with the necessity for these and therefore
the chief muscles of the fore limbs are in its proximal end
near the body. The same is true of the hinder extremity,
tendons only being continued into the distal end to carry out
the ^novements of the toes. Thus the great muscles of the
limbs are likewise situated in a favourable position of the body
for flight. Cutaneous muscles, chiefly inserted into the feathers

HIGH SCHOOL ZOOLOGY. 129

and destined for shaking the plumage, attain a greater develop-
ment in the birds than they do in the lower forms.

8. A great advance is to be seen in the brain of a bird as
compared with that of any reptile, for not only is the cere-
brum much larger, but the cerebellum is so also, with the result
that the optic lobes are thrust aside right and left towards the
base of the brain. The surface of the cerebrum is smooth, but
that of the cerebellum is much folded so that the white matter
is arranged in a tree-like fashion in its interior. Of the senses,
sigthis decidedly the most acute ; the birds of prey especially are
gifted with extraordinary powers of vision, and in association
therewith the bulb of the eye has a very different shape from
the globular one present in other Vertebrates. Its principal
axis is much elongated, the posterior part of the bulb being a seg-
ment of a sphere, while the anterior is drawn out in a tubular
fashion. As in some of the reptiles, the sclerotic coat has a
circlet of bony plates formed in it. Hearing is also more acute
than in the reptiles ; the tympanic membrane is situated at the
bottom of a short external auditory passage (surrounded by
special "auricular" feathers) and the Eustachian tubes con-
verge to a common aperture in the palate.

9. Although organs both of touch and taste are present in
the mouth-cavity of the bird, yet the tongue is generally clad
to a great extent with horn, which varies in shape in different
species. The most constant peculiarity of the oesophagus is the
presence of a crop, which may be a projection from one side, as
in the fowl (Fig. 94), or from both, as in the pigeon. The
stomach is divided into a smaller glandular cardiac end, the
proventriculus, and a larger muscular pyloric end, the gizzard.
In the latter the muscular coat is very thick in two places, and
the epithelial lining is converted into horny pads, which serve
for the grinding of the food in the granivorous birds. As a
compensation for small salivary glands, the pancreas is large,
and the length of the intestinal surface is increased by two

130

HIGH SCHOOL ZOOLOGY.

cceca, which open into the anterior end of the large intestine.

10. Certainly the most
remarkable feature about
the respiratory system of
birds is the development
of air-sacs, which receive
their air from the lungs;
and are situated partly
among the viscera of the
body-cavity, partly be-
tween the muscles, and
underneath the skin of
the body, and finally
within the bones, dis-
placing the marrow in
these. The function of
these air-sacs is not con-
fined to supplementing
the size of the lungs,
(although a certain inter-
change of gases between
the blood and the con-
tents of the air-sacs must
take place), but they like-
wise serve to render the
body specifically lighter
(especially as the bodily temperature is high), and thus more
adapted for flight. As the bird's locomotion involves much
muscular exertion, both the respiratory and circulatory systems
are more perfect than in the reptiles, the presence of four
chambers in the heart, allowing the complete separation of the
blood which has been returned for aeration, from that which is
sent out by the heart to the system.

11. In the lower Vertebrates the voice is little developed,

Fig. 94— Viscera of the Fowl, (after Brandt).

oe. oesophagus; ig, crop; tr, trachea; m, muscle;
la, syrinx ; p, lun^; c, heart; h, liver; dh, hepatic
duct; vf, gall-bladder ; dch, bile-duct; pv.proven-
triculus; sp, spleen; v, gizzard; d, duodenum;
pa, pancreas; i, small intestine; coe, its cceca;
fo, egg-follicle burst ; o, eggs ; od, oviduct part-
ly slit open containing a mature egg, o'-; cl, clo-
aca ; Bz, Bursa Fabrieii.

HIGH SCHOOL ZOOLOGY. 131

but in the birds, especially in the song-birds and parrots, it is not
only of considerable range, but also capable of modulation. The
larynx, which is the organ of voice in the other Vertebrates, is
here in the background, for the notes of the song-bird are pro-
duced lower down in the wind-pipe, at the point where it divides
into the two bronchi. Here the " syrinx " is situated, in the
formation of which, both membranes capable of vibration, and
resonant dilatations capable of reinforcing the sounds produced
by these, take part.

12. The kidneys in the birds are not so elongated as in the
reptiles, and are moulded into the large and complex sacrum.

Only one oviduct, the left, is present ; the number of eggs laid
is very different in different species, but approximately constant
in the same species. The size is not always directly propor-
tionate to the size of the bird, for the chicks escape from the
egg (by the agency of a temporary tooth on the upper beak) at
very different periods of their development. Of the various
orders of Carinate birds, those which are the more primitive
escape from the egg in a condition to fend for themselves (aves
precoces), while the young of the higher orders required to be
looked after by the parents for some time after they are hatched,
their escape taking place at a much less developed phase (aves
altrices).

13. The egg of the fowl owes its large size chiefly to the food-yolk,
which is associated with the germinal yolk (1,66). The yolk is, never-
theless, a single cell bounded by a wall, the vitelline membrane. After
bursting through its capsule in the ovary (Fig. 94), it escapes into the
ccelom, and is received by the open mouth of the oviduct, the walls of
which are provided with glands, which secrete the albumen or white,
and with muscular layers, which propel it in a spiral direction (involving
the formation of the ropy parts of the white) towards the lower end of
the tube, where the shell -glands secrete the shell. When the egg is
laid, it has already undergone some of the stages of segmentation, the
white patch upon the surface being formed of a layer of cells (the
blastoderm), destined to grow into the body of the chick. The process
of incubation requires twenty -one days, and it can be carried out

132 HIGH SCHOOL ZOOLOGY.

artificially, if fresh air and moisture, as well as the proper temperature
— 104° F. — be afforded to the eggs.

14. Having examined the structure of the fowl as a con-
venient carinate type, let us now see in what respects Archse-
opteryx and the Ratitae differ from it. As far as the plumage
is concerned, Archaeopteryx approaches the Fowl more closely
than do the Ratitae, for in the latter the feathers are mere
downs, while in the former quill-feathers were present, and
probably also fine contour-feathers, although the impressions of
these have not been preserved. The quill-feathers were at-
tached to the ulnar side of the hand and fore-arm, round the
neck, to the leg as far as the tarsal joint, and in" a single series
along each side of the long tail. That is really the most im-
portant peculiarity of the fossil, for instead of the short tail of
the Fowl, there were twenty independent vertebrae, each with a
quill-feather attached right and left to it. The trunk region, like-
wise, shows less of the concrescence so marked in the carinate
bird) for the the vertebrae are all amphiccelous, and only a few of
them are united into a sacrum ; furthermore, the ribs are de-
cidedly reptile-like in their arrangement. In place of the horny
sheath of the bird's bill, Archaeopteryx was furnished with
numerous little conical teeth, probably lodged in sockets; in
other respects the skull was bird-like. It is argued from the
absence of a crest on the humerus that Archaeopteryx was a
poor flier, (the sternum has not been found, so we lack the
evidence which would have been forthcoming from it), but the
hand was formed of three fingers with independent metacarpals
and stout claws, so it is likely that the anterior extremity must
have been of great service in climbing, the plumage serving,
perhaps, more as a parachute than for true flight. In the
structure of the hinder extremity there is no great difference
from that of a bird.

15. The Ratitae or Cursorial Birds are unquestionably much
closer to the Carinate Birds than Archaeopteryx is ; indeed many

HIGH SCHOOL ZOOLOGY.

133

zoologists regard them as degenerate forms of carinate birds,
which have in the coarse of ages lost the power of flight, while
others, looking at their structure and their geographical distri-
bution, think that they are a more primitive group than the
Carinatse with more affinity to the reptiles, and that they never
possessed the power of flight. The plumage in this group never

Fief. 95. -Skeleton of the Moa (Dtnornis).

134 HIGH SCHOOL ZOOLOGY.

lias the character of contour or quill-feathers, the plumes of
the ostrich being nothing but gigantic clowns. Instead of the
bones of the head uniting early with each other, the sutures are
quite evident, and the cervical ribs are for a long time movable,
instead of being coalesced with the vertebrae. Again, either
the pubic or ischiac bones or both may form a symphysis as they
do in most living reptiles ; and, at least, there is a greater re-
semblance to the Dinosaur pelvis than there is in the carinate
birds. Other anatomical features of the Ratita3 are adaptive ;
the functionless nature of the fore-limbs is associated with the
reduction in size of their bones and of the clavicles, while the
adaptation of the hind limbs to rapid locomotion leads to a loss
of one or two of the four toes.

There is great structural difference between the families of Ratitse, and
they are also marked off geographically from each other. New Zealand
has the Kiwis (Apteryx), small forms of about the size of a turkey with a
very rudimentary anterior extremity and four toes, of which the hinder
one is strongly clawed. Allied to it are the remains of various giant birds
(Dinornithidce), recently extinct and found for the most part in New Zea-
land (Fig. 95). These Moas, as they are named by the Maoris, stood ten
feet from the ground, and their eggs were of very large size. Allied to
them is a similar form from Madagascar (jEpyornis), believed to be the Roc
of Eastern Fables ; the skeleton of this genus is not well known, but eggs
have been found of enormous size, which hold as much as two-and-a-half
gallons, and have been estimated to be equivalent in contents to twelve
dozen hen's eggs. In the rest of the Australian region two other genera,
the Cassowaries (Casuarius), and the Emus (Dromceus), are found, while
in South America, are the three-toed Ostriches {Rhea), and in the
deserts of Africa and Western Asia, the two-toed Ostrich (Struthio
camelus).

Like the Carinatse the Ratitse have no teeth in the jaws, which are
simply clothed with a horny beak, but the genus Hesperornls. which as
far as its sternum is concerned is one of the Ratitse, had only a horny
beak on its premaxillse, while the maxillse and the mandibles had teeth
fixed in a continuous groove. Besides the teeth, there were numerous
other characters which give it an intermediate position between the
Dinosaurs and the Ratitse. The anterior extremity is represented by the

HIGH SCHOOL ZOOLOGY.

135

humerus alone, but the whole skeleton gives the impression of a large
diving bird like a Grebe, living on fish, and swimming by m.ans of the
powerful feet. On the other hand, the genus Icththyornis was truly
carinate, its anterior extremity being like that of an ordinary bird, but
the rest of the skeleton presenting primitive features indicating reptilian
affinities, such as teeth arranged as in Hesperornis (except that they
were in sockets), and amphiccelous vertebras as in# Archoeopteryx.
Icththyornis, therefore, occupies a middle position between Archaeop-
teryx and the Carinatse.

Fig. 96.— Feet of various Avian genera.

a. wading type, Ciconia; b. perching, Turdus ; c. rasorial, Phasianus ; d. raptorial,
Falco ; e. adherent, Cypselus ; b. cursorial, Struthio ; g. scansorial, Picus ; h. locate,
Podiceps; i. lobate and scolloped, Fulica ; k. palmate, Anas; 1. totipalmate, Phaethon.

16. When we come to the classification of the Carinate birds
we meet with great difficulties ; for although we recognise that
there are certain orders which are lower than the others, yet
the adaptation to an aerial life has impressed a certain uniformity

136

HIGH SCHOOL ZOOLOGY.

upon all, concealing such structural characters as might be re-
lied upon for making a natural classification, and causing the
ornithologist to depend frequently on characters which are in
relation to the food or the manner of life (Figs. 96, 97). The

Fig. 97.— Outlines of bills of various genera.

L Leptoptihis, marabu ; P. Passer, sparrow ; Ca. Cancroma, Boatbill ; D. Doci-
mastes, Swordbill ; PI. Platalea, spoonbill ; Pe. Pelecanus, pelican ; T. Turdxis, hrush ;
Re. Recur virostra, avoeet Ph. Phoenicopterus, Flamingo; Ry Rhynchops, Skimmer;
A. Anastomus, stork; B. Balceniceps, shoebill ; S. Sarcorhamphus, condor; Co. Col-
umba, pigeon ; My. Mycteria, stork ; Me. Mergus, Merganser ; I. Ibis.

difficulties of classification are chiefly met with among the
higher orders, to which not only by far the greatest number of

HIGH SCHOOL ZOOLOGY.

137

the species belong, but which exhibit far less important differ-
ences between each other than do the members of the lower
orders.

17. The following arrangement of the orders of Carinatse is that gener-
ally employed ; although there may be doubt as to the affinities of some
of the groups, there is none that the swimming birds occupy the lowest
place and the song birds the highest. Of the former the Pygopodes, or
Divers, are marked by the far back position of the legs required by an
erect or semi -erect at-
titude, by the short-
ness or rudimentary
characterof the wings,
by the complete or
incomplete webbing
of the three toes, and
by their powers of
swimming and div-
ing. The most re-
markable genus is the
Penguin ( A ptenodytes)
of Southern Seas,
(Fig. 98) in which
the power of flight
has been lost, and the
wings are converted
into flippers covered
with scale-like feath-
ers. Another inter-
esting form, in which
the wings, though
feathered, were ex-
tremely short and in-
capable of flight, is the
great Auk (Plautus
impennis (Fig. 99),
which was common in
the Arctic Seas at the beginning of this century, but is now thought to be
quite extinct. Allied to it are the Puffins {Fratercula) with their singularly
shaped and brilliantly coloured bills, and the Sea-pigeons (Cepphus gryUe)

Fig. 98.— Penguin (Aptenodytets)
(after Brehni.)

138

HIGH SCHOOL ZOOLOGY.

the most elegantly formed of the group. More familiar than these
marine forms are the Loons ( Urinator) and the Grebes (Podicipidce), the
latter with the toes merely fringed, the former with the toes entirely
webbed.

18. In contrast with these forms are the long- winged swimmers
(Longipennes), in which the length of the wing is due to the length of
the arm-bones, not of the hand. They are excellent fliers, and sweep
down upon the sea and inland
lakes for the aquatic animals
(chiefly fish) on which they live.
The three front toes are web-
bed, the first, free and often ru-
dimentary. The gulls ( Larus),
Terns {Sterna), and the Jaegers
(Stercorarhis) all belong to this
group. Nearly allied to it are
the marine petrels, to which
small forms like the stormy
petrel or Mother Carey's chick-
en (Procellaria pelagica) be-
long, and the giant albatross,
Diomexlea exulans, with a
wing-spread of 15 feet. The
nostrils of the latter, however,
are tubular, not mere fissures
as in the gulls, etc. ; they are,
therefore, often regarded as a
distinct order (Turbinares).

.*"<•

Fig. 99. — Great Auk. Plautus impennis.
(after Brehm.)

19. The Steganopodes have
received their name from the
complete webbing of the toes,
the first toe being turned for-
ward and united by a mem-
brane to the second. They are all fish -eating birds, but embrace
such different forms as the tropic and frigate birds {Phaethon and
Tachypetes), the darters (Plotm), gannets (Sulci), and, more familiar in-
land, the cormorants (Phalacrocorax), and pelicans {Pelecanus). The
singular mandibular pouch of the last genus marks it from the others.

20. Unlike the above, the Ducks and their allies (Anseres) have the

HIGH SCHOOL ZOOLOGY. 139

hinder toe free ; the others are webbed, and the beak is covered with a
soft skin iD which there are numerous tactile corpuscles, while the gape
is provided with horny lamelhe (hence Lamellirostres), which serve for
straining the muddy water in which they seek their food. The least
duck-like forms are the Mergansers, which have a serrated bill and dive
for fish. A very large number of species of wild ducks are known, from
one of which, the Mallard {Anas boschas), the domestic duck is derived.
To the same genus belong the Teal and Widgeon, but the Shoveller
(Spatula), Pin-tail (Dajila), Wood-duck (Aix) and Red-head and Canvas-
back (Aythya) are sufficiently different to be separated under distinct
genera. The same is true of the Buffle-head (Charitoneta), Harlequin
(Histrionkus), the various species of Eiders {Somaleria) and Scoters,
and the Ruddy Duck {Er'ismatura). The domestic goose is derived from
the European Anser ci?iereus, which genus is represented in America by
the white-fronted goose. Various allied forms, like the Canada goose
and Barnacle goose, are ranged under the genus Branta. To the same
order belong the Swans (Cygnidce), and allied to it are the Flamingoes
(Phcenkopterus) with their singular bent bills, very long legs and
brilliant plumage.

21. In the next order (Herodiones)," we have various genera which like
the Flamingoes have very long legs, the tibia and tarsus being much
elongated, but they differ from them in the structure of the bill, and also
from the following order in the same respect. The bill has no cere or
fleshy part at the root as in the other waders, but it is very differently
shaped in the different genera, e.g., in the Spoonbills (Plataha) it is
flattened and spatulate at the tip, in the Ibises compressed and arched
downwards, in the Storks (Ciconia) much thicker than in the Herons
(Ardeidce), from which the order derives its name. This family embraces
the Herons (Ardea), Bitterns (Botaurus), the Night Herons {Xyctkorax) ;
the rest of the waders are subdivided into marsh-birds and shore-birds.
To the former (Paludicolse) belong the Cranes {Gruida}), and Rails
(Rallidaz) including the Gallinules and the Coots, while the latter
(Limicolse) embrace the Avocets (Becurvirostra), Snipes (Gallinago,)
Woodcock (Philohela), Sand- Pipers (Tringa and Totanus), Curlews
(Numenius), and Plovers (Charadrius and jEgialitis), etc.

22. In contrast to the long-legged Waders we now come to the Galli-
nacei the legs of which are short, stout, and adapted for scraping. The
Pheasant family (Phasianidai), to which the domestic fowl belongs, is only
represented in America by the wild turkey, Meleagris gallopavo, (the
probable stem -form of the domestic turkey), but it is abundantly repre

140 HIGH SCHOOL ZOOLOGY.

sented in the Old World, and especially in India by the Pheasant (Phasi-
auus colchiai-s), Peafowl {Pavo), Guineafowl {Numkla), Argus Pheasant
{Argus), etc. On the other hand, the Grouse family is as character-
istically American as Old World, for we have Ruffed Grouse (Bonasa)
Prairie-hen {Tympanuchus), Ptarmigan (Lagopus), and other forms. Two
aberrant families are associated with the Gallinse which exhibit primitive
characteristics in two different directions, — the Megapodidseof Australia,
which do not hatch their eggs, [but lay them in heaps, to be incubated by
the heat evolved from decomposing vegetable matter mixed with them
and the Tinamus of South America, which in the structure of the skull
remind us of the Ratitse.

23. The Pigeons or Columbse are better adapted for flight than the,
foregoing order, the feet are more delicate, the bill has a soft cere, and the
young are looked after by the parents on their escape from the egg.
In this region we have merely the passenger pigeon {Ectopistes) and the
mourning dove (Zenaidura) ; but the pigeons form a very large group,
especially developed in the Australian region, where the ground-pigeons
{Gourd) and fruit-pigeons {Carpophaga) are abundant. Our numerous
domestic races and varieties are all derived from the Mediterranean
Rock-pigeon {Columba livia). Now extinct forms allied to the pigeon
were the Dodo of Mauritius (Didus ineplm) and the Solitaire of Rodri-
guez (Pezophaps), their extinction being attributable to their rudimentary
wings.

24. All the birds of prey (Raptores) agree in the possession of strong
curved claws and bill, the upper beak projecting like a hook beyond the
lower, and with a cere surrounding the nostrils. The tarsus may be
scutellate or partly feathered. It is naked and extremely long in the
Secretary Bird, Gypogeranus, a crane-like form from the African steppes,
which chiefly hunts Reptiles, but it is comparatively short in the other
gentra, especially so in the Owls, where not only the tarsus is feathered,
but also the foot. The whole plumage in the Owls is of such a character
as to permit the noiseless flight so helpful to them as nocturnal birds.
Their habit of concealing themselves during the day in trees, rocks, etc.,
is assisted by the climbing foot. Some of the species like the Barn -Owl
(Strix), and Saw- whet Owl (Nyctale) have complete radiating disks of
feathers round the eyes, others like the Horned Owls (Bubo), only horns.
The tiny burrowing Owls of the Western States (Speotyto) have the
singular habit of nesting at the ends of long burrows.

The above-mentioned families include extreme types of the Raptores,
between which are the vultures, eagles, falcons, etc. , more closely related

HIGH SCHOOL ZOOLOGY. HI

to each other. Among the vultures those of the New World (Cathartidce)
resemble those of the Old World ( Fulturidce) in the absence of feathers
about the head, but differ in the structure of the bill, and in their habit
of feeding on carrion,, The Falconidae, on the other hand, have a feath-
ered head, shorter bill, and include the various buzzards, eagles, hawks,
falcons and the ospreys.

25. A large series of very different forms used to be associated as the
"scanso^ial birds " on account of their possession of " climbing" feet, but
it is now recognized that they ought to be grouped under several orders.
One of the most singular of them is that of the Psittaci or parrots, which
are marked by the upper bill being shorter than it is high, strongly
curved, movably articulated to the skull, and with a cere surrounding
the nostrils. The lower bill, on the other hand, is short and truncated,
and the tongue fleshy. This is essentially a tropical group, chiefly de-
veloped in South America and the Australian region. It embraces the
cockatoo, macaws, parrots, and ground-parrots. Associated with the
cuckoo under the ordinal name Coccyges, are a number of forms with
the foot more or less adapted for climbing, and with a long bill, but
forming, on the whole, a somewhat heterogeneous group. The Toucans
of S. America with their gigantic bills, the Rhinoceros birds, with the
singular horny process on theirs, the Cuckoos, Motmots, Kingfishers
and Hoopoos belong to this order. The Plci are a more homogeneous
order, embracing the Woodpeckers and Wrynecks ; the toes which are
turned forward are connected at the base, and the bill is sharp and
chisel-like. Finally, the Macrochires receive their ordinal name from
the length of the hand, which is longer than the fore-arm, and that
longer than the humerus. They are good fliers, and embrace the Goat-
suckers, Swifts and Humming- birds.

26. More than half of the species of Birds belong to the last order,
Passeres, in which the bill is differently shaped but always without a cere ;
in accordance with their " perching" habits the hinder toe is longer and
stronger than the second toe ; both the outer toes are connected at the
base. They fall into two sub-orders, the Clamatores, which embrace the
forms destitute of a syrinx such as the Flycatchers, and the Oscines
or singing-birds, which include the Larks, Crows, Jays and Magpies,
the Blackbirds, Orioles, Finches, Sparrows, Tanagers, Swallows, Shrikes,
Creepers, Warblers, Wagtails, Wrens, Nuthatches, Tits, Thrushes and
Bluebirds.

142 HIGH SCHOOL ZOOLOGY.

CHAPTER VI
The Mammals.

1. Among the classes of Vertebrates already studied we have
observed much difference as to the care taken by the mother
of her young. In the Fishes, for example, large numbers of
eggs are produced, and for the most part left to their fate, only
a certain number of the fry reaching maturity. But there are
examples of nest-building forms among them, and of parents
which defend and protect their young, while there are others in
which the young are retained within the body of the mother
until they are able to look after themselves. (I, 94.) Similar
differences are to be met with in the Amphibia and Reptilia as
to this point, and we have also seen that some Birds make very
little provision for the safe hatching of their eggs, while in the
case of others, the eggs are incubated and protected until
the young escape, either able to fend for themselves or
in a condition to require further protection and feeding from
the mother. As an example of special adaptation to the
care of the young may be mentioned the Pigeons, in which the
glantls of the crop secrete a milky fluid during the time of incu-
bation, which is used for the nutrition of the squabs.

2. We meet with an analogous condition of affairs in the
Mammals, where certain glands of the skin are specially adapted
to furnish milk for the nourishment of the young. Even in
this group, however, we see great differences as to the condi-
tion in which the young are brought forth, for puppies aie born
blind and helpless, while the young of the Herbivora are able
to run about shortly after birth. If such differences are to be

HIGH SCHOOL ZOOLOGY. 143

observed in familiar animals, still greater differences characterise
two orders of the Mammalia which are almost confined to the
Australian Region — the Monotremes and the Marsupials. In
the first of these groups eggs are laid, large in size, con-
taining much food-yolk, and surrounded by a shell which
has a certain amount of lime in its composition. After a
short period of incubation the young escape from the shell in
a very helpless condition, and are now dependent on the
milk which exudes from the cutaneous glands of the
mother. In one of the two genera which belongs to this
order, the milk-glands open into a pouch, big enough to receive
the head of the young, but in the other no such provision is
present. The Marsupials, the second of these orders, however,
in which the young are also born in a very helpless condition
(the giant Kangaroo, as tall as a man, brings forth young of
about the size of a newly-born rat), have a provision for shelter-
ing them in the s'hape of the pouch, a fold of the skin on the
ventral surface of the abdomen, which supports and protects the
young while they are being fed by the milk-glands of the
mother, and to which they resort in danger even after they are
able to run about. In this respect, then, we are able to recog-
nize three great groups of Mammalia, (1.) the oviparous forms;
(2.) those which bring forth their young alive, but in such a
helpless condition that they must be carried for a long time in
the mother's pouch ; and (3.) the higher Mammals, in which the
development of the young advances to a much higher degree
within the body of the mother. These groups or sub-classes
have been called Prototheria, Metatheria, and Eutheria, respect-
ively, and while each of the first sub-classes contains only a
single order of Mammalia, the third embraces all the remaining
orders, and contains all the most familiar and conspicuous
quadrupeds. It is not to be supposed that this primary sub-
division into sub-classes depends alone on the characters men-
tioned; there are certain other anatomical differences in the

144 HIGH SCHOOL ZOOLOGY.

skeletal and other systems, which, however, it will be easier to
understand after we have glanced at the structure of one of the
Eutheria, and compared it with that of the foregoing classes.

3. Any familiar mammal will serve our purpose equally well,
but the Cat (Felis domesticd) is perhaps as accessible an example
of the group as we can study. It belongs to the order of the
Carnivores or Beasts of Prey (Carnivora), and is accordingly
furnished with claws and teeth which are adapted to its mode
of life, and is, indeed, one of the most highly specialised of the
order in this respect, so that we must not expect to find it a
primitive example of Mammalian structure.

4. With few exceptions, the mammals are clad with a coat
of hair, which like the plumage of the birds enables them to
preserve their high bodily temperature. The exceptions to
this rule are certain aquatic forms where a subcutaneous ac-
cumlation of fat, the blubber, furnishes the necessary non-con-
ducting envelope, and certain terrestrial forms, where the
epidermis is either extraordinarily thick as in the Pachyderms,
or has given rise to horny scales or other protective coverings.
Even in these cases, however, scattered hairs are present, and
in the aquatic forms referred to, bristles occur about the lips of
the young. So the hairy covering is as characteristic for the
Mammalia as the horny scales are for the reptiles. Although,
like scales and feathers, hairs are epidermal structures, nourished
by a papilla of the corium, yet there is a fundamental difference
between them in their development. Both scales and feathers
begin by a thickening of the epidermis which projects beyond
the level of the skin, and, in the case of the feather, is only
afterwards retracted into the follicle, but the hair begins by a
thickening of the epidermis which grows inwards into the cutis*
and only afterwards comes to project beyond the level of the
skin. (Fig. 100.)

In the Cat two kinds of hairs are present, those which con-

HIGH SCHOOL ZOOLOGY.

145

stitute the fur, and those which form the whiskers (vibrissce);
the latter from the richness of their nerve-supply are especially
tactile in function. In many of the Carnivora and other
orders a soft under-fur is overlaid by stronger bristle-like hairs,

Fig. 100— Section through skin of horse — enlarged, a, epid-
ermis ; b, its Malphigian layer, c, papillary layer of corium, d ;
e, Subcutaneous tissue ; /, hair in its follicle, g, with papilla h ;
i, old hair being replaced by k ; I, sebaceous glands ; m, sweat
glands ; n, sweat duct.

which form the external coat. The hairs are lubricated by the
secretion of the sebaceous glands, which open into the necks of
the hair-follicles. The skin of the Mammal is therefore richer
in glands than is that of the Reptiles or Birds. In addition
to these, however, there are also sweat glands, which select
from the blood certain materials which have to be excreted
from it, and so the skin of the Mammal comes to be an im-
portant excretory organ. Aquatic Mammals alone are desti-
tute of these glands. Of the two kinds of glands referred to,
it is the sebaceous kind which the milk-glands resemble most
as to structure.

146 HIGH SCHOOL ZOOLOGY.

5. In all Mammals (with the exception of some aquatic forms)
it is possible to distinguish all the five regions of the vertebral
column — cervical, dorsal, lumbar, sacral, caudal. In some
aquatic forms (Fig. 101) the hinder extremities have so nearly

Fig. 101. Skeleton of Porpoise. (Phoccena). vc, cervical vertebrae anchylosed ;
vth, dorsal ; vl, lumbar ; vx, caudal regions; pd, dorsai , pc, caudal fins ; pi, pelvic rudi-
ments; c' false, c true ribs ; st, sternum ; sc, scapula ; h, humerus ; r, radius ; ca, car-
pus ; po, pollex ; mc, metacarpus ; ph, phalanges.

disappeared that it becomes impossible to distinguish a sacral
region, but the ribs are always present and connected to the
sternum in such a way as to mark off the cervical, dorsal and
lumbar regions. As we advance through the Vertebrate series
we see a tendency towards the reduction in number, and
towards a constancy in the reduced number of certain parts.
The teeth, for example, will furnish us with a good illustration
of this rule, but it is also well exemplified in the cervical region
of the vertebral column, for not only is it much shorter than
usual in the Reptiles, but (with the exception of a few genera
which also in other respects present primitive characteristics)
it always contains seven vertebrae, and that in spite of the ex-
tremely long and short necks which we meet with in different
members of the class. The other regions vary in different
orders as to the contained number of vertebrae, within narrower
or wider limits, the caudal most of all ; the Cat, e.g., has thir-
teen dorsal, seven lumbar, three sacral, and twenty caudal verte-
brae. (Fig. 102). Instead of the sternal ends of the ribs being
ossified as they are in birds, they are always cartilaginous, and

HIGH SCHOOL ZOOLOGY.

147

Fig. 102.— Skeleton of Cat. (After Strauss-Durkheim.)

oc, occipital ridge ; sc, scapula ; il, ilium ; is, ischium ; f, femur ; pa, patella; t, tibia;

fi, fibula ; c, calcaneum ; mt, metatarsus ; me, metacarpus ; a, pisiform ; r, radius ;

n, ulna ; h, humerus ; x, xiphoid cartilage ; m, manubrium sterni ; cl. clavicle ;

cr, cricoid ; th, thyroid.

the sternum presents more traces of its original mode of
formation than it does even in Reptiles. Thus, in the Cat, it is
composed of eight pieces, the first of which, the manubrium,
carries the clavicles in the mammals in which these bones are
complete, while the last, the xiphoid cartilage, does not become
ossified like the other pieces.

6. The skull of the cat is, of course, modified in connection
with the strong teeth and muscular development of the jaws,
but apart from such superficial characters, a knowledge of its
structure will enable the student to understand that of the
other mammals, and to compare it with that of the lower forms.
It is first to be observed that the bones of the cranium and face,
with the exception of the mandible, are immovably united to-
gether, as in the turtle or bird, but the sutures remain quite
distinct, and the bones can be readily separated from each other in
a macerated skull. The first thing that strikes one in comparing

148 HIGH SCHOOL ZOOLOGY.

the skull of a cat with that of a lower Vertebrate is the relative
proportion of the cranium to the face. Here it is obvious that
the facial bones form only a small portion of the skull, the in-
creased size of which, on the other hand, is chiefly due to the large
surface of the frontal, parietal and squamosal bones which form
the greater part of the brain case. A second feature is the
widely-arched form of that bar (zygomatic or jugal), which ex-
tends from the articulation of the lower jaw to the superior max-
illa, and is, therefore, comparable to the quadrato-jugal bar of the
reptiles. It is widely arched, partly to accommodate under-
neath it the great temporal muscle, which arises in the temporal
fossa bounded behind by the strong lambdoid crest, and partly
to give a wider origin to another muscle of mastication which
arises from its convex outer surface, the masseter. A third
feature is the tendency to union of certain groups of bones sepa-
rated by sutures in the reptiles ; thus the mammalian occipital
bone is formed of the four occipital elements and rests on the
atlas vertebra by two condyles which are borne on the exoc-
cipitals; it likewise absorbs in older animals an unpaired
interparietal^ which is wedged between the supraoccipital and
the parietals. The mammalian temporal bone is similarly com-
plex, because it embraces not only the three periotic bones
with the tympanic and squamosal, but probably also the quad-
rate and quadrato-jugal. Within the bullate tympanic is to be
found the chain of small bones answering to the columella
auris of the reptiles. A third complex bone is the sphenoid,
the elements of which, however, are more easily separated from
each other. They are the basi-, pre-, ali- and orbito-sphenoids
with the pterygoids. Finally the ethmoid, which looks into the
skull with its perforated plates, into the nasal cavity with the
septum and the labyrinthine turbinate, and into the orbits with
its orbital plates, is formed of mesethmoid and parethmoids.

Attention should also be directed to the following points : —

HIGH SCHOOL ZOOLOGY. 149

the union of the frontal and jugals, the strength of the jugal
processes of the maxillaries, and of the alveolar parts of these
bones, the hard palate with the incisive foramina between the
nasal and mouth cavities, and the concealment of the vomers by
the palatines, the foramina for the escape of the various cranial
nerves, that in the lachrymal bone for the passage into the nasal
cavity of the tear-duct, and, finally, the intracranial aspect of the
various bones, with the ossified partition (tentorium cerebelli)
which separates the cerebrum from the cerebellum, and the
hollow on the upper surface of the basisphenoid (sella turcica)
for the accomodation of the hypophysis.

Certain muscular processes on the lower jaw, especially the
coronoid process to which the temporal muscle is attached, in-
dicate the powerful character of the parts concerned. The
articular surface of the mandible is convex, and elongated trans-
versely; it fits into a corresponding concavity (glenoid) bounded
behind by a ridge (postglenoidal) on the root of the zygomatic
process of the temporal bone. It is a question whether this part
of the temporal bone is comparable to the quadrate of the lower
forms or not. The fact that the Meckelian cartilage is con-
tinuous in development with one of the chain of bones within
the drum of the ear (the malleus) caused anatomists to believe
that, in comparison with the Sauropsida, the Mammalian man-
dible has shifted its articulation to the squamosal, but this con-
tinuity is not irreconcilable with the interpretation of the glenoid
region of the temporal as the quadrate.

The complex visceral skeleton of the fish is only represented
in the Mammal by the hyoid bone and its two pairs of cornua.
Both of these a re attached to the extremities of a curved basal
piece, the anterior representing the hyoid, the posterior the first
branchial arch of the lower forms. The former is attached to
the temporal region of the skull, and often unites with it form-
ing a bony process (stylo-hyoid) of the temporal bone. In the

150 HIGH SCHOOL ZOOLOGY.

rest of its course it may be ligamentous, or formed into cerato-
and epi-hyal bony pieces. The posterior cornua are formed by
one bony piece on each side, which on account of their support-
ing the larynx receive the name of thyro-hyal.

7. Considerable difference will be observed in the structure
of the shoulder-girdle, and the mode of its attachment to the
trunk. In the Sauropsida we saw that an intimate connection
of the skeleton of the anterior limb to the trunk was secured by
the union of the clavicles and coracoids to the sternum. But
in the Mammals both these bones may be absent or very much
reduced in size, the shoulder-girdle being represented only by the
scapula, which is then connected to the trunk by muscles alone.
In the cat e.g., the coracoid is in the form of a mere process
projecting from the scapula in the neighborhood of the glenoid
cavity, and the clavicle, which in man is connected to the spine of
the scapula and the manubrium of the sternum, is rudimentary.
As regards the rest of the appendicular skeleton little need be
said, except to call attention to the comparatively primitive
arrangement of the parts (with the exception of the position of
the radius), to the incipient or complete absence of the first toe,
the greater development of one element in the carpus and tar-
sus for the attachment of muscles, and the fact that the meta-
carpals and metatarsals (metapodials) are not in contact with
the ground in locomotion.

In regard to the first point it will be observed that the radius,
although related to the inner border of the carpus and hand, is
connected with the outer border of the humerus ; this is attribut-
able to a twist in the lower end of that bone, which changes
the position of the radius at the elbow joint, and renders it
necessary that it should cross the ulna so as to reach the inner
border of the hand.

In many members of the cat's own order, so-called plantigrade
Carnivores, the feet have a larger surface of contact with the

HIGH SCHOOL ZOOLOGY. 151

ground than in the cats, which are on this account called
digitigrade. The terminal joints of the toes in the cat-tribe
are attached in such a way, that, when not in use, the claws
which they bear do not touch the ground ; they are retracted
into a sheath and are thus always kept sharp. In all the forms,
the skin underlying the portions of the feet which touch
the ground is converted into pads or balls, the thickened
epidermis of which affords protection to the underlying cutis.

8. A comparsion of the relative weight of the brain and body
in the cat with that in any of the lower classes of Vertebrates
will convince us that a great advance in intelligence is to be
expected, and, indeed, the relative size of the brain-case and
facial region in the skull already discloses its superiority in
this respect. At first sight it may he difficult to compare the
cat's brain with that of any of the lower forms studied, for cer-
tain of the regions which are visible in the reptile or bird are
here concealed by the overgrowth of other regions. This is
especially true of the thalamencephalon and the optic lobes, which
are entirely hidden by the backward extension of the cerebral
hemispheres. The cerebellum also has gained in size, especially
its lateral lobes, which are joined by a series of fibres crossing
transversely under the fore part of the hind brain, and consti-
tuting the pons Varolii. In front of the pons, the fibres which
ascend through the medulla oblongata towards the cerebrum
diverge in two masses, the crura, to the hemispheres, and in
front of the crura is the only part of the thalamic region which
reaches the surface of the brain, viz. the hypophysis and in-
fundibulum. On the whole, the most important changes are
those which have taken place in the cerebrum, for not only has it
increased in size by growing forward, backward and towards the
sides, but the grey matter of its surface, instead of being smooth,
is folded inwards in such a way as to leave a series of fissures on
the surface of the cerebrum with intervening convolutions. We

152 HIGH SCHOOL ZOOLOGY.

have already seen in the cerebellum of the bird a similar plan
for accommodating a large s lrface of grey matter in a compara-
tively small space, and the cat's cerebellum also exhibits the
characteristic " arbor vitae " arrangement. The cerebral hemi-
spheres are not inde-
pendent of each other,
for, apart from certain
-ctr transverse bundles of
fibres present in the
lower classes, there is
also formed between

K p
Fig. 103. -Median longitudinal section of brain of cat tll0Se Parts °f tne hemi"

(Modified after wilder. j spheres which project

s. Spinal cord with contained central canal, mo, me- UqpIt nwr- ihn +vno ™r»f
dulla oblongata ; p, pons Varolii ; cb, cerebellum, form- DaCK OVer T"e Tlue rooT
insj the floor and roof of the 4th ventricle, mes, optic nf +V»p TirniTi /W\cr 1 (V-U
lobes or corpora quadrigemina, the roof of the mesocoele Ul cuc uuuu \x &* 1U'J/
or" iter," the floor is formed by the crura in front of the nrn'mnnrtmit- trnn«vpr«<i
pons. In front of the mid-brain is the thalamic region, ^important transverse
the cavity of which (3rd ventricle) is traversed by acorn- commissure the COrDUS
missure, c', uniting the side walls or thalami ; the ' *

roof is partly formed by the epiphysis (above vies), and calloSUm, which serves
the floor by the hypophysis k ; but the chiasma. ch. of

the optic nerves, II, also forms part of the floor, while to effect COmmunica-
the anterior thin wall (terminal lamina) is above the

chiasma. The cerebral hemispheres, cer, are right and tions between the two
left of the lamina, and connected by cc, the corpus oallo- ,

sum ; oi, the olfactory lobe sides. In some higher

mammals the cerebral hemispheres project so far forward as
to conceal the olfactory lobes from above, but in the cat these
are well marked off from the rest of the brain.

