OOLOGY

PRACTICAL

TO RO 1*1 TO
THE QQPW, ©LARIC OQMPAMY, LlMil'i©

INDON PUBLIC LIBRARY

& ART MUSEUM
LONDON - ONTARIO

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& ART H'

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ZOOLOGY

DESCRIPTIVE AND PRACTICAL

BY
BUEL P. COLTON, A.M.

AUTHOR OF "PHYSIOLOGY, EXPERIMENTAL AND DESCRllTIVE," " PHYSIOLOGY ;

ILLUSTRATED BY EXPERIMENT," " ELEMENTARY PHYSIOLOGY,"

"PRACTICAL ZOOLOGY"; AND PROFESSOR OF NATURAL

SCIENCE IN THE ILLINOIS STATE NORMAL

UNIVERSITY

^art I
DESCRIPTIVE

D. C. HEATH & CO., PUBLISHERS

BOSTON NEW YORK CHICAGO

THE VOICE OF THE SEA

"The child holds a shell to his ear and hears the roaring of
the sea. Do not yet tell him that the sound he hears is only
the echo of the rushing of blood in his own head. In a higher
sense the child is right. To him it speaks of the sea, its home.
It brings the inland child a message from the vast ocean — the
distant — the mysterious. It widens his narrow horizon; it
takes him to the shore whose waters wash all other shores. He
IS no longer isolated, but put in touch with all the world. And
this typifies the broad principle that one fact — considered in all
its relations — involves the whole universe."

Copyright, igog,

By BUEL P. COLTON.

xi

2 B4

PRINTLU L\ U. S. A.

PREFACE.

The Plan. — The general plan of the book is to introduce each of
the larger groups of animals by the careful study of a typical repre-
sentative. It is the aim to present a fairly complete picture of the life
of this type, — its place of living ; its manner of securing food ; its
enemies and its means of protection; its mode of locomotion; the
processes of digestion, circulation, and respiration ; its sense organs ;
its development ; its relations to the plant world, to other animals, and
to man. Following the study of the type is a general account of
representative forms. The characteristics of the group are given in
summarized form. Each chapter closes with a tabular classification
of the group.

Time for the Study of Zoology. — Of the three seasons during
which school is in session, winter is the least desirable for the study
of animals. Many of the birds have migrated ; most of the insects
have been killed ; those that remain alive are in close hiding and are
hard to find, and still more so are their eggs, larvae, or pupae. A large
number of animals are hibernating. Animal life is at low ebb. The
choice of time, then, is practically limited to fall and spring. While
there is an abundance of life in the spring and some forms can better
be studied then, on the whole animal life is at its highest activity in the
fall. Again, since spring is preferred for botany, the fall seems the
best time for zoology.

The Order of'Study. — The chief aim is to understand the lives
of animals. To know them it is necessary to study them in relation to
their surroundings. To do this to the best advantage they should be
studied when at the hight of their activity. These points, then, must
largely determine the order of study. For instance, if zoology is begun
in the fall, one finds insects active and abundant. Many forms are
laying their eggs to produce the generation of the following spring

iv Preface.

They should be studied before the season of frosts. On the other
hand, fishes can as well, or better, be studied later. Since the natural
history point of view is prominent, the general principle regulating the
order of study should be, " follow the season." The birds, too, should
receive attention during the first part of the term, for many of them
migrate early. It is not necessary, nor always desirable, to complete
the study of one group before beginning another. Two lines of work
can profitably be pursued on alternate days or weeks.

For fall work, the order here given has been found satisfactory.
But circumstances call for considerable variation ; it is not necessary to
follow any given order with slavish fidelity. If the work begins in the
spring, the teacher may prefer to begin with the crayfish, clam, fish,
or frog.

There are some advantages in beginning with the lowest animals
and studying them in the ascending order. This gives the clearest
idea of the natural sequence of the animal kingdom.

Other things being equal, it would be better to study animals in their
logical sequence, just as we prefer to learn historical facts in their
chronological order. But there are very serious objections to this
order. First, it involves the use of the microscope at the outset. This
is impossible for many schools. Further, the tise of the microscope is
like a new language, which must be translated. Even if the student
has a microscope and has mastered its technique, he still has difficul-
ties. What he sees is very different from his previous observations.
All our knowledge is knowledge of relation. Until the new is related
to that already known, it means nothing. The very simplicity of the
Protozoan makes it hard to understand.

If, however, the teacher decides upon this course, the work may
begin with Chapter XVIII. By following the remaining chapters and
then beginning with Chapter I, the ascending order will be followed
with a few slight exceptions. But, as before stated, the teacher should
not be tied down to any fixed order. Zoology is the study of animals.
For most schools, the best time to study animals is* when they can be
most easily collected, for two reasons. First, it involves expense to
keep them on hand to use at a later date. Second, and more impor-
tant, the sooner they are studied after collection, the better. At this
time some of the facts as to their source will appear, even if the students
have not assisted in the collecting. The study of the home life and
natural surroundings is of vital importance, if the student is to get

Preface. v

beyond morphology into the fields of natural history, ecology, and
economic relations.

The Place of Nature Study. — Many teachers of natural his-
tory are accused, often very justly, of placing too high a value on the
subject. The true teacher will try to see the real place of his subject
in the course of study. Natural history cannot claim the highest place.
Interesting as are the actions of animals, they cannot compare with the
deeds of men. History is above natural history as man is above the
other animals. But the student who has formed the habit of seeking
the meanings of facts in natural history will carry this habit into the
study of history. The study of natural history should come first, for
children are interested in animals. The habits of observation and
interpretation once formed will be carried through life and applied in
every line of thought. To cultivate these habits should be the con-
stant aim of the teacher. The study of animals especially lends itself
to such training, because of the child's inherent interest in the subject,
and because of the varied adaptations to their surroundings that animals
everywhere exhibit.

The Interpretation of Nature. — The study of the relations
of animals to their surroundings is a constant investigation of cause.
The student must ask why an animal has a certain color, form, or habit.
He must first learn to observe the facts that come within the range
of his experience. Next, he must seek an explanation of these facts.
He must become possessed by the idea that every fact has a meaning,
and that it is worth while to think out this meaning. At first he must
be helped ; but he is to learn that he must rely mainly on himself for
the solution of the problems of animal life.

Classification. — It is highly important that the student learn how
to classify animals ; that he commits to memory a system of classifica-
tion is of doubtful value. To classify is simply to sort, or to arrange,
things according to their likenesses. The child sorts his blocks; that
is, he puts those of a kind together. Those of different kinds are
separated. This is classification, — a grouping according to resem-
blances and differences. But the child cannot sort blocks unless he
has them. Neither can the student classify animals unless he knows
them. It is impossible to classify the unknown.

VI Preface,

As the facts concerning the different kinds of animals become known,
they must be sorted and arranged according to some system. The
basis of classifying animals is structure. Of course the beginner
cannot go deep into anatomy, but he must know some of the more
important facts of structure or else his attempt at classification is com-
paratively useless. Since it is usually impracticable to study animals
in systematic order, the student must learn to arrange his knowledge
as he proceeds. This is not different from mental growth in other
lines. Our experiences do not come to us classified. Just as an
orderly merchant sorts his new goods, and arranges them on shelves
with previously acquired articles of the same kinds, so the student must
arrange in systematic order his ever increasing stock of knowledge.

At the close of the volume will be found the classification of the
animal kingdom according to Parker and Haswell, whose arrangement
is considered the most authoritative of recent works.

The Value of the Study of Types. — Real knowledge comes
through experience. What one learns through another is information.
The teacher must distinguish between first-hand knowledge and second-
hand knowledge. Now the number of animals that any student can
examine is small in comparison with the number in existence. The
study of the animal kingdom is greatly simplified by the fact that, with
all the variety of animal forms, there are actually but few different plans
of structure. One important part of the teacher's work is to select the
best types for careful study. On the foundation thus laid much infor-
mation may be built. If one had never seen a Crustacean, he would
get little from reading about Crustaceans. But, after studying a cray-
fish, a fairly clear idea of a lobster or a crab may be obtained by read-
ing, for a foundation has been laid in sense perception.

The knowledge of a type may be compared to a peg in a wall ; if it
is driven in solid, it will hold many facts of information.

The types selected, their number, and the thoroughness with which
they are studied will naturally vary with the locality, season, the age
of the student, the time allotted to the study, and various other
circumstances.

Definitions. — The stadent should be taught to make definitions.
By comparing a number of related forms, as suggested in the practical
work on insects, the student should see what characteristics they have

Preface. vii

In common. Thus he is enabled to distinguish groups. Memorized
definitions have comparatively little value. "A neat definition is a
very attractive thing. It seems to offer the sum and substance of
wisdom in portable form. But to understand it, to comprehend what
it includes and what it excludes, the thoughts of the master must be
gone over again in the mind of the disciple, — and then he no longer
needs the definition." But definitions, however made, are often mis-
leading. The fact is that nature has not sharply and distinctly sepa-
rated animals into groups. There are usually no hard and fast lines
between them. If we try to establish a dividing Hne, we almost always
fina it cutting across some intermediate forms. Since the groups of
animals overlap, and gradually shade off one into another, it is better
not to try to think of them as having definite boundary lines. We
should rather consider each group as arranged about a type at the
center.

Practical Work. — It has been thought best to place the practical
work in the latter part of the book. But this work should, of course,
precede the assignment of lessons in the descriptive text. Effort has
been made to correlate the two parts so that they may be used together
to good advantage. The author is well aware that in many schools the
facilities for field and laboratory work are very limited. He has, there-
fore, thought best to err on the safe side and give rather full descrip-
tions. But the teacher should see to it that the student himself solves
as many as possible of the problems.

The teacher may find help in the " Suggestions to the Teacher of
Zoology," which is issued in pamphlet form by the publishers of this
book.

Economic Importance of Animals. — The common schools aim
primarily at intellectual acquisition and training rather than at indus-
trial application. Still, the economic side of the study of animals
should be kept clearly in miiid. The public has a right to demand
that the knowledge gained in school shall have some practical value.
The economic side, too, is one of the most interesting, and should
receive attention for this reason, if for no other. This is a line of work
in which collateral reading may be most profitably followed. There
are many Reports of the Department of Agriculture which may be
obtained free on application to the Department of Agriculture, Wash-

vili Preface.

ington, D.C. These pamphlets may serve as the nucleus of a reference
library. These reports, and as many other books as the school can
afford, should be accessible to the student, and he should be encouraged
to use them freely.

Acknowledgment. — The manuscript, entire or in part, has been
critically read by Professors M. A. Bigelow, Teachers College, Columbia
University; H. Garman, State College of Kentucky; F. R. Lillie,
University of Chicago ; T. H. Montgomery, University of Pennsyl-
vania; M. M. Ricker, Burlington, Iowa; and J. M. Tyler, Amherst
College. The manuscript has been corrected by Miss Chestine Gowdy,
teacher of grammar, Illinois State Normal University.

The proofs have been read by Professors M. F. Arey, State Normal
School, Cedar Falls, Iowa ; A. C. Boyden, State Normal School, Bridge-
water, Massachusetts; M. J. Elrod, University of Montana; J. W.
Folsom, University of lUinois ; H. Garman, State College of Kentucky;
W. S. Jackman, University of Chicago ; H. S. Jennings, University of
Michigan; J. M. Johnson, Peter Cooper High School, New York;
S.J. Hunter, University of Kansas ; Louis Murbach, Detroit High
School; Frank Smith, University of Illinois; H. B. Ward, University
of Nebraska. To all of these the author extends his most sincere
thanks. Their criticisms have weeded out many errors ; but for those
that remain they are in no way responsible.

In most cases the sources of the cuts are indicated in the captions.
About forty of the cuts are original. The drawings of the clam were
made by Mr. Frank J. George, now a teacher in the Philippines. Most
of the other original drawings were made by Miss Esther Mohr.

Normal, Illinois.

CONTENTS.

CHAPTER PAGB

1. Branch Arthropoda — Class Insecta i

II. Branch Arthropoda — Class Insecta {Continued) . . 25

III. Branch Arthropoda 54

Class I. Myriapoda 54

Class 2. Arachnida 55

IV. Branch Arthropoda — Class Crustacea .... 61
V. Branch Arthropoda — Class Crustacea ( C<?;//m«^</) . . 77

VI. Branch Annulata — The Segmented Worms ... 87

VII. Branch Mollusca — Class Pelecypoda 102

VIII. Branch Mollusca — Class Gastropoda . . . . .127

IX. Branch Mollusca — Class Cephalopoda .... 138

X. Branch Chordata 148

Subbranch Urochorda 148

Subbranch Vertebrata 151

Qass I. Cyclostomata 153

Class 2. Pisces 154

XI. Branch Chordata — Class Pisces {Continued^ i-. . .168

XII. Branch Chordata — Class Amphibia 181

XIII. Branch Chordata — Class Reptilia 196

XIV. Branch Chordata — Class Aves 208

XV. Branch Chordata — Classification of Aves .... 222

XVI. Branch Chordata — Class Mammalia 246

XVII. Branch Chordata — Classification of Mammalia . . . 256

XVIII. Branch Protozoa — The One-celled Animals . . . 286

XIX. Branch Porifera — The Sponges ...... 307

XX. Branch Ccelenterata 313

Qass I. Hydrozoa 317

Qass 2. Scyphozoa 323

Class 3. Actinozoa 325

ix

Contents.

CHAPTKK PAGE

XXI. Branch Echinodermata ...,,,. 331

Qass I. Asteroidea 331

Class 2. Ophiuroidea 337

• Class 3. Echinoidea 338

, Class 4. Holothuroidea 343

Class 5. Crinoidea 345

XXII. Branch Platyhelminthes — The Flatworms . . . 348
Branch Nemathelminthes — The Roundworms . . .351

Branch Trochelminthes — The Rotifers .... 352

Branch Molluscoida 353

XXIII. Classification of the Animal Kingdom .... 355

Index 359

ZOOLOGY: DESCRIPTIVE AND
PRACTICAL.

PART I. DESCRIPTIVE.

CHAPTER I.
BRANCH ARTHROPODA.

CLASS INSECTA.
Example. — The Grasshopper.

The Life of an Animal. — In order to understand the life
of any animal, try to get answers to such questions as these :
Where does it live } How is it adapted to its surround-
ings ? What does it eat, and how does it get its food ?
What are its enemies, and how does it escape them ?
What is its chief mode of locomotion ? What is it doing
most of the time ? What seems to be its main object in
life ? What changes does it undergo in its growth ? Does
it eat the same kind of food, breathe in the same way,
move in the same way, or live in the same conditions dur-
ing the different stages of its development ? How does it
affect plant life ? What is its influence on other animals ?
Is it useful, either directly or indirectly, to man .^^ Is it
either directly or indirectly injurious to man ?

Home Life of a Grasshopper. — As indicated in its name,
we find this insect on plants. So well does its color har-

Insecta. 3

monize with its surroundings that we often fail to see the
grasshopper when it is right before our eyes. Even when
we have frightened a grasshopper, and watch its jump or
flight, on going to the place where we saw it alight we do
not always readily discover it.

The plant on which the grasshopper rests serves both
as food and as shelter ; it is its home, so far as it can be
said to have a home. Food usually being abundant, the
grasshopper moves about but little, and leads a rather
sluggish life.

Locomotion of the Grasshopper. — The grasshopper has
three modes of locomotion, crawling, jumping, and flying.
The wings and legs are moved by the strong, white,
striated muscles, which are situated chiefly in the thorax.

Crawling. — This is accomplished mainly by the first and
second pairs of legs, the hind pair making fewer movements
in the ordinary slow crawl. The hooked claws enable the
grasshopper to retain a firm hold while crawling.

Jumping. — The length and strength of the hind legs fit
the grasshopper for powerful jumping. The spines on the
hind border of the tibia keep it from slipping.

The Wings and Flying. — The anterior pair of wings
serve mainly as covers for the hinder pair, and their com-
parative thickness and toughness fit them well for this use.
Jl^ The hinder pair of wings are much wider, being folded
like a fan when not in use and wholly covered and pro-
tected by the anterior pair. The hinder pair are more
delicate in their texture, but still are sufficiently strong for
their work in flight, being stiffened by the hollow veins
which radiate through them. The grasshopper is crawling
through the grass or resting quietly on stems and leaves
most of the time, and is flying only a small part of the

OtvUniv^

Ni:: — -^-^-i— rV'-^ .

^rC^ ScuieUum {^

Fig. 2. ExTERNAi Features of a Grasshopper, Dorsal View.

JVom Packard's Zoology,

Insecta. 5

time. So we can see the fitness of having the flying wings
folded compactly and placed close to the sides and guarded.
The wings are kept from mutilation, and the whole insect
is much less conspicuous than he would be with the wings
outspread. Some grasshoppers fly high in the air and
travel long distances.

Respiration in the Grasshopper. — The spiracles are
shown in Fig. i ; two ...pairs of thoracic and eight pairs
of abdominal openings. From these spiracles, tubes.

Fig. 3. Cross Section of Insect.

a = Digestive Tube.

called tracheae, run inward to a trachea extending length-
wise on each side of the body. There is also a pair of
dorsal and a pair of ventral air tubes. There are, then,
six air tubes running lengthwise, in communication with
the outside air through the spiracles, and connected with
each other by branches. From these main tubes branches
extend which subdivide, finely permeating every part of
the body, even, to a limited extent, the legs and the larger
veins of the wings (see Figs. 3 and 4). In addition to the
air tubes there are two rows of air sacs, which add to the

6 Descriptive Zoology.

buoyancy during flight. The work of respiration depends
on the abdomen, as the thorax is rigid. The abdomen is
made smaller by the action of its muscles, and expands
again when they relax. Expiration seems to be accom-
plished by active effort, and inspiration by elastic reaction,
just the reverse of the breathing process in man.

Circulation in the Grasshopper. — The circulatory system
of the grasshopper is not highly developed. The only dis-
tinct organ is the heart (see Figs. 3 and 4), extending along

Oorsal air-tube

Fig. 4. Air Tubes and Air Sacs of Grasshopper.

From Hyatt's Insecta.

the dorsal part of the abdomen. It is in the form of a
tube, closed behind and open at the anterior end. It has
several compartments, with valves, which allow the blood
to pass forward only. There are also openings with valves
at the sides, so that blood enters when the tube widens, and
when it contracts the blood is pumped forward. The
blood is colorless, or slightly yellowish or greenish, and
fills all the otherwise unoccupied spaces of the body, thus
bathing all the tissues. The low development of the cir-
culatory system is compensated for by the high develop-

Insecta. 7

ment of the respiratory system, which conveys air to all
parts constantly. Thus the insect is enabled to exert its
muscles powerfully and rapidly, and in general maintain
the high degree of activity which is so characteristic of
the group. As might be expected, the temperature of
insects is high, compared with that of invertebrates in
general, being several degrees above that of the surround-
ing air.

The Grasshopper's Food and Digestion. — Eating is a large
factor in the life of the grasshopper. We see it on many
kinds of plants, gnawing leaves and stems with its short,
strong, laterally moving jaws. The narrow gullet extends
upward to about the center of the head, then turns pos-
teriorly and dilates into the crop, which runs lengthwise
in the thorax. At about the beginning of the abdomen
the crop narrows somewhat and becomes the stomach.
Alongside the crop are the branched salivary glands, whose
ducts run forward to empty into the mouth. At the place
where the crop joins the stomach it is surrounded by a set
of six or eight double-cone-shaped pouches extending par-
allel to the digestive tube itself. These bodies are the
ceca. They are hollow and communicate with the cavity
of the digestive tube by openings. The ceca secrete a
liquid that aids in digestion ; they increase the surface of
the digestive tract and probably are largely concerned in
the work of absorption. The stomach extends about half
the length of the abdomen. Its posterior limit is marked
by a large number of slender tubes, the urinary tubes,
which enter the digestive tube at the juncture of the stom-
ach and intestine. The last part of the intestine is some-
what dilated, forming the rectum, which, in turn, terminates
in the anal opening at the upper part of the end of the
abdomen.

8 Descriptive Zoology.

Absorption in the Grasshopper. — The absorbed food ma-
terials from the digestive tube pass directly into the general
blood of the body cavity, there being no special set of
tubes as in man and vertebrates generally.

The Excretory System of the Grasshopper. — The urinary
tubes (formerly called the malpighian tubes) extend into
the blood of the body cavity and extract from it essen-
tially the same materials as the kidneys of the higher
animals do. As above stated, these tubes empty into the
intestine.

The Nervous System of the Grasshopper. — The nervous
system of the grasshopper is essentially like that of the
crayfish (Fig. 49), consisting of a row of ganglions con-
nected by a nerve cord lying along the floor of the body
cavity. It really is composed of two rows of ganglions,
each connected by its own chainlike cord; but usually
the two corresponding ganglions unite, forming what seems
a single ganglion. In the grasshopper, the nerve cord is
plainly double throughout the head and thorax, while in
the abdomen the cord appears single. There are ten gang-
lions, two belonging to the head, three in the thorax, and
five in the abdomen. The first ganglion, often called the
brain, is above, or rather in front, of the gullet. From this
the two strands of the nerve cord pass to right and left of
the gullet and again unite in the second, or infra-esophageal
ganglion, forming the nerve ring (" nerve collar ") found in
arthropods and mollusks.

The Senses of the Grasshopper. — It is very evident that
the grasshopper can see and hear, and it does not require
extended experiment to show that it has also the sense of
touch. The large compound eyes, composed of many
facets, give a wide range of vision ; but the sense of sight

Insecta,

is probably not very acute, especially at any considerable
distance. The clear membrane on the first segment of the
abdomen is the tympanum
of the hearing organ. The
antennae are the chief or-
gans of touch.

The Enemies of the Grass-
hopper.— Probably birds
are the most formidable
enemies of the grass-
hopper. The grasshopper
usually becomes aware of
the approach of an enemy
through sight or hearing,
and ordinarily escapes by
flight or by jumping. They
sometimes escape by simply
dropping to the ground.
The grasshopper is largely
protected by his resem-
blance in color to that on
which he habitually rests,
some forms being usually
on plants, while those that
stay much of the time on
the ground are more of the
color of the soil. The posi-
tion while on plants, parallel
to the stem, makes them
less conspicuous than they
would be otherwise. Grass-
hoppers are often subject to injury by parasites, especiallv
certain red mites which are often to be found under th^

lO Descriptive Zoology.

bases of the wings. They are often destroyed in large
numbers by the growth of a parasitic fungus in their
bodies. Every boy knows that when the grasshopper is
captured he ejects from the mouth a dark Uquid secreted
by the crop. This is probably a means of defense.

Sounds made by Grasshoppers. — Sounds are produced
by the males only. Some grasshoppers make the noise
by rubbing the bases of the legs against the bases of the
outer wings. Others, while flying, rub the under surface
of the base of the outer wing over the upper surface of
the base of the inner wing. The katydids and crickets
make the sound, while at rest, by rubbing the wings against
each other.

Colors of the Grasshopper. — Although the grasshopper
is decidedly inconspicuous when at rest, on account of
the protective resemblance in color, yet it is to be ob-
served that in some species the inner wings are con-
spicuously colored, making the insect very noticeable
during flight.

Development of the Grasshopper. — The ovaries occupy
the upper part of the abdomen of the female. When full
of ripe eggs they take a good share of the space in the
abdomen. The oviducts extend down and back, opening
between the sharp points at the end of the abdomen. These
four sharp points together form the ovipositor. In lay-
ing the eggs the female presses the tips of the four
points close together, which makes a strong and fairly
good digging tool. This is thrust into the ground and
the points are then separated, and by repeating this a hole
is made, into which the eggs are introduced, passing out
between the guides. The egg hatches out into a little
grasshopper resembling the parent, but lacking wings.

Insecta.

II

After a time rudimentary wings appear. In all such cases
as this, where the young are hatched in essentially the same
form as the adult, the development is said to be direct.

Injury done by Grasshoppers. — Ancient history records
plagues of locusts. (The name "locust" is the proper one
for our common grasshopper.) And in modern times and
near-by places there have been migrations of locusts in
such numbers that they have darkened the sky, and, light-
ing everywhere, have devastated the land by eating almost

Fig. 6. Grasshopper laying Eggs.

From Hyatt's Insecta.

every leaf and tender stalk of grass, crops, and trees in
garden and field. The Rocky Mountain locust, migrat-
ing eastward, almost produced a famine in Kansas and
Nebraska, and created terror beyond the Hmits of its actual
ravages. But, fortunately, the young hatched in the lower
states are not healthy, and die prematurely ; hence the
plague has not spread so extensively as it threatened to do.
Packard says that the Rocky Mountain locust, within a
period of four years, inflicted a loss of ;^200,ooo,ooo on the
farmers of the West.

12

Descriptive Zoology.

ORDER ORTHOPTERA.

The Orthoptera. — We have selected the grasshopper as
the best available type of the class Insecta and also of the

order Orthoptera. The word
07'tJioptera means straight-
winged, probably in allusion to
the mode of folding the hind
wings. The first pair are thick-
ened, serving as a cover for the
second pair, which are folded
when at rest. The mouth parts
are fitted for biting. The de-
velopment is direct.

Protective Resemblance. —

The green grasshoppers, es-
pecially the katydid, are note-
worthy for their resemblance to
leaves, both in color and form.
The walking stick (Fig. 7) so
closely resembles a twig that
it is seldom discovered by
casual observers. These in-
sects afford fine examples of
the advantages of protective
resemblance.

The green grasshoppers have
a windowlike membrane on the
Fig. 7. A Walking Stick Insect tibia of each fore leg that is

{Diapheromerafemoraia) ON TwiG. g^pposcd tO be an Organ of
From Jordan and Kellogg's Animal Life. .

hearing.
Classification of Orthoptera. — The famihes are : the short-
horned grasshoppers (locusts), which we have studied;

Insecta. 13

the long-horned grasshoppers (usually green), including
the katydid; the crickets ; the cockroaches, including the
"croton bug," so common about water pipes; the walking
sticks ; and the mantids.

ORDER ODONATA.

The Dragon Fly. — The dragon fly has a long, straight
abdomen, and large eyes. The two pairs of net-veined
wings are alike in texture and nearly of the same size.
The wings are never folded, but when at rest are held out
at right angles to the body, ready for instant use. There
is a pair of strong jaws, which are nearly covered by the
large under and upper lips. The dragon fly feeds on in-
sects, which it catches on the wing, being one of the
swiftest and strongest flying of insects. Dragon flies are
most abundant in marshy places, where they may be seen
flying over the water or perched on a leaf or stem above
the water, on the alert for a passing mosquito or other
small insect. The females lay the eggs in the water, and
may often be seen hovering over the water with the tip of
the abdomen dipping beneath the surface. An egg hatches
into a form called a nymph, with strong jaws. It immedi-
ately begins to prey upon other insects and larvae that it
finds. When it has attained its growth it crawls up the
stalk of some water plant, splits along the back, and the
dragon fly emerges, leaving the empty skin still chnging
to the stalk. The development is here also called direct.
While living in water the larva breathes by taking water
into the hind part of the digestive tube. Other dragon fly
larvae have rudimentary gills. Some of the smaller dragon
flies, when at rest, place the wings close together, just above
the body. These are called dampel flies. Dragon flies are

H

Descriptive Zoology.

also called darning needles, devil's needles, snake feeders,
snake doctors, spindles, and mosquito hawks. In the

OI^^^j

Fig. 8. Dragon Fly and May Fly.

From Hyatt's Insecta.

Northern states children and ignorant adults believe that
these insects sew up people's ears, and in the South the

Insecta.

15

same classes think they bring dead snakes to Ufe. It is
easy to see how these stories arise. The long abdomen is
supposed to hold a correspondingly long sting ; while its
mode of laying eggs (people not knowing what it is doing)
gives it the name applied in the South. The name mos-
(^uito hawk is the most significant of its life and habits, for
it has no sting, and is entirely harmless ; but, on the other
hand, it benefits man by destroying mosquitos and other
insects.

Characteristics of Odonata. — The dragon flies represent
the order Odonata. The chief characteristics of the order
are : wings net-veined, the two pairs equal or nearly so ;
mouth parts fitted for biting ; abdomen long and slender ;
development direct.

COMPARISON OF GRASSHOPPER AND DRAGON FLY.

GRASSHOPPER. DRAGON FLY.

On land Home Over water

Plants Food. Insects

Numerous Enemies . Few

Strong — for jumping Legs . . Weak, merely for perching

Two pairs Wings, number Two pairs

First pair thick Wings, texture of ... . Both pairs gauzy

Fold close to body . ] Wings, position, f Extended at right angle

First pair covering 2d / resting i . . . . Not overlapping

Crawl through grass . 1 t> •.• 11 .[•••• Dart after insects

^. , , .• f Position enables to -^ ^^ 1 j

Elude observation . . J . I Exposure less dangerous

Adaptation to Mode of Life. — In addition to the above
tabular representation of some of the most striking differ-
ences between the grasshopper and dragon fly, let us
consider what characteristics each has that fit it for its
particular mode and place of life, and which unfit it for

1 6 Descriptive Zoology.

the mode of life of the other. Let us suppose that they
trade places. It is not unfair to make this supposition, for
they are not extremely unlike. Both have strong biting
jaws, two pairs of strong wings, and a long abdomen.

In the first place, let us suppose that the dragon fly can
subsist on vegetable food, and that it takes up its life as
a grasshopper. It finds its long, projecting wings in the
way. They not only hinder it as it attempts to crawl
into narrow places, but are apt to be torn, for, though
strong, their texture is delicate. So it will naturally turn
the wings back alongside of the body, and for compact-
ness will probably let one pair rest upon the other. It
will further protect them if the outer wings become harder
and tougher, but this change will be something of a
sacrifice in flying power.

Again, when the wings are thus folded, the insect covers
less area and is less conspicuous and therefore more likely
to elude the eyes of birds or other enemies. Its legs, which
are light and weak, having been used merely for support,
need greater strength to enable it to crawl and jump. The
eyes are not required to be so keen and naturally may
become smaller, and as it leads a lazier life it becomes
more corpulent and clumsy. To make up for the loss of
flying power in the front wings, the hinder ones become
wider ; this necessitates their being folded when at rest
in order that the narrower front wings may completely
cover them.

Let us now consider how the grasshopper would fare
in the endeavor to lead the life of the dragon fly. In the
first place, the grasshopper lacks the flying power requisite
to capture lively little insects on the wing It must have
both pairs of wings developed for active use; and it can
afford to do this, as it does not need to have the front pair

Insecta. 17

thickened, as in its situation covers are not needed. It
should have wings constantly poised, ready to dart in-
stantly after its prey. There is no objection to having the
wings continually spread, as it lives in open spaces and
does not have to crawl through grass and twigs ; and the
increased area due to the spread does not especially endan-
ger it by making it more conspicuous, since it has compara-
tively few enemies. The body is too heavy, and it must
" train down " until it can handle itself better. The legs
are too heavy, especially the hind pair ; and, as it uses them
very little except to perch upon a leaf or twig, waiting for
something to turn up, this matter takes care of itself, for
any unused organ is likely to dwindle away.

It needs keener eyes, for it no longer feeds on plants
which are sure to stay in place while it crawls upon them ;
it is another matter to discern small insects at some dis-
tance. So it develops better eye power to discover its food,
as well as better wing power to overtake it after seeing it.
It had fairly good jaws before, but they become some-
what enlarged and better adapted to the new work. The
enlargement of the jaws and the eyes make the whole
head bigger than it was before.

Of course insects do not trade places in this manner;
nor does any insect suddenly change its habits. But we
can easily imagine that these two forms have descended
from the same ancestors and have gradually grown dif-
erent, each becoming fitted for the situation in which it is
placed.

It is no longer supposed that all the forms of life we
now see on the earth have been distinct from the begin-
ning, for we see evidences that many forms have arisen
by the increase in numbers which establishes competition,
and which in turn . has compelled dispersion and forced

1 8 Descriptive Zoology.

adaptation to new surroundings and a gradual advance-
ment to changed conditions of life.

ORDER HEMIPTERA.

The Giant Water Bug. — This is the largest of the bugs,
being two and one half inches long. It lives in the water
of our lakes and rivers, but was not very generally known
until electric lights became common. The light attracts
them, and they are frequently found where they have fallen
under the lamps. Consequently many people call them.

Fig. 9. Giant Water Bug.

From Hyatt's Insecta.

the ** Electric Light Bugs." They are more abundant in
river towns that are lighted by electricity, and a good way to
collect them is to look for them under the lamps late in the
evening. By preserving them in alcohol enough may be ac-
cumulated to supply a class. They serve admirably to show
the chief characteristics of bugs, and are large enough to dis-
sect if the student wishes to learn the internal structure.

The head is relatively small and the neck is not con-
spicuous. The prothorax is large and broad. The outer
wings are narrow in front, being separated by a triangular
elevation of the mesothorax, called the scutellum. Then

Insecta. 1 9

for a short distance the two outer wings meet in the middle
line ; beyond this the wings are wider and overlap each
other. The hinder part of the wings is much thinner than
the front part. The inner wings are much thinner and are
folded. The mouth parts are united to form a strong pierc-
ing and sucking tube, which is bent back under the head,
between the bases of the front legs. The features thus far
described are common to nearly all bugs. But while the
majority of bugs live in the air, the water bug lives under
the water most of the time, though it can, and sometimes
does, come out and fly about. To fit it for swimming under
the water the body is flat and boat-shaped ; the second and
third pairs of legs are flattened, especially the tibia and
tarsus, making admirable paddles. The front legs are of
no use in swimming, but are used in grasping. The water
bug hides under leaves and sticks in the water, and when
an unwary insect, small fish, frog, or tadpole comes near,
darts out, seizes it with its powerful fore legs, and kills it by
piercing it with its sharp beak. It then sucks its blood,
having no jaws for chewing solid food.

The entomologists do not describe any poison glands
in these insects, but it would appear that they have a poison-
ous effect, since they seem to kill their victims so quickly ;
and since this and numerous other bugs, some aquatic and
some not aquatic, inflict painful wounds on man. In fact,
the collector who is gathering minnows in a net is often
bitten by aquatic bugs, and sometimes the hand and arm
become painfully swollen as a result.

Water bugs may be seen coming to the surface, where
they project the tip of the abdomen into the air. They
breathe through the anal pair of spiracles.

In attempting to spread the outer wing, one usually meets
difficulty, — the wing seems to be caught. There is an in-

20 Descriptive Zoology.

genious catch, consisting of a little projection or hook on
the side of the thorax, that catches into a groove in the
under surface of the front edge of the wing.

There are two forms of water bugs common. Bclostoma
americamim has a groove in the femur of each front leg,
into which the tibia shuts like a knife blade into a handle.
The other form, Be7iacus giiseiis, lacks this groove.

The Squash Bug. — Although smaller than the giant
water bug, the squash bug has the advantage of being
more abundant. If the former cannot be obtained, the
latter should be studied. Like the water bug, it has a
small head with a sharp beak, bent back under the head
and thorax. The outer wings, too, have a thickened base,
with the thin hind portions of the hind wings overlapping
each other. The thinner inner wings are folded lengthwise.
The legs are adapted to crawHng. The prothorax is large
and triangular. On the under surface of the thorax are
glands which secrete an ill-smelling liquid. This is a rather
common characteristic of Hemiptera, and brings the ''bugs"
into disrepute. This is a further reason why we should not
use the term "bug" indiscriminately for the term "insect."
It is incorrect, and as unfair as it would be to designate all
mankind by the name of one of the most disagreeable tribes
of savages that could be found.

As is well known, the squash bug lives upon plants, suck-
ing their juices through its strong, piercing beak, doing con-
siderable damage, especially to plants of the gourd family.
The eggs are laid on the under surface of the leaves about
the first of July, and in August the young may be seen
with the wings in all stages of development.

The Cicadas. — These insects are often improperly called
"locusts." Probably they are best known by the shrill

SQUASH BUG

Fig. io. Squash Bug, Structure and Development.

mi, antenna; la, labium; mx, maxilla; oc, simple eye; su, su';king tube
From Hyatt's Insecta.

22 Descriptive Zoology.

sound made by the males. Under the abdomen of the
males are two circular disks. Under these is the appa-
ratus by which the sound is produced.

Both pairs of wings are membranous, the hinder pair
being much the smaller. The larva is a grublike form
which lives under the ground, sucking the juices from the
roots of trees. When ready to appear in the upper world,
it crawls up the trunk ; and while it still cHngs to the bark
its back splits open, and the winged insect emerges, leaving

Fig. II. Cicada: Harvest Fly.

From Hyatt's Insecta.

the empty skin adhering by the claws. Here the shed skin
may remain for weeks, until washed off by the rain or
brushed off by a passing animal.

The dogday harvest fly (Fig. 1 1) has a very broad head
with eyes projecting at its angles, and is rather greenish.
His shrill sound is suggestive of the dry, hot, August mid-
day. The periodical cicada (the correct name for what is
usually called the "seventeen-year locust") spends from
thirteen years in the Southern form to seventeen in the
Northern in the larval state. This cicada is distinctly nar-
rower-headed than the summer cicada, and is darker in
color.

Insecta.

23

Order Hemiptera, — Among the many exceedingly interesting He-
miptera we may briefly mention the chinch bugs, so well and so unfavor-
ably known, and the plant lice, which are so common on many plants,
especially on house plants. Noticeable among the plant lice is the

Fig. 13. Plant Louse, Wing

Natural size. LESS LaRVAI. FfiMALE.

Fig. 12. Plant Louse, Adult Winged
Female.

From Hyatt's Insecta.

Ob maple

On osage orange

Fig. 14. Maple Scale Insect.

From Hyatt's Insecta.

•24 Descriptive Zoology.

grape phylloxera, so injurious to the grapevine. The scale bugs, or
bark lice, are very injurious to trees ; some of them are among the worst
pests of the fruit grower, and tax his utmost ingenuity to prevent their
spreading. The females are scalelike, and sometimes to be seen project-
ing from beneath the scale is the cottony egg cluster so frequently
observed on maples.

Two kinds of bugs are worthy of mention as useful to man, the
cochineal insect, furnishing a dye, and the lac insect, from which we get
shellac. Lastly we refer to the parasitic Hemiptera, such as the vari-
ous forms of lice, bedbugs, etc. Most of these forms are very degen-
erate in their structure, having lost their wings as a result of their
parasitic habits.

Characteristics of Hemiptera. — The mouth parts form a
piercing and sucking tube ; the prothorax is prominent ;
fore wings often thickened at the base; many are ill-smell-
ing ; development direct.

ORDER NEUROPTERA.

The order Neuroptera is a small order. The only ex-
ample here presented is the ant lion (Figs. 15 and 16).

eiQ. 15. Ant Lion, Adult. Fig. 16. Ant Lion, Larva,

From Hyatt's Insecia.

CHAPTER II.
BRANCH ARTHROPODA.

CLASS INSECTA {Continued).
Order Lepidoptera.

The Monarch, or Milkweed, Butterfly. — This common
butterfly is of a brown color, with black veins and wing
borders. There are about two rows of white spots in the
black border. This butterfly has a wing spread of about
four inches. The larva is greenish yellow, with distinct
bands of shiny black, and feeds on milkweeds. The chrys-
alid is suspended by the tip, as shown in Fig. 17.

One of the most noticeable features of the butterfly is
the presence of scales on the wings and body. The scales
are modified hairs, and on the body they are slender. The
scales shed water, strengthen the wing, and serve as an
ornament. The wings are large, and in flying act together
as one wing, the wing motion being slow.

Another distinctive character is the long coiled sucking
tube by which the butterfly sucks nectar from the flowers.
When not in use, this tube is coiled like a watch spring
and concealed between the labial palps. The sucking tube
consists of the two maxillae, much lengthened and each
grooved along its inner surface, so that when the two are
closely applied to each other they form a tube. The man-
dibles are but slightly developed.

In September or October great swarms of these butter-
flies may be seen, and this is a good time to collect them.

as

26

Descriptive Zoologyc

At night they settle on trees, hanging in great clusters
from the leaves. It is not easy to see them at such times.

Fig. 17. Structure and Development of the Monarch Buiterfly.

From Hyatt's lusecta.

They look like dead leaves. In the morning, when they
are chilled, they may be taken in a net.

Insecta.

27

The Cabbage Butterfly. — One of the easiest of the butter-
flies to capture and to rear in confinement is the cabbage
butterfly. It is white or slightly yellowish above and
yellowish below. Both sexes have black tips on the an-

FiG. 18. Cabbage Butterfly, Male.

Fig. 20. Cabbage Butterfly.

a, larva, i, pupa.

Fig. 19, Cabbage Butterfly, Female.

From Hyatt's Insecta.

Fig. 21. Cabbage Butterfly.

Pupa.

terior wings ; the male has a round black spot near the
outer border of each wing, while the female has two spots
on each anterior wing. In the early fall, watch the female
laying eggs on cabbage leaves ; gather some of the leaves
and watch the larvae come out of the eggs ; feed the larvae
till full grown ; keep the chrysalids till the butterfly ap-
pears. Describe all the changes and note the dates of all
the moltings and transformations.

28 Descriptive Zoology.

The Hawk Moth. — This moth is well known by its habit
of poising like a humming bird over the flower from which
it is extracting the nectar by means of its long sucking
tube. It is also called the humming miller, or humming
bird moth. The hawk moths have long, sharp-pointed
wings and strong powers of flight. Their larvae are usu-
ally large green "worms," one of the most common being
the so-called tomato worm. The pupa is often plowed up
in gardens, and is distinguished by the tongue case, which
is bent around to one side of the body, like a pitcher
handle. The hawk moths usually fly at twilight. The
hawk moths are also called sphinx moths, from the fact
that the larva often rests for a long time with the anterior
end held erect.

DIFFERENCES BETWEEN MOTHS AND BUTTERFLIES.

BUTTERFLIES.

MOTHS.

I.

2.
3.

Day-flying, usually.
Wings erect when resting.
Antennae knobbed.

I.

2.
3-

Night-flying, usually.
Wings sloping when resting.
Antennae not knobbed.

4-

Pupa a chrysalid.

4-

Pupa (often) in a cocoon.

Development of Lepidoptera. — The egg hatches into what
is commonly called a " worm." But no true worm has
jointed appendages, while in these larvae each of the first
three segments back of the head bears a pair of jointed
legs. These three segments become the three segments
of the thorax. In addition to these legs the caterpillar, as
it is usually called, has several pairs, commonly five, of
soft, fleshy legs on segments farther back, almost always a
pair on the last segment. These prolegs have a sort of
cleft at their ends by means of which they aid in crawling.
Some caterpillars are smooth, others are densely hairy.

Fig. 22. Hawk Moth or Sphinx Moth, Adult.

From Hyatt's Insecta. Larva of another species.

30 Descriptive Zoology.

The larvae eat voraciously and grow rapidly, molting sev-
eral times before reaching full size. When ready to trans-
form, the butterfly larva assumes a harder coat, commonly
ornamented with silvery or gold markings (hence such a
pupa is called a ** chrysaUd "), while the larva of the moth
may spin a cocoon of silk, adding to it the hairs from its
body, though some moths have a simple, dull-colored pupa
which is buried in the ground. The larva has a silk gland
which opens on the under lip, though many larvae spin
little or none, some making one or two loops to support
themselves when changed to chrysalids, alongside or under
some protecting cover, such as a limb, fence-board, etc. It
should be noted that the larvae have strong, laterally mov-
ing jaws, and eat greedily, subsisting on solid food, whereas
the adult is a dainty eater, and lives on liquid food, which
it takes through the sucking tube. It is common to speak
of the Lepidoptera as undergoing a " complete " meta-
morphosis, while the grasshopper is said to have an " in-
complete " metamorphosis. But as the development of the
locust is just as complete as that of the butterfly, we should
call the development of the grasshopper " direct," and that
of the butterfly " indirect."

Kinds of Lepidoptera. — The butterflies are generally most conspicu-
ous, as they fly in the daytime, but many of the moths are very beauti-
ful. One group of butterflies are called from the form of their wings
the swallow-tails. Though we associate the word " butterfly" with warm
weather and sunny days, one species, the White Mountain butterfly, is
found only high in the mountains, and the writer has been delightfully
surprised to find these beautiful creatures above "timber line," near
snowbanks, on the chilly mountain tops.

Perhaps most noted among the moths is the silkworm, a native of
China. But we have a number of native American silkworm moths ;
of these the Cecropia and Polyphemus are perhaps best known. The
larva of the codling moth is often found in apples. There is a large

Insecta.

3»

number of related moths whose larvae roll leaves, and are knovv^n as
"leaf rollers." The *' measuring worms" are larvse of moths. Last,
but not least in importance, is the clothes moth, which departs from the
usual custom of living on vegetable food.

Mimicry. — The viceroy butterfly, which is sometimes
eaten by birds, is protected by its resemblance to the ined-
ible monarch butterfly. This is a case of mimicry.

Fig. 25. The Monarch BurrERFLY.

Fig. 26. The Viceroy Butterfly, which mimics the Monarch.

From Kellogg's Zoology.

General Characters of Lepidoptera. — The moths and
butterflies have two pairs of scaly wings, which are large
and slow in motion. The parts of the body are distinct.

32 Descriptive Zoology.

The long, coiled sucking tube, composed of the two max-
illae, is a noticeable feature. The legs are small and weak,
some forms having but two pairs, others having the anterior
pair but not using them.

ORDER DIPTERA.

The House Fly. — The house fly has but one pair of
developed wings, the second pair being represented by a
pair of bodies resembling pins, that is, consisting of a
threadhke stalk with a knob at the end. They are called
balancers ; their function is supposed to be sensory. When
the fly is at rest the wings are extended backward and
held horizontally over the back, lapping over each other at
the inner borders, but are not folded, in the strict sense of
that term ; that is, are not thrown into folds, as are the
inner wings of the grasshopper.

The mandibles and maxillae are rudimentary, and the
proboscis is composed mainly of the labial palps, which
are developed into broad plates, which are thus adapted
not only for lapping but also for rasping. They cannot
bite, though they often light on the human skin to lap up
the perspiration.

The wing movements are very rapid, making as many as
330 vibrations in a second. The sound produced by flies
is mainly made by the vibrations of the wings ; but when
the fly is held by the wings, there is still heard a faint
buzzing noise, and this is supposed to be due to the pas-
sage of air through the spiracles.

Development of the House Fly. — House flies lay their
eggs in stable manure, each female laying about 150 eggs.
In favorable weather, the eggs hatch in about one day.

Horse fly

older

o:irTubes

Fig. 27. Horse Fly, Structure and Development.

a/, antenna; /a, labium; md, mandMc; mx, maxilla. — From Hyatt's /nsecia.

34 Descriptive Zoology.

The legless larva is called a maggot. After living in this
state about a week, it becomes a pupa, remaining in its old
larval skin, which is called a puparium. (See Fig. 27.) In
a week more it emerges as a fly. There may be, therefore,
ten or a dozen generations in a single summer. A small
number live over winter, hiding in crevices in walls and
similar places. House flies are worse than mere nuisances,
they are spreaders of disease. On the other hand they
do much good as scavengers.

How Flies Crawl. — The fly has many little hairlike pro-
jections on its feet. These secrete a sticky substance from
their ends, by means of which the fly adheres to smooth
walls and ceilings.

Other Kinds of Flies. — The stable flies closely resemble the house
flies, but have a sharp, piercing sucking tube. They sometimes And
their way into houses, especially on warm, rainy days in the fall. On

the other hand many of the flies
seen about stables are house flies.
The horseflies are well known,
the most common being known as
the "greenhead"; a still larger
form is dull black, and in the West
is called " t»undog," from its size
and persistency ; still smaller than
either are those with banded wings,
and these usually have the wings
spread wider so that the fly looks
FIG. 28. THE BEE KILLER. triangular; some of these are called

rr , r u 'Meer flies. ''^ It is a surprise to find

1* rom Hyatt s Insecta. _ ^

• the big black horseflies abundant
and annoying in the cold air of the high tops of the Rocky Mountains.
Among the forms that annoy man and beast are the black flies, or
midges, often swarming in the Adirondacks. On account of their
smallness the Indians call them "no-see-ems." To guard himself
against these pests the hunter and the fisher often anoint the face
and the hands with a mixture of tar and oil of pennyroyal.

Insecta. 3j

Every one has noticed the big fly that occasionally is found in houses,
as it attracts attention by its loud buzzing and its bluish abdomen.
It is the blowfly, that lays its eggs on meat. It is a disgusting sight
to behold flesh ^' alive with maggots," but when one reflects he sees

Breathing tubes

Pupa. Larva.

Fig. 29. Development of the Mosquito.

what a wise provision of nature it is that such decaying matter should
be so promptly and effectually disposed of. Let the hunter sit down
to eat his lunch of biscuit and meat in any part of the Rocky Moun-
tains, and the chances are that before he has finished the blowflies will
have discovered the presence of flesh, and come buzzing around him.

The botfly lays its eggs on the hairs of horses' fore legs and shoul-
ders. The horse gets them into the mouth from scratching itself by
biting, and swallows thern. The larva attaches itself by means of hooks
to the inner wall of the stomach. Later it passes on through the intes-
tine, and the pupa completes its development in the dung.

" Skippers " are the larvae of black flies, about half the size of the
house fly, that lay their eggs on cheese, ham, and bacon. Bills received
from packing houses often specify that they do not guarantee their goods
against skippers.

There are also flies that injure plants. Among these the Hessian fly
is well known. The larva is to be found between the sheath of a blade
of wheat and the stalk, where it does its damage. There is also a
" wheat midge " which causes considerable loss. Nearly every one must
have noticed on the ends of willow twigs a gray cone-shaped growth.
This is caused by the developing larva of the "pine cone" gall gnat.

The Mosquito. — The mosquito lays its eggs on stagnant water. The
larvae are known as " wrigglers," and their well-known habits justify the

^6 Descriptive Zoology.

name. The larva breathes by a tube at the hinder end of the body.
The pupa is also active ; it breathes air through two tubes which grow
out of the thorax. The piercing and sucking tube of the adult consists
of several mouthpieces which fit snugly together. Only the female bites.
She is a cheerful individual, singing as she goes about her work. Some
excellent authorities believe that mosquitoes are the chief agents in intro-
ducing the germs of malaria into the human system. Pouring kerosene
on the water in which mosquitoes are breeding will kill them, and this
is probably a more practical method of reducing their number than might
be at first supposed, for kerosene, like any other oily substance when on
water, spreads out in an exceedingly thin film, a little of it going a long
way.

Diptera. — This order of insects receives its name from
the fact that its members have but two wings, as seen in
the flies and mosquitoes. The life history of the house fly
is fairly typical. The knobbed balancers (rudimentary
hinder wings) are called **halteres."

ORDER COLEOPTERA.

The May Beetle. — This brown fellow is well known, but
more commonly under the incorrect name ''June bug."
You will hardly need to hunt for a specimen, for if you
leave your window open as you sit by your lamp on an
evening in May or June, he will come to you. Instead of
picking him up and throwing him out of the window, as you
have been in the habit of doing, lay down your book and
study him, for he will teach you more about himself than
you could possibly learn from any book in the same length
of time. At his best he is a poor flier, and, bewildered by
the glare of light, he is more clumsy than ever ; if he bumps
against the lamp and falls upon the table, you will have a
good look at him. Note the order in which the legs are
moved in crawling. Try to pick him up and find how he

eintennoi
mandible^
maxilla c^

head

r\5.y- beetle

m eta-thoraxL f ro-m [ront '^■

Fig. 30. The May Beetle, Structure and Development.

From Hyatt's Insectm..

38 Descriptive Zoology.

holds on so well. Observe another one flying, — see how
he holds the wing covers up and out at the sides. As soon
as he lights, see how these wing covers come down over
the membranous flying wings, which at first project behind
the wing. Watch him tuck the wings under the wing covers ;
can you tell how he does it ? After the membranous wings
have been withdrawn from sight, pick him up and note
that the wing covers meet in a straight line along the
middle of the back, entirely concealing the true wings.
Note also the large prothorax. The head is small, but has
strong mandibles and two pairs of maxillae. The enlarged
ends of the antennae consist of a series of leaflike plates,
giving the name to a large group, — the LamelHcorn
beetles. Watch him as he starts to fly again. In order
to give the flying wings free play, the wing covers must be
held well up a^d forward. In this position they make con-
siderable resistance to flight, and it is easy to see that this
kind of insect cannot be a first-class flier.

These beetles sometimes do considerable damage, by
eating the leaves, especially of the cherry. In the early
evening one may see swarms of May beetles and later hear
them buzzing about the foliage.

The eggs are laid in the ground and hatch out into
white "grubs." Every boy knows them well and uses
them for bait, and often he learns that the blackbirds
know enough to follow the plow and pick up the grubs
that are left in the furrow. The grub usually has a dark
head, with a white body, the first three segments bearing
each a pair of jointed legs that correspond to the three
pairs of legs of the adult beetle. The hinder part of the
body is often dark from the dirt that has been eaten.
Every one knows how they lie curled up and in the ground ;
they generally rest on their backs. They often do great

Insecta.

39

injury by eating the roots of grasses, strawberry plants,
corn, grain, and other plants. The larva lives in the ground

Fig. 31. The Colorado Potato Beetle and its Development.

<*» eggs; b, larvae; c, pupa (underground) ; d, adult; e, wing cover; f, leg.
From Hyatt's Insecta.

two or three years. The last of its stay is passed in a
pupa state, when it is inactive, lying in a smooth, oval

cavity it has made for itself.

The Colorado Potato Beetle. — This is
too well known to need description. It is
a native of the Rocky Mountain region,
where it lived on a species of Solanum (to
which genus the potato belongs) ; when
the potato began to be cultivated near its
home, the beetle transferred to the new
plant, and, starting in 1859, it spread east-
ward till it reached the Atlantic coast in
1874.

The Ground Beetles. — Among the most
common of our beetles are the ground
beetles, to be found under logs, boards, and stones, or running about on

Fig. 32. Common Ground
Beetle.

From Hyatt's Insecta.

40 Descriptive Zoology.

the ground in the summer and fall. The caterpillar hunter has green
wing covers and is over an inch long. The fiery hunter has on the
wing covers rows of red or copper-colored spots.

The Tiger Beetles*. — These beetles get the name from their active
predaceous habits, as well as from their bright-colored and yellow-barred
wing covers. They run actively and fly well for beetles. They are
often to be seen on the ground, especially on sand along streams. When
you attempt to capture one it may remain quiet till you get near it,
when it darts away, flying a short distance, and usually lights with its
head toward you.

The Borers. — There are many beetles whose larvae bore into trees,
where they do great damage. Among these, perhaps the locust borer

Fig. 33. Hickory Tree Borer; Larva, Pupa, and Adult.

From Hyatt's lusecta.

and the painted hickory borer are found as frequently as any. The
woodpeckers do good service in destroying these grubs.

The Stag Beetles. — Many children know these beetles as "pinch
bugs." The large, incurved mandibles are very characteristic. The
larvae usually live in decaying wood.

The Dung Beetles. — No boy or girl who has spent much time in the
country has missed seeing these odd beetles, called " tumble-bugs."
On the way to and from the district school the child meets the pai^s
of beetles rolling the big ball that they have made from the drop-
pings of horses and cattle. It is interesting to see them, one pushing
and one pu/ling ; as he patiently follows and watches them, he sees
them at last bury the ball. Later the child learns that the female lays
eggs in the ball, which the larvae consume as food.

The "Weevils." — Some of these are small beetles, not more than
one fifth of an inch long. They lay their eggs on the pea pods ; the

Insecta. 41

larvae bore their way into the pea, and eat out to the skin through
which the adult easily makes his way when ready to emerge.

Blister Beetles. — A large family of beetles has a blistering substance
which is used in making blistering plasters. The " Spanish fly " be-
longs to this group. One of the most common of our blister beetles is
a black fellow abundant on goldenrod flowers.

Carrion Beetles. — These usually have club-shaped antennae. The^
are well known, as both the larvae and the adults feed on decaying
flesh. Some of these beetles are called "sexton beetles" from the fact
that they bury small animals.

The Rove Beetles. — These are odd forms, with short wing covers,
which hardly conceal half of the abdomen. This is long and flexible,
and is often carried turned up as if threatening to sting, which it has no
power to do.

The Ladybugs. — All children who live in the country know these
hemispherical beetles, with their smooth and often brightly colored and
spotted backs. Most of them are predaceous, and one of the greatest
triumphs of economic entomology was the introduction of a species of
ladybug from Australia into California, where it largely checked the
ravages of a scale insect, which was making havoc with the fruit trees.

The Carpet Beetles. — Some of these destroy carpets. Others are
the greatest pests of museums, destroying the stuffed specimens. The
best remedy is bisulphide of carbon, whose fumes are fatal to eggs,
larvae, and adults.

The Click Beetles. — Boys know them as '"'spring beetles," "snap-
ping bugs," "skipjacks," etc. Lay one on its back, and soon it gives a
spring, with a click, that raises it perhaps several inches. If it lights
on its back, it soon tries again. These beetles, like many others, " play
'possum." Their larvae are " wire worms," and do great damage, eat-
ing the roots of corn, grain, grasses, and other plants. One of our
largest click beetles, the eyed elater, is gray, and has on the prothorax
^'Wo large black spots resembling eyes.

The Snout Beetles. — These beetles (the true weevils) are very odd
in having the head prolonged into a long beak, sometimes longer than
the body. Most of these are known as curculios. They bore a hole
with the end of the snout, deposit the egg, and then push the egg to
the bottom of the hole with the snout. They destroy many fruits and
nuts.

42 Descriptive Zoology.

The Fireflies. — These, too, are beetles. Children do not need to
be told that they emit light, and the most learned scientist cannot tell
just how the light is produced. The females of some fireflies are wing-
less, and are called " glowworms."

Water Beetles. — Not least interesting among beetles are the water
beetles. We shall notice three kinds. First, the whirligig beetles,
which nearly everybody has observed on the surface of the water, whirl-
ing round and round in swarms. Like the other water beetles, they
have a flattened body, and the hinder legs are paddle-shaped. The
whirligig beetles occasionally dive. They have each eye divided into
two parts, one of which looks up and the other down, so that one would
say they had two pairs of eyes.

The predaceous diving beetles have oval bodies, somewhat wider
behind. They are more abundant in stagnant water. When at rest
they come to the surface and remain with the head down and the tip of
the abdomen projecting into the air. Like the water bugs, they breathe
by taking air under the wings, and when a new supply is needed they
again come to the surface. The spiracles are on the upper surface of
the abdomen. They are very voracious, and eat other insects and even
small fishes. The larvae are spindle-shaped, with sharp, incurved
mandibles, and are known as " water tigers " on account of their fierce-
ness. Both larvae and adults may be kept and fed on meat.

The water scavenger beetles are elliptical. They do not breathe as
do the predaceous water beetles, but come to the surface head up and
take air under the body, where it is carried as a film, which gives a sil-
very gleam when seen from beneath. They are supposed to feed mainly
on decaying vegetable matter, but some are known to catch live insects
and eat them. They may be distinguished from the predaceous water
beetles by their shape, and by a long, sharp spine that projects back-
ward from the under surface of the thorax. Catch one of these beetles
by one of the hind legs and you will probably find out the use of this
spine. Though all these beetles have the power of flight, they do not
usually try to escape from a jar of water. It is easy to catch them by
scooping in ponds with a dip net. They may be kept in glass jars
(candy jars are very convenient), and watched from below as well as
from above. If they have no solid surface on which to crawl, they are
not likely to get away. It would seem that they cannot start to fly
from the surface of the water, but must have some solid object froro
which to rise into the air.

Insecta. 43

Coleoptera. — The beetles are called Coleoptera, mean-
ing sheath-winged, from the hard, horny wing covers.
The hind wings are membranous, and are usually consid-
erably longer than the wing covers. To enable the beetle
to protect them there is a joint in the anterior edge of the
wing so that it can be folded crosswise as well as length-
wise. This is accomplished by moving the abdomen down-
ward and backward, then upward and forward to draw the
wing under the covers. Some beetles lack true wings and
are unable to fly. The mouth parts are fitted for biting.

All insects have chitin in the skin to stiffen it, but the
beetles have this most fully developed, and are the hardest
and firmest bodied of insects. This is in keeping with their
mode of life, as many of them crawl into crevices, under
stones, logs, etc. They are the strongest of insects, and
the load they can carry, in proportion to their weight, is
marvelous. Beetles have compound eyes, but almost always
lack the simple eyes that are present in most insects.

As the under surface of the abdomen is subject to fre-
quent pressure, it needs to be hard and unyielding. How,
then, can respiration be effected.? It is secured by having
the upper surface of the abdomen more soft and flexible ;
by the in-and-out movement of this region the air is taken in
and sent out through the spiracles, which, except in water
beetles, may usually be seen along the abdomen.

In a former chapter we saw how the dragon fly would
have to change if he were to assume the life of a locust.
Go a step farther and it will be evident that the beetle,
forcing his way into crevices and into narrow places, has
acquired the hard, smooth body which he requires to fit
him for such a life.

There is great variety in the habits of beetles ; they live
in air and in water; are carnivorous and herbivorous; some

44 Descriptive Zoology.

are parasitic ; the larvae are found in the earth, in decay-
ing wood, in the living wood of hard trees, in manure, in
carrion, in fruits and seeds.

Many are injurious; others are beneficial, as the lady-
bugs, which destroy injurious insects.

ORDER HYMENOPTERA.

The Honeybee. — Our honeybee is of European origin,
and has long been domesticated. Occasionally escaped
swarms live in a wild state. The three parts of the body,
namely, head, thorax, and abdomen, are very distinct;
but it should be noticed that the prothorax, instead of
being immovably connected with the rest of the thorax, as
in the fly and many other insects, is movable. Another
feature, peculiar among insects, is the transferring of one
segment from the abdomen to the thorax, — what appears
to be the last segment of the thorax being really the fore-
most segment of the abdomen. The second segment of
the abdomen (apparently the first) is slender, and allows
the abdomen to be bent sharply forward under the thorax ;
and nearly every one has learned, in a way that he will not
forget, how and why the bee does this.

The two pairs of wings are membranous, the hind pair
being much smaller than the anterior. Along the front
margin of the hind wings is a row of hooks which catch on
a ridge at the hind edge of the front wings, so that in flight
the two wings work as one, — in fact until the wings are
unhooked there seems to be but one pair.

The mouth parts are peculiar. In most insects the mouth
parts are fitted either for biting or for sucking. In the bee
we find both sorts of structures. Mandibles are present,
and sometimes are strongly developed. But the food of

sifTfple e;yes "^

Fig. 34. The Honeybee, Structure and Development.

From Hyatt's Insecta.

46 Descriptive Zoology.

the honeybee is liquid, and the tongue is the conspicuous
organ. The two maxillae, with the two labial palps, form
the sucking tube, within which the cyHndrical tongue moves
up and down.

The antennae are like an arm bent at right angles at the
elbow. The pollen " basket " (see Fig. 34) is on the out-
side of the tibia of the hind legs of the workers, and is
simply a flattened segment surrounded by stiff hairs. The
sting is a modified ovipositor, consisting of several pieces
closely fitting together, constituting a tube, through which
the poison is conveyed from the poison gland within the tip
of the abdomen.

Fig. 35. Honeybee.

a, drone or male; 6, worker or infertile female; c, queen or fertile female.
From Jordan and Kellogg's Animal Life.

Kinds of Bees in a Hive. — There are three forms of
honeybees, — the queen or female, the drones or males,
and the workers, which are undeveloped females. There
is but one queen in a hive most of the time, and compara-
tively few drones, the great majority being workers. The
average hive consists of from twenty-five thousand to thirty-
five thousand bees, but there may be as many as fifty thou-
sand. The drones have broad, blunt bodies, and have no
stings; and may be further distinguished by their large
eyes, which make up most of the head. They may be found
in the hive in the early sumnqer, but after the swarming

Insecta. 47

season is over they are driven out or killed by the workers.
The workers are the smallest of the three kinds, and are
provided with "pollen baskets" and stings. The queen is
larger than the workers, and has a long, pointed abdomen.
She has a sting, but never uses it except against a rival
queen. The average life of a worker is about five weeks.
Workers may live eight months, while a queen has been
known to live five years.

The Work of the Hive. — As indicated in the name, the
management of the hive falls chiefly on the workers. In the
first place, the workers make_liQii£y. They gather nectar
from flowers ; this is taken into the honey stomach, but
not mainly for the sustenance of the worker. It is trans-
ferred to the cells, loses some water by evaporation, and
becomes honey. The workers make the wax from which
the comb is made. The wax is a secretion from the glands
on the under surface of the abdomen. When wax is needed
a large number of workers gorge themselves with honey
and hang like a curtain, clinging to each other, remaining
quiet. As the wax exudes from the glands, other workers
gather it and construct the comb. The economy of mate-
rial is well known, but the cells are not always mathemati-
cally exact, as is commonly supposed.

The workers also collect a gummy substance from buds,
which forms propolis, or "bee glue," with which they
cement crevices and make similar repairs. Pollen is also
gathered in a " basket " on each hind tibia. Of this pollen
"bee bread " is made for feeding the young.

Development. — For the rearing of the young special
cells are made which constitute the "brood comb." This
brood comb may be afterward used for storing honey. The
queen deposits an egg at the bottom of each cell, and after
they hatch, the larvae are fed by the workers till ready to

48

Descriptive Zoology.

Larv

Pupae

go into the pupa state, when the cell is capped over till
the pupae transforn^ into adult (or imago) bees.

The drones, being larger than the workers, are developed
in larger cells. Queen cells are larger than other cells.
At the season of the year when the bees give regular

attention to rearing queens,
the queen cells are usually
built at the bottom or ends
of the comb. But if the
bees are obliged to produce
a queen out of the regular
swarming season, the queen
cells are made by tearing
out the partitions and com-
bining three cells into one,
which is built out and hangs
vertically in front of the
comb. In the egg state
there is no difference be-
tween the queen and the
worker, but the larva that
is to become a queen is fed
on specially prepared food. In the, early part of the sum-
mer several queen cells are made ; as soon as a new queen
is hatched the old queen tries to kill her ; but the workers
protect the new queen, and the old queen, followed by a
part of the workers, departs to estabhsh a new colony, and
this is called *' swarming." If a number of new queens are
hatched at the same time, they may fight for leadership,
and the one survivor rules supreme. Or, often, several
young queens depart with a swarm.

The queens that are thus killed are carried out by the
workers, and they do the same for any that die in the hive

ueen
cell

Fig. 36. Celi^ containing Eggs, Lar-
v^, and pupm of the honeybee.

The large, irregular cells are queen cells. — From
Jordan and Kellogg's Animal Life.

Insecta. 49

All dirt and rubbish are carefully removed, the hive being
a model of neatness.

In warm weather a number of workers may be observed
stationed at the entrance, fanning vigorously with their
wings ; they do this to vQniilatejthe, hive.

Bumblebees. — The queen is the only one of a colony that lives
over the winter. Selecting some convenient place for a nest, usually an
old nest of a field mouse, she gathers a mass of pollen and lays some
eggs upon it. As the eggs hatch out the larvae eat into the pollen, and
when fully developed spin silken cocoons for themselves. After these
cocoons have served as cradles they are strengthened with wax and
used for storing honey. Every country boy has robbed the ne.sts of the
bumblebee ; he likes the honey and is willing to pay the price for it.
Nearly the whole colony of bumblebees may be captured by pouring
water into the nest, which renders them unable to fly ; or if a jug partly
filled with water be set near the nest, when they are disturbed they
usually enter the jug, and, getting into the water, are easily taken ; or
the whole colony may be chloroformed. Being larger than the honey-
bee, they offer some advantages for study.

Other Bees. — The honeybees and bumblebees are called social bees
in distinction from other kinds of bees that lead a solitary life. Among
the solitary bees is the carpenter bee, that tunnels into wood, sometimes
a foot or more. Some bees cut. out circular pieces of leaves with which
to line their holes. Others dig holes in the ground ; some mine into
the sides of banks, one group of the mining bees being called the
" short-tongued " bees. There are also several parasitic bees.

Wasps. — As with the bees, some of the wasps are social, while
others are solitary. In colonies there are three kinds of individuals,
males, females, and workers, all winged. The wings, unlike those of
bees, are folded into plaits, as in a fan. They build nests either in the
ground or on trees and buildings. Nearly everybody has seen the
large nests suspended from trees, about the size and shape of a football ;
and perhaps many have vivid recollections of the warm reception they
received when they knocked abruptly at the door of this lively commu-
nity. The hornet, or yellow jacket, need not be described to a country
lad. "Eternal enmity" is sworn between them, and each knows there
is no use of showing a white flag. Still, the skillful teacher may capture

50 Descriptive Zoology.

the entire colony by quietly slipping an insect net over the nest and
tying the net to inclose them. Later a hole may be made in the tip of
the net, and a single hornet at a time may be allowed to pass under a
tumbler inverted on a plate. After being kept awhile they will be
hungry, and if a drop of sugar water be introduced, the proud captive
will not hesitate to let his enemies see how he eats. The entrance to
these nests is below, while within are horizontal combs. The wasps
make the nests out of wood fibers, which they tear off stumps, fences,
and unpainted buildings. They chew these fibers into a pulp and make
a coarse gray paper. They probably are the original paper makers.

Another wasp builds a single layer of comb, which is held horizon-
tally under some protecting object by a narrow stalk, the comb not
being surrounded by a case as with the yellow jackets. The wasps
that make nests in the ground also make paper to line the nest.

Among the solitary wasps some are diggers, and it is interesting to
see one of them digging a hole, throwing the dirt back as it digs very
much as a dog does. Others make tunnels into the stems of plants,
where the young are reared.

The mud dauber wasps are slender-waisted, and wear a suit of shiny
dark blue. They have the habit of nervously jerking their wings.
They are often seen lighting on the mud about horse troughs, where
they are gathering mud for their nests. They make a nest of several
cells, in which the eggs are deposited. We see these cells on rafters,
under eaves, etc.

Some wasps store the cells with spiders and insects for the larva to
feed on till it emerges. Often the insect is stung so as to paralyze, but
not quite kill it.

Ants. — Here, again, we have a communistic society with perhaps a
still more perfect division of labor. The males and females at first
have wings, but the males are short-lived, and the females soon bite off
their wings. The work is done by the workers, who are wingless.
Some make a nest in the ground, while others tunnel into decaying
wood. In a disturbed nest we sometimes see the workers carrying
eggs. The large white objects which they carry are cocoons. Ants are
very strong for their size and do a variety of work. They care for the
larvae, protect the nest from invasion by enemies ; some species make
slaves (and it is interesting to note that the masters are light-colored
and the slaves dark). They keep cows (aphides) from which they get
a sweet liquid (honeydew), and some build a covar for their herds

Insecta. 51

(cow sheds). In some forms the masters are so dependent upon their
slaves that they perish unless cared for by them. Some of the ants that
keep the plant lice as cows are injurious through the action of the plant
lice, which feed on the roots of corn and other plants. The ants carry
the plant lice, or their eggs, into holes in the ground where they survive
the winter, which they probably would not otherwise be able to do.
Yellow ants often invade houses, making a nest within a wall where it
is almost impossible to dislodge them; these are often called "red
ants." Though fond of sweets, ants are almost omnivorous.

Other Hymenoptera. — Among the other Hymenoptera we may notice
the sawflies whose leaf-eating larvae are known as the rose slug, pear
tree slug, currant worm, etc. Various forms of Hymenoptera sting their
eggs into the stems and leaves of plants. Around the egg is formed a

Fig. 37. Larva of a Hawk Moth, with Cocoons of a Parasitic Ich-
neumon Fly.

From Kellogg's Zoology.

swelling known as a gall In this the larva develops, finally eating its
way out. There are many kinds of galls, and the entomologist knows
the kind of insect from the characteristic form of the gall, and the adult
insects are known as "gallflies."

The ichneumon flies have an ovipositor consisting of long, slender
(usually three) threads, by means of which the eggs are deposited,
usually in the trunks of trees, where these larvae prey on the larvae of
other boring insects.

In the fall one occasionally sees a sluggish caterpillar covered with
little oval bodies resembling eggs ; examined more closely, these little
bodies are £:een to have a silky finish ; they are the cocoons cf a para«

52 Descriptive Zoology.

site. A group of parasitic Hymenoptera (the Braconids) deposit their
eggs on the caterpillar; the little larvae bore their way into the big
larvae, and after consuming the tissues of the caterpillar, eat their way
out and add insult to injury, attaching their cocoons to the outside of
the skin. Sometimes the chrysahd of a cabbage butterfly fails to trans-
form, and a hole may be discovered where the adult " Braconids " have
made their escape.

Characteristics of Hymenoptera. — The Hymenoptera
have two pairs of membranous wings, the hind pair being
smaller than the front. The mouth parts are fitted both
for biting and for sucking. The female usually has a
sharp ovipositor, which in many cases is used simply as a
sting. Development indirect.

General Characteristics of Insects. — i. Insects have a
segmented external skeleton, i.e. consisting of a series of
rings. 2. These rings are grouped in three sets, head,
thorax, and abdomen. The head bears one pair of an-
tennae. The thorax bears three pairs of legs and usually
two pairs of wings. The abdomen does not usually have
jointed appendages. 3. Insects have air tubes, branching
through the thorax and abdomen, by which they breathe.

Harm done by Insects. — i. They destroy crops, and the
damage to our field and garden produce is almost beyond
computation. 2. They convey disease both by getting on
diseased matter and conveying it to our food, and also by
introducing disease germs in biting (mosquito). 3. They
injure stock (flies, mosquitoes, botflies, etc.). 4. They
injure buildings (ants and white ants). 5. They are often
annoying, when not injurious, to man.

Good done by Insects. — They benefit us (i) by making
silk; (2) by making honey; (3) by furnishing material
for making ink (galls); (4) furnish dyestuff (cochineal);
(5) they are used in medicine (blister beetles); (6) their use

Insecta. 53

in fertilizing flowers is unknown to many, but is essential
to man in certain crops ; (7) they serve as scavengers (flies,
beetles, maggots, etc.); (8) many kinds are very useful in
killing injurious insects, as ichneumon flies that destroy
borers, ladybugs that eat scale insects, etc.

On the whole it would be difficult for a jury to say
whether insects do more harm than good ; and it is per-
haps best to regard them as having their place in the
world to fill. And yet we must not submit tamely to their
ravages, for we may outwit the robbers and turn other
robbers against them. We should make it a study to turn
insects, as well as other groups of animals, to the best
account, and thus make the lower forms of animal life
serve man, who is deservedly at the head of creation so
long as he shows his fitness to rule.

ORDERS OF INSECTS.

Thysanura — Springtails. Neuroptera — Ant Lions.

Odonata — Dragon Flies. Lepidoptera — ButterflieSo

Orthoptera — Locusts . Diplera — Flies.

Hemiptera — Bugs . Coleoptera — BeetleSo

Hymenoptera — Bees.

CHAPTER III.
BRANCH ARTHROPODA.

CLASS MYRIAPODA.

Myriapoda. — The myriapods (''thousand legs" and cen-
tipeds) have a wormlike form, but, like other Arthropods,
have a more or less hardened external skeleton, and possess
jointed appendages. The head is distinct, but after it the
segments are ahke, there being no distinction of thorax
and abdomen. On the sides or ventral surface of most of
the segments are the spiracles or breathing pores, which
lead to the air tubes, or tracheae, as in the insects.

u^

rrnrn

Fig. 38. Centiped.

The head, as in insects, appears to be composed of sev-
eral segments, fused together; it bears a pair of many-
jointed antennae, a pair of eyes, and two or three pairs
of jaws.

There are two principal groups, the centipeds and the
milHpeds. The centipeds have flattened bodies, with one
pair of legs to each segment. They are carnivorous, and
have a poison gland opening at the tips of the first pair of
legs, which act with the mouth parts. The millipeds, or
thousand legs, have cylindrical bodies, and may be recog

54

Myriapoda. 55

nized by their habit of coiling into a spiral when disturbed ;
they have two pairs of legs to each segment. They are
vegetarian and not poisonous.

Fig. 39. Skein Centiped.

Both of these forms are usually to be found by over-
turning stones and logs ; the centipeds seek safety by run-
ning briskly away, while the millipeds coil up and He still.

CLASS ARACHNIDA.

The Spiders. — The body of a spider consists of two
parts, connected by a constricted waist, the unsegmented
cephalothorax and a large, soft, unsegmented abdomen.
There are six pairs of appendages : first, the jaws, each
jaw ending in a sharp, incurved segment at whose apex
opens the duct of a poison gland ; second, the palps, which
are sometimes mistaken for a pair of legs ; and lastly, four
pairs of legs.

Spiders have from one to four pairs of simple eyes vari-
ously arranged on the top or front of the head. Spi-
ders have a well-developed sense of sight, and their sense
of touch is very delicate. Of their other senses little is
known.

56

Descriptive Zoology.

Fig. 40. Jumping
Spider.

They suck the blood of insects, which they kill by means
of the poison introduced through the biting jaws. Their
bite is seldom serious to man, though one of the larger
spiders is said to kill small birds. There
is a strong sucking stomach which is
worked by special muscles.

In addition to breathing by air tubes,
as in the case of insects, spiders also have
what are called lungs, or, from their
peculiar structure, "lung books." The
openings to these lungs are under the
abdomen. The cavity to which the
opening leads is somewhat like the inside
of a pocketbook, with a number of com-
partments. Blood flows around the out-
side of this lung book, and within the
plates or leaves of the "book." Thus the blood and the
air come near each other, separated only by a thin mem-
brane, and by the folding an increase of surface is secured.
This is the same general plan of all lungs and gills, but
the details of the plan are carried out in various ways.

Like crustaceans, spiders molt, and one may often find
their cast skins, looking like dead spiders, but closer exami-
nation will reveal the difference.

Spinning. — One of the most interesting of the habits of
spiders is their web making. There is a great difference
among spiders in this regard. Some spiders spin very
little, leading a wandering life. Among these are the
"jumping spiders," so named from their habit of creeping
stealthily close to their victims, and then suddenly pounc-
ing upon them. These forms are common, and their
habits are exceedingly interesting. But probably most
people are rather more familiar with the spiders that make

Arachnida.

57

the conspicuous webs. These kinds lead a rather seden-
tary life, preferring to set traps for their game rather than
actively hunt for it.

The spinning apparatus consists externally of two or
three pairs of short segmented appendages under the tip
of the abdomen. Each of these spinnerets has many short,
hairlike projections, with a perforation at the tip of each.

Fig. 41. The Spinnerets of the Common Garden Spider.

Within the abdomen are glands which secrete a liquid sub-
stance of which the web is made. When the spider wishes
to spin it presses the spinnerets against some surface, and
the exuded liquid adheres ; then as the liquid is drawn out
into a slender thread it hardens as it is drawn, making a
thread often of hundreds of strands united. The feet of
the spiders have blunt claws with a series of teeth, by
means of which they can easily walk on the web without
tearing it. In spinning the webs with radiating and concen-
tric lines, such as we have often noticed, the spider first
spins a few foundation threads, then the radiating threads.

--^ 53^^tL^^t--^(f^fl{f^^ Zoology.

After this it begins at the center and proceeds spirally
outward ; but when this spiral web is completed it begins
once more at the outside, and takes up this spiral and
replaces it with a spiral spun in the reverse direction. It
bites off the first spiral, and, rolling it up into little balls,
drops them to the ground, hence it was formerly supposed
to eat the web. The web is not placed quite vertically.

Fig. 42. Head and Mandibles of Common Garden Spider.

The spots above are eyes.

and the spider hangs on the under side, so that when a fly
is caught it can run to a point over it and drop down and
quickly catch it. It is usually the female that is on the
web, while the male may be hidden near by. The male is
sometimes much smaller than the female and generally
brighter-colored.

We have often wondered how it is that on some bright,
warm summer days there is so much spider web, or
" gossamer," floating in the air. This is mostly formed by
small spiders. They climb up on a fence or stump, or
other place where there is an up current of air, caused by
the heat of the sun. Standing with the tip of the abdomen
pointing upward a thread is started ; the current carries it
upward as it is formed, and after awhile the current bears
up, not only the thread, but the thread maker, — the spider
itself, — and they may often be seen by the hundreds float-
ing along, so many tiny, unpatented airships.

:r7r;

Arachnida. 59

It is said that these gossamer webs are a sign of fair
weather ; so these Uttle creatures seem to have forerun
mankind in forecasting the weather as well as in aerial
navigation.

Some spiders construct funnel-shaped webs, and remain
concealed at the small end of the funnel, ready to rush out
when their delicate sense of touch informs them that some-
thing is shaking the web, as when an insect is caught.
Gently disturb such a web, and see the occupant dart forth.

Another use of the web, and almost the only use in some
spiders, is as an envelope for the eggs. The web forms a
silky but tough covering, usually deposited in some place
of safe-keeping, but rarely carried by the mother. There

Fig. 43. Spider, with Cocoon attached to Spinnerets.

are many eggs in one such case, and when hatched
the little spiders sometimes become cannibals, each eating
as many as it can of its brothers and sisters.