9. As far as the sense-organs are concerned, we shall find that
the nose and ear are those which exhibit conspicuous advan-
tages in structure over the lower classes. The olfactory cavity
in the fowl is not entirely smooth, but in the cat the olfactory
mucous membrane covers an extremely complicated surface,
furnished chiefly by the ethmoid bone, but also supported by
independent turbinal bones. The olfactory lobes rest upon
the cranial surface of the mesethmoid, separated by a median
crest in that bone, and sending the olfactory nerve-fibres down-

HIGH SCHOOL ZOOLOGY. 153

ward into the mucous membrane of the complicated labyrinth,
through the perforated or sieve-like plates of the ethmoid. The
right and left nasal cavities are separated by the perpendicular
plate of the ethmoid, and by the cartilaginous partition
(Septum), which extends as far as the nostrils. Certain small
cartilages not present in the lower forms are developed in the
external nose for its support, and for the attachment of the
muscles which move the nostrils. An organ of Jacobson, such
as is well developed in the snakes, is present in the cat, but it
has only a cartilaginous capsule, and it opens into the mouth
on each side through the incisive foramina. In the far-back
position of the posterior nostrils, the cat and other mammals
resemble such reptiles as the turtles and crocodiles, but the
pterygoid bones do not take part in bounding the nostrils.

10. Reference has been made above to the great develop-
ment of the tympanic cavity, but there are also other modifica-
tions of the amlitory apparatus, which make the ear of the
mammal more efficient (Fig. 104). In the first place the outer ear,
or pinna, is formed with its supporting cartilages, which serve for
the attachment of the muscles which move it. The chain of
bones, also, which effects communication between the tympanic
membrane and the labyrinth, is more complex ; it contains three
elements, the malleus, incus and stapes, of which the first
is connected in the young with Meckel's cartilage while
the last, a stirrup-shaped bone, occupies the fenestra ovalis.
Zoologists at one time thought that from the connection of the
malleus with Meckel's cartilage, the former bone must be com-
parable to the quadrate of lower forms, but the view is gaining
ground that the whole chain is comparable to the columella
auris of the lower forms.

With regard to the labyrinth, an important advance in struc-
ture, which we meet with in most mammals as compared with
the Sauropsida, is that the cochlea, instead of being a straight
11

154

HIGH SCHOOL ZOOLOGY.

tube, is coiled up like the coils of a snail's shell (from which
indeed the name cochlea is derived), and the branch of the
nerve which goes to it has to occupy the axis or columella of
the coil, so as to reach the whole length of the tube.

Fig. 104.— Partly diagrammatic representation of auditory apparatus in man.
(The external and middle ear are in their proper position, hut the lahyrinth is rota-
ted inwards through 90° ; both tympanic cavity and labyrinth are twice the natural
size, the external ear is the natural size). g£, auditory passage ; tf, tympanic mem-
brane , ph, t>mpamc cavity; ot, Eustachian tube; h, malleus; a, incus; s, stapes;
vh, vestibule of labyrinth ; bg, semicircular canals ; vht, scala vestibuli of cochlea ;
tht, scala tympani, leading to fenestra rotunda, rf ; sb, temporal bone '3 osd, parotid
gland.

11. The mammals present just as great diversity in the
nature of their food and in their method of securing it as do any
of the lower classes. Important reactions on the structure of
the creature, especially on its intestinal system, are to be ex-
pected, and the teeth as well as other parts are thereby affected)
Much importance is attributed by systematists to these organs,
because they are readily accessible to inspection, are the only
parts of the intestinal system preserved with the skeleton in
fossils, and are extremely constant, not only in number but also
in form, for any particular species. Like most mammals, the cat

SIGH SCHOOL ZOOLOGY. 155

has two sets of teeth, the milk set and the permanent set :
it is diphyodont. Some mammals are monophyodont, they
have only one set of teeth, which are destitute of the fangs
or roots of ordinary teeth, and are simply added to in length by
the pulp, as their free surface becomes worn down. Other
forms, which are diphyodont with regard to the greater number
of their teeth, still retain some with this unlimited power of
growth. Although in some reptiles certain teeth are dis-
tinguished from their neighbours either by their form or by
standing isolated in the series, yet no such specialisation of the
teeth in the different parts of the gape occurs, such as we find in
the mammals. Here the premaxillary bones lodge teeth of a
distinct form, the incisors, which in the cat are six in number,
and are separated by a gap or diastema from the large and sharp
canines, the foremost teeth of the maxillaries. Corresponding
but alternating with these are similar teeth in the lower jaw,
but the gaps are in this case behind not in front of the canines.
Behind the canines are the premolars, i.e. the teeth which re-
place the back teeth of the milk dentition, and behind these the
true molars, which only appear in the permanent set. Both
kinds of grinders are reduced in number in the cat in accord-
ance with the principle of specialisation referred to in § 5.

There are three premolars and one molar in the upper jaw
but only two of these are functional, the first premolar and
the molar being evidently rudimentary. On the other hand,
there are two premolars and one molar in the lower, all three
of which are functional teeth. The same alternation which is
to be seen further forward in the gape is also to be seen here, so
that the cat's dental formula of one side might be expressed
thus : —

i i i C pm pm PM m
i i i C * pm pm M

The teeth marked in full-faced type are the characteristic

156 HIGH SCHOOL ZOOLOGY.

teeth of the carnivorous dentition, the canines and sectorials,
specially developed in accordance with the carnivorous habits,
while the asterisk indicates the gap caused by the absence
of the first premolar. It is interesting to compare this formula
with the less specialised dentition of a dog: —

i i i C pm pm pm PM m m
i i i C pm pm pm pm M m m
Here it is obvious that the last premolar above, and the first
molar below are, as in the cat, the sectorial teeth, and although
the molars proper are more numerous, they show the same
tendency to a rudimentary character at either end of the
series. As far as numbers go, the bear's formula is the same as
the above, but there is no specialisation of the sectorial teeth,
and both the bear and the clog present a formula, which is very
near to what is generally considered the typical formula of the
Mammalia, only differing therefrom in the absence of a third
upper molar. Rewriting, then, the cat's dental formula after
comparing it with that of the dog, we should have the follow-
ing better expression of its dentition.

i1 i2 i3 c * pm2 pm3 PM4 m1 * *
ji ^ ^3 c * * pm3 pm4 Mi * *

When it is not considered necessary to indicate the relative
position and character of the teeth, the dental formula is gen-
erally simplified ; thus, (for the cat) : — if c£ pmf m^.

In respect to their form, the molars in the Carnivores
hardly deserve the name of grinders, for the functional
molars have sharp cutting edges not adapted for grinding.
The bears and their allies, however, which are more omnivorous
in their habits, show how a cuspidate molar may be worn down
to a grinding surface.

12. Inmost mammals the lips and tongue attain consider-
able independence of movement ; this is associated with the
development of a complicated musculature which is hardly

HIGH SCHOOL ZOOLOGY. 157

represented in the lower forms. The hinder part of the roof of
the mouth likewise is contractile, and becomes the soft palate,
a flap of which, known as the uvula, hangs down in the middle
line, so as to cut off a posterior chamber or pharynx from the
true mouth-cavity. The aperture between the two is further
narrowed by folds at either side, the pillars of the fauces,
between which are the tonsils belonging to the lymphatic
system. (I, 63). The pharynx communicates above with the na^al
cavities, below with the larynx and oesophagus, the aperture
into the former tube being always protected by the epiglottis,
a movable fold behind the base of the tongue. The primitive
mouth-cavity which we studied in the lower forms is thus not only
separated into a respiratory chamber above (the nasal cavities),
but into an alimentary chamber below, which further presents
from before backwards, a buccal cavity between the lips and
the gums, the mouth-cavity proper and the pharynx. The
structural advance which we thus see in the mammals is partly
determined by the use of the lips for prehension, partly by the
longer retention of the food in the mouth, for admixture with
the secretion of the salivary glands, for mastication and for sub-
mission to the organ of taste.

13. In all mammals the salivary glands are arranged in three
masses, parotid, submaxillary, and sublingual, and their secretion
partly serves to facilitate the swallowing of the food, and partly
to aid in the digestion of the starchy constituents thereof. The
organ of taste is composed of certain bud-like structures which
recall the sense-organs of fishes (I, 9), and which are chiefly
situated in the walls of trenches surrounding the large circum-
vallate papillae at the back of the tongue. Fungiform and
filiform papillae are also present in the tongue of all mammals,
the latter clothed with horny epidermic sheaths in the carni-
vores, and giving the front of the tongue its rasp-like surface.

14. In the lower forms studied, the ccelom is an undivided

158 HIGH SCHOOL ZOOLOGY.

cavity, in front of which is the heart with its separate serous
sac, the pericardium ; the lungs, when present, project into the
ccelom, and are covered with the same serous coat as the in-
testines, but, in the mammals, the coelom is sub-divided by a
muscular partition (the diaphragm), into a thoracic cavity con-
taining the lungs and the heart, and an abdominal cavity con-
taining the other viscera. That part of the cavity which
belongs to the lungs is now called the pleural cavity, the heart
with its pericardium remaining independent between the two
pleuraa. The diaphragm acts chiefly as a muscle of respiration,
serving by its construction to enlarge the thoracic cavity, and
thus to facilitate the changes of the air in the lungs. Certain
structures like the oesophagus, the aorta, and various nerves,
must pierce the diaphragm so as to reach the abdominal cavity ;
they do so after traversing the mediastinum, or space between
the pericardium, the pleurae and the vertebral column. The
intervention of the diaphragm thus forms a sharper boundary
between the oesophagus and stomach than we have met with
in the lower forms. In no mammal has the stomach the
simplicity met with in the Ichthyopsida or Reptiles. If it be
considered as a dilatation of the intestinal tube, it is always a
one-sided dilatation, so that there is a short curvature (the un-
dilated side of the tube), and a greater curvature (the dilated
side). Its form in the Cat is quite simple, but in herbivorous
animals there is generally a much more complex stomach, and
in these also the intestine is relatively much longer. The chief
difference in the mammal's intestine as compared with lower
forms, is the proportionately much greater length of the large
intestine.

15. As regards the respiratory system, apart from the differ-
ences referred to above, the most important is the more min-
utely " cellular " character of the lungs, the bronchi dividing
up dichotomously into smaller tubes which eventually end in
the alveoli or air-cells. There are thus no membranous ppr-

HIGH SCHOOL ZOOLOGY.

159

tions of the lung- walls or sac-like projections thereof, such as
occur in the Sauropsida. The upper part of the windpipe is of
great interest, however, because it is first in the Mammalia, in
which we meet with the characteristic arrangement of the hard
parts of the larynx, which attain their perfection in the vocal
organ of man. In addition to the cricoid and arytenoid car-
tilages, such as are met with in the lower forms, a third, the
thyroid, is developed which forms the " Adam's apple " of the
human larynx and serves with the arytenoids for the attach-
ment of the vocal cords. A membrane stretches from the
outer edge of the thyroid cartilage to the tbyrohyals (§ 6), and
the larynx is thus brought into connection with thehyoid bone.
16. We saw that the great respiratory activity of the birds
requires a complete separation of the arterial and venous blood

in the heart : this is effected
in the same way in the mam-
mals, the right auricle and
ventricle, respectively, receiv-
ing the venous blood from the
body and pumping it through
the lungs, while the left
auricle and ventricle, res-
pectively, receive the aerated
blood from the lungs and
pump it through the system
(Fig. 105). Some difference
is to be observed in the great
vessels which come off from
the heart, notably as to the

Fig. 105^-Heart and Lungs of Man t ^ ^ which ^
a, descending aorta ; Ik, -left, Tk, right » »
ventricle; rvk, right auricle; ha, inferior £he fourth arterial arch of
vena cava ; 1, trachea ; e and f, the two caro-
tids ; beside these, dand g the two internal t]ie left not Qf the right side,
jugular veins ; c and l, subclavian arteries; °
b and m, subclavian veins. as fn birds. The blood, which

160

HIGH SCHOOL ZOOLOGY.

returns from the intestines is subjected to the action of the
hepatic cells while passing through the portal circulation, but
the venous blood from the posterior extremities is returned
directly to the heart through the posterior vena cava, the kidney
(which first attains in the mammals its reniform shape) receiv-
ing its blood supply entirely through the renal arteries.

17. Having now examined into the structure of one of the
typical mammals, or Eutheria, let us see in what respects the
Prototheria and Metatlieria differ therefrom.

The Prototheria embrace only a single order — Monotremata —
represented by two well-known forms, the Duck-mole (Orni-
thorhynchus 2)aradoxus), and the Porcupine Ant-eater (Echidna
hystrix) of the Australian region (Figs. 106 and 107). Out-
wardly, and in their
habits, these creatures
differ very much from
each other, the Duck-
mole being an aquatic
animal, with soft un-
der - fur covered by
stiff over-lying bristly hairs, which prevent the wetting of the
fur, with webbed feet which adapt it for swimming, and with
a horny, toothless bill like a duck's, evidently adapted to

secure food in the same
way ; while, on the
Other hand, the Porcu-
pine Ant-eater is pro-
vided with stout bur-
rowing feet, by the aid
of which it opens the

Fig. 107.— Porcupine Ant-eater. (Echidna hystrix). A ants' nests, on the Con-
tents of which it feeds, is protected by stout spkies instead
of the bristly coat of the Duck-moles, has a sharp snout

Fig. 106.— The Duck-billed Platypus. $
(Ornithorhynchus paradoxus).

HIGH SCHOOL ZOOLOGY. 161

like most of tlie ant-eaters, and secures its food with its
tongue. There are no teeth, at least rudimentary teeth which
are present in the embryo never break through the jaw, so we
are obliged to consider the absence of teeth not as a primitive
character, but as an adaptation to habits of life.

Inwardly, however, the Monotremes agree with each other,
and differ from the other mammals in many important respects,
such as the presence of an episternum (III. 18), with which the
clavicles articulate, and of complete coracoids, which unite the
scapula and sternum. There are also other features which,
like their oviparous habits and the structural characters associ-
ated therewith, remind us more of the Sauropsida than the
Mammalia ; such are the simplicity of the brain and of the ear,
and the temperature of the blood, which is much more like
that of the surrounding medium than in the ordinary mammals.

18. The Metatheria similarly correspond to a single order,
the Marsupialia. This order receives its name from the pouch
referred to above (§ 2), which is supported by two epipubic
bones, present in all members of the order, whether the pouch
is well-developed or not. The Monotremes also have these
epipubic bones, so it is probable that they are not formed in
connection with the pouch, but rather represent such structures
as the fore part of the pelvis in the Menobranch. Although
the Marsupials are specially developed in the Australian region,
they are not exclusively confined to it, for in America there are
several species of opossum (Didelphys), and in the Oriental
region also, there are a few representatives of the group.
Australia is, nevertheless, the home of the Marsupials of the
present day, although it is of interest to note, that the earliest
fossil remains of mammals, obtained in Europe and other parts
of the world, indicate that they ought to be associated with the*
Metatheria instead of the Eutheria, and, therefore, that this
sub-class was at one time much more widely distributed than it
now is.

162

HIGH SCHOOL ZOOLOGY.

A great variety of forms occurs among the Australian Marsupials. There
are some like the Tasmanian devil (Dasyurus), or like the native dog,
{Thylacinus) which are distinctly carnivorous in their habits ; other
fruit-eating forms which are arboreal, and are adapted for their mode
of life by the possession of a long prehensile tail, or even, as in the case
of the flying phalangers (Phalancjista), of a patagium like our flying
squirrels ; again, there are herbivorous forms like the kangaroos (Fig.
108), in which the fore legs are extremely short, the hind limbs chiefly
used in locomotion and the toes reduced in number, and, finally, there are
forms (Phascolomys) with gnawing teeth like the beaver's, which are
associated with similar methods of securing food. Such features as the
above are evidently adapted to the habits of the creatures, but there are

Fig. 108. Giant Kangaroo. (Halmaturvx giganteus). fs

certain underlying structural peculiarities common to the whole group
apart from those refered to in § 2. The dentition e. g., is not refer-
able to the same type as that of the higher Mammalia, the teeth being
much more numerous ; the tendency to union of different tracts of skull-
bones (§6), is not so well-marked, and the angle of the lower jaw bone
is turned in, in a characteristic way, which has assisted in the identi«
fication of the fossil remains of this nature.

HIGH SCHOOL ZOOLOGY. 163

19. When we finally study the group of the higher mammals
or Eutheria, we find a wonderful diversity of form in the differ-
ent orders, depending on their habits and methods of locomotion.
Certain aberrant orders may first be referred to, which occupy a
somewhat isolated position in the sub-class. Of these the
Bruta or Edentata is a very heterogeneous order, embracing the
ant-eaters of the Old and New Worlds, and the sloths of South
America. The former differ very much in the clothing of the
skin, for in the Indian genus Manis (Fig. 109), it is formed of
large overlapping horny scales, while in the South American
Myrmecophaga, coarse hair replaces these. Both genera have a
long snout and a long protrusible tongue by means of which
(and the secretion of tne large salivarv glands) they secure their

Fig. 10J. Scaly Ant-Eater or Pangolin. (Manis longicaudata). ^

food. The Brazilian armadillos (Dasypus) and some other
South American allied forms have the skin of the back and
sides converted into a more or less complete shield of bony
plates, while the African Orycteropus is clothed with coarse
hair. Unlike the Carnivores, the teeth, if they are present at all,
are all alike, often very numerous, and there is only one set.

20. Contrasting with these forms which have all strong
burrowing feet are the sloths, in which the claws are curved in
such a way as to be only useful for an arboreal life. The teeth
are less numerous than in the insect-eating armadillos, and their
surfaces are flat and not tuberculate ; the toes in accordance

164

HIGH SCHOOL ZOOLOGY.

with their different function are reduced to three (Brady-
pus) (Fig. 110, F) or two (Cholcepus). Very complete remains
of extinct forms intermediate between these two subdivisions
of the order have been found in South America ; these include
gigantic forms like Megatherium, almost as large as an elephant,
which probably fed on the foliage of trees, uprooted by their
powerful limbs.

■ *

Fig. 110. Manus of various Mammalia.

P, Horse. D, Dolphin. E, Elephant.. A, Orang. T, Tiger. 0, Ox. F, Sloth.

M, Mole, r, radius, c, carpus, m, metacarpus, s, sesamoid bone.

ph, phalanges, ds, dew-claws.

21. A second aberrant order is that of the Cetacea, which
owe their peculiarities to their aquatic life. This is not the
only order of Mammalia in which aquatic habits are present, for
certain carnivorous animals like the seals, sea-lions and walruses,
are exclusively or almost exclusively confined to water, yet in
the Cetacea, this adaptation is carried so far as to isolate them
from the other orders of the sub-class to which they belong.

HIGH SCHOOL ZOOLOGY. 165

The general spindle-shape of the body (Fig. Ill), the hairless skin,
the thick layer of blubber, the rudimentary character of the
olfactory organ, and the consequent restriction of the nostrils to
the respiratory function, the situation of the nostrils on the
top of the head, the conversion of the anterior extremities into
flippers (Fig. 1 10,D), the almost complete absence of the skeleton
of the posterior extremities, the peculiar horizontal caudal fin, and
the dorsal fin occasionally present, are all features which are asso-

Fig. 111. Outline of White Whale of St. Lawrence. (Beluga.) fa

ciated with the conditions of their existence. The whales have
only one set of teeth, but these disappear in some of the mem-
bers of the order, being replaced on the upper jaw by the horny
strainers (whalebone), which prevent the escape of the minute
creatures on which the whalebone-whales live. Two groups of
Cetacea are therefore distinguished — the toothed whales and the
whalebone-whales. To the former belong the porpoises, (Pho-
coena); dolphins, (Delphinus); white whales, (Beluga, Fig. Ill);
as well as the grampus (On a) and the singular Narwhal (Mono-
don) ; they chiefly live on fish and cuttle-fish, for seizing which
they are provided with numerous sharp conical teeth, but the
Grampus has only a few very powerful and sharp teeth, in ac-
cordance with its habit of attacking the larger forms of its
own order, and the adult Narwhal is quite toothless, except for-
the single long spiral tusk of the male.

Only the lower jaw is provided with teeth in the Spermaceti
whales (Catodon), which are chiefly remarkable for the
enormous head swollen up by the accumulation of spermaceti
between the skull and the skin.

166 HIGH SCHOOL ZOOLOGY.

A considerable proportion of the length of the body in the
whalebone-whales likewise belongs to the head. The members
of this group attain the largest size of any whales, some of
those with a dorsal fin (Physalus) measuring as much as one
hundred feet in length, while the right whales^ which are the
chief objects of the whale fisheries, never measure more than
sixty feet. (Fig. 112.)

Fig. 112.— Outline of Greenland Whale. (Balcena mysticetits.) ^

22. A third aberrant order, that of the Sirenia, have a
certain superficial resemblance to the Cetacea, which is associ-
ated with their aquatic mode of life, but they are not so com-
pletely adapted thereto, being herbivorous forms, and thus
necessarily frequenting the shallow waters of the shore-zone for
sea-weeds, or ascending the estuaries of the great tropical rivers
and browsing upon the vegetation which fringes their banks.
The manatees (Manatus) of Western Tropical Africa, and of
Eastern South America, are, indeed, not completely helpless on
land, the fingers in the flippers are marked by short nails, and
in all the forms, the presence of a neck, the position of the
nostrils at the end of the muzzle, and the less rudimentary
character of the pelvis indicate less departure from the typical
mammalian form than is to be seen in the Cetacea. One of
the forms, the northern sea-cow, (Rhytina), exterminated little
more than a century ago, was previously abundant on the
shores of Siberia and Kamschatka. It was toothless, the
mouth being provided with four horny -toothed pads, which
served in place of the grinders of the living forms. These are
more numerous in the manatee, than in the dugong of the Indian

HIGH SCHOOL ZOOLOGY. 167

Ocean {Halicore, Fig. 113), but the latter has tusk-like incisors
in the upper jaw, which are only transitorily present in
the manatee. The caudal fin of the latter is by no means so
effective a propelling organ as is that of the dugong, which
creature is, on the other hand, quite helpless on land. While
the skin in the sea-cow was extremely thick and hairless, that
of the manatee is covered with stiff bristles, which are both
fewer in number and shorter in the dugong. Some fossil

Fig. 113.— Dugong (Halicore.) ^

members of the order are known, in which both the teeth and
the skeleton of the hind limbs are more completely represented
than in the living Sirenia, but these, instead of uniting the
group to the Cetacea, rather prove an alliance with the hoofed
animals, to the study of which we now proceed.

23. The remaining orders of Mammalia arrange -themselves
naturally in two series, the Hoofed Animals ^Ungulata) on the
one hand, those provided with claws and nails on the other
(Unguiculata). Although, at first sight, this distinction appears
to be of little importance, the hoof being a horny covering for
the whole of the distal joint of a toe, while the claw or nail is
merely developed on one surface (the anterior), yet it is the
mark of a difference of function which is associated with some
of the most characteristic peculiarities of the Ungulata. In by
far the greater number of the living hoofed animals the extrem-
ities are devoted entirely to the function of locomotion, and in
most cases the number of toes is reduced in accordance with a

168 HIGH SCHOOL ZOOLOGY.

principle referred to above. They thus contrast with the
Unguiculata, which retain for the most part the typical number
of toes. If we, however, extend our survey from the living to
the fossil Ungulates, we shall find that the reduction of the
number of toes is comparatively recent in the history of their
series, the oldest forms being five- toed like most Unguiculata.

24. The most primitive order of the hoofed animals in this res-
pect (Fig. 110 E) is that of the Proboscidea or Elephants, al-
though in other respects it is one of the most specialised and high-
ly organised of the series. The only living genus is Elephas,
represented by two species JE. indicus and africanus, the latter
distinguished from the former by its enormous ears, and by the
lozenge-shaped ridges on the molar teeth. In both the living
forms, the thick skin has only a few isolated bristles, but the
fossil mammoth {E. primigenius), which was abundant in

Fig. 114— Skeleton of Mastodon.

Siberia and Alaska, and of which frozen carcases have been
found, was covered with wool intermingled with coarse hair.
Most of the peculiarities of the skull are attributable to the
singular dentition of the Elephant, which consists of two huge
incisor tusks in the premaxillaries and, in addition, six grinders

HIGH SCHOOL ZOOLOGY. 169

on each side in each jaw, which, however, instead of being pre-
sent simultaneously, succeed each other, so that only one, or at
most two of the six are in function at the same time. The length
of the tusk-sockets causes the great height of the skull, which
is especially large in the Indian elephant, not so much from the
size of the brain, as from the great thickness of the middle or
spongy layer of the cranial bones. In the fossil genius Mastodon,
(Fig. 1 14) of which many remains are found throughout Ontario,
there were tusks in the lower jaw as well ; the grinders suc-
ceeded each other as in the elephant, but they had from three to
six transverse rows of tubercles, from which the genus derives its
name. One can arrive at the structure of the elephant's tooth
from that of the mastodon, by imagining the transverse rows
added to in number, their surfaces worn down and the intervals
between them filled up with cement.

The neck is so short that the proboscis or trunk, an elongated
external nose with a finger-like process at its tip over the nostrils*
becomes necessary for securing food ; it requires, therefore, to be
very muscular and sensitive. The apparent disproportion between
the length of the fore and hind limbs is due to the fact that the
latter are inclosed within the skin of the loins nearly to the
knee-joint, but the bones of the fore and hind legs are ap-
proximately of the same length. A curious difference of gait
is observable between the elephant and higher Ungulates on
account of the position of the elbow and knee joints in the former;
they occupy the middle of the limbs, the metapodials being
quite short and contributing to the formation of the soles of
the feet, whereas in the latter, the metapodials become the
long cannon bones, the wrist and ankle joints are raised to
the middle of the limbs, being known as the "knee" and
" hock " respectively, and the true elbow and knee joints are
close tip to the trunk. The higher Ungulates therefore are not
plantigrade like the elephants, "but walk on the tips of the

distal joints of the digits. (Fig. 1 10, P and 0).
12

170 HIGH SCHOOL ZOOLOGY.

From what has been said above, it will be understood that
the geographical distribution of the elephants was formerly by no
means so limited as it is at the present day; for, in addition to
the mastodons already referred to, true elephants were abund-
ant in Ontario during the pleistocene period, and ranged
southwards through the States to Mexico.

25. Associated with the earliest fossil elephants, there have been found
in Miocene strata in Europe remains of a proboscidean of gigantic size
(Dinotlierium), the skull of which measures some five feet in length, and
differs from the elephant's, in that some five molars replace the single
grinder, and that the lower jaws contain the tusks. The conformation
of the skull suggests a trunk like the elephant's, and the bones of the
feet, which have also been found, prove it to be referable to this order.
2so examples of it have been found in America, but in the earlier Eocene
strata are found remains of mammals of the size of elephants, and with
bones so similar, that some nearer alliance is suggested than that they
are mere predecessors in time. Their skull and teeth, however, were
specialised in a very different direction from that of the Dinotherium,
for the former was provided with three pairs of bony cores for the at-
tachment of horns (whence the name of the principle genus and the
order Dinocerata), and the latter were arranged in the following pecu-
liar way : —

isclpm^ml
there being no upper and very small lower incisors, while the upper
canines were tusk-like, the lower ones small, and the small molars with
two transverse ridges. Casts of the cranial cavity of these early Mam-
malia show that the brain was very small in size, and low in its type of
structure.

More primitive than Dinoceras and its allies with regard to the teeth
are Phenacodus and Coryphodon from the lower Eocene, which have the
typical formula §11, and, in the former case, truly tuberculate teeth. All
the toes are present, the middle one in Coryphodon, however, being
distinctly the longer, as in the tapirs. No such primitive hoofed ani-
mals persist till the present day, all of them (with the exception of
the elephants) having undergone a reduction of the number of toes.

26. Before we proceed to the typical hoofed animals there is one aber-
rant genus (Hyrax) to be mentioned, which is placed in an order by itself
(Hyracoidea). This order includes several species of timid little crea-

HIGH SCHOOL ZOOLOGY. 1?1

tures of the size of rabbits, which extend from, the Cape of Good Hope
to Syria (the coneys of Scripture), living in crevices in rocky and moun-
tainous districts. The toes are four on the fore, and three on the hind
limbs, being all provided with fiat hoofs, except the inner hind toe,
which is clawed. Unlike those of the higher Ungulates, the hoofs do not
support the weight of the body, which rests on the soft soles attached to
the under surface of the other joints of the toes, and which, applied
sucker-like to the rocks, enable them to perform marvels of climbing.
Like the rabbits they have a rodent dentition, i.e., the incisors — 1\ — wear
down to a chisel-shaped edge and have growing roots, the upper are
curved, the lower horizontal, there are no canines and the molars
(pm% 77i%) are provided with transverse ridges. In other respects the
Hyrax is more nearly related to the true Ungulata, and especially to the
order of the odd-toed Ungulates, which we now proceed to study.

27. Reference was made to the fact that in one of the earliest
fossil Ungulates the middle (third) toe is longer than the others,
and therefore contributes more to the support of the body. A
similar preponderance of this toe is to be observed in all odd-
toed( imparidigitate) Ungulates, which constitute the order called
on this account Perissodactyla. The first and most primitive
family of these is the Tapiridce, represented by one Indian and two
South American species of Tapir (Tapirus). These are swamp-
loving creatures with short smooth hair, a short tail, an almost
trunk-like proboscis, feet four-toed in front and three behind
like the Hyrax, but with a more primitive dentition, i § c ]■ m £.
Although so limited in number at the present day, numerous
fossil tapirs are known, as well as forms (Palceotherium, &c),
connecting them with the Coryphodons, and with the Rhino-
ceroses which constitute the second family of the order. This
family (Rhinocerotidoe) contains only a single genus with four
species living in India, Java, Sumatra and Africa respect-
ively, the two former being one-horned, the two latter two-
horned species. In all, the skin is provided very sparingly with
hair, is very thick and often divided off into shields ; the horns
are not supported by a bony core. In the living forms there
are only three toes (viz. nos. 2, 3, 4) present, but in certain

172

HIGH SCHOOL ZOOLOGY.

fossil forms the fifth toe was also present in the fore foot, as in
the Tapir. The earlier fossil Rhinoceroses had a more complete
set of teeth than the living species, which have no canines, and
have a tendency to lose the incisors, while the molars are present
to the full number \. Like the Elephants, the Rhinoceroses had
once a much wider geographical distribution, for remains of the
woolly rhinoceros are found with those of the mammoth in
Siberia, and numerous American representatives of the family
have also been found. Among these are Miocene forms which
had two horns side by side, and attained elephantine dimensions
( Brontotherium).

28. The third family of Perissodactyla is represented at the
present day by the single genus Equus, to which the horse and
various species of asses and zebras belong. It diners from the
foregoing, in that the body is supported entirely on the third
toe, the distal joint of which (coffin-bone) is covered with the
hoof, while the second joint (coronary) and proximal joint
(fetter-bone), but especially the metapodials (cannon-bones) are
much elongated, bringing the wrist and ankle-joint up to the
middle of the leg (Fig. HOP). The second and fourth toes have
disappeared almost entirely, but they are represented by the
rudimentary metapodials (splint-bones), the proximal ends of
which, only are complete. Occasionally it occurs that a horse
is born with these rudimentary digits in a more perfect con-
dition, the splint-bones not only being complete, but carrying
short digits, the ends of which may be clad with miniature hoofs.
Such a three-toed horse is evidently a reversion to a more
primitive Perissodactyle type, and such reversions are known
as instances of " atavism."

This family presents a more typical dentition than does the
foregoing. The incisors are j, the canines small, especially in
the mare, and there is a long diastema between the front teeth
and the grinders which number g, the first milk molar not

HIGH SCHOOL ZOOLOGY. 173

reappearing in the permanent dentition. A peculiarity of
the incisors is that the surface enamel is folded in like the in-
verted finger of a glove, the result being a ring of enamel which
constitutes the mark of the incisors, until, in the aged horse, the
tooth has been worn down below the fold. In all the members
of the family, the hair of the mane and tail is long, and there
are present callosities in the skin near the knees and hocks, but
in the asses and zebras, the hair is only long at the tip of
the tail, and the callosities are only present on the fore-legs-
The zebras are South African forms distinguished by black
stripes on a cream-coloured ground ; the asses occur in North
Africa, "Western and Central Asia, the North African species
being probably the source of the domestic ass. Although
horses are found in a feral condition (i.e., apparently wild, but
really only secondarily so) in Asia and South America, it is un-
certain whether the original stock still exists in a wild condi-
tion ; some recent investigations, however, in the high table-lands
of Thibet point to the conclusion that such is the case. The
South American horses were imported by Europeans, but it is
not to be supposed that the New World was until the time of
its discovery uninhabited by horses. Fossil remains of true
horses show that they were abundant in America long before
their importation from Europe, and from the various Tertiary
strata numerous representatives of the family have been dis-
covered, so that the American fossil Equidss are much more
numerous than the European forms. Those from the lower
Tertiaries had both a more complete dentition and also a greater
number of toes, recalling in this respect the genus Coryphodon
(§ 25) ; but as we study the forms which occur in the higher
Tertiary strata we find a gradual loss first of the fifth, then of
the second and fourth toes until the third alone is left
with the rudiments referred to above. The earlier Equida3
were small, about the size of a fox, but they gained in size

174

HIGH SCHOOL ZOOLOGY.

during the Tertiary period until they attained the stature of the
horses of the present day.

29. The great bulk of the Ungulates belong to the order
Artiodactyla, in which the third and fourth toes equally
support the weight of the body. Here we have also primitive
forms, and specialised foiins adapted for rapid locomotion ; the
primitive forms being, as in the last group, swamp-loving or
aquatic creatures, with comparatively hairless skin, and with
teeth much more nearly approaching the tuberculate type than
do those of the more specialised forms. As far as the dentition
is concerned, the swine are the most primitive of the living
species, but the Hippopotamus is supported by all four toes, and
therefore, in this respect, it is the more primitive form.

Fi.?. 115.— Reduction of the lateral toes, and coalescence of metapodials into a can-
non-bone in Artiodactyla. (After Gaudry.)

A, pig; B, Hycemoschus ; C, roe; D, antelope (Calotragus); E, sheep; P,
embryo calf.

These constitute two families, the Hippopotamidce and the Suidce,
which differ from the remaining Artiodactyla in not chewing the cud.
The first family has only a single genus, which, at the present day, is

HIGH SCHOOL ZOOLOGY. 175

represented by one or two species in the rivers of Africa. Their denti-
tion is singular, for although the milk teeth are if, oJ> m|, the adults
have only if, c\, nig, there being no permanent successors for one of the
milk incisors and one of the milk molars. The permanent front teeth
are tusk-like, the incisors being straight, while the canines are curved,
and meet each other in such a way, that the posterior faces of the much
larger lower ones are ground flat against the anterior faces of the upper
ones.

The second family has many more representatives, and a much less
limited geographical distribution, for there are several Old World
genera, as well as the Peccaries, which are peculiar to the New World.
The skin in all is more or less closely beset with bristles, their bodies
are more elongated, and thus better adapted for rapid locomotion, and
they are supported solely by the third and fourth toes ; the second
and fifth, although they are complete and furnished with hoofs, not
reaching the ground. (Fig. 115 — A.)

The Peccary even offers a further reduction in the hind foot, for
the fifth toe there is undeveloped. This genus (Dicotyles) is in
many respects the most specialised of the family, for apart from
the structure of the hind foot, and a reduction in the number of incisors
and molars, the stomach resembles in its complexity that of the
Ruminants. On the other hand, the genus Sus is the most primitive, for
its dentition is if, c{, pmf, inf, whereas in the other genera, there is
either a reduction in the number of the incisors or molars, or both.
The canines are generally tusk-like, the lower ones being the chief
weapons in the family, but the upper ones may also attain a formid-
able size, as in the pig deer— ^Babyrussa — of the Moluccas (Porcus),
where they are curved upwards and backwards ; the incisors are small
and sometimes absent in the adult, as in the pigmy hog (Porcula) of
India, and the wart-hog (Phacochcerns) of Africa, but the molars are
always of a tuberculate pattern.

30. The foregoing families constitute the non-ruminant sec-
tion of the Artiodactyla; all the other numerous genera are
ruminant forms, the stomach being complex, so as to admit of
their characteristic way of feeding. This and the reduction of
the second and fifth toes are both to be regarded as subservient
to the more rapid locomotion in this group, for these herbivora,
which are the chief objects of pursuit hj the larger carnivores,

176 HIGH SCHOOL ZOOLOGY.

are able to secure and to bolt, without previous mastication, in
a very short time, a large amount of food, which they after-
wards masticate when they have got to some secure retreat.
The mechanism concerned may be studied in the sheep's
stomach, where the cardiac end has two compartments, the larger
Rumen (paunch), and the smaller Reticulum (honey comb), while
the pyloric end has similarly two compartments, the Psalterium
(manyplies), and the Abomasum (rennet stomach). The
oesophagus is attached between the rumen and the reticulum,
and the grass which is hastily swallowed passes first into these
compartments ; it is then moved from one to the other, and
finally thrown back into the mouth and subjected to a thorough
mastication and insalivation, after which the semi-fluid product
is again swallowed and strained off into the abomasum and in-
testine, through the psalterium, which is connected indirectly
with the oesophagus by a half-groove on the wall of the
reticulum, capable of being converted into a complete channel.
A peculiar dentition accompanies the ruminant stomach ; in
the typical forms it is i§, c^, m§, there being only a pad in the
upper jaw, against which the lower incisors and incisor-like
canines bite. A wide gap separates the front teeth from the
molars, which have flat crowns with semilunar folds of enamel
on the surface. Such teeth are therefore said to belong to
selenodont forms, in contradistinction
to the tuberculate teeth of bunodont
forms, but it is obvious (as in the
Hippopotamus, e.g.,) that a tuberculate
tooth when worn down may present a Fig. ii6. -Molars from the up-

„ v i, n i i ,i per jaw of Bunodont and Seleno-

peculiar pattern ot enamel, and there- dont fossil Artiodactyia, Palceo-
fore bunodont forms are regarded as choerus and XiPhodon'
more primitive (Fig. 116).

The feet are also different in their structure in the ruminant
forms, for not only are the second and fifth toes raised off the
ground, becoming dew-claws, but they often disappear, and

HIGH SCHOOL ZOOLOGY. 177

the weight of the body rests entirely on the tips of the
third and fourth toes, being transmitted to them through a
cannon bone, which is formed by the more or less complete
coalescence of the third and fourth metapodials (Figs. 115 and
110 O). There are generally horns in this group, often con-
fined, however, to the male sex; when there are no horns,
tusk-like canines may serve as compensatory weapons of de-
fence. The sheep, oxen, antelope and deer are the typical
ruminants, but there are some aberrant families which we may
shortly consider first.

Of these the Camelidce present some peculiar features ; for example,
the psalterium is absent ; the upper jaw in front is not destitute of teeth,
for it retains one of the upper incisors and the canine on each side,
which are absent in the ruminants : the canines, the upper especially, are
tusk-like and the molars are only £ Instead of walking on the tips of
the digits, they are digitigrade forms, all three joints resting on the
ground ; the hoofs are thus of no use in locomotion, a single or double
pad of skin being present on the under surface of the third and fourth
digits. There are no dew-claws, but the third and fourth metapodials have
not so completely coalesced as in the oxen. The geographical distribution
of the family has the same peculiarity which we have noted of certain
other groups, there being both Old and New World representatives, quite
isolated from each other at the present day. In the Old World the genus
Camelus only occurs in a domesticated condition, as the Dromedary and
the Bactrian Camel, the former in Arabia, Africa, and India, the latter
(the two-humped camel), in the Mongolian table-lands. Both are used
as beasts of burden, and it is likely that the humps are the result of their
employment as such. There is only a single cushion underneath the
digits, which, therefore, present a suitable surface for the sandy soil of
the desert. In the New World, on the other hand, there are both wild
and domesticated forms belonging to the genus Auchenia ; these are
smaller sized forms without a hump, they tread on a double pad,
have fewer molars and larger ears than the camel. The wild species are
the larger Huanaco, and the smaller Vicuna ; the domesticated forms, the
Llama (the beast of burden of the mountain regions of Peru), and the
Alpaca, which is kept in herds for its flesh and its wool. The explanation
for the existence of the two branches of this family is to be sought in the
Miocene Strata of America, where numerous remains of Camelidae are

178 HIGH SCHOOL ZOOLOGY.

found, with complete f roflt teeth, and separate metapodials. The
descendants of these must have made their way into the Old World by a
bridge which existed between North America and Asia, and which after-
wards subsided so as to form Behring Straits.

Like the Camelidce, the pigmy deer of Java and West Af rica ( Tragu-
lidce) have tusk-like upper canines in the males and only three compart-
ments of the stomach ; their metapodials are less completely coalesced
than in the camels. In size and in the possession of tusk-like canines,
the musk-deer of Central Asia (Moschus) resemble the pigmy deer, but
the male has a peculiar musk-gland on the skin of the ventral surface.

A fourth group is that of the Giraffes (Camelopardalis) an African
form much nearer the typical Ruminants than any of the foregoing.
They differ from them both in the general form, and in the horns, which
are skin-bones covered with soft skin, the most primitive of the horns
of the ruminants.

32. It is according to the nature of these structures, that we subdivide
the typical Ruminants into the hollow-horned (Cavicornia) and the ant-
lered forms (Cervidce). In the former, projections of the frontal bones
form the so-called cores, which are covered with the variously-shaped but
usually unbranched horn, in the latter, the frontal bones bear the ant-
lers, with an intervening ring of bone, the "rose," where the antlers are
broken off each year. The antlers are only covered by skin (the velvet)
while they are undergoing formation ; that process complete, the velvet
ia rubbed off, and the polished bone exposed. We noted that, in several
of the preceding families, only the males have tusk-like upper canines ;
in these forms, also, it is of common occurrence that the males only
should have the weapons of offence and defence in the shape of horns or
antlers. Among the Cervidce, the Reindeer or Caribou (Rangifer) is
singular in that both sexes have antlers, which like those of the Moose
(Alces) are broad and palmated in form. Those of the StagfC. Can-
adensis) as well as of the Virginia deer (Cariacus virginianus) carry
rounded branches.

Among the Cavicornia, the Prong-horn of the Western prairies (Antilo-
capra americana) is the only form with a tendency to branching of
the core. It comes nearest the Cervidce in this respect, as well as in the
fact that it casts its horns at intervals. It is usually classified with the
Antelopes, a sub -family "of the Cavicornia, whose headquarters are
Africa, buj which are less numerous in Europe and Asia. The only

HIGH SCHOOL ZOOLOGY. 179

other American Antelope is the Rocky Mountain goat {Haplocerus
americanus). A well-known European genus is the Alpine chamois
( Rupicapra), while the gazelle (Antilope dorcas) is a common North
African species. Some of the African antelopes approach the next sub-
family, the oxen (BovinaJ, in their proportions. This group embraces
the domestic ox (which includes various races probably derived from
several wild species), the humped zebu (Bos indicus) and two or three
other Indian species. Other genera are the Old World buffalo (Bubalus),
the European and American bi>on, the yak of Thibet (Pqephagus) and
the musk-ox of the Arctic regions (Onibos moschatus). A third sub-
family (Ovina) embraces the sheep, which are found wild on high moun-
tain ranges, e.g., the bighorn (O. montana) of the Rocky Mountains and
the Argali of Central Asia, also the ibexes {Capra ibex) and goats (C.
hircus). Our domestic sheep are probably derived from one of the
Asiatic forms.

33. We must now turn to the Unguiculate orders, looking in
the first place somewhat more closely* into the classification of
the Carnivora, one form of which has been already studied.

Of the six families recognized in this order, the Ursidaz is least special-
ised ; it embraces plantigrade forms, with a dentition in which the sectorial
teeth are not prominent, and which are frequently omnivorous. Examples
of these are the kinkajou of Brazil with its prehensile tail (Cercoleptes),
the racoon (Procyon lotor) and the true bears ( Ursus). Nearest to these
are the badgers ( Taxklea) and skunks {Mephitis), which form a plantigrade
section of the weasel family (Mustelidce), to which there also belong
the chief fur-bearing animals of North America, the martens (Mustela),
minks and ermines (Putorius), wolverines (Gulo), otters (Lutra), and sea-
otters (Enhydra). The third family ( Viverridce), embracing the civet
cats and the ichneumons (Herpestes), is chiefly an Old World family, as is
that of the Hycenidce, but the dogs (Canidce) and cats {Felidce) are abund-
antly represented on both continents, the former embracing the dogs,
foxes, wolves and jackals ; the latter, the lions, tigers, leopards, lynxes
and cats of the Old WTorld, and the pumas, ounces and lynxes of the
New.

34. A very interesting branch of the Carnivora is that of the
Pinnipedia often placed in an independent order, and much
modified in accordance with their aquatic mode of life. There
is a marked tendency in this group, which contains the Seals,

180

HIGH SCHOOL ZOOLOGY.

Walrus, etc., towards the reduction in number of the incisor
teeth j the canines are rarely tusk-like, and the extremities are
converted into nippers, the hinder ones being turned backwards
parallel with the short tail (Fig. 1 1 6). The seals proper are those

Fig. 116.— Skeleton of Seal,
vc. cervical, vd. dorsal, vl. lumbar, s. sacral, vca. caudal regions of vertebral column ;
h. humerus; r. radius; c. carpus; me. metacarpus ; ph. phalanges; sc. scapula; co,
ribs.

which are least adapted for locomotion on land ; the walruses and
sea-lions, on the other hand, can raise themselves off the ground
by the aid of their limbs, and the nippers of the sea-lions even
have divisions, corresponding to the toes. As a rule there is
no external ear, the head is rounded, and the cylindrical body
diminishes in girth towards the tail.

Of the three families distinguished, that containing the eared-seals
(Otarice), is nearest such Carnivora as the sea-otter, the structure of
the flippers and their habits suggesting a less perfect adaptation to an
aquatic life than we meet with in the seals proper. In most of the
species the coat is formed of stiff, bristly hairs alone, but in several,
such as the Alaska fur-seals (Callorhinus ursina), the bristles are scarcer,
and there is a thick, soft under- wool. These skins, when dried and the
bristles removed, yield the valuable seal-skin furs, bnt the skin of the
seal is also sought after for other purposes, and the blubber of all the
species yields a valuable oil. Some of the Otariae, such as the California
sea-lion (Eumetopias Sttlleri), reach the large size of fifteen feet. The
other species are smaller,

HIGH SCHOOL ZOOLOGY. l&l

The Phocidce chiefly differ from the above in the absence of external
ears and the shape of the flippers, those of the hinder extremities being
especially remarkable on account of their notched outline, due to the
shortness of the middle and the length of the inner and outer toes.
The harp seal of the St. Lawrence is one of the commonest species
(Phoca grcenlandica, Fig. 195), but there are some singular forms also in
this family, such as the hooded seal of the North Atlantic (Cystophora
cristata), and the gigantic sea-elephant of the Antarctic Ocean,
(C. proboscidea), which attains a length of twenty feet, and is distin-
guished by the prolongation of the nose into a proboscis. Some species
of the family live in land-locked seas, such as the Caspian and the
lakes of Newfoundland.

The "Walrus ( Trichechus rosmarus) is placed in a family by itself, char-
acterized by the enormous upper canine tusks, by the shape of the
trunk, which does not diminish in girth towards the loins, by approach-
ing the Phocidse, in respect to the absence of external ears, and the
Otariae, in the ability of the creatures to raise the body on the limbs,
and thus leave the sea, and even climb steep rocks so as to reach a
safe place above high water, where they may bask in the sun.

It is observed that the young sea-lions take somewhat unwill-
ingly to water, and swim at first awkwardly ; this is one indication,
among many others, that the Pinnipedia are a group of mammals
which have gradually acquired aquatic habits, and with them their
modified form. The same is thought to be true of the Sirenia, for fossil
forms have been found allying them to the terrestrial Ungulata. Great
uncertainty is felt by zoologists, however, as to the alliances of the
third group of aquatic mammalia — the Cetacea ; many, nevertheless,
think that these carnivorous aquatic forms may have been originally
more seal-like in form, and that the horizontal caudal fin had within it
the hard parts of the hinder extremities, of which hardly a trace is now
to be detected ; no fossils have yet been found to confirm this idea,
although various anatomical considerations render it probable.

35. In turning to the other orders of Unguiculate mammals,
we shall find some forms that exhibit more primitive features
than the Carnivores, others that are specialised for an aerial,
arboreal or subterranean life, as much as the Pinnipedia are for
a life in water.

182 HIGH SCHOOL ZOOLOGY.

36. As far as regards the dentition, the Insectivora are
certainly the most primitive ; they are also all plantigrade
forms, and have well-developed clavicles. The teeth are not
more numerous than in the Carnivores, but the canine
tooth does not assume the function which it has in most
mammals, sometimes an incisor, sometimes a premolar, project-
ing further from the jaw than it does itself. Seven molars are
by no means always present, but their surfaces are always
tuberculate, in accordance with the insect-food.

Between groups of Rodentia and Insectivora, which corres-
pond in their habits, a certain superficial resemblance is to be
detected, a convergence of character which we attribute to the
influence of their surroundings, but the Rodents, as we shall
learn, including about one-third of all the species of mammals,
offer a greater wealth of form than we find in the Insectivora.
To these two orders belong all the smaller species of Mammalia,
and, indeed, parallel groups of both orders are to be be found,
some adapted for a life on the surface of the ground, some for
burrowing underneath it, some for a semi-aquatic, and some for
a more or less completely arboreal life.

Only two out of the six families are represented in our region, the
Shrews {Sorlcidce), and the Moles ( Talpidce). The former are mouse-like
Insectivora with an elongated muzzle, and a short velvety coat. In both
the common forms, the eyes are small, and in one {Sorex platyrhinus) the
ears and tail are long, while, in the other {Blarina brevicauda), both are
short. Both of these are terrestial species, but an aquatic genus
(Myogale), in which the toes are webbed and which has a very penetrating
musky odour, is found in South-east Russia and the Pyrenees. In all, the
hinder feet are larger than the fore, but, in the Talpidae, the fore feet are
converted into broad shovel-like structures, with short toes and stout
claws for digging the burrows in which they live (Fig. 1 10M) ; the limbs are
very short, the body elongated and cylindrical in outline, the head very
small, without either evident eyes or ears. The shape of the body is ob-
viously adapted to the underground life, and the snout is provided with
extremely delicate tactile sensibility. This is best seen in the Star-nosed
moles (Condylura cristata), where the fleshy disc at the end is divided

HIGH SCHOOL ZOOLOGY. 183

up into projecting rays ; in the other genera, Scalops and Scapanus,
the Common and Hairy -tailed Moles, the snout is simply pointed.

The other families are confined to the Old World ; their typical genera
are Erinaceus, the European hedge-hog, a terrestrial form in which the
hairs are converted into stout spines ; it protects itself by rolling itself
into a ball, and thus causing the spines to diverge from each other. In
another family, to which the Centetes of Madagascar belongs, the spines
are replaced by bristles, which, with the pointed snout and strong lower
canines, give the creature some resemblance to a miniature pig. The
Malayan genus Tupaja and its allies are arboreal insectivores with the
soft fur and habits of squirrels, and, in the same region, a singular genus,
Galeopithecus, is to be met with, provided with a patagium like our
flying squirrels. It is the representative of an independent family, as
is also the African Macroscelides, marked by the length of the hind
limbs, like the Jerboa, and occurring, like it, in rocky and desert regions.

37. The chief contrast between the Insectivora and Rodent ia
is in the nature of the food, and the difference in structure and
habit brought about thereby. Nowhere is the difference in
structure more evident than in the dentition, where the incisors
are reduced in number, grow from persistent pulps, and
acquire a chisel-shaped edge, from having the enamel only on
the anterior surface. Generally the incisors are only i, but in
the hares and rabbits (Lepus), there is a small tooth behind each
of the curved upper incisors ; the canines are always absent, and
the molars never tuberculate, but provided with transverse folds
of enamel. As in the Herbivora, the stomach is constricted into
cardiac and pyloric chambers, and each of these may have re-
cesses ; further, the alimentary canal is long in proportion to the
body.

Nearly half of our N. American Mammalia are Rodents belonging to
seven families, the Leporidce, Hystrichidos, Muridce, Dipodidaz, Geomy-
idee, Castoridce, Sciuridce. The first of these includes the hares and rab-
bits, and is sufficiently characterized by its dentition. The type of the
second is the Old World Porcupine (Hystrix), represented in N. America
by the common porcupine (Erethizon). Both of these forms have spines,
which are more efficient weapons of defence than those of the hedgehog,

184 HIGH SCHOOL ZOOLOGY.

on account of the ease with which they can be detached from the skin.
To the Muridce belong the rats and mice ( Mus), as well as the field-mice
(Arvicola) and the aquatic musk-rat {Fiber). An interesting northern
genus is the lemming (Myodes), which often migrates in vast numbers
from one part to another in Northern Europe and Asia. The Dipodidm
include the Egyptian Jerboa (Dipus), marked by the length of the hind
legs ; the same peculiarity is present but less developed in the American
jumping mouse (Zapus). In the Western prairies, two genera of pouched
gophers are met with, which constitute the family Geomyidce. They have
cheek -pouches which open on the cheeks outside the mouth, and are lined
with hair. As the gophers are burrowing forms, the fore feet are large
and armed with strong curved claws. The most truly aquatic of the
Rodents is undoubtedly the beaver (Castor fiber), the largest of our
species. As in the musk-rat, the hind toes are elongated and web-
bed, and the flat, scaly tail is very characteristic. The last family
— the Sciuridce — includes several genera, chiefly arboreal forms with soft
fur, and more numerous molars than the preceding, except the hares.
Among those which are distinctly terrestrial in their habits, may be
mentioned the gophers and prairie-dogs, while the chipmunk and the
woodchuck are intermediate, in this respect, between these and the true
arboreal squirrels and flying squirrels. The completely terrestrial forms
have cheek-pouches which open into the buccal cavity ; these are best
developed in the gopher (Spermophilus) and the chipmunk ( Tamias),
while they are rudimentary in the prairie-dog (Cynomys), and absent in
the woodchuck (Arctomys) and the squirrel (Sciurus and Sciuropterus).
The last-mentioned genus includes the nocturnal flying squirrels, which
have a patagium stretching from the fore to the hind limbs and permit-
ting a slanting leap, such as we have already observed to be possible in
several mammalian orders.

As representatives of tropical families, may be mentioned the Chin-
chilla of Chili and Peru, valued for its grayish fur, the Guinea-pig
(Cavia cobaya, now only known in the domesticated condition), the Capy-
bara (Hydrochcerus, the largest Rodent), the Paca (Cazlogenys) and Agouti
{Dasyprocta) of Northern South America, which four genera have almost
hoof -like nails, and, like most of the Rodents, are gregarious in their
habits.

38. On the approach of cold weather many animals of differ-
ent classes pass through a resting phase, which, in the warm-
blooded animals, is usually spoken of as hybernation. This

HIGH SCHOOL ZOOLOGY.

185

phenomenon ocelli's in several orders of Mammalia, but nowhere
is it more easily studied than in the Rodents. During this
period the various functional activities are arrested as much
as possible ; there is no food taken and little tissue consumed,
so that, as respiration is also very inactive, the body temperature
is assimilated to that of the surrounding medium, and thus the
warm-blooded animals become temporarily cold-blooded.

39. After the Rodents, the greatest number of mammalian
species belong to the bats — Chiroptera — our next order. Here we
have a very different modification for aerial life than we have
hitherto met with ; instead of a patagium like that of the flying
squirrels, Galeopithecus and the Phalangers, certain of the
fingers and the fore-arm are much elongated, and serve to spread a
very delicate hairless web, which extends backward to the thighs
and frequently also surrounds the tail (Fig. 117). The thumb

Fig. 117.— Outline and skeleton of Phyllostoma (after T? Alton).
oa, humerus ; va, radius 'and ulna ; w, carpus ; I, pollex ; II— V, second to fifth fin-
gers ; m and f l 2 •% elongated metacarpals and phalanges ; zf, femur.

alone does not take any part in the support of the web, this being
chiefly effected by the third, fourth, and fifth fingers. Except
in the fruit bats, it is the only digit which bears a claw; in these,
however, the index also is clawed, although, like the other fingers,
it is entirely enveloped in the web. The web is very sensitive
13

186 HIGH SCHOOL ZOOLOGY.

and as the bats are nocturnal creatures, the nerve-terminations
in it constitute one of the chief channels through which sensa-
tions reach the brain. In further accordance with their noc-
turnal habits, the bats have small eyes, and large ears ; they
hybernate in cold climates, where they are often to be found in
large numbers, hanging in some cave or building, by the claws
of the hind feet, wrapped up in the patagium. The bats are
characteristically insectivorous forms, very few are fruit-eating,
but the dentition of the two groups indicates a sharp contrast
between them. As the patagium does not merely serve to break
the force of a fall or to permit of an oblique leap, but is a true
organ of flight, the pectoral muscles require to be specially
developed to permit of such use of the anterior extremity, and
consequently the sternum is provided with a crest, and the
clavicles are stronger than they are elsewhere among mammals.
It is not surprising that the bats should be the most widely
distributed of Mammalia.

The fruit-bats are abundant in eastern tropical countries, and attain
the largest size of any members of the order. Pteropus, the fox-bat, so
called on account of the pointed snout, may be mentioned as a type of
this section, the fruit-eating habits of which are indicated by the blunt
tubercles of the molars. In the insectivorous bats, on the other hand,
the tubercles of the molars are sharp or coalesce into a W-shaped
cutting edge. The snout is short, and the external ears are of large
size. Two groups are recognized — those in which the external nose is
provided with a membranous expansion round the nostrils, and those in
which there is no such membranous expansion. To the former belong
the vampire-bats of S. America (Desmodus), which attack and suck the
blood of horses and mules. With that exception, they are mostly insect-
eating forms, but the genus Vampyrus of Guiana lives chiefly on
fruit. The ordinary bats ( Vespertilionidce), with the nose destitute of
the membrane, are represented by two genera in our region, as examples
of which may be mentioned the little brown bat ( Vespertilio subulatus)
and the red bat (Atalapha noveboracensis).

40. As the Australian continent is peopled by a remarkably
primitive mammalian fauna, so also the Island of Madagascar
characteristic mammals which are found nowhere else,

HIGH SCHOOL ZOOLOGY. 187

and which occupy, in some respects, a comparatively low place
among the unguiculate Eutheria. With few exceptions the
mammals of Madagascar belong to the order Prosimii, and the
members of this order are also, with few exceptions, confined to
Madagascar and the neighbouring parts of the Continent of
Africa. As well the fact, however, that there are certain out-
lying members of the order in the Malay Archipelago and
India, and that fossil remains have been found in various parts
of the world indicate that their geographical distribution was
not always so restricted. They are completely arboreal forms,
the inner digits of both fore and hind feet being opposable, and
thus forming thumbs. On this account, they were long asso-
ciated with the monkeys under the ordinal name Quadrumana,
but it is more convenient to consider them apart from the mon-
keys, although they are undoubtedly allied in some respects to
them. Their dentition is peculiar, the incisors being §, or re-
duced in number, the canines absent in a rodent-like genus
(Chiromys), and the molars tuberculate like those of the Insec-
tivora, but they do not confine themselves to insect food, living
also upon smaller Vertebrates, fruit, etc. The second digit of the
hind limb is always clawed, while the other digits bear nails,
such as those of the monkeys. Most of them are nocturnal
creatures which have a soft warm coat, and often a bushy tail.

Two families are formed for the reception of the aberrant genera Tar-
dus and Chiromys. The former is found living socially in the woods of
Borneo, and has received its name from the great length of the tarsus. It
is also singular on account of the enormous size of the eyes. The Chiromys
is the Aye- Aye of Madagascar, a form which picks out larvae from
the trees on which it lives, by means of an extraordinarily thin finger
(the third), which it inserts into their burrows. Its rodent-like incis-
ors suggest that its food is not confined to larvae.

The third family Lemuridce includes all the other genera, some of which
are very bizarre creatures. The Loris {Stenops, &c.) somewhat resemble
the Spectres (Tarsius) in their distribution and habits. The Galagos are
carnivorous creatures which vary from the size of a rabbit to that of a

188 HIGH SCHOOL ZOOLOGY.

mouse, while the Lemurs proper are of large size, attaining in the case of
the tailless Indri (Lichanotus) nearly three feet in length. The other
Lemurs are smaller in size and provided with a long tail which is coiled
about them for warmth, while they rest during the day. In Propi-
thecus the snout is short as in the Indri, the result being a monkey-like
face, while in the ring- tailed lemur (L. catta) and its allies, the snout is
prolonged.

41. However monkey-like certain of the lemurs are, they
form a decidedly more primitive group than that of the
monkeys proper. This is especially noticeable in the structure
of the brain, the cerebellum being left uncovered by the cere-
brum in the former group, while, in the latter, the hinder lobe
of the cerebrum is so developed as to overlap the cerebellum
entirely. In this respect, as well as many other anatomical fea-
tures, the monkeys agree in structure with Man, and, accord-
ingly, they are generally placed together in the order Primates,
in spite of the exceptional place which Man otherwise occupies
in nature. In all Primates the incisors are f , the inner digits
(thumb and great toe) are opposable (except in man, where this
is only true of the thumb), and all the fingers are nailed, not
clawed. The orbits, which have complete bony walls, are di-
rected forwards, and the face, in comparison with the Lemuroids,
is hairless.

Apart from Man, three families
of Primates are recognized, two of
which are New World groups.
Most of the S. American monkeys
belong to the Platyrrhini, so called
on account of the width of the
septum of the nostrils, which
causes these apertures to look
outwards. The tail is usually
prehensile, assisting in their ar-
^ boreal life in the dense forests

Fig.ll8-TheUakari.-JBrac%«^ca^.which ^ inhabit ^ they differ
Asan example of the Platyrrhini. from both the other famili«s in

(From Brehm.)

HIGH SCHOOL ZOOLOGY. 189

having an extra molar tooth, and a rounded skull. Examples of
this group are the howling and spider monkeys (Mycetes and Ateles),
the bonnet-monkeys {Cebus), and certain smaller squirrel-like forms,
with soft, abundant fur, and nocturnal habits, which depend upon
their feet alone for climbing {Nyctipithecus, Chrysothrix). The re-
maining South and Central American forms are called Arctopitheci;
they have one true molar less than the Platyrrhines, tuberculate
grinders, and fingers with claws instead of nails. Only one genus is
recognized (Hapale), including several species of marmosets, the smallest
of the Primates.

The Old World monkeys (Catarhlni) have a thin nasal septum, the
nostrils directed downwards and forwards, the same dental formula as
Man, (if, c\, pm|, m|) and the tail, if present, never prehensile. There
are two groups of them, those that approach Man (Antkropomorpha) in
the absence of the tail and of cheek-pouches, as well as in the less
prominence of the face, and the greater length of the anterior limbs, and
those that approach the Carnivora (Cynomorpha) in the strength of the
facial region, and the development of tusk-like canines, while they differ
from the other group in having shorter anterior limbs, and, very often,
cheek-pouches. To the Anthropomorpha belong the chimpanzee
and the gorilla of Western Africa ( Troglodytes), the orang-utan, {Simia
satyrus) of Borneo and Sumatra, and the gibbons (Hylobates) of the
same islands and the continent of India. To the Cynomorpha belong
forms generally of smaller size, such as the sacred monkey of the
Hindoos (Semnopithecus), the African Colobus, the squirrel-like Cerco-
pitheci of Africa, the macaques. (Macacus — chiefly Asiatic, with the ex-
ception of the tailless macaque, M. ecaiidatus, of North Africa, which is
preserved in Gibraltar), and the baboons, which are the most dog-like
in face of the Cynomorpha, and include, among the African species,
very large forms.

ltO HIGH SCHOOL ZOOLOGY.

CHAPTER VIL
The Arthropoda.

1. It was stated in Chapter I., that the term Invertebrata in-
cludes several distinct sub-kingdoms, resembling each other
in that they do not possess the arrangement of the nervous
system and skeleton typical for the Vertebrates. It must not
be understood that all are equally unlike Vertebrates, some
worms for example, seem to foreshadow in their structure the
vertebrate organization, but the most highly organized Inverte-
brates— the Arthropoda — diverge very widely from the type of
structure which we have studied heretofore, although their
organs are built up of histological elements, similar, in many
respects, to those of the Vertebrates. The nature and extent of
the divergence referred to may be studied in the crayfish, an
Arthropod which forms a suitable introduction to the sub-
kingdom to which it belongs, both on account of its size and on
account of its position in the group.

2. The Arthropoda are bilaterally segmented animals like the
Vertebrates, but, unlike them, their segmentation is visible on
the surface of the body, especially on ae count of the fact (from
which the group derives its name) that each segment may carry
one pair of jointed appendages. Throughout the sub-kingdom
the rule holds good which obtains also in the Vertebrates, that,
in the more primitive families, the segments are not only more
numerous but less constant in number, and show less tendency
to be grouped into dissimilar regions. The nervous system par-
takes in the segmentation of the body, but is situated on the
ventral aspect, while the centre of the blood-vascular system is
dorsal, so that there is a complete reversal of the neural and

HIGH SCHOOL ZOOLOGY.

191

haemal aspects, as compared with the Vertebrates (Fig. 119) ;
nevertheless, it is the neural aspect which is first developed in
both sub-kingdoms. No endoskeleton affords attachment to the
muscles of the body or protects the delicate organs, but this is
functionally replaced by an exoskeleton of chitin, a hard sub-
stance of peculiar chemical composition, secreted by the skin,
and sometimes rendered harder by the admixture of calcareous
salts.

Fig. 119.— Diagram of transections through the abdominal regions of a catfish and
a crayfish, to show the relative position of nervous system, N, and intestine, I.
D, dorsal ; V, ventral surface ; E, endoskeleton ; B, aorta ; K, kidney. «

3. The last peculiarity is especially met with in the Crustacea,
one of the four Arthropod classes, and that to which the crayfish
belongs. The other classes (Insecta, Arachnida, Myriapoda)
embrace chiefly air-breathing Arthropods, whilst almost all
Crustacea are aquatic, so that there is, on the whole, a marked
difference between the respiratory organs of the Crustacea and
those of the other classes.

Several species of crayfish or crawfish (old English crevish,
Fr. ecrevisse, Ger. Krebs) occur in Ontario ; one of the com-
monest near Toronto is Cambarus robustus, Girard, (Fig. 120),

102

HIGH SCHOOL ZOOLOGY.

Fig. 120.— Cambarus robustus. (Girard).
but all are included in the genus Cambarus, while those on the
Pacific slope of the Rocky Mountains, as well as the European
crayfishes, belong to an allied genus, Astacus. This genus giv< s
its name to the family Astacidae, which includes the lobster
(Homarus americanus), the marine representative of the crayfish.
Any species will serve for making out the arthropodous charac-
ters already mentioned, as well as those peculiar to the Crustacea
which follow.

4. Twenty segments, of which only the last (telson) is desti-
tute of a pair of appendages, are invariably present in the group
of Crustacea, to which the crayfish belongs, and these are

HIGH SCHOOL ZOOLOGY. 193

grouped in three regions, of which the head contains five, the
thorax eight and the abdomen seven. On account of the ex-
tent to which a segment from one region differs from that from
another, the segmentation is styled heteronymous, hut the same
fundamental plan of structure may be observed in all. The
abdominal segments are independent, but the segments of the
head and thorax are coalesced with each other into a cephalo-
thorax, the fusion being more complete on the dorsal surface.
Behind a line which marks off the cephalothorax into anterior
and posterior regions, each side of the thorax is provided with
a flap of skin which acts as a gill-cover, forming a cavity in
which the gills, attached to the bases of the thoracic legs, are
sheltered.

5. It will be convenient to study one of the hinder pairs of
abdominal appendages first ; they are biramous, consisting of
a basal part, with two branches, internal {endopodite) and ex-
ternal {exopodite). Those of the sixth pair are modified with
the telson into the caudal fin ; while the first and second pairs
are different in the two sexes.

Of the eight pairs of thoracic legs, the three foremost are
turned forward as the foot-jaws (maxillipedes) to assist in
securing food, while the five hindmost are the walking legs.
Comparing these with the abdominal appendages, we find that
although the endopodite is large in all, the exopodite is only
present in the foot-jaws, while, with the exception of the
eighth pair, all the thoracic appendages have in addition a
membranous flap — the epipodite — concealed within the gill-
chamber, and carrying, with the exception of the first, gill-
filaments. There are thus six gills of this nature on each side ;
the other gills are attached to the soft membrane which con-
nects the legs to the thorax, and there are eleven of these on
each side, the third to the seventh appendages each carrying
two, while the second has only one. The fourth pair of tho-

194 HIGH SCHOOL ZOOLOGY.

racic legs — the great claws — are adapted for prehension ; they,
like the fifth and sixth, are chelate, i.e., the penultimate joint
is prolonged so as to be opposed to the terminal joint.

Of the five pairs of head-appendages, the two anterior
(antennulce and antennae) are sensory, while the three poste-
rior (the mandibles and the maxillce) are related to the mouth-
aperture as jaws. The second pair of niaxillse most closely re-
semble the foot-jaws, but the exopodite and epipodite of each
are united into a spoon-shaped flap, which lies in the anterior
narrow aperture of the gill-cavity, and, by its movements, ere*
ates a current of water, which flows outward through that aper-
ture. In both pairs of maxillae as well as in the mandibles, the
endopodites are feeler-like (palps), while it is the basal segments
which are flattened and approximated to the mouth-aperture,
those of the mandibles alone being hardened for cutting. Neither
exopodites nor epipodites are present in the mandibles or first
pair of maxillae. On the other hand, both of the foremost ap-
pendages are biramous, the exopodites of the antennae being,
however, mere scales, while those of the antennulae are similar
to the endopodites. On the basal joints of the antennae and
antennulae, respectively, are to be seen the apertures of the
green glands or kidneys and of the ears to be afterwards de-
scribed.

6. Having inspected the outward form of the body, we must
now glance at the various systems of organs. It will be ob-
served that the chitinous cuticle remains soft where movements
are necessary, and that it is most densely calcified where it
meets with the greatest strain, as e.g., in the chelae and
mandibles.

7. The muscles are formed of very plainly striped tissue;
indeed the histology of this tissue can be more easily studied
here than in the catfish (I, 8). The muscular bundles are at-
tached to ingrowths of the exoskeleton, which can be seen very

HIGH SCHOOL ZOOLOGY.

195

well in the chelae and elsewhere,
the ventral nervous system.

Similar ingrowths protect

8. We distinguish in the nervous system,
the brain and ventral nerve-cord, the latter
composed of a chain of paired ganglia, con-
nected by longitudinal commissures. Of such
ganglia the last eleven segments in front of

| the telson have each one pair, but the ganglia
of the five segments in front of these have
coalesced into an infracesophageal ganglionic
mass. This is united to the brain, or supra-
cesophageal ganglia, by commissures which
lie at either side of the oesophagus. The
brain supplies nerves to the eyes and an-
tennae. All of the nerves in the crayfish, as
well as other Invertebrates, are of the non-
medullated type.

9. An examination of the sense-organs
shows that they differ both in position and
structure from those of Vertebrates. The
eyes are elevated in this order of Crustacea
(Podophthalmata) on movable stalks, and
they are of the compound type so character-
istic of most Arthropods (Fig. 121).

II n.

The stalk is partly occupied by muscles, but

oSLTdium^mThfeye chiefly by ganglionic expansions of the optic nerve,
of the Crayfish ; c, cu'ti- from the outermost of which the nerve-fibres pass
cular facet formed by un- „ , , , , , , . ,,

derlying hypodermal off through a basement membrane to end m the

cells ch ; p, pigment cells modified epidermal cells which constitute the eyes,
surrounding the retino- r t J

phoral cells and cc, the These cells are disposed in three zones, the outer-

faa^rh.1 rhabdo'me^ bm most of which secrete the cuticular facets of the

basement membrane ; n, eve . each facet corresponds to an element (om-

matidium) of the compound eye, and is formed by

two cells of the outermost zone j underneath these are the four retino-

196 HIGH SCHOOL ZOOLOGY.

phoral cells, (surrounded by four pigment cells), which secrete the crys-
talline cone, and this is prolonged inwards into a tube (formed by seven
cells of the innermost zone— the retinulse), of which it forms a spindle-
shaped core — the rhabdome. The nerve fibre to each ommatidium oc-
cupies the axis of the rhabdome and of the crystalline cone ; the cones,
therefore, constitute the sensitive elements of the eye, like the rods
and cones of the Vertebrates.

Auditory sacs are present in the basal joints of the anten-
nulse. They contain foreign particles, which play the part of
otoliths (I, 46), and the sensitive elements are stiff hairs in
which nerve-fibres terminate. Both pairs of feelers obviously
act as tactile organs, but peculiar setae on the outer branches
of the antennulse have been interpreted as olfactory in function.

When the various jaws have been removed, the mouth is
exposed, bounded in front and behind by unpaired chitinous
outgrowths, the labrum and metastoma. The chitinous cuticle
is continued into the spacious stomach, where it forms numerous
calcified teeth, of use in comminuting the food. Digestive
juices are furnished by the so-called liver, a bulky tubular
gland which lies above and behind the stomach, and which
opens into the mid-gut, the only part of the intestine destitute of
chitin. Behind this is the straight rectum, the lining of which
becomes continuous with the cuticle at the anus.

10. In comparison with the Vertebrates, the Arthropods have
a less complete blood-vascular system, for, during part of the
circulation, the blood flows in interspaces instead of closed
capillary vessels. These are, however, partly represented in the
crayfish, and the heart, as well as the arteries and veins, is
well developed (Fig. 122). The blood is driven out to the
whole system through the arteries, and is returned by venous
sinuses through the gills to the pericardial sac.

11. The female crayfish may be found in spring with eggs
attached to the abdominal appendages, to which the young ad-
here until they have attained the form of the adult. la the

HIGH SCHOOL ZOOLOGY.
b &

197

Fig. 122.— Diagram of circulation of Crayfish— a, heart in pericardium ; b, c, d, an-
terior, posterior, and ventral arteries.

lobster, as well as most other Crustacea, the young are freed
from the egg when they have attained three pairs of legs
(Nauplius-phase) ; they only arrive at the adult form after a
series of moults, and there is generally a complicated meta-
morphosis.

12. If we except a species of prawn (Paloemonetes) and another of
Opossum-shrimp (Mysis) found in the Upper Lakes, the Podophthalmata
are exclusively marine forms, including on the one hand the various
kinds of shrimps and prawns, which resemble the crayfish in the long
tail {Macrura), and on the other, the crabs {Brachyura), where the short
tail is tucked up under the cephalothorax. An intermediate group is
formed by the hermit-crabs (Paguridce), in which the cuticle of the
tail-segments never becomes calcified, and the creatures resort to empty
univalve shells for protection. An allied East Indian genus, the cocoa-
nut crab {Birgus latro), lives in holes in the earth, and, instead of
depending on its gills for respiration, uses the wall of the gill-cavity as
a lung. This is an instance of what is termed "change of function,"
a principle which must be borne in mind, in comparing the structure of
animals which are nearly allied in form, but different in habits.

1 3. Two other .orders of Crustacea, which resemble the cray-
fish in the number of the segments and the appendages, have
fresh-water representatives which are very common, although
the majority of both are marine. These are the Isopoda and
the Amphipoda ; but in both, only one of the eight pairs of
thoracic appendages is turned forwards toward the mouth.
The Isopods have the body depressed, while in the Amphipods
it is compressed. A familiar example of the former is the
water-slater, Asellus communis. (Fig. 123). It will be observed

19$

HIGH SCHOOL ZOOLOGY.

that the four hindmost abdominal segments
are coalesced above into a shield, from beneath
which the last pair of legs project. The three
pairs of legs in front of these serve for respira-
tion, and the eggs are carried in the female on the
under surface of the thoracic segments. Terrestrial
Isopods, like the common Wood-louse (Oniscus)
and its allies, exhibit an interesting adaptation for
breathing air ; one of the pairs of abdominal legs
being traversed by tubes which have the same
function as the tracheae of insects.

Among the marine Isopods several are temporary par-
^commmiii.xt18 asites adhering to the surface of fish ; others are perman-
ent parasites, which live in the gill- or body -cavity of
other Crustacea, and which consequently loose much of their resem-
blance to the free Isopods.