Kinds of Spiders. — There are many kinds of spiders ;
among the largest is the tarantula; the bite of this and of
some other large spiders is very painful to man, but most
of the stories told of spider bites are gross exaggerations.
The trapdoor spider is an interesting form ; it lives in a
hole in the ground, lines its hole with web, and makes a
lid which it hinges with the web. One spider lives under
water, forming an arched web, under which it stay«^, carry-
ing down bubbles of air which are introduced beneath
the web.

6o Descriptive Zoology.

Scorpions. — Scorpions are found in warm countries,
reaching their greatest size in tropical America and Africa.
The form shown in Fig. 44 occurs from North Carolina to
Florida. Other species are found in the southwestern
United States as far north as Kansas. The body consists
of a short, unsegmented cephalothorax, followed by a
twelve-segmented abdomen. The anterior part of the ab-
domen is broad, the hinder part narrow, ending in the poi-

Fig. 44. Scorpion.

son sting. The sting is painful and serious to man, but
seldom fatal. The scorpions are nocturnal, and feed on
the blood of insects. Respiration in the scorpions is by
means of lung books, as in the spiders.

Harvestmen. — The harvestmen, or daddy longlegs, are
similar to spiders, but with extremely long legs. They
frequent shady places, and live chiefly on small insects,
such as plant lice.

Mites and Ticks. — These are small and often degenerate
forms of Arachnids. Many of them are parasites, sucking
the blood of mammals, as ticks on dogs, cattle, and even
man. Among the mites is the "itch mite," which has
been made rare by the spread of " soap and civilization."

CHAPTER IV.
BRANCH ARTHROPODA.

CLASS CRUSTACEA.
Example — The Crayfish.

Occurrence. — Crayfishes are found fairly abundant in
streams and ponds in many parts of the United States.
They may be seen crawling about on the muddy bottom,
but, being n.octurnal in their habits, they usually escape
observation during the daytime by hiding in holes, under
stones, and especially under ledges of rocks, overhanging
banks, or where the stream has washed out the soil about
the roots of trees standing on the banks.

Crayfish Holes. — Crayfishes are also found in holes
which they dig, usually in low ground. When the water
dries up from the ponds and creeks, crayfishes often dig
down to water, and, at this season, live in these holes.
The holes are frequently many feet deep. The soil and
clay are brought up in pellets, and with these a "chimney"
is built up around the mouth of the hole.

How the Crayfish Walks. — The crayfish walks by means
of the last four pairs of thoracic. legs. Each of these legs
has seven segments ; and the successive joints admit of
motions in different planes, so that the whole appendage
has great freedom and variety of movement. The cray-
fish usually walks slowly, holding out the big pinchers in
front. It can, however, walk sideways or backward. When
taken out of water the crayfish walks with a heavy, awk-

6i

62 Descriptive Zoology.

ward movement, frequently bumping its body upon the
floor ; it evidently needs the buoyancy of the water to sup-
port its weight.

How the Crayfish Swims. — Swimming is the most rapid
action of the crayfish, and it probably seldom resorts to this
means of locomotion except to escape enemies. The side
parts of the " tail fin " are spread out as wide as possible,
and the whole abdomen is suddenly and forcibly bent down,
under, and forward. This makes a powerful stroke, and
drives (or rather pulls) the crayfish swiftly backward. The
whole of the under surface of the abdomen is concave, thus
getting a good hold on the water. As the animal darts
backward the resistance is greatly reduced by the convexity
and smoothness of the dorsal surface of the abdomen.
Again, since the big pinchers rather necessarily extend
forward, it would be difficult for the crayfish to move for-
ward with any considerable speed ; but when it darts back-
ward the big claws drag along in the wake without any
special resistance. It should be further observed that when
the crayfish is frightened, the chances are that it is on or
near the bottom, which in most cases is more or less muddy ;
when the powerful tail stroke is made, it would naturally
sweep close to, if not actually touch, the muddy bottom.
This stirs up the mud, and thus makes the water turbid
between the pursuer and the pursued, and greatly favors
the chances of escape.

The Muscles of Locomotion. — The muscles which move
the appendages are inclosed in the framework along the
ventral surface of the cephalothorax. The muscles which
flex and extend the abdomen in the act of swimming fill
most of the space in the abdomen. As would be expected,
the extensor muscles are much smaller than the flexors.
The extensors arise from the side walls of the thorax, and

Fig. 45. External Features of the Lobster,

' From Packard's Zoology.

64

Descriptive Zoology,

extend back into the abdomen, being attached to the an-
terior edges of the abdominal rings in the upper part of the
abdomen. When these muscles shorten they pull the an-
terior edge of each tergum under the posterior edge of the
preceding tergum, and thus straighten the abdomen. The
extensor muscles lie above the intestine. Below the intes-
tine, and filling out most of the space of the abdomen, are
the flexor muscles. These are very complicated. Like the

Extensor muscle

Abdominal artery.

Tergum.

Intestine

Flexor muscles.

Pleurum.
Nerve cord.

Epimerum. y^„^^^,

abdominal artery.

Sternum.
19, one of the swimmerets.

Fig. 46. Cross Section of Abdomen of Crayfish.

From Huxley's Crayfish.

extensor muscles, they originate in the thorax, and extend
back and are inserted on the sternums ; and when they
shorten, they flex the abdomen, giving the powerful stroke
by which the animal swims backward so rapidly.

Food of the Crayfish, and Mode of Eating. — The crayfish
lives largely on worms, the larvae of insects, with which
most waters abound, snails, etc. The crayfish is carnivorous
by choice, yet by necessity may be almost omnivorous. It
is a greedy eater, and does not disdain carrion. It is de-

Crustacea.

65

cidedly useful as a scavenger, disposing of a

great amount of dead and decaying material

which would pollute the water, ^

such as dead fish, clams, etc. In

eating, the ^ vbi^ pinchers may

tear the food to pieces,

and then the smaller pinch-

ers of the second and third 0

pairs of legs may transfer i

the pieces to the mouth, the «" o

entrance to which is sur- |" ^

rounded by the maxillipeds. e- ^

Or, instead of this process, | c

the crayfish may apply the ^ g

mouth directly to the food, | 5

and gnaw it off in bits by |*

means of the mandibles and f'

maxilhpeds. Crayfishes S

are frequently, guilty of |

cannibalism.

M

3

The Digestive System of =
the Crayfish. — The mouth |
of the crayfish is^oiTTh^ I
under surface instead of at |
the front of the head, as
in many animals. There
are six pairs of mouth parts
mandibles, two pairs of maxillae, and
three pairs of maxiUipeds. These
jaws all move sidewise ; and when all of them
are closed, the third or hindmost pair of
maxillipeds cover all the others. The short
gullet passes straight up from the mouth to

66 Descriptive Zoology.

the stomach, which is situated in the head. The stomach
is very complicated. It has in its walls a set of arms or
levers so jointed together as to support the walls of the
stomach. Further, these bars, which are composed of
chitin, are acted on by sets of muscles on the outside.

There are teeth on the inner walls of the stomach, some
projecting inward from each side and some from the upper
surface. Certain muscles attached to the outside of the
stomach act in such a manner as to make these teeth work
together and masticate food in the stomach. The function
of the stomach is wholly masticatory, and it has no digestive
function. At the hinder part of the stomach there is a
series of stiff hairs which act as a strainer, so that only
very fine particles are allowed to pass on into the intestine.
Alongside the stomach on each side is the large digestive
gland. Each of these opens by a duct into the intestine just
back of the stomach. These glands were formerly called
livers, but in function they more closely resemble a pancreas,
their secretion digesting proteids and fats, and perhaps
also starches. Beyond the stomach the intestine extends
in a nearly straight course along the upper part of the
abdomen, ending in the anus on the under surface of the
telson.

Respiration in the Crayfish. — The crayfish breathes by
means of the plumelike gills, which are covered by the
sides of the carapace. Each gill has two blopd^tubes in its
stem, through one of which the blood enters, while it returns
through the other tube. In the feathery branches of the
gill the blood is separated from the water by merely a
thin membrane, so that the blood and the water make an
exchange, the blood getting oxygen from the water, and
giving to the water the waste products — such as carbon
dioxid — which it contains.

Crustacea.

67

There are Two_Sets of Gills. — One row is attached to
the bases of the thoracic appendages ; these are the foot
gills. A second row arises from the joints by which the

WATER
CURRENTS T

Fig. 48. Cross Section of a Crayfish through the Heart,

Showing the gills, blood currents, and water currents.

thoracic appendages are attached to the thorax ; these
are the joint gills. (In the lobster there is a third set,

68 Descriptive Zoology.

higher still, arising from the side of the thorax, and called
the wall gills.) The lowest set, the foot gills, have leaflike
extensions along their borders, which perhaps serve to keep
the filaments of the gills from becoming entangled with
one another. The gills all have their free ends extending
upward. The direction in which the gills extend is in
keeping with the fact that the water which bathes the gills
enters about the bases of the legs, and, passing over the
gills, escapes near the anterior end of the cephalothorax,
back of the base of the antenna of each side. It has been
observed that the cephaHc groove marks the distinction
between the head and the thorax. This groove also marks
the anterior limits of each gill chamber. In the extreme
anterior part of the gill chamber, extending obliquely up-
ward and backward, is the gill paddle or gill scoop. It is
a part of the second maxilla. It is attached by its middle
part, and each end is a somewhat spoon-shaped paddle.
By a constant back-and-forth motion this paddle continu-
ally bails the water out at the anterior end of the gill
chamber, and thus draws more water in at the lower border
of the gill cover, between the bases of the thoracic legs.

Circulation in the Crayfish. — The heart is situated in
the dorsal part of the cephalothorax. From its anterior
end arise five arteries : a single artery in the middle line
supplies the eyes ; back of this a pair run to the antennae ;
and, still further back, a pair lead to the digestive glands
of the two sides. At the posterior end of the heart arises
one artery, which almost immediately divides into two
branches; the first branch runs straight back, just above
the intestine, and is called the dorsal abdominal artery;
the other branch extends downward, passing through the
nerve cord. After passing through the nerve cord it again
divides into two branches, one running forward, the sternal

Crustacea. 69

artery, and the other extending backward, the ventral ab-
dominal artery.

All these arteries divide and subdivide, forming capil-
laries. But the capillaries do not reunite, forming veins ;
they empty into more or less irregular spaces in the body,
around the muscles and other internal organs. All these
spaces, or sinuses, as they are called, lead into one main
channel, the sternal sinus, which extends along the middle
of the ventral region. From this sinus, passageways con-
duct the blood to each gill. In each gill one tube, the
afferent vein, conveys the blood to the gill filaments ; while
another tube, the efferent vein, returns the blood to another
set of veins, called the branchio-cardiac veins, which lead
to the pericardium. There are no tubes to convey the
blood into the heart, but the blood enters the heart directly
through three pairs of holes, one on each side, a pair on top,
and another pair below. These holes have lips on the
inside, which act as valves, allowing the blood to enter
freely, but preventing a reflow through the holes. Thus
the beating of the heart causes a constant flow of blood in
one direction : first to the tissues of the body in general,
where it gives up oxygen and food materials and picks up
carbon dioxid ; then to the gills, where it gives off ca^rbon
dioxid and gains oxygen ; then back again to the heart
The blood is colorless, but after exposure to the air it
turns bluish.

Excretion in the Crayfish. — In connection with the study
of the gills we have seen how the carbon dioxid is removed
from the body. But the nitrogenous wastes are excreted
by a pair of kidneys, which are called, on account of their
color, the green glands. They are situated in the head,
just below and in front of the stomach. The gland proper
is a button-shaped body, lying close to the ventral body

70 Descriptive Zoology.

wall. This leads into a thin sac, which serves as a bladder,
and it in turn opens by a duct to the exterior, through the
apex of a hard, white, conical papilla, on the ventral surface
of the base of each antenna.

It is worthy of notice that the current of water coming
from the gills passes directly by this other exit of waste,
so that one stream carries away all the waste products,
avoiding dupHcation of machinery.

The Nervous System of the Crayfish. — The nervous sys-
tem consists of a nerve cord which lies on the floor of the
body cavity, extending the whole length of the body in the
middle line. It is a white cord, composed of a ganglion
for each segment, connected in line by nerve fibers. The
cord is really double, but the two rows of gangHons have
consolidated, so that there appears to be but one row of
ganglions. The cord itself, between the successive gan-
glions, while apparently single, is actually double. And in
two places the double nature of the cord is manifest. The
two parts of the cord pass on the right and left of the
gullet, forming what is called the esophageal ring, or
esophageal collar ; again, the sternal artery passes between
the two halves in the interval between two of the gan-
glions. Though there is a ganglion for each segment,
there is a consolidation, so that there are but thirteen dis-
tinct gangHons for the twenty (or twenty-one) segments.
The first ganghon, called the brain or the cerebral ganglion,
is the result of the fusion of three pairs of gangHons. Back
of the gullet, and connected to the brain by the two com-
missures passing on either side of the gullet, is a large
ganglion, which is evidently composed of the gangHons of
the last three cephalic segments united with the ganglions
of the first three segments of the thorax. Following this
are five more distinct ganglions in the thorax and six in the

Crustacea.

71

abdomen. In the abdomen the nerve cord is in plain view
when the abdominal muscles have been removed. But in
the thorax the cord is concealed in a groove made by the

Antennule
nerve

Antenna
nerve

Nerve ring
around gullet

Sternal artery

Ganglion 7

Anus

Fig. 49. Nervous System of Crayfish.

From Huxley's Crayfish.

inward projecting framework which supports the muscles
which move the appendages. From each ganglion nerves
radiate to supply the adjacent muscles and sense organs.

72 Descriptive Zoology.

The Senses of the Crayfish. — The crayfish appears to
have the senses of touch, sight, taste, and smell.

The Sense of Sight. — The eyes are on movable stalks.
The advantage of being able to project the eyes is ap-
parent. The protection afforded by withdrawing the eyes
is almost equally apparent when we consider that cray-
fishes fight fiercely with each other, besides being frequently
under the necessity of protecting themselves from enemies
outside of their own race. The projecting rostrum and
the sharp blade of the lamina of the antenna need no ex-
planation as to their use. The eye of the crayfish is a
typical compound eye. It is made up of distinct parts,
each of which is called a facet, or cornea.

The Sense of Touch. — One does not need to experiment
long with crayfishes to be sure that they feel as well as see.
The general surface of the body is more or less sensitive
to touch, but with such a hard covering this sense can
hardly be other than a very dull sense over most of the area.
But the antennae are specially adapted for this sense, and
their long, slender, tapering form and jointed structure
render them convenient to apply to surrounding objects.

Smell and Taste. — Certain hairs of the external branch
of the smaller antennae are believed to be connected with
the sense of smell.

There is in the basal joint of each antennule a sac,
formed by the depression of its outer surface, so that free
communication is left with the surrounding water. This
was long supposed to be an organ of hearing, but is now
regarded as the seat of the sense of equilibrium.

There is no doubt that the crayfish discriminates in
choice of food, and we have good reason to believe that
the sense of taste is present.

Crustacea. 73

The Enemies of the Crayfish. — Various carnivorous
fishes, such as blacl^ bass, eat crayfishes, hence the fisher-
man also becomes an enemy of the crayfish by capturing
it for bait. Raccoons are very fond of crayfishes. Both
of these animals are nocturnal in their habits ; so when the
crayfish sets out in the evening to get a lunch, the raccoon
lunches on the luncher. One who frequents the woods
may see the raccoon tracks along the creeks where it has
been seeking this and other aquatic animals for food.
Muskrats and crows are also among the more important
enemies of the crayfish.

How the Crayfish escapes its Enemies. — In the first place
its noctumal-Jmbits keep it out of sight of some enemies.
Second, its coIoT-is in close harmony with its surroundings,
so that it is very inconspicuous. Dull shades of green,
brown, and red are the prevailing colors.

Though the seRses of the crayfish are none of them very
acute, they plainly are useful in making the animal aware
of the approach of enemies. Then it is usually near the
bottom, where there are many places of refuge. And last,
but not least, this creature has one kind of locomotion that
is speedy, that of swimming. The hard covering may
make the crayfishes objectionable as food to many animals
that otherwise would eat them. The big pinchers, too,
which he knows so well how to use, are no mean defense
against his lesser foes. And further, the threatening atti-
tude which the crayfish assumes when cornered, may
intimidate some would-be assailants who do not like the
looks of the bristling claws, and fear that the " bite will be
as bad as the bark."

The Eggs of the Crayfish. — The eggs are extruded
as usual, but instead of being left in some place of de-
posit, are attached to the mother by being glued to the

74 Descriptive Zoology.

swimmerets. The eggs are small and smooth, reddish or
dark, and in the mass suggest the appearance of a berry ;
hence the mass of eggs is called the ** berry." A lobster
with the eggs attached is called a "berry lobster." From
the eggs hatch the little crayfishes, which have the form of
the adult. These little fellows have incurved hooks on the
ends of their claws, by means of which they take fast hold
of the swimmerets of the mother and remain so attached
for some time.

Rate of Growth of Crayfishes. — The crayfish is about a
quarter of an inch long when hatched. At the end of the
first year it is about an inch and a half long. After the
first year it grows more slowly, and seldom becomes more
than five or six inches in length.

Molting. — Since the hard parts are on the outside,
such creatures would soon reach a limit of growth unless
some special provision were made. This is provided for
by the shedding of the entire outer hard covering at stated
periods. The hard shell splits across the dorsal surface
at the junction of the cephalothorax and abdomen. The
carapace also usually splits part way forward from the
transverse opening above mentioned. By severe effort
the cephalothorax and its appendages are first extracted ;
then the abdomen is pulled out of its hard covering. This
is a critical period in the life of the crayfish. Sometimes
the big pinchers are broken off in the effort to get them
out of the old case. Crayfishes sometimes perish in the
struggle to get free from their *' hide-bound" condition.
And for some time after molting the body is soft, and
hence almost defenseless. At this time the animal is un-
usually timid, and lives in hiding till its skin again hardens
by the addition of limy matter. After shedding, the cray-
fish is doubly helpless; not only is his body soft and easily

Crustacea. 75

injured, but his claws, being soft, are useless as weapons of
defense. In molting, the hard Hning of the stomach, with
the stomach teeth, is also shed. Crayfishes molt several
times the first year, the number of molts gradually decreas-
ing till in adult Hfe the molt probably takes place but
once a year.

"Crab*s Eyes." — Previous to the time of molting there
appear on the sides of the stomach two button-shaped
'bodies of Hmy material. In molting they are shed into
the cavity of the stomach, together with the lining of the
stomach. It is believed that they break up, become dis-
solved, and are absorbed and then deposited as stiffening
matter in the chitin, which makes the basis of the envelop-
ing crust.

Restoration of Lost Limbs. — Crayfishes often lose their
legs while fighting. Sometimes also they seem to drop
them or throw them off when badly frightened, but
perhaps they are merely snapped off in the violent effort
to escape. The legs seem to break off always at the same
place, where the leg is most narrow, and this is the easiest
place to heal. The blood quickly coagulates, and such
loss seems not to be dangerous or even serious. The
mutilated stump at once begins to grow a new leg, but
for a long time it is smaller than its mate. If one looks
over a number of crayfishes, he is pretty sure to find some
in this condition. The big fighting Hmbs are ordinarily
the ones that have been lost.

Are Crayfishes Beneficial or Injurious to Man ? — Crayfishes are good
to eat, the only part, of course, being the muscle, most of which is in
the abdomen. They are used as food to a considerable extent in
Europe, but they are little used in this country. Crayfishes are very
useful as scavengers, eating dead fish, etc. Crayfishes are said to
benefit some heavy, clayey land by the holes they dig, perhaps by mak-
ing the soil more porous and helping to drain it

76 Descriptive Zoology.

On the other hand, crayfishes often do very great damage by digging
holes in the dikes and levees along the lower Mississippi. These holes
gradually become enlarged, perhaps by muskrats, and may finally cause
the levee to give way, inundating vast tracts of land which are protected
by the dikes, and causing immense loss of property and sometimes of
life.

Distribution of Crayfishes. — Crayfishes are fairly common through-
out the United States, more especially in the central and southern por-
tions. They are usually more abundant in regions where there is plenty
of limestone, and are less abundant where granite rock prevails, as in
New England. They are to be found in Ireland and England and on
most of the continent of Europe, in Australia, New Zealand, Madagas-
car, and Japan. But they occur in very limited areas in Asia and South
America. In Africa none have ever been found.

Origin of Crayfishes. — It is supposed that the crayfishes are descend-
ants of marine crustaceans ; that some of these forms lived about the
mouths of rivers, gradually became accustomed to partly freshened
water, and in time to fresh water, and ascended the streams and entered
lakes. We do not know any living salt-water crustacean from which
the crayfish is supposed to have been derived.

M>

CHAPTER V.
BRANCH ARTHROPODA.

CLASS CRUSTACEA {Continued).

Lobsters. — With a few unimportant exceptions, the
structure of the lobster is essentially the same as that
of the crayfish. The lobster may be said to be a big salt-
water crayfish, or the crayfish a small fresh-water lobster.
Lobsters are an important food product of the North At-
lantic, both to the old world and the new. From twenty
to thirty millions are caught annually along the coasts of
New England and Canada. They are captured by sinking
large wooden traps, which are called " lobster pots." These
are baited with refuse fish. A buoy is attached to each
trap to mark its place, and to serve as a means of taking up
the trap. The lobsters thus caught average less than four
pounds in weight, but specimens have been found that
weighed as high as thirty-nine pounds.

Shrimps and Prawns. — Two other marine crustaceans
that are largely used as food are the shrimps and prawns.
These are essentially like the crayfish, but differing from
it more than the lobster. They are caught in large numbers,
and eaten fresh or canned, as is the lobster. Prawns have
a permanent hump on the dorsal surface of the abdomen ;
and the dorsal surface rises as a sharp ridge, perhaps to
diminish resistance, and thus increase its speed when swim-
ming. Most of our so-called shrimps, out of which the
famous salad is made, are really prawns, and not shrimps.

77

78 Descriptive Zoology.

Crabs. — Though differing considerably in appearance,
crabs have the same essential structure as crayfishes and lob-
sters. The cephalothorax is broad instead of being rela-
tively long and narrow. The abdomen is kept folded under
the cephalothorax, and is not used in swimming, almost its
only use being to protect the eggs in the female. As in the
preceding forms, there is the hard protecting crust ; stalked
eyes ; several mouth parts ; five pairs of large thoracic ap-
pendages, the first pair armed with big pinchers ; gills on

Fig. so. Shrimp.

the sides under cover of the carapace ; and the same general
manner of life. Crabs are great scavengers ; and if, while
at the seaside, one wishes to clean a skeleton, if he puts it
into a box guarded by slats, with spaces just wide enough
to let crabs in, they will do the rest. Crabs may be caught
by tying a piece of meat to a string and letting it down off
almost any wharf or rock into the water. When the crab
takes hold with the pinchers he will usually hold on till he
reaches the surface ; and while he may be lifted out on the
wharf or bank, it is safer to use a net when he is brought
to the surface. Though most crabs are good to eat, and
many kinds are so used, the one most eaten is the blue crab

Crustacea.

79

[Callinectes kastatus), often called the " edible crab." Just
after they molt they are esteemed good, cooked whole,
under the title " soft-shelled crabs."

Swimming crabs, such as the blue crab, have the last pair
of thoracic legs developed as paddles, by means of which
they swim sideways with considerable rapidity. In the

Swimming legs.

Fig. 51. Lady Crab, Natural Size.

case of crabs that do not swim, the last legs are not flat-
tened, but end in a point like the other legs. The little
oyster crab is often found in an oyster stew (Fig. 52).

Development of the Crab. — It is very interesting to note
that the crab, when first hatched, has nearly the form of
the crayfish, with an extended abdomen and a relatively
narrow body, but that gradually the cephalothorax widens,
and the abdomen becomes folded under the body. Crabs

8o Descriptive Zoology.

are regarded as the highest, and probably the latest, of the
crustaceans. While the development of the individual does
not recapitulate the development of the race quite so fully
as in some other groups, it serves very well to illustrate the
general law that the development of
the individuals of the highest group
is an epitome of the development of
the group as a whole, and often is a
recapitulation of the order of geo-
logical succession.

Fig. 52. Oyster Ckau,

Cephalization. — By this term is meant the
higher development of the head, and of the appendages belonging to and
immediately surrounding the head. In the lower forms of crustaceans
the head does not predominate as in the crabs. The diameter is ap-
proximately the same from one end to the other. Even in the crayfish,
the ganglion at the anterior end is very little larger or better developed
than those of the abdomen. In the crabs there is a much greater con-
centration of the ganglions in the thoracic region. This principle will
be illustrated in other groups of animals, but it can be seen here that the
higher in the scale, the greater is the development of the head regions.
The Sand Crab. — This crab, with numerous others, lives out of
the water considerable of the time. It is sandy in color, and lives
out on the beach. It seems to be rather keen sighted, and runs at
a lively rate when pursued. It usually attempts to escape, and often
succeeds, by burying itself in the sand. This it does in a wonderfully
short time. With a few quick, jerky motions of its legs it buries itself,
usually leaving only the tips of its two eyes projecting above the surface.
It is practically concealed, — so much so that one who has pursued it,
unless he looks closely, may lose sight of it ; but the crab has its enemy
in sight all the time. Its means of escape is ingenious, and the color is
a fine example of protective resemblance.

The Fiddler Crab. — This litde crab, about two inches wide, has one
big and one small pincher, suggesting the fiddle and bow. These very
interesting little fellows are sometimes so thick on the shore, along the
water line, that they crowd each other for crawling room, and make a
very noticeable rustling noise as they elbow each other while retreating
from the inquisitive biped, of whose motives they are suspicious.

Crustacea.

8i

Blind Crayfishes. — In the Mammoth Cave, and some other caves,
are found blind crayfishes. This does not mean that in all cases eyes
are completely lacking, — in fact, in most cases rudiments of eyes are
present, but useless. How long these animals have thus lived in dark-
ness we do not know ; but we find that an organ that is no longer used
may lose its function and even dwindle away. We here see illustrations
of the general law that disuse leads to deterioration in both structure
and function, often resulting in complete uselessness, and perhaps com-
plete atrophy as well.

Hermit Crabs. — These crabs back into an empty univalve shell, which
they carry around with them for protection. The abdomen, and all the

Fig. 53. Blind Crayfish of Mammoth Cave, Natural Size.

parts except the head and projecting appendages, become soft, and de-
pendent upon a continuance of such protection. When the crab gets
too big for the shell, he hunts for a bigger one. It is said that these
crabs sometimes fight over shells. One hermit meeting another crab
that has a shell that he thinks would fit him better than the one he has,
ejects the other fellow, perhaps only to find that he has gotten a misfit
after all, and so goes back to his old shell, a wiser if not a better crab.
Barnacles. — If one lies down on the edge of almost any stone pier
or wharf along the coast and looks down into the water, he may see a

82

Descriptive Zoology.

fjeneral wavelike motion as if hundreds of hands, with feathery
fingers, were constantly ojDening and closing. Looking closer, he will
see that these feathers are in clusters, each projecting from the apex of a
cone-shaped body whose base is attached to the rock wall. These are
acorn barnacles. Disturb them and they will draw in their feathery
appendages and close the shelly valves that guard the opening. They
resemble bivalve mollusks, and in fact were regarded as mollusks until
it was discovered that when young they are like the young of the lower
Crustacea. After leading a free-swimming Hfe for a time, they attach

Fig. 54. Hermit Crab in Shell of Sea Snail.

themselves by the head end to a rock, and thenceforth live anchored to
this one spot. They have given up locomotion, and become sessile.
The law of progress in evolution is toward greater freedom, as illus-
trated in many forms of animal life ; but here we have a good example
of retrograde development, or degeneration. Almost the only ready
indication of its cmstacean relationship is the segmentation of the
appendages.

Another form of barnacle is the goose barnacle, which has a body
resembling a clam, attached by a soft, flexible stalk to some solid
object, frequently to a piece of floating timber. When actively feeding,
the shell opens and the feather-like feet extend in lively motion, but

Crustacea.

83

they are withdrawn and shut in if the animal is disturbed. In its devel*
opment the goose barnacle has about the same history as the acorn
barnacle.

Other Degenerate Crustaceans. — Degenerate as are the barnacles,
there are still lower crustaceans. Various crustaceans have become
parasites, living attached to whales, fishes, etc., and have become so
degenerate as to have lost all likeness to the typical crustacean struc-
ture, so that no one would, without pro-
longed investigation, even suspect that they
belonged to this group.

All of the above cases, blind crayfish,
hermit crab, barnacles, and parasitic Crus-
tacea, illustrate one general principle, that
disuse leads to atrophy, and that parasitic
habits involve degeneration in structure as
well as in function.

Classification of Crustacea. — The Crus-
tacea are divided into two subclasses, the
Entomostraca and the Malacostraca.

The Entomostraca are of comparatively
simple structure, usually small, sometimes
microscopic. The number of segments is
variable, and the appendages are very similar throughout,
briefly consider some of the leading orders.

Some of the Phyllopoda are covered by a flat, shield-shaped carapace ;
others have a bivalve shell which does not inclose the head. Some
Phyllopods have no carapace. In some forms the body is unsegmented,
and there are leaflike, lobed, swimming feet.

The Ostracoda are small and the head as well as the rest of the
body is inclosed in a bivalve shell, somewhat resembUng a Httle clam.

The Copepoda may be represented by the cyclops, or water flea,
Fig. 56. This form is common in sluggish streams and ditches. It
is white, large enough to be seen by the naked eye, and swims by a
jerky motion of the antennae, which are its largest and strongest
appendages. The female bears two large egg masses.

The Cirripedia comprise the barnacles above mentioned.

The Malacostraca comprise the higher Crustacea. They are usually
of considerable size, and the number of segments is rather constant,
instead of variable as in the Entomostraca. There may or may not be

Fig. 55. Goose Barnacles.

From Kingsley's Comparative
Zoology*

We may

84

Descriptive Zoology.

a carapace, and the head may consist of but one piece, formed by the
consolidation of several segments (usually five). The thorax has eight
segments and the abdomen usually seven.

Without attempting to enumerate the orders, we may mention the
Amphipoda, and illustrate them by the beach tieas and sand hopperS;

Fig. 56. Water Flea (Cyclops).

Female with egg sacs. There is a single eye with two facets.

which have a laterally compressed body, the anterior legs bearing gills,
and the posterior used for jumping.

The Isopoda have a body flattened from above, and bear gills on the
abdominal appendages, as in the sow bug, shown in Fig. 57.

The Decapoda, or ten-footed Crustacea, are so named from the five

large pairs of thoracic appendages observed in the crayfish, which serves

•N^ . \ ^ as an example of the group. The Decapods

\ ^^^J|H^^^^> are sometimes further divided into the

^■H^^^^^Hfeg^ Macrura, or long-tailed forms, such as the

/^3HRH|B^^ crayfish and lobster, and the Brachyura, or

I -^|n]nv^^ short-tailed forms, such as the crabs.

Fig. 57. Sow Rug
(Crustacean).

Characters of Crustacea. — i . The
crustaceans have a hard cuticle,
formed by the underlying skin. The cuticle consists
largely of a substance called chitin, which is tough and
more or less elastic. The chitin becomes more or less
infiltrated by carbonate of lime, and is thus made harder.

Crustacea. S5

2. But the limy material is not deposited everywhere in
the cuticle. Certain places are left for joints. At these
places the chitin remains flexible. Hence we have a series
of segments joined together, five in the head, consolidated,
eight in the thorax, and usually seven in the abdomen,
twenty being the typical number in the higher forms.

3. Not only is the body segmented, but normally each
segment bears a pair of appendages, which are themselves
segmented. The eyes are no longer regarded as append-
ages, but outgrowths of the head, which later become
movable by means of a joint.

4. Most crustaceans have gills and lead an aquatic life.
Some of the simpler forms breathe by the whole surface
of the body, and a few forms which have gills live out of
water, but usually in damp places. The gills remain moist,
a small amount of water serving to transmit the oxygen
from the air to the blood within the gills.

5. Crustacea normally possess two pairs of antennae.

6. Most crustaceans have compound eyes.

7. Crustaceans are an active group, but, as above
noticed, some are sessile, and others parasitic.

The King Crab. — The king crab, or horseshoe crab, has a body
shaped somewhat like a horseshoe. A six-sided abdomen fits into a
deep notch in the posterior margin of the cephalothorax, and ends in a
long, tapering spine. On the cephalothorax is one pair of simple and
one pair of compound eyes. The mouth is in the center of the under
surface, between the bases of the legs, and a series of leaflike gills are
to be found under the abdomen. The king crab is found along our
Atlantic coast, often burrowing in the sand. It molts by splitting the
shell along the anterior margin. The hard crust, the molting, the gills,
and general mode of life would seem to ally the king crabs to the Crus-
tacea, but later researches place them nearer the spiders. They have
some points of relationship with the extinct trilobites, and are especially
interesting as the only known survivors of their race.

86

Descriptive Zoology.

CHARACTERISTICS OF ARTHROPODS.

1. Arthropods have an external skeleton, or cxoskeleton.

2. This skeleton consists of a series of rings, movable
upon one another, i.e. the skeleton is segmented.

3. Some of these rings, or segments, bear appendages
that are segmented.

Classification of Arthropoda.

Arthropoda.

Crustacea (CI

ass I). '

(Tracheata.)

I. Aquatic

(generally) — breathe

I. Aerial — breath

le by

air tubes

by gills.

or " lungs."

2. Antennae

: — 2 pairs.

2. Antennae— I pair (or none).

(Class n)

(Class HI)

(Class IV)

Arachnida. ,

Myriapoda. -^4 .
. i.' 'Head.1

Insecta.

Parts of 1 I. Head-thorax.
Body. \ 2. Abdomen.

Other rings
Many-^ all alike.

2. Body worm-

/I. Head.
Three \ 2. Thorax.
1 3. Abdomen

like.

Legs.

4 pairs.

Many pairs.

3 pairs.

Antennae.

None.

I pair.

I pair.

Jaws.

2 pairs."

2 or 3 pairs.

2 pairSo

CHAPTER VL
BRANCH ANNULATA.

THE SEGMENTED WORMS.

Example — The Earthworm.

Habits of Earthworms. — The name " earthworm " is so
appropriate that no one questions its fitness. As every one
knows, the earthworm burrows through the soil, usually
making the hole deep enough to reach moist earth. The
first portion of the burrow is usually vertical, but deeper
its course is somewhat irregular. The worms swallow the
soil, and from it they derive a considerable part of their
food, digesting out of it the organic matter, which is largely
composed of decaying plant material. The earthworm has
the advantage of utilizing as food the material which it
must excavate to make its burrow. In this respect it has
a decided advantage over such animals as the mole or
pouched gopher, which, as they proceed, are obliged to
carry out or push aside the soil without deriving any
immediate benefit from it. Earthworms are nocturnal in
their habits, and the fact that they are seldom seen except
when dug up leads most people to suppose that they spend
their whole lives beneath the soil. But this is not the case,
for if one searches for them with a lantern, they may be
found in summer nights, sometimes wholly out of their
holes, sometimes partly out, holding fast to the sides of the
burrow by the tail end, and ready to retreat at the approach
of danger. If they are found crawling about in the day-

87

88 Descriptive Zoology.

time, except after a heavy rain, it is pretty good evidence
that they are diseased. Often in such cases it is found
that they have been parasitized by a fly. Nearly every
one must have noticed in the morning the fresh excrement,
at the mouths of their burrows. These coiled ** castings,"
as they are called, are the residue of digestion, and as the
amount of nourishment in the soil is not great, and since
the worm must do considerable excavating, the amount of
the "castings" is necessarily considerable. In dry wea^
ther the worms dig deep, and may be several feet from the
surface. But when the ground is fairly moist they often
remain during the day near the surface, with one end near
the end of the hole. In winter they hibernate below the
reach of frost.

Form of the Earthworm. — The end that usually goes
foremost is the anterior end, and the hinder end is the
posterior end. When crawling on the ground the surface
on which the worm rests is the ventral surface, and the
surface uppermost is the dorsal surface. If the earthworm
were split lengthwise in the middle line by a vertical plane,
the right and left halves would be counterparts of each
other, that is, the earthworm is bilaterally symmettical.
The earthworm is approximately cyHndric, the anterior
end being more pointed, and the posterior end somewhat
flattened, especially on the ventral surface. The division of
the body into rings, or segments, is very evident. Toward
the anterior end is a region of about six segments in which
the sides and dorsal portions of the segments are swollen
and more or less fused together, forming a wide girdle
called the clitellum, the function of which is to secrete
the capsule in which the eggs are laid.

General Plan of Structure. — As just noted, the body of the
earthworm is cylindric. At the anterior end is the mouth and

Annulata,

89

at the posterior end is
the anus. These are the
two ends of the digestive
tube, which runs straight
through the body, being, on
the average, about half the
diameter of the body. The
body, then, consists of two
tubes,the outer wall,or body
wall, and the digestive tube;
the outer tube, or body wall,
narrowing till it joins the
inner tube. Between these
two tubes is a space, the
body cavity, or celom. In
most of the higher animals
we find a similar space
around the digestive tube
and within the body wall.
In the earthworm the body
cavity is divided into many
compartments by the par-
titions that extend between
the inner and outer tubes
at the constrictions, seen
on the outside, between the
successive segments.

The Body Wall. —This
consists of two coats, each
of which is made up of two
or more layers. Outside is
the skin, and within this
the muscular coat.

pO Descriptive Zoology.

The Skin. — This consists of two layers. Outside is the
cuticle, a thin layer, usually showing a beautiful iridescence.
The cuticle often peels off in specimens that have been in
alcohol. Underneath the cuticle is the epidermis (often
called the hypodermis).

The Muscular Coat. — The muscular coat is very much
thicker than the skin. It consists of two layers, — an outer
layer of circular muscle fibers, and an inner layer of fibers
running lengthwise. The inner layer is much thicker than
the outer.

The Bristles. — The bristles, or setce, are short, stiff, chi-
tinous spines, in four rows along the ventral surface and
lower part of the sides. They are outgrowths of the skin,
and are lodged in inf oldings, or pockets, of the cuticle, which
are called setigerous glands. As the bristles are worn out
and become useless, they are replaced by others ; and in
the same sac may be found bristles in various stages of
development. Each row of bristles is double ; and each
segment, except the first and last, has four pairs of them.
Special muscles are attached to the base of the sac hold-
ing the bristles, so that the bristles can be turned and held
in various directions. The bristles can also be protruded
and withdrawn.

How the Earthworm Crawls. — When the worm wishes to
crawl forward, the spines are turned backward. Then the
longitudinal muscles shorten, and the posterior_end_of the
body is pulled forward, the'^hole body" becoming shorter
and thicker. Next the circular muscular fibers are short-
ened ; this narrows and elongates the body ; but as the
spines prevent any part from being pushed backward, the
result is a forward movement. By a repetition of these
acts the worm effects its slow locomotion. If it wishes to

Annulata.

91

travel with the pos-
terior end fore-
niost, as it does
occasionally, it has
but to point the
spines forward,
and the same action
of the muscles will
propel it posterior
end foremost. If
the worm were
lying on a perfectly
smooth surface, on
which there was
no friction what-
ever, the shorten-
ing and lengthen-
ing of the body
would avail noth-
ing in the way
of locomotion ; it
would be simply
motion. The loco-
motion of the earth-
worm, however, is
not essentially
different from that
of other animals,
— they must all
have some point of
support or resist-
ance by means of
which they pro-

= 3

TO H

ft o

° s

^ 2

era ?3

92

Descriptive Zoology.

gress. Most animals move forward by pushing backward
on some more or less solid support ; the earthworm pulls,
rather than pushes, itself along.

What the Earthworm Eats. — Besides eating the soil, the
earthworm eats leaves, both fresh and decayed, decaying

Circular muscle fibers.

Kidney
pore.

Longitudinal
muscle fibers.

Fig. 6o. Cross Section of Earthworm.

Bristles.

wood, etc. The worms drag leaves into their holes, where
they are moistened by a secretion that prepares them for
digestion. Earthworms eat bits of meat that are left in
their way, and would seem to be almost omnivorous.