Of the fresh-water Amphipods species of a genus Gammarus

(Fig. 124), are everywhere to be
met -frith. The gills are on the
thoracic legs, the abdominal legs
being partly for swimming, and
partly for leaping. Species of an
allied genus, Pontiporeia, occur in
R* m.-Gammaru8 8V. x 3. tne Great Lakes; they are inter-
esting, like Mysis, because the other species are chiefly marine.
14. The lower orders (separated in a sub-class Entomostraca,
from the foregoing Malacostraca,) exhibit by no means the same
constancy in the number of segments which we meet with in
the higher, nearly allied forms often presenting considerable
differences in this respect. All of the orders except one — the
Cirripedia — have fresh- water representatives, which are for the
most part inconspicuous, often microscopic, creatures.

The most primitive forms, as well as the largest we have to
mention, belong to the Phyllopoda, a group in which all the
behind the head bear flat leaf-like swimming-legs.

HIGH SCHOOL ZOOLOGY.

199

A common form in spring pools is Branchipus vernalis

(Fig. 125), with eleven pairs of such

legs ; an allied genus, Artemia, is

very common in salt lakes. Other

genera are protected by a shell, which

swimming on its back. x 3. may ^ horse-shoe shaped as in Apus,

or formed of two valves as in Estheria. Such shells are also found

in another group of Phyllopods— the Cladocera or water-fleas —

(Fig. 126), in which there are only five pairs of legs, but which

Fig. 126— Daphnia pulex. x 18. Fig. 127.— Cypris Candida, x 16.

are otherwise marked by the large second pair of antennae
taking on a locomotive function. Another order, Ostracoda, in-
cludes forms with a still shorter post-cephalic region, for only
two pairs of legs are to be found behind the jaws (Fig. 127). The
Copepoda, however, have a much longer post-cephalic region
than this, there being five thoracic segments, the first of which
is coalesced with the head, and five abdominal segments term-
inating in a furca. The latter are footless, but the thoracic
segments bear biramous swimming feet, and the head-segments
the usual appendages, although the second pair of maxillae
separate on each side into two independent so-called foot-jaws,
which may undergo curious alterations. Many of the Copepoda
live a semi-parasitic or parasitic life ; in the free forms (Fig. 123),
the jaws are formed for biting, but in the parasitic forms, the
parts of the mouth are more or less converted for sucking or ad-
hesion (Figs. 129 and 130), in which the posterior antennae may
assist. As a rule the parasitic Copepoda do not appear to injure

200

HIGH SCHOOL ZOOLOGY.

much the creatures they attack, but one form, Argulus, which
attains the length of quarter of an inch, is found to kill the
whitefish in lakes in the North- West in immense numbers.

***$*.

Fig. 128.— Cyclops sp. x 12.

Fig. 129. -Ergasilus
with egg-sacs from
gills of sunfish X10

Fig. 130.— Ach-
theres from gills
of catfish x 6.

This form attaches itself by the anterior foot-jaws, which are
modified into suckers, but it is the piercing and sucking mouth
which injures the fish.

The remaining order — the Cirri-
pedia — has only marine forms, which
pass through an active larval phase,
but eventually attach themselves by
their heads and secrete a compli-
cated shell (Figs. 131 and 132). The
antennae are rudimentary, but three
pairs of jaws are present, and behind
these, six pairs of biramous feet,
which by their movements bring food

particles to the

mouth. These are,

however, absent in

certain parasitic

forms.

Fig. 131.— Shell of Balanus hamerk

Fig. 132. —Lepas anatifera.

HIGH SCHOOL ZOOLOGY.

201

15. On the Atlantic coast, from Nova Scotia southwards,
there occurs a very remarkable animal called, on account
of its shape, the horse-shoe crab, Limu-
lus polyphemus (Fig. 133), the body of
which is divisible into three regions —
cephalothorax, abdomen and caudal spine.
The first of these bears six pairs of leg-like
appendages, chiefly chelate, on either side
of the mouth, possibly equivalent to the
first six pairs of the Crustacean. The ab-
dominal appendages are present in five
pairs, the outer branches of which are
beset with gill-leaflets. Limulus passes
through a " Trilobite-phase" (Fig. 134), in
its development, so called on account of
its resemblance to the singular fossil Ar-
Limulus pohjphemxis. £. thropods, which were so abundant during
the Palaeozoic period. (Fig. 135).

Fig. 134.-Trilobite-j.:
of Limulus.

(After Kingsley).

Fig. 135.— Asaphhus Canadensis,
Chapman. Utica Formation.

16. Both the Trilobites and Limulus have generally been
considered as Crustacea, but many points in the structure and
14

202

HIGH SCHOOL ZOOLOGY.

Fig. 136.— Scorpio europceus,
with its combs and ocelli.

development of the latter seem to point to its being more closely

allied to the Arachnida. This resemblance is strongest to the

Scorpions (Fig. 136), a group of Arach-
nida confined to the warmer zones of

the Old and New Worlds. In these

the appendages of the cephalothorax

are similar to those of Limulus, the

first two pairs (chelicerae and pedipalpi)

acting as jaws and prehensile arms,

while the others are walking legs.

Respiration is performed by four pairs

of " lungs," which are cavities on the

third to the sixth abdominal segments,

containing leaflets that recall the gills

of Limulus, and opening by slits on the ventral surface.

Development shows that these lungs arise as infoldings at the

bases of appendages, and that they are homologous with the

gills of the horse-shoe crab. The abdomen differs from that
of the crayfish, in being differentiated into
two regions, a preabdomen of seven, and
a postabdomen of six segments, the last of
which terminates in a curved claw, per-
forated by the duct of a poison-gland.

The little book-scorpions (Chelifer) have no
poison -gland in the tail, nor is the abdomen sub-
divided into two regions ; they belong to an in-
dependent sub-order, the Pseudoscorpionina, as
do the daddy-long-legs (PJiaktngina), with their
short abdomen and long walking legs. Both of
these groups feed on minute insects and mites ;
with the Scorpions they form the order Artnro*
gastra.

17. Of the various orders of Arachnida,

ig. 137— Aqaiena nceoia, . . ••

v ith th e ocelli the g piders ( Aranema) and mites ( Acarina)

(Afcer Emerton). V \ / \ /

HIGH SCHOOL ZOOLOGY.

203

are the most important. Both have the two pairs of mouth-
appendages and the four pairs of walking legs, but the form of
the body is very different in the two groups, on account of
the separation of the abdomen in the spiders proper, by a
slender stalk, and the presence at its extremity of the spin-
nerets (Fig. 137).

Some of the chief structural peculiarities of the spiders
may be gathered from Fig. 138. The two-jointed chelicerae
terminate in a powerful claw, perforated by the duct of a

Fig. 138.— Diagrammatic section of a 'spider— Epeira. (After Emerton).

a, b, upper and lower lips ; c, oesophagus ; d, f, upper and lower muscles of the suck-
ing stomach ; «, stomach ; g, ligaments attached to diaphragm under the stomach ;
k, upper, j, lower, nerve-ganglion ; I, nerve to legs and palpi ; m, m, branches of stom-
ach ; n, poison-gland ; o, intestine ; p, heart; r, lung ; s, ovary; t, trachea ; u, spinning
glands.

poison-gland. Between the bases of the pedipalpi is the mouth,
which leads by an oesophagus into a sucking stomach, dilatable by
muscles, and provided with latei-al cceca. The abdominal part of
the intestine is provided with a liver, and with Malphigian tubes
(slender cceca arising from the hinder end of the intestine in
air-breathing Arthropods, and discharging the function of
kidneys). The heart is elongated like that of the scorpion and
of the lower Crustacea, but the nervous cord is concentrated
into the thorax. Above the oesophagus is the brain, which
sends nerves to the simple (not facetted) eyes, the arrangement
of which on the head is of great use to systematists. The
numerous lungs of the scorpion are only represented here by
two air-sacs (four in the trap-door spiders), while, in addition, a

204 HIGH SCHOOL ZOOLOGY.

pair of branching air-tubes, such as are universally present in
the insects, open further back near the spinnerets. These are
three pairs of projections, through short tubes on the ends of
which the spinning glands open. The secretion furnished by
these glands hardens on exposure to the air, and the threads so
formed are guided by the hind legs into the characteristic webs,
which serve as dwellings, or as traps for the prey, or even for
flight.

18. In the Mites, on the other hand, the abdomen and cephalothorax are
coalesced and unsegmented, while the mouth-appendages are frequently
much modified by the adoption of a parasitic mode of life. Some of the
Mites are parasitic on insects, during a larval stage, in which they have
only six legs, afterwards seeking their food on plants (Trombhlium).
Some are aquatic forms, which may live free (Hydrachna), or parasitic-
ally on fresh-water mussels (Atax). Others are temporary parasites, like
the ticks {Ixodes), but there are various forma which live a permanently
parasitic life in the plumage of birds (Dermaleichus), or in the skin of
mammals (Sarcoptes, Demodex). Finally, the cheese-mites and their
allies ( Tyroglyphus) have their mouth-parts adapted to the easy mode in
which they secure their food. Plants are not exempt from the attacks
of mites, for the species of one group (Phytoptus), in which the two
hinder pairs of legs are rudimentary, make minute galls in the leaves
of various plants.

The effect of the adoption of a parasitic mode of life is best seen in the
genus Pentastomum, a form destitute of appendages, except for two pairs
of hooks near the mouth, which lives in the nasal cavities of Carnivora.

With the exception of the larger mites and ticks, all of the above
forms have no special respiratory organs, and this is the case also with
the bear-animalcules ( Tardigrada) , a group of microscopic creatures living
in moss, and feeding on minute larvae or Rotifers. Like the latter, they
may be desiccated and revived by moisture. They are associated with
the Arachnida on account of the number of appendages, but the fourth
pair of legs occupies the hinder end of the body.

19. Apart from, such minute air-breathing Arthropods as are
referred to in the above paragraphs, all have respiratory organs,
consisting (with the exception of the lungs of the scorpions and
spiders) of branched air -tubes, communicating with the outside
by " stigmata," and introducing air into all the tissues of the

HIGH SCHOOL ZOOLOGY.

205

body. The walls of these tubes are delicate, but they are pre-
vented from collapsing by the presence of a strengthening, spiral,
chitinous fibre, just as, in the higher Vertebrates, the windpipe

0«-jo is by its cartilages.
.-e« They are, therefore,
«|« called tracheae, and

SHT^ the air-breathing Ar-
enas "5 , f

S"3> I thropods are hence
frequently spoken of
as the " tracheate" in
contradistinction to
the " branchiate" Ar-
thropods. Two groups
of the tracheate Ar-
thropods remain for
us to discuss — the
|i = x Insecta and the Myri-
=" £| | apoda. Although the
^•'5« latter contains the
-s §._'« most primitive forms,
•JjS | yet some knowledge
J; * |1 of a very accessible
~ =. " a member of the former

as s

Ss^o class — the red-legged

2* ® ^

f"-|| grasshopper — will

1 1 * S serve to introduce to

"5 ...

» = w o

a, a- 3
<j „« c

.►a- o

f -p C/3 rH

ca-'O

c = 3 r
5 a; s<sJ

1 O o 3

both.

20. Among sever-
al species of locusts
which are abundant
in the fields in the
there is none

ill! Wl-

"** g 2 g easier to obtain than

oH o

ShI tne sPecies above

206

HIGH SCHOOL ZOOLOGY.

named — Caloptenus femur-rubrum. Comparing it with the
crayfish, we find that there are conspicuous differences both as
to the number and grouping of the segments, and as to the
number and nature of the appendages. Instead of a cephalo-
thorax and abdomen, we find a head composed of four segments
(the number only to be arrived at from the appendages), a
thorax consisting of three free segments (pro- meso- and meta-
thorax), each of which bears a pair of walking legs, and the two
hindmost, each a pair of wings ; and finally, an abdomen of ten
segments without obvious appendages (Fig. 139).

21. In the abdomen, the exoskeleton of each segment is divi-
sible into a sternum below, a tergum above, and a lateral piece
on each side — the pleurum — coalesced with the tergum, and
only indicated by the stigmata. In the meta- and meso-
thorax (but not in the prothorax) a further differentiation is
associated with the attachment of the wings, for each tergum
or notum is subdivided into an anterior scutum and a posterior
scutellum, while the independent pleurum is subdivided on each
side into an anterior epimerum and a posterior episternum.
Only the sterna of the head-segments can be recognized, for
the dorsal part of the exoskeleton of the head (epicranium) be-
longs solely to the first segment.

The thoracic legs are formed of
the femur, tibia, and three-jointed
** tarsus," — these names must not be
supposed to indicate any homology
with the parts so-called in Verte-
brates— articulated to the thorax by

the "trochanter," "coxa" and "tro-
Fig. 140.— Maxilla and labmm of . „ _ • 4 , ,

Caloptenus. (After Packard), c, chantme, but the head-appendages

cardo ; s, stipes ; 1, lacinia ; g, iralea; , . , , rp,

p>, maxillary palp ;sm,submentum; are more Complicated. Ihey em-
rn, mentum ; pf, palpifer ; le and li, , ,, «,.« . ,

external and internal lobes ;PMa- brace the filiform antennae, the
biaipaip. strong cutting mandibles, the max-

illae and the labium, which is formed of a second pair of maxillae,
coalesced in the middle line (Fig. 140). Certain unpaired struc-

HIGH SCHOOL ZOOLOGY. 207

tures, like the labrum and metastoma of the crayfish, are repre-
sented here also, for above the mandibles there is an impaired
labrum articulated to the epicraniurn by an intermediate cly-
peus, and projecting into the mouth-cavity as the epipharynx,
while a hypopliarynx is found opposite in the floor of the
mouth ; both of these are covered with stiff hairs.

Although the abdomen has no obvious appendages yet the
blades of the ovipositor and the cerci (more conspicuous in the
cockroach) are, in reality, appendages of the eight, ninth, and
tenth segments ; traces of an eleventh segment are also present.

22. Of very different nature from the appendages, are the
wings : these are to be regarded as outgrowths from the notum
of the two hinder thoracic segments, which have become hinged
to the thorax, and penetrated by vascular and respiratory
organs. In this genus the anterior wings are less of use in
flight than the posterior, and serve partly as wing-covers (elytra).

23. In the locust, the nervous system is related to the seg-
mentation in a way somewhat similar to what we found in the
crayfish, but it is not so concentrated as in the spider. The
brain supplies the eyes, ocelli and antennae; the infraoesophageal
ganglion, the mouth-parts; the three thoracic segments have each
their own ganglion (the last of which supplies the ears) ; but
there are only five abdominal ganglia situated in the third,
fifth, seventh, eighth and ninth segments respectively (Fig.
141). The intestines have a special ganglion united with the
brain by a visceral nerve.

Little definite is known with regard to the senses of the locust ;
the antennae and palps of the jaws have undoubtedly a tactile
function, but it is likely that some parts of them may be employed
to detect odours and tastes as well. The compound eyes have
a similar structure to those of the crayfish, but there are in
addition three ocelli (comparable to a single ommatidium of a
compound eye), one of which is situated between the bases of
the antennae, the other two, higher up on the front of the head.

208

HIGH SCHOOL ZOOLOGY.

Locusts are capable of producing sounds by rubbing the hind
legs against the wing-covers, and they have also organs fitted
for perceiving sounds. These are situated on the first abdominal
segment, and consist of a vesicular
auditory sac, suspended on a stretch-
ed tympanic membrane.

24. Fig. 141 indicates the chief
parts of the intestinal system. The
oesophagus, on ascending from the
mouth-cavity (into which salivary
glands open), dilates into a crop, the
lining of which is furnished with
hairs regularly arranged. Al the
junction of the crop with the stomach
are several cceca, which serve to in-
crease the intestinal surface, while at
the junction of the stomach with the
intestine proper, the Malphigian or
urinary tubes are situated. The
heart is an elongated vessel occupy-
ing the first seven abdominal seg-
ments, and the respiratory organs
are a complicated system of air- tubes,
opening by ten pairs of apertures
(stigmata or spiracles) to the outside.
Two of these are thoracic, being situ-
ated in front of and behind the meso-
thorax, while the other eight are on
the anterior eight abdominal seg-
ments. The spiracles communicate
directly with two longitudinal lateral
air-tubes ; these give off the smaller
tracheae to the tissues, but the spir

HIGH SCHOOL ZOOLOGY. 200

acles are also very directly related to a series of large air-sacs,
which buoy up the locusts in their flight.

25. There is a conspicuous difference between the end of the
abdomen in male and female specimens \ in the latter (Fig. 141)?
the ovipositor serves to drill the holes in the ground in which the
eggs are laid, surrounded by a stiff secretion furnished by special
glands. Oviposition occurs in the fall, and development begins
at once, but is checked by winter, so that the young larvae only
escape from the eggs in the spring. Apart from the circum-
stance that they are destitute of wings, they resemble the parent
in form ; the complete resemblance is attained during a series
of moults, after each of which the body becomes larger and the
rudimentary wings more evident. No complete resting-stage
occurs such as the "chrysalis" of the butterfly, but the insect is
said to be in the " pupa" stage, before the last moult, which con-
verts it into the adult (imago) stage : the locust and its allies
are consequently said to develop without metamorphosis.

26. According to a recent computation, the number of species
of living animals described, amounts to some 272,000 ; of these,
200,000 belong to the class of the Insecta, and are consequently
constructed upon substantially the same plan as the locust
described above. Although only some 6,000 of these occur in
Canada, yet there is such a wealth of form, and such differences
of habit within the limits of this single class, that it will be
impossible to do more here than indicate the chief modifications
of the insect type, which characterize the various orders.

Most of these are more specialised than the type described,
so it may be as well to glance in the first place at the more
primitive forms. Such, like the cockroaches (Blattidce), and
earwigs (Forficulidce), are to be found within the order
(Orthoptera) and sub-order to which Caloptenus belongs. The
order receives its name from the position which the wings
assume in rest in the family (Acrydidce), in which it is

210

HIGH SCHOOL ZOOLOGY.

placed, and to which the carnivorous locusts and crickets are
nearly allied ; but the wings may be entirely absent, as in the
singular walking-stick insects (Diapheromerafemorata), or only
partly developed, as in some of the cockroaches and earwigs.

The family Phasmidm contains some of the most striking cases of
protective resemblance to the environment, for the members may
resemble dried twigs, or even leaves of the trees on which they live, as
in the case of the East Indian winged Phyllium,

27. From the earwigs we are led to a group of insects char-
acterized by the entire absence of wings, and the presence of
caudal appendages, equivalent to the cerci of the locust and
cockroach, and to the forceps of the earwigs. These are the
spring-tails (Thysanura), inconspicuous on account of their size
(Fig. 142), but interesting to the zoologist as the most lowly
organized insects, some of them (Fig. 143) even having rudi-
mentary legs on the abdomen, and thus resembling certain
Myriapods (Fig. 144).

14.2.— Podura.

Fig. 143— Cam-
podea.

Fig. 144— Scolo*
pendrella.

28. The characters of this class, the Myriapoda, may be
therefore briefly examined before proceeding to the higher In-
secta. It is a small group of less than a thousand species, in
which the numerous segments of the body may each bear one
or two pairs of appendages, but are never grouped, as they are

HIGH SCHOOL ZOOLOGY. 211

in the Insecta, into thorax and abdomen. There are no wings,
and the maxillae may only be present in one pair. Most of the
Myriapods fall into two orders, the Chilopoda and Chilognatha,
the former including carnivorous forms (Centipedes, Fig. 145),
the latter, forms which live in decaying vege-
table material (Millipedes and galleyworms).
The parts of the mouth are adapted to their
habits, for in the Chilopoda the first pair of legs
end in powerful claws perforated by the duct
of a poison-gland, and are turned forwards to
supplement the three pairs of jaws. In the
Chilognatha, on the other hand, there is only
one pair of maxillae below the mandibles, and
they are united to form a labium. The two
Fig. 145.-Scutigera. gr0Ups further differ in that the Centipedes
have only one pair of legs to each segment, the Millipedes two j
and that, while the Centipedes resemble the insects in the
position of the opening of the oviduct, this is near the head in
the Millipedes. It will be apparent from what follows that
these are much more important structural peculiarities than we
find separating the orders of Insecta from each other.

Certain tropical worm-like forms (Peripatus) which have the habits of
Millipedes, but whose segments bear unjointed appendages terminating
in hooks, are of interest as being intermediate between the Vermes and
the lower Arthropoda. A separate class (Protracheata) has been formed
for their reception.

29. Returning to the locust and its allies, which are described
vas the Orthoptera proper (0. genuina), we must now proceed
toward the higher orders of insects, glancing, in the first place,
at certain forms associated by naturalists with the Orthoptera,
on account of the structure of the mouth-parts and the absence
of a metamorphosis, but differing from them in that both pairs
of wings are alike. The wings resemble those of the nerve-

HIGH SCHOOL ZOOLOGY.

winged insects (Neuroptera), and, to distinguish them from
these, the forms referred to are called Pseud o-neuroptera.
Belonging here are the dragon-flies (Libellulidce), May-flies
(Ephemeridce), stone-flies (Perlidce), all of which have aquatic
larvss (into the tracheae of which air is absorbed through
peculiar expansions of the body-wall known as tracheal gills),
but there are also forms with terrestrial larvae, such as the
Psocidce (very small insects which live like plant-lice chiefly on
hardwood trees, and often attract attention by the woolly -looking
masses which they form).

Allied to these are the tropical Termites, often called "white ants, "
because they live a social life in colonies and build nests. An African
species — Termes bellicosus — builds towers 12 or 15 feet high ; in addition
to the males and females, the inhabitants are partly wingless neuters,
most of which undertake the work, but some the defence of the colony,
and are therefore called workers and soldiers.

Occupying an intermediate place between the Orthoptera and the next
order, is the family Tlirypsidce, including minute insects which have the
parts of the mouth adapted for sucking vegetable juices. They often
attack cultivated plants in great numbers, causing destruction, e.g., of
the hay and onion crops. The wings of the adults are margined by long
delicate hairs.

30. Like the Orthoptera, the Hemiptera are insects with an in-
complete metamorphosis, but the parts of the mouth are gener-
ally modified for sucking, the labium being converted into a
grooved and jointed proboscis (generally folded back underneath
the thorax), in which the mandibles and the maxillae lie in the
form of slender stylets (Fig. 146, 2).
h

Fig. 146, 1, 2, S — Diagram of transections of the proboscis of dipterous, hemip-
terous, and lepidopterous insects. (After Dimmock, Graber, and Muhr, respectivelyX

le, labrum and epipharynx ; lb, labrum, la, labium , (between the two are the
mandibles and maxillae, and in 1, the hypopharynx); mxt maxillae.

HIGH SCHOOL ZOOLOGY. 213

Palps are absent, except in some low wingless forms — the
Mallophaga — which live on the young hairs and downs of
mammals and birds, and have, consequently, biting mouth parts.
They, with the Pediculidce, which live by sucking the blood of
animals, form the sub-order Aptera. But the absence of wings
is not confined to this sub-order, some of the plant-parasites
(sub-order Phytophthires) being also wingless. This sub-order
includes the plant-lice, Aphidce, and the scale-insects, which are
so harmful to plants (especially those cultivated in the house)?
the juice of which they suck by means of the proboscis.

Among the better known forms of these parasites are the Phylloxera
vastatrix, which was carried from this continent to Europe, and has
there done enormous damage to the vineyards, chiefly by forming galls
on the rootlets of the vines, and the cochineal insect (Coccus cacti), a
scale-insect which lives on the prickly-pear cactus in Mexico, and
which is the source of carmine, one of the most valuable dyes of
commerce.

The bulk of the Hemiptera belong to the two remaining sub-
orders, the Homoptera, in which the wings are alike, and the
Heteroptera, in which the anterior are partly converted into
elytra. To the former belong the musical Cicadidce, the males
of which have a vocal apparatus on the under surface of the ab-
domen, and the Cicadellidce, which are much smaller forms but
include many more species. To the latter, belong the water- and
land-bugs, Hydrocores and Geocores. In accordance with their
aquatic life, the Hydrocores have one or more pairs of legs
modified for swimming, their habitual mode of locomotion
during the day, but their hind wings enable them to fly, which
they do chiefly at night. All of them are predaceous forms,
sucking the blood of fishes, Ephemerid larvae, etc. ; they are
capable of inflicting a sting by means of their proboscis. The
body may be elongated (Ranatra), or flattened (Belostoma), or
keeled for swimming on the back (Notonecta). The Geocores,
however, include many more species, partly living on animal,
partly on vegetable juices. Some have extremely long legs, by

214 High school zoology.

means of which they run over the surface of water (Gerris) ;
others have a flat, depressed body, with short legs, like the
bed-bug (Acanthia lectularia), while among the phytophagous
forms, to which some destructive species like the chinch-bug
(Rhyparochromus leucopterus), and the squash-bug (Coreus
tristis) belong, a great variety of form exists.

31. All the Insecta mentioned above are spoken of as ame-
tabolic forms (A?netabola), on account of the fact that they do
not undergo a metamorphosis. Those on the other hand now
to be dealt with are metabolic (Metabola).

At first sight the Neuroptera, on account of the wings, seem
to be closely allied to the May-flies referred to above, but their
larvae pass through a resting (pupa) stage, during which they
attain their aduit form. The terrestrial larvae of Myrmeleon
are called ant-lions, as they feed on ants, which they catch by
preparing sand-pits for them to roll into. They spin a cocoon,
in which they pass their pupa-stage. The aquatic larvae of the
caddis-flies (Phryganea) live in cases, formed of sand or bits of
twigs, in which they afterwards pass the pupa-stage. This
group (Trichoptera) is an interesting one, because it leads to
the Diptera and Lepidoptera, both on account of the fact that
the anterior wings are hairy, and because the mouth-parts ap-
proach the structure met with in these orders. The latter is
true also of the genus Panorpa, which is further remarkable for
having caterpillar-like larvae.

32. From the carnivorous terrestrial larvae of the Neuroptera
we pass naturally to the carnivorous forms of beetles — Coelop-
tera, — which are marked by a more complete conversion of the
anterior wings into elytra than we have yet met with, and by
a greater resemblance of the mouth-parts to those of the Orthop-
tera, than exists in other insects. More than a third of the known
species of insects belong to this order ; it may be gathered, there-
fore, that within comparatively narrow limits of structural
modification there is a surprising wealth of form, associated

SIGH SCHOOL ZOOLOGY. 215

with adaptation to habits of life characteristic for each species.
Thus we have the carnivorous Carabidce, running forms often
destitute of the hind wings, the allied aquatic water-beetles,
Dytiscidce, and scavenger forms like the Sylphidce and Staphy-
linidce, several of the latter being always found in ants' nests,
and presenting curious instances of dependence upon their hosts.
Destructive household-pests like the Dermestidce (which attack
furniture, carpets, museum specimens, etc.), are amongst the
smallest of the order, while the Scarahoddaz, along with a number
of familiar phytophagous forms like the May-beetle (Lachno-
sterna), include some tropical giants — Dynastes — which may
attain a length of 5 or 6 inches. The fire-flies (Lampyridce) are
sufficiently marked by the luminous organs on the abdomen,
the weevils (Curculionidce) by the prolongation of the head into a
sort of proboscis, the bark-beetles (Bostrychidce)by the character-
istic channels which they hollow out in trees. Several of the
leaf-eating forms (Chrysomelidce), like the potato-beetle (Dory-
phora decemlineata), are familiar, and the lady-birds (Coccinel-
lidce), which feed on plant-lice, attract attention as well by their
form as by their colouration.

33. In the two next orders of insects, Diptera and Lepido-
ptera, the mouth-parts are formed for sucking, but this conver-
sion is carried out in different ways in the two groups. In the
former the labrum and the labium form an unjoin ted double
tube, in which stylets formed of the mandibles, maxillae, and
hypopharynx are contained (Fig. 146, i). In the Lepidoptera on
the other hand, it is the maxillae which by their apposition
form the sucking proboscis (Fig. 146, 3) ; the maxillary palps
are rarely well developed, while the labial palps are. The
Diptera receive their name on account of the apparent absence
of the posterior wings, which are converted into balancers —
halteres ; the Lepidoptera, theirs, from the presence of scales
(which are generally coloured) on the wings.

216 High school zoology.

To the Diptera belong the mosquitos (Culicidce), black-flies
(Simulidce), and horse-flies (Tabanidce), the females of which
suck blood through wounds made by their piercing stylets.
The larvae are aquatic, or, as in the case of the horse-flies, they
live in the earth. There are also forms like the Hessian-fly
{Cecidomyia destructor), which are injurious to cultivated
plants, eggs being deposited within the cellular tissue, and thus
forming galls, in which the larvae are developed. Again, there
are the domestic flies (Muscidce), in which the ends of the
labium — (labellce) — are converted into a rasping proboscis, which
enables them to dispense with their piercing stylets. The
larvae (maggots) lead a parasitic or saprophytic life. Finally, the
fleas (Pulicidce) are distinguished by the absence of wings and
by the serration of their mandibles, which adapts them better
for their life of semi-parasitism.

Many differences of habit are likewise met with among the
Lepidoptera. Small forms like the clothes-moths (Tinea) belong
to the Microlepidoptera, which also include a hcst of forms de-
structive to vegetation, in one way or another, like the coddling-
moth (C arpocapsa). Such is also the case among the larger
forms, Macrolepidoptera, which include the butterflies (Papil-
ionidce), hawk-moths (Sphingidce), silk-worm moths (Bomby~
cidce), and other families.

It is in this order that remarkable instances of protective resemblance
to other animals (so-called mimicry) was first observed. The bee-moths
(e. g., Sesia thysbe and others) receive their names from (and owe their
freedom from attack to) their resemblance to various stinging wasps.

34. The most highly developed of all insects are undoubtedly
the Hymenoptera. They exhibit this in the reduction of the num-
ber of the abdominal segments and in the concentration of the
nervous system, as well as in the social life which characterizes
the higher genera It is possible to recognize in the parts of
the mouth, all of those met with in the locust, but the charac-
teristic " tongue" of the bee is formed by the fusion and prolong-

HIGH SCHOOL ZOOLOGY.

217

ation of the inner lobes of the labium, while the external lobes
so marked in the locust here only form the paraglossse (Fig. 147).

Fig. 147.— Part of the Head with the Mouth-parts of the Honey Bee.
01, labrum ; k1, mandible; k2, maxillae ; taz, maxillary palps ; uk, submentum ;
fc. mentum; g, palpifer ; al'!, external lobe of the labium (paraglossaY) ; il, internal
lobe, (tongue) ; ta;i, labial palps.

Both pairs of wings are transparent, the anterior larger than
the posterior, and united with them in flight. The lowest
group, the saw-flies (Tenthredinidce), have caterpillar-like larvae
which live on leaves, but are distinguishable from caterpillars
by the greater number of abdominal feet. Most of the families,
however, either provide for the larvae, cells of wax, or of paper,
or in the soil, and stock these with suitable food, which may
consist of honey, or pollen and honey, or of paralyzed insects
(Sphegidce), or else they deposit their eggs in the bodies of other
insects, or in plants, in such a way that the larvae on hatching
are surrounded with suitable food. In either case the larvae
are footless, and have rudimentary mouth-parts. The first con-
dition is met with in bees (Apidce), wasps (Vespidce), and ants
(Formicidce), the females of which are furnished with a sting
or modified ovipositor connecting with a poison-gland, the
second in the Ichneumonidce, which possess long ovipositors by
which they deposit their eggs in other insects, and in the
Cynipidce (the gall flies), where the laying of the eggs by the
short ovipositors, in the cellular tissue of plants, gives rise to
characteristic diseased outgrowths — galls — , in the interior of

which the insects live till they reach the adult condition.
15

2l8 HIGH SCHOOL ZOOLOGY.

CHAPTER VIII.
The Vermes and Mollusca.

1. In last chapter, reference was made to the prevailing heter-
onomy of segmentation of the Arthropods, but the class of the
Myriapods, and especially the genus Peripatus, were described
as possessing a more worm-like form and homonomous segment-
ation. The latter genus, indeed, is destitute of the jointed
appendages almost universal in the Arthropods, and its locomo-
tive organs rather suggest the unjointed stumps of the highest
worms. These belong to the class Annelida (of the sub-kingdom
Vermes), a class which is chiefly represented by marine forms,
but of which the earthworm and leech may be selected as more
accessible types.

2. The Vermes admit of no such sharp definition as do the
Arthropods, for although bilateral symmetry is present in all,
yet some forms are segmented, others unsegmented, and thus,
the structure of the body may be extremely different in the
various classes. The highest class, the Annelida, includes all
the segmented forms, and those, consequently, nearest the
Arthropods : a comparison, however, of an earthworm and a
leech, on the one hand, with a crayfish on the other, will disclose
the essential differences which exist between them.

3. One of the most notable of these is the absence of any
exoskeleton such as that of the Arthropods; a thin cuticle
containing chitin represents it, and is formed by underlying
epidermal (so-called hypodermal) cells, but many of these ar^

HIGH SCHOOL ZOOLOGY.

219

glandular in their character, and thus the skin is softer than in
the Arthropods. The external segmentation does not always
correspond to the internal ; in the earthworm it does, partitions
or septa being attached opposite the external furrows, which
tend to divide off the ccelom into so many chambers as there are
segments. In the leech, however, there are several furrows,
which are merely skin deep, to each true segment marked off
by the septa. The completeness of the internal segmentation,
brought about by these septa, necessarily affects the various
organs contained in the ccelom, thus the intestine, the blood-
vessels and. the nerve- cord all partake in it. It is not often
that we observe any reduction in the number of repeated parts,
(each segment, for example, having its own nerve-ganglion), and
this is especially true of the excretory system, each segment
having a pair of coiled tubes, segmental organs or nephridia,
which open outwardly and also into the ccelom (Fig. 1 48). Ho-

Fig. 148.— Diagram of transection of earthworm.

JJ, the hypodermis ; c, the circular, I, the longitudinal muscular layers ; Sl /52,
the upper and lower pairs of bristles; a, external, a1, coelomic aperture of the
nephridium(the external aperture is not exactly in the same plane as the setae, nor is
the internal aperture in the san.e plane as the external) ; i, the intestine with its roof
infolded (typhlosole) : it is coated with glandular epithelial cells; blood-vessels are
represented in black, above and below the intestine, and around the nerve-cord — n.

220 HIGH SCHOOL ZOOLOGY.

mologues of these are to be recognized in the green gland of the
crayfish, and the coxal glands of various other primitive Arthro-
pods, such as the scorpions and mites, which have a similar
position, but are not repeated in every segment as in the
Annelids.

The excretory organs of Annelids find a closer parallel in the kidneys
of the more primitive Vertebrates, which are also disposed segmentally ;
the internal apertures may be retained, but the separate external aper-
tures are replaced by a single collecting duct leading to the outside.

4. Instead of the elaborate muscles which are present in the
highest Arthropods, we find that the muscles and the skin
are closely united into a tube surrounding the coelom. Im-
mediately underneath the skin is a layer of circular fibres,
within that, one of longitudinal fibres, and both are penetrated
by radial fibres which extend from the skin inwards. Although
locomotion is always effected by the alternate contractions
and relaxations of this cutaneo-muscular tube, yet the precise
way in which it is carried out differs in the two subclasses of
Annelids — the Chsetopoda and Discophora — to which the earth-
worm and the leech respectively belong. In the former, loco-
motion is assisted by bunches of strong bristles (setse) attached
to the sides of the segments, and worked by Special muscular
slips, while in the latter, one or more regions of the tube are
modified into suckers, which fix the body, while the muscu-
lar tube alternately contracts and elongates.

5. To the Chsetopods belong the bulk of the Class, marine
forms with numerous bristles (Order Polychaeta) fixed on short
projecting stumps (parapodia), which may also carry feelers,
gills, or protecting scales. The marine Annelids are either car-
nivorous in their habits, living a free life, and swimming or
creeping about the seashore, or sedentary forms, which burrow
in the sand (Fig. 149), or live in tubes of chitin or sand or lime,
which are constructed with the aid of secretions from the skin.

HIGH SCHOOL ZOOLOGY. 221

The order to which the earthworm belongs, however,
(Oligochseta) chiefly includes fresh-water (limicolous) or teres-
trial (terricolous) worms, where the bristles are few in number,
and lodged in setigerous follicles, there being no parapodia, nor
appendages of the nature of feelers or gills. The Limicolse are
small forms living for the mosb part in the mud at the bottom
of ponds or streams. Some of them, the Naididce, are parti-
cularly remarkable on account of their reproducing themselves
by budding, so that they are often found in chains, still
attached to each other. They live chiefly on decaying vegetable

Fig. 149. —Marine lob-worm. (Arenicola piseatorum).
The bunches of setaB are more apparent in front of the gills than behind.

matter, but one species of Chcetogaster lives a parasitic life in
the lungs of various pond-snails. The earthworm (Lumbricus
terrestris) is the most familiar of the Terricolse ; its setae are not
conspicuous, but each segment carries eight, disposed in four
groups. One region of the body is often swollen and noticeable,
bearing the clitellum ; it furnishes a cocoon in which the eggs
are developed. The researches of Darwin proved the earth-
worm to be of the first importance in the loosening of the soil
and the formation of mould. This is effected in the course of
its burrowing, which it does partly by separating the particles
of earth, partly by swallowing them. Although no special respir-
atory organs are present, yet the skin is traversed throughout
by capillary vessels, which bring the blood close to the surface.
The fluid portion of the blood (not the corpuscles, I, 60) con-
tains haemoglobin j and its circulation through the skin, as well

222 HIGH SCHOOL ZOOLOGY.

as through the rest of the body, is assured by heart-like loops
which connect the principal longitudinal vessels. These are
situated above and below the tubular intestine, and above and
below and on each side of the nerve-cord.

6. The Discophora differ from the other Annelids in the entire
absence of bristles, and in the presence of a sucker immediately
below the posterior aperture of the intestine. Most forms also
have the segment in front of the mouth (prestomium) converted
into a sucker. In accordance with their habits of life, we find
conspicuous structural differences in the Leeches, as compared
with the other Annelids. They are sometimes temporary para-
sites, like the medicinal leech in Europe (Hirwdo) or its Ameri-
can representative Macrobdella, living upon the juices of other
animals, which they suck and store up in a sacculated intess
tine, or carnivorous forms with a simpler intestine preying on
the smaller Invertebrates (Nephelis). Both of these groups
have jaws, which are used either for inflicting a wound be-
fore sucking, or for comminuting their food. Other para
sitic forms are destitute of jaws, but have instead a protractile
proboscis. Common examples are the fish-leech (Piscicola or
Ichthyobdella), and the various species of Clepsine, large form-
of which attack the pond-turtles, while smaller species prey on
the pond-snails. Another interesting form, destitute of the
anterior sucker, is the curious little BranchiobdeUa, several
species of which are to be found on the gills, and on the head-
parts, of the various species of crayfishes.

7. In contrast to the Annelids, the lower Classes of Vermes do
not possess metameric segmentation. Certain marine forms —
Gephyrea — have segmental organs, but the ccelom is undivided
and the nerve-cord alike throughout. In the other Classes
(Rotifera, Nematelminthes, and Plathelminthes), to which, for
the most part, unfamiliar and inconspicuous forms belong, a

HIGH SCHOOL ZOOLOGY.

223

so-called water-vascular system — to be presently described —
replaces the segmental organs.

8. TheRotifera or Wheel-Animalcules are microscopic aquatic creatures,
round the mouth of which are disposed lobes bearing cilia, which, when
ill motion give the appearance of rotating wheels (Fig. 150). They serve
to bring food to the mouth, and also for
swimming. A longer or shorter tail, which
is sometimes telescopic, assists in locomo-
tion, and serves also, as it terminates in a
pair of forceps, for temporary fixation. Some
of the species are sedentary, living in tubes,
either singly or in colonies. The intestine is
absent in the males (which are not only more
minute than the females, but also much fewer
in number, and shorter-lived), but it is com-
plete in the females, having near the mouth
an expanded part containing a chitinous mas-
ticating apparatus, and, behind that, two
lateral cceca. The water-vascular system
consists of two convoluted tubes opening
anteriorly into the coelom and posteriorly
into a contractile bladder, which communi-
cates with the rectum. Instead of the elong-
ated nerve-cord of the higher Annelids, there
is here only a single ganglion situated above
the oesophagus, whence are distributed nerve-
fibres to the various parts, including the eyes
and tactile organs. There are no blood-
vessels, and no respiratory organs. The Rotifers like the Tardigrades
have considerable power of resisting death by desiccation.

Fig. 150
fer.

Female of Roti-
(Hydatina senta).

9. The names of the remaining Classes, which include for the
most part parasitic worms, are taken from the form of the body,
which is cylindrical in the Nematelminthes but flattened in the
Plathelminthes. According to the grade of parasitism, the in-
testinal system is more or less reduced, being absent in those
most completely adapted for a parasitic mode of life. Organs of
fixation suited to the nature and degree of the parasitism, are

224

HIGH SCHOOL ZOOLOGY.

also to be recognised. The development is often complicated
by a metamorphosis, and the creatures often pass through dif-
ferent stages of their parasitic life in different hosts, a phenom-
enon known as heteroecism.

Fig. 15L— Trichina spiralis*

A, female; B, male; C, junction of oesophagus and intestine; D, encysted

Trichina-larva between the fibres of muscular tissue.

10. Two orders of Nematelminth.es are recognised, the Nematodes,
which have generally a complete intestine, and the Acanthocephali, which
have none. To the former order there belong some free microscopic forms,
which live in decaying matter in water, also some vegetable para-
sites, like the wheat- worm ( Tylenchus) and the beet- worm (HeteroderaJ,
but the bulk of the order are parasites, either during a part of their
life (like the insect parasites Oordlus and Mermis), or during the whole of
it. All groups of Vertebrates have special Nematode parasites, which live
in the skin, or the eyes (FilariaJ, or in the intestine (Ascaris), or the

HIGH SCHOOL ZOOLOGY.

225

muscles ( Trichina), or the respiratory organs (Syngamus, Strongylus),
or blood-vascular system (Sclerostomum), and cause many serious
diseases. One of the most dangerous of these to which man is liable,
is Trichiniasis, caused by eating insufficiently-cooked pork, in the
flesh of which the minute encapsuled Trichinae are living (Fig. 151).
The Acanthocephali are so-named, from a proboscis covered with hooks,
by which they fix themselves in the intestines of their hosts — for the
most part, lower Vertebrates.

11. The Plathelminthes also include some free forms, such as the marine
Nemertini, unsegmented worms, which sometimes attain alength of thirty
or forty feet (Linens), and also the Turbellaria, for the most part very
small creatures living in water or damp places. In both, the skin is covered
with ciliated cells, which are absent in the other (parasitic) orders.
The intestine is tubular and complete in the Nemerteans, but in the
Turbellarians it is sometimes much branched, and always opens to the
outside only by the mouth. The commonest forms are species of Plan-
aria (Fig. 152 b) little flat, leech-like forms,
which are to be found clinging to stones or
creeping about in fresh-water ponds or
streams. They are rartly longer than half
an inch, but some marine forms attain a
much larger size. On the other hand, there
are fresh-water Turbellaria with a simple
rod-like intestine (Fig. 152 a), which rarely
exceed a line in length, and others, with
no intestine at all, in which the food-parti-
cles are simply admitted by the mouth into
the interior of the body, which is composed
of soft cells.

Fig. 15a— Turbellaria.
p a, Mesostonium, with rod-
like ; b, Planar la, with branch-
ed intestine ; m, the mouth ; n,
nerve-ganglia with eye-spots.

12. The remaining orders of the Flat-worms
are the Trematodes, and Cestodes. In the
former, the intestine is a forked tube open-
ing only by the mouth ; in the latter, it is entirely absent, and
there is no ccelom in either. Organs of fixation in the form of
suckers or hooks are always present. The Trematodes live either
as ectoparasites on various animals, such as fishes and molluscs, —
in which case they are well provided with hooks and suckers, and
form only a few eggs, which they fix directly to their hosts, —
or as entoparasites within various Vertebrates, — in which case they

226

HIGH SCHOOL ZOOLOGY.

generally have two suckers (genus Distomum J, one round the mouth,
the other on the ventral surface. The eggs are very numerous,
for only a very small number of them can meet with the com-
plicated conditions favourable to their complete life. They do not give
rise at once to the Distome form, but, by internal budding, to inter-
mediate broods, which differ from the adult in form, and are found in
some different animal (Fig. 153),

Fig. 153.— Developmental cycle of Distomum hepaticum.— The liver-fluke of sheep.
(After Leuckart).

a, the adult showing the position of the suckers, and the hranched intestine ; b,
an egg with opercillum, and contained ciliated embryo, with some unconsumed food-
yolk.— This embryo gives rise to. a "sporocysfin which " rediae," like c, are formed
by internal budding. The redia gives rise, also by internal budding, to larval distomes —
" cercaria) " d, —which loose the tail and after encystment attain the adult form, a.

13. Apart from the absence of the intestine, the Cestodes differ from the
Trematodes in the formation of chains by budding, each segment in the
chain or proglottis, resembling its neighbour, but differing from the
original or head-segment, by the absence of organs of fixation. The seg-
ments have sometimes more, sometimes less capacity for independent
life. The eggs formed within them do not at once develop into original
head-segments, but into larval bladder-like forms (Cysticerci) — which are
found in some different animal from the host of the adult — and these
may, by budding, give rise to more than one head-segment. The adult
chains are found in the intestines of all the classes of Vertebrates ; the
cystic stages in the flesh, liver or brain of some animal, which serves as
food for the host of the adult chains (Fig. 154). Thus the tape- worms of
the carnivorous sharks pass through their cystic stages in the Teleosts,

HIGH SCHOOL ZOOLOGY.

on whichthey feed. Through eating insufficiently-cooked beef,
fish, man is liable to several forms of these parasites.

pork or

Fig. 154.— Developmental cycle of Taenia serrata. (A species of tape-worm
which occurs in the dog). (After Leuckart).

1, A young tape-worm composed of the head, with hooks (a, b), and suckers, and
a chain of immature segments ; 2, a mature segment, the branched uterus of which is
full of G-hooked shelled embryos, 3 ; these gain access to the liver of the rabbit, loose
their hooks, become encysted, 4, and invaginated at one end which gives rise to the head
of the future tape-worm, 5 ; 6, a fully formed bladder-worm (Cysticercus pisiformix) ;
7, section of the head before its eversion ; r, the rcstellum which carries the hooks ; s,
two of the suckers.

MOLLUSCA.

14. From the lowly- organised unsegmented worms, which we
have been considering, to a sub-kingdom like the Mollusca, which
contains some of the largest and most highly-organised of the
Invertebrates, seems a very long step, and yet it is to the Vermes,
and not to any of the other sub-kingdoms, that we must look
for any resemblance to the Molluscan structure,

228 HIGH SCHOOL ZOOLOGY.

The sub- kingdom derives its name from the softness of the
tissues of the body, a peculiarity dependent on the fact that it
is generally protected by a one or two-valved shell. Locomo-
tion is effected by the specialised musculature of the ventral
surface of the body — the so-called foot— winch recalls, in many
cases, the creeping surfaces of the Planarians, but is often
curiously modified for other methods of locomotion. . The re-
spiratory organs are generally gills, situated on one or both sides
of the body and protected by a fold of the skin called the
pallium or mantle ; it is this portion of the skin which has the
function of secreting the shell. One pair of excretory organs,
similar in structure to the nephridia of the segmented worms,
are present, but the nervous system is arranged on a plan
entirely different from that of any of the Yermes studied.

15. Two subdivisions of Molluscs are recognized, which differ
according to the amount of specialisation of the cephalic end of
the body. The bivalve shell-fish, from the peculiar manner in
which their food is secured and their almost sedentary habits,
have none of that concentration of the sense-organs and of the
nerve-centres into the "head," which we find in the other
Molluscs. They are thus frequently called the Acephala, in con-
trast to the Cephalophora.

16. The Acephala form a single class — Lamellibranchiata,
called so on account of the plate-like gills, which are present in
all. It is chiefly a marine group, but representatives of both of the
orders into which it is subdivided occur in fresh water, the most
conspicuous being the fresh-water Mussels (Unionidcu), any
one of which will serve as a type for the study of the class.

The shell, like the body, is symmetrical, the right and left
valves being similar ; it is only in attached forms of Lamelli-
branchs like the oyster, in which any great degree of asymmetry
is to be observed. At the dorsal surface is to be noted the
hinge, formed by an an uncalcified part of the shell, the ligament,

HIGH SCHOOL ZOOLOGY.

and often by teeth on the valves. In front of the hinge are
the umbones, the first-formed parts of the valves ; they gener-
ally incline forwards. Three layers may be seen in the shell,
the outer brown periostracum, the thick prismatic layer formed

by the activity of the thickened
border of the mantle (Fig. 155), and
the nacreous or pearly layer, se-
creted by the whole mantle surface.
Pearls are the result of repeated
layers of this substance being form-
ed round foreign particles, which
have got between the mantle and
the shell. The mantle corresponds
in form to the shell, hanging down
right and left of the body : in many
Lamellibranchs, the margins of its
two lobes tend to unite, except in

mm 4» •»■ *. *_ _*• front, to allow egress to the foot,

Fig. 155.— Diagrammatic transection ' ° '

^Anodon. (After Ludwig). and behind at two points, the

1, ligament; sh, shell; m, mantle ; . _ ,, , . ,

w', its thickened margin; g\ g2, SipAOIlS, to allOW Water to get into
outer and inner gill-plates;/, in the , . j* ±\. n -i. r .

mantle-cavity points to the foot, which and out ot the mantle cavity, but

contains portions of the intestine (i) ., . • i „ , „ _ • ji „

and reproductive organs ; n, is in _ the thlS Union does not OCClir in the

*o^n!n^ot?s^onf^diSM^Tnto TTnios, and the siphons (Fig. 156),

the mantle-cavity. ^ merQ gpecialised parts Gf the

mantle-margin, which can be fitted together.

Locomotion is effected by the ploughshare-shaped foot ; mus-
cular fibres are hardly developed elsewhere in the body-wall
except along the border of the mantle, and especially at its
anterior and posterior ends, where the adductor muscles which
close the shell are situated.

Related to these muscular masses are the three pairs of nerve-
ganglia — cerebral, pedal and parieto-splanchnic — with connect-
ing nerve-cords. A pair of flat, triangular, tactile tentacles on

230

HIGH SCHOOL ZOOLOGY.

each side of the mouth, a pair of otocysts in the foot, sup-
plied by the cerebral ganglia, and a patch of olfactory neuro-
epithelium near the posterior adductor are the chief seats of
the special senses. In some forms, eyes are distributed along
the mantle-margin, but not in the Unios.

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The mouth lies under the anterior adductor and leads into
a stomach surrounded by a bulky liver, and possessing a ccecum
containing a " crystalline stylet" of unknown function. After
several turns within the foot, the intestine ascends, and in its
course to the upper surface of the posterior adductor, is enve!"

HIGH SCHOOL ZOOLOGY. 231

oped by the heart. This organ is " systemic," driving the blood,
which it has collected from the gills, forward and backward
throughout the body. The most spacious part of the ccelom is
the pericardium surrounding the heart ; it communicates with
the outside (the mantle-cavity) by means of a pair of nephridia
(the Organ of Bojanus), which open into the pericardium ante-
riorly, and then turn upon themselves in such a way, that the
distal non-glandular part of each tube lies above the proximal
glandular part, and opens in nearly the same plane as the peri-
cardial opening.

There are two gill-plates ; each is formed of a number of ver-
tical filaments attached to the side of the body-wall (as may be
seen to the right of * in Fig. 155) and curved upon themselves,
the inner series to the inside, the outer to the outside. The
plate results from the union of filaments to their neighbours
in front and behind ; it is double, owing to the recurving of
each filament, but the two layers are separated above, although
the space between them is partly obliterated by junctions be-
low.

Water is sucked through the inhalent or branchial siphon by
means of ciliated cells on the gill-plates ; the current sets through
the surface of the plates into the spaces between the two layers,
whence it is swept out through the exhalent or cloacal siphon,
carrying with it the excreta from the kidneys and intestine.
Solid particles contained in the water are swept forwards
towards the mouth, and guided into it by ciliated cells on the
tentacles.

The reproductive organs are situated in the foot, and the eggs
undergo the greater part of their development in the inter-
lamellar space of the outer gills, which are thus turned into
brood-pouches. The distribution of the larvae (Glochidia) is
provided for by their escaping thence and fastening themselves

HIGH SCHOOL ZOOLOGY.

in the skin of various small fish, where they undergo a resting
stage before they attain their adult form.

17. The Unionidse belong to an order Asphoniata distinguished by the
absence of tubular siphons ; the oyster {Ostrea) and scallop (Pecten) also
belong here, but they have only one (the posterior) adductor muscle," and
no foot. Intermediate between these types is the sea-mussel (Mytilus),
in which the anterior adductor and the foot are small. These forms are
attached, not by the shell, but by horny "byssus " threads secreted by
the foot.

18. A second order Siphoniata is formed for those in which the mantle
cavity is closed^ except for the tubular sphons behind, and an aperture
for the foot in front. Numerous minute fresh-water forms {Cyclas,
Pisidium) belong here, but the bulk of the forms are marine. When the
siphons are long, and can be retracted into the shell, there is a corres-
ponding mark within the shell (F g. 157), as in the Sea-clams (Mya and
Venus). Some of the forms burrow in sand, others in rocks (Pholas), or
timber (Teredo).

19. The higher division of the Mollusca (the Cephalophora)
presents a much greater range of form than do the Acephala;
four Classes are recognized, each of them
exhibiting important modifications of the
typical Molluscan structure. Most of the
species belong to one of these, the Gas-
Fig. 157. tropoda, called so on account of the de-
Tellina grcenlandiea. ,/».,/»,., ■ .•

velopment or the foot into a locomotive

organ, generally a flat creeping surface, occupying the ventral
aspect of the body.

Yery few Gastropods retain the bilateral symmetry which we
see in the Acephala ; the most primitive forms — the Chitons —
do, (a group, which of all the Mollusca, comes nearest to the
Yermes), but in most a distinct asymmetry is present. This
depends upon a separation of the vegetative from the animal
organs, and the grouping of the former into a visceral mass or
hump, above the head and foot, which are closely united (Fig. 1 58).
The visceral mass is protected by a shell (similar in structure

HIGH SCHOOL ZOOLOGY. 233

fco that of the Lamellibranchs), which, in the simplest cases, is
formed of a single conical piece ; in most Gastropods, however,
the shell is spiral, and the visceral mass has, in the course of
development, become twisted in the same direction, so as to cause
the intestine e. g, to open anteriorly. This twist results in the
suppression of the gill and nephridium of one side, and also in

x'

Fig. 158.— Diagram of Limnaea, to show the course of the intestine and the
arrangement of the nerve-ganglia in the head.

r, floor of the mouth occupied by the radula ; r1, a row of lingual teeth ; g, posi-
tion of apertures of reproductive organs ; m, the free mantle margin ; ml the line of
fusion of the mantle with the body-wall bounding the lung in front ; I, the aperture of
the lung ; a, the anus ; S, the stomach, receiving tne tubes of the liver which occupies
the apex of the shall : C, the cerebral, pi, the pleural, v, the visceral ganglion ; be
tween the two pleural are the two pedal, and between the visceral, the single abdom-
inal ganglion.

the asymmetrical situation of the heart. The direction of the
twist determines which side of the body shall be affected ; it is
sometimes towards the right (dexiotropous), but generally
towards the left (leiotropous), in which case the organs of the
right side are retained at the expense of those of the left.

The mantle-cavity, which is so roomy in the Acephala, is
much restricted in the Gastropods, and is confined to the sides
of the visceral mass. The mantle-margin is rarely free, but
generally forms an enclosed space opening externally by an
aperture or tube, which lies on the right side in left-twisted
(leiotropous) forms.

Apart from the asymmetry referred to, the most striking dif-
16

234

HIGH SCHOOL ZOOLOGY.

ference is in the organization of the head. Not only are the ehie£
nerve-centres and the sense-organs aggregated here, but there is
developed a complicated mechanism in connection with the
mouth, consisting of horny jaws and a lingual ribbon or radula,
the surface of which is beset with teeth like a rasp or file, and
which can be ever! ed by special muscles.

20. Three-fifths of the Gastropods are adapted for breathing
air, the mantle-cavity being altered into a lung and the gills be-
ing rudimentary (cf. VII, 12); they form an important order Pul-
monata, a key to the structure of which is furnished by the pond-
snail figured above. It belongs to a sub-order, the members of
which ( Basommatophora) have the eyes at the bases of the
tentacles, and possess thin shells, which may be spiral like Lim-
ncea, or spiral and dexiotropous like Physa, or coiled in one

plane like Planorbis, or
simply conical like An-
cylus (Fig. 159). Move
numerous, however, are
the land -snails and slugs
which carry the eyes at
the tips of the tentacles
(Stylommatophora), and
which include shelled
Fig. 159.-Shells of fresh water Gasteropoda. formslike Helix.Zonites,

Pulmonates— 1, Helix; 2, Succmea; 3, Physa ; '

4,Jncylus; 5, Plaaorbis., Prosobranchs,— 6, Fain- SuCClliea and forms With

dina, with the operculum in the aperture ; 7, Gonw

basis. a rudimentary internal

shell like Limax.

21. A second order of Gastropods— Prosobranchiata— includes, for the
most part, marine forms, differing from the Pulmonata in possessing a
gill in the mantle-cavity, and, usually, an operculum carried on the foot for
closing the aperture of the shell. The ordinal name is derived from the
fact that the respiratory organ is situated in front of the heart, as it is in
the Pulmonata. Great variety of colour and form characterizes the shells
of the Order, the Chitons, e.g., having a shell formed of eight transverse
pieces, the Limpets (Patella), a simple conical shell, while endless va-

HIGH SCHOOL ZOOLOGY,

235

rleties of spirals are to be met with in the Top-shells, (Turbo and Tro-
ehus), Olives, Cone-shells, Cowries (Cyprcea), &c., &c. Some few Proso-
branchiates, such as Helicina, Valvata, Paludina, are met with in fresh
water (Figs. 159, 6 and 7).

22. In the Heteropoda we

have a series of Gastropods
adapted for a pelagic life, the
foot being compressed into a fin,
and the visceral mass and its
protecting shell much reduced
in size, so as not to interfere
with the transparency of the
creature (Fig. 160) ; and in the
Opisthobranchiata, a series of
marine forms, in which the
shell is small or absent, but the
gills generally project free from
the surface of the body, and are
situated behind the heart (Fig.
161).

Fig. 160.— Outline of
a Heteropod (Atlanta).
The foot is divided into
three regions : pro- meso-,
and meta-podium. On the
mesopodium is a sucker,
on the metapodium, an
operculum.

Fig. 16L
A naked
Opisthobran-
chiate (Doris).
A rosette of gills
surrounds the
anus.

23. The Gastropods are the only Class of Cephalophorous Mol-
luscs which are represented inland ; the others are exclusively
marine, and embrace comparatively few living forms. They are
contained in three Classes, the Scaphopoda or Tooth-shells, with
burrowing foot and numerous slender tentacles (Fig. 162 o), the
Pteropoda, pelagic forms with or without a shell, but with the
foot converted into two wing-like fins (Fig. 162 c), and the
Cephalopoda, at present a small group in comparison with its
development in past geological times (Fig. 162 a). To
this class belong the most highly-organized Mollusca — the
Cuttle-fishes (Sepia), Squids (Loligo), Octopus, &c.; in all
of which the shell is reduced to an internal " cuttle-bone *
or "pen." The foot is partly transformed into a circlet of
ten or eight " arms " surrounding the mouth and carrying for-
midable suckers, and partly into a u funnel," which permits the
water used in respiration to be forcibly ejected from the mantle-

236

HIGH SCHOOL ZOOLOGY.

cavity, and thus to be employed for swimming. Horny jaws
bound the aperture of the mouth ; and the nervous system and
sense-organs, which are protected by a cartilaginous endoskele-
ton, attain a degree of development not to be met with else-
where among the Invertebrates. These forms have two gills

Fig. 162.— a, a Cephalopod (£o%o) ; 6, a Scaphopod (Dentaliuiri) ; c, a Pteropod
{Eyalea).

m, mantle-margin of Loligo ; /. the funnel ; /], the fins of Hyalea, between them the
mouth ; m1, processes of the mantle-margin.

(Dibranchiata) in the mantle-cavity, but the Pearly Nautilus
(N. pompilio) has four (it is a Tetrabraachiate form), and it
further diners from the cuttle-fish in the number of the oral
subdivisions of the foot, in the presence of an external chambered
shell, and the absence of the ink-bag, (a very characteristic
organ of defence of the Dibranchiata, which furnishes the

HIGH SCHOOL ZOOLOGY. 237

" sepia " that they diffuse around them for concealment). Al-
though fossil Dibranchiate forms are not uncommon (Belem-
nites), yet the bulk of the fossil Cephalopods belong to the Tetra-
branchiata, the chambered shells of thousands of different species
furnishing to the Palaeontologist means of recognizing the rela-
tive age of the rocks in which they occur.

MOLLUSCOIDEA.

24. Two classes of animals require to be noticed in the present
chapter, which have been associated together as the sub-king-
dom Molluscoidea, partly on account of real, and partly on ac-
count of fancied affinities to each other and the Mollusca proper.
These are the Brachiopoda and Polyzoa ; the former, long con-
sidered to be related to the Lamellibranchs on account of the
possession of a bivalve shell ; the latter, on account of their
forming colonies, formerly classed with the " zoophytes " to be
described in the following chapter. There is no superficial re-
semblance between the two classes themselves, but zoologists
have determined by studying the development of both, that they
are not only related to each other, but also to the Vermes.

25. The Brachiopods are exclusively marine animals, compara-
tively few species of which survive to the present day ; in past
geological periods, however, they were extremely numerous, and
have, therefore, much of the same interest attaching to them as
the Trilobites and Tetrabranchiate Cephalopods. Most of the
living species are found in the warmer seas ; of the few that
occur in the Gulf of St. Lawrence, Rhynchonella jisittacea is per-
haps the commonest. This species exhibits the characteristic
inequality of the two valves of the shell (Fig. 163), the
smaller (dorsal) valve fitting like a lid on the larger (ventral)
valve, which also has a projecting beak permitting the passage
of a short stalk by which the animal is attached. These valves

238

HIGH SCHOOL ZOOLOGY.

Fig. 16S.— Rhynchonella plena.

Chazy Formation. eggS are to be IOimd

are secreted by mantle-lobes, which, of course, have likewise a
totally different relation to the body
from what exists in the Lamellibranchs.
Their edges are beset with setae, like
those of worms, and they contain pro-
cesses from the ccelom in which the
The animal is

confined to the attached end of the shell (Fig. 164) the roomy

mantle-cavity being Q

occupied by a pair of

coiled-up arms, fring- s&^j&y^ Ishk ir

ed with tentacles,

which take their ori-
gin on either side of a

the mouth. These

arms (at one time

supposed to be equiv-
alent to the Molluscan

foot-

OI the Class — ) are municating with the oesophagus in front, and the intestine

often supported by abehind; d'°Penin^ o, dosing muscles. '
calcareous endoskeleton ; such is not the case in Rhynchonella,
but in some of the fossil forms (Fig. 165), the complete skeleton

is well preserved. It is obvious,
then, that the arms are not for
locomotion ; their chief function
is to bring food to the mouth, and
this is effected by cilia on the
tentacles, which, create a current

Fig. 165. -Internal surface of dorsal valve down the coils to the mouth.
of a Spirifer. Qne QV ^WQ pa{rs Qf nephridia

are present, more nearly resembling those of Vermes than of
Mollusca, The intestine ends blind in Rhynchonella and other
forms which have a hinge to the shell (Testicar dines), but in

Fig. 164.— Diagram of Rhynchonella, as seen from the
, •, side with the shell partly removed,

-nence tne name a% anterior ; b, posterior or hinge area of shell ; p.

HIGH SCHOOL ZOOLOGY. 239

Lingula, (a form with a long flexible peduncle, which can
displace laterally the upper valve of its shell owing
to the absence of a hinge — Ecardines) the intestine
turns forwards and opens near the mouth. Lingula
is an example of a " persistent " type, as the generic
characters do not appear to have altered from
Fie 166 -L Paleozoic times (Fig. 1 66).

Levis forma- Although the adults are attached forms, the larvae
are free ; they are decidedly worm-like, being formed
of three segments, the hindmost of which becomes transformed
into the stalk, the foremost becomes much reduced, while the
middle one gives rise to the body and mantle-lobes.

26. Like the Brachiopoda, the Polyzoa are bilateral animals,
sedentary in their adult condition ; they possess a circlet of tenta-
cles about the mouth, and are protected by a shell secreted by
the skin, but in other respects no resemblance is to be detected
between them, except during developmental stages. The fact
that the Polyzoa almost invariably form colonies by budding at
once separates them from the forms heretofore studied ; it is to
this peculiarity that the class owes its name.

With the exception of Cristatella (Fig. 167), the colonies are

permanently sedentary, being
attached by an extensive or
limited surface. According
to the relative position of the

Fig, 167.--Colony of Cristatella, attached to buds theY ^ay be, in the

stem of pond-weed. former case, massive, encrust-

ing or straggling, in the latter, foliaceous or arborescent (Fig.
168). The moss-like form of the colonies has gained the class
the alternative name of Bryozoa. Each individual in the colony
secretes a " cell " into which the head with the crown of

240

HIGH SCHOOL ZOOLOGY*

tentacles may be withdrawn for protection, and these cells
together with connecting tubes constitute the " ccenoecium."
It may be of very different character in different forms, being
sometimes gelatinous, but oftener horny or calcareous. The
colonies may reach a considerable size, but the individuals
rarely exceed one or two lines in length.

Most of the Polyzoa fall into two orders, which are nearly
co-extensive with the Fresh-water and Marine forms respec-

Fig. 168.— Portion of a colony of Plumatella enlarged.
1 and 2, expanded individuals ; 3, 4, 5, individuals in various stages of retraction
into the cells, a, the lophophore ; b, oesophagus ; c, stomach ; d, intestine ; e, anus ;
/, statoblast, attached to base of stomach.

tively. The former, which are abundant in our ponds and
streams, have a horse-shoe shaped row of the ciliated tentacles
and a cover (epistome), which closes the mouth (Phylactolaemata);
the latter (Gymnolsemata) — of which Paludicella is the only
Fresh- water example — a circlet of tentacles and no epistome.

Some idea of the form of the intestine and of the mechanism
of retraction into the cell may be formed from Fig. 168. The
nervous system is in the form of a ganglion between the aper-
tures of the intestine, and there are no special sense-organs.

HIGH SCHOOL ZOOLOGY.

241

Neither are special circulatory or respiratory organs present,
but a pair of excretory tubes put the ccelom in communication
with the outside. In addition to in-
crease by budding, the Fresh-water
Polyzoa give rise to new colonies by
winter-buds or statoblasts, which are
protected by a double horny shell (often
Ornamented with hooks — Pectinatella,
Cristatella — (Fig. 169). These float up

Statoblastof Crista- to ihe surface ** Spring and give rise
at once to new colonies by budding.
In the marine forms, the colonies are frequently polymorphic,
special individuals being modified for prehension alone, others,
so as to act as brood-pouches for the developing eggs. Fossil
remains of such as had calcareous ccencoecia (e.g, Fenestella) are
abundant from the Silurian strata upwards.

Fig. 169.
tella. X25

242

HIGH SCHOOL ZOOLOGY.

CHAPTER IX

The Bemaining Invertebrate Sub-Kingdoms.

1. Four sub-kingdoms, the Echinodermata, Ccelenterata,
Porifera, and Protozoa remain to be referred to ; with the ex-
ception of the last, however, they have but few fresh-wate*1
representatives. In place of the bilateral symmetry of the fore-
going sub-kingdoms, a radial symmetry is often more notice-
able. On this account the groups in question were at one time
known as the " Radiata," but it must be understood that bi-
lateral symmetry may co-exist with the radial.

2. The Echinoderms, exclusively a marine group, receive their

name from the general
presence of an exoskele-
ton formed of more or
less regular calcareous
plates in the skin (Fig.
1 70), which carry pro-
tecting spines. As a rule
the body is formed of
five similar rays or " an-
ti meres " grouped round

Fig. 170.— Echinus esculentus. $. a central axis. The in-
Half of the shell is stripped of the spines, show- , .. . n
ing the double rows of imperforate plates, a; and testine IS usually COm-
of those perforated by the tube-feet-fc ^ and contained in a

spacious coelom, from which there is separated off during
development a system of blood-vessels, and also a characteristic
system of water-vessels. The chief stems of the latter answer

HIGH SCHOOL ZOOLOGY.

243

to the rays, and are provided with
reservoirs, from which water can be
forced into certain short processes of
the stems, known as " tube-feet *
(Fig. 171), which are thus caused to pro-
ject from the surface of the body, so as
to act as locomotive organs.

3. The larvae are extremely unlike
the adults, the developmental stages
recalling in many respects those cf a
remarkable worm-like animal {Balano-
glossus), the organization of which
Fig. m.-Pcntacta frondosa. points to its being a very primitive
A Hoiothuroid with tentacles form, presenting as it does, points of

expanded, and tubc-fect pro- . . . . j ., , .

trudcd; the latter are arranged Contact With Several higher Sub-kmg-
in distinct rows. ,

doms.
4. Of the various classes into which the Echinoderms are
subdivided, the Holothuroidea are characterized by cylindrical
form and a soft skin (Fig. 171). The tube-feet are often con-
fined to a ventral surface so that the animals are then distinctly

Pig. 172. -Sand-dollar from
above. — Eehiiutrachniux par-
ma. ^. The ten double-rows
of plates of which the shell is
constructed may be seen ; the
upper ends of the perforated
rows are modified into peta-
loid ambulacra.

Fit,'. 173.— Pentaceros from above,
A Bahaman Starfish.

244

HIGH SCHOOL ZOOLOGY.

bilateral. The Echinoidea,
on the other hand, may be
| globular (Fig. 170), or discoid
(Fig. 172), but the skeleton is
made up of regular rows of
plates (generally twenty) some
of which are perforated for
the tube-feet. The Star-fishes
(Asteroidea) and Brittle-Stars
Fig.174.-Brittle.Stex. OpMothrtx fragiUs. (0pMuroidea) resemble each

other in having a cen-
tral disc and projecting
arms, which bear tube-
feet only on the ventral
(lower) surface, but
they differ in that the
Starfish arms (Fig. 173)
contain processes from
the intestine, while this
is not the case in the
Brittle-stars (Fig. 174).
Finally, the Crinoidea
resemble the preceding
in having a disc with
arms, but the ventral
surface with the mouth
is uppermost, and the
dorsal surface is tem-
porarily or permanently
fixed by a stalk (Fig.

i>tk\ at • i_ k Upper surface of the calyx with the arms cut off,

175). Along With cer- Showing the mouth in the centre, and the furrows
. ... converging to it from the arms.

tarn allied forms, which

are now quite extinct, the Crinoids were much more abundant

in the earlier geological periods, than they are at the present day.

Fig. 175.— Living Crinoid (Pentacrinm) with part
of its stalk.

HIGH SCHOOL ZOOLOGY.

245

f\Af\

Fig. 176. —Thread-cells of Hydroid. I,, undergoing
development ; II, with the thread protruded.

5. The Coelenterata also are "radiate,"
but the parts are usually disposed in
twos, or fours, or sixes ; instead of the
complete intestine and complicated
ccelom of the preceding group, there is
only one cavity which discharges the
functions of both ; peculiar modified
cells (thread-cells or nettling organs,
Fig. 176), take on a defensive function,
by pouring an acrid poison into wounds
inflicted by their microscopic barbs.
From the tendency to form colonies
(often plant-like in form) this group,
which is almost exclusively marine,
used to be called the Zoophytes.

Apart from some singular pelagic forms which have comb-like
ridges of cilia on the surface (Ctenophora), the Ccelenterates
fall into two classes — the Hydrozoa and the Actinozoa. The
former name is derived from the fresh-water Polyp, Hydra
(Fig. 177), a cosmopolitan form very much simpler in its organi-
zation than its marine allies. It does not form colonies, but
buds off individuals which soon become detached from the
parent. Eggs are formed, during a short period of the year, in
the wall of the two-layered tube which constitutes the body.

Fig. 177. — Hydra viridis, at-
tached to a weed,with buds in
two stages of development.
The expanded tentaclesappear
granular owing to accumula-
tions of thread-cells, a, a
thread -cell.

24ft

HIGH SCHOOL ZOOLOGY.

One end of the tube is closed, and serves for attachment, the
other opens by the mouth, which is surrounded by tubular
tentacles, capable of extraordinary elongation, and employed
for seizing the minute animals on which they feed. Both layers
of the body-wall (ectoderm and endoderm) take part in the
f rmation of the tentacles. Hydra owes its generic name to its
extraordinary power of recovery after injury, any fragment of
an individual being capable of reproducing the rest. The
marine Hydroids form colonies, often arborescent (Fig. 178), the
connecting stems of which are always, and the individuals
frequently, protected by a horny exoskeleton — the perisarc
(Fig. 179). Eggs are formed in peculiarly shaped individuals,

Fig. 179.— Diagram of Hydroid
colony (after Allmnn) b, root or
hydrorhiza: a, coenosarc; a1, peris-
arc; h, modified individual with
reproductive buds (t) about to as-
sume the form of locomotive
medusa? like k; c, nutritive individ-
ual; e, mouth; g, tentacles.

fig. 178 — Hydroid colony. {Obelaria gelatinosa).

HK;Lt SCHOOL ZOOLOGY.

247

which, in some cases, differ very much from the ordinary polyp
in shape, and may even be detached and swim off as Medusce
(Fig. 170). There is then an alternation between the Hydra-
form, multiplying by buds, and the Medusa-form multiplying by
eggs. Some Medusa?, however, the larger jelly-fishes (Fig. 180),
do nob come from Hydroid colonies, but their eggs give rise to
tube-like larva?, which undergo multiplication by division into
young Medusae, related to each other like a pile of saucers. In
such higher forms of Hydroids an abundant layer of gelatinous
connective tissue (mesoderm) separates the endoderm from the
ectoderm.

6. The class Actinozoa (exclu-
sively marine) derives its name from
the Sea-anemone — A ctinia — (Fig.
1°1). These creatures attain a
considerable size, and are often very
brilliantly coloured. They differ
from the Hydroids by having the
mouth-end of the tubular body
turned in as a stomach-sac, which is connected by mesenteries or
septa to the outer tube (Fig. 182). The chambers between
the septa open above into the tentacles,
which are separated from the mouth by
an intervening disc. The Sea-anemonies
have no skeleton, and do not form
colonies, but allied forms give rise by
budding, or division, to colonies, which
may be arborescent or massive, and in
which a skeleton or corallum is a
marked feature. The corallum may
be confined to the axis of the common
flesh (ccenosarc), which unites the indi-
vidual polyps, as in the Fan- corals and
the Bed Coral of commerce (Fig. 183),
or it may invade the polyps them-

Fig1. 180.— Higher Jelly-fish.
(Aurelia aurita).

Fig. 181. — A Sea-anemone (Acti-
nia), a, the mouth; b, the disc ;
c, the tentacles : d, margin of the
disc ; e, the wall ; f, the base.

24$

HIGH SCHOOL ZOOLOGY.

Kg. 182. -Diagram of Actinia
(From Ludwig).

a, tentacle ; b, mouth ; o, stomach-
sac ; d, its opening into coelenteron 1 ;
e, septum ;el, secondary septum ; f, g,
apertures in septum; h, muscular
slips ; i, reproductive organs k, mes-
enteri al filaments.

selves. In the latter case, it may
be only in the form of detached
calcareous spicules, but oftener
the spicules unite into a con-
tinuous structure, which pene-
trates the wall alone (Tubipora,
Fig. 184) or even the septa of the
polyps, forming thus a " cup-coral "
(Fig. 185). Abundant fossil ex-
amples of such cup-corals occur
in the Palaeozoic strata of Ontario,
but the living representatives of
the group are chiefly confined to the
warmer seas of the present day,
where many species contribute to
the formation of the different kinds
of coral-reefs.

Fig. 183. — Red coral. (Corallium rubrum).
P, the calcareous axis or sclerobase. A, coenosarc investing the axis and contain-
ing the individual polyps, B.these are m different stages of retraction ; d, tentacles ;
CB, stomach-sac ; m, mesenteries. The coenosarc is cut through and turned back, so as
|p show the canals (1 and n) which traverse it, and the axis which it covets.

HIGH SCHOOL ZOOLOGY,

249

if. By many zoologists the Porifera or Sponges are regarded
as Ccelente rates, chiefly distinguished by the absence of thread-
cells ; they have so many other peculiarities, however, that it is
convenient to consider them apart. Although one family
(Spongillidce) is confined to fresh-water, and is abundantly
represented in our lakes and streams (Fig. 186), yet it does not

Fig. 184.— Organpipe coral.

(Tubipora musica).

Some of the polyps are expanded.

Fig. \S5.—MicheKnea convexa.
Devonian.

F\g. 186.~-Spongilla lacustris.

contain conspicuous forms, and the word " sponge ' is most fre-
quently connected with the marine animals, whose skeletons we
use in every day life. Yet those are derived from but one

17

250 HIGH SCHOOL ZOOLOGt.

(Spongidce) of very many marine families, and in fact from com-
paratively few species of it. The skeleton in other families is
either formed of calcareous spicules (Calcarea), or of siliceous and
horny material, together or separate (Non-calcarea) ; it is only
in one family of the latter that there is no skeleton.