The Digestive System of the Earthworm. — The mouth is
a small crescent-shaped opening on the ventral surface of
the first segment. Overhanging the mouth is a small pror
)oscis. There are no teeth, nor anything corresponding to

Annuiata. 93

them. The first part of the digestive tube is the pharynx,
very muscular and thick-walled. Its own muscular fibers
enable it to close with considerable force. Attached to the
outside of the pharynx are muscles radiating in all direc-
tions to the outside of the body wall, by means of which the
pharynx can be retracted and dilated. The pharynx not
only serves in swallowing, but is the worm's only organ of
prehension. By means of the sucking and holding power
of the pharynx the earthworm is able to drag relatively
heavy leaves into the burrow. It is by the strength and
various movements of the pharynx that the worm performs
the work of burrowing. The pharynx extends back about
six segments. Back of the pharynx is the gullet, a slender
tube running to about the thirteenth or fourteenth segment.
Along the sides of the gullet are the esophageal glands,
whose limy secretion is supposed to aid in digestion. At
about segment fifteen the gullet dilates into the large, thin-
walled crop. Separated from the crop by a slight constric-
tion is the gizzard, which extends about two segments.
The walls of the gizzard are very thick and muscular, and
it has a tough chitinous lining. In it, by the aid of sand,
the worm grinds food, as the hen does by means of bits of
gravel, thus making up for the absence of teeth. Beyond
the gizzard, the intestine extends to the anus, which is a
vertical slit at the posterior end. The intestine is about
the same diameter throughout, except that it is constricted
at each partition, and bulges out in each segment.

If a cross section of the intestine be made, it will be
found that the hollow is not circular, as would naturally be
expected from the external form, but is crescent-shaped,
with the concave side of the crescent uppermost. This is
due to a prominent ridge that projects downward from the
upper inner surface of the intestine. This ridge is called

94 Descriptive Zoology.

the typhlosole. It is richly supplied with blood tubes and
serves to increase the surface for the absorption of food.

As the food passes along the digestive tube it has added
to it liquids secreted by the intestinal walls, and these
juices have the power to digest starchy, fatty, and proteid
foods. As the food is digested it is absorbed through the
intestinal walls, either into the liquid of the body cavity,
or into the blood tubes that branch through the walls of the
intestine, or into both of these.

The Blood. — The blood of the earthworm is red, and the
red color is due to a substance called hemoglobin, as in
human blood. But the color is in the liquid itself, and not
in the corpuscles as in our blood. Small colorless corpus-
cles are present in the blood. The liquid found in the
body cavity has also corpuscles, and this liquid is compara-
ble to the lymph of higher animals. It is colorless or
sometimes milky in appearance. There is a minute pore
opening in the dorsal part of most of the segments.

Circulation of the Blood. — In watching the live earth-
worm one sees a dark red streak through the dorsal wall ;
this is the dorsal blood tube. It usually shows plainly a
waveUke motion running from the posterior end to the
anterior end. The action is due to the successive short-
ening of the circular muscle fibers in the wall of the
blood tube, from behind forward. This sort of action is
familiar to many under the name of peristaltic action,
such as takes place in the intestines of most animals. By
this action the blood is continually driven forward in this
blood tube. A similar blood tube is to be found under
the intestine, the ventral blood tube. In it, by the same
means, the blood is sent backward. These are the princi-
pal longitudinal blood tubes, but there are three small
tubes close to the nerve cord. In the region of the gullet

Annulata. 95

are several, usually five, branches that connect the dorsal
and ventral blood tubes ; they arch around the gullet on
each side, hence are designated the "aortic arches"; in
some forms they have a series of enlargements, presenting
a necklace-like appearance. These enlargements contract
and dilate rhythmically, hence they are sometimes called
*' hearts," but they probably have no greater share in the
work of propelling the blood than the other blood tubes.
Connected with these main blood tubes are branches by
which blood is supplied to the body walls, to the walls of
the digestive tube, to the partitions between the segments,
to the kidneys, and all the organs of the body.

One earthworm common in the central states has two
dorsal blood tubes (hence the name, Diplocardia). This is
a large worm whose girdle extends from the 13th to the
1 8th segment. It has two gizzards.

How the Earthworm Breathes. — The earthworm breathes
by means of the skin, there being no special organs
of respiration. The body wall is richly supplied with a
fine network of blood tubes. These are separated from
the external air by a thin membrane only. This thin
and delicate covering is always moist, and through it an
interchange is continually taking place between the blood
within and the air without ; oxygen is being absorbed into
the blood, while carbon dioxid and other waste matters
are passing in the opposite direction. The worm cannot
five long in a warm, dry air, for, when the skin cannot be
kept moist, respiration is stopped and the worm is suffo-
cated. They can endure immersion in water for some
time, but it seems injurious to them. They often are
found crawling about in large numbers after a heavy rain.

The Excretory System of the Earthworm. — Part of the
waste matter, the carbon dioxid, is thrown off by the skin,

96 Descriptive Zoology.

as we have just noted. There is also in each segment
(except a few at the two ends of the body) a pair of simple
kidneys. Each kidney is a tube opening freely into the
body cavity at its inner end, while the other end opens to
the outside through a small aperture in the body wall below
(or sometimes above) the upper row of bristles. This long
tubular kidney is thrown into loops, and there is consider-
able variation in its diameter at different points. Each
tube begins as an open funnel which is lined with ciHa.
The oddest fact about these tubes is that each kidney begins
in one segment and ends in another; the funnel is in the
back part of the segment and the tube from it soon passes
through the partition behind it, the bulk of the tube lying
in the segment posterior to the one in which it began.
These tubes absorb waste matter from the liquid of the
body cavity, and convey it to the outside.

The Nervous System of the Earthworm. — This is a chain
of nerve centers or ganglions along the ventral part of the
body cavity, lying under the intestine. In each segment is
a ganglion, and these are connected by a nerve cord run-
ning lengthwise. Though apparently single, the nerve cord
and chain are really double, the two ganglions and cords
being so closely applied and fused that they appear as one.
The shortness of the segments brings the successive gan-
gHons so near together that they are not very distinct. In
the anterior region the double nature of the cord is appar-
ent. Under the anterior part of the pharynx the two strands
of the cord separate, one passing up on each side of the
pharynx to a large ganglion, the two gangHons lying closely
side by side, forming the "brain." Thus a ring is formed
around the pharynx, which is called the " nerve ring " or
"esophageal collar." From all the ganglions nerves pro-
c'eed to the surrounding organs.

i

Annulata. 97

The Senses of the Earthworm. — The sense of touch is
undoubtedly most fully developed, and on this sense the
worm largely depends for its knowledge of the outer
world.

The sense of taste exists, and probably smell also, for
the earthworm exercises choice of various foods offered it,
as shown in many experiments made by Darwin.

The earthworm can distinguish between light and dark-
ness, as evidenced by the fact that it retires to its burrow
at the approach of day. When a strong light is flashed
upon the anterior end of the earthworm, it retreats. The
posterior end is also sensitive to light. But there is no
reason for supposing that the worm sees objects with any
distinctness, as do animals with well-developed eyes. There
is no evidence of a sense of hearing.

Development of the Earthworm. — The ovaries are small
and close to the ventral surface, usually in the thirteenth
segment. The oviducts open on the fourteenth segment.
The eggs are inclosed in capsules of albuminous material
formed by the girdle, or clitellum. In May and June the
capsules containing the eggs of one species are deposited
in the earth under logs and stones, or especially in, or
under, manure heaps. The little worms are about an inch
long when hatched.

Enemies of the Earthworm. — The principal enemies of the earth-
worm are moles and birds. To escape the latter the worms usually
retire into their holes at the approach of day, often plugging the mouth
of the hole with pebbles. If they are too slow in hiding, or neglect to
shut the door, the sharp eyes of the bird may discover them. The
early bird gets the late worm.

Distribution of Earthworms. — Earthworms are very widely dis-
tributed, being found nearly all over the world, even in isolated islands
of the ocean. There are many species, but they are all much alike in
most features which are essential for our present knowledge.

98 Descriptive Zoology.

Effect of Earthworms on the Soil. — Darwin says that in all regions
where there is found a smooth expanse of vegetable mold, which is
the substance of all black soils, this mold has passed and will pass
again, every few years, through the bodies of earthworms. Before the
observations and experiments of Darwin the world hardly dreamed
what an important part earthworms have played in making the soil what
it is, but some previous observers had an inkling of it. The quality
of the soil is altered by the digestive process. It is worked over, and
the deeper layers are brought to and deposited upon the surface. This
inversion of the soil is essentially the same as that of plowing, so, as
Thomson says, earthworms were plowers before the plow. The holes
also aid circulation of air and water in the soil. To get a clear idea of
the effects of these worms on the soil, the student should read Darwin's
Vegetable Mould and Earthworms.

Number of Earthworms and Extent of their Work. — Darwin esti-
mated that in the tillable soil of England there were, on the average, over
fifty thousand earthworms to the acre ; that they bring up eighteen tons
of soil to the acre ; that they cover the surface at the rate of an inch in
five years ; and that thus in long ages they have buried large rocks and
ancient buildings. And his conclusion is that "it may be doubted
whether there are many other animals which have played so important
a part in the history of the world as have these lowly organized ani-
mals." In the United States earthworms are not so numerous.

Harm done by Earthworms. — Earthworms do some harm by eating
tender seedlings and delicate roots, but this is trifling in amount as
compared with the very great aid they render to agriculture.

Repetition of Parts. — If a person had grown up without having seen
an earthworm, at first sight of one he would probably be impressed with
its sameness of structure, nearly all the rings or segments having the
same general appearance. Dissection shows that the internal structure
is not so very different, the anterior portion having somewhat of a
variety in the development of the parts of the digestive, circulatory, and
reproductive organs. Back of the middle of the body there is no seg-
ment which adds anything new in function to the body, each segment
being simply a repetition of what precedes. As a rule, multiplicity of
parts, without corresponding variety of structure and function, marks an
animal as low in rank.

Recovery after Mutilation. — When an earthworm is cut in two in the
middle, the .anterior end probably lives in most cases, as it has all the

Annulata.

99

kinds of parts or organs that the earthworm possesses ; it has simply
lost a part of the intestine, nerve cord, blood tubes, etc., but not all of
any one set of organs.

Color of the Earthworm. — The color of the earthworm is largely due
to the color of the blood and to the matter contained within the diges-
tive tube. But besides this, the dorsal surface is darker than the ven-
tral, as is the case with most animals.

The Sandworm. — One of the commonest of the sea
worms (Nereis) is known as the sandworm or clam worm.
It is cylindric, bluish green, and from six inches to a foot

Fig. 6i, A Marine Worm.

A, appearance at breeding season, and B, at other times.
From Jordan and Heath's Animal Forms.

long. It is abundant along the Atlantic coast, and is an
excellent type lo study, especially when the earthworm
cannot be readily obtained. One can usually find them at
low tide along the sandy or muddy beaches. They make
burrows in the sand, but they are to be found at night,
swimming freely, especially during the breeding season.

One of the first points of difference between Nereis and
the earthworm is that Nereis has a distinct head. On the
top of the head are two pairs of eyes. There are also sev-
eral pairs of antennae and a pair of palps. Back of the

lOO Descriptive Zoology,

head the segments are all alike. On each side of every
segment are muscular projections, called parapodia; each
parapodium has several lobes, and these lobes are provided
with bundles of bristles, capable of extension and retrac-
tion, and also of being turned in different directions, as in
the case of the bristles of the earthworm. By means of
the parapodia and bristles the sandworm can crawl, and it
also swims by the same means. In the middle region of
the body the parapodia serve as gills, and the blood flowing
m the thin projections gives them a red color.

The internal structure, in the main, is very much like
that of the earthworm. The pharynx is muscular, and is
everted in seizing food ; but the sandworm has a pair of
strong, hard, horny teeth, with which it can grasp and kill
other worms and small animals that it eats. It also con-
sumes vegetable food. It is itself a favorite morsel for
many kinds of fish, and hence is much used by fishermen
as bait.

The Leech. — Leeches are usually flattened. They have no spines
nor appendages of any sort. There are from one to five pairs of eyes
on the anterior segments. The body appears to have many segments,
but dissection shows that many of these grooves are mere external
wrinkles, there being but one partition for from three to five of the con-
strictions. There is always a sucker at the posterior end, and in some
leeches one at the anterior end also, as in the well-known medical leech
of Europe, formerly much used in bloodletting. The mouth has three
radiating jaws, each bearing many fine teeth on its edge. The jaws are
acted on by muscles which work them back and forth like a semicir-
cular saw. The blood thus obtained is sucked into a crop, which
makes up the principal part of the digestive tube. The crop has several
pairs of side pouches in which the blood is stored, and it is said that the
leech can take enough at one meal to last a year. The blood does not
coagulate in the crop, and this is said to be due to the action of the
saliva. Digestion is accomplished in the narrow stomach posterior to
5;ne crop. A short intestine succeeds the stomach. Leeches have three

Annulata. loi

modes of locomotion : {a) they creep along with a gliding movement
like a snail ; (d) they swim by a graceful undulatory motion ; (c) they
travel by a " looping " action, somewhat as in " measuring worms,"
holding on alternately by the anterior and posterior suckers, some
leeches thus progressing actively.

Other Annulate Worms. — There are many annulate worms, mostly
marine. Some are free-swimming, while others live in tubes which
they form of mud, sand, or limestone. Many of them have beautiful,
feathery gills, sometimes distributed along the body, but in the tube-
inhabiting forms more frequently at the head end. Many sea worms
are phosphorescent, emitting a vivid green light.

CHARACTERISTICS OF ANNULATA.

1. The body is bilaterally symmetrical; there are also
distinct anterior and posterior ends, and dorsal and ventral
surfaces.

2. The body is segmented (except Gephyrea).

3. There is a distinct body cavity, divided by partitions
into as many compartments as there are segments.

4. There is a well-developed blood-tube system for the
circulation of blood.

5. A nervous system is present, consisting of cerebral
ganglions, esophageal collar, and ventral nerve cord.

6. There are tubular kidneys in each segment.

Classes of Annulata.

{I. Oligochaeta (few bristles — earth"
worm) .
2. Polychaeta (many bristles — Nereis),
Annulata. -{ Class 2. Gephyrea.

Class 3, Archi-annelida.

Class 4. Hirudinea — the leeches.

CHAPTER VII.

BRANCH MOLLUSCA.

The branch Mollusca includes clams, oysters, scallops,
snails, slugs, squids, and cuttlefishes. The large majority
of mollusks have shells. The shells have always been
objects of great interest on account of their beauty of
color, delicacy of texture, and variety of form. Their
durability and the ease with which a collection may be
made and kept have further contributed to making the
mollusks a favorite subject of study.

CLASS PELECYPODA.
Example. — The Fresh-water Clam.

"Where Clams Live. — Clams live in creeks and ponds,
lakes and rivers. They are usually less abundant in the
smaller streams, as these may become dry in midsummer.
The natural position of the clam is shown in Fig. 64.

External Features of the Clam. — The clam shell is com-
posed of two equal valves, fastened together at the dorsal
margin by a tough, elastic membrane, the hinge ligament.
Somewhat nearer the anterior than the posterior end
is a raised point close to the dorsal margin; this is the
umbo ; it is frequently more or less worn or broken away,
which is not surprising, as it is the oldest part of the shell
and is subject to friction as the clam plows along through
the sand. Around this are the concentric lines of growth,
running parallel to the ventral margin. Different species

102

Pelecypoda.

103

of clams are distinguished by the size and shape of the
shell, the relative proportions of the parts, the color mark-
ings, smoothness or roughness of the shell, the thickness
of the shell, and by the hinge teeth on the interior.

Umbo

Dorsal margin
Hinge ligament

Fig. 62.

Line ot growth
Ventral margin

External Features of a Clam Shell.

Outside of left valve.

The Inside of the Clam Shell. — After the soft parts are
removed, the following internal markings are usually plainly
seen. The scars are the places of attachment of the mus-
cles, of which the most notable are the anterior and poste-
rior adductor muscle scars. Just below and posterior to the
anterior adductor scar is the scar of the protractor of the
foot. Above the anterior adductor scar is the scar of
the anterior retractor of the foot. Just above and anterior
to the posterior adductor scar is the scar of the poste-
rior retractor of the foot. There are also a few small scars
of muscles in the dorsal regions. In removing the boay of

I04 Descriptive Zoology.

the clam, it will be found that the mantle has several mus-
cular attachments. Running parallel to and not far from
the ventral margin is the mantle line, the line of attachment
of the inner edge of the muscular portion of the mantle.

Anterior
adductor
muscle

Lateral hinge teeth
Cardinal |

hinge
teeth

Mantle line

Fig. 63. Inside of Right Valve of Clam Shell.

The Hinge Teeth. — In most species of fresh-water clams
there are interlocking projections near the dorsal margin
of the valves. Near the anterior adductor are strong,
toothlike projections, the anterior, or cardinal, hinge teeth.
Parallel to the dorsal margin, near the hinge ligament, are
long ridges, the lateral or hinge teeth ; there are usually
two of these on one valve and one on the other, which fit
together when the shell is closed. These teeth aid in
keeping the shell shut.

The Natural Position of the Clam. — The ventral margin
is imbedded in the mud or sand, the anterior end usually
considerably deeper than the posterior. This position
brings the siphon openings above the mud ; but at

Pelecypoda.

105

times the whole shell is buried in the soil ; this seems
to be the case more often in the winter, when the clam
is less active, or after freshets which cover the clams with
mud.

The Clam at Home. — By watching the clam in its natural
habitat the position, as above described, may be observed.
It may be seen that the shell is slightly agape ; that a soft
membrane protrudes from the opened edges of the shell ;
that at the posterior end are two elliptical openings. It
may be proved that a current of water is entering one of
these openings and issuing from the other. If the borders

Excurrent
Siphon

Fig. 64. Clam in Natural Position.

With foot and siphons extended.

of these openings are touched, the soft membrane forming
the margins of the openings is withdrawn into the shell,
and the shell is tightly closed. If a clam, previously un-
disturbed, be quickly pulled out of the mud, a soft, fleshy

io6 Descriptive Zoology.

projection, the foot, is found extending from the anterior
ventral margin ; but this will be at once, though not rapidly,
retracted, and the shell securely shut.

The Enemies of the Clam. — The question naturally arises,
" Why does the clam need such a strong protective cover-
ing ? '* The working parts of the body are soft, the Latin
word mollis giving the name to the whole branch — Mol-
lusca. Such a soft-bodied animal would naturally be the
prey of carnivorous animals. And further, since the clam
is slow in movement and has few and poorly developed
senses by means of which to become aware of the presence
of enemies, it is not surprising that it should be thus
securely protected. Among his most dangerous foes are
the raccoon, otter, mink, and muskrat, and probably other
mammals that frequent the water or prowl along the banks
of our streams. Muskrats open the shell by first gnawing
off the hinge, after which it is comparatively easy to open
the shell. Against its enemies the clam has, apparently,
but the one means of defense, namely, to shut the shell as
strongly as possible and to keep it shut till the coast is
clear. Man, whether gathering specimens for study, seek-
ing pearls, or gathering the shells for buttons, is to be reck-
oned among the clam's enemies.

How the Clam opens and shuts its Shell. — Two large
cylindrical muscles pass directly across the body of the
clam, connecting the two valves. One of these muscles is
at the anterior end, the anterior adductor muscle, and the
other, the posterior adductor muscle, is at the posterior
end. The ends of these muscles are strongly attached to
the inside of the shell. When they shorten they bring the
two valves together and hold them with great force.

For an inch or so along the dorsal margin the two valves
are held together by the elastic hinge ligament, which is

Pelecypoda.

107

merely an uncalcified portion of the shell. When the mus-
cles pull the valves together, this ligament is stretched.
Consequently, as soon as the adductor muscles relax, the
elasticity of the hinge ligament opens the shell. It will be
observed that the shell is shut by muscular effort, whereas
it is opened by the mechanical action of a spring, which
consists of practically dead tissue. It requires no effort to

Hinge Ligament
External

Hinge Ligament
Internal

Fig. 65. Mechanism for opening and shutting a Clam Shell.

keep the shell open. As the shell is partially open most
of the time, the economy of this arrangement is apparent.
Why would it not do as well to have the shell opened by
muscular action and closed by a spring ? In some bivalve
mollusks the hinge ligament is internal, so that when the
shell is shut the ligament is compressed, instead of
stretched, as in these clams. Then, when the muscles
relax, the shell is opened by the expansive elasticity of the
ligament. The general principle is the same, but is carried
out in a different way. See Fig. 65.

io8 Descriptive Zoology.

Why the Clam opens and shuts its Shell. — It is only by
opening the shell that the clam is able to place itself in
communication with the outside world. The opening allows
the foot and siphons to be protruded. When disturbed, the
clam withdraws the foot and the siphons, and completely
closes the shell, and usually remains in this condition until
the disturbance ceases. The muscles are of the slow-acting,
non-striped kind, and can remain shortened a long time ;
but they evidently get tired, and after a while they relax,
and the shell gapes open.

The Location of the Siphons. — Since the clam pulls itself
forward by the foot, which it imbeds in the mud, the foot
naturally extends forward and downward. As a good share
of the ventral part of the shell is below the level of the sand
or mud, the only available place to take in clear, fresh water
is at the upper and posterior border. And here we find
the siphons.

How the Clam Progresses. — The foot is slowly extended
forward and downward into the mud. When it has become
well imbedded in the rnud, if the clam wishes to move for-
ward, it shortens the muscles of the foot and body, and thus
pulls forward the body, shell and all. Then another inter-
val must elapse until the foot is again anchored before an-
other move can be made. In this way the clam slowly
plows its way along, leaving a distinct furrow by which
it may be traced in clear water. The protruding of the foot
is a slow process, while the act of pulling forward is of com-
paratively short duration. It is stated that the extension of
the foot is mainly due to an inflow of blood which is kept
frojn.jreturning by a tightening of the sphincter muscles
around the veins. At any rate, the foot is often found
dilated toward the extremity, which plainly increases its
efficiency as an anchor.

Pelecypoda. 109

Extent of the Clam's Locomotion. — The clam does not
travel far. Since it brings its food in by the currents of
water which it creates, it does not have to move about for
food. When the water gets low, as in most creeks in the
summer time, the clam apparently seeks the deeper water.
The question naturally arises, ''How does the clam become
aware of this change, and how does it know in what direc-
tion to go .? "

The Clam's Muscles and their Functions. — There are five
chief muscles : —

1. Anterior adductor. > ^, ^, , ,, See Figs. 63
^ . , , > Close the shell. , °

2. Posterior adductor. > and 65.

3. Protractor — pulls the foot and body forward and
downward. '

4. Anterior retractor — pulls foot and body upward and
backward.

5. Posterior retractor — pulls foot and body upward and
backward.

When the foot is imbedded in the sand or mud, the
shortening of the retractors, whose fibers spread over the
body and foot, pull the shell forward instead of retracting
the foot.

Structure of the Clam Shell. — If a shell is roasted thor-
oughly, its structure may more easily be learned. The first
fact to be noted is that the shell consists of layers ; the
next, that these layers are in two sets, the dividing plane
between which starts from the mantle line and extends
toward the umbo. The shell is an outgrowth of the outer
layer, or epidermis, of the mantle. But the layers of the
shell made by the part of the mantle outside of the mantle
line are not directly continuous with the layers formed by
that part of the mantle which is dorsal to the mantle line.
The mantle Hne is really a row of small muscle scars where

no Descriptive Zoology.

the muscular border of the mantle is attached to the shell.
The edge of the mantle, it was observed, is attached to the
edge of the shell. The outermost layer of the shell, the

Umbo

Fig. 66. Structure of Clam Shell.

Cross section.

periostracum, is formed by the edge of the mantle, and is
horny in composition. Inside this is the prismatic layer,
and innermost is the laminated pearly layer.

Growth of the Clam Shell. ^ — The successive concentric
lines of growth seen on the outside of the shell mark the
growth, each line of growth having once been the ventral
edge of the shell. The layers are formed by the mantle,
and each new layer is a little wider and longer than the one
preceding, and outside of it. The muscles grow and gradu-
ally move outward, hence the muscle scar continually widens,
forming a triangle. But as the muscles move on, the scar
of former years is covered by the new layers formed by the
mantle.

Uses of the Clam Shell. — The fresh-water clams are little
used as food, but their shells are used largely in making
buttons. This is an industry of considerable extent along
the Mississippi River and some of its tributaries.

Respiration in the Clam. — The current of water which
we saw entering and leaving the clam brings Dxygen as well

Pelecypoda.

Ill

as food. The blood circulates in the walls of the gills, and
thus the water current and the blood current are brought
very close to each other. Oxygen passes from the water
into the blood ; and from the blood, carbon dioxid and other
waste matters pass into the water through the thin layer of
the wall of the gill surrounding the blood tubes. There is
also an active circulation of blood in the mantle, and a con-
siderable share of the work of respiration is undoubtedly
accomplished here.

The Structure of the Gills. — Each gill has the appearance
of a thin, single-layered membrane ; but in reality each gill

Artery

Anterior adduc-
tor muscle

Auricle Ventricle
1 i

Posterior adductor
muscle

Fig. 67. Body of Clam.

Left valve removed.

is double walled, and a cross section is like a letter V.
Each gill is a long, narrow, V-shaped pocket or trough,
though divided into many compartments by cross partitions.
The two gills of each side are united so as to form, in cross
section, a W, the upper margin of the outer wall of the
outer gill being attached to the mantle, the upper edge of

112 Descriptive Zoology.

the inner wall of the outer gill joining the upper edge of the
outer wall of the inner gill, while the upper edge of the inner
wall of the inner gill is sometimes attached to the body or
sometimes free. Back of the body the upper edges of the
inner gills of the two sides unite with each other, thus sepa-
rating the lower, or gill, cavity, into which the water first

Fig. 68. Clam, Side View.

Water currents to the mouth and through the gills.

enters, through the lower incurrent siphon, from the upper,
or cloacal, chamber, from which the water passes out. The
question presents itself, •' How does the water pass from
the one cavity into the other ? "

The sides of the gills are perforated, so much so that they
are compared to a sieve or trelliswork. The vibrations of
the myriads of cilia with which the gills are covered drive

Pelecypoda.

"3

the water that lies outside of the gill through these openings
into the space within the gill. The water then passes up
through the open top of the gill into the cloacal chamber,
and back out of the excurrent siphon. The four gills are
so many narrow, V-shaped troughs with their sides full of
holes. Instead of filHng at the top and leaking out at the
holes in the sides, these troughs are filled through the holes

Ventricle Intestine

Auricle

Cross section through heart. Cross section through posterior adductor muscles.
Section at /I. Section at 5.

Fig. 69. Clam,

Water currents through the gills. Compare with Figs. 68 and 71.

in the sides, and overflow above, — only the water cannot
run down the sides of the trough, but must pass back and
out through the upper siphon. (Figs. 68, 69, and 70.)

The Food of the Clam, and how Obtained. — The clam
lives on microscopic plants and animals and on minute par-
ticles of organic matter. This material is supplied by the
current of water which is continually passing into the lower

114

Descriptive Zoology.

and out of the upper siphon. The current is produced by
the vibration of the ciUa which cover the outside of the gills
and the inner surface of the mantle. The entering current
passes forward around the body and gills. The palps are
also ciliated ; and between the two palps of each side the
minute particles are caught and passed on into the mouth,

Blood tubes

Blood currents

Water holes

Fig. 70. Structure of Clam's Gill.

whose upper lip is formed by a continuation of the two
outer palps meeting across the middle line, the two inner
palps similarly forming a lower lip.

The Digestive System of the Clam. — The mouth is just
back of the anterior adductor muscle. A short, wide
gullet extends upward and backward to the large spherical

Pelecypoda.

"S

stomach. On each side of the stomach is a large, greenish,
digestive gland, often called the liver, whose secretion
passes into the stomach. From the stomach the intestine
passes downward and backward, making one or two coils
in the abdomen and foot, then passes upward back of the
stomach, near the dorsal margin ; it then turns posteriorly,
parallel to the dorsal margin, passes through the ventricle

Digestive
gland

Anus

— ~ — ■ — intestine

Fig. 71. Digestive and Excretory Organs of a Clam

of the heart, over the posterior adductor muscle, just back
of which it ends, thus discharging the refuse of digestion
where the outgoing current of water will catch it and
sweep it out of the body through the dorsal siphon. The
digestive tube is hard to trace in a fresh specimen, less
difficult in one which has been boiled or hardened in
alcohol. The whole tube may be injected with a colored
starch injection and thus readily followed. In the fall
the intestine is often found to contain a cylindrical body of

Il6 Descriptive Zoology.

clear material having the consistency of a gumdrop. This
is the ** crystalline rod," and is thought by some to be a
store of food material. Others regard it as a secretion to
protect the lining of the intestine from injury.

The Circulatory System of the Clam. — From the gills
and mantle of each side the blood passes up into the cor-
responding auricle (Figs. 67 and 69). The auricles, are
wide at the base, where they arise from the upper margins
of the gills, but narrow as they approach the ventricle, so
that the lateral view gives a triangular appearance. The
auricles are thin-walled, delicate structures. They open
into the sides of the median ventricle. From the ventricle
arise two arteries, one carrying blood forward above the
intestine, the other extending backward beneath the intes-
tine (Fig. ^y^ After leaving the arteries, the blood
passes into irregular and ill-defined channels, supplying all
parts except the shell. The blood collects in a caval vein
under the floor of the pericardium, then passes through
the kidneys, and to the gills once more. In the gills and
mantle the blood loses carbon dioxid and gains oxygen.
As it passes through the kidneys it loses nitrogenous waste
matter, and from the digestive tube it absorbs new food
material for the support of the life processes.

The Kidneys. — The kidneys are ill-defined, dark-colored
organs, lying just beneath the floor of the pericardium and
in front of the posterior adductor muscle. Each kidney
consists of a tube doubled on itself, the bend being near
the adductor muscle. One end of the tube communicates
with the bottom of the anterior part of the pericardium,
the other end opens on the side of the abdomen, near the
upper edge of the inner wall of the inner gill, and above
the tip of the corresponding palp. Here the excretion
is poured out, and is carried away by the water current.

Pelecypoda.

117

Nervcus System of the Clam. — There are three pairs
of gangUons, which are connected by nerve trunks, called
commissures : —

1. The cerebral ganghons, one on each side of the
mouth, just above the outer palp of each side; these are
connected by a nerve cord which passes over the gullet.

2. The two pedal ganghons, lying closely side by side,
deeply imbedded in muscle, near the middle of the foot.
Each of these is connected with the cerebro-pleural gan-
gHon of its side.

Gullet

Visceral
Ganglions

Fig. 72. Clam, Nervous System.

3. On the under surface of the posterior adductor are
the two visceral ganglions, apparently forming one double
ganglion. These ganglions are much easier to find than
the others. Each of these is connected with the cerebral
ganghon of its side by a nerve cord, which runs along in
the dorsal part of the body for a good share of its length.
From all of these ganghons nerves extend to supply the
adjacent regions.

Xi8 Descriptive Zoology.

The Sense Organs. — The sense of touch is preeminent.
This sense is best developed in the palps, along the margin
of the mantle, especially that part of it which forms the
borders of the siphons, and in the foot. There is no
sense of sight, but the tentacles around the siphons seem
somewhat sensitive to light. On a nerve near the pedal
ganglion is the so-called **ear sac," of doubtful use. At
the base of the gills is an organ sometimes called the
"smelling patch," which, perhaps, has the office of testing
the quaUty of the water. The sense of taste is doubtful,
though it is probable that there is some discrimination as
to what should be taken as food. The clam is sensitive
to vibrations communicated either through the soil or the
water.

The Reproductive Organs. — These are diffuse glands
enveloping the coils of the intestine in the abdomen. The
glands in the two sexes (ovaries and spermaries) are so
similar that it usually requires microscopic examination to
distinguish them. The ducts, both in the male and female,
open on the side of the body near the opening of the duct
from the kidneys. The eggs, when mature, pass out of
the duct and lodge in the gills (more often the outer gills)
of the female. They are fertilized by the sperms, which
have been set free in the water and are drawn in by the
same current that brings the food particles. The males
and females may sometimes be distinguished by the greater
convexity of the shell in the female, the valves being more
bulging to accommodate the accumulation of eggs and
young clams in the outer gill.

Development of the Clam. — The young usually develop
during the fall and winter. When liberated, the young
clams are called Glochidia. They are of different shape
from the adult, being ovate, with the hinge at the wider

Pelecypoda. 119

end. There is but one adductor muscle ; the foot is yet
undeveloped, but from the foot region project long threads,
the " byssus," by which it becomes attached. At the tip
of each valve there is an incurved hook by which the little
clam usually catches hold of the fin or gill of a fish,
whereby it is protected from enemies and kept in fresh
water. Soon after it thus becomes attached it is covered
by a growth of the skin (a diseased growth) which still

Fig. 73. Young Clam, still within the Egg Membrane.

m, adductor muscle ; /, hooks by which it attaches itself to the gills or fins of fishes ; 6, byssus j

s, sense organs. 'j

further protects the parasite. When sufficiently mature,
the young clam drops off, soon becomes like the adult in
form, and shifts for itself.

Salt-water Clams. — Although several kinds of marine
clams are used as food, there are two that are more largely
eaten in this country. One is Venus mercenaria, found
from Texas to Cape Cod, but rare north of that point ; the
other Mya arenaria, found generally along the coasts of
the Eastern states, but rather distinctively more Northern
than the other. So when Massachusetts people speak of
clams they mean the Mya, commonly designated elsewhere
as the ''soft clam," ** soft-shelled clam," "long-necked
clam," or "long clam." Whereas, when New Yorkers
mention clams, without any qualifying adjective, they have

I20

Descriptive Zoology.

in mind Venus mercenaria^ which, farther north, and away
from the coast, would be designated as the " hard clam,"
'round clam," or "quahog." Both are frequently found
in the markets inland.

The Soft-shell Clam. —This clam
lives in a vertical burrow with the
anterior end down. Instead of
having short siphons like the fresh
water clam, the posterior margins
of the mantle lobes are extended
and grown together to form a long
double tube, which reaches to the
surface of the sand or mud, the body
being sometimes a foot from the
surface. The two mantle lobes are
united along their entire edges,
except at the two siphon apertures
and an anterior opening, for the
projection of the foot. The ventral
channel is the incurrent and the
smaller dorsal one the excurrent.
As in the clam we have studied,
the incurrent siphon has a fringed
margin and is very sensitive. The
border is also dark colored, so that
it is not readily seen, and if disturbed
it is withdrawn into the hole. At
low tide the tube is generally so re
tracted. At this time clams are
hunted and dug up.

As the clam grows, it deepens and
widens its burrow. The foot is small, and the old clam, dug
up and left on the surface, has difficulty in making a new

Fig. 74. Long Clam, BURIED
IN THE Mud.

The arrows show the currents in
the siphons.

From Kingsley's Zoology.

Pelecypoda. I2i

burrow. The internal structure is essentially the same as in
the fresh-water clam. To accommodate the long siphon
tube when it is retracted, there is a deep indentation of the
mantle line in the posterior region. The shell of Mya can-
not be snugly closed, there being a gap both anteriorly and
posteriorly. Probably this may be accounted for by the
more protected position and the need of having the siphon

Fig. 75. Hard Clam; Round Clam; Quahog.

With foot, siphons, and edge of mantle extended.

tube extended most of the time. The siphon tube, with its
black tip, is commonly called the " head," but this clam is
as headless as its fresh-water relative.

The Hard Clam. — The hard clam, or quahog, is also an
important sea-coast food, especially where the soft clam
is not obtainable. It is oval, with a thick shell. It bur-
rows but a short distance, hence the siphons are not long,
and the two tubes are partly separated. The foot is well
developed, and the clam crawls more or less like the fresh-

122 Descriptive Zoology.

water clam. These clams may be picked up at low tide,
but are ordinarily taken by means of long rakes or tongs.
The smaller or medium-sized ones are preferred. The
border of the inner surface of the shell is usually purplish,
and this part was made into the beads which constituted
the more valuable purple wampum of the Indians of New
England.

The Oyster. — One essential difference between the
oyster and the clam is that the oyster is stationary,
being firmly attached by one valve to some solid object,
a rock, or another oyster so attached. The oyster lies on
the left side, and the lower valve is much more concave
than the upper, which is nearly flat, serving as a lid. As
the oyster does not travel, it needs no foot and has none,
hence is less tough than the clam. The hinge is at the
pointed end of the shell, and the two mantle lobes are free
from each other, except near the hinge. There are no
siphons, the water entering all along the more curved bor-
der of the shell and passing out on the straighter side near
the larger end of the shell. The water is propelled by cilia
and passes through the gills as in the clam. There is but
one adductor muscle.

Development of the Oyster. — The eggs and young are
not carried nor protected as in the clam, but the eggs are
fertilized after being set free in the water. The egg
becomes many-celled by the growth and repeated division
of the one cell which constituted the egg. This becomes
ciliated and swims by means of these cilia. After a few
days of this free swimming life, during which time the
shell and other organs are gradually developing, the little
oyster attaches itself by its left valve to some submerged
object, to which it becomes firmly cemented by the deposit
of limy material which makes the hard part of the shell.

Pelecypoda. 1 23

Comparison of Clam and Oyster. — It will be noticed that
the hinge in the oyster is at one end of the shell. This
end corresponds to the anterior end of the clam. The
oyster shell can open but sHghtly. The shells are rougher
than those of clams. The green spot in the oyster is the
digestive gland (often improperly called the liver), and
not the digestive tube or its contents, as commonly sup-
posed. Oysters and other salt-water m.ollusks are often
left above water at low tide.

Distribution of Oysters. — Oysters are abundant along
the Atlantic coast, south of Cape Cod, and in the Gulf of
Mexico. In former times they occurred north of Cape
Cod, but are now rare. Other species are found on the
Pacific coasts and on the coasts of Europe, at the Cape of
Good Hope, in Japan, and Australia. Chesapeake Bay is
the center of the oyster industry, and the British market
is now largely supplied from our beds, as we have not only
the most abundant supply, but ours are the best in the
world.

The Oyster Season. — The common saying that oysters
are good only in months containing the letter "r," is partly
wrong and partly right. Oysters are good to eat at any
time of the year when freshly taken from the water. But
during their breeding season — June to August — they do
not bear handhng so well, and are more likely to spoil.
It is more profitable, too, to leave them undisturbed at this
time, that they may increase enough to maintain their
numbers.

The Shipworm. — As the name implies, this mollusk is wormlike.
It sometimes becomes ten inches long and half an inch thick. It bears
a small bivalve shell at its larger end. It burrows in wood, doing great
damage to ship timbers, buoys, wharves, etc. The first stages of devel-
opment are like those of many other bivalves. If the larva cannot find

124

Descriptive Zoology.

wood, it soon dies. The hole by which the larva enters the wood is
hardly larger than a pin head, but as the animal grows it excavates a
constantly widening tube, thus imprisoning itself for life. Just how it
burrows is not certainly known. It does not feed upon the wood, the
fine sawdust being carried off through the excurrent siphon. Its food
consists of microscopic plants and animals, which are brought in by

Fig. 76. Razor Shell Clam.

currents, as in the clam, and its only communication with the outer
world is through the small hole by which it first entered the wood.
Shipworms work rapidly, often completely honeycombing the wood.
But no matter how many of them there are in the wood, their tubes
never interfere with one another, but there is always left a thin partition
between. They avoid iron rust, so timbers are protected by driving
them thickly with broad-headed nails. The copper sheathing of hulls
of ships is the best protection. Shipworms caused the famous dam
break in Holland at the beginning of the last century.

The Razor Shell Clam. — The razor shell clam has a shell somewhat
resembling in shape and size the handle of a razor. The foot projects

at the anterior end, the siphons
at the posterior end. These
clams make vertical holes in
the sand and can dig rapidly.
At low tide the posterior end
may be seen projecting from
the sand, but unless the col-
lector approaches quietly and
seizes the clam quickly, it is
almost sure to escape. They
seem to be very sensitive to
vibrations, and probably be-
come aware of approach through these rather than through hearing or
sight, although they are somewhat sensitive to light.

The Salt-water Mussel. — One of the most common marine bivalves
is the mussel. The shell is usually dark or purplish, and rather thin

Fig. 77. Mussel.

With threads by which it is attached.

Pelecypoda. 125

and weak. The mussel is found attached to rocks by means of a num-
ber of yellowish threads, the byssus, which grow from the base of the
small foot. Mussels are found widely distributed along the coasts in
most seas. They are used to a considerable extent as food in some
countries.

The Giant Clam. — Probably the largest bivalve known is a marine
clam of the genus Tridacna, found in Eastern seas. The soft body
sometimes weighs twenty pounds, and the two valves of the shell
together may weigh five hundred pounds.

The Scallop. — The outline of the shell as seen from one side is
Qearly circular. The two valves are not equal, one being less convex

Fig. 78. Scallop.