8. The name Porifera is derived from the presence of
numerous smaller and larger apertures on the surface of the
living sponge, respectively called "pores " and " oscula ;" water,
carrying particles of food, is caused to stream through a more
or less complicated system of ccelenteric canals, of which the
pores are the inhalent, and the oscula the exhalent apertures.
Certain parts of the canals — the ciliated chambers — are lined
by tall ciliated cells of characteristic shape — " collar-cells" (§ 16)
— and it is especially those which are active in bringing about
the current. They are equivalent to the entoderm of the
Ccelenterates, the rest of the canal-system and the outer surface
being clad with flattened ectodermal cells, while the soft, gela-
tinous, connective-tissue between these layers, which constitutes
the bulk of the " flesh" of the sponge, belongs to the mesoderm.

In some cases the ccelenteron, or gas tro vascular cavity, has
only a single " osculum" (Fig. 187), and then the sponge may
be compared to a single Coelenterate polyp, but generally it is a
more complicated canal-system with numerous oscula, and the
resemblance to a Coelenterate colony is lessened by the absence
of symmetry and of constancy in the form of the body and the
position of the oscula.

9. Sponges are only possessed of locomotive powers in their
early larval stages; they afterwards attach themselves, and
possess, therefore, but little muscular tissue. Special sensitive
cells are present in the skin, but there are no sense-organs, such
as are found in the higher Ccelenterates. In addition to the
formation of new individuals from eggs, a separation of buds,

HIGH SCHOOL ZOOLOGY.

251

ilk

\

**$\

or even of parts of the living
sponge, may also give rise to
them. A peculiar kind of bud-
ding occurs in the fresh-water
Sponges, which recalls the form-
ation of the winter-buds of the
Polyzoa, as it takes place under
similar conditions. The buds
are called statoblasts or lt gem-
mules " and are protected by
characteristic spicules (Fig. 183)»

10. Fossil remains of sponges
are abundant in the earlier for-
mations, but they reached the
height of their development
during the upper Secondary
period.

11. The Calcarea are chiefly minute
collar-cells ;" e, osculum. The arrows *_-._,., t^„n a i„ cU„n~,«. ■m**.** ±u
indicate the direction of the current in- forms found m shallow water ; the
wards through the pores, and outwards same is true of the fleshy Non-cal-
through the osculum. _, ,. , . » » -.,

carea — Hamarca, — but most of the

others attain a considerable
size. Some of those with
purely siliceous skeletons,
like Euplectella and Hyalo*
nema, are most beautiful
objects ; they occur in the
depths of the ocean, anchor-
ing themselves in soft mud
by a wisp of glassy threads.
In these forms, there are
triaxial spicules in addition
to the fibres, but in many

snonaes from shallow water ^ m_ Dia?ram of gemmule of a fresh-water
sponges irom snauow water, gpon^e) showing the coating. Gf amphidisks and the

the spicules alone constitute aperture ; b, an aniphidisk of Ephydatia- the river
the skeleton, which may 8Ponge'

Fig. 187. --Diagram of a Calcareous
sponge, with a single osculum.

a, ectoderm ; b, mesoderm, with trira-
diate spicules; c, lining of gastro-vascu-
lar cavity ; /, ciliated chambers lined with

252 HIGH SCHOOL ZOOLOGY.

then "be cork -like (Suberites) or friable in consistence (SponglUa)i One
genus — Cliona — has the singular habit of boring by means of its spicula
into limestone and shells. The sponges of commerce, which come chiefly
from the Mediterranean and the Bahamas, have the skeleton of spongin,
either entirely free from foreign matter (in the best Turkey sponges —
Euspongia officinalis), or else somewhat coarser in texture, from the
building of siliceous spicules and fragments of sand into the horny
fibre (horse-sponges — Hippospongia). Although much variety of form
is to be met with in this family, still wider ranges in this respect are to
be found in other families — not only massive, but tubular, funnel-shaped,
dendritic and encrusting forms being met with.

The Protozoa.

12. AH the foregoing sub-kingdoms have one feature in com-
mon, which is not shared by the lowest forms of animal life \
they pass through certain stages of development consisting of
the segmentation of the egg, and the arrangement of the result-
ing spheres into a blastoderm, which always possesses at least the
two primary layers, ectoderm and entoderm. The tissues, also,
in all are the result of the further division and differentiation
of these spheres ; but in the sub-kingdom Protozoa, to which
we now proceed, development does not take place in this way,
and even the most highly organized forms are unicellular, the
organs of the body being differentiated out of parts of one and
the same cell. These important differences are expressed by unit-
ing the foregoing sub-kingdoms under the one designation
Metazoa.

13. The Protozoa are generally microscopic in size, and, with
the exception of some parasitic forms, are confined to the sea and
to fresh- water. Four classes are distinguished — the Sarcodina,
Sporozoa, Mastigophora, and Infusoria. The two latter are often
spoken of as Flagellate and Ciliate Infusoria, on account of their
characteristic locomotive organs ; neither flagella nor cilia are
piesent in the first two classes ; indeed the Sporozoa, being par-
asitio forms are destitute of any locomotive organs, and, in the

HIGH SCHOOL ZOOLOGY. 253

Sarcodina these are of the nature of " pseudopodia," i.e., less
permanent processes of the sarcode or cell-plasma than the
flagella or cilia, and either thread-like or lobate in form.

14. In passing from the study of the lower to the higher
Protozoa we shall have an opportunity of seeing to what extent
" organization " can be carried within the limits of a single cell.
The Sarcodina offer comparatively little of such differentiation j
food-particles absorbed by the pseudopodia are conveyed into
the softer cell-plasma at any point of the surface, and the undi-
gested remains are similarly thrust out anywhere. Reproduc-
tion is effected chiefly by division into two or many cells, in
some, a resting stage of " encyst rnent," preceding division.

15. Among the simplest is the genus Amoeba (Fig. 189),
called so on account of its ceaseless change of form, the endo-
plasm, which contains the nucleus, is more diffluent than the
ectoplasm which forms the pseudopodia and contains the "con-
tractile vacuole," a structure which appears to discharge the
function of an excretory organ in these and other Protozoa,
The Sarcodina are not all naked like the Amoeba; in the
order to which it belongs (Rhizopoda, — called so on account
of the root-like branches of the pseudopodia in many),
most of the forms secrete shells (Thalamophora), which may
be perforated all over for the escape of thread-like pseu-
dopodia, or have merely one aperture through which similar
processes escape or lobate ones like the Amoeba's. The latter
is the case in Arcella and Difflugia (Fig. 189, 2 and 3), while
iwEuglypha and others the processes are thread-like (Fig. 189, 4).
These are fresh-water forms, in which the shells are formed of
chitinous matter, or of foreign particles cemented together, butthe
marine forms — generally called Foraminifera — have for the most
part a calcareous shell This may be imperforate or perforate, and
is generally composed of numerous chambers disposed in variously
formed spirals (Fig. 190). Although of small size, these Foramini

2bi

HIGH SCHOOL ZOOLOGY.

Fig. 189. —1, Amoeba ; 2, Arcella ; 3, Shell of Difflugia ; 4, Euglypha ; 5, Actino-
phrys, a naked Heliozoon with axial filaments in the pseudopodia ; 6, Clathrulina, a
stalked shelled Heliozoon ; 7, Gregarinid, from an insect-larva ; 8, Encysted Gregarina,
the contents transformed into spores ; 9, Spore from a Myxosporidium.

Fig. 190.— Living Foraminifer : Rotalia veneta.

HIGH SCHOOL ZOOLOGY. 255

fera have a very great geological importance, rocks of the chalk
and other formations being often formed largely out of the
remains of their shells. A deposit of ?a similar nature is being
formed at the present day at the bottom of the Atlantic, dead
shells of Globigerina and similar pelagic forms being rained
down upon the bottom.

16. The pseudopodia in the Rhizopoda may flow together
round a particle of food as represented in Fig. 1 90, but in the
remaining orders of Sarcodina, they are less subject to altera-
tion in form, rarely coalesce, stand out radially from the body,
and are sometimes strengthened by an axial filament. These
orders are the Heliozoa and the Radiolaria, the former a small
group, chiefly of fresh-water forms, sometimes naked, sometimes
with a spicular or perforated shell (Fig. 189, 6) • the latter, a ma-
rine group containing numerous forms with siliceous skeletons,
which offer the most surprising beauty and wealth of form (Fig.
191). The Radiolaria are also important from a geological,
point of view, for deposits of " infusorial earth n are found
consisting almost entirely of their shells, and similar deposits
are being formed in some parts of the ocean at the present day.
The body is more differentiated than in the Heliozoa, the endo-

.-'

3*9

-^

//''i

«,.

Fig. 191.— Living Radiolarian '.—UeUosphcera actinota.

256 HIGH SCHOOL ZOOLOGY.

plasm being separated off by a special " central capsule " from
the ectoplasm. In the latter there are often found minute yel-
low Algse, which appear to live " symbiotically" with the Ra-
diolaria.

1 7. The Sporozoa are distinguished from the Rhizopoda not
only by the absence of pseudopodia,but by the presence of a w< 11-
marked cuticle which limits the contractions of the protoplasm ;
they reproduce by spores, formed by the simultaneous division
of the plasma of an encysted individual into a multitude of glo-
bular bodies, which eventually acquire characteristically-shaped
shells (Fig. 189, 7,.s). They are all parasitic, some of them being
intestinal parasites of the Invertebrates (Gregarinidce), others,
so-called cell-parasites, which multiply in epithelial or blood -cells
of both lower and higher animals, and others, finally, ectopara-
sites of fish, being found on the gill-filaments. The spores of
the last forms have singular lasso-like organs of attachment
(Fig. 189,9.)

18. The name Infusoria ("occurring in infusions " — an indi-
cation of the saprophytic life of many of the forms — ) often
employed for the two remaining classes, was at one time used
to cover a host of microscopic creatures, to many of which, such
as the Rotifers, we have already given some attention ; it is
now restricted to the higher Protozoa, and frequently to those
which are ciliated, the class name Mastigophora being reserved
for those which have flagella. As they undoubtedly include
the simplest forms, which touch both upon the Sarcodina and
the Vegetable Kingdom, they may be mentioned first.

19. Many of the most minute animals belong to the flagellate
Infusoria (Fig. 192), various monads — e.g., Monaster mo — hardly
reaching 1 -2000th of an inch in length. Such a form presents
definite specific characters, however, and retains a definite shape.
There can hardly be said to be a mouth ; rather there is a
vacuole at the base of the flagellum, which takes up food-

HIGH SCHOOL ZOOLOGY.

257

Fig. 192.— Types of Flagellate Infusoria.

1, Monastermo; 2 Ciliophrys in its two stages; 3, Dinobryon, one of the shells
contains an animal which has given rise by budding to a new individual ; 4, Euglena ;
5, Anisonema; 6, Salpingoeca with delicate "collar" standing up round the flagellum ;
7, Ceratium ; 8, Noctiluca.

particles whipped into it. A simpler method of obtaining food
occurs in Ciliophrys, which throws out pseudopodia for this
purpose, and passes into a flagellate stage for locomotion.
Many of the monads form colonies ; Dinobryon e.g., not only
does so, but possesses another peculiarity which is found in many
—the ability to secrete a shell. The most interesting forms
with regard to the process of nutrition are Euglena and its allies.
They are active locomotive forms provided with a mouth, but
the latter serves merely to get rid of the contents of the con-
tractile vacuole, fluid nourishment being taken up through the
cuticular body-wall, as in the lower plants. They further re-
semble plants, by possessing coloured bodies which have the same
physiological significance as the endochrome of the Algae, i.e.,
they serve in the presence of light to decompose carbonic acid,
so that the animal secures part of its carbonaceous food in this
way. Various forms like Volvox, usually regarded as plants,

258 HIGH SCHOOL ZOOLOGY.

might be equally well placed along with these coloured FlageV
lata. There may be more than a single flagellum ; Anisonema,
e.g., has two, one of which is stout and used for springing ;
others have four or six alike in character.

20. A remarkable group, the members of which resemble
the collar-cells of the sponges in form (§ 8), has represent-
atives both in fresh and in salt water. Salpingoeca,
which has both the collar and a case, may serve as an ex-
ample of it. Finally, reference must be made to two forms
of marine Flagellata, which are interesting on account of
assisting in producing the phosphorescence of the sea, in which
they occur in great numbers. Ceratlum may be taken as a
type of the larger group, marked by the possession of a insist-
ent case, and by a second flagellum situated in a groove, which
looks like a row of cilia when in movement. Noctiluca, on the
other hand, attains a much larger size ; it is peach-shaped, with a
tentacle at the head of the groove which lodges the mouth, and
a flagellum and tooth within the groove. It is distinguished by
the reticular character of the protoplasm within the cuticle.

21. As a type of the Infusoria proper or Infusoria Ciliata, one
of the largest and commonest forms, Paramecium — the slipper-
animalcule — found everywhere in water containing decaying or-
ganic matter, may be studied. It attains the size of 1-1 00th of
an inch, and is, therefore, vhible to the naked eye. Mouth and
anus are both present, as they are in all, with the exception of
s me parasitic forms (Opalina), and there is a distinct oesophagus
leading inwards from the mouth to the endoplasm. The body is
uniformly covered with similar cilia (it belongs to the order Holo-
tricha) and there are, in addition, certain thread-like structures —
" trichocysts " — peculiar to this family, which can be thrust out
from the cuticle and seem to have a function similar to that

HIGH SCHOOL ZOOLOGY.

259

of the nettling-organs of the Ccelenterates. Two functions are
discharged by the cilia ; they bring food towards the mouth, and
they serve for locomotion, but the contractile ectoplasm assists
in the latter function. Two contractile vacuoles are present in
this genus, which discharge their contents by radial tubes.
Within the diffluent endoplasm may be seen fcod-particles cir-
culating, which are being subjected to its digestive action; the
nucleus is also situated there. This organ is peculiar in the

Fig. 193 —Types of Ciliated and Suctorial Infusoria.
1, Paramoecium; 2, Opalina; 3, Stentor; 4, Onychodromus ; 5, Vorticella;
6, Acineta ; cv. contractile vacuole ; m, mouth ; v, vestibule, leading: towards mouth ;

n, nucleus ; t, trichocysts ; a, anus ; /, contractile fibre in stalk
border.

r, cilia of " right '

Ciliata and presents many varieties of form (Fig. 193) ; it con-
sists of two parts, a larger and a smaller (the nucleus and the
micronucleus) ; both of these play an important part in the
method of multiplication by fission, which is so common in this
group. They are also active in conjugation, a method of repro-
duction which occurs in other groups of Protozoa as well as in
the Algae.

22. The trumpet-animalcule (Stentor) may be taken as an ex-
ample of another order (Heterotricha) where the cilia which

260 HIGH SCHOOL ZOOLOGY.

surround the mouth — "adoral " — are different from those cloth-
ing the rest of the body ; there is, as it were, a division of labour
between the locomotor and the nutritive cilia. A third order
(Hypotricha) has the cilia confined to one surface, which there-
fore becomes a locomotor surface, and some of the cilia on that
are generally converted into hooks or spines as in Onychodromus,
while the fourth — Peritricha — which contains numerous species
tending to be attached and to form colonies, have the cilia con-
fined to the neighbourhood of the mouth. The Peritricha are,
however, by no means motionless ; they generally have a con-
tractile fibre in the stalk of such forms as the Bell-animalcule
( Vorticella), but they may be free or parasitic forms swimming,
or creeping by their adoral cilia, or they may simply be able
to retract themselves into a shell or case, in virtue of the
contractility of the cell-body.

23. Many of the Peritricha are found living on the surface
of various aquatic animals, especially in such places as the
gills, where they have the advantage of a continuous change of
the surrounding water. Such also is the case in the Suctoria,
a group of Infusoria which begin life with cilia, but afterwards
settle down and replace them by suckers or tentacles through
which, in the absence of a mouth, they take in their nourish-
ment. The suckers are tubular, and communicate with the
endoplasm, to which they carry the juices of the other Infusoria
on which they prey, or of the aquatic animals to which they
are attached. Both fresh- water and marine forms belong to
this group, as well as to the other orders of Ciliata, but the
fresh-water forms are naturally best known.

HIGH SCHOOL ZOOLOGY. 261

CHAPTER X.
General Principles.

1. In the preceding Chapters the principal forms of Animal
Life have been reviewed, a particular standpoint having been
selected in each of the chief subdivisions of the Animal King-
dom. An accessible and, where possible, a primitive type has
been somewhat carefully examined, and the modifications of form
then traced throughout the sub-kingdom or class to which it
belongs. The examination has been confined to the more ob-
vious characters of the adult organism, but occasional references
have been made to minute structure, and to the developmental
stages through which the adult form is reached. It has been
made apparent that zoologists classify animals according to the
degree of resemblance which they exhibit in these respects, and
that, therefore, classification is a Synopsis of the results of such
structural studies.

2. "While it has been chiefly with this — the morphological—
aspect of Zoology that we have hitherto been dealing, other
topics have been incidentally touched upon. It has been made
evident that there is the closest relation between the form of
organs, and the uses to which they are put (whatever may be
the explanation of this relation), that the various kinds of ani-
mals are limited to certain parts of the earth's surface, that the
forms of life at present on the earth are different from those
which occupied it in past times, and that there is the closest
connection between animals and their surroundings. The
present chapter will be reserved for a more systematic discus-
sion of such topics as these, and an endeavour will be made to

£62 HIGH SCHOOL ZOOLOGY.

state briefly the general principles which have been arrived at
by zoologists in regard to them, and to indicate the relations to
each other of the various aspects of zoological study.

3. Zoology is one of the two divisions of biology (that
science which has for its subject-matter all things which have
or have had " life," in contrast to the lifeless objects of inor-
ganic nature), it is, in fact, the Biology of animals, while Botany
is the Biology of plants. It may be asked why, in the face of
the palpable differences which exist between plants and ani-
mals, it should be necessary to have a common term for the
study of the phenomena manifested by both. The answer is,
that the phenomena manifested by living matter in both king-
doms present such a striking contrast to those manifested by
not-living matter, that the study of the difference between them
becomes a question of the first importance. It is not meant
that the matter which enters into the composition of an organ-
ism is different from that of which lifeless things are made, for
there is a constant exchange of matter between the living and
the lifeless world. An organism has been well compared to a
wave formed by an obstruction in a rapid, the shape of which
is approximately constant, but the particles composing which
are incessantly changing. So the living organism is constantly
taking into it matter from the inorganic world around it, and,
as constantly, parting with matter to its surroundings (as we
see in its relations, for example, to the gases of the surround-
ing atmosphere). Nor is it meant that matter in an organism
conducts itself in any exceptional way, for wherever it has been
possible to follow the transformations of matter and of energy
in the living plant or animal, it has been found that these take
place in harmony with laws which have been deduced from, the
conduct of matter in the inorganic world. What then are these
manifestations of " life " and the properties common to plants
and animals, which induce us to regard Zoology and Botany as
parts of a more comprehensive science — Biology ?

HIGH SCHOOL ZOOLOGY.* 26$

4. They may be stated as follows :— (1) Life is always asso-
ciated with protoplasm, which has accordingly been termed the
" physical basis of life." Even in its simplest forms, this sub-
stance is undoubtedly extremely complex from a chemical stand-
point, while in its more differentiated forms, it contains tempor-
arily within it innumerable " organic compounds " which form
a considerable part of the subject matter of Organic Chemistry.
All forms of protoplasm are constituted largely of " proteids "
— complex compounds of Carbon, Hydrogen, Oxygen and Nitro-
gen, with small proportions of Phosphorus and Sulphur, but
they also form within them Carbon compounds of greater sim-
plicity, such as starch, sugar, fat, etc., which, however, do not
occur in nature except as the products of the organic world.
(2) The life of protoplasm (as manifested, for example, by irrita-
bility and contractility) is accompanied by its partial destruction,
and this involves repair by the incorporation and assimilation
of new matter, or, in other words, the ingestion of food and
changes whereby this food can be rendered available for replace-
ment of the material destroyed. (3) If the income of food is
in excess of the expenditure by waste, growth results ; but each
individual organism has a limit of size which it cannot exceed.
A process succeeding the attainment of the full size in the
simplest organisms is that of division, whereupon the life of the
individual terminates and a new generation composed of two
new individuals replaces it. Similar phenomena of death and
reproduction occur also in the higher organisms. Nothing like
these characters is to be met with in the Inorganic world, but this
is not the only reason for studying the life of plants and animals
together, for, apart from the circumstance that there are cer-
tain organisms (IX, 19) which can hardly be said to have struck
out on either of the diverging paths which lead to plant
and animal peculiarities, there is so much interdependence
between the two, that a knowledge of the life of either is not
complete without considering both, and indeed this interdepen-

26*4 HIGH SCHOOL ZOOLOGY.

dence is in part due to the differences which we shall refer to
hereafter. However great these differences are, it must, never-
theless, be understood that the resemblances between plants and
animals are such, that the methods of Zoology are the same as
those of Botany, and the aspects of the study of the Biology of
plants, the same as those of the Biology of animals.

VARIOUS ASPECTS OP BIOLOGICAL STUDY.

(1) Morphological.

5. This division of Biological study involves, as we have
seen, questions of form and structure. It admits of sub-division
according as these questions deal with the adult, or with stages
in the development of the adult : Anatomy, in its widest sense,
being the term reserved for the former group of questions,
Embryology or Ontogeny for the latter. In a narrower sense,
Anatomy is restricted to such structural points as can be
studied without the aid of the microscope, while Histology is
employed for the study of the finer details of the tissues, and
Cytology for those of their component cells. It is evident that
questions, other than those of pure form, must be inseparable
from the studies which have just been styled morphological.
The changes of form, for example, in individual cells are merely
the expression of physical and chemical changes taking place
within them, so that Cytology might as legitimately be referred
to the following aspect of Biological study.

(2) Physiological.

6. Morphology is sometimes described as statical Biology,
because it involves the notion of rest; Physiology, on the
other hand, as dynamical, because it studies the work-

HIGH SCHOOL ZOOLOGY. 265

ing of the plant or animal as a machine, its object being to
follow the transformations of matter and of energy within the
living organism. Although it is a comparatively easy task to
trace how the energy locked up in fuel is made available by the
steam-engine, it is an infinitely more difficult one to trace how
the energy locked up in food becomes available as muscnlar
work ; yet there are other activities of the body which lend
themselves far less easily to measurement than does that of the
muscular system.

It is, then, the various activities of the organism which
Physiology discusses. Function is the term employed for
the role or duty discharged by any part of a plant or animal,
and the part discharging a particular duty is termed an organ
these terms are thus used cor relatively. We have seen that
different kinds of activity such as nutrition, locomotion and
reproduction may be performed by apparently undifferentiated
or little-differentiated protoplasm ; it is therefore necessary
to beware of supposing that organization or differentiation
into separate organs is necessary for the display of the activities
of life, although the term organism would seem to imply that.

7. The various functions of plants and animals may be
grouped as follows : —

(a) Those essential to the process of waste and repair refer-
red to in §4. The process of waste is mainly one of oxida-
tion and involves the formation of waste-products, partly gaseous,
partly fluid, which require to be separated from the tissues:
Respiratory and excretory organs are therefore rendered
necessary. The process of repair, on the other hand, not only
involves the ingestion of food, but its assimilation, and, there-
fore, the nutritive organs first render the food soluble in such
a way that it can be absorbed, and then elaborate it into forms
suitable for repairing the waste. Circulatory organs are sub-
servient to all three systems.
18

266 HIGH SCHOOL ZOOLOGY.

Plants as well as animals are provided with organs of these
three categories, but important differences exist as to the
nature of the processes discharged by them. The food of plants
is drawn from the inorganic world, and consists of salts
absorbed in solution from the soil, and of the carbonic acid in
the atmosphere. This is decomposed by the combined action of
the chlorophyll within the green plant-cells and light — part of
the energy of the sun's rays being intercepted by the colouring
matter — with the result that carbon is secured for forming simple
carbohydrates like glucose, which are afterwards elaborated
within the plant-body, while oxygen is disengaged far in excess
of that required for the ordinary processes of oxidation.

Thus, from simple compounds, in which little energy is lock-
ed up, more complex ones are formed, which are highly energised,
and which thus serve for fuel and food to the animal world.
Animals are, in fact, dependent either directly or indirectly for
their food on the vegetable world, and, as far as we know, not
even the simplest among them (apart perhaps from such colour-
ed forms as are referred to in IX, 1 9) can derive carbon from
the inorganic world.

(b) Even more striking differences between plants and
animals are to be met with in those organs which relate the in-
dividual to its environment ; in fact, the organs of locomotion
and sensation are generally described as the specially " animal"
organs. Not that vegetable protoplasm is destitute of con-
tractility and irritability, but the further elaboration of these
essential properties of protoplasm is characteristic of animals, tf
the exclusion of plants. Nor is it meant that the plant is lejs
adapted to its surroundings on account of the absence of special
organs of relation ; on the contrary, we shall see that the plant
is just as plastic as the animal in its adaptability to its environ-
ment. The difference between them in this respect in no doubt
to be largely attributed to differences referred to in last para-

SIGH SCHOOL ZOOLOGY, 267

graph ; competition for food on the part of animals having 3ed
to the necessity for the complex mechanisms of the muscular
and nervous systems.

The functions of the nervous system include all those pro-
cesses, which, in their elementary forms, appear as the simplest
kinds of " reflex action," such as, for example, the contraction
of the Amoeba on irritation, but puss by easy transitions
through higher forms, till those extremely complicated inherited
reflexes, which we call "instincts," are reached, and even those
higher processes, which we ascribe to the " intelligence" of
animals. Such psychical processes, from the simplest to the
most complex, form the subject-matter of Animal Psychology
and Sociology.

(c) The third group of functions is formed by those which
refer to the production of new individuals. Very close paral-
lels are offered by the vegetable and animal kingdoms in re
spect to these, and multiplication by division (separation of the
body into equal parts), the formation of buds (detachment of
smaller portions), or, finally, the detachment of reproductive
cells, and the formation of new individuals from eggs are to be
observed in both. Similar phenomena in connection with this
group of functions are also to be studied in both; such as (1)
the limited span of life of the individual ; (2) the tendency for
succeeding generations to increase in number ; (3) the ten-
dency of the offspring to inherit the form of the parent, and
yet (4) to vary considerably from that form. These phenomena
lead us to the discussion of various other aspects of Biology, in
the first place, of those which exhibit the relations of present to
preceding generations, viz.: Developmental, Palseontological and
Taxonomic aspects.

(3) Developmental and Paljeontological.
8. "We know that the plants and animals living on the earth at
present are the descendants of the immediately preceding gene-

268 HIGH SCHOOL ZOOLOGY.

rations. Further, it is evident, on reflection, that few traces of
these preceding generations are preserved, such is the de-
structive power of the minute saprophytic organisms that live
by pulling to pieces decaying organic matter. Even the hardest
tissues like bone and wood soon crumble to dust, if left to the
ordinary process of decay. Now and then, however, the hard
parts of a dead animal or plant are preserved, as, for example,
when they are washed by a stream to some spot, where they
become silted up by the sediment deposited from the stream,
and thus protected from the destroying influences to which
they would otherwise have been exposed. A reference to the
skeletal tissues described for the various groups of animals in
the preceding chapter, will make it easy to understand what
parts would be likely to be preserved under such circumstances,
although under specially favorable circumstances, impressions
even of the softest bodied animals are to be found. The material
held in suspension by a stream, and deposited as the sedi-
ment referred to, is the result of the wearing down or
denuding of the land drained by it, and it is obvious that
organic remains found in the upper layers of such a deposit
must belong to more recent generations than those found in the
lower layers.

9. Many of the rocks which form the earth's surface have
been formed like the silt referred to, from sediment produced
by the ceaseless action of the waves on the sea-coast, or by the
denuding action of the various atmospheric influences — rain
frost, snow, etc., and swept down by rivers to the shallow waters
of the ocean. Such deposits vary much in their character
according to the material held in suspension by the water, and
result in sandstones, limestones, shales, etc., but they all
exhibit a tendency to layering or stratification, depending on
the way they were formed, and are, therefore, called Sedimen-
tary Strata. The relative age of such strata is determined by
their position, and it will be readily understood that the upper-

HIGH SCHOOL ZOOLOGY. 269

most or most modern layers will be most like those that we
actually see in process of formation, while the oldest or lowest
will have been subjected to many changes, such as pressure
from those above, upheaval from disturbances of the earth's
crust, etc. Now, the examination of the remains of organic
life — fossils — preserved in these sedimentary rocks (an import-
ant branch of Biology — Palaeontology — ) shows that only
a comparatively thin layer of superficial deposits contains
remains of organisms like those at present alive ; the deeper
down we go, the more do we find different species of plants and
animals replacing those familiar to us, until the latter disap-
pear completely and leave us in the presence of an entirely new
fauna and flora. The question now arises, — have the species of
plants and animals now living on the surface of the globe, and
whose remains are found in the superficial deposits, originated
entirely independently of the different species found in deeper
strata, or are the ancestors of the former really represented
among these unfamiliar remains, only unrecognizable at first
on account of differences, which the recent forms have accumu-
lated in the course of long ages 1 The latter solution of the
question is the alternative generally accepted at the present
day, and it will be seen that it involves relationship by descent
of the present species of plants and animals to some of those ot
former epochs, others having died out or become extinct with-
out leaving any descendants, just as has been the case within our
knowledge of modern species (V, 15, 23 ; VI, 22). Not only
does it involve descent, but descent with modification, and indeed,
when we look at the forms of life in the o]der rocks we recognize
that the modification must have been of a very profound nature.
It has, furthermore, been of a definite, orderly character,
because we find that the lower classes of plants and animals
have appeared before the higher classes — fossil Mammalia, for
example, being found only in comparatively recent strata.
There has thus been (if we accept the view that the present

270 HIGH SCHOOL ZOOLOGY.

forms of plants and animals are the modified descendants of
other species now extinct) a continuous development from
lower to higher forms, presenting in its entirety what is
often called the evolution of organic Nature. It is, in fact?
possible to subdivide the sedimentary rocks according to
the prevailing kinds of life during their deposition, into
Archaean — which contain few, if any, traces of life — and Palaeo-
zoic, Mesozoic, and Kainozoic, in all of which fossils are abun-
dant, but the last of which alone contain any resembling the
forms of life at present on the earth. Some information may be
gleaned from the accompanying Table as to the characteristic
plants and animals of these various periods, and as to the order
of their introduction. Not only is the appearance of the life of
these periods characteristic, but the classification is assisted, in
Europe at least, by the occurrence of conspicuous 'breaks'
between them, which indicate, for example, that the Palaeozoic
strata were elevated into dry land, partly denuded and
upheaved, before they again sank, and had the Mesozoic strata
laid down upon them uneonformably — i.e. not in plains paral-
lel to those below as if they had been deposited consecutively.
Such breaks do not, of course, occur at the same ' horizon ' in
other parts of the world, but the classification from the pre-
vailing kinds of life answers all over the world. Each age is
again divisible into various epochs, which are marked by more
or less distinct breaks in different places, and also by charac-
teristic fossils, so that the geologist is enabled to recognize the
rocks of any particular horizon by diagnosing the contained
fossils.

10. An important question which comes up in connection
with these strata, is that of their age, and, consequently, that
of the contained fossils. If we assume that the rate of deposi-
tion has been uniform throughout the various strata, then the
maximum thickness may be taken as a measure of the relative
duration of the time during which they were deposited. The

HIGH SOiiOOL ZOOLOGY.

271

TABLE OF THE SEDIMENTARY ROCKS,

Showing their relative age and thickness, and their cJuiracteristie rock-
formations, plants and animals.

Agr or
Period.

Quaternary
or

Post-Kuiv'c.

Epoch.

Characteristic Rock-
Formatioxs.

Tertiary

or

Kainozoi£.

Uecent

• Post-glae.

Glacial

Pliocene
Miocene
Eocene

Cretaceous.

Jurassic.

Triassic.

Permian.

Carboniferous

Devonian.

Silurian.

Cambrian.

Huronian.

Laurentian.

Indian shell-mounds.

Raised beaches, shell-marls, loess

Boulder-clay, " till " or drift.

Loams, sands, shales, clays, &c.

Charac.
Plants.

Cultivated
plants.

Angiospenn-
ous Phanero-
gams.

Lignites, limestones, clays, and
sandstones,

Marls and limestones.

Red sandstones and conglom-
erates.

Limestones, sandstones
and marls.

Coal measures and car-
boniferous limestones.

Sandstones, limestones
and shales.

Sandstones, limestones
and slates.

Gneiss, mica-slate and

various crystalline

rocks.

Conifers

and
Cycads.

Vascular
Crypto-
gams.

Algaj.

Charac.

Animals.

Man.

Mammals,

Reptiles.

Amphibi-
ans and
Fishes.

Inverte-
brates.

Eoeoon (?)

272 HIGH SCHOOL ZOOLOGY.

accompanying table shows graphically that the Mesozoic Strata
are about one-ninth the thickness of the Palaeozoic, and it ought
to represent the Kainozoic as about one-fifth of the Mesozoic,
and the Post-Kainozoic as one-fifth of the Kainozoic, but
the exigencies of printing have made the Kainozoic, and
especially the Post-Kainozoic, too thick.

Various calculations have been made as to the absolute time
the deposition of the sedimentary rocks has required ; these do
not rest on very certain data, but their results come between
thirty to sixty millions of years, and are chiefly interesting, as
convincing us of the length of time that has elapsed since the
appearance of life upon the earth.

(4) Taxonomic or Classificatory.

11. Returning to the question of the descent of present forms
of life from past forms, it will be observed that it throws a new
light on the terms " allied" and " related," so frequently used
in the preceding chapter : — the greater or less resemblance of
structure, on which classification is based, is due to community
of descent, — to more or less distant blood-relationship.

To facilitate the study of relationship between individuals,
genealogical trees are framed on documentary evidence, and
similar trees have been constructed (going beyond historical
times) to show the relationship of nations to each other. The
kind of evidence used in the latter case has been partly that
obtained from observation of the nations at present, (especially
the structure of their language, their folk-lore, etc.,) and partly
of a palseontological nature, such as the contents of tombs, and
implements, weapons, etc., preserved in the most superficial
deposits.

Going further back, however, into geological time, attempts
have been made to construct similar trees, to show the relation-
ship of different groups of organic life to each other (phylogeny),

HIGH SCHOOL ZOOLOGY. 273

but it will be understood that although the advance of Mor-
phology is constantly improving our evidence from the living
forms, and although hitherto undiscovered fossil species are
constantly being unearthed, yet the evidence from the palaeon-
tological side must always be incomplete (§ 8). Phylogenetic
classifications must, therefore, be tentative, except in the case of
such modern groups as are distinguished by the profuseness of
their fossil remains. The genealogical tree of the Animal
Kingdom might be described as buried, with the exception of
the terminal green twigs — the existing species ; to trace the
connection between these it is necessary to dig down into the
sedimentary strata, and to piece together with infinite patience
the fragmentary evidence which we there find. It must be
remembered, however, that the principle of correlation depending
on the constant association of morphological peculiarities (such
as, for example, a ruminant dentition with a particular conform
ation of the skeleton of the foot), justifies us in making use of
evidence from very fragmentary remains.

12. Such studies may, then, indicate the probable line of de-
velopment which has culminated in a particular species ; the dis-
cussion of the nature and origin of species will be deferred to a
subsequent section. In the meantime, in connection with the
foregoing topics the accompanying table may be of use, which
gives an approximate estimate of the number of described
species in the various classes and orders, and serves to show
what groups of animals are in " ascendance" at the present day,
as exhibited by their comparative wealth in species, and to call
attention to the former wealth as compared with the present
poverty of such groups as the Brachiopods, Cephalopods, Crinoids,
Pteropods, Trilobites, etc. It makes it apparent, also, how cer-
tain highly specialised groups, such as the Teleosts, the Anura, the
Passeres, the higher Insecta, preponderate over more primitive
allied groups.

274

HIGH SCHOOL ZOOLOGY.

TABULAR VIEW OF THE CLASSES AND ORDERS

OF THE ANIMAL KINGDOM,

Showing their relative richness in species.

Living.

Fossil.

I. — Vkrtkbrata —

A. Urochorda or Tunicata.

270
30

1

Class H.~Thaliacea

B. Cephalochorda.

b. Craniota.

Class I.— Pisces

1000+

Sub-class — I. Cyclostomi

17

2S5

32

4

2500
125
177
370
640

30>i0

93

800

22

4. Dipnoi

5. Teleostei

Class II. — Amphibia.

0. 1. Urodela

2. Anura

100

300

250

21

1250

1000

2. Crocodilia

4. Ophidia

Class IY.—Aves

300 .

80
228

60
180
140

17
400
360
540
500
325
736
400
5700

4. Anseres

fi Grallap / Paludicolse \
b. Grallae j Limicolffi J . .

10. Raptores

11. Macrochires

12. Pici

15. Passeres

HLGH SCHOOL ZOOLOGY.

275

TABULAR VIEW— (Continued).

Class V. — Mammalia

0. 1. Monotremata

2. Marsupialia

3. Edentata

4. Cetacea

5. Sirenia

6. Perissodacryla

7. Artiodactyla

8. Proboscidea

9. Hyracoidea

10. Rodentia

11. Insectivora

12. Pinnipedia .

13. Carnivora

14. Chiroptera

15. Lemuroidea

16. Primates

II.— Arthropoda—

Class I. — Crustacea.

Sub-class— Malacostraca (higher orders)

Entomostraca (lower orders)

Gi^anrostraca and Trilobitae

Class ll.—Aracknida.

O. 1. Arthroffastra(Scorpionina
Phalantjina, &c.)

2. Acarina

3. Araneina

Claxs III.—Myriapoda

Class IV.—Insecta.

O. 1. Thysanura

2. Orthoptera

3. Neuroptera

4. Hemiptera

5. Diptera

6. Lepidoptera

7. Hymenoptera

8. Goieoptera

Living.

Fossil.

lEL — Vermes

IV. — Mollisca— ■

A. Acephala.

Class I. — Lamellibranchiata

B. Cephalophora.

Clan If. — Scaphopoda

Class JI I.— Gastropoda.

O. 1. Prosobranchiata . .

2. Pulmonata

3. Opisthobranchiata

4. Heteropoda

< Ian I V. — Pteropoda,

O. 1. Gymnosomata . . .
2. Thecosomata

149

42

155

5

23

250

2

12
800
150

30
340
415

55
219

3525

2075
5

250

900

2500

100

6000

1000

14000

18000

20000

25000

80000

5500

5000

SO

9000

6000

900

60

150

600
1760

40
2600

9000
160

6000
600

160

276

HIGH SCHOOL ZOOLOGY.
TABULAR VIEW— (Continued).