The crusaders' badge.

than the other, sometimes perfectly flat. While at rest the scallop lies
on the bottom with its valves widely gaped open. The scallop has a
row of eyes along the margin of each mantle lobe. When an enemy
approaches, the shell is quickly and powerfully shut by the one strong
adductor muscle. This forcibly ejects the water, and by reaction the
scallop is driven through the water, hinge foremost. The foot is rudi-
mentary or lacking. The scallop is used for food ; the adductor muscle,

126 Descriptive Zoology.

however, is the only part eaten. It has a sweetish taste. The scallop
shell was worn as a badge by the crusaders, as evidence of having
visited the Holy Land.

Pearls. — These are formed of nacre, the material which constitutes
the inner layer of the shell. They begin as deposits around grains of
sand or other foreign objects that have gained entrance within the shell.
They are usually found between the mantle and the shell, but may be
in almost any of the soft parts. It is said that the Chinese introduce
little images into the cavity of the pearl oyster, leaving them to become
coated over with nacre. The most valuable pearls are usually obtained
from the pearl oyster, but they are often found in certain species of
fresh-water clams. The most celebrated pearl fisheries are in the
Persian Gulf.

Characteristics of the Bivalve MoUusks. — The clam and
most of the other bivalve mollusks have the following
characteristics, and have received various names, accord-
ing as any given writer places special emphasis on one
characteristic or another : —

1. There is no head; hence some designate the group
Acephala.

2. There are large, leafiike gills, from which comes the
name Lamellibranchiata.

3. There is usually a muscular, tongue-shaped or hatchet-
shaped foot, giving rise to the term Pelecypoda.

4. The mantle consists of two lobes, each lobe lining
a valve ; hence they are called Bivalve Mollusks.

CHAPTER VIII.

Apex

BRANCH MOLLUSCA.

CLASS GASTROPODA.

The gastropods include the snails and slugs. They are
of many kinds, terrestrial and aquatic, in fresh water and in
salt water, shelled and shell-less, symmetrical and unsym-
metrical, herbivorous and carnivorous.

The Shell. — The shells of gastropods are usually of one
piece, therefore they are often called univalves in distinc-
tion from the bivalves.
This one-pieced shell is
almost always in the
form of a goae. Some-
times the cone is nearly
straight, as in the tooth-
shells ; again it is in the
form of a very low, wide
cone, as in the limpets ;
but in the great majority
the cone is twisted into a
spiral, making a thick,,
short cone out of a long
and slender one. Some-
times this primary cone
is wound upon itself to form a plane spiral like a watch
spring, as in Planorbis. But ordinarily the spiral is an
ascending spiral, which may be illustrated by holding the
outer end of a watch spring and pushing the inner end out

127

Lip

. Aperture

Fig. 79. Parts of a Snail Shell.

128

Descriptive Zoology.

at right angles to the plane of the flat spiral. By pushing
out the center, first to the right and then to the left, we may
illustrate both the right-handed and the left-handed shells.
A very good substitute may be made by winding a narrow
strip of paper around a lead pencil at one end. This,
unwound, forms a flat spiral, representing the discoid shell.
By pushing the center, first to one side and then the other,
illustrate the right- and left-hand shells. Lay snail shells
alongside a common wood screw ; those having the whorls
run the same way as the threads of the screw are right-

Left-hand shell Flat spiral or Right-hand shell

Fig. 8o. Comparison of Kinds of Snail Shells.

hand shells ; those with the whorls twisting in the opposite
direction are left-hand shells.

The structure and composition of the shell are essentially
the same as in clams, the lines of growth usually showing
plainly parallel to the border of the lip.

The QpjerculuiP- — Nearly all sea snails, and many fresh-
water snails, have a trap door attached to the hinder part
of the foot, with which they close the aperture of the shell
when the body is drawn in. This covering is the opercu

Gastropoda.

129

lum, and grows by concentric rings to keep pace with the
continually widening aperture.

The Lingual Ribbon. — In the floor of the mouth is a rib-
bon-shaped membrane bearing on its upper surface many
rows of fine, sharp teeth. This ribbon passes over a pad of
cartilage, being pulled forth and back by muscles. It acti
like a rasp, wearing away the surfaces to which it is applied.
As it is worn away in front, it is pushed forward by a new
growth behind. In addition to the lingual ribbon, many

. Fig. 81. Fig. 82.

Three Species of Pond Snails.

In Figs. 82 and 83 the aperture is closed by an operculum,

Fig. 83.

mollusks of this group have also one or more jaw plates
in the mouth, against which the ribbon works.

The Foot. — The foot in the gastropods is broad and flat.
Resting upon this wide foot, the animal creeps or glides,
leaving behind a slimy trail of mucus^ which is abundantly
secreted. The foot is symmetrical, and the anterior end is
more or less distinctly marked off as the head.

The Digestive System. — The mouth opens on the front
or under surface of the head. Watch a snail in an aqua-
rium to see how the mouth works. From the mouth ex-
tends a short gullet, sometimes dilated into a crop, to the

I JO Descriptive Zoology.

stomach, which in turn is followed by the intestine. The
intestine is usually twisted around so as to end in the
mantle chamber near the edge of the aperture of the shell.
SaUvary glands are almost always present, and there is a
large digestive gland around the stomach, as in the clams.

The Circulatory System. — This is on essentially the same
plan as in clams. The blood comes from the gills, or lung,
to the heart, and is thence pumped to the other parts of the
body. There is usually but one auricle in place of two
found in the clam.

The Excretory System. — The gastropods have kidneys
essentially Hke those of clams, whose ducts open into the
mantle cavity. Owing to the one-sided development, usu-
ally only one kidney is retained.

The Nervous System. — The nervous system is primarily
about the same as that of the clam, consisting of several
pairs of ganglions connected by nerve cords. The twisting
of the body in many of the univalves involves the nervous
system so that the nerve loop becomes twisted into the
shape of a figure 8.

Sense Organs of Gastropods. — The eyes of the snail are
described below. It is doubtful how well a snail can see,
but it can discern light from darkness and can perceive
quick movements.

A sense of touch belongs to the whole surface of the
body, but is more acute in the tentacles. At the base of the
gills are organs called "osphradia," or "smelling patches,"
being perhaps organs for testing the quality of the water.
Land snails can detect odors, and the seat of the sense of
smell seems to be in the tentacles.

Respiration in Gastropods. — The majority of the gastro-
pods breathe by means of gills. Between the mantle and

Gastropoda. 131

the body, near the aperture of the shell, is a space called
the mantle cavity. In this space lie the gills, but in many
cases but one gill is developed.

Air-breathing Gastropods. — In land snails, slugs, and
numerous fresh-water snails, the mantle chamber becomes
more shut in, leaving a narrow opening, which is near the
right side in right-hand snails, and on the left in the left-
hand snails. Through this opening, which is kept closed
most of the time, air is taken into the cavity, which acts as a
lung. The blood circulates around the walls of the lung
cavity, and is thus brought close to the air, so that an inter-
change can take place between the two.

The Land Snails. — These are abundant in damp woods,
especially in limestone regions. Their shells are usually
thin. Land snails have two pairs of tentacles, with eyes at
the tips of the upper or longer pair. The eyes can be
pulled in, the tip disappearing first, as when in puUing off
a glove the tip of the glove finger sticks to the end of the
finger. If the tip of one of these tentacles is cut off, it will
be reproduced, and it is said that this has been done twenty
times in succession.

Land snails usually have no operculums ; but at the ap-
proach of winter, or of a period of drouth, they bury them-
selves in the ground, and pull the body in until the foot is
even with the edge of the aperture. A layer of mucus is
secreted which completely closes the aperture. In some
cases limy material is added, and, in any case, the covering
soon hardens. Sometimes the snail then withdraws still
farther, and makes another such barrier, or even several.
In the spring, or at the return of moisture, the temporary
door is cast off, and the snail resumes its activity. Snails
have great vitahty, and have been known to survive in this
shut-in condition for six years without food.

132 Descriptive Zoology.

Most kinds of snails lay their eggs in strings, masses, or
clusters ; but the land snails deposit theirs singly, burying
them or depositing them in moist places.

The French follow the usage of the Romans in eating
the land snails, and they are now imported into the United
States from Europe by Eastern dealers.

In Europe snails do considerable damage in gardens, but
they do not seriously affect us.

Slugs. — Slugs are air-breathing, terrestrial gastropods,
almost always destitute of a shell. They are to be found
In moist woods, especially under the bark or in the decaying
trunks of fallen trees.

On the anterior dorsal surface is a fleshy plate, the mantle,
and near the right edge of this is the breathing pore, lead-

Mantle

Fig. 84. Slu(;.

Near the lower border of the mantle is the respiratory pore.

ing to the lung. As in the land snail, there are two pairs
of tentacles, with eyes at the ends of the upper (longer)
pair. The body is elongated ; but when the animal is dis-
turbed, it draws up into a short, compact lump.

Slugs are nocturnal, hence are less conspicuous than
snails. They do considerable damage in gardens, rasping
off the surfaces of the leaves. Their presence is also in-
dicated by the slimy trails which they leave behind. One
,of the most effective ways of checking them is to sprinkle
coal ashes over and around the plants they are attacking.

Gastropoda.

^33

The Pond Snails. — The pond snails have the mantle
caYit}^ transformed into a lung, as in the land snails.
They frequently come to the surface of the water to get
air, and may be seen first to emit a bubble of the contained
air, take a new supply, and again descend to resume their

Fig. 85.

Fig. 86.

Pond Snails Creeping.

The largest part extending from the shell is the foot. There are three other protruding
organs: (1) the proboscis, in the center; (2) the two tentacles, with an eye at the base
of each; (3) outside the tentacles, the respiratory tubes, one of which takes in water, the
other sending it out. In Fig. 85, the dark semicircle back of the shell is the operculum.

eating. They are exclusively herbivorous, and in an aqua-
rium may be observed cleaning off the layer of green scum,
mostly consisting of algae, which grows on the sides of the
aquarium.

Fig. 87. Variations in a Common Pond Snail.

After Morse, from Packard's Zoology.

There is but one pair of tentacles, at the bases of which
are the e^es. Only a few pond snails have operculums.

134

Descriptive Zoology.

The eggs are laid in clusters, usually enveloped in a gelat-
inous mass ; and in an aquarium are usually deposited on
the side of the glass in a very favorable place for watching
their development. There are three common genera, —
Limnea, a right-hand shell; Planorbis, a discoid shell, or
fiat spiral ; and Physa, a left-hand spiral (Fig. 80).

The River Snails. — These are not entirely distinct from
the pond snails ; still, they nearly all breathe by means
of gills, and most of them have operculums. Being gill
breathers, they of course do not come to the surface to
breathe, hence are not usually so conspicuous. Some of
them have a projecting tube on each side of the neck,
the water entering through one of the tubes to the gill, and
passing out through the other. The eyes are like those of

the pond snails in being
borne at the bases of the one
pair of tentacles. In some
of the river snails the young
are brought forth alive.

Sea Snails. — These are
found chiefly along the
shore, not often in very deep
water. They are numerous
in kinds and individuals, and
vary greatly in both color
and form. In size they vary
from almost microscopic to
a foot and a half or more
in length. They also vary
greatly in shape, from globu-
lar (Fig. 88) to slender tapering forms resembling screws.
The shell is usually right-handed, and the majority have
operculums. Nearly all breathe by means of gills.

Fig. 88. A Large Sea Snail
(Natica).

It feeds on clams, etc., boring through
their shells.

Gastropoda.

135

A Drilling Sea Snail. — Natica (see Fig. 88) is common on the New
England coast. It is one of the largest of the snails found along the
northern shores, sometimes reaching a length of five inches. Natica is
carnivorous, and lives mostly on clams and other bivalves. It burrows
in the mud or sand ; and when it finds a clam, it uses the lingual ribbon
and bores a hole through the shell, rotating its own body meanwhile.

Fig. 89. A Sea Snail (Natica) Graveling.

Showing the very large foot (surrounding the shell).

It produces as neat a countersunk hole as any made by a drill for the
head of a screw such as may be seen in any door hinge. After the hole
is made through the shell, the soft body of the clam is eaten.

Sea Slugs. — Sea slugs are found near shore, on rocks or among
seaweeds. Many of them are devoid of shells when adult, but all have
shells in their earlier stages. Many of them are symmetrical externally,
but few are so in their internal structure, — the intestine, for example,
usually ending on the right side. In some the gills are covered, in others
exposed. The gills often project

Tentacles

Gills

as leaflike appendages on the
posterior part of the dorsal sur-
face ; and the whole animal, in
form and color, has such a close
resemblance to the seaweeds, on
which it crawls and feeds, that it
escapes the enemies to which, in
its defenseless condition, it would
be an easy prey. Some of the
sea slugs can swim, and usually do so inverted, with the flat surface of
the foot at the surface of the water. When the adult has a shell, it
sometimes has its edges covered by the overlapping mantle, and some«
times is completely inclosed by a sac like, mantle.

Fig. 90. Naked Mollusk.

From Kingsley's Comparative Zoology.

136 Descriptive Zoology.

Limpets. — Along the shore there are to be found gastro-
pods with low conical shells, clinging close to the surface
of the rocks. They may be scraped off by a quick motion
with a dull knife, but if they are first alarmed they draw down
and adhere so firmly to the rock that one is likely to break
the shell in the attempt to dislodge them. The keyhole
limpet is so named from the shape of the hole at the apex.

The Ear-shell or Abalone. — Closely related to the limpets
is the " ear-shell " found on the California coast. There is

Fig. 92. Abalone or Ear-shell.

Furnishes mother-of-pearl for inlaid work.

Fig. 91. Limpet.

Surface view and side view. FiG. 93. RED CHITON (kl'tSn).

a row of perforations near one margin of the shell, through
which tentacles project. The interior of the shell is pearly
and of beautifully variegated color. It is known as " aba-
lone," and is much used for inlaid work.

A Multivalved MoUusk. — Chiton is a very peculiar
marine mollusk. It is low and flat, creeping like the lim-
pets. But the shell consists of a series of eight pieces over-
lapping one another from the anterior to the posterior end.
The animal is completely symmetrical, both internally and
externally (Fig. 93).

Gastropoda. 137

CHARACTERISTICS OF THE GASTROPODA.

1. The gastropods have a foot which is developed as a
broad, flat, creeping disk.

2. There is usually a well-developed head, with eyes and
tentacles.

3. The majority have a univalve shell, but this is some-
times lacking.

.4. Body often unsymmetrical.
5. There is a lingual ribbon.

CHAPTER IX.
BRANCH MOLLUSCA.

CLASS CEPHALOPODA.

The cephalopods include such forms as the squid,
cuttlefish, and chambered nautilus.

The Squid. — The squid is the best example of the group.
It is abundant along the Atlantic coast. Squids swim in
schools, and are frequently found following schools of
young herring and mackerel, on which they feed. They

Fig. 94. Common Squid.

From Packard's Zoology.

are chiefly nocturnal, though not infrequently seen in the
daytime. After a storm the writer has seen the beaches
on Cape Ann covered with them in the morning, where
they have been left stranded by the receding tide.

The Form of the Squid. — Seen from above the body ap-
pears cylindrical. At the anterior end is a well-developed

138

Cephalopoda. 139

head and a distinct neck. At the tail end are two triangu-
lar fins which together present the appearance of a dia-*
mond-shaped arrow point. Seen from below the body is
conical or fusiform, ending in a distinct point behind, the
tail fin covering about one third of the body. The fins are
attached at the sides of the dorsal part of the hinder part
of the body, and can be wrapped more or less around the
tapering posterior end. The common kinds of squids sel-
dom attain a length of a foot.

The Head. — From the front of the head project five
pairs of arms, arranged in a circle around the mouth.
Four pairs of these arms are short, and taper to a point.
One pair are much longer, being nearly as long as the body,
and are enlarged near the ends. On the inner surfaces of
the short arms, and on one side of the club-shaped end of
the long arms, are rows of suckers. These are button-
shaped or saucer-shaped bodies, attached to the arms by
stalks. The outer surface is hollow, and when applied to
any surface the center can be retracted by the muscular
stem by which it is attached, thus making a strong hold-
fast. The long arms are sometimes called the '* grasping
arms."

On the sides of the head are the two large eyes, the
most highly developed eyes among the invertebrates.

The Mantle. — There is an opening all around the neck
where it projects from the mantle cavity. The whole
external envelope of the body is the mantle, inside which
is the conical body, with a space extending nearly all around
it except along the dorsal line, where the outside of the
body mass is attached to the inside of the mantle. The
mantle is muscular and very powerful.

The Pen. — The squid has no external shell, and the
only representative of one is a horny structure, somewhat

140 Descriptive Zoology.

similar in shape to a feather. This is imbedded in the dor«
sal part of the mantle, extending nearly the whole length of
the back. It is wholly inclosed in a capsule in the thick-
ness of the mantle wall.

The Siphon or Funnel. — Projecting from the mantle
cavity under the head is a funnel whose narrow end opens
forward and whose wide end points back into the mantle
cavity.

How the Squid Swims. — Water is taken into the mantle
cavity through the open space around the neck. Then
the edge of the mantle is contracted and is fastened to the
neck and sides of the base of the funnel by a set of car-
tilages that have a sort of '* hook and eye " arrangement.
Then by the contraction of the mantle the water is forced
out through the siphon, and by reaction the squid is rapidly
driven backward through the water. So swift is its move-
ment that it has received the popular name of " arrow fish."
Squids sometimes dart clear out of the water, and, when
kept in aquariums, thus jump over the sides. Their mo-
tion is amazing, not only on account of its swiftness, but
because there is no manifest cause of the motion. They
propel themselves by the outgush of water, which is in-
visible, and the change in size from the contraction of the
mantle is so slight as to be unnoticed. To the uninstructed
it is as inexplicable as the motion of a trolley car is to
a savage. When the squid wishes to move slightly, it
does so by gently flapping the tail fins.

The Ink Bag. — The squid has an ink bag, which lies
near the rectum, and which opens near the anal opening,
near the inner end of the funnel. When in flight from a
pursuing fish, a discharge of ink is sent out in the strong
gush of water through the siphon. This makes a dark
cloud in the water, under cover of which the chances of

Cephalopoda. 141

escape are greatly increased. This ink is the original
"sepia" used as ink by the Chinese and Japanese. Some
of this ink, from the fossil squid, has been used to make a
drawing of the animal from which the ink was taken.

The Color of the Squid. — Ordinarily the dead squid is
of a pale color, tinted with purplish. In the living animal
the color is very changeable, passing quickly from red to
b!ue or purple, and one part may have one of these colors
while other parts have another color. This change of color
is due to several different sets of colored cells, called "chro-
matophores"; these expand and relax under the control
of muscles, which are in turn governed by nerves. The
color changes in quick flashes, exceeding the quickness of
blushing and pallor observed in the human face. This
change of color is undoubtedly for the sake of protection,
though one is inclined to wonder why such intense hues
should be employed. As a school of squids are swimming
along they are often seen to change their color abruptly,
according to the bottom over which they are passing.

Methods of Escape from Enemies. — (i) The squid may
elude observation by taking on the color of its surround-
ings. (2) By speedy flight. (3) In flight its chances of
escape are increased by the discharge of ink, which makes
the water turbid.

The Digestive System. — The brown beak projects from
the center of the circle of arms in front of the head. It
consists of a pair of hard, horny jaws, somewhat resem-
bling the beak of a parrot, except that the upper jaw
is much smaller than the lower, into which it shuts.
In addition to the beak there is a lingual ribbon, as in the
snails. From the mouth extends a long, narrow gullet.
Well back in the body is the muscular stomach, which
has a large cecum. The intestine then extends forward,

14^ . Descriptive Zoology.

ending in the mantle cavity near the large inner end of
the funnel. The excrement, as in the clam, is swept out
by the water current. There are salivary glands ; and a
large digestive gland, often called the " liver," pours its
secretion into the cecum.

How the Squid captures its Prey. — The squid is a
voracious animal and lives largely on small fishes. It
sometimes stealthily approaches a fish by almost imper-
ceptible motions of its fins, until it is within grasping dis-
tance, when it suddenly seizes the fish and quickly kills it
by biting it in the back of the neck. Again it swims
swiftly, and suddenly darts among a school of fishes, and
turns and kills its prey by a quick snap of its powerful
jaws. It also eats crabs and other animals. While it is
pursuing the smaller fishes, it may, in turn, be chased by
larger fishes.

Respiration and Circulation in the Squid. — The squid
has two plumelike gills attached to the under surface of
tne body, extending along the mantle cavity. The circu-
latory system is more highly developed than in any of
the other mollusks.

The Nervous System. — The nervous system, too, is
highly developed and concentrated, consisting of several
pairs of ganglions in the head, forming a central brain,
from which nerves extend to the other parts of the body.
There is a protecting case of cartilage, a rudimentary cra-
nium, supporting and partly surrounding the brain.

The Senses of the Squid. — The eyes are highly devel-
oped, and evidently have keen sense of sight. A number
of squids may be lying side by side in the water, perfectly
motionless, perhaps relying on their quietness and protec-
tive color. A sudden motion on the part of a person ob-

Cephalopoda.

143

serving them may cause them to dart off like so many arrows.
There is a rudimentary ear. Some authors say that the squid
has the five senses which are best known in our bodies.

The Squid used as Bait. — Squids are used very extensively as bait
in the cod fishery, a single small vessel sometimes using eighty thou-
sand in six weeks. They are caught mainly by means of nets. They
are either kept fi-esh for this use, or may be "pickled" in brine.
They are also used in fishing for bluefish.

Fig. 95, Octopus, from Brazil.

From Packard's Zoology.

Giant Squids. — Some species of squids have a body over nine feet
long, with arms thirty feet in length. Some of these may have given
rise to the stories of " sea serpents."

The Octopus. — As the name indicates, these forms have eight arms
instead of ten, as in the squids and cuttles. The body is short and
nearly spherical. Though the octopus can swim, it is very much less
active than the preceding forms, spending most of the time crawling
over the bottom, resting on the basis of the circle of arms with the body
held above. The arms are more or less connected by webs at the base.
There is neither internal nor external shell. A Pacific coast octopus has
body a foot long, the arms having a radial spread of twenty-eight feet.

144 Descriptive Zoology.

Many weird tales are told of the octopus, most of which have little or no
foundation. In fact, there is no satisfactory evidence that an octopus
ever intentionally attacked a human being. In countries adjacent to
the Mediterranean the octopus is largely used as food.

The Nautilus.— The nautilus is closely related to the squids and
cuttlefishes, but has the body inclosed in a flat-spiral shell. From
time to time the animal moves forward and partitions off the space in
the shell which it formerly occupied, the live animal occupying only the

Fig. 96. Chambered Nautilus.

Showing chambers with soft body in outer chamber.

From Packard's Zoology.

outermost space in the shell. It retains its hold on the smallest and
oldest portion of the shell, however, by means of a slender fleshy cord
which passes through a series of holes left in the partitions. The inner,
abandoned spaces are filled with gas. From this fact of growth the
animal is commonly called the chambered nautilus, though it is also
called the pearly nautilus, from the pearly lining. It lives in the
South Seas.

Fossil Chambered Shells. — While the nautilus is almost the only
living form of this peculiar plan of growth, there are many fossil cham-
bered shells. Two of the most noteworthy of these are the Ammon-

Cephalopoda. 145

ites, a spiral form very similar to the nautilus, and a perfectly straight
conical shell, hence named Orthoceras.

The Cuttlefish. — In the cuttlefish the lateral fins extend along
Jhe whole of the length of the side, and the body is less sharpxy
conical. Though essentially like the squid, they are less swift in the'r
flight. In the sharp prow of the squid one sees the build of a racing
shell, while the greater width of the cuttlefish suggests the increased
breadth of beam in an ordinary rowboat. Cuttlefishes feed on crabs,
clams, and fishes. The internal shell of the cuttlefish is calcareous,
instead of horny as in the squid, and is well known from its use in fur-
nishing limy material to canary birds. The ink of the cuttlefish is the
basis of the pigment sepia. Cuttlefishes live near shore and are used
extensively as food (in the Old World) as well as for the ink and
cuttle bone.

CHARACTERISTICS OF THE CEPHALOPODA.

1. There is a distinct head with highly developed eyes.

2. The foot has developed around the head (hence the
name Cephalopoda), and is divided into a number of arms.

3. Part of the foot develops into a funnel-like siphon.

4. The shell may be external, internal, or lacking.

5. Chromatophores are found in the skin.

6. There is a beak and a lingual ribbon.

CHARACTERISTICS OF THE MOLLUSKS.

There is such a great diversity among the mollusks that
it is very difficult to make any concise statement of their
common characteristics. Some have shells, others none ;
some are aquatic, others terrestrial ; some live in fresh
water, others in the sea ; some breathe by gills, others by
lungs ; some are herbivorous, some carnivorous ; some are
free, others sessile; the Hmpet, though free, practically is
glued to its place on a rock ; the slug is so slow that we
have borrowed his name to make a common adjective,

146 Descriptive Zoology.

while the scallop swims actively ; clams and oysters feed
on microscopic forms swept in by currents of water, while
the cephalopods prey upon the most active fishes ; there is
Strong contrast between the monotonous existence of the
headless clam, burrowing in the mud, and the free life of
the cuttlefish, with its distinct head and highly developed
eyes ; the oyster is fixed to his spot,- almost as passive as a
sponge, while the squid darts so swiftly that it is called
the arrow fish.

Nevertheless the following characteristics belong in
common to the various classes of mollusks : —

1. Aside from the shell the body is soft; hence the
name " mollusk," soft.

2. The body is unsegmented, in distinction from the
arthropods, the vertebrates, and many worms.

3. There is an extension of the skin called the " mantle,"
which usually produces a shell, univalve, bivalve, or rarely
multivalve.

4. There is usually a ventral muscular extension, the
foot, which, in most forms, serves in locomotion.

5. They are mostly bilaterally symmetrical, but some
are much distorted.

6. The nervous system consists of about three pairs of
ganglions, connected by nerve cords.

CLASSIFICATION OF THE MOLLUSCA.

As all earlier classifications are based on superficial
characteristics, it was to be expected that the first classifi-
cations of mollusks would be by their shells. Hence the
science of Conchology. But now we class the mollusks,
as other groups, by their general plan of structure,
mainly of the soft parts, for these parts make the shell,
and the shell does not mould them.

Cephalopoda. 147

They have been classed according to the head into
Acephala (headless, clams), Cephalophora (head-bearing,
snails), and Cephalopoda (head-footed, squids).

The classification here adopted is based on the foot and
presents three chief classes : —

1. Pelecypoda (hatchet-footed) ; example, the clam.

2. Gastropoda (stomach-footed) ; example, the snail.

3. Cephalopoda (head-footed) ; example, the squid.

CHAPTER X.
BRANCH CHORDATA.

This branch is mainly composed of the vertebrates, or
backboned animals, that is, fishes, amphibians, reptiles, birds,
and mammals. But it is now found necessary to class with
them certain other animals formerly regarded as inverte-
brates. Hence the old branch Vertebrata is made a sub-
branch, and, with two other subbranches, included in the
branch Chordata. The chordate animals are characterized
by the possession of a dorsal chord or notochord. This is
a supporting rod extending along the dorsal region between
the body cavity and the main nervous system or spinal
cord. While the notochord is always present in the young,
it is, with a few exceptions, replaced in the adult by a seg-
mented cartilaginous or bony axis, which is known as the
spinal or vertebral column. In other words, the notochord
is a sort of forerunner of the backbone.

Subdivisions of Chordata. — The branch Chordata is
divided into three subbranches : —

1 . Adelochorda, wormlike, marine forms (Balanoglossus).

2. Urochorda, the tunicates or ascidians.

3. Vertebrata, lancelet to mammals.

Division A. — Acrania, the lancelets.

(a) Cyclostomata, without
jaws (lampreys).

(^) Gnathostomata, with
jaws (true fishes to
mammals).

Division B. • - Craniata.

148

Chordata. 149

SUBBRANCH UROCHORDA.

As an example of the urochordates we may take the
common ascidian. Such forms are sometimes called *'sea
peaches" or *'sea pears," indicating the size, shape, and
general appearance. They are attached by one end to
rocks or shells or even to a muddy bottom. There are two
holes, one at, and the other near, the free end. When the
living animal is disturbed, it ejects water from both of
these holes, hence the more common name, ''sea squirt.''
The tough muscular external coat, or tunic, also gives the
name tunicata. They are all marine.

Structure of an Ascidian. — Inside the outer wall, or tunic,
is a lining, the pharynx, which hangs free below its attach-
ment near the larger opening, the mouth. The pharynx
is perforated by many small apertures through which water
is driven by ciUa. From the space around the pharynx,
the peribranchial chamber, the water passes out through the
second, or exhalant, aperture. From the lower end of
the pharynx arises the gullet, which soon enlarges into the
stomach. A relatively short intestine empties into the
peribranchial chamber, where the outgoing water current
catches the refuse of digestion. There is a simple tubular
heart, which is unique in its action. After pumping the
blood in one direction for a few beats, it reverses its action
and sends the blood the other way. The nervous system
is very simple, consisting mainly of a ganglion between
the two apertures (see Fig. 97).

Development of Ascidians. — In the above account of the
structure of an ascidian there is no trace of relationship to
the other chordates, and so long as the structure of the
adult only was known, no one even guessed at its real
affinities. But the study of its development threw light on

so

Descriptive Zoology,

the subject. It was found that the larval ascidian possesses
a long tail in which is a distinct notochord and an elongated
nerve cord. But early in life the larva attaches itself by
its head, the tail gradually disappears, and the elongated
nerve cord becomes shortened to a mere ganglion. In the

Mouth

Water exit

Heart

Fig. 97. Diagram of a Tunicate or Ascidian (Sea Squirt).

From Kingsley's Zoology.

sessile adult animal no trace remains of the primitive noto-
chord. This illustrates what is called *• retrograde devel-
opment " ; or, in simple words, the ascidian is a degenerate
chordate, perhaps even a degenerate vertebrate. This is
one instance of degeneration in which the real relationship
is indicated by the structure of the young rather than by
that of the adult.

A crania. 151

Other Tunicates. — Some tunicates are minute and free-
swimming by means of a vibratile tail. Other small forms
are barrel-shaped, and exhibit a marked "alternation of
generations." Many of the tunicates live and multiply by
budding in colonies.

SUBBRANCH VERTEBRATA.

The Lowest Vertebrate. — To the beginner it would seem
easy to determine whether or not an animal has a back-
bone, and so to decide whether it is a vertebrate or an
invertebrate. But let us take a glance at what is by many
authors regarded as the simplest of the vertebrates.

The Lancelet. — The lancelet (Branchiostoma, or Amphi-
oxus) is fishlike in form and general appearance, only two

Fig. 98. Diagram of Lancelet.

Above (dotted) is the nervous system; below it (cross-lined) the notochord; the mouth is sur-
rounded by a circle of tentacles; below the notochord is a row of gill slits; the vent is
near the posterior (right) end below. From Kingsley's Zoology.

or three inches long, and nearly transparent. It is marine,
being found in warm waters. Specimens are taken along
the south Atlantic coast. The lancelet has a notochord
extending to the anterior end, or the snout. There is a
nerve cord along the dorsal side of the notochord, but the
anterior end is hardly well enough developed to deserve
being called a brain. It has blood tubes, but no heart.
There is a tail fin, but no limbs, not even paired fins. The
mouth is surrounded by a circle of fringelike tentacles.
Back of the mouth extends the capacious pharynx, whose
walls are perforated by numerous ciliated gill slits. At the

152 Descriptive Zoology.

posterior end of the pharynx the intestine continues to the
anus, situated posteriorly and ventrally. By the action of
the cilia water is taken into the mouth, passes through the
slits in the wall of the pharynx, and enters a space around
the pharynx, called the atrial or peribranchial chamber,
whence it escapes to the exterior through a ventral opening
called the atrial pore. The lancelet usually lies buried
in the sand, with only the mouth projecting. It gets both
food and oxygen from the water, which is circulated
through the body by means of ciliary action. The lancelet
occasionally swims by fishlike movements.

Classification of the Lancelet. — It might, at first thought,
seem strange that so simple an animal should be classed
with a group having such complex structure as the verte-
brates. The lancelet has, in fact, been placed with the
moUusks, and later with the fishes, but is now located at
the foot of the vertebrate series, chiefly on account of the
possession of the notochord and the dorsal nervous system.
It is really hard to locate an animal with colorless blood,
and with neither skull, brain, heart, auditory organs, paired
eyes, nor paired fins.

The student who gets his ideas of classification almost
entirely from reading is apt to think that the animal king-
dom is divided into groups separated by clear and distinct
dividing lines. But when he undertakes the actual exami-
nation of any considerable series of animals, he often finds
that two groups, which he regarded as distinct, actually
merge one into the other so gradually that he finds it diffi-
cult to see just where the line of division should be drawn.
The line of demarcation must frequently be so drawn that
it cuts across some intermediate forms, part of whose char-
acteristics lie on one side and part on the other. In some
cases the intermediate forms are living; in other cases the

Cyclostomata. 153

" connecting links " are represented only by fossil forms,
as, for example, the extinct animals that connect the
reptiles and the birds.

The lancelets are plainly on the threshold of the verte-
brate household. By some authorities they are denied
admittance, and must wait just outside. Others allow
them barely to cross the threshold and humbly take their
place by the door, the lowest of the great branch at whose
head stands man.

Distinction of the Lancelet from Other Vertebrates. — On
account of the poorly developed brain and the absence of
a cranium, the lancelet is placed by itself in a division
called Acrania, while all the other vertebrates are desig-
nated as Craniata, from the presence of a skull and the
higher development of the brain.

CLASS CYCLOSTOMATA.

The lowest of the craniate vertebrates are the Cyclo-
stomata. This class includes the lampreys, or lamprey
eels, as they are often called, and the hagfishes. They
are eel-Hke in form, without scales, and with smooth, slimy
skins. They have no jaws, but a round, sucking mouth,
hence they are sometimes called the " round-mouthed eels."
There is a single nostril on top of the head. They have
dorsal and caudal fins, but no paired fins. There are sev-
eral pairs of purse-shaped gills, hence they are called by
some authors Marsipobranchii. The skeleton has no trace
of bone, being wholly cartilaginous and very imperfectly
developed. The internal organs are, in many features,
similar to those of the true fishes.

Lampreys are rather widely distributed. They are
found along the Atlantic coast and ascend the rivers.

154

Descriptive Zoology,

Some appear to live permanently in our large lakes. By
their sucking mouths they attach themselves to fishes,

Fig. 99. Lamprey Eel.

After Goode. — From Kingsley's Zoology.

sucking their blood, or even penetrating their bodies.
They are the only vertebrates known to live a parasitic
life. In Europe the sea lampreys are valued as food.

CLASS PISCES.
Example. — The Ringed Perch.

Life of a Perch. — If one stops to consider what are the
chief objects in life with a fish, he soon sees that it is well
expressed in the words " to eat and not be eaten.'*

DORSAL FINS

INTER-OPERCLE

Fig. 100. External Features of a Perch.

In order to secure food and escape enemies the fish
must have sense organs and organs of locomotion.

Pisces. 155

How the Fish Floats. — Before taking up the question of
locomotion in fishes, let us first consider how it is that the
fish can keep its place in the water without effort, neither
rising nor sinking. A freshly killed fish usually sinks,
showing that its body is slightly heavier than water.
Almost every one knows that after a fish has been dead
a short time it usually floats (commonly with the ventral
surface upward). This is due to the development of gases
in the intestines.

Most fishes have air bladders (or swim bladders), by
means of which they can regulate their position in water.
By shortening the muscle fibers in the walls of the air
bladder, or in the walls of the abdomen, the air bladder is
made smaller and the fish sinks. By relaxing the muscles
the air expands, the fish as a whole is relatively lighter,
and consequently rises.

Most fishes have swim bladders, and stay in midwater,
that is, do not rest most of the time on the bottom. On
the other hand, many fishes that rest most of the time on
the bottom are without a swim bladder. In some fishes, as
the perch, the air bladder is attached to the walls of the
abdomen. In others, for example, suckers, the air bladder
is free from the walls of the abdomen and is readily
removed, and in dressing the fish the air bladder is taken
out with the other internal organs.

Locomotion of Fishes. -:— Most fishes have the body com-
pressed ; that is, flattened from side to side. The thickest
part of the body is in front of the middle. The longer
taper is toward the tail, and this gives greater flexibility
and freedom of motion to this part. When the fish wishes
to swim, it makes a sideways and backward stroke of the
tail. This sends the body ahead and sideways ; that is, if
the tail is struck back and to the right it pushes the fish

156 Descriptive Zoology.

forward and to the left. But the fish quickly makes an-
other stroke in the opposite direction, and as a result of
the two he may go straight ahead. The fish may simply
make the double stroke, right and left, and without further
strokes dart straight forward, but usually there is a suc-
cession of strokes by which it is enabled to pursue a
straight course. It should be noted that nearly all fishes
that can swim rapidly have a pointed snout to diminish the
resistance. Resistance to the motion of the fish is still
further reduced by the mode of overlapping the scales and
the coating of mucus. The fins, too^ point backward.

How the Perch Eats. — The perch feeds on minnows,
worms, water insects, and larvae of various sorts, which it
catches and swallows alive. The extensibility of the mouth
is very great. The upper jaw can be protruded so that
the opening of the mouth is a wide circle, nearly as large
as the greatest circumference of the fish at any point. It
has been noticed that when the fish keeps the mouth closed
the snout presents a sharp point; this is in marked con-
trast with the large opening shown when the fish is about
to ingulf its prey. It must be kept in mind that the fish
has no special organs of prehension, but must do all the
work of catching with the mouth alone. There are
numerous teeth, but they are not large, serving merely to
hold the struggling captive, and used little, if any, for either
tearing or masticating it.

Digestive Organs of the Perch. — The mouth narrows back
into the wide gullet, which is kept closed except when
swallowing. The gullet leads into a fair-sized stomach,
which ends blindly behind. The intestine arises from one
side of the anterior end of the stomach. At the begin-
ning of the intestine are three short blind tubes, the ceca.
The intestine takes one or two turns and terminates in

Pisces.

157

the anal opening. As
the perch is carnivorous,
we should naturally ex-
pect a relatively short in-
testine. In the anterior
part of the body cavity
lies the liver. On its
posterior surface is the
bile sac, which may be
greenish or yellowish,
or, if empty, have little
color. It is then hard to
discover, and appears
like a small worm-shaped
appendage to the liver.
A duct conveys the bile
into the intestine.

Circulatory System of
the Perch. — The heart
of the perch is almost
literally "in his throat.'*
The heart is in a sepa-
rate cavity, the pericar-
dial chamber, with a
firm partition between it
and the main body cav-
ity. The heart_consists
of three parts, through
which the blood passes
in order from behind.
The venous sinus re-
ceives the blood from all
parts of the body ; from

158 Descriptive Zoology.

the sinus the blood enters the auricle, which also is thin-
walled ; from the auricle it passes into the ventricle, whose
walls are thick and muscular, and by whose contraction the
blood is pumped clear around the whole circuit to the heart
again. From the anterior end of the ventricle runs for-
ward the artery leading to the gills. The first part of the
artery is often enlarged and is sometimes called the arterial
cone or arterial bulb. This artery divides into four branches
on each side, one to each gill. After traversing the gills,
the blood-tubes (still called arteries) unite on each side, and
later the two arteries thus formed unite to form one dorsal
artery which supplies all parts of the body. The small
arteries subdivide and form capillaries, which pervade all
the tissues. The capillaries unite to form the veins, which
again bring blood to the heart.

How the Perch Breathes. — When watching a live fish
one sees that the mouth and gill openings open and close
alternately. It can easily be proved that water enters the
mouth and passes out through the gill openings ; thus a
pretty constant current of water flows over the gills. Each
gill consists of a bony arch, hinged at the upper and lower
ends and jointed in the middle. Along the posterior border
of each gill is a red fringe, the red color being due to the
red blood within, which shows through the thin, delicate
coverings of the gill filaments, as the individual parts of
the fringe are called. As the blood comes up into the
gill from the artery below, it goes off into small side
branches running out into the filaments ; when it returns
along the other margin of the gill filament, it enters
another artery to pass out at the upper end of the gill.
Thus it is clear that there is a constant flow of blood in
very narrow, thin-walled tubes in the thin-covered gill
filaments; there is also a stream of fresh water flowing

Pisces.

159

over the outside of the
filament. The blood
entering the gills has
lost oxygen in passing
through the muscles
and other working tis-
sues of the body ; so, in
passing through the
gills, it absorbs oxygen
from the water through
the comparatively thin
wall that separates it
from the water. On the
other hand, the blood
entering the gills is
loaded with carbon di-
oxid and other waste
matter that it has
picked up in the mus-
cles and other tissues ;
this passes out into the
water and is carried
away. It should be
noted that the current
of water is in the right
direction to keep the
delicate gill fringe
evenly extended, in-
stead of matting and
tangling it together, as
it would be likely to do
if the water current
were reversed.

l6o Descriptive Zoology.

The Protection of the Gills. — The gills are really ex-
ternal organs. From the nature of their work they must
have very thin external coatings, and so are correspond-
ingly delicate. Hence the strong yet flexible gill cover.
The more technical name for this is the opercle. It con-
sists of several parts, the opercle proper, subopercle,
pr^opercle, and interopercle (see Fig. lOo). Overlapping
from front to back, and being under muscular control so
that they can be held down with considerable force when
necessary, they constitute a very good_shield. In addition
to the opercle there is a gill cover below, called the bran-
chiostegal membrane. It is a tough, yet thin, mem-
brane supported by several small curved bones, the
branchiostegal rays. A fish carries about its head organs
that are of vital importance and of most delicate texture,
yet it dashes among more or less rough aquatic plants and
after fishes that are well armed with spines. It is safe in
doing this because of the double set of gill covers, one soft
and one bony.

When the perch swallows a spiny fish, still struggling,
will not the soft gills be torn from the inside, producing
serious injury ? The use of the bony, toothlike gill rakers
projecting on the inner surface of the gill arches is now
apparent. The gill rakers also serve as a strainer in
swallowing smaller particles of food, and some authorities
say that the gill rakers serve, to a certain extent, as teeth in
crushing the food.

When the fish seizes its prey, it of course takes water
into the mouth with it; but this is allowed to pass out
through the gill openings, and probably only a little is swal-
lowed with the food.

The Sense Organs of the Perch. — The perch has well-
developed eyes, but without movable lids. If any one

Pisces. i6i

doubts their keenness of sight, let him fish for trout or black
bass before rendering his verdict. The sense of touch
seemsjwell developed. Numerous fishes have tactile bar-
bels about the mouth, as the catfish, sturgeon, and codfish.
The lateral line is considered a sense organ. There is an
internal ear, but it does not appear that fishes hear ordinary
sounds made out of water, like human speech, unless they
are loud ; on the other hand, fishes have a keen perception
of any sound vibrations that are directly transmitted to the
water, such as splashing in the water, noises made by the
grating of oars in the oarlocks or by hard objects striking
the bottom or sides of a boat. The semicircular canals are
now understood to be connected with a sense of equilibrium.
Smell is probably pretty well developed, in some fishes at
least. The nostrils have nothing to do with respiration in
any fishes below the lungfishes. The nostrils do not open
into the mouth, but are simply openings into a cavity
around which the nerves of smell are distributed. Some
fishes have a single nostril on each side. In others, as in
the perch, there are two openings on each side. The two
nostrils of one side connect with a common cavity, the
water entering through one aperture and leaving through
the other. The sense of taste is probably less distinct.

Excretory Organs of the Perch. — The gills excrete car-
bon dioxid. For the removal of nitrogenous waste matter,
there is a pair of slender red kidneys which extend the
whole length of the body cavity. They can be seen
through the dorsal wall of the air bladder. There is an
enlargement at the anterior end in front of the air bladder.
At the posterior end there is a tube, the ureter, to convey
the excretion to the exterior; this duct joins a small uri-
nary bladder and opens just back of the opening of the ovi-
duct, so that the three openings at this place are, in order

1 62 Descriptive Zoology.

from the front,' the anus, the opening of the oviduct, and
the -opening of the ureter. In most of the higher fishes
these three openings are separate.

Development of the Perch. — The ovary is an elongated
body, occupying, when the eggs are mature, a large part of
the space in the body cavity. The outlet of the ovary is
the oviduct, whose external opening is just back of the
anus. The ovary shows that it is really a double organ by
its forked anterior end. In the male the two white sper-
maries unite in one sperm duct, which reaches the exterior
just behind the anal opening. The eggs are fertilized
after they have been laid. They are left without care on
the part of the parents. The eggs contain a store of nour-
ishment which is not yet completely absorbed when the
tiny fish begins to swim. The young fishes feed at first on
small crustaceans and other minute forms of Hfe. Both
the eggs and the young fishes are eaten in great numbers
by many kinds of fishes and other voracious water animals.

Scales. — Scales are developments of the deeper skin or
dermis, serving for protection, or ornament, or both. The
scales usually overlap each other so much that only a small
part of each scale is exposed, and this part is covered by
the epidermis. The scales are usually of horny material
and not bony, except in a few fishes, such as ganoids.

Kinds of Fish Tails. — When the tail is completely sym-
metrical, inside and outside, it is called diphycercal. In
most fishes the tail, while externally symmetrical, is not so
within, the spinal column being turned up as it joins the
tail fin ; such a tail is homocercal. When the tail is unsym-
metrical, with the spinal column extending into the upper
lobe, the tail is said to be heterocercal. It is noteworthy
that the tails of nearly all young fishes are heterocercal.

Pisces. 1 6^

The Fins. — The ordinary fin has a set of fanUke rays
supported by a series of bones at the base of the fin.
Fins are designated as " soft-rayed " or " spiny-rayed,"
according to the nature of the supporting rays.

The dorsal, anal, and caudal fins are called median, as
they are in the middle plane of the body. The pectoral
and pelvic are spoken of as " paired fins," and are com-
parable to the two pairs of Hmbs of the higher vertebrates.

Uses of the Different Fins. — As already noted, the tail
fin is the chief propelling power. It also serves as a rud-
der in guiding the direction of movement. The paired fins
serve as balancing organs and also serve in elevating or
depressing the body. The dorsal and anal fins act like
the keel of a boat in steadying and guiding the movement.

The Air Bladder. — The air bladder is generally consid-
ered as comparable with the lung of the higher forms. It
certainly acts as an organ of respiration in the lungfishes
and some of the ganoids.

But in most fishes the air bladder acts as an organ for
maintaining the fish's position in the water, and hence is
more appropriately spoken of as a " swim bladder." In
the lungfishes and some ganoids the air bladder has a wide
and direct connection with the gullet ; in many other fishes
the opening persists, but is less direct. On the other
hand, in many fishes the duct is entirely closed. The air
bladder may have thin walls or thick ; it may be in one
section or divided into several sections ; it may be attached
to the body wall or lie freely in the body cavity.

Flatfishes. — Fishes may be flattened in two ways :
( I ) from side to side, that is, laterally, when they are said
to' be "compressed," as in the ordinary fish, more mark-
edly shown in the fresh-water sunfishes; (2) a fish that
is flattened from above, or dorso-ventrally, is said to be

164 Descriptive Zoology.

"depressed," as with the rays. The flounders are com-
pressed, but have turned down on one side.

Electric Fishes. — These fishes have the power of giving
an electric shock when touched. The electrical apparatus
is a modification of the muscular system, and, Hke the
muscles, is under the control of the nervous system. It is
a point to be noted that the electric fishes are devoid of
scales. The torpedo of the Atlantic coast and of the
Mediterranean belongs to the rays. An African catfish
has the same power, and in South America is found the
electric eel. It is said that in South Africa the natives
drive herds of horses into the pools, and after the electric
eels have exhausted their " shocking power " on the horses,
the eels may be caught and handled with impunity.

Colors of Fishes. — The colors of fishes are due to two
factors, the nature of the scales and the pigment in the
epidermis. The scales often are striated or poHshed to
give various colors, especially the gleam so often seen on
the sides of a fish. Aside from this kind of appearance the
color is chiefly due to pigment. As in most animals, the
color is darker on the back than below, where we often find
white. The oHve or dark back of most fishes makes it
difficult to see them when looking down into the water,
while the white color beneath might make a fish less con-
spicuous to an enemy below him. In the breeding season
many fishes, especially the males, assume much brighter
colors, most accented on the fins. Many fishes, notably
catfishes, change their color considerably in conformity
with their surroundings, like the amphibians and lizards.

Care of the Eggs and Young. — Most fishes give no care
whatever to the eggs or young. Some deposit the eggs in
a place of comparative safety. The stickleback builds a
nest for the eggs and the male defends them carefully.

Pisces. 165

But the eggs of many fishes are eaten by thousands by many
kinds of fishes and other animals. The very great num-
ber of eggs laid by most fishes is in keeping with the fact
that the chances are many to one against their success-
ful development. Indeed, if the eggs all developed,
it is easy to see that the ocean would be overrun. For
instance, the codfish is said to lay about eight miUion
eggs yearly ; if each of these eggs developed, it would not
take long literally to fill the ocean. Contrast this ** infant
mortality" with that of the fulmar petrel. This is said
to be the most numerous bird in the world, though it lays
but a single egg; but the conditions are such that the
chances of this single egg for reaching maturity are ex-
tremely favorable.

Migration of Fishes. — The salmon, shad, and sturgeon
pass from the sea up rivers to spawn. The eels pass from
rivers into the sea to lay their eggs. Aside from migrat-
ing to find suitable breeding grounds, fishes migrate more
or less in search of food. With some kinds their move-
ments are pretty regular and well known ; in other cases
their location at any given season is very uncertain, depend-
ing on their food and other conditions not accounted for.

Deep-sea Fishes. — Most fishes are found near shore or
in comparatively shallow water. Of those found in deeper
waters, it is interesting to observe that, as the water be-
comes deeper, and the amount of Hght consequently less,
the fishes usually have larger eyes, or else a better develop-
ment of the organs of touch. In the deepest water many
are phosphorescent, and blind fishes, or fishes with rudi-
mentary eyes, are found.

The Food Fishes. — Among the principal food fishes are
the codfish, salmon, haddock, shad, mackerel, hake, smelt,
sardine, menhaden, mullet, lake trout, whitefish, sturgeon,

1 66 Descriptive Zoology.

halibut, flounder, herring, catfish, various kinds of bass, both
fresh-water and marine, pike, pickerel, sucker, buffalo, carp,
and many others. Space will not permit an account of
them here, but the student is referred to the Riverside
Natural History^ and other works of the same scope.

Artificial Propagation and Distribution of Fishes. — In
late years much has been done toward protecting and
propagating our edible fishes. With the increase of popu-
lation the food question will gradually become a more and
more serious one. An excellent authority has said that an
acre of water ought to supply as much food as an acre of
land. The time has passed when the privilege is extended to
any one to fish anywhere and at any time. Common sense
dictates that fishes should not be caught during their breed-
ing season, and that they should not be caught under a cer-
tain size, etc. ; hence laws limiting the fishing season, and
requiring that seines must have meshes not less than a given
size. Killing fishes by the use of dynamite is prohibited.
Also it is provided that there shall be no obstruction to the
free passage of fishes up and down streams; and that
where dams are necessary, side channels (fish ways) shall
be provided.

Most of the states have enacted laws for the protection
of its native fishes. A number of states have made appro-
priations for the establishment and maintenance of fish
hatcheries, where fish are artificially hatched. These are
shipped, to be introduced into various waters where it is
thought they will thrive, sometimes to replenish a stock
that is diminished by overfishing or other causes ; in other
cases to introduce them where they do not naturally occur.
The United States government has also taken the matter
in hand, and many valuable results have been obtained.
This industry is comparatively in its infancy, but it promises

Pisces. 167

to increase greatly the world's food supply. It remains to be
seen what can be done toward getting rid of the more
voracious fishes that destroy so many of the young of the
food fishes. The pikes, including the pickerel and mas-
calonge of the tributaries of the Mississippi and St. Law-
rence, must greatly reduce the numbers of more valuable
fishes. If they were to increase rapidly, they might nearly
deplete the waters, so active and voracious are they.

CHAPTER XI.
BRANCH CHORDATA.

CLASS PISCES {Continued).
The Elasmobranchs.

The sharks and rays are the chief representatives of the
subclass designated Elasmobranchii. They are nearly all
marine. One of the best representatives is the shark
known as the ** dogfish," which is caught in large numbers
along the New England coast for the sake of the oil ob-
tained from the livers. It differs from the "true fishes"
in the following points : —

1. The skeleton is cartilaginous, never bony.

2. There is no gill cover, the gill slits (usually five)
opening separately.

3. The mouth and nostrils open ventrally.

4. The scales are small and separate, making the skin
rough.

5. The tail is heterocercal, — that is, the spinal column
extends up into the upper lobe.

6. The eggs are few and large, inclosed in a tough case,
the walls being strengthened by chitin. In some sharks,
as the dogfish, the young are brought forth alive.

7. There is no air bladder.

The Sharks. — The typical shark has a spindle-shaped
body, and is exceedingly active. The mouth is far back
under the head instead of in front, as in most bony fishes

168

Pisces.

169

The gill openings are separate. The teeth are flat, three-
cornered, and sharp. There is a constant succession of
teeth, so that as those of the front row are lost, others take
their place from behind. Though sharks are very vora-
cious, it does not follow that they always attack human

Fig. 103. Shark (Dogfish).

Showing separate gill slits. Tail heterocercal.

beings. For instance, on the coast of North Carolina sharks
are abundant and of large size ; yet they do not attack man.
This is probably because fishes are abundant and the
sharks have an ample supply of food. But in some parts
of the world sharks are exceedingly dangerous.

The Rays. — The skates and rays have a broad body,
partly due to the merging of the body into the large,
horizontally flattened pectoral fins. The body is usually

Fig. 104. Shark (Dogfish), Ventral View.

Showing nostrils, mouth, gill slits, and anus.

rhomboidal, often wider than long. One form is called
the "barn-door skate." They live on the bottom, feeding
on mollusks, and have pavement teeth. Some have sharp

I70

Descriptive Zoology.

spines above the base of the tail, and are called " thorn-
backs " and "sting rays." Perhaps the largest of them is
the "devilfish," sometimes attaining a width of eighteen
feet and a weight of several tons.

Some of the rays have a compHcated electric apparatus,

Fig. 105. Common Skate (Ray).

Jaws and teeth (above); mouth and gill slits (below).
From Packard's Zoology.

with which they can give a strong shock to an animal with
which they come in contact. This serves both as a means
of defense and for securing prey. The one electric ray
found on the Atlantic coast has the scientific name Torpedo
and the common names " crampfish " and " numbfish."

THE BONY FISHES.

The great majority of fishes differ from the sharks and
rays as follows : —

I. The skeleton is bony instead of cartilaginous.

Pisces. 171

2. The gills are protected by a gill cover, so that there
is but one external opening.

3. The eggs are small and numerous.

The Spiny-rayed Fishes. — The perch is typical of a
large group of fishes, all of which have spiny rays. The
perch is widely distributed in fresh-water lakes and streams ;
the sea perch, or cunner, is common along the Atlantic
coast, and is so nearly like the yellow or "ringed" perch
that the descriptions and directions for dissection will apply
fairly well to it.

In the same family with the perch is the pike perch,
better known as the "wall-eye" or wall-eyed pike, an
excellent food fish. Among the perches are also the
darters, a most interesting family on account of their small
size and peculiar habits. They rest on the bottom, never
poising in the water like ordinary fishes ; they are found
in streams, in rapid currents, getting their food under

Fig. 106. Mackerel.

stones, etc. They swim by means of their pectoral fins,
coming to rest after the quick, darting motion that gives
them their name. One species is only from an inch to an
inch and a half long. Yet in some respects they are to be
classed among the most highly developed of fishes. They
may be caught in a minnow seine by taking pains to " keep
the lead line down," that is, by being careful to drag very

172

Descriptive Zoology,

close to the bottom. In keeping with the fact that they
stay on the bottom is the fact that most of them lack an
air bladder. They feed mostly on insect larvae.

The simfishes are a closely related family; these are
well known as having short, deep bodies, usually with
bright colors. More active than the sunfishes proper,
though in the same family, is the black bass, so well known
as a game fish. There are also the white bass, striped
bass, and yellow bass in fresh waters, and various kinds of
sea bass. Two important families of the spiny-rayed fishes
are the mackerels and the codfishes.

Fig. 107. Codfish.

Most of these fishes are very active and reckoned among
the " game fishes " on account of their resistance to being
caught and the skill required to capture them.

The Black Bass. — The black bass is probably more
sought by the scientific angler than any other fish in the
Central States. It is a fine type of the spiny-rayed fishes.

" The black bass is eminently an American fish ; he has
the faculty of asserting himself and making himself com-
pletely at home wherever placed. He is plucky, game,
brave, unyielding to the last when hooked. He has the

Pisces. 173

arrowy rush and vigor of a trout, the untiring strength and
bold leap of a salmon, while he has a system of fighting
tactics peculiarly his own. I consider him, inch for inch
and pound for pound, the gamest fish that swims." — J. A.
Henshall.

The Catfishes. — The catfishes are scaleless ; they have
long, tapering barbels ('* feelers ") around the mouth ; the
mouth is wide, and the head low and flat, adapting the fish
for a groveling life, skimming along the bottom. The
dorsal and the pectoral fins each have for the first ray a
very strong, stiff spine, with a jagged edge, by means of

Fig. 108. Catfish; Channel Cat.

which they inflict painful and probably poisonous wounds.
They seem to be lovers of muddy streams, and lead a
rather sluggish life. They abound in the Mississippi Val-
ley, where some species reach a weight of 150 pounds.
They are esteemed as food, as the flesh is of fair quality
and unusually free from bones.

The Suckers. — In this family are a number of forms,
such as the various suckers, the buffalo fishes, and carps,
including some carps that have been introduced from
Europe. The scales are large, with smooth borders ; such
scales are called cycloid scales. They all have a scaleless

174 Descriptive Zoology.

head and a sucking mouth, toothless, with soft lips capable
of downward extension; they feed to a large extent on
vegetable matter, hence have a long intestine, in marked
contrast with the short intestine of the carnivorous perch.
The air bladder is large, and is constricted into two or
three compartments, linked together sausagelike. The
air bladder communicates with the digestive tube. They
ascend streams in the spring to lay their eggs. Their flesh
is rather tasteless and full of bones ; still, they are largely
used as food, as they cost less than other fishes, being
caught in immense numbers in seines. Their sluggishness
contrasts sharply with the alertness of the game fishes.

Fig. 109. Atlantic Salmon.

From Kingsley's Zoology.

The Salmon Family. — The salmon is well known both
from its commercial importance and from its remarkable
migrations up rivers to spawn. It passes swift rapids and
leaps falls of considerable height. To this family also
belong the trout and the whitefish of the great lakes.

The Trout. — One of the daintiest of fishes, as well as
one of the most delicately flavored, is the trout. On
account of its wariness it is sought by the angler who
wishes to overmatch its cunning.

" This is the last generation of trout fishers. The chil-
dren will not be able to find any. Already there are well-

Pisces.

175

trodden paths by every stream in Maine, in New York, and
in Michigan. I know of but one river in North America
by the side of which you will find no paper collar or other
evidence of civilization. It is the Nameless River. Not
that trout will cease to be. They will be hatched by
machinery and raised in ponds, and fattened on chopped
liver, and grow flabby and lose their spots. The trout of

Fig. iio. The Rainbow Trout.

From Kellogg's Zoology.

the restaurant will not cease to be. He is no more like
the trout of the wild river than the fat and songless rice
bird is like the bobolink. Gross feeding and easy pond
life enervate and deprave him. The trout that the chil-
dren will know only by legend is the gold-sprinkled living
arrow of the white water, able to zigzag up the cataract,
able to loiter in the rapids, whose dainty meat is the glanc-
ing butterfly." — Myron W. Reed.

The Flatfishes. — As an example of this group we may
select the flounder found along the Altantic coast. These
fishes keep near the bottom, swimming on one side, and
the two eyes are both on the side that is uppermost. Per-
haps the most interesting fact concerning these odd fishes
is their development. At first they are symmetrical, with

176 Descriptive Zoology.

an eye on each side, and erect like other fishes ; gradually
the body turns over to one side, the cranium becomes
twisted, and the eye of the side that turns down travels
over to the upper side ; the upper side becomes dark, while
the under side is white or nearly so, whereas in the young
flounder both sides were colored alike. The sole and the
plaice belong to this family. The most important member,

Fig. III. Winter Flounder.

From Kingsley's Zoology.

however, is 'the halibut, which sometimes reaches a weight
of three or four hundred pounds.

Eels. — The eels have elongated, cylindrical bodies, with
minute scales or none. They have no ventral fins, and
swim or crawl through the mud by a snakelike motion.
They are active and very voracious, pushing their way under
stones and into holes after small fishes and crustaceans, on
which they feed. It is said that they can crawl a consider-
able distance on land, through wet grass, and that they
pass around falls and other obstructions in this way.

Flying Fish. — Certain marine fishes are called " flying
fishes." They do not really fly, but, by means of their long
pectoral fins, make long flying leaps through the air. They

Pisces.

177

make these leaps better against the wind than in the same
direction as the wind. Their leaps are probably somewhat
like the ** sailing " of birds.

THE GANOIDS.

We have in the United States four kinds of ganoids, the
gar pike, the sturgeon, the mudfish, and the spoonbill catfish

Fig. 112. Gar Pike; Gar.

The gar pike has a cylindrical body covered by rhom-
boidal bony scales. These scales are coated with enamel,
making a very strong and complete armor. The jaws ex-
tend, forming a long bony snout, the nostrils being at the
tip of the upper jaw. The teeth are sharp, and the fish
is voracious, but of rather sluggish habits. The tail is
slightly heterocercal. Three species are common in the
Mississippi and some of its tributaries : the long-nosed gar
(Fig. 112); the short-nosed gar; and the alligator gar,
which is said sometimes to attain a length of ten feet.

Fig. 113. Common Sturgeon.

After Goode. — From Kingsley's Zoology,

The sturgeon is decidedly like a shark in general ap-
pearance, with its strongly heterocercal tail, its projecting
snout, with the mouth well back on the ventral surface, and

178

Descriptive Zoology.

its cartilaginous skeleton. The skin is also rough like that
of a shark ; but in addition to the separate scales that give
roughness, there are several rows of bony plates, each with
a central projecting point. These rows of scales are not
set close together, one row of large scales being along the
back, with rows of smaller scales along the sides. The
sturgeon has a projectile toothless mouth, and feeds along
the bottom, sucking up worms, larvae, etc., from the mud.

The spoonbill catfish very much resembles a catfish, being
smooth-skinned, but has a long, paddle-shaped upper jaw
with which to stir up the mud from which it gets its food.

The mudfish, or bowfin, is, in the Mississippi Valley,
commonly called the " dogfish," an unfortunate term that

Fig. 114. Mudfish; Bowfin ; Grindle.

Dogfish (of Central States, but should not be confused with the shark called dogfish).

is likely to confuse it with the shark called by the same
name. The mudfish, as the name implies, lives in shallow
water, and is a very voracious fish. It is more nearly like
the ordinary bony fishes than the other ganoids, having a
pretty complete bony skeleton. Its flesh is soft, and gen-
erally considered as wholly unfit for food, but of late it is
beginning to be used. In some waters of the Mississippi
system it is very abundant.

These four fishes do not present many characteristics in
common, hence it is not strange that the authorities differ
greatly as to their classification. In the first place, it should

Pisces. 179

be noted that there are but few living ganoids ; these are
the survivors of a host that existed in earlier geologic
periods. Many of these fossil forms possess a heavy
armor, of which the gar shows a sample. It is also
noteworthy that North America has a majority of the
survivors. Most of them have heterocercal tails.

The most valuable feature for our consideration is the
air bladder, which is present in all, and in all is connected
with the gullet by a persistent open duct. This duct opens
on the dorsal side of the gullet except in one instance.
Further, the air bladder in most has an unusual supply of
blood, so that it serves to a considerable extent as a lung.
Both the mudfish and the gar pike often come to the sur-
face and emit bubbles and take in a fresh supply of air,

Fig. 115. LuNGFiSH.

After Boas. — From Kingsley's Zoology.

very much as do the mud puppy and the tadpole after the
lungs begin to develop. These two fishes are very tena-
cious of life when removed from the water, undoubtedly
because of the ability of the air bladder to act as a lung.
The ganoids thus foreshadow the lungfishes, as, in turn,
the lungfishes anticipate the Amphibia.

THE LUNGFISHES.

In the lungfishes the development of the air bladder as
a lung is much more complete than in any of the ganoids.
The nostrils open into the mouth cavity, which is not the

i8o Descriptive Zoology.

case with any other fishes. There is also a pulmonary
artery and a pulmonary vein, making the circulation much
more perfect. In keeping with this, the auricle is partially
divided into two compartments. There are only three or
four species, one in Australia, one in Africa, and one or
two in South America. The Australian form has a single
lung ; the others have the lungs double. The African
lungfish secures protection during the dry season by
burying itself in the mud, where it remains in a snugly
inclosed cavity. These " mud nests," as they are called,
have been dug up and the fish taken alive and uninjured to
Europe. Gills are present and permanently kept.

It is a general belief among naturalists that the Amphibia
originated from such lunged fishes as these we have been
considering. Why, indeed, should we hesitate to believe
that a race of animals has gradually changed from an
aquatic to a terrestrial life in long course of time, when we
have all seen this change take place in the individual frog
in a relatively short time ? Whether they were first led to
do this from the drying up of the water or from pollution
of the water, making it unfit for respiration, or whether
they were forced to adopt a land life from the competition
for a living in the water, or from some other causes or
conditions, who shall say ?

SUBCLASSES OF PISCES.

Class
Pisces.

' Subclass I. Elasmobranchii, sharks and rays.

f Teleostei, the bony
Subclass 2. Teleostomi. fishes.

Ganoidei, "ganoids."
^ Subclass 3. Dipnoi, the lungfishes.

CHAPTER XII.
BRANCH CHORDATA.

CLASS AMPHIBIA.
Example. — The Frog.

Where Frogs Live. — Frogs are usually found in or near
water. In the spring they congregate in ponds and pools
to lay their eggs. Later in the season they scatter, and
may be found at some distance from the water, but still in
moist places, such as near springs, swampy meadows, etc.
Even when they are spending most of the time in the
water they come out on the banks to catch insects.

How the Frog Progresses. — The frog has three modes of
locomotion — jumping, swimming, and creeping or walk-
ing. The latter mode is seldom used except to change its
position or cUmb up something on which to rest. The long,
muscular thighs enable the frog to make powerful leaps, by
which it rapidly escapes to the water when it is on shore
and alarmed. In swimming it folds the fore limbs along-
side the body and by the simultaneous strokes of the two
hind limbs, with the long, broad, webbed feet, makes rapid
progress. It is a model swimmer.

The Frog's Food and Method of Eating. — The frog
feeds chiefly on insects, though it also eats slugs, worms, and
various kinds of larvae. The writer has found the remains
of a mouse in the stomach of the common frog, and in the
stomach of a bullfrog a small bird entire ; but these cases
are exceptional. The frog catches insects — its main

i8i

I82

Descriptive Zoology

food — by means of the tongue. The tongue is attached
in front and free behind. Insects are caught by turning
the tongue forward quickly, the sticky mucus with which
the tongue is covered holding them securely. There are
fine teeth on the upper jaw and the roof of the mouth, but
these serve merely to hold the insect or slimy worm, while
it is being swallowed, and are not used for masticating the
food. The wide mouth narrows into the gullet, which is
really wide, since the animals captured are swallowed

Fig. ii6. Plan of Frog's Structure, Side View.

whole, but is kept closed by being " puckered up," as it
were. Back of the gullet is the rather large stomach.
The stomach narrows as it extends backwards, and is con-
tinued into the intestine, which, after one or two turns,
suddenly widens into the cloaca. Alongside the stomach
is the lobed liver ; between two of the lobes is the bile
sac, whose duct empties into the intestine a short distance
behind the stomach. The duct from the small pancreas joins
the bile duct a little before the latter enters the intestine.

Amphibia.

83

How the Frog Breathes. — The adult frog breathes chiefly
by means of lungs. In dissecting, the lungs may be found
collapsed ; in which case they are small and dark-colored.
When inflated they are of considerable size and of a beau-
tiful pinkish color, owing to the blood in the capillaries.
A frog's lung is not a mere air sac, with transparent walls,
as with most fishes. There is blood circulating in the
wall, and the wall is somewhat thickened, and has ridges
extending on the inside, which, to a limited extent, parti-

FiG. 117. Plan of Frog's Structure, Ventral View.

tion off the space into air vesicles, thus increasing the area
of the inside of the lungs, and consequently exposing more
blood to the action of the air contained within the lung.

In watching the breathing movements of the frog, three
actions are seen : first, the in-and-out movement of the
floor of the mouth ; second, occasional movements of the
side of the body ; third, opening and closing of the nos-
trils. When the floor of the mouth is lowered and the
nostrils are opened, air is taken into the mouth cavity ; if,
now, the nostrils are closed and the floor of the mouth

184 Descriptive Zoology.

raised, air is forced into the lungs. The gullet is kept
firmly closed so that air does not enter it, and the glottis, a
longitudinal sHt in the floor of the mouth just back of the
tongue, being opened at the right time, air freely enters
the lungs. The windpipe, or trachea, is extremely short,
dividing almost immediately to enter the two lungs. The
less frequent movements of the sides of the body seem to
be for driving air out. This is accompHshed by the action
of the muscles of the sides of the abdomen. From the
above it may be understood why a frog may be suffocated
by having its mouth held open for any considerable time.

The frog also breathes to a limited extent by means of
the skin. It has been noticed that the skin is always
moist, a condition necessary for this function. In cool
weather it will be noticed that frogs kept in aquariums
frequently sink to the bottom and remain there for a long
time. Of course the breathing movements then cease.
The diminished activity is accompanied by a reduced re-
spiratory need, and the. blood, circulating in the skin,
absorbs all the oxygen that is required.

Circulation of Blood in the Frog. — The heart consists of
one ventricle and two auricles. The right auricle receives
blood through the caval veins from all parts of the body
except the lungs; this blood is dark because it has been
deprived of its oxygen by the working tissues of the body ;
it is loaded with impurities which the tissues have given to
it. The left auricle receives blood from the lungs; this
blood is bright-colored from the oxygen just obtained in
the lungs ; it has also lost some carbon dioxid.

The two auricles contract at the same time and send
these two kinds of blood into one ventricle. How is one
ventricle to send the purer blood to the organs that need it,
and the impure blood to the organs whose work it is to

Amphibia. 185

remove impurities? Without attempting here to explain
this in detail, it may be stated that, owing to the way in
which the arteries branch from the ventricle, and to an
ingenious valve arrangement, (i) the best blood is sent to
the head, (2) the next best blood (somewhat mixed) is sent
to the body, and (3) the most impure to the lungs and skin.

The Lymphatic System. — In skinning the frog it is very noticeable
that the skin is attached only occasionally, leaving a free space between
the skin and muscles over the greater part of the body. In these
spaces is a more or less watery liquid, the lymph. Lymph is also found
in the body cavity around the internal organs. The lymph system is
part of the blood system. Lymph may be described as part of the
liquid of the blood that has soaked out of the regular blood tubes and
gotten into the lymph spaces. There are two pairs of contractile
" lymph hearts," one, whose pulsations may have been observed, near
the anus. The other pair is between the transverse processes of the
third and fourth vertebrae, and cannot readily be found.

Excretion of Impurities. — The lungs and skin remove
carbon dioxid from the blood as it circulates through them.
The nitrogenous waste matter is taken from the blood as
it flows through the kidneys. From each kidney a tube
called the ureter passes back to open into the cloaca on
its dorsal surface.

The Colors of the Frog. — The prevailing colors are green
and brown, though some are marked by black spots, and
sometimes these black spots are made more distinct by a
whitish border. The frog does not frequent bare ground,
but is usually to be found near plants, whether in water or
on land. Its colors are generally similar to the surround-
ings, so that it is not a very conspicuous object, and some-
times keen eyesight is needed to discover it even when in
plain view. By distending its lungs the frog easily floats
in water. When so floating only the top of the head is out
of water, with its three projecting points, the snout and

1 86 Descriptive Zoology.

the two eyes. In some kinds of frogs the head is more
distinctly green than other parts, so a little practice is
required before the collector readily discovers it as it rests
in the water, with the top of the head appearing among
green leaves.

The color is due to pigment cells in the deep layer of the
skin. These cells are branched, but can change their shape
and vary the color somewhat in accordance with the sur-
roundings. These cells may easily be observed in the skin
of the frog's web, and can hardly escape observation when
the circulation in the web is studied.

The Frog's Enemies.— Most of the larger snakes eat frogs
when they can get them. Many fishes take them greedily,
hence the frog is used as bait. A number of birds capture
frogs, including some of the hawks, certain waders, and
perhaps others.

The frog's color undoubtedly often keeps it from being
discovered, and when it is approached it can make use of
one, or both, of its two speedy modes of locomotion to make
good its escape ; concealment by protective resemblance
and escape by flight are its two safeguards, for it has no
weapons of defense.

How Frogs spend the Winter. — At the approach of freez-
ing weather frogs reassemble at the shore, and perhaps for
some time may be found at the surface during the warmer
part of the day, but stay at the bottom during the night or
during colder days. They finally dive deep into the mud, —
which is their winter resort. Here they hibernate, motion-
less, eyes closed, lungs emptied, with no breathing move-
ments, the heart beating feebly and slowly, till they are
revived by the returning warmth of spring.

Warm-blooded vs. Cold-blooded Animals. — The frog's nor-
mal temperature during the season when it is active is a

Amphibia. 187

little above the surrounding air or water. Its temperature
varies with the degree of its activity. In the winter when
it is buried in the mud its temperature sinks nearly to the
freezing point, for the lower layers of water have a tem-
perature of about 40° F. In other words, the frog's tem-
perature is variable y instead of constant as in the case of
mammals.

The Nervous System of the Frog. — The widest part of
the brain consists of the two optic lobes. In front of these
^e the two cerebral hemispheres. Barely separated from
the anterior ends of the cerebral hemispheres by a slight
groove are the olfactory lobes ; they seem to be a part of
the cerebral hemispheres. Back of the optic lobes, sepa-
rated by a depression, is the cerebellum, a narrow trans-
verse band. Beyond the cerebellum is the spinal bulb (see
also Fig. 167). There are ten pairs of cranial nerves.
There are also ten pairs of spinal nerves.

The Senses and Sense Organs of the Frog. — The promi-
nence of the frog's eyes has already been noticed. The
upper lid is thick and drops with the eye when it is with-
drawn. The thin under lid can be drawn more completely
over the eye and is often used when the upper lid remains
stationary. Back of the eye the eardrum is conspicuous.
From the inner surface of the tympanum extends the bony
rod called the " columella " to the inner ear, to which it
transmits the vibrations received by the tympanum. The
sense of taste is apparently well developed. All parts of
the skin seem to possess the sense of touch. The nostrils
open directly into the front of the mouth. Of the sense of
smell less is known than of the other senses.

Development of the Frog. — The eggs are formed in the
ovaries. When the eggs are mature the ovaries become
much folded and plaited and the egg-masses occupy a large

l88

Descriptive Zoology,

share of the space in the body cavity. The eggs finally are
set free in the body cavity ; they find their way to the open-

Nasal sac

Eye

Cerebru

^■^AjC./»»/»

Spinal bulb

Boundary between
Spinal cord

Spinal nerves ,

Branches connecting .-'

Sympathetic gan- *■'
glions

Sympathetic gan-
glion

Olfactory nerve

Optic nerve

Ganglion of fifth

nerve
Fifth nerve
Ganglion of vagus

nerve
Vagus nerve

First spinal nerve
Brachial nerve (arm)

Sympathetic nerve
trunk

Sympathetic gan.
glions

Sciatic nerve (thigh)

Fig. 118. Nervous System of Frog, Ventral View.

Amphibia. 189

ing at the inner end of the oviduct and as they pass along
the duct are coated with a layer of gelatinous material
which swells up after the eggs are laid, so that each Qgg
appears as a small, spherical, glassy body, with its upper
part of a dark color, and surrounded by a spherical mass of
clear, jelly like substance. In a few weeks the form of the
body begins to appear. The tail begins to vibrate, the sur-
rounding mucus breaks up and the tadpole emerges with gills
— very much Hke a tiny fish. For a short time there is no
mouth opening, and the little tadpole attaches itself to water-
weeds by suckers near the place where the mouth is to

Fig. 119. Development of a Toad.

From Packard's Zoology.

appear. After the mouth, with horny lips and jaws, is
developed, the tadpole feeds greedily on waterweeds and
grows rapidly. The external gills disappear and are replaced
by internal gills, which are concealed by a fold of skin which
incloses a gill chamber. There is an opening on the left
side of the body for the water to escape. The limbs de-
velop as little projections, like buds, on the sides of the
body ; but the anterior limbs are for a long time concealed
by the gill chamber and therefore appear to develop later
than the hinder pair. At first the tadpole swims, fishlike,
wholly by means of the tail, and it continues to do so long
after the limbs appear. It holds the limbs close by the side

190

Descriptive Zoology.

of the body and swims by the sidewise movements of the
tail. At this time the intestine is long and coiled spirally.
Then for a time the tadpole quits eating. It fasts, but is
maintained by the material from its tail, which is being
absorbed while a great transformation is taking place. The
horny lips and jaws are shed, the mouth becomes wider and
develops true jaws with teeth. The long, coiled intestine
becomes relatively short. The anterior limbs are pushed
out through the fold of the skin that inclosed them. Lungs
are developed, although they are at first but little used, the
tadpole coming to the surface occasionally to get a mouth-
ful of air; respiration is still chiefly accomplished by the

Fig. 120. The Siren ; Mud Eel.

Gills persistent.

gills, but the lungs come to be used more and the gills less
until finally the gills disappear. It was herbivorous ; now
it is carnivorous. Formerly strictly aquatic, it is now am-
phibian. In short, our tadpole has become a frog.

CLASSIFICATION OF AMPHIBIA.

The Siren. — The lowest of the amphibians is the siren
or mud eel. It is eel-like in form, having gills that persist
through life, and one pair of legs (the anterior). It lives
in the swamps of the Southern states and sometimes is
three feet long

Amphibia.

191

The Mud Puppy. — The mud puppy, or water dog, is a
little higher than the siren, having two pairs of legs. It
also has persistent external gills. It is found in the streams

Fig. 121. Necturus; Mud Puppy (North) ; Water Dog (South).

Gills retained thruout life.

of the Mississippi Valley and in the lakes of central New
York. It sometimes attains a length of two feet.

Fig. 122. Spotted Salamander.

The Salamanders. — The salamanders are still a step
higher. They have gills in the earlier stage, but shed them
when adult. They retain the tail, and, in swimming, fold

192 Descriptive Zoology.

the two pairs of limbs close to the body and swim by lat-
eral movements of the vertically flattened tail. Most
of the salamanders live on land, but they seek moist
places. The salamanders are often incorrectly called liz-
ards. They are pretty well distributed in temperate and
tropical regions. Most of them are of rather small size.
One form is used as food by the Mexicans. In some
forms the larva is larger than the adult. In unfavorable
conditions some of the larvae fail to transform, but perma-
nently, or at least indefinitely, retain the gills. Some
European forms fail to develop lungs. Many of the
salamanders reproduce the legs or tail when these
members have been lost. Like the other amphibians, the
salamanders go to the water to lay their eggs, and all sala-
manders, whether they lead a terrestrial life later or not,
spend their early life in the water, breathing by means of
gills. One family of salamanders are called newts or efts.
None of our amphibians are in any way poisonous or inju-
rious to man, though several of them are reputed to be so.

Frogs and Toads. — These are the highest of the amphib-
ians. They have lost, not only the gills, but also the
tail. They are not only fitted to Hve a truly terrestrial
life, like the salamanders, but are much more active than
the latter, having the hind limbs well developed for leap-
ing, whereas the two pairs of limbs in the salamander are
nearly equal, and it can, at best, only crawl.

One of the commonest of the frogs is the leopard frog,
so named from its spots. Quite similar to it in general
appearance is the pickerel frog. The green frog is green-
ish and brownish, with small dark spots. The bullfrog is
well known from its size and heavy voice.

The common toad has a rough-looking, warty skin, in
which are glands that secrete an irritating liquid for pro-

Amphibia. 193

tection. The toes are webbed, but not so completely as in
the frog. The hind Hmbs are less fully developed, and so
the toad merely hops, instead of jumping Uke the frog.
The frog has teeth in the upper jaw only, the toad in
neither jaw. The toad Hves away from the water ; still it
goes to the water to lay its eggs, and the young tadpoles
pass through the same stages of development as the frog.
The toad lays its eggs in strings, while those of the frog
are in masses. The tadpoles of the toad are usually
darker than those of the frog. The toad has the same
kind of tongue as the frog and catches insects in the same
way. The toad is usually of a duller color, corresponding
with its surroundings.