Clans V. — Cephalopoda.

O. 1. Tetrabranchiata
2. Dibranchiata . . .

V. — MOLLUSCOIDKA —

Class I.—Brachiopoda.

O. 1. Testicardines . . .

2. Ecardines

Class II. — Polyzoa.

O. 1. Phylactolaemata
2. Gymnolsemata . .

VI. — ECIIINODKRMATA—

Class I. — Holothuroidea

" //. — Echinoidea

" III. — Ophiuroidea

" IV. — Asteroidea

" V. — Crino. dea

" Vl.—Cystoidea

" VII- Blastoidea

VII. — COSLKNTERATA—

Class I.—Ctenophora

" II.—Hydrozoa

" III. — Actinozoa

VIII.— PORIFKRA

IX.— Protozoa —

Class I. — Sarcodina.

0. 1. Rhizopoda

2. Heliozoa . . .

3. Radiolaria .
Class II. — Sporozoa

" III. — Mastir/ojthora

" IV. — Infusoria

Living.

4
140

50

440
300
700
500
430

45

1100
1800

700

40

2600

55

290

500

Fossil.

4200
310

2200
400

1850
2000

1170
140
90

1800
800

1500
400

* The fossil remains of Vermes, which consist chiefly of the tubes of tubicolous
Annelids.and the jaws of Errantia, are too \mcertain in character to allow of numerical
estimate.

HTGn SCHOOL ZOOLOGY, 277

13. The preceding paragraphs have been devoted to the rela-
tions existing between different generations of organisms ; nc
less important are the relations of the individual or the species
to other organisms and to its inanimate surroundings. Ques-
tions of this character have been styled Mesological, as dealing
relation to the " environment," but it will be more convenient
to deal separately with the relations to the different elements of
the environment, discussing, in the first place, the distribution
of animals in space, which we shall find to be explained partly
by the past configuration of. land and water, and partly by
climatic influences. These aspects of Biology are, therefore :

(5) Geographical and Climatic.
We are apt to think of the present distribution of land and
water as something unalterable, and of climate as chiefly a mat"
ter of latitude and longitude, but a little consideration will show
that not only is the latter dependent on the former, but that
both have been, again and again in the history of the earth, sub-
jected to change. In respect to the one point, we have merely
to compare the mild winters of Britain with those of Labrador,
or our own with those of the Biviera. The differences are attri-
bu table, in the one case, to ocean currents, in the other to our
situation in the heart of a great continent. In respect to the
other point we can find evidence of profound changes at our own
doors. Wherever we find sedimentary rocks there we realize
that the land in question has been submerged in the ocean, and
often that this has occurred, not only once, but repeatedly in the
course of geological time. Ontario, for example, is everywhere
underlaid by sedimentary rocks; those which contain fossils were
evidently formed at the bottom of Cambrian or Silurian seas, but
the fact that we do not find any trace of the Upper Palaeozoic or
Mesozoic or Kainozoic strata covering them indicates that it has
been long exposed to the denuding effects of the atmosphere.
Again, the superficial deposits which cover these old formations,

27$ HIGH SCHOOL ZOOLOGY.

and which belong to Post-Kainozoic Age, show that compara*
tively recently, Ontario, with the greater part of North America
as far south as Washington, was covered by an Ice-Sheet, so
that then the whole country resembled the present desolate and
lifeless interior of Greenland. Can it be doubted that such
changes taking place all over the world must have had the most
important influence on the distribution of life 1

While we recognize a distinction between tropical, temperate
and arctic faunas and floras, and are obliged to infer climatic
changes if we find that Magnolias flourished in Spitzbergen dur-
ing the Miocene epoch, and that Hippopotamuses wallowed in
British rivers in the intervals of successive Ice-Sheets, yet we
must be careful not to attribute too great an influence to climate
alone, without taking into account the geographical changes to
which the climatic ones are secondary.

14. That such changes have been both recent and profound
will now appear from some of the facts of distribution already
cited, and the explanation of these offered by palaeontology.
First, however, let us look into the causes and effects of that
Glacial Period, during and after which the surface deposits of
Ontario were formed.

There are certain regularly recurring astronomical conditions,
which affect the relative length of winter and summer, and
which are dependent (1) on the relative proximity of the poles
to the sun during these seasons, and, (2) on the amount of
eccentricity of the earth's orbit. The relative proximity to the
sun in winter of the North and South Hemispheres is reversed
every 10,500 years, but the amount of eccentricity varies much
more slowly. Now, jt is at its minimum; between 100 and
200,000 years ago it was very great, with the result of alter-
nating periods of 10,000 years of long, cold winters, and short,
hot summers, with the reverse. It is believed that these con-
ditions, occurring simultaneously with large elevations of land

HIGH SCHOOL ZOOLOGY. 279

within the Arctic Circle (where, as we know from fossils found,
there had been warm seas during the Miocene epoch,) had the
effect of producing the glaciation. It must not be supposed
that the Glacial Period lasted with undiminished severity dur-
ing all this time; we have evidence of interglacial milder
periods, when the Ice-Sheet retired, and the life, which had been
driven towards the south, again crept northward, but these very
alternations must have been a fruitful source of change in the
fauna and flora of the countries subjected to them.

15. Apart from the combined effects of the astronomical con-
ditions referred to, and the raising of the land towards the North
Pole, let us consider the effects of a general elevation of the sea-
bottom outside the present shore-line, to an extent far less than
we know to have taken place within comparatively recent times.

The summits of some of the Alps — the Dent du Midi, for
example, 10,770 feet — are formed of Nummulitic limestone, a
formation consisting largely of shells of Foraminifera, deposited
during the middle Eocene epoch, and elevated since then. Now,
we know from hydrographic researches that if an elevation of the
shallower waters of the world to half this extent were to take
place, that it would entirely alter the configuration of the land.
Not only would Great Britain be continuous with France, Den-
mark and Norway, but the whole of Europe, Africa and Asia
would form one continuous Continent. It would be even possible
to travel by land from England to Canada, via Iceland, Green-
land and Labrador, and then on to Siberia by Alaska. The only
large tracts of land remaining unconnected with this vast Con-
tinent would be Australia, which would still be an Island, and
Madagascar, which would still be separated from Africa.

Ample evidence exists, and some of it has been already re-
ferred to (VI. 30), which shows that changes of such a character
have occurred, not necessarily simultaneously, but at least at
different times. The Camel family, e.g., flourished m North

HIGH SCHOOL ZOOLOGY

America in Miocene times and spread thence to South America
and to Asia where they had not previously existed, but to which
the distribution of the modern form is limited. Again, the primi-
tive forms of the Tapir family lived in Europe during the early
part of the Eocene epoch, they spread during the later Eocene
and Miocene epochs to North America, where, however, they
died out without leaving any descendants, but they persisted in
Europe, where they gave rise to the modern Tapirs, and these
again spread to Asia and South America, where alone the
modern species occur.

That Madagascar was at one time connected with Africa, we
gather from the survival on the mainland of some of those pe-
uliar lemurine forms, which are so characteristic of the Island.
But these have almost been exterminated from Africa by the
contact of the higher Eutheria, so that we conclude that the
connection with Africa was submerged before the influx of the
higher mammals from Eurasia. The persistence of the Proto-
theria and Metatheria in Australia is similarly to be attributed
to its long independence from Asia.

The fauna of Great Britain, finally, can only be accounted for
on the assumption that since the Glacial period it has been en-
tirely submerged, raised again, and populated from the main-
land, but again submerged before this repopulation could become
complete. The freedom of Ireland from reptiles is not to be
attributed to any unsuitability of climate, but to the fact that
the channel was not dry land sufficiently long to allow these
forms, which are slow at distributing themselves, to reach it.

1 6, Such facts lead us to the position that the geography of the
past has had the most important influence on determining the
geographical zoology of the present. Each species has a certain
area of distribution, which is called its habitat : it tends to
widen this area, as far as the conditions of existence will per-

HIGH SCHOOL ZOOLOGY. 281

tuit, but the most effectual barriers are high mountain-chains
and deep seas. By mapping out the ranges of different species
it is possible to mark out certain zoogeographical regions in
which the simultaneous occurrence of the same or nearly allied
species confers a certain similarity of appearance or facies to the
fauna. A glance at these regions, as laid down by Dr. Wallace
in the accompanying map, will shew that they agree pretty
well with our ordinary geographical divisions, except that great
natural barriers cut off the Ethiopian region from North Africa,
the Oi iental from the Palsearctic, and the Australian from the
Oriental ; these are the Sahara, the Himalaya, and the very
deep sea along " Wallace's line," between Bali and Lombok,
Borneo and Celebes. This is certainly a most instructive
illustration of the effect of a deep-sea barrier, and of the fact
that mere climate does not determine geographical distribution.
From Bali to Lombok is hardly twenty miles, and yet there is
more difference as to the fauna between these two islands, the
climate of which is practically identical, than there is between
Canada and Florida.

17, Although the distribution of aquatic animals admits also of
geographical treatment, it is obvious that the barriers to their
spreading far and wide must be of very different character, and,
apart from those forms confined to the shore by limited loco-
motive powers, must be largely due to ocean currents, tempera-
ture and other surrounding conditions. Other elements of
interest, however, exist in connection with them —their occur-
rence in fresh or in salt water, and their bathymetrical distri-
bution— i.e., the depth at which they occur.

The greatest profusion of life is found in the shallow waters
of the shore-zone, but recent observations have shown that it
also abounds in the depths of the sea, even down to four or five
miles. Again, there are so-called pelagic forms which live on
fehe surface-waters of the open sea, and are only occasionally
19

282 HIGH SCHOOL ZOOLOGY.

driven upon the shore. It is believed that the littoral fauna
originated from the pelagic in the first place, while many pel-
agic forms, such as the whales, are undoubtedly derived second-
arily from shore forms. The origin of fresh-water faunas is
another point of great interest ; certain stages through which
they must have passed may be seen in the mouths of rivers
where different species extend upwards to a greater or less dis-
tance, according as they are more or less tolerant of the dimin-
ished salinity of the water. That part of the fresh- water
animals are so derived may be gathered from such cases where
they exhibit little or no difference in their new habitat, (VI, 34,
VII, 1 3). There are many curious facts in the distribution of the
fresh-water fishes, which indicate the early separation of some
groups from marine forms, and which can only be explained
by realizing that changes in the configuration of the land
must have involved many changes in the great water-courses.

In inland lakes we have also littoral, deep, and pelagic
faunas, the study of the nature and origin of which offers a wide
field of inquiry in Ontario. Before leaving the subject of the
distribution of animals in water, it may be noted that not only
do ocean currents affect the ranges of aquatic, but also of ter-
restrial organisms, so that, apart from their climatic influence
on these, they may frequently transport animals and plants to
new points at considerable distance from their original homes.

(6) Relations of Animals to the Conditions of
Existence and to each other

By climate we mean temperature, pressure and other atmos-
pheric conditions, which do not seem to determine any con-
spicuous differences of form, but there are other conditions of
existence which do seem to be always associated with corres-

HIGH SCHOOL ZOOLOGY.

283

ponding differences of structure ; such are the association of
underground life with the absence of eyes and of colour (II, 79 ;
III, 12) ; and that of the shape of the body with the medium
and mode of locomotion (Fig. 194). These offer a very tempt-

Fig. 194.— Harp Seal Phoca groenlandica'(from Brehm).

ing field for investigation, and cause us to enquire how changes
in surrounding conditions and in habits affect animal life.

19. Reference has already been made to the fact that organisms
tend to increase in number in geometrical progression. Some-
times countless eggs are produced by a single individual, but in
such cases few of these reach maturity, and it is only now and
then that we are startled by the disproportionate development
of some one species, disturbing the course of Nature. When,
however, one generation exceeds the previous one, even in the
proportion of two to one, it is evident that there will soon be a
competition or struggle between the individuals for suitable
food, and that the strongest and best adapted to survive will be
those, on the whole, that do survive. Along with this we have
to take into account the tendency of organisms to vary and to
transmit their peculiarities to their descendants (§ 7). Those
individuals whose organs vary in such a way as to adapt them
better, however little, to their special circumstances of life, are,

284

HIGH SCHOOL ZOOLOGY.

therefore, rendered better fitted to survive, and will not only-
do so, but will transmit their peculiar variations to their off-
spring ; selection being thus made by Nature of the individuals
best fitted to the existing conditions of life.

20. If those conditions were stable, a persistent equilibrium
of organic nature would be established, and no opportunities
for the development of new species would arise, but the condi-
tions of life are never stable, and consequently we have a greater
or less degree of instability of the balance of life, depending on the
greater or less changes taking place in the conditions of exist-
ence. It is obvious that any apparent equilibrium would be
upset by changes, however gradual, of the character indicated in
§ 14 and 15, and$ therefore, that such changes must be regarded
as those most operative in the production of new forms. A species
subjected to such changes must either produce variations fitted to
cope with them, or else become extinct, perishing at once, or
struggling on under the unfavourable influences, till a depau-
perate condition, such as has been observed in many fossils, as
well as in living forms, is gradually reached. If it is a form
capable of adapting itself, by assuming new habits, it is possible
that (as we see in varieties spread over a wide area) this accom-
modation should proceed along different lines with different
varieties, and therefore, that several new forms would result from
the original species. It is evident that the intermediate forms be-
ing liker the original in character would tend to be eliminated
by their relative unsuitability to the new conditions, and thus,
instead of a series of varieties, we should have two or more new
? species' distinct from each other. Another circumstance,
tending in this direction, is that individuals of a variety tend
to keep together, with the result that comparatively near species
become incapable of crossing, so as to form a mixed race. This
was at one time considered to be an essential feature in the
definition of a species, but several examples are now known
of undoubtedly distinct species, which do form such crossesj
where their areas of distribution come into contact.

HIGH SCHOOL ZOOLOGY. 285

21. The theory stated in the preceding paragraphs is that of
the Origin of Species by Natural Selection, associated with the
names of Darwin and Wallace ; it will be observed that while
resting upon the large amount of variation offered, it does not at-
tempt to explain the cause of such variation. This is attributed
by certain American zoologists, — of whom Cope is the chief rep-
resentative— to the direct action of the environment, for ex-
ample, the gradual preponderance assumed by the central digits
in the Ungulates would be explained by the greater strain
received by those reaching the ground. Strict Darwinists do
not consider such an explanation to be sufficient, because there
are many instances of protective resemblance and mimicry
where just as remarkable modifications of form are to be met
with, which could not be attributed to such a direct action of
the environment. On the other hand, we have met in the pre-
ceding chapters with so many instances of the adaptation of the
organism to its habits {vide Index, adaptation) that it seems
difficult to believe that such remarkable correspondence should
only be the result of selection from variations tending to occur
in every direction.

22. Not only have we to contemplate the effect of competition
between different individuals as favourable to change in organic
nature, but also the competition of different species. This is
^readily seen in a garden which, if left to itself, soon becomes
wergrown with weeds — those forms of plants which have either
tetter means of protecting or dispersing themselves, or are able
k) cope with less favourable conditions of life than the plants for-
merly cultivated. It is easy to see, that such competition, where
species come into contact for the first time, may lead to extinc-
tion of the form less able to protect itself; indeed the extinc-
tion of past forms of life is to be explained partly by such com-
petition, and partly by reason of some forms being specialised
to such a narrow range of conditions, that they have become

286 HIGH SCHOOL ZOOLOGY.

incapable of adapting themselves to any changes. On the other
hand, we may explain to ourselves the persistence of certain
types (VIII, 25), either by the little specialised character of their
requirements, or by their gaining superior means of protec-
tion, as for example, the adoption of a subterranean life, by
terrestrial animals, or their retirement to the recesses of deep
forests.

The competition of different species is interesting in another
aspect — the regulation of the balance of life- It is obvious that
the number of carnivorous animals is regulated by the number
of phytophagous forms on which they feed, and that these,
again, are dependent on their food-plants.

23. "While 7-eference is being made to species which live in
competition with each other, it must be recalled that many in-
stances of association for mutual advantage are to be found in
Nature. One of the most striking of these is afforded by some
Sea-anemonies, which fasten themselves over the abdominal
region of certain Paguridse. They serve in place of the shelter-
ing shells, which most of the genera select (VII., 12), and, in
addition, protect the crab by reason of their thread-cells ; in
return, they are furnished with locomotive facilities not usually
enjoyed by their relations. Other examples of such mutualism,
or symbiosis, are not uncommon.

24. Still more common, however, are the cases of partial or
complete parasitism, which are to be met with in all the sub-
kingdoms. (See index). The various grades of parasitism
offer such easy transitions from completely normal to much re-
duced organs, that we are tempted to seek an explanation for
these in the direct action of the environment. It is especially
the locomotive and digestive organs which exhibit such reduc-
tion, and the disuse of these seems to offer a rational explan-
ation of their condition.

25. In the course of disappearance of organs which are under-

HIGH SCHOOL ZOOLOGY. 287

going reduction, and before all trace of them disappears, they
are styled " rudimentary" organs ; such are the rudimentary
metapodials of the horse. Organs like these receive their only
satisfactory interpretation when we look at them in the light of
the doctrine of descent with modification.

26. The active relations between different species discussed
above, lead us to the consideration of the remarkable phenomena
of protective resemblance and mimicry (VII., 26, 33) — pheno-
mena which appear to be explainable only by natural selection.
The word mimicry conveys a striving after similarity, which is
entirely at variance with such an explanation, and the term is
now really taken to mean the preservation by Nature of
variations in the direction of resemblance to some other animal,
protected either by offensive or defensive weapons. Cases of
such protection are recorded above. A further illustration is
afforded by certain South American butterflies belonging to the
family Pieridse, which " mimic" those of another family, the
Heliconidse, protected from insectivorous birds by their offensive
odour and taste.

Protection may also be secured, however, by resemblance in
colour, or form, or both, to surrounding plants or inanimate
objects. The winter white coat of Arctic animals, the colours
of the nests and eggs of birds, the form of the leaf- and walking-
stick insects (VII, 23), are all to be explained in the same way.
Occasionally such likenesses are employed, not for defensive,
but for offensive purposes. One species of the predatory genus
Mantis (a member of a family allied to the Phasmidae) re-
sembles an orchid which is visited for its honey by bees, and a
species of spider has been observed, which, in the attitude in
which it waits for its prey, has the innocent appearance in
colour and form of a bird-dropping !

Colouration, in fact, is very generally protective in its func-
tion, and the transparency of most pelagic animals, the change-

288 HIGH SCHOOL ZOOLOGY.

able hues of the chamseleon and the tree-toad (which are ef-
fected reflexly through the nervous system), are to be explained
on the same principles. This does not exhaust its functions ;
it would appear with gregarious animals to be useful in recog-
nition of other individuals of the same species, also for warning,
as in the case of the brilliantly coloured coral-snakes (Flaps
IV., 21). That such warning colours are not unfavourable to
their possessors, might lead us to suppose that the rattlesnake's
rattle (IV., 22) is a similar warning to enemies not to interfere.

(7). Relation of Animals to Plants.

26. Some of the phenomena recounted above serve to recall
that plants are not destitute of defences provided by natural selec-
tion in relation to phytophagous animals. Such are the spines,
and the bitter, acrid and poisonous excretions, such as tannin,
which the best protected possess. It is only in comparatively
rare instances that plants can be said to assume the agressive,
and seize upon opportunities for securing food by absorption of
proteids from animals, instead of manufacturing them with the
aid of the nitrates of the soil. Such cases do occur in the
carnivorous plants, like the Venus' fly-trap (Dioncea), and the
more familiar pitcher-plants (Sarracenia) and sun-dew (Dros-
era). It must not be forgotten that there is a whole division
of the vegetable kingdom — the Fungi — which, being destitute
of chlorophyll, require to get their nourishment from previously
formed organic matter. They are either saprophytic or paras-
itic forms, the latter sometimes so actively aggressive, as to be
one of the most fruitful causes of disease and death, both in the
animal and vegetable kingdoms.

27. But there are also instances of plants and animals deriv-
ing mutual advantage from living together, which recall the cases
of symbiosis of animals. Such are afforded by the " yellow

HIGH SCHOOL ZOOLOGY, 289

cells n of the Radiolaria, which seem to prosper in their hosts
and to occasion them no inconvenience by their presence. Pos-
sibly they furnish oxygen to the tissues, and utilize themselves
the waste products, including carbonic acid, excreted by the
animal tissues.

28. The most obvious instances of the association of animals
and plants for mutual advantage are to be met with in the repro-
ductive phenomena of the vegetable kingdom, chiefly in those
connected with the fertilisation and distribution of flowering
plants. It is now known that by far the greater number of
Phanerogams with conspicuous flowers are fertilized by ins ct-
agency, and that the secretion of nectar, the colour and often
the form of the flower are so many inducements, acquired by
natural selection, to insects to visit them, while, on the other
hand, many peculiarities of form, or of the relative development
in time, of parts of the flower are so many obstacles to self-
fertilisation. So close is the relationship between flowering
plants and the insect- world that they may be said to have been
correlatively developed.

Similar mutual advantages exist in the relation of frugivor-
ous birds to fruit-bearing plants; the distribution of such
plants has been shown to be largely effected by the birds in
question, and the bright colours of fruits as well as their
sweetness receive a partial explanation in this way. Other
examples of the co-operation of animals in the distribution of
plants are furnished by those whose fruits (burrs), being clothed
with hooks or spines, adhere tenaciously to the coats of various
mammals, and thus secure a wider range.

29. Such considerations as those above emphasize the interde-
pendence of the vegetable and animal kingdoms, and the neces-
sity of studying the phenomena of both in connection with each
other. This is rendered more imperative when we come to
look at the economical aspects of Biology, and realize that the

290 HIGH SCHOOL ZOOLOGY.

diseases of cultivated plants and animals are frequently avert-
ible by a proper knowledge of the life-history of the organisms
in question. Many of these diseases are merely phases of the
struggle for existence, which occurs not only between individuals
of the same species but between species of the most different
character. Other diseases are due to unfavorable surrounding
conditions, which a due attention to physiology may make it
posssible to remedy. Such disturbances of the normal or
healthy processes of life form the subject-matter of Vegetable
and Animal Pathology.

For further information on these as well as on the other
topics discussed in this chapter, the student must, however,
consult books which deal with them specially. The object 01
the present chapter has chiefly been to show the relations of
facts scattered throughout the preceding chapters, and to indi-
cate as far as possible the general principles which have been
reached by zoologists.

INDEX.

Page

Abomasum 176

Acanthia 214

Acanthocephali 224

Acanthopteri 62

Acarina 204

Acephala 228

Acetabulum 85

Achtheres 200

Adnata 259

Acipenser 73

Acrania 79 274

Acrydidce 209

Actinia 247

Actinozoa 245

Actinophrys 254

Adam's Apple 159

Adaptation of feet of Uugulata

for locomotion . . 167-8, 174
of Ruminants for rapid

locomotion 175

of sloths to arboreal life. 163
of Marsupialia to differ-
ent modes of life 162

of Mammals to aquatic

life . 164, 180

of Mammals to aerial life 185
of Mammals to subter-
ranean life 182

of bird's skeleton and

muscles to flight 127-8

of bird's feet to different

methods of locomotion 134-5
of Amphibia to burrow-
ing 98

of Lacertilia to different

modes of life 107, 110

of insects to aquatic life 213
of Chelonia to aquatic and
terrestrial life . . . 104

Page
Adaptation of Hyla and frog

to arboreal life. .... 96, 97
of fossil reptiles to differ-
ent modes of life. .117, 120

jEgialitis 139

JSlurichthys 56

JEpyornis 134

Agama 107

Agalena 202

Aglossa 94

Agouti 184

Air-bladder of cyprinoids .... 58

Function of 43

Connection with auditory

labyrinth 38

Vessels of in Physoclysti. 63

Coats of 42

Of Ganoids 72

In Acanthopteri 63

In Dipnoi 78

Air-bladder and duct of cat-
fish 130, 42

Air-sacs of birds — of locust . . 209

Aix 139

Albatross 138

Alces . . 178

Alewife 60

Alligator garpike 75

Alligator 115

Alisphenoid 23

Alpaca 177

Altrices 131

Alternation of teeth in mam-
mals 155

Alula 122

Alveolar part of maxillaries

mammals 149

Alveoli of lung in mammals . . 158
Ambloplites , ; 64

292

INDEX.

Page

Amblyopsis 62

Amblystoma 90-1

Ametabola 214

Amia 74

Amiurns, species of 51-3

Auricle of catfish 45

Amoeboid cells .... 14

Amoeboid blood-cells 44

Amoeba 253

Amphibia 80

Amphicoelous ....81, 18, 116, 106

Amphidiscs of sponges 251

Amphioxus 79

Amphipnous 62

Amphipoda 197

Amphisboena 110

Amphiuma 89

Ampullse of auditory labyrinth 38

Amyda 104

Anacanthini 70

Anaconda , Ill

Anadromous 59

Anas 135-9

Anastomus 1 36

Anatomy 264

Anchovy 61

A ncistrodom 114

Ancylus 234

Anguilla 62

Anguis t 110

Anisonema 257 -8

Annelida 218

Anodon 229

Anseres 138

Anteaters 163

Antelopes 178

Antennae 194

Antennulae, crayfish 194

Anterior extremity of Meno-

branch compared with fish 85

Anthropomorpha 189

Ant'docapra . . . 178

Antilope 179

Antimeres 242

Antlers 178

Ant-lions 214

Ants 217

Anura 88,92

Aorta dorsal 46

Aortic arches of catfish. •-.•«•« 46

Page

Aortic arches of mammals ... 159

Apertures of body in catfish.. 11

Aphis 213

Apis 217

Appendages abdominal of in-
sects 207

Appendages of crayfish 193

Appendicular 11

Apieryx 134

Aptenodytes 137

Aptera 213

Apus 199

Aquatic animals, distribution

of 281

Arachnida 191, 201-4

Araneina 202

Arbor vitae 152

Arcella 254

Archmopteryx 123, 132

Archaean Rocks 270

Arius 56

Arctopithecini 189

Arctomys 184

Ardeida 139

Argali 179

Argulus 200

Argus 140

Arms of Brachiopod 238

Arm of starfish 243

Armadillo 163

Aromochelys 105

Artemia 199

Arterial cone 72, 87

Arteries of catfish 44

Artiodactyla 174

Articular processes 19

Arthropoda 190- 217

Arthrogastra 202

Articular element of man-
dible 24

Arvicola „ 184

Arytaenoid 159

Asaphus 201

Ascaris 224

Asellus 198

A sinus 173

Asiphoniala 232

Aspects of body in Vertebrates

and Invertebrates 190

<>.... 104

INDEX.

293

Page

Aspredo 57

Abacus 192

A wteriaa 243

Asymmetry of gastropod 233

Of oyster 228

Alalapha 186

Atavism . . . '. 172

Atax 204

Ateles 189

Atlanta, 235

Atlantosaurus 117

Atlas 126

Atrium 45

Auchenia, 177

Auk 138

Auditorycapsule 36

Aurelia 247

Australian region 161

Aves precoces and altrices ... 131

Avocet 136-9

Axial 11

Axis cylinder 16

Axis vertebra 126

Axolotl 91

Aye-aye 187

Aythya 139

Babyrusa 175

Baboon 189

Bactrian Camel 177

Badger 179

Bagrus 56

Balmna 166

Balceniceps 136

Balancers 215

Balanoglossus 243

Balanus 200

Batistes 71

Barbels 12

Bark- Beetle 215

Bass-Tribe 64- 67

Basibranchial 26

Basioccipital 23

Bascanium 114

Basommatophora 234

Basalia of Fin 28

Bathymetrical Distribution . . 281

Batrachia 80

Bear- Animalcule 204

Beaver 184

Page

Bed-Bug 214

Beetles 215

Bee 217

Beetworm 224

Bell- Animalcule . . . : 260

Belostoma 213

Beluga 165

Belemnites 237

Bighorn 179

Bilateral Symmetry 10

Connection of, with Form-
ation of Locomotor Sur-
face 243,259-60

Biology 262, 264

Birds 121

Birgus 197

Bison 179

Blatta 209

Blackfly 216

Blarina 182

Blackbird 141

Blastoderm 131

Beadsnake 113

Bladder-Worm 227

Blind-Fishes 62

Blind-Snake Ill

Blind- Worm 110

Blood-Cells 44

Blood-Supply of Gills 46

Blood-Temperature 161

Blubber 144

Bluebird 141

Boa-constructor Ill

Boatbill 136

Bojanus, organ of 231

Boleosoma 66

Bombyx 216

Bonasa 140

Bony-pike 74

Bone, structure of 15

Book-scorpion 202

Bostrychus 215

Botaurus 139

Bovina 179

Bowfin 74

Brachiopoda 237

Brachyurus 188

Brachyura 197

Branchial Arches of Catfish . . 26
ofCat 149

iU

INDEX.

Page
Branchial arches of Frog .... 93

of Menobranch 83

Brain 31, 86, 103, 129, 152

Branchial Arteries, Afferent

and Efferent 46 87

Branchial Chamber and Aper-
ture 12

Branchiostegal Membrane and

Bays 25, 42

Branta 139

Branchipus 199

Branchiate Arthropods 205

Brady pus 164

Branchiobdella 222

Breeding-colours of cyprinoids 58

Brine-shrimps 199

Brontoiherium 172

Brontosaurus 117

Brood-pouch in lamelli-

branchs 231

In Polyzoa 241

Brula 163

Bryozoa 239

Bubo 140

Bubalus 179

Buffalo 179

Bufo 92-6

Bunodont 176

Burrowing Lamellibranchs . . 232

Bursa Fabricii 130

Burbot 70

Brittle-star 244

Butterfly 216

Byssus 232

Caddis flies 214

Caducibranchiata 90, 88

Calcarea 250

Calotragus 174

Caloptenus 206

Callorhinus 180

Callichthys 57

Callosities of horse 173

Cambarus 191

Campodea 210

Camelus 177

■CameloparddUs 178

Cancroma 136

Cannon-bones 169, 177

Canis 179

Page
Canine teeth 155

as compensating for ab-
sence of tusks 177

Capra 179

Capelin 60

Capillaries 44

Capybara 184

Carp 58

Carmine 213

Cartilage in Cephalopoda 236

Cartilage, structure of 14

Carotid arteries of cat-fish .... 46
Cardinal veins " .... 46

Carpus of Menobranch 85

Carotids of " 87

Carcharodon 77

Cardo - 206

Caribou 178

Carpocapsa 216

Carabus 215

Cariacus '. . 178

Carp-suckers 58

Carnivora 144, 179

Carapace of turtle 102

Carpophaga 140

Carinatai 124, 137

Care of young in Vertebrates. 142
Catfish, specific name of.... 51

Catodon 165

Catarhini 189

Cathartes 141

Catostomus 57

Cassowary 134

Casuarius 134

Castor 183

Cavkornia 178

Cavia 184

Cebus 189

Cecidomyia 216

Cells 16

Cell-animal, structure of ... . 14

Cell, Polyzoa 239

Cephalopoda 235

Cephalophora 228, 232

Cephalothorax 193

Cepphus 137

Cmtetes 183

Centipedes 211

Centrum of vertebra 18

Centrarchus 64

INDEX.

295

Ceratohyal of catfish 26

Central canal of spinal cord . . 32

Ceratium 257-8

Ceratobranchials 26

Cerebral hemispheres of cat-
fish 30

Cerebellum of catfish 30

Cercaria 226

Cervical region of vertebral

column in mammals 146

Cerebellum of mammals .... 152

Cerebrum of mammals 151

Cercojnthecus 189

Ceralodus 78

Cervidce 178

Cercoleptes 179

Cervus 178

Cerci 207

Cere 140

Cestodes 225

Cetacea 164

Chcttogaster 221

Chcetopoda 222

Channel cat 54

Chawodeon 108

Charadrius 139

Characteristics of birds 121

Chamois 179

Cheek-pouches monkeys .... 189

rodents 184

Cheese-mite 204

Chelse 194

Chelate 194

Chelicerae 202

Chelifer 202

Chelonia 100

Chelopus 105

Chelydra 100

Chemical composition of liv-
ing bodies 263

Chinch-bug 214

Chimcera 76

Chilognatha 211

Chilopoda 211

Chinchilla 184

Chilomycterus 72

Chiroptera 185

Chimpanzee 189

Chitin 191

Chiasma of optic nerves 152

Pajfe

Chiromys 187

Chirotes 109

Chipmunk 184

Chiton 232, 234

Chondrostei 73

Choroid 35

Cholcepus 164

Chrysothrix 189

Chrysalis 209

Chrysemys 105

Chrysomelidm 215

Ciconia 135, J 39

Cicadella 213

Cicada 213

Ciliary muscle 35

Ciliate Infusoria 253

Ciliated chambers 250

Ciliophrys 251

Circulatory organs 265

Cirripedia 200

Cinosternum 103

Circulation of crayfish 197

Circumvallate papillaa 157

Circulation of earthworm 221

of cat 179

Cistudo 105

Ciscoe 59

Clarias 57

Clavate cells 17

Classification. .9, basis of . . . . 261

Clamatores 149

Cladocera 199

Clam 232

Clathrulina 254

Clepsine 222

Climatic aspect of Biology . . 273

Cliona 252

Clitellum . 221

Clothes-moth 216

Cloacal Siphon 231

Clupea 60

Clypeus 205

Cobra {Naja) 113

Coccinella 215

Coccoon earthworm 221

Coccus 213

Coccyges 141

Cochineal insect 213

Cochlea 37

Cochlea, scahe of 154

296

INDEX.

Page

Cocoa-nut Crab, . . . 197

Cockroach 209

Cocoon 214

Coddling-moth 216

Codfish 70

Coeca, intestinal of birds 129

Ccelenterata 245

Cadogenys 184

Ccelom of Vermes 219

Ccelom 11

of mammals 158

Ccenoecium 240

Coenosarc 247

Coffin-bone 172

Coleoptera 214

Collar-cells of Sponge 250

Colobus 189

Colonies Polyzoa 239

Colouration, functions of .... 278

Coluber 112

Columbce 140

Columba 136

Columella auris 94, 83

Columella of cochlea 154

Compsognathus 118

Compound eye 195

Comparison of earthworm and

crayfish 219

Concrescence of cranial bones

in mammals 148

Connective tissue 13, 14

Contractile vacuole 253, 259

Corium 12

Conus arteriosus 72

Conus 235

Condor 136

Condylura 182

Coney 171

Condyles occipital 126

Coot 139

Copper-head 114

Copepoda 199

Cope 285

Coracoids of Monotremes .... 161

mammals 150

catfish 27

Corallum 247

Coral 247

Corallium 248

Coregonus 59

Coreus ; 214

Cormorant 138

Cornea 34

Coronary 172

Corpora quadrigemina 152

Corpus callosum 152

Correlation, principle of 273

Coryphodon 170

Coverts 122

Cowrie 235

Coxal glands 220

Coxa 206

Crayfish 191

Cranium 20

Cranial nerves 33

Cranium, proportion to face . . 148

Cranial bones origin of 20

Creepers 141

Cricket 210

Cricoid 159

Crinoidea 244

Crlstatella 239

Crystalline cone of arthropod

eye 196

Crow 141

Crocodllia 115

Crotalus 113

Crura cerebri 151

Crustacea 191, 200

Cryptogamic 9

Crystalline stylet , . . 230

Cuckoo . . 141

Culex 216

Culmen 122

Curlew 139

Cursorial birds 132

Curculio 215

Cutaneous muscular tube, Ver-
mes 220

Cutaneous sense-organs of fish, 1 7

Cuttle-fish . . 235

Cutaneous secretion, Bufo ... 93

Ctenoid 12

Ctenophora 245

Cyclops 200

Cyclostomi 78

Cyclophus 114

Cyclopterus 69

Cyclas 232

Cygnidai 139

INDEX.

297

Page

Cynips 217

Cynomys : 184

Cynomorpha 189

Cyprinus 57

Cypr'is (Candona) 199

Cyprcea 235

Cysticercus 226

Cypselus 135

Cydophora 181

Cystic stage of Oestodes 226

Cytology 264

Daphnia 199

Daddy-long-legs 202

Dafila 139

Darter 66

Darwin on earth-worm 221

Darwinism 2S5

Dasyprocta 184

Dasypus 163

Dasyurus 1 62

Deer s. 178

pigmy 178

Defensive habits of Heteroilon 114

Demodex 204

Dentition Mammals 155

Insectivora 182

Rodents 183

Seals 180

Primates 1S8

Camel 177

Ruminants 176

Horse 173

Bats 186

Fossil Artiodactyla 176

Bear 156

Edentata 163

Dental formula, typical 156

Dentary 25

Dentine 18

Dew-claws 176

Dermaleichus 204

Dermaiocheiys 105

Dermestes 215

Descent with modification . . . 269
Desiccation, resistance to ... . 204

in Rotifers 223

Desmodus 186

Development, locust 209

Brachiopoda 237

20

Pasre

Development Toad 96

Dexiotropous 233

Diadophhis 114

Diastema 1 55

Diapheromera 210

Diaphragm 1 5S

Dicotyles 175

Diemyctylus 91

Didelphys 161

Didus 140

Dibranchiata 236

Dittuyia 254

Dipkyodont 155

Dipnoi 78

Dipiera 215

Dipus 184

Dinobryon 257

Dinosauria 118

Dinornis 133-4

Dinolherium 170

Dimorphism 223

Diodon 71

Diomedea 1 38

Dioncea 2S8

Discophora 220

Distomum 226

Disuse of organs, effects of. . 286

Docimastes 1 36

Dodo 140

Doris 235

Doree 66

Doras 56

Dorosoma 60

Dorypliora 215

Draco 108

Dragon-flies 212

Dromams 134

Dromedary 1 77

Drosera 288

Duck-mole ... . 160

Dynastes 215

Dytiscidce 215

Ear of cattish 36

crayfish 196

locust 208

Ophidia 113

mammal 153

Earthworm 219

Earwig , 209

EcarduitA 239

298

INDEX.