The tree toads or tree frogs are somewhat warty and
thus get the name " toads," but they are in a different
family from either frogs or toads. They are peculiar in
having the tips of the fingers and toes dilated into disks,
which adhere and thus aid in cHmbing. No matter how
high and dry they may live in trees, they return to the
water to lay their eggs. As is well known, they can
change their color through a considerable range, from
nearly white to nearly black, in keeping with the surface
on which they are resting. The hind limbs are elongated
as in other frogs, but, since they jump little, if any, the
muscles of these limbs are slightly developed, making
them slender instead of strong and muscular.

Though the larynx is poorly developed, nearly all the
frogs and toads have voices. The males have louder voices,
and most of these are well known, from the faint " peep "
of the little frogs and the shrill ** trill " of the tree toad to
the heavy bass notes of the bullfrog.

Some Peculiar Forms of Development. — In some of the islands of
the ocean where there are no marshes, the development is direct, the

194 Descriptive Zoology.

young being hatched in the form of the adult. A few forms bring forth
the young alive.

CHARACTERISTICS OF AMPHIBIA.

The Amphibia breathe by gills in the larval state, but
generally develop lungs in becoming adult. They have no
fin rays as with the fishes, but usually have paired limbs
with distinct fingers and toes.

Aquatic Life vs. Terrestrial Life. — Several lines of investigation
converge to prove that at one time the globe was entirely covered by
water. Of course until there was land there could be no land life.
What were the first forms of life on the land ? Did some of the
forms of aquatic animals gradually become fitted for living on land and
then desert the water ?

The study of the amphibia seems to throw some light on these ques-
tions. In the ganoid fishes we saw that the swim bladder had some cir-
culation of blood in its walls and that there was an opening from the
gullet into the swim bladder, which is, in action at least, a sort of rudi-
mentary lung. The lungfishes have the air bladder still more com-
pletely developed as a lung. The lungfishes came to the very door of
land life, but remained aquatic. The Amphibia boldly stepped over the
threshold and were, probably, among the first of the animal kingdom to
emerge from the water to live upon the land. This transition from life
in the water to life upon the land marks a great step upward. Perhaps it
would be hard to believe that any group of animals had made such a
profound change, if it were not for the fact that we see this same change
in the individual life of every amphibian.

Gradation among the Amphibia. — It is interesting and instructive to
observe the successive progress in the various groups of amphibians.
If we consider in succession the siren, mud puppy, salamander, and frog,
we see that they all have traveled along the same road, only some have
gone farther than others. They all start as limbless tadpoles, with gills,
practically in the same stage of development as the fishes. The siren
develops one pair of legs, retains the legs and gills, although developing
lungs, and goes no farther. The mud puppy makes a slight advance
by developing another pair of legs. It retains the two pairs of legs and
the gills, at the same time breathing, in part, by means of lungs. The
salamander takes a decided step upward when it sheds the gills and

Amphibia. 195

breathes by means of lungs. The frog goes through all these stages^
but rises to a still higher level by getting rid of the tail which it had in
its larval life. In short, each of these forms has gone through all the
stages represented by the forms below it in the scale, but has discardea
certain features and has advanced to a higher plane and leads a more
active life.

The life history of the frog, therefore, serves to review all the other
forms of amphibians below it in the scale. The temporary stages of the
frog's life represent the permanent form of the lower kinds of Amphibia.
To put it in another way, — they all start at the foot of the same stairs
at the fish level, so to speak ; the siren climbs up on the first step and
stops there ; the mud puppy makes one more step and rests content ;
the salamander mounts still higher by a step and has reached its high-
est point ; while the frog takes all of these steps and reaches out once
again and tops the series by getting on the highest step of the stairs.

This series illustrates a law which, though general, does not appear
so clear in some other groups. The stages of development of the
individuals of the higher groups recapitulate the development of the
group as a whole ; or, in other words, "the development of the individ-
ual epitomizes the development of the race."

DIFFERENCES BETWEEN FISHES AND AMPHIBIANS.

Fishes. Amphibians.

Persist through life Gills . . . May disappear in adult

Air bladder respiratory in lungfishes . Lungs . . . Present in adult

I Auricle, i Ventricle .... Heart . . .2 Auricles, i Ventricle

Fins with fin rays Limbs . . . Limbs with digits

Scales (usually) .... Exoskeleton . . Skin smooth (usually)
Not open to mouth (except lungfish) Nostrils . . . Open into mouth

ORDERS OF AMPHIBIA.

{Order i. Urodela .... Salamander
Order 2. Anura Frog
Order 3. Gymnophiona , . . Blind-snake

CHAPTER XIII.
BRANCH CHORDATA.

CLASS REPTILIA.

There are four principal forms of reptiles, represented
by the lizard, snake, turtle, and alligator.

THE LIZARDS.

General Characters of Lizards. — Lizards are scaly rep-
tiles, having, in the typical forms, two pairs of limbs and
an elongated body, with a long, tapering tail, frequently
twice as long as the rest of the body. The middle of each
vertebra of the tail has a thin layer of cartilage, at which
places the tail easily breaks off. The advantage of this
arrangement is readily seen. When attacked by an
enemy the chances are the lizard will be seized by the
tail, for he is probably trying to escape by flight. The
brittle tail breaks off, and as this constitutes the greater
part of the length, the pursuer thinks he has the main
part; at any rate, while he is holding this the curtailed
lizard may make good his escape. But the tail grows olit
again.

In capturing lizards, which often lie basking in the sun,
it is best to creep stealthily upon them till within arm's
length, and quickly dart the hand forward. Unfortunately,
in thus grasping them, the tail is in most cases broken off.

There are five toes, with claws, on each foot. There
are no external ears, but the tympanum is sunken, leaving

196

Reptilla.

197

a depression back of the eye. The eyes have movable
upper and lower lids. The teeth are attached to the ridge
or edge of the jaws, and are not set in sockets.

Lizards feed on insects, worms, and other small animals,
though a few forms are herbivorous.

Lizards are active in habits, some being called '* swifts."
They are found on the ground, more often in sandy soils,
on rocks, trees, walls, etc.,
being most abundant in
warm countries. There are
not many north of latitude
40°. A few live more or less
in the water, but they do
not have gills at any stage
of their lives.

Lizards lay eggs of com-
paratively large size, which
are covered by a tough
leathery or limy shell.

Many lizards are bril-
liantly colored, and some
have power to change their
color; most noted of these
are the chameleon, of the
old world, and the Anolis
(Fig. 123), found in the
Carolinas and Florida, which
readily changes from a
bright green to a dull brown
according to its surround-
ings. Put one of these fellows in a box with a lot of dead
pine needles, and note the color change. This lizard is
often sold under the name *' chameleon."

Fig. 123. Green Lizard.

From Kingsley's Comparative Zoology.

198 Descriptive Zoology.

The Chameleon. — The true chameleon is found in Africa. Its power
to change its color has been mentioned. It has a laterally compressed
body, with a prehensile tail. Its feet are fitted for climbing by having
two toes on one side and three on the other. The two eyes can move
independently of each other, and the tongue can be darted out four or
five inches after insects.

The Horned Toad. — This is a lizard with a broad, relatively short
body, with spines on the back of the head. It is found in the dry
regions of the Western and Southwestern states.

Fig. 124. The Gila Monster.

The only poisonous lizard. — From Kellogg's Zoology.

The "Gila Monster." — This is the largest of the lizards found in
the United States, being about eighteen inches long. It is found from
New Mexico south and west. It is brown, with red m^irkings. Its
bite is poisonous, though seldom fatal to man.

The Iguanas. — In Central and South America and the West Indies
are found the lizards called iguanas. They are about three feet long,
and are found on the lower branches of trees. They are used as a food
by the natives, and are said to be excellent eating.

The Monitors. — The monitors are found in Africa, Australia, and
the East Indies. They are the largest of living lizards, being five or
six feet long.

Differences between a Salamander and a Lizard. — Salamanders are
commonly called lizards. The two animals have a general resemblance
in form, both having elongated bodies, with two pairs of limbs and a
long tail. The following tabular statement shows important points of
difference : —
Salamander (Amphibian). Lizard (Reptile).

Smooth Skin : . . Scaly

Unarmed Toes With claws

Present in young Gills No gills at any stage

A metamorphosis Development Young like adult

Reptilia. 199

The Joint-snake. — Every one has heard of the glass-snake or joint-
snake, which is by no means rare in the Central states. The commonly
accepted story is that when struck it flies to pieces, and that the pieces
come together again, making the animal whole as before. The facts
are as follows : The glass snake is a lizard without legs, and with a tail
two or three times as long as the body proper; hence it looks very
much like a snake. A closer examination would show that it can shut
its eyes, which no snake can do. There is also a depression marking
the ear, not found in snakes. A groove along each side of the body is
also a feature never found in snakes. The tail is very brittle, as in all
lizards. When struck, the tail is easily broken off and broken into
several pieces, the short body usually crawling quickly away. No part
of the tail lives. The disappearance of the pieces of the tail is easily
accounted for by any one who knows how many animals are on the
lookout for something to eat. To one who knows the animaPs struc-
ture an explanation is easy ; it is also easy to comprehend how the
ignorant usually accept the popular story. If one can be obtained,
carefully compare it with a snake.

THE SNAKES.

Characteristics of Snakes. — The absence of limbs is not
distinctive, since the glass-snake is a legless lizard, and
some snakes have rudiments of hind limbs. In snakes ^

there are no movable eyelids, the eyes being covered by ^^Z'
the thin, transparent epidermis. The mouth is very dilat-/'^^
able, the lower jaw being held by extensible ligaments,
and the two halves of the lower jaw are also loosely con-
nected so they can be stretched apart during swallowing.
The tongue is long, soft, cylindric, and forked at the tip ;
it serves as an organ of touch, and has nothing to do with
the poison apparatus. The teeth are relatively small,
pointed backward, and serve to hold the prey and to a'y.in
swallowing. There is no breastbone. The number of
vertebrae is great, in the boa over four hundred. Ribs
begin on the second vertebra and continue the whole length
of the body cavity.

200 Descriptive Zoology.

Locomotion of Snakes. — The chief mode of locomotion in
a sinuous line is so well known that a double curve is desig-
nated as ** serpentine. " It should first be noted that along
the whole length of the ventral surface is a series of broad,
overlapping plates, — the scutes or ventral ^plates. By
means of these the snake "gets hold " of rough places, for
on a perfectly smooth surface it can make no progress. By
the winding, waveHke motion of its body it both pulls
and pushes itself along. The absence of limbs enables it
to glide through grass and weeds and into crevices and holes.
Snakes also glide along with the body straight. This is
accomplished by rhythmically drawing the ribs and scutes
forward and pushing them backward, or, as some express
it, by "walking on the ribs."

J'ood of Snakes. — Snakes are carnivorous and take only
living prey. This they swallow whole. The constrictors
wind the body around the victim and crush it. Our com-
mon black snake (blue racer) is a good example of a con-
strictor. Our commoner snakes feed on toads, frogs, birds,
etc. Garter snakes sometimes eat earthworms. Water
snakes catch fish, frogs, and other aquatic animals.

Process of Swallowing. — Birds are usually swallowed head
first. If the snake catches a frog by a hind leg, that part
leads the way in. The backward-pointing teeth prevent
escape. The two halves of the lower jaw are alternately
pushed forward and drawn backward, and the victim is
thus slowly drawn in. Meanwhile the salivary glands
lubricate the object.

The Organs of Digestion. — The gullet is as wide as the
mouth, and there is no constriction or line of demarcation
between it and the stomach. The posterior end of the
stomach is glandular. About halfway back in the body

Reptilia.

201

cavity the stomach ends
and is continued into
the intestine, which
pursues nearly a
straight course. Near
the posterior part of
the body cavity it
widens, forming the
cloaca. Alongside the
stomach is the long,
narrow liver ; from its
hinder end the bile duct
extends back to the bile
sac, and from this a
duct empties into the
intestine a little way
back of the stomach.
The pancreas, a pale,
roundish organ, also
pours its secretion
through a duct into the
intestine. Digestion is
a slow process, as might
be guessed from the
condition in which the
food is swallowed, and
the snake lies stupid
and inactive for a long
time after such a
" bolted " meal.

How the Snake
Breathes. — The right
lung is long and nar-

202 Descriptive Zoology.

row, and continues back, as a transparent air sac, through
most of the length of the body cavity. The left lung is
rudimentary, sometimes being so small it is difficult to see.
The windpipe is long, beginning very close to the front of
the floor of the mouth. This is regarded as an adaptation
to the mode of eating, so that the snake may not be suffo-
cated during the long and tedious process of swallowing.

Circulatory System. — The heart beat is slow and the
circulation not very active. The heart continues to beat
long after the head is severed. The temperature of the
blood varies with that of the surroundings.

Excretory Organs. — In the posterior part of the body
cavity are the two long, slender kidneys, whose ducts open
into the cloaca.

The Eggs and the Young. — Eggs are produced in two
long, narrow ovaries ; the oviducts also open into the
cloaca. ' Some snakes deposit their eggs in the earth,
though probably a majority bring forth the young alive.

Senses of Snakes. — Sight and touch are fairly well de-
veloped, though a study of snakes does not reveal a keen
sense of sight. Some snakes are affected by music, show-
ing a sense of hearing. Of their senses of smell and taste
we know but little.

Adaptations of Internal Organs to External Form. — We
have seen how the external form is adapted to the mode of
life. Let us now see how the internal organs are fitted to
the necessarily long, narrow space allotted to them. In
the first place the body cavity is so long that a moderately
long digestive tube is accommodated without the necessity of
coiling it, as in many animals. But one lung is developed,
and that one is long and narrow, whereas our bodies admit
of two relatively wide lungs placed side by side. The liver

Reptilia.

203

is long and slender, and its bile sac is behind it. Not only
are the ovaries (and spermaries) and kidneys slender, but
they are not directly opposite each other ; in short, every-
thing is arranged on the tandem plan. Yet the snake is
bilaterally symmetrical, in its fundamental plan, like other
vertebrates and the vast majority of animals.

Poisonous Snakes. — Some of the front upper teeth of
these snakes, called " fangs, " are especially adapted for in-
troducing poison. They are longer than the other teeth,

)iAMOND Rattlesnake.

From photograph by W. H. Frsher. — From Recreation, by permission of G. O. Shields.

can usually be erected or folded back, and have a hollow,
or groove, by which poison passes from the poison sac into
the wound by muscular pressure on the sac. The poison
gland is a modified form of salivary gland. This poison is
not a stomach poison, but a violent blood poison. Our
chief poisonous snakes are the rattlesnake, now becoming
rare in all thickly settled regions, the copperhead, and the
water moccasin of the South. Their abundance and the
danger from them are both grossly exaggerated. As an

204

Descriptive Zoology.

antidote, a hypodermic injection of permanganate of potash
(i to lOo), is by many now preferred to alcoholic liquor. In
India the cobra kills several thousand persons yearly.
(See The American Natural History. Hornaday.)
How Snakes protect Themselves. — (i) By their color,
(2) bj flight, (3) by their odor, (4) by jtheir poison.

Many snakes are colored so Hke their surroundings as to
be decidedly inconspicuous, and this is of advantage both

in escaping enemies and in
securing their prey. By their
noiseless mode of locomotion
they can, unobserved, ap-
proach a victim or elude a
pursuer. We are so familiar
with their stealthy move-
ments that we are not sur-
prised when we learn that
the words snake and sneak
are of the same origin;
nor do we wonder that there
has been a long-standing
enmity between man and serpent. Yet the majority of
snakes are entirely harmless, and are as much surprised as
we are when we " meet by chance." Many snakes have a
disagreeable odor which probably serves to protect them
from some enemies. Lastly, the poisonous snakes use their
poison to secure food and to protect themselves. Among
the enemies of snakes are to be reckoned several kinds of
birds, such as the shrikes and hawks, hogs, wild and domesti-
cated, bears (occasionally), and various other animals.

Molting. — At least once a year snakes shed the epi-
dermis over the entire body, even over the eyes. During
this process they arc dull-colored, and inactive.

*3: ^

Fig. 127.

Dissection of Head of
Rattlesnake.

Showing fangs and poison sac {p\. — From
Kingsley's Comparative Zoology.

Reptilla. I05

DIFFERENCES BETWEEN A SNAKE AND A "GLASS

SNAKE."

Snake. Glass Snake.

No lids Eyes Movable lids

Dilatable Mouth Not dilatable

Extensible Tongue ..... Not extensible

Invisible externally Ear Visible externally

Broad plates Ventral scales Small

Short, strong Tail Long, brittle

Absent ...... Lateral groove Present

THE TURTLES.

General Characters of Turtles. — In turtles the relatively
short and broad body is inclosed between two bony shields,
the dorsal one being called the carapace, and the ventral,
the plastron. The carapace is made up of (i) the widened
spines of the thoracic vertebrae, (2) the ribs, which have
widened and grown together, and (3) a series of marginal
plates. There is no breastbone, but the plastron is made
of a set of bony plates. Both carapace and plastron are
covered by a set of horny, epidermal scales which do not
coincide with the underlying bony plates. The "tortoise
shell" of commerce is made of the epidermal plates of the
big sea turtle known as the hawkbill turtle.

There are no teeth, but instead the jaws are horny. The
neck and tail are the only movable parts of the spinal
column, and these, with the legs, can be withdrawn so as
to be protected by the shell. In the boxshell turtle there
is a hinge in the plastron to make the protection more
complete by closing the shell. The sea turtles have pad-
dles, while the land turtles have feet, with more or less
distinct toes. Some of the sea turtles weigh as high as a
thousand pounds. The green turtles, so valued for soup,
are caught in the West Indies at night, when they come

2o6 Descriptive Zoology.

ashore to lay their eggs. Among the more noticeable of
our inland turtles are the fierce snapping turtle, the soft-
shell turtle, and the " gopher " of the South, which burrows
in the ground. The terrapins of Chesapeake Bay are
noted for their quality as food. All turtles bury their eggs,
and our northern forms all hibernate in the mud.

THE ALLIGATORS.

General Features. — The alligators and crocodiles are
Hke lizards in general form, but differ from them in several
important points. They swim well by means of the verti-
cally flattened tail. The skin is covered with horny-
scales, those of the back having corresponding underlying
bony plates. The teeth of alligators are set in sockets,
which is true of no animals below it in scale. The heart
is also more complete than in the other reptiles, having a
complete partition separating the ventricle into two parts.
The temperature is about that of the surrounding air or
water. The brain, though more highly developed than in
other reptiles, is small relative to the size of the body and
the skull. The alligators have a muscular, gizzardlike
stomach. The young feed on fishes and small animals,
but the full-grown alHgators seize mammals, for which they
lie in wait at the edge of the water until the animals come
down to drink or swim. The nostrils, eyes, and ears are
at the top of the head, so these reptiles can lie concealed,
with their main sense organs extending into the air to
discover their prey ; they very much resemble a stranded
log. The nostrils can be closed by a valve, which is
done when a victim is dragged under water to drown.
Alligators dig holes in the banks, in which they lay their
eggs, which are sometimes as large as those of a goose.

The alligators of our Southern states grow to a length of

Reptilia. 207

ten or twelve feet. Alligators are confined to the western
hemisphere, occurring in the Southern states, Central and
South America.

Crocodiles are found in both the old world and the
new. One species is found in southern Florida.

Extinct Reptiles. — In earlier geologic ages reptiles were very much
more numerous than at present. Not only were they more abundant,
but there were more kinds ; and many of them were large, some being
eighty feet in length. Some were lizardlike, with long, slender necks.
Others were fishlike. Some had resemblances to birds. The tracks of
many of these ancient reptiles in the mud have hardened into rock, and
have often been called " fossil bird tracks." Perhaps the most remark-
able were the flying reptiles. They are supposed to have been rather
batlike in appearance. The remains of these reptiles are found m rocks
in many parts of the world, and the age in which they were most preva-
lent is called by geologists the " Age of Reptiles.'"

General Characteristics of Reptilia. — Reptiles are cold-
blooded vertebrates, covered with scales, and when toes
are present they end in claws. There is no metamorphosis
after leaving the egg. There are no gills at any stage of
life. Reptiles produce large eggs which are covered by a
tough limy or leathery shell. Some reptiles are ovo-
viviparous. Reptiles show a decided advance beyond
amphibians in the development of the nervous system ;
in the respiratory system, since they breathe by lungs
after leaving the egg ; and in the circulatory system, the
heart of the alligator having four cavities, as in birds and
mammals.

CLASSIFICATION OF REPTILIA.

^ , „ fLacertilia — lizards.

I Order i. Squamata. i ^ , . ,.
(Ophidia — snakes.
Order 2. Chelonia — turtles.
Order 3. Crocodilia — alligators.

CHAPTER XIV.

BRANCH CHORDATA.

CLASS AVES.

Example. —The Common Pigeon.

Adaptation for Flight. — The pigeon is fitted for flying :
(i) by the wings, which, with their wide, strong, yet elastic
feathers, are air paddles of marvellous efficiency; (2) by
the powerful breast muscles which move the wingS-4-^(3)
by the lightness of the skeleton ; (4) by the air sacs through-
out the body, which render it more buoyant; (5) and, not
least, by the shape, being double pointed, so as to penetrate
the air with the least resistance.

Structure of a Feather. — Let us consider the structure of
one of the quill feathers. It consists primarily of two parts,
the shaft and the vane, or flattened part. The shaft is solid
so far as the vane extends, but the basal part is hollow, and
is called the quill. The two sides of the vane are unequal
in width, and the feathers overlap so that the wider side of
the vane is beneath. The vane is made up of side branches
called barbs, arranged in a close row. From each side of
each barb arise secondary branches, called barbules ; and
the barbules of adjacent barbs interlock by little hooked
ends, so that the whole vane is firm.

Feathers are developed from papillae of the skin. In a
growing feather it can be seen that the quill is full of pulp
supplied with blood. In the fully developed feather the

ao8

Aves. 209

dry, pithy remains of this pulp are found in the quill, which
is now narrowed at the base, but still shows an aperture.

Kinds of Feathers. — There are four principal kinds
of feathers : ( i ) The quills^ found on the wings and tail.
(2) The contour feathers, which have the same general
structure as the quills, but are smaller, and He close to
the body. They protect the body from bruises, and also
from cold, being the very best of non-conductors of heat.
Their mode of overlapping serves admirably for shedding
rain and for retaining the heat when flying through cold
air. (3) Doivuy feathers, which differ from the above in
not having the barbs fastened together by hooked barbules ;
the result is a loose, soft feather, well suited for retaining
h^at. These feathers, when present, are inside the contour
feathers, where we should expect to find them. The young
pigeon has downy feathers, but they disappear in the adult.
(4) The pmfcatJiers are fine, hairlike feathers, usually left
after the pigeon is plucked, and usually removed from fowls
by singeing. They show that they are feathers by a little
tuft of barbs at the tip.

Distribution of Feathers. — Feathers are not evenly dis-
tributed over the surface of the body ; but there are certain
areas from which they grow, and certain other areas from
which feathers never grow. By separating the feathers on
a bird's breast it may readily be seen that no feathers de-
velop there. There are also bare places on the sides of the
neck and in other places ; but the length of the feathers
and their mode of overlapping cover these bare spots, so
that most people hardly know of their existence.

The Pigeon»s Wing. — The wing, like our arm, consists of
three parts, the arm, forearm, and hand. The similarity
of the first and second of these to the corresponding part
of our arms is so evident that it needs no explanation. The

2IO

Descriptive Zoology.

V

tun^n

'^ny

;ai

f^ -^'^ /■

f

i^iy

Ftg. 128. External Features of a Bird.

From Kellogg's Zodlogy.

Aves. 2 1 1

front angle of the wing, or *'bend of the wing," as it is
called, corresponds to our wrist; but the hand is sharply
bent back upon the forearm when the wing is folded, a posi-
tion we cannot assume. When the wing is folded, the arm,
forearm, and hand lie alongside of each other Hke this, z.
Further, the hand is reduced to two fingers, bound together,
and the thumb, which every one has seen in the plucked
fowl. The thumb, with its feathers, is called the false wing.
The feathers borne on the hand are called primaries, and
those supported by the forearm are the secondaries. In
some cases a few of the inner feathers of the forearm are
called tertiaries. The wing is concave on the inside, mak-
ing it fit the body closely when the wing is folded.

The Flying Muscles. — To use such a wing effectively as
an air paddle, it is evident that there must be very strong
muscles. These we find in the breast. The bulk of the
breast is made up of two powerful muscles, which cover
nearly the whole of the ventral surface of the body. To
support these large muscles, and supply a basis for their
attachment so they can work, it is equally clear that a con-
siderable extent of bone is also a necessity ; hence the large
breastbone. Not only is the breastbone very large, but
along its middle line is a high ridge, the keel. Lying
between the body of the breastbone and the keel, and
attached to both, there is on each side the large pectoral
muscle, the two together constituting about one fifth of the
entire weight of the body. At the anterior end, each pec-
toral muscle narrows into a tendon, which is attached (in-
serted) to the bone of the upper arm (humerus). By the
shortening of this muscle the wing is pulled downwa,rd.
Two points must now be kept in mind: (i) the wing is
concave beneath, which enables it to ** catch " the air ;
(2) the wider side of the vane of each quill is on the under

212 Descriptive Zoology.

side, so when the wing is struck against the air, the resist
ance presses the vanes together in one continuous layer,
through which the air cannot pass. The result is that a
strong ** push " is made against the air, and by reaction the
bird is propelled upward or forward according to the direc-
tion of the wing stroke. In seeking the muscle that raises
the wing, one would naturally look on the dorsal surface in
the region of the shoulder ; but, oddly enough, the muscles
that raise the wings are also on the breast. Every one has
noticed in the well-cooked breast of a bird that the meat of
the breast separates into two parts, the outer part being
large and flat, the pectoral muscle just described. Inside
of this, lying in the angle between the body of the breast-
bone and the keel, is a slender muscle, somewhat triangu-
lar in cross section. This is the subclavian muscle. At
its anterior end it narrows into a tendon, which passes
up through a hole left between the bones that make the
shoulder; the tendon then turns and is attached to the
upper (dorsal) surface of the arm bone (humerus). When
the subclavian muscle shortens, this tendon acts as a pulley,
and elevates the wing. In raising the wing it is desirable
that there should be as little resistance as possible. This
condition is secured ( i ) by the convex outer surface of the
wing ; (2) by the fact that pressure on the outside of the
wing separates the quills and allows the air to pass through
with very little resistance.

The Legs and Feet. — The pigeon is a model flier. It
uses the feet but little, hence the legs and feet are small
and weak. Heavy legs and feet would be to the pigeon a
useless burden. The hind limb consists of three parts,
thigh, leg, and foot. The true heel is some distance from
the toes, where we cut off the foot in dressing a bird. The
part between the toes and the heel, usually covered with

Aves. 213

scales, is the tarsus. The pigeon has four toes, one extend-
ing backward and having two joints. Of the three front
toes, the inner has three joints, the middle four, and the
outer five. Each toe ends in a claw.

It should be noted that the hip joints are not only far
apart, but are very high on the body, being near the dorsal
surface. This enables the body of the bird to swing be-
tween its two points of support, somewhat like an ice-
pitcher on its two pivots. Since the bird is obliged to put
its head to the ground so frequently, the convenience of this
arrangement is apparent. When we stoop we realize that
we are awkwardly built for such a position. It would at
first seem that the bird's center of gravity is too far forward,
but the length of the toes must be taken into account.

Perching. — It is to be noticed that when a bird's leg is
drawn up close to its body, the toes are clenched at the
same time. This is due to the action of a tendon that
passes over the joints of the leg in such a way that when
the limb is bent the tendon is put on a strain and thus the
toes are flexed. So when the bird settles on its perch the
toes grasp the perch without active muscular effort ; this
helps answer the question, '' How does a bird stay securely
on its perch when asleep.-*" There are also muscles by
which the bird can voluntarily clutch without depending on
this purely mechanical arrangement.

The Pigeon's Shoulder Braces. — With such strong pull-
ing as the breast muscles give the wing, it will be seen that
the shoulder needs to be firmly braced, especially against
the strong pull of the pectoral in making the down stroke
of the wing. In the first place, the shoulder is braced
like our own by the collar bones, or clavicles, the two collar
bones uniting near their attachment to the anterior end of
the keel, together making the "wishbone." In addition

214 Descriptive Zoology.

to this brace there is an additional bone alongside of each
half of the wishbone, the coracoid bone, much stronger
than the collar bone itself. On the back the shoulder is
braced by the strong, curved shoulder blade.

To strengthen the body for the work of flying, the verte-
brae of the trunk are consolidated, the only parts of the
spinal column that are flexible being the neck and the tail.

The Head and Neck. — In many birds the beak is the only
organ capable of being used for grasping, hence the long,
flexible neck, which makes up for the above-mentioned
stiffness of the trunk. The bird must be able to reach the
ground, hence the length of the neck is proportioned to
that of the legs ; the head must also be able to reach any
part of the body. Some birds have as many as twenty-
four cervical vertebrae. In many birds the head must be
darted forward quickly to secure prey or in defense. The
horny beak is strong, yet light, and serves as a hand in
picking up small objects. Because of the quick motion of
a bird's head, as it picks objects out of the dirt, soft lips
would be too delicate. A head that requires such quick
handling needs to be light ; and in keeping with this re-
quirement there is an entire absence of teeth in all exist-
ing birds, though in a few cases rudiments of teeth are
found in the embryo. In the plucked bird it is found that
the neck is more slender than would appear from the out-
side, the feathers fiUing the angle between the neck and
the body, and making on the exterior a gradual transition,
where in the bare bird there is an abrupt change.

The Pigeon's Food and Digestive System. — Pigeons feed
chiefly on grains and other seeds. These are swallowed
whole, and pass into the crop, an enlargement of the gullet
situated in tront of the breast. Here seeds are moistened
and well soaked before they go farther. The crop serves

Aves.

21S

as a storing sac during the hasty gathering of food. In-
side of the body cavity is the stomach, which consists of
two very distinct parts ; the first part is the glandular
stomach, or proventriculus, and the second is known as the
gizzard. The gizzard is very strong, having thick muscular
walls. In it the seeds, only partially softened, are to be
ground. To aid this process small pebbles are swallowed.
It is clear, therefore, that its inner wall needs to be tough ;

Fig. 129. Internal Anatomy of a Pigeon.

it will not do to have the soft glands here, hence they are
placed out of the way, a little higher up the digestive tube
where the secretion can trickle down upon the food in the
grinding stomach. The intestine arises from the gizzard ;
first there is a long loop, the duodenum, in which lies the
pancreas. Its secretion is poured into the duodenum.
The liver is adjacent and the bile duct also empties into the
duodenum. The transition from the small intestine to the
large intestine is marked by two small, blind side branches,

21 6 Descriptive Zoology.

the ceca. The terminal portion of the digestive tube is
widened, and is called the cloaca. It receives three sets of
products, (i) the residue of digestion, (2) the eggs, and
(3) the excretion of the kidneys.

The Circulatory System of the Pigeon. — The circula-
tion of blood is very rapid in birds because of their great
activity. The heart is proportionally large ; it is com-
pletely divided into two halves, so that the blood moves
through one half of the heart from the lungs to the body,
and through the other half from the body to the lungs,
being pumped twice in the circuit instead of once as in
fishes. An important point to note is that the aorta turns
to the right instead of to the left as in our bodies.

How the Pigeon Breathes. — Respiration is exceedingly
active in a bird. Imagine yourself taking such violent ex-
ercise as that required for a bird to fly through the air at
the rate of a mile a minute. Would you not be "out of
breath " ? The bird's lungs are of fair size ; in addition
there are air sacs in all parts of the body, communicating
with the lungs, the bronchial tubes continuing on through
the lungs into these sacs. The lungs do not lie free in the
body cavity as in our bodies, but are attached to the dorsal
wall, fitting closely between the ribs. The air sacs are also
in communication with the hollows of the bones, which
adds to the buoyancy. The temperature of birds is higher
than that of any other animals, being about 1 10° F.

The movements of respiration in birds is pecuUar, in that
expiration is accomplished by active muscular effort, and
inspiration by elastic reaction, —just the opposite of the
processes of our bodies.

The Excretory System of the Pigeon. — The lungs serve
us organs of excretion, throwing off carbon dioxid. The

Aves. 217

kidneys are paired organs, lying embedded in the hollow of
the pelvis, each kidney being in three sections.

The Oil Gland. — On the rump, at the base of the tail, is
the conical oil gland. It is concealed by feathers, but
when the bird wishes to oil the feathers, oil is taken from
the gland by the beak and spread over them. The oil
glands are the only skin glands possessed by the bird,
there being no glands distributed over the skin as in many
other animals.

Nervous System of the Pigeon. — The brain is relatively
large. It is also wide in proportion to its length as com-
pared with the brains of reptiles and amphibians. The
anterior part of the brain consists of the two cerebral hemi-
spheres (see Fig. 167). Back of these, in the middle
line, is the rather large cerebellum, marked by transverse
grooves. On the sides of the cerebellum are the two
optic lobes. The whole nervous system is relatively large,
the brain and spinal cord in some of the smaller birds
constituting a greater proportion of the weight than in any
other animals.

The Senses of the Pigeon. — Sight is the most highly
developed of the bird's senses. The eye is very large in
proportion to the size of the head. The outer coat
(sclerotic) of the eye is strengthened by stiff sclerotic
plates. The sense of sight is keen, enabling the bird to
discover food and to escape enemies.

The sense of hearing is acute, the inner ear being well
developed. There is no outer ear, but the depression lead-
ing to the tympanum is easily to be found back of the
eye, though usually more or less concealed by feathers. The
sense of touch is general over the body. Taste is appar-
ently not very acute. While it is pretty generally believed
that birds, especially carrion eaters, have a keen sense of

21 8 Descriptive Zoology*

smell, yet experiment seems to show that this is not so
acute as supposed.

The Pigeon^s Voice. — The cooing of the pigeon is pro-
duced by air vibrations made in the windpipe, but not, as
in most animals with a true voice, in a larynx at the upper
part of the windpipe. In birds the organ of the voice is at
the lower end of the windpipe, where it forks to form the
two bronchi ; and it is called a syrinx instead of a larynx.
The bird uses the voice to utter cries of warning, to call
the young, and to attract attention in the mating season.
It is worthy of notice that the sweetest singers are not to
be found among the highly colored birds, but among those
of more subdued tints.

Origin of the Domesticated Pigeon. — All other varieties
of domesticated pigeons appear to have descended from
the rock pigeon of the old world. By carefully selecting
pigeons having certain peculiarities, and breeding from
these to the exclusion of other forms, in time we have
produced a large number of varieties of pigeons, known as
carriers, pouters, fantails, etc. This production of vari-
eties by interfering with the natural selection of mates is
known as artificial selection.

A Bird*s Egg. — Birds' eggs are proportionately large.
This might naturally be expected, since there is deposited
within the ^gg sufficient nourishment to form the chick in
resemblance to the adult. The eggs are formed in the
ovary, and it is interesting to find that but one ovary (the
left) is developed, though the right ovary is represented by
a rudiment. The eggs as produced by the ovary consist
simply of the yolk. On one side of the yolk is the germ
spot. As the yolk, which is the real ^gg, passes along the
oviduct, it has added to it first an enveloping mass of
transparent substance which is termed the " white of the

Aves. 219

e.gg'' or albumen. The word " albumen " (from album,
white) now stands for the class of substances having the
same essential composition as the clear part of the egg.
After the albumen is added to the yolk, the oviduct secretes
a limy shell which completes the egg. The eggs pass from
the oviduct through the cloaca on their way out.

Incubation. — Most birds incubate the eggs. They are
sometimes, laid on the bare ground, but generally in a more
or less carefully prepared nest. These nests vary from a
simple platform of sticks to the elaborate hanging nest of
the oriole, woven of grass and soft fibers, or the still more
ingenious nest of the tailor bird. It is to be noted that the
nest is "simply a cradle and not a home."

The germ spot always turns uppermost, so that the
developing embryo gets the heat from the body of the
incubating bird. During incubation there is an increase
in the amount of blood circulating in the area in contact
with the eggs, a provision for affording heat to them.

The Colors of Birds. — The colors of feathers are due to
two factors, first to certain coloring matters, or pigments,
and second to the structure of the feather, most of the
luster and iridescence being due to the latter. As a class
birds are highly ornamented. The males are usually more
highly ornamented than the females. Perhaps this is
because the females are safer, during incubation, with dull
colors. But in many families the sexes are colored alike.
The young generally resemble the adult female.

Molting. — Birds shed their feathers and renew them at
least once a year. If the molting takes place but once a
year, it is usually in the fall, but some birds also renew
their plumage in the spring. In rare cases there is a third
molt. Most birds shed their wing quills in pairs, succes-
sively, so that they are at no time deprived of the use of

220 Descriptive Zoology.

the wings ; but the ducks shed their wing quills all at once
and for a time are unable to fly. Some birds shed the
claws, and the puffin sheds the outer covering of the beak.

Migration of Birds. — Comparatively few of the birds
that we see during the year reside with us permanently.
If one makes a list of the birds, that remain through the
winter, he misses many of his summer acquaintances. The
crow, jay, nuthatch, chickadee, some of the woodpeckers,
several sparrows, the hawks and owls, and a few others
are left, when the rest have flown southward. Why do
they go ? The common answer is, *' Because they cannot
endure the cold." But if one examines the feathers he
finds little difference between the robin and the jay, or the
bluebird and the sparrow. It is chiefly a question of food.
The robin and the bluebird live mostly on insects and
worms. As winter approaches these birds can no longer
find this sort of food in northern latitudes, and they seek
a warmer climate, not so much because they cannot stand
the cold as because insects and worms cannot stand the
cold. Woodpeckers are insectivorous, yet remain; but
they can get the larvae from the trees about as well dur-
ing the winter as in the summer. The large majority of
the birds that remain with us during the winter are either
seed-eating birds, like the grouse and sparrows, or car-
nivorous, as the hawks and owls. Some are omnivorous,
like the crows and jays. Some birds, such as the swal-
lows, are very regular in the times of their migrations.
Others are irregular, and some birds migrate or not,
according to varying conditions. We must keep in mind
the bird's marvelous power of flight; in a short time he
can cover a very great distance.

Parasitic Birds. — Perhaps the most common example
of the parasitic habit is seen in the common cowbird.

Aves. 221

It lays its eggs in the nests of smaller birds. The eggs,
being larger than those of the owner of the nest, receive
the most heat, and are likely to hatch first and prevent the
development of the rightful heirs ; thus the usurper suc-
ceeds. Our cuckoo builds its own nest and should not be
confused with the English cuckoo, whose bad reputation is
sometimes transferred to his American namesake.

CHAPTER XV.
BRANCH CHORDATA.

CLASSIFICATION OF AVES.

Existing birds are divided into two great groups. All
flying birds have the keeled breastbone, and from this fact
of structure are placed together in the division Carinatae.
meaning " keeled." The ostrich has no keel on the breast-
bone, hence is placed in the division Ratitae, from a word
meaning ** raftlike," referring to the shape of its breastbone.

DIVISION I. — RATIT^.

The best-known representative of this division is the
African ostrich. It cannot fly, the wings being small ; but
it is a swift runner, equaling a horse in speed. The breast-
bone is not only without a keel, but is relatively very small,
as might be expected since there are no large flying
muscles. The feathers on the wings and tail have no
booklets on the barbules ; the result is a plume instead of
a firm vane as in the flying birds. These plumes have
been valued as ornaments from the earliest time, and now
the rearing of ostriches for the plumes is an important
industry in South Africa and southern California.

The ostrich is also noteworthy from its size, being the
largest of existing birds, standing from six to eight feet
high. It has but two toes on each foot. In the same
division are also the South American ostrich, the emu
of Australia, the cassowary of Australia and the East
Indies. The kiwi of New Zealand has bristlelike feathers,

Aves.

223

so that it appears to be covered with hair, and the nos-
trils open at the tip of the long beak. The Ratitae are
" overgrown degenerate birds that were once on the right
road for becoming flying fowl, but through greediness and

Fig. 130. South American Ostrich.

From Kingsley's Zoology.

idleness never reached the 'goal,' went back, indeed, and lost
their sternal keel, and almost lost their unexercised wings"
(Parker).

DIVISION II.— CARINAT.E.

This division includes all flying birds. All of the birds
in this part of the world are carinate. The breastbone

224

Descriptive Zoology.

is large and keeled to support the flying muscles. The
barbules have hooklets which unite the barbs, forming a
firm vane. The Carinatae are divided into a number of
orders.