Page

Echeneis „ •«••*.«.. 67

Echinodermata 242

Echinarachnius 243

Echinus 242

Echidna 160

Ectoderm of Hydra 246

Ectoparasitic Trematoda .... 225

Protozoa .256, 260

Ectopistes 140

Edentata ] 63

Eel 62

Effects of external form on in-
terna] organs, Ophidia .... Ill

Eft........ 91

Eggs, Amphiuma 98

Brachiopoda 238

of Catfish.. 48

of crayfish 196

Crocodiles 116

Birds 131

Hydrozoa 246

Lamellibranchs 23 1

Menobranch 87

Monotremes 143

Ophidia 113

Pipa 94

Sharks 78

Turtle 104

Siphonops 98

Elaps . ... 113

Elasmobranchii 76

Electric Catfish 56

Eel 62

Ray 77

Elephant 168

Elevation of land, effect of ... 279

Elytra 207

Embryology 264

Emu 134

Emys 105

Enamel 18

Encephalon 31

Encystment of Protozoa 253

Trematoda 226

Cestodes 227

Endochrome in Euglena 257

Endoderm of Hydra 246

Endolymph 37

Enhydra 179

Endoparasitic Trematodes.. . . 225

Endoplasm 253

Endopodite . .". 193

Endoskeleton, Cephalopoda... 236

of Brachiopod arms 238

Endoskeleton of Vertebrates. 17

Entoderm 246

Entomostraca 198, 200

Eider 139

Environment, direct action of 285

Ephemeridce 212

Ephydatia 251

Epiblast 49

Epibranchials 26

Epicranium 206

Epidermis 17

Epidermis, Sauropsida 101

Epiglottis 157

Epihyal 25

Epimerum 206

Epiotic 22

Epipharynx 207

Epiphysis of Catfish 31

Epipubic bone 161

Episternum, Monotremes. ... 161

Epipodite 193

Epistome 240

Epithelium 13, 14

intestinal 40

Episternum, amphibians ... 93

Equus 173

Eretmochelys 105

Ergasilus .' 200

Erinaceus 183

Ermine 179

Erismatura 139

llsox 61

Estheria 199

Etheostoma 66

Ethmoid of Mammals 148

Erethizon 183

Engraulus 61

Euglena 257

Euglypha 254

Eumeces 107

Eumetopias 180

Euplectella .• . . 251

Euspongia 252

Eustachian Tubes 93, 154

Eutamia 114

Eutheria 143

INDEX.

299

Page

Evolution of Organic Nature. 270

Excretory Organs 265

of Vertebrates 47

of Insects 203

of Arthropods 203

of Vermes 219

of Mollusca 228

of Polyzoa 241

of Protozoa 253

Exhalent Siphon 231

Exocmtus 63

Exoccipital 23

Exopodite 193

Exoskeleton 17

of Turtles 101

Crocodiles 115

Edentata 163

Echinodermata 242

Eye, Vertebrate 34, 35

Compound 195

Falco 135

Fan-coral 248

Fauna of Madagascar 186

Fauces of Mammals 157

Feathers 121, 122

Felis 144, 179

Femur 85, 206

Fenestella 241

Fenestra Ovalis 83, 153

Rotunda 154

Fetter-bone 172

Fiber 184

Filaria 224

File-fish 71

Filiform papillae 157

Fins 11

Unpaired 81

of Cetacea 165

Rays 27 28

Pteropod 235

Finches 141

Fire-flies 215

Fistularia 63

Fission in Protozoa 26!)

Flagellate Infusoria 253

Flamingo 136, 189

Flat-fish 70

Flea 216

Flounder 70

Pasre

Flipper, seal 180

Aquatic Mammals 165

Sirenia 166

Turtles 104

Ichthyosauria 117

Penguin 137

Fluke-worm 226

Flying-squirrel 184

Flying-fish 63, 69

Flycatchers 141

Follicles hair 144

Feathers 121

Setigerous 221

Fontanelles 21

Food-yolk ....49, 131

Foot in Mollusca 228

Heteropoda 235

Foramen magnum 20

Foraminfera 254

Formulae of teeth 156

Forficula 209

Formica 217

Formative yolk 49

Fossils 269

Fratercula 137

Fresh water Faunas, origin of. 282

Frigate-bird 138

Fruit-bats 186

Frontal plane 10

Frog 97

Fulica 35

Fungi . 288

Fur-seals 180

Fur 179

Funnel 235

Fungiform 157

Function 265

Change of 197

Ga.leopithecus . . 185

Galea 206

Galago 187

Galls 216, 213

Gallinacei 139

Gadus 69

Galtinago 139

Gallinule 139

Gallflies 217

Galleyworms 211

Gallus 124

300

INDEX.

Page

Gall-bladder of catfish 41

Gamm,arus 198

Gannets 138

Garfish, Scomberesox 74

Ganoidei 72

Ganglion-cells 32

Ganglia 32

Garpike 72

Garter-snake 114

Gastric glands 40

Gasterosteus 63, 64

Gastropoda 232

Gastrovascular Cavity of

Sponges 250

Gastrovascular Cavity of Ccel-

enterates 245

Gavial 115

Gazelle 179

Gecko 108

Gemmules of Sponge 25 1

Gephyrea 222

Geocores 213

Geographical Distribution,
Past and Present, of Lemurs 187

of Elephants 170

of Camels 177

Geological Importance of

Radiolaria 255

of Foraminifera 254

Record, incompleteness of 272

Genus 54

Genealogical Trees 272

Germinal Epithelium 14

Gerris 214

Germinal Yolk 131

Geomys 183

Gibbon 189

Gill-Rakers 73, 43

Gill-Slits 12

Gill-Slits of Menobranch . . 80, 81

Gill-Filaments 43

Gill- Arches, Membranous Par-
titions 76

Gill- Pouches 76

Gills, Urodela 89

Gills, External of Menobranch 80

of Tadpole. 95

Gills, of Cephalopoda 236

of Crayfish 193

Lamellibranchs 231

Gills, Mollusca 228

Giraffe 178

Gizzard of Fowl 129

Gizzard-Shad 60

Glacial Period 278

Glandular Epithelium 14

Glass-Snake 110

Glenoid Cavity 85

Glenoid Fossa of Mammal's

Skull 149

Globigerina 254

Glochidia 231

Glottis of Menobranch 86

Goat 179

Goat-Sucker. . 141

Gold-Fish 57

Goniobasis 234

Gonys 122

Gordius 224

Gopher 184

Gorilla 189

Goura 140

Grampus 165

Grasshopper 205

Grebe 138

Green-gland of crayfish. .... 219

Gregarina 254

Grouse 140

GriM 139

Gulo 179

Guinea fowl 140

Pig 184

Gull 138

Gymnophiona 88, 98

Gymnolcemata 240

Gymnotus 62

Gypogeranus 140

Haddock 70

Heemal arch 19

Haemoglobin 44

Hair 144

Helicina 235

Heliconidce 287

Helix 234

Hellbender 89

Hemiptera 211

Hepatic cells 41

Portal Circulation in

Mammals 160

INDEX.

301

Page

Heredity 283

Herpestcs, 179

Herodiones 139

Hermit-crab 1 96

Heterocercal 19, 73

Herring 60

Hesperornis 123

Hessian-fly 216

Hawkmoth 216

Heteronoinous 193

Helerodon 114

Half-gill (demibranch) 72

Halibut 70

Halteres 215

Halisarca 251

Halicore 1 67

Hapale 189

Haplocerus 179

Harp seal 181, 283

Hatteria 100, 106

Hag-fish (Mi/xhie) 79

Head, Molhisca 228

Heart mammals 158

of Catfish 44, 45

of Menobranch 87

of Turtle 104

of Crocodile 116

Hedge-hog 183

Heliosphcera 255

Heliozoa 255

Heteropoda 235

Heteroptera 213

Heteroecism 224

Heterodera 224

Hippocampus 63, 65

Hippopotamus 174

Hinge in Lamellibranchs 228

in Brachiopods 239

Hirudo 232

Hippospongia 252

Histology 16, 264

Holotricha 259

Holostei 73

Holothuroidea 243

Homonomy 210, 218

Homarus 192

Homologous 10

Hy-itrix 183

Homocercal 19

Hoopoo 141

Page

Honeycomb-stomach 176

Horizontal plane 10

Horse-flies 216

Horns 178

Horse 173

Homoptera 213

1 (orned-toad 107

Huanaco or Guanaco 177

Humerus 85, 1 50

Hycemoschu8 174

Hyama 236

Hyalonema 251

Hybernation 184, 186

Hydrochoerus 1S4

Hyoid of Mammals 149

Hydra 215

Hydrackna 204

Hydathia 223

Hydrozoa 245

Hydrorhiza 246

Hydrophis 113

Hydrocores 213

Hi/Johates 189

Hyla V6

Hymenoptera 216

Hyomandibular 24

Hyodon 66

Hypobranchials 26

Hypophysis 30, 152

Hypohyal 25

Hypoblast 49

Hypopharynx 217

Hypodermis 195, 219

Hypofrirha 260

Hyracoidta 170

Ibex 179

Ibis 139

Ichthyornis 124, 135

Ichthyobdeha 222

Ichthyopteryyia 117

Ichthyosaurus 117

lehtJtyop.sida 99

Icktluelurus 54

Ichneumon (Mammalia) 179

(Insecta) 217

Iguana 107

Iguanodon 118

Ileo-ccecal valve 39

Ictalurus 54

302

INDEX,

Imparidigitate Ungulates .... 171

Imago 209

Incisive foramen 149, 153

Incisors 155

Incus 153

Inhalent siphon 231

Inferior lobes of brain 30

Ink-bag 236

Infusoria 252, 256

Ciliata 258

Infusorial earth. 255

Incubation of eggs 131, 132

Insecta 191

Insectivora 182

Instinct 267

Intestine of leech 222

of Crayfish 196

of Earthworm 219

of Catfish 40

of Menobranch 103

Indri 188

Interhyal 25

Intercellular substance 14

Interoperculum 25

Interparietal 148

Invertebrata term 9

Iris 35

Interspinal 28

Isopoda 107

Ixodes 204

Jseger 138

Jacobson, organ of, in cat. . . . 153

Jaws, catfish 24

Turtle 101

Ophidia 112

Leech 222

Jay 141

Jerboa 183, 184

Jugal arch 148

Jugular fins 62

Jugular vein 159

Kainozoic 270

Kangaroo 143

Kidney of catfish 47

of menobranch 87

head- 47

Kingfisher 141

Kinkajou 179

Page

Kiwi 184

Knee of elephant and other

Ungulates 169

Labellre 216

Labrum, crayfish 196

Insects 205

Labium 206

Labrynth of ear in catfish 36

Labyrinthodontia 97

Lachnosterna 215

Lacinia 206

Lacertilia 106

Lady-bird 215

Lagopus 140

Lake-mullet 58

LameUibranchiata 228

Lamellirostres 139

Lake-herring 59

Lampyridce 215

Lamprey 78

Land-locked seals 187

salmon 59

Lancelet 78

Larvae Echinodermata 243

higher Medusse 247

provisions for in Hymen-

optera 217

Larks 141

Larus 138

Larynx in animals 159

Lateral line, catfish 12

Menobranch 81

Leech 220

Leiotropous 233

Lemming 184

Lemuroidea 187

Lemur 187

Lens 35

Leopard 179

Lepomis 64

Lepidosiren 78

Lepidoptera 215

Lepidosteus 74

Lepas 183

Leptoptilus 136

Libellula 212

Lichanotus 188

Life, characteristics of 263

Ligament in Lamellibranchs . . 228

INDEX.

303

Page

Limax „ . , 234

Limbs of higher Vertebrates. . 81

Limicolce 139

Limicolous worms 220

Limncea 233

Limbs, development of, in

tadpole 95

Limulus, relation of, to Arach-

nida 201 202

Limpet 234

Linens 225

Lingula 239

Lips and tongue of mammals. 157

Lion 179

Littoral zone 281

Liver-fluke 226

Liver of catfish 41

Lizards 107

flying 108

Lobster 192

Locomotion in Cephalopoda . . 236

Ophidia . Ill

Log-perch 6Q

Llama 177

Loligo 235

Longipennes 138

Loon 138

Lophobranchii 63

Lophophore (circlet of tent-
acles in Polyzoa) 240

Lore 122

Lori 187

Loricaria 57

Lota 70

Lungs of memobranch com-
pared with air-bladder. 86

Turtle 103

Ophidia Ill

Mammals 158

Scorpion 202

Spider 203

Lutra 179

Lymphatic system 47

Lynx 179

Macacus 1 89

Mackerel 67

Macrochires 141

Macrolepidoptera 216

Macrura 197

Page

Macroscelides 183

Macrobdella 222

Magpie 141

Malacostraca 191-8

M alapterurus 56

Mallard 139

Malleus mammalia 149, 153

catfish 22, 38

~M.allophaga 213

Mallotus 60

Malphigian tubes 203-8

Mammals 142

Manubrium sterni 147

Mammoth 168

Cave 62

Manatee 166

Mandibles — crayfish 194

Mandible — catfish 25

Manis 163

Mantis 283

Mantle of Mollusca 228

Gastropods 233

Manus of various mammalia. . 164

Manyplies 176

Marabu 136

Marine-worms 220

Mark in horse's incisors 173

Marsupialia 143, 161

Marten 179

Masseter 148

Mastigophora 252, 256

Mastodon 169

Maxillae, crayfish 194

Maxillipedes 193

Maxilla of catfish 25

Maybeetle 215

Mayflies 212

Meckel's cartilage . . 25, 149, 153

Mediastinum 158

Medulla oblongata 30

Medusa-form 246

Medicinal leech 222

Megatherium 164

Megapodidm 140

Megalosaurus 119

Meleagris 139

Mentum 206

Menobranch 80

Menopoma 89

Mephitis . . . 179

304

INDEX.

Page

Mermis *224

Merganser 136, 139

Mesosiomurn 225

Mesenteries of Actinia 248

Mesoblast 49

Mesozoic 270

Mesethmoid 22

Mesentery 40

Mesology 277

.M esoderm of Hydrozoa 247

Metabola 264

\! etastoma 196

M etapodials, rudimentary of

horse 172

conversion of into cannon

bones 169

Metatheria 143, 161

Metazoa 25?

Metamorphosis of Crustacea. . 197

of Anura 91, 94

ofUrodela 90

Metameres 20

Metapterygoid 25

Metacarpus, menobranch 85

Michelinea 249

Microplerus 64

Micronucleus of Infusoria. . . . 259

Microlepidoptera 216

Milk -glands of mammals 142

Milk-dentition 155

Mimicry 216, 287

Millipedes 211

Minnow 67

Mink 179

Moa 133, 134

Molar teeth 155

Mole 182

Mollusca 227

Molluscoidea 237

Monads 257

Monodon 165

Monas 257

Monotremata 143, 160

Monophyodont 155

Moon-eye 61

Moose 178

Mosquitos 216

Monkeys 188

Moschus 178

Page

Motmot 141

Mould, formation of by earth-
worms 221

Mouth- vacuole of Flagellata.. 257
Mouth of Ciliated Infusoria. . 259
Mouth-parts of Diptera . .212, 215

of Insecta 206

of M^riapods 211

Moult of locust 209

Mouse 184

Mouth-cavity, sub-divisions of

in Mammals 157

Moloch 108

Moxostoma 58

Mucous membrane 38

Mud-puppy 80

Mudfish 74

Mur'uke, Mus 1 83

Musca 216

Muscle-tissue 13-16

Muscles 28-29

Mussels 228

Muskallunge 61

Musk-ox 179

Musk-rat 184

Mustela 179

Mustelus 77

Mya 232

Mycetes 1 89

Myctema 1 36

Myodes 184

Myogale .' 182

Myriapoda 191, 210

Myomeres 29

Myotomes 50

Myrmeleon 214

Myrmecophaga 163

Mysis 192, 198

Mytilus 232

Myxine 79

Myxosporidium 254

Nacre 229

Naja 113- 114

Nanemys 105

Natural Selection 279- 281

Nauplius-phase 197

Nais 221

Nautilus ' . . 236

Narwhal 165

INDEX.

305

Page

Nasal Cartilages 153

Nasal septum mammals 153

Nasal cavities of Dipnoi .... 78

Necturiis 80

Negative characters in classi-
fication 9

Nephelis 222

Nephridia of earthworm .... 219

mollusca 228, 231

homologues of, in

Arthropods 220

Brachiopods 238

Nervous system of crayfish . . 195

spider 203

insects 207

Lamellibranchs 229

Central, of Vertebrates . . 30

Nests of fishes 63

birds 287

Nematelminthes 223

Nematodes 224

Nematognathi 56

Nemertini 225

Neuroptera 212- 214

Neuro-epithelium, auditory . . 38

Neural arch 18

Nerves afferent and efferent30, 32

function of 32

Nerve-cells 32

Nettling-organs 245

New World Monkeys 188

Newt 91

Noctiluca, 207, 208

Nomenclature 51, 55

Notochord, 18

Notonecta 213

Notum 206

Noturus 55

Nucleus of cells 16

Infusoria 259

Numenius 139

Numida 140

Nummulitic Limestone 279

Nutritive organs 265

Nuthatch 141

Nyctale 140

Nycticorax 139

Nyctipithecus 189

Obelarku 246

Ocean Currents, Effects of .. . 282

Pacre

Ocellus 203, 205, 207

Occipital Condyles 126

Octopus 2 f)

Odontoid Process 1 26

Odd-Toed Ungulates 171

Oligochaeta 220

Oliva 235

Olfactory Organs, Lamelli-
branchs 230

Olfactory Bulbs and Tracts of

Catfish 30

Olfactory Organ 34

Mammals 152

Crayfish . . 165

Ommatidium 195

Onychodromus 259

Onchorhynchus 59

Oniscus 198

Ontogeny 264

Opalina 259

Operculum 25

Of Gastropods 234

Opisthoccelous 75

0 phiosaurus 110

Ophidia Ill

Ophiothrix 244

Ophiuroidea 243

Opisthobranchiata 235

Opposable Digits of Primates. 186

Opossum-Shrimps 197

Opossum 161

Optic Lobes 31, 152

Ophibolus 114

Orang-utan 189

Orbitosphenoid 23

Orcynus 67

Orca 165

Organization 253

Oriental Region 287

Oriole. . . 141

Ornithopoda 118

Ornithorhynchus 167

Ornithological Terms 122

Otoliths 37, 196

Orthoptera 209

Genuina 211

Orycteropus 163

Otter 179

Oscines 141

Osculum of Sponge 250

306

INDEX.

Page

Organ 266

Organism 265

Organisation 265

Osmerus 60

Ostracion 71

Ostracoda 199

Ostrea 232

Ostrich 134

Otarice 180

Otocysts 230

Ovibos 179

Oviparous mammals 143

Oviposition locust 209

turtles 104

Ovipositor 207, 217

Ovis 179

Ounce 179

Owl 140

Oyster 232

Paca 184

Pachyderm 144

Paqurus 197

Paddle-fish 73

Palate 157

Palaeontology 269

Palaeozoic 270

Palcemonetes 197

Palceochcerus 176

Palceotherhim 171

Palp 194, 206

Palpifer 205, 217

Paludicolce 139

Palatine 25

Pallium 223

Paludicella 240

Paludina 234, 235

Palps or tentacles, Lamelli-

branchs 231

Panorpa 214

Papillae of tongue 157

Skin 13

PapiHo 216

Pancreas 51, 52

Paraglossae 217

Parapodia 220

Parasitism in Infusoria 259

Grade of 286

Effects on organs 223

In annelids 221

Page

Parasitism in Leeches 222

Fish 78

Parasitic Protozoa 256

lsopods 198

Copepods 199

Mites 205

Ichneumons 217

Larval Diptera 213, 216

Patella 234

Parethmoid 22

Parasphenoid 23

Parotid 154-7

Parotoid 93

Passeres . . 141

Parrot 141

Parallel groups of Rodents

and Insectivora 183

Patagium 184, 186, 162

Paunch 176

Pavo 140

Peafowl 140

Pearls 229

Pearly Nautilus 236

Pectoral girdle mammals 150

Pecten 232

Pectinatella 241

Peduncle of Brachiopods .... 238

Pelecanus 136

Pelican 136

Pelagic animals 245, 235, 281

Pelvic arch 28, 93

Pen of squid 235

Perca 65

Penguin 137

Peccary 175

Pedipalpi 202

Pediculus 213

Pentaceros 244

Pentacrinus 245

Pentacta 243

Pentastomum 204

Percina 66

Perennibranchiata 88

Pericardium 45, 158

Periostracum 229

Periotic 148

Peripatus 218, 211

Perisarc 246

Perissodactyla 171

Peritoneum 40

INDB~.

807

Page

Peritricha 260

Perla . . . 212

Persistetit types 239

Petrel 138

Petromyzon 79

Pezophaps 140

PMtthon 138

Phacochoirus 175

Phalacrocorax 138

Phalanges 85, 185

Phalanijina 202

Phalangers . 62

Phalangista 162

Phanerogamic 9

Pharyngeal teeth 26

Pharyngobranchials 26

Pharynx 157

Pkascolomys 162

Phmianns 124, 135

Phasma 210

Ph&acodus 170

Pin,'-, ma 146, 165

Phoca 181

Pholas 232

PhcznicoptertiA 136, 139

Phosphorence of sea 258

Phryganea 2) 4

Phytophthires r>>

Phylbpoda ' .6

Ph i/lloxera 43

Pkyllium 210

Phylactolcemata 240

Phyllostonia 185

Phylogeny 272

Physiology . . . ". 264

Pkysoxtomi 58

Physoctvsti 62, 58

Phn/ it o.<*, „ta 107

Phytoptus 204

Physa 234

Pici 135

Pickerel 66

Pietidai 287

Pike-perch 66

Pike 61

Pigeon 140

" crop of 142

Pigment in skin 92

Pipn 94, 95

Pipe-fish 63

Page

Pineal body 106

Pinrtipedia .... 179

Pinna of ear 153

Pintail 139

Pisidium 232

Piscicola 222

Pimelodu8 56

Planaria 225

Planorbis 234

Plantigrade 179

Plants contrasted with Ani-
mals 266-7

Plants, protective organs of. . 288

Plants, carnivorous 288

Plants, relations to animals . . 288

Plantlice 213

Plastron 102

Platalea 136, 139

Plathelminthes 225

Platydactylus 109

Ptatyrrhini 188

Platypus (duck-mole) 160

Plautus 137

Plectognathi 71

Pkthodon 91

Plesiosaurus 116

Pleuronectes 69, 70

Pleural cavity 158

^leurum of insects 206

/'lotus 138

Plover 139

Plumatella 240

Podiceps 1:5, 138

Podophthalmata-i 195

Podura 210

Poephagus 179

Poison apparatus of Ophidia .112-3

Of Scorpions 202

Spiders 203

Insects 217

Polychceta 220

Polyodon 73

Polypterus 75

Polymorphism of Polyzoa .... 237

of Hydrozoa 247

Polyzoa 237

Polyp 245

Porcupine 183

Pomoxys 64

Pondturtle 100

308

INDEX.

« .. Pa^e

Port/em 249

Pons Varolii 151

Pontiporeia 198

Porcupine anteater 160

Porcus 175

Porcula 175

Porcupine -fish 71

Pores of sponges 254

Portal vein 42

Posterior extremity 85

Potato beetle 215

Pouch of Marsupials 143

Prairie-hen 140

dog..... 184

Prawn 197

Precoces (aves) 131

Precoracoid 83

Premaxilla 25

Premolars 155

Preoperculum 25

Prestomium 222

Primates 188

Primaries 122

Primary and secondary girdles 27

Primitive characters 10

Pristis 76

Proboscis of insects 212

Proboscidea 168

Proboscis of leeches 222

Procellaria 138

Procyon 179

Proglottis : .... 226

Propithecus 188

Pronghorn 178

Prosimii 187

Prosobranchiata 234

Protection and protective re-
semblance 210, 216, 287

Colouration 82, 108

In Cephalopoda 237

Proteids 263

Proteus 88

Protracheata 211

Protoplasm 263

Protopterus 78, 80

Prototheria 160, 143

Protozoa 252-261

Proventriculus 129

Psalterium 176

Pseudopodia 253, 255

Pseudoneuroptera . 212

Pseudobranch 57

Pseudoscorplonma 202

Psittaci 141

Psocus 212

Psychology 267

Ptarmigan 140

Pterosaurla 120

Pterodactyl 119

Pterotic 22

Pteropoda 235

Pteropus 186

Puffin 137

Pulex 216

Puma 179

Pupa of Locust 209

Putorius 179

Pulmonary artery and vein . . 87

Pulmonata 2.J4

Pyloric cceca 60

Python Ill

Pyloric valve 39-41

Pygostyle 126

Pygopodes 137

Quadrate 25

Homologueof in Mammals 149
Quadrumana 187

Race 52

Racoon 179

Radial Symmetry 242

Radiata 242

Radiolaria 255

Radius 85

Radula 234

Rallus 139

Rana 92, 96

Ranatra 213

Ranyifer 178

Raptores 140

Rat 184

Rattle, Functions of 113

Rattle-Snake 113

Ratitce 132

Ray (Raja) 76

Rays 242

Rectrices 122

Recur viroatra 136

Red-Coral 248

INDEX.

soa

Page

Redia 226

Regions of Body in Vertebrates 1 1

Reflex Action 39, 267

Reindeer 178

Remiges 122

Renal-portal circulation . .49, 57

absence of in mammals. . . 160

Reptilia 99

Rennet-stomach 176

Reproduction by budding, Nais 221

Respiratory system 43, 265

turtles 103, 105

earthworm 221

Reticulum ... 176

Retina 35

Retinophoral cells 195

Retinula 195

Reversion in horse 172

Rhabdome 196

Rhacophorus 97

Rhamphorhynchus 120

Rhea 134

Rhinoceros 171

bird 141

Rhizopoda 253

Rhynchonella 237

Rhyparochromus 214

Rhynchops 136

Rhytina 166

Roc 134

Rock-pigeon 140

Rose of Antlers 178

Rostellum of Cestodes 227

Rostrum of sharks 76

RotaVia 255

Rotifera 204, 222

Rudimentary organs 287

hind limbs of Ophidia 111

Ruddy-duck 139

Rumen 176

Ruminants 175

Rupicapra 179

Saccobranchus 57

Sacculus 37

Sacral region 85

Salpingozca 257, 258

Sagittal plane 10

Salamander 90

Salivary glands 156

Page

Salivary glands, Insects .... 208

Salmo 58

Sauropoda , 117

Sauropterygia 117

Sauropsida . . . -~ 99

Sandpiper 139

Saprophytic life of Infusoria. . 256

of Fungi 288

Sarcorhamphus 136

Sarcoptes 204

Sarcodina 253

Sarracenia 288

Saururoz 122

Sawfish 76

Sawflies 217

Scales of turtle 101

of fish 12

of insects 212

of Ophidia Ill

Scalops 183

Scallop 232

Scansorial feet 141

Scaphopoda 235

Scapula 27

Scapanm 183

ScarabcBUS 215

Sceloporus 107

Scaphirrhynchops. 73

Sclerotic coat of eye 34

Sciurm 184

Sciuropterus 184

Sclerostomum 225

Scolopendrella 210

Scomberesox 63

Scomber 67

Scoter 139

Scorpion 202

Scutum of insects 206

Scutigera 211

Scutetlum 206

Sea-anemony 247

Sea-cow 166

Sea-cucumber 243

Sea-elephant 181

Sea-lion 180

Sea-horse 63

Sea-pigeon 137

Sea-otter 179

Sea-urchin 242

Sea-snake 113

310

INDEX.

Pasre

Seal 180

Sebaceous glands 145

Secondaries 122

Sedimentary Strata ....... 268-71

Segmentation of egg in fowl . . 131

of Crustacea 192

of Myriapoda 211

Segmented and unsegmented

worms 220

Segmental organs 218

Selache 77

Sella turcica 149

Selenodont 176

Semi-circular canals, mammals 154

of Fish 37

Semnojnthecus 189

Serranus 66

Senses of insects 207

Sepia 235

Sepia 237

Septa of Actinozoa 248

Serous coat of intestine 39

Sesamoid bone (formed in ten-
don)' 164

Sesia 216

Setae of earthworm 220

Siphoniata. 232

Shad 60

Sharks 76

Sheat-fish 55

Shell of Mollusca 236

Shell Brachiopoda 237

Sheep 179

Shiner 57

Shrew 182

Shields of turtle 101

Shrimp 197

Shrike 141

Shoveller 139

Shovel-nosed Sturgeon 73

Sieve-plate of ethmoid 153

Silkworm 216

Silurus 55

Simia 189

Simple eye 203

Simulia 216

Siphons . . 229

Siphonops 98

Siren 89

Sirenia 166

Page

Skeleton fowl ,.<... 125

Skeletal system 17

of Actinozoa 248

of Protozoa 254

of Radiolaria 255

of Sponge 250

Skull of cat 147

of Menobranch 82

Skull 103, 134

Vertebrate, theory of ... . 20
"Union of, with vertebral

column 126

Skunk 179

Skin 12

of Menobranch 81

of Turtle 101

of Aquatic Urodela 92

Skink 107

Skimmer 136

Slater 198

Sloths ' 163

Slough of snake Ill

Slime-cells 17

Slipper-animalcule 258

Smelt 60

Snakes Ill

Snapper 100

Snipe 139

Social life of Hymenoptera . . 216

Soldiers of Termites 212

Sole 70

Solitaire 140

Somateria 139

Sorex 182

Sparrows 141

Spatula 139

Spawn of frog 94

Species 51, 284

Specialisation 70

Spleen 47

Spectre ( Tarsius) 187

Spermophilus 184

Speotyto 140

Sphenotic 22

Sphenoid, complex, in mam-
mals 145

Sphex 217

Sphinx 216

Spinal cord 32

Nerve roots 32

INDEX.

Page

Spinnerets 201

Spiracles of locust 204,208

Offish 72

Spiral valve 73

Spirifer 238

Sponges 249

Spongllla 250

Spoonbill 139

Spores of Sporozoa 256

Sporocyst 226

Sporozoa 256

Squid 235

Squash-bug 214

Squamosal 82

Squirrel 184

Stapes 83, 153

StaphylinidcB 215

Starfish 243

Statoblasts 240, 241, 251

Steganopodes 138

Stegosaurus 117

Stenops 187

Stercorarius 138

Sternum 93

Of Insects 206

Stmtor 259, 260

Sterna . . .- 138

Stigmata 204

Stickleback 63

Stipes 206

Stizostedium 66

Stomach Ruminant 176

-Sac Actinozoa 248

Ccecal Type of 41

Mammals 158

Stonecat 54

Stoneflies 212

Stork 139

Storeria 114

Strix 140

Stronqylus 225

Struthio 134, 135

Sturgeon 72, 73

Stylets 212, 216

Stylommatophora 234

Stylohyoids 150

Subcutaneous Tissue 12

Suberites 252

Sublingual Gland 157

Submentum 206

Page

Submucous Tissue „ 40

Submaxillary Gland 157

Suboperculum 25

Succinea 234

Sucker 57

Suckers of Leeches 222

Sucking-Fish 67

Suctorial Infusoria 260

Sus 174

Sula 138

Sunfish 64

Surinam Toad 94

Supraclavicle i3, 27

Supraoccipital 22

Suspensorium 82

Suture 21

Swallow 141

Swan 139

Sweat-Glands 145

Swift 141

Sword- Fish 67

Sylphidm 215

Symbiosis 255, 282, 286

Sympathetic nervous sys-
tem 33

Symphysis of pelvis 128

Syrinx 130, 131

Syngamus 235

Syngnathus 63, 64

Tabanus 216

Table of species 274-6

Sedimentary strata 271

Tachypttes 138

Tadpole 94

Taenia 227

Talpa 182

Tamias 184

Tanager 141

Tapirus 171

Tape-worm 226

Tardigrada 204, 223

Tarsius 187

Tarso-metatarsus of birds 128

Tarsus of Menobranch 84

of insects 206

Tasmanian devil 162

Taste-buds 157

Taxidea 179

Taxonomy 272

jia

INDEX.

m , Pa»e

Teal 139

Teeth, Menobranch 86

Echidna 161

Whales 165

Formulae of 156, 157

Correlation of to habits . . 154

Teleosts, development of ... . 50

Teleostei 10, 71

Tellina 232

Telson 192

Temporal bone mammals 148

Tentacles of Hydra 245

of suctorial Infusoria. .. . 260

Tenthredo 217

Tentorium cerebelli 149

Teredo 232

Tergum of insects 236

Terminal lamina 152

Termites 212

Terricolous worms 220

Testicardines 238

Tetrabranchiata 236

Tern 138

Tertiaries 122

Testudo 105

Thalamic region of brain. .31, 152

Thalamophora 254

Thorax of arthropods 193

of insects 206

of mammals 158

Thread-cells 245

Thrush 141

Thryps 212

Thylacinus 162

Thymus 44

Thyrohyal 150, 159

Thyroid 44

Thyroid cartilage 159

Thysanura 210

Tibia of insects 206

Tibio -tarsus of birds 128

Ticks 204

Tinamu 140

Tinea 216

Tissues 16

Tits 141

Tiger 179

Tobacco-pipe fish 63

Tooth, Structure of 16

Tooth-shells 235

Page

Tongue of Anura 94

of Birds 129

of Mammals 156

of Bee 217

Tonsils 157

Top-shells 235

Torpedo 77

Tortoise-shell 101

Totanus 139

Totipalmate 135, 138

Toucan 141

Trachea (windpipe) 131, 159

Tracheae of Arthropods 205

Tracheal gills 212

Tragulus 177

Transverse processes 19

Transect 10

Trap-door spiders (Myogale) . . 203

Tree-toads 92

Trematodes 225

Trichechus 181

Trichina 244

Trichuriasis 225

Trichocysts 259

Trichoptera 214

Trilobites 201

Trlobite-phase of Limulus .... -201

Tringa 139

Trigla 59

Triton 91

Trionyx 104

Trochanter of insects 206

Trochantine " 206

Troglodytes 189

Trombidium 204

Tropical catfish 56, 57

Tropidonotus 114

Trout 59

Tropic-bird 135

Truncus arteriosus 45

Trunkfish 71

Tube-feet 243

Tubipora 248, 249

Tunny 67

Tupaja 183

Turbellaria 226

Turbinals of mammals 148

Turbinares 138

Turbo 234

Trochus 235

INDK.V.

313

m . Page

Turdus 136

Turkey 139

Turtles 105

Tusks of Sus 175

as compensatory to ab-
sence of horns 177

Tylenchus 224

Tympanic bone 148

Tympanic cavity 93

Tympanic membrane 93

Tympanuchus 140

Typhlops Ill

Typhlosole 219

Tyroglyphus. . , 204

Uakari 188

Ulna 85

Umbo 229

Umbra 62

Uncinate processess 127

Unconformable strata ........ 270

Unguiculata 167

Ungulata 167

Unicellular animals 252

Unio 228

Unsegmented worms 222

Ureter 47

Urinary bladder 47

Urinator 138

Ursa 179

Utriculus 37

Urodela 88

Uvula 157

Valvata 235

Vampire-bat 186

Vampyrus 186

Varanus 1<>7

Variation 267, 284

Variety 52

Vascular system 44-5

Crayfish 196

Velvet of antlers 178

Veins 44

Venous sinus 45

Ventricles of brain 31

Vermes 218-232

Vertebrata 9-189

Vertebrate 9

Page

Vertebral column

IS, 19, 93, 103, 111, 146

Vertex 122

Vespa 217

ytxpertiUa 186

Vestibule of Labyrinth 154

Vibrissae 1 4.1

Vicuna 177

Visceral skeleton

20, 24, 93, 1! 3, 149

Vitreous 3.1

Viverra 179

Viviparous snakes 114

Vocal organs locust 208

Vocal-sacs frog 94

Vomer 23

Vortkella 249, 60

Vultur 141

Wallace 285

Wallace's line 281.

Walking-stick insect 210

Walrus 181

Warbler 41

Wart-hog 175

Wasp 217

Water-bug 213

-flea 199

-vascular system of won as 223

of Echinodermata 243

Weasel 179

Web, spiders 204

Weeds 285

Weevil 215

White-ants 212

White-fish 59

Wheel-animalcules 223

Wheat- worm 224

Whales 165

Widgeon 139

Wings, bird's 122

Insect's 207

Wolverine 179

Woodchuck 184

Woodcock 130

Wood-duck 139

Woodlouse 198

Woodpecker 141

Wren 141

Wryneck 141

314

:x.

Page

Xiphias 67

Xiphodon 176

Xiphoid Cartilage 147

Yak. 179

Yellow-Cells of Radiolaria. . . 255
Yolk-Sac ,,... 49

Page

Zapus 184

Zebra 173

Zebu 179

Zenaidura 140

Zonites 234

Zoophytes 245

Zygomatic Arch 148

Prints© bt The Com>s Clark Comtany, Lt-mitkd, Toronto,

ustotie.

The following suggestions as to the order and scope of the practical
lessons which should precede the study of the Text-Book as a whole
may be of use to Teachers. The References are to Chapters and
Sections of the Text-Book.

1. Thorough examination of the external form (I. 1-5), the gills (56)
and the viscera (49-65) of some common fish.

2. Study of the prepared skeleton — preferably of the catfish, on
account of the assistance to be obtained from the figures (I. 10-30).

3. Demonstration of the arrangement of the muscular and nervous
systems (31-35, 37) and the sense-organs (41-3) as far as these can be
studied without the aid of the microscope.

4. Comparison of the structure of the frog (III. 16-22) with that of
the fish, and with that of the Menob ranch described in III. 1-10. The
skeleton of the pectoral and pelvic girdles and of the appendages
of the frog, should be compared with the figures of the same parts in
the Menobranch (III. 5).

5. Examination of the external form of a Turtle (IV. 1-12) and a
Snake (17-20).

6. Examination of the structure of a pigeon or a fowl (V. 1-3, 5-12).

7. Study of the skeleton (VI. 5-7), also of the teeth and viscera
(11-16) of a cat or dog.

8. Study of a crayfish as a type of the Arthropods (VII. 1-11).

9. Comparison of the Crayfish with an Insect — Grasshopper, Cricket,
or Cockroach (19-26)— also with a Millipede (23) and a Spider (17).

10. Examination of an Earthworm and Leech (VIII. 1-6).

11. Study of a fresh-water mussel and s pond-snail (VIII. 14-20).

12. The principles of Zoological nomenclature (II. 1-8) as illustrated
by some of the common fresh- water fish, such as the sucker and herring
(9-11), bass and perch (17-18).

13. Study of an Amoeba or Paramoeciuni as a type of an unicellular
animal.

14. Cells and tissues of the higher animals (I. 6-9) and the microscopic
structure of their organs (I. 11, 31, 38, 44, 48, II. 2, VI. 4).

15. Development of the eggs of fish in the Spring (I. 66), and the
metamorphosis of the tadpole (III. 21).

In addition to practical lessons such as those indicated above, the
following topics ought to be illustrated by figures, diagrams, etc : —

The modifications of the form of the body in Vertebrates in con-
nection with different methods of locomotion — Figs. 30, 39, 41, 43, 65-
68, 71-2, 74-5, 78-9, 81, 84-90, 92, 95, 98-9, 106, 108, 111-3, 115, 116-7.

The characters of the orders of Mammalia (VI. 17-41) [large type] and
their geographical distribution — compare X. 16-16 and map.

The succession of the fossiliferous rocks (p. 271) and the importance
of the Ganoids (II, 24), the fossil Reptiles (IV. 22-26), the Trilobites
(VIII. 15), Brachiopods (VIII. 25) and Corals (IX. 6), from a Palseonto-
logical standpoint.