The Diving Birds. — The diving birds have webbed (or
lobed) feet and are expert in swimming and diving. The
wings are usually small or rudimentary. In many the tail
is rudimentary. Our local examples are the grebes and

loons, though these are
little seen except by the
field naturalist, hunter, or
fisher. Their legs are set
far back in adaptation to
their main use, the result
being that they must stand
upright and can hardly
walk. The plumage is
thick and well oiled, to
fit them for diving. Water
does not penetrate be-
tween the feathers, so the
skin is not wet. The
grebes have lobed toes
and are about the size
of our smallest ducks. They dive Hke a flash when
alarmed, but it is not true that they can dive between the
flash of a gun and the time that the shot can reach them.
The grebe is commonly called "hell-diver." The loon is
our largest diver. Its peculiar cry, sometimes resembling
a hysterical laugh, has given rise to the expression, " crazy
as a loon." The loon does not try to escape pursuers by
flight, but dives and swims long distances under water, so
that it is seldom shot.

Fig. 131.

Pied-billed Grebe or
Hell-diver.

From Eckstorm's The Bird Book.

Aves.

225

The auks and puffins are found in vast numbers on
the coast of Labrador and northward, some having great
powers of flight.

Fig. 132. The Loon.

From Eckstorm's The Bird Book.

The penguins are correspondingly characteristic of Pata-
gonia and the Antarctic regions. Their wings are small
and paddlelike, and ^

are covered with scale-
like feathers.

The Long-winged
Swimmers. — This
group includes the
gulls and terns. They
are web-footed and
have long wings and
tail, with remarkable
power of flight. They
occasionally rest upon
the water, coming on
shore only to lay their eggs. They are mostly sea birds,
though some frequent inland lakes and rivers, and any one

Fig. 133. Herring Gull.

From Eckstorm's The Bird Book.

226

Descriptive Zoology.

who has taken a trip by steamer has watched them and
wondered at their tireless flight. The gulls have hooked
beaks, while those of terns are pointed and nearly straight ;
in both the bills are often bright-colored. They feed chiefly
on fishes, but some are scavengers, following ships.

The Tube-nosed Swimmers. — To this order belong the
f»^trels, which resemble the gulls except in having the nos-

FiG. 134. Petrel.

From Eckstorm's The Bird Book.

trils open as two parallel tubes on the top of the beak.
Perhaps best known, or at least most read about, are the
stormy petrels, or " Mother Carey's chickens." Closely
related also is the albatross of the southern hemisphere,
which has a spread of ten feet.

Aves.

227

The Totipalmate Birds. — As the name indicates, the
birds of this order have full-webbed feet ; that is, there
are not merely two webs between the three front toes, as
in ducks and m.ost web-footed birds, but there are three
full webs, the hind toe being connected by a web with the

Fig. 135. The Cormorant.

From Eckstorm's The Bird Book.

inner front toe. Our most familiar examples are the cor-
morants, but they are shy birds, found in the lakes and
larger streams. They are voracious fish eaters. Nearly
every one has seen the pelican, as it is frequent in zoologi-
cal gardens and menageries. The cormorant has a rudi-
ment of the throat pouch so conspicuous in the pelican.

228 Descriptive Zoology.

In the East Indies the peHcan is tamed and used in fish
ing, as is the cormorant in China.

The Ducks and Geese. — These birds have webbed feet,
with heavy, oily plumage. The body is flattened, and all
are fine swimmers. The bill is frequently broad, with a
sort of saw edge. The tongue is fleshy. In the geese and
fish ducks the bill is narrow. The swans belong to this

Fig. 136. Head of Pelican.

From Eckstorm's The Bird Book.

group. Our domesticated duck closely resembles the wild
mallard, from which it is descended. The downy feathers
are much used for pillows, etc. Some ducks dive well,
and live largely on fish, which diet gives their flesh a rank,
fishy flavor; but the fine flavor of the canvasback is
thought to be due to the wild celery on which it feeds.
The wood duck, and a few others, are exceptional in
nesting in trees, though, of course, near water. Ducks and

Aves.

229

geese attract attention by their migration in large flocks,
especially in the spring. But their former vast numbers have
been reduced, mainly by those who shoot them for market.

All the above-described orders are often classed together
as the " swimming birds."

Herons and Storks. — These are slender-bodied, long-
legged, and long-necked, with long, sharp bills, living
about the water and feeding chiefly on fishes, etc. They
are fitted for wading, not only by their long legs, but also

Fig. 137. Wood Duck.

From Kingsley's Zoology.

by the fact that the feathers extend only part way down
the tibia. The long neck is ordinarily kept bent in an
S-shape, and can be quickly darted out to seize food.
Among the herons are the big blue heron, seen along
the rivers and creeks, the white egret, the bittern or stake
driver, the night heron, and the little green heron. In the
breeding season the head bears long plumes that are much
sought as ornaments.

230 Descriptive Zoology.

The Cranes and Rails. — This group also consists of marsh
birds, usually with long legs and necks. The cranes are
large, the white or whooping crane having a very long
windpipe coiled in a hollow in the breastbone. The rails
are smaller birds, not larger than a hen. These are seldom
seen except in reedy swamps. The coot, or mud hen, is
common in marshes and reedy lakes ; it has a bill Hke a hen.
It is an excellent swimmer, but has lobed instead of webbed
feet. The flesh is rather rank ; but as ducks are becoming
more scarce, the coot is not unfrequently substituted.

The Shore Birds. — This order includes the snipes, plovers,
etc. Like the two preceding orders, its members usually
have long bills, neck, and legs. The three orders are often
spoken of together as the ** waders." The long, slender bill
is often soft and sensitive at the tip, to fit it for probing in the
mud for worms. Several of the snipes are highly esteemed
by epicures, especially the woodcock and "jacksnipe."

The plovers are found rather more on dry land ; they
have no hind toe. The golden plover is often seen in large
flocks during its migration, and nearly every one knows the
killdeer by the cry from which it gets its name.

The Gallinaceous Birds. — The Gallinae, or fowls, have
robust bodies, well-developed legs, strong, blunt bills and
claws. The hind toe is elevated, that is, is attached higher
than the other toes. They are poor fliers, having relatively
short wings. They are essentially ground birds, none
making their nests in trees. They feed chiefly on seeds
and grains, the crop and gizzard being well developed.
On account of their plump bodies and the excellent quality
of their flesh, they are valued as food. Other animals than
man prey upon them ; and as they live on the ground,
where prowling enemies can gain easy access to them, we
should expect to find them colored for protection ; and, in

Aves. 23 1

fact, they wear grays, browns, and blended colors resembling
grass, weeds, and brush. The turkey is a native American,
though bearing a foreign name. Except the turkey, all our
native Gallinae belong to the grouse family.

The quail is widely known as "bob-white." It is very
cunning, and holds its own fairly well when properly pro-
tected by law.

The partridge, or ruffed grouse, lives in the woods. On
account of its wildness, it persists where native forest still
stands. It makes a loud noise by beating its wings rapidly
(drumming).

The prairie hens once abounded on the prairies of
the Central states, but are fast disappearing. Even though
protected by law eleven months of the year, they seem
doomed to extermination. They lack the cunning of the
quail, and their size is a disadvantage. The cock has a
bare colored spot on each side of the neck. This is inflated
while making his booming noise in the mating season, and
gives him the appearance of having an orange on each side
of the neck.

The sage grouse (sage hen) is found on the Western
plains among the sage brush. Sage hens are very good to
eat early in the season, but later are often tainted by eating
sage leaves, which makes the flesh bitter. The sage hen
is pecuHar in lacking a gizzard.

One of the most interesting of the grouse is the ptarmi-
gan. It is a rock grouse. The American species is found
in the Rocky Mountains, living on the rocks above timber
line. The legs and feet are fully feathered down to the
base of the claws. It has in summer a mixed gray and
brown color that makes it inconspicuous on lichen-covered
rocks. In the winter it turns pure white, and in fall and
spring is partly gray and partly white in transition.

232

Descriptive Zoology.

Our common fowl are descendants of the jungle fowl of
India, which our ancestors took from a wild state and do-
mesticated. The guinea fowl, peafowl, and turkey are
other domesticated gallinaceous birds, these domesticated
forms all belonging to the pheasant family. It is remark-

FiG. 138. The Ruffed Grouse.

From Eckstorm's The Bird Book.

able that the breast muscles should retain their large size
when they are so little used. Of late, pheasants from the
old world have been introduced in various parts of this
country. The Gallinae are undoubtedly the most valuable
to man of any order of birds.

Aves. 23J

The Doves. — The doves are characterized by a soft,
swollen membrane, or cere, overhanging the nostrils at the
base of the bill. They are strong fliers, with heavy flying
muscles and small, weak legs. This is a small order. The
wild pigeon, formerly existing in countless numbers, is now
well-nigh extinct. The turtledove, or mourning dove, how-
ever, remains abundant in the Central and Western states,
finding abundant feed in the grain fields.

The Birds of Prey. — Birds of prey usually have stout,
hooked beaks and sharp, curved claws, fitting them for
clutching and tearing their prey. They do not have a
gizzard, not needing such a stomach for digesting flesh.
The colors are usually dull, the sexes generally being
colored alike. The females are usually larger than the
males. There are three principal forms of Raptores, illus-
trated by the hawk, the owl, and the vulture.

The hawks are the best examples of the order. They are
keen-eyed, strong of wing and leg. There is much un-
grounded prejudice against them, for, with the exception
of Cooper's hawk and the sharp-shinned hawk, most of
them do more good than harm, killing large numbers of
mice, especially field mice. The eagles belong to the same
family (Falconidae) as the hawks. The so-called "bald-
headed eagle " is not bald ; but in old age the feathers of
the head and neck are white, making the name "white-
headed eagle " appropriate. The adult is smaller than the
younger eagle. This bird hardly deserves to be chosen as
the emblem of this country, as he is a notorious robber.
Often he perches, waiting and watching, till an osprey, or
fishhawk, has captured a fish ; then he swoops down upon
him and snatches away the prize. The golden eagle is a
distinct species, characterized by being full-feathered down
to the toes.

234

Descriptive Zoology.

The owls have both eyes facing forward. The eyes are
large, and have very dilatable pupils, thus enabling them to
see well at night. Owls have a soft plumage and an almost
noiseless flight. They depend more on stealth than on
swiftness for securing their prey. They do much good by

jm .___,

Fig, 139. The Marsh Hawk.

From Grinnell's Our Feathered Friends,

destroying rats and mice. They swallow birds and mice
nearly whole ; later the bones, hair, and any other indigesti-
ble portions are ejected from the mouth. Many owls have
tufts of feathers called **ears," "ear tufts," or "horns,"
but these probably are merely ornamental. The great
horned owl is well known by its hoot, " hoo-hoo, hoo-hoo.

Aves.

^3S

hoo-hoo, hoo-hoo," the last note prolonged with a circum-
flex accent.

The common little screech owl shows an interesting varia-
tion in color. Two colors are found, a gray and a reddish.
It was at first thought they belonged to different species,
but these two colors have been found in young of the same
brood. The difference seem.s to have no relation to age,

Fig. 140. Turkey Buzzard.

From Grinnell's Our Feathered Friends.

sex, or geographical distribution, nor do there seem to be
intermediate individuals. There are evidently two styles
of dress with the screech owls. This occurrence of two
styles of plumage is known as *' color dimorphism."

The vultures are degenerate Raptores, usually carrion
eaters. The head and neck are usually bare, and the bill
and claws weaker than in the above-described forms. Many

236 Descriptive Zoology.

of them are large, and soar gracefully hour after hour high
in the sky ; but when they descend to earth they show their
disgusting nature. Yet they are useful as scavengers, and
are wisely protected by law, especially in the South. Our
only example in the Northern states is the turkey buzzard,
which has a spread of six feet. In the South is found also
the carrion crow. This must not be confused with our
common crow, which, though carnivorous, is classed with

Fig. 14T. Carolina Parrakeet.

From Kingsley's Zoology.

the Passeres, or perching birds. The condor of the Andes
is a vulture ; though feeding chiefly on carrion, it sometimes
kills lambs and other small animals. Exaggerated accounts
of its size and ferocity are common ; measurements do not
show that it exceeds a spread of eleven or twelve feet.

The Parrots. — Parrots have a soft, fleshy, mobile tongue,
and can learn to talk. They have the toes in pairs, and
can climb well. The bill is large and so strong they can

Aves.

237

crack hard nuts. Most of the group are tropical birds, as
the macaws and cockatoos, and have gorgeous colors.
The only example of the order found in the United States
is the parrakeet of Florida.

The Cuckoos. — The cuckoos have the toes in pairs, the
outer front toe having been turned backward. In the
same group are placed
the kingfishers, though
this order is confessedly a
" mixed lot " that were
thrown out of the old
group of "climbing
birds."

The Woodpeckers. —
The woodpeckers are
typical climbers, the feet
being zygodactyl, that is,
with two toes turned
forward and two back-
ward. In climbing, the
stiff tail feathers assist by
bracing against the tree
below. The bill is
straight, hard, and chisel- f^
like, the strong neck
muscles using it to drill
a hole through bark and
wood after insect larvae.
When the larva is reached,
it is secured by the slender tongue, hard and barbed at the
tip, which is darted out and withdrawn with force and pre-
cision. The mechanism for projecting the tongue can
hardly be understood without actual examination.. There

Fig. 142. Downy Woodpecker.

From Grinnell's Our Feathered Friends.

238

Descriptive Zoology.

''^li, :f.-^^

are two slender cartilaginous rods which pass backward
from the tongue under the angle of each jaw, up and for-
ward on top of the head, in some cases even nearly to the
tip of the bill. The cartilaginous rods furnish stiffness, so
that a muscular sheath can be effective. Woodpeckers do
good by destroying borers. Only one kind, the true sap

sucker, or yellow-beUied wood-

f w^ ^ V pecker, uses the wood or sap, thus

M ^KlA&dlR ^ being somewhat injurious^

■ WHHH Wk The Swifts and Humming

M ^hBh lA Birds. — The birds of this order

^K HEHuf wKlk ^^^^ long, pointed wings, the

mjk WKSL mHII primaries being especially elon-

lUifflk /^^iH^^JKHB gated. The feet are small and

weak. The swifts are well known
to every one under the name
" chimney swallows," but they
are not closely related to the true
swallows. The humming birds
are the smallest of birds and
among the most beautifully
colored. The tongue is long
and extensible, and is used in
securing insects from tubular flowers, over which they
are often seen hovering.

The nighthawk and whip-poor-will are in this order.
They are fitted for catching insects on the wing by the
very wide mouth, the gape extended far along each cheek,
while the bill itself is small and weak. These birds fly at
night or at dusk. When they light on a branch, they
always sit lengthwise, never crosswise, and, as they lie
quite flat and are of a grayish tint, they are very hard to
see.

Fig. 143. Nighthawk.

From Packard's Zoology.

Aves.

239

The Perching Birds. — This is the largest order of birds.
Its members have the toes fitted for perching, with three
toes turned forward and one backward, all on the sam.e
level; most of them are "tree" birds, and are small or
medium-sized. There are usually twelve tail feathers and
nine or ten primaries.

The flycatchers include the kingbird and pewee. The
crows and jays are known by their harsh voices, omnivo-
rous appetites, and thievish habits. They do harm by
eating the eggs and young of many birds. The black-
birds and orioles form a well-known family, including
the parasitic cowbird, the boboUnk, and meadow lark.
The sparrows, or finches, are the largest family of perchers.
They have stout, cone-shaped beaks, with the " corners of
the mouth drawn down."
Most of the sparrows are of
rather dull colors, streaked
grays, drabs, and browns pre-
vaiHng,as in the tree sparrow,
chipping sparrow, and snow-
bird. Still, many of these
have patches of yellow, white,
or chestnut feathers. Some
are conspicuously colored, as
the purple finch, wild canary,
or thistle bird, the indigobird,
and the cardinal and rose-
breasted grosbeaks.

The English sparrow was introduced into the United
States about 1850, with the hope that it might check the
ravages of the " cankerworm " and other tree-infesting
caterpillars. The importation was a failure. It is doubt-
ful if these sparrows do much good in the way of eating

Fig. 144. Kingbird.

From Packard's Zoology.

240 Descriptive Zoology.

obnoxious insects. Certain it is that the Enghsh sparrow
drives away many birds that were very useful in destroy-
ing such insects. The English sparrow is a bold, pugna-
cious bird; he makes himself at home, but drives from
home many of our fine birds, such as the bluebird, pewee,
and wren. This sparrow, like most sparrows, is mainly a
seed eater, and does considerable damage in this way. A
further charge against him is his dirty habits.

The swallows are another interesting family, comprising
the " swallow-tailed " barn swallow, the eave swallow, the

Fig. 145. Butcher Bird ; Shrike.

From Miller's My Saturday Bird Class.

bank swallow, which makes its nest in long, horizontal
holes in steep banks, and the half-domesticated martin.

The shrikes are hawklike in appearance and in habits,
having a hooked beak and sharp claws. They catch mice,
frogs, small birds, snakes, grasshoppers, etc., and impale
them on the thorns of hedges and other trees. From these
habits they are also called mouse hawks and butcher birds.
A large family of small birds called warblers live in tree
tops, and are not well known except to those who take
special pains to study them. The sprightly wrens are
placed in the same family with the mocking bird, catbird,
and brown thrush. These last three are superb singers.
Another fine songster is the wood thrush ; though placed in

Aves. 241

a different family, it resembles the brown thrush in hav-
ing a tawny back and a light-colored breast, with brown
spots, the tail being shorter than that of the brown thrush.
The mocking bird is more southern, occurring mainly
south of the latitude of the mouth of the Ohio River. The
nuthatch and chickadee remain through the winter, as they
feed on insects found beneath the bark of trees. The nut-
hatch has the chmbing habits of a woodpecker, but its

Fig. 146. Blue Jay.

From Grinnell's Our Feathered Friends.

toes are arranged as in perchers. It is not excelled as a
climber, going sideways or head downward, as well as up-
ward. Among the highest in development of all birds is
the bluebird, which, unfortunately, is growing rare in the
Central states, especially about towns, where it was formerly
common. Perhaps no bird ranks higher in its general
organization than that bird so dear to every American
child, the robin. '

242

Descriptive Zoology.

Fossil Birds. — In rocks in various parts of the world
have been found remains of various extinct birds. Some
of them were larger than any existing, — ten feet in height.
One egg has been found, the capacity of which equaled one
hundred and fifty hen's eggs. But more interesting than
the great size is the peculiar structure of some of these
ancient birds. Many of them possessed teeth, and some

Fig. 147. Meadow Lark.

From Grinnell's Our Feathered Friends.

of these teeth were set in sockets, a feature we did not
find till we reached the highest of the reptiles. One fossil,
found in Bavaria, had not only teeth, but also a long tail,
consisting of many vertebrae, with a pair of feathers
extending out on each side from each joint.

Relations of Birds and Reptiles. — Not only do fossil
remains show points of structure in common between these

Aves.

243

two groups, but if we compare the structure of modern birds
and reptiles, we find likenesses that are not apparent on
superficial examination. Feathers and scales are of the
same origin ; the bird has both. The feathers of the wing
of the penguin are scalelike. The head joins the first ver-
tebra in the same way in both by a single occipital condyle,

Fig. 148. Baltimore Oriole and Nest.

From Grinnell's Our Feathered Friends.

that is, the head pivots on a single rounded process, instead
of on two, as in our bodies. The tongue of a snake is
supported in the same way as in a bird, and both are more
or less protrusible. Both lay large eggs, and there are
points of development in common that cannot be con-
sidered here. All these facts, here scarcely hinted at, go
to show that birds have descended (or ascended)- from

244 Descriptive Zoology.

reptiles. Hence many authors include birds and reptiles
in the one group, Sauropsida, just as the fishes and am-
phibians are placed together in the group Ichthyopsida.

Game Birds. — The principal game birds are the various
kinds of grouse (the quail, prairie hen, partridge, sage hen),
the ducks and geese, and various wading birds, including
snipe, rails, plovers, etc. But the food value of these is
not great. All sportsmen who wish a continuation of these
game birds should agree in enacting such laws as shall
protect them so their numbers may not be greatly reduced.
The general sentiment is that they ought not to be killed
for market purposes, nor during the breeding season.

Value of Birds. — The value and importance of game
birds sinks into insignificance in comparison with the
smaller birds. When we stop to consider the ravages of
insects, those that infest the fields and orchards, forests
and groves, the many larvae at the roots and on the foli-
age, the caterpillars, cankerworms, etc. ; and on the other
hand the multitude of birds — mostly of small size — the
robin and bluebird, the cuckoos and warblers, flitting about
in the tree tops all day long in search of these noxious
insects, — when all these facts are weighed, we may well
raise the question whether, if all bird life on the globe
were destroyed, the earth would long continue habitable by
man. As it is, occasional plagues of insects strip large
areas of plants and bring on local famine. These birds
should be fully protected by law. Till lately the number
of many of these birds has rapidly decreased, owing to their
being killed for their plumage, to the collection of eggs,
and to wanton and aimless destruction. Besides game birds
none should be killed, except for scientific purposes, unless
they are themselves noxious, as crows and jays, the English
sparrow, a few hawks, and possibly a few others.

Aves.

245

General Characteristics of Birds. — The possession of
feathers is sufficient to distinguish birds from all other
animals. The consolidation of the thoracic vertebrae and
the pelvis is peculiar. The bones of the cranium are
united in one, the sutures disappearing early. The ribs
are provided with flat braces extending to adjoining ribs.
The breastbone is large, and usually has a well-developed
keel. The two collar bones (clavicles) unite to form a wish-
bone. Air sacs are connected with the lungs. The tem-
perature of the blood is high. The red corpuscles are
elliptical and have nuclei. The brain is relatively large,
the eye especially being large in proportion to the size
of the head. The organ of the voice is at the lower end of
the windpipe, instead of at the upper.

CLASSIFICATION OF BIRDS.

Division Ratitae

Class Aves <

Division Carinatse

ORDERS. EXAMPLES.

1. Struthiones Ostrich

2. Pygopodes Loon

3. Longipennes ..... Gull

4. Turbinares Petrel

5. Steganopodes .... Pelican

6. Anseres Duck

7. Herodiones Keron

8. Paludicolae . . . . Crane

9. Limicolae Snipe

10. Gallinse Quail

11. Culumbae Pigeon

12. Raptores Hawk

13. Psittaci Parrot

14. Coccyges Cuckoo

15. Pici Woodpeckei

16. Macrochires Nighthawk

17. Passeres Robin

CHAPTER XVI.
BRANCH CHORDATA.

CLASS MAMMALIA.
Example. — The Common Rabbit.

Habits. — The common gray rabbit is familiar to many
under the name of " cottontail" This name is due to the
white fur of the ventral surface of the tail. As the tail
is held erect, the white part is very conspicuous when the
rabbit is running away from the observer. Our rabbit
— unlike the EngHsh rabbit — does not burrow, though it
sometimes takes to holes to escape pursuit, and perhaps
lives in them when other shelter is not convenient. In
pleasant weather the rabbits stay most of the time in
rather open spaces, hiding in bunches of grass. They do
not make any nest at such places, but simply find, or make,
an opening in a convenient tuft of grass, where they squat.
Such place is called a ''form." In colder weather, especially
when there is snow, they find a more complete protection
in brush heaps, hedges, and patches of weeds, or even in
burrows. They are nocturnal, sitting quiet all day, or
coming out only in the cool part of the summer mornings
and evenings. But at night they come out and run about
for food, and many observers think they are very social and
enjoy playing together.

Covering of the Rabbit. — The rabbit has a covering of
hair. The bulk of the covering, the fur, is made up of
short, soft hairs. Among these, and more deeply embedded

246

Mammalia. , 247

in the skin, are a number of long, straight hairs with dark
tips. They make an admirable covering during the cold of
winter. The feet are also covered by hairs, and the inside
of the cheek is hair-lined.

The Rabbit^s Mode of Locomotion. — It should first be
observed that the hind limbs are much larger and stronger
than the fore limbs. The back and loins are well-muscled,
all fitting the rabbit for running. When it is undis-
turbed, and moving about in search of food, it simply
hops. But when frightened, it runs swiftly. In running,
the chief propelling power is the hind limbs, which, when
straightened, are efficient means in pushing the body for-
ward. Before each leap the body is doubled, or arched.
Then the body straightens by the action of the muscles of
the back and the hind limbs. At the end of the long leap
the rabbit aUghts on the front feet, but the long hind legs
swing forward, one on each side, straddling the fore legs,
so that the foremost tracks, in the set of tracks made al
each leap, are made by the hind feet, and the two smaller
tracks, which are closer together, are made by the front
feet, as follows : —

o hind o

front o o

feet o o

o feet o

Not unfrequently the rabbit sits erect, resting on the
whole length of the hind feet. Ordinarily the rabbit walks
or runs on the toes only. The true heel in the rabbit is
off the ground in running, and is where we usually cut off
the foot when dressing the rabbit.

Food of the Rabbit. — The rabbit is herbivorous, eating
clover, grass, etc., with an especial liking for many garden
vegetables. It is, therefore, commonly found around gar-

248 Descriptive Zoology.

dens and orchards. The rabbit likes such places, not only
on account of the food there found, but also because of the
shelter afforded by the grass and bushes. In winter, when
fresh vegetation is scarce, the rabbit eats twigs, especially
the buds and bark ; thus a brush heap of fresh cuttings
from such trees as the apple affords the rabbit both shel-
ter and food.

The Rabbit's Teeth. — At the front of the mouth are
two pairs of chisel-shaped teeth, the incisors. These teeth
are mainly composed of dentine. On their front surfaces is
a layer of hard enamel. The result of this hard front edge
is that in gnawing, the hinder edges of the teeth are worn
away faster and the teeth are kept constantly beveled ; in
other words, they are self-sharpening. These teeth grow
at the base of the roots as fast as they are worn away at
the outer ends. If one of these teeth should be broken
off, or otherwise destroyed, the opposing tooth would no
longer be worn down and would grow too long, and sooner
or later interfere with the process of eating and cause
starvation. Many cases of this kind among rodents have
been known. Back of the upper incisors is another, smaller
pair of teeth, also regarded as incisors, an arrangement pe-
culiar to the rabbits and not found in other rodents. Back
of the incisors is a considerable space without any teeth,
before the grinding teeth, or molars, are reached. This
space undoubtedly enables the rabbit to manage the mouth
better in gnawing, just as in most of our pinchers we have
a widened space back of the nipping jaws. The same
arrangement is found in the horse, cow, etc.

The molars are six above and five below, set in close
rows, and having ridges running crosswise. The direction
of these ridges must be considered in relation to the joint
by which the lower jaw articulates with the skull. This

250 Descriptive Zoology.

joint is not a regular hinge joint, such as we find in a cat,
which allows of little more motion than a door hinge.
The rounded knob at the upper end of each jawbone fits
into a groove which runs front-and-back, thus allowing the
jaw to be moved forward and back. If one watches a
rabbit chewing, he will see that this motion is character-
istic in place of the more decidedly lateral movement seen
when a cow is ruminating. The ridges of the upper and
lower molars, therefore, are drawn back and forth over
each other, thus effectively grinding the food.

The Process of Digestion. — There are four pairs of
salivary glands on each side of the head, which pour their
secretions into the mouth to aid in digestion. At the base
of the tongue is the epiglottis, a cartilaginous cover which
turns down over the opening into the windpipe when the
food passes over it on the way to the stomach. The gullet
extends through the thorax, piercing the diaphragm, and
enters the large stomach, which lies back of the diaphragm,
partly separated from it by the liver. On the liver is the
bile sac, from which the bile is poured into the first part
of the intestine, called the duodenum. The long, coiled
small intestine finally joins the large intestine, and at their
junction is a long, blind tube, or sac, the cecum. Near the
stomach is the pale pancreas, which empties its secretion
by a duct into the duodenum.

Since the rabbit eats food that is relatively poor in nour-
ishing material, it is obHged to eat a large amount ; and as
vegetable food, especially with a good deal of cellulose, is
difficult of digestion, we should expect to find the digestive
tube both long and capacious, and this is the case. The
intestine is about ten times the length of the rabbit's body.
While the rabbit sits in concealment during the day, the
slow process of digestion is going on.

Mammalia.

251

The Circulation of Blood in the Rabbit. — The rabbit's
circulation is essentially as in our bodies. The heart is
completely divided into two parts, the right and left halves.
The right half pumps the blood to the lungs, whence it
returns to the left half of the heart to be pumped to all the
other parts of the body through the main artery, called the
aorta. The heart is within a pericardium, situated between
the two lungs, and resting against the diaphragm, near the
ventral body wall.

How the Rabbit Breathes. — The rabbit's respiration, too,
is very like ours. The diaphragm is a thin sheet of muscle
that arches across the
body at about the pos-
terior border of the longer
ribs, separating the body
cavity completely into two
cavities, the anterior con-
taining the heart and
lungs, the posterior con-
taining the stomach and
intestines, with the liver,
pancreas, kidneys, blad-
der, etc. By the shorten-
ing of its muscle fibers
the diaphragm is moved
backward, thus drawing in the air. The muscles which
move the ribs in and out also do part of the work. The
lungs are similar to ours, being hght (hence called
"lights") and porous, all the air vesicles being reached
by minute branches of the bronchial tubes, which fork
from the windpipe. The temperature of the rabbit's
blood is considerably higher than our own, averaging 103^
or 104° F.

Fig. 150.

Cross Section of Abdomen
OF Mammal.

252 Descriptive Zoology.

The Excretory Organs of the Rabbit. — The lungs act as
excretory organs, throwing off carbon dioxid as well as ab-
sorbing oxygen. The kidneys also are organs of excretion.
The kidneys are bean-shaped bodies attached to the dorsal
wall of the abdominal cavity. To each kidney runs a branch
of the aorta, supplying it with blood, and from the kidney a
vein returns the blood to the postcaval vein. As the blood
flows through the kidney in fine tubes called capillaries, the
kidney removes from it certain impurities, especially the
waste matter that contains nitrogen. The excretion is con-
veyed backward by a tube called the ureter, and emptied
into the urinary bladder, an organ not possessed by the
birds or reptiles.

Enemies of the Rabbit. — Among the enemies of the rab-
bit are dogs, wolves, foxes, cats, both wild and domesticated,
minks, weasels, hawks, owls, and perhaps many others. In
addition to these larger foes, the rabbit is usually infested
by parasites, such as fleas, tapeworms, etc.

How the Rabbit escapes his Enemies. — The rabbit has
claws, but they are not very efficient as a means of defense.
Rabbits use their teeth in fighting one another, but these
avail nothing against their enemies. The rabbit is practi-
cally defenseless, and relies upon two means for protec-
tion, — the first is its color, and the second its speed of flight.
The prevailing color of the rabbit is gray, varied with some
blackish, and more or less tinged with yellowish brown. In
the summer he appears rather more rusty or tawny. He is
so Hke his surroundings that it takes a keen and practiced
eye to detect him when he sits perfectly quiet in his form.
This he usually does, relying on his color to protect him.
Besides his color, his position is an aid in concealment, for
he is snugly doubled up, the ears folded down closely along
the back, and the white tail is out of sight. He generally

Mammalia. 253

sits in the center of a tuft of grass, and frequently he
appears to select a small bunch of grass, just large enough
to cover him scantily, perhaps thinking that he will not be
looked for in such slight cover. Sometimes a rabbit will
start from his form when an enemy is at a distance, especially
if much noise is made ; at other times he may be approached
closely, and almost touched, before he will stir. When he
does start, it is usually with a dash ; and he generally runs
with great speed to another cover, often running through
hedges and other places that will prove an obstruction to
pursuers. If followed, especially by dogs, the rabbit fre-
quently runs in a circle, and after completing the circle,
suddenly jumps far to one side, thus throwing the follower
off the scent. Though speedy, the rabbit is not an enduring
runner. He carries too much weight. The bulky food and
the large amount he eats prove a handicap. His paunch
suggests that of the cow. A dog has the advantage. Being
a meat eater, he has a short intestine, whereas that of the
rabbit is long. The dog's food is concentrated, nutritious,
and quickly digested ; hence the dog is hght in the abdo-
men, where the rabbit is heavy. Further, the heart of the
dog is stronger relatively, and a strong heart is the chief
factor in long-windedness. But in spite of his relative short-
windedness, his running and his cunning often enable him
to escape.

Injury done by the Rabbit. — Rabbits do considerable
harm by gnawing the bark of young trees in orchards, and
in some places it is necessary to build a protection around
the trees to save them. The English rabbit, introduced
into Australia, has become a plague. In spite of all the
means that man has been able to devise, they multiply
beyond any checks that can be applied. High rewards
have been offered for any means that will exterminate

254 Descriptive Zoology.

them, and bounties are continually paid for killing them ;
they thrive in spite of all that can be done. The intro-
duction of contagious diseases has not been a success.

Uses of Rabbits. — In this country they are used only for
food, and that to a very slight extent ; but in Australia and
some other parts of the world the fur is saved and used in
making felt. This is an important industry, as practically
all our " derby " hats are made of rabbit fur. Most of the
fur goes to London to be dyed.

Development of the Rabbit. — The ovaries are small ovoid
bodies attached to the dorsal wall of the abdominal cavity,
posterior to the kidneys. The eggs are microscopic, and
when set free from the ovary, enter the free opening of the
oviducts, as in the case of the frog. The posterior end of
each oviduct is developed into an organ called the uterus,
for holding and nourishing the egg, which is here retained
till development to the form of the parent is reached. The
young are born alive, and for a time after birth they are
nourished by milk from the mammary glands of the mother.
From four to seven are usually in a litter, more commonly
five or six. As several litters may be produced during a
year, the rate of their increase is very rapid ; but their fa-
talities are enough to keep their numbers down in this part
of the world. The little " cottontails " are concealed in a
fur-lined nest, which is a pocketlike hole in the ground.

The Nervous System of the Rabbit. — The brain is fairly
well developed, but the rabbit has not a high intelligence; and
as in the other lower orders, the surface of the brain is nearly
smooth instead of convoluted, as is the case with brains of
the higher animals. The principal parts of the brain are
the cerebrum, with its two hemispheres tapering forward
into the olfactory lobes (see Fig. 167). Back of the cere-
brum is the irregular cerebellum, with a central and lateral

Mammalia. 255

lobes. From the ventral surface of the brain the spinal
bulb arises, and continues into the spinal column as the
spinal cord. From the brain arise twelve pairs of cranial
nerves, and from the spinal cord a series of paired spinal
nerves which supply the body.

The Senses of the Rabbit. — Sight and hearing are es-
pecially well developed. The eyes are prominently placed
on the sides of the head, so that the rabbit can see an enemy
approach from any direction. The ears are long, and can
be moved by muscles so as to turn in any direction to catch
the sound. Rabbits may not unfrequently be seen to sit
erect and prick up the ears as if suspicious of danger.
When at rest in concealment, the ears are laid flat on the
back. The sense of smell seems well developed. The nos-
trils are longitudinal slits at the end of the nose, and between
them is a cleft, from which fact we borrow the term " hare-
lip." This arrangement apparently gives greater mobility
to the hps in feeding, and in sniffing there is considerable
range of movement of the upper lip and nostrils. Taste
also appears to be fairly keen, judging by the rabbit's dis-
crimination in choice of foods. Microscopic examination
of the tongue shows essentially the same taste organs and
nerve supply as in our tongues. The sense of touch ap-
pears to be distributed all over the body, though prob-
ably more keen about the nose, especially through the long,
stiff hairs which we commonly call the "whiskers."

CHAPTER XVII.
BRANCH CHORDATA.

CLASSIFICATION OF MAMMALIA.
Subclass I. — Prototheria.

There are two subclasses of mammals, the Prototheria
and the Theria. The Prototheria nourish the young with
milk. They also show that they are mammals by their
hairy covering. But they reveal their relationship to birds
and reptiles by the fact that they lay eggs.

Fig. 151. Duckbill.

From Packard's Zoology, after Liitken.

In this subclass there is but one order, the Monotremata.
The order contains but three or four species, and there are
two chief forms, the duckbill and spiny ant-eater, both lim-
ited to Australia and adjacent islands.

256

Mammalia. 257

The duckbill has a horny bill similar to that of a duck.
Its habits are similar to those of a muskrat. It lives in
water, and has holes in the bank, which it can enter beneath
the water. The body is about as big as a cat's, though
it presents a " squatty " appearance, the legs being very
short. The feet are webbed and the tail is flattened. It is
covered by a soft, fine fur. The duckbill has rudiments of
teeth in the early stages of its life, but in the adult state
neither the duckbill nor the spiny ant-eater has any teeth.

The ant-eater is of about the same size as the duckbill.
The hairs are developed into strong, stiff, sharp spines.
The bill is conical, and a small mouth at the end permits
the extension of the slender tongue, with which it licks up
ants like other ant eaters. It lives in rocky ground.

SUBCLASS II. — THERIA.

The Theria include all the remaining mammals. In this
subclass the young are born alive, in the form of the adult.

The Marsupials. — Our only marsupial is the opossum.
This odd animal is well known, at least by report, on
account of its habit of feigning death when attacked. The
marsupials get the name from their most marked charac-
teristic, the possession of a pouch, or infolding of the skin
of the abdomen. Two peculiar bones extend forward from
the pelvis, toward the pouch ; they are called the mar-
supial bones, as they support the pouch. The young are
born in a very immature condition, and are transferred to
the pouch, where they are nursed. The young are kept a
long time developing in the pouch, and, after they become
self-helpful, occasionally take refuge in the pouch. The
opossum is almost omnivorous, eating insects, eggs, and
birds, the teeth being of the carnivorous type. The opossum
is a good climber, and has a hairless, scaly, prehensile tail.

258

Descriptive Zoology.

Opossums are very tenacious of life, and it is commonly
reported that after a ** possum " has been severely pounded
and ''every bone in its body broken," it later gets up and
crawls away. The following are some facts of structure

Fig. 152, Opossum.

From photograph from Recreation, by permission of G, O. Shields.

that may explain such reports. First, the skin and hair
make a thick protective covering, under which is usually a
thick layer of fat. The chewing muscles extend far up
on the top of the head, meeting in the middle Hne. The

Mammalia. 259

skull is therefore well protected, so that it may receive a
severe mauling and not be much the worse, except for
external bruises. The opossum is of a low order of intelli-
gence, and appears stupid, both when free and in confine-
ment. It has not sense enough to become a pet.

The kangaroo is another well-known marsupial. The
story of its development is about the same as that of the
opossum, but the mode of life is different. The hind legs
are excessively developed, and the animal hops with
"record-breaking" power, seldom putting the feeble fore
legs to the ground. When standing, the strong, muscular
tail aids in supporting the body, forming a third leg, so to
speak. The kangaroo is entirely herbivorous. There are
many other marsupials in AustraUa, and, in fact, with the
exception of the opossums, all the living marsupials are
confined to the Australian region. Many countries yield
fossil remains of marsupials, some of large size, showing
that Australia contains the remnants of this peculiar, but
once widely distributed race. It is further interesting to
note that Australia has no other native mammals than the
marsupials, except possibly the dingo, or wild dog, which
some believe to have been introduced.

PLACENTAL MAMMALS.

All the mammals above the marsupials are born in a
more mature condition.

The Edentates. — This order includes the sloths, arma-
dillos, etc. They are not wholly toothless, as the name
would indicate, but the teeth, when present, are simple or
imperfect. They are mostly tropical, one armadillo occur-
ring in southwestern Texas.

The sloths are herbivorous and tree-inhabiting. They
climb, hanging under limbs by their hooked claws, and as

26o

Descriptive Zoology.

they proceed, strip off the leaves. On the ground they
are almost helpless. The extinct slothUke megatherium
was as large as a rhinoceros.

The armadillos have a scaly or horny development of
the skin for protection ; some have also the power of roll-
ing themselves into a ball, still further securing safety.

The ant-eaters lack teeth ; they secure insects by pro-
truding the long, sticky tongue.

The Gnawers. — The gnawers, or rodents, are character-
ized by chisel-shaped incisor teeth, which keep wearing
away at the tip and as continually growing from the root.

Fig. 153. Nine-handed Armadillo.

From Packard, after Llitken.

In all but the hares the incisors are two above and two
below. There are no canine teeth, and there is a wide
space between the incisors and the molars. They are
chiefly herbivorous, and the digestive tube is long. They
constitute the largest family of mammals, and are espe-
cially numerous in individuals.

The Hares. -^ The general characteristics of this family
have been illustrated in the description of the rabbit.
Besides our common gray rabbit, there are found in the
Southern states the marsh hare and the water hare ; in the
North, the northern hare, which turns white in winter;
on the Western plains, the big jack rabbit.

Mammalia. 261

Porcupines. — The porcupines are distinguished by hav-
ing sharp spines, which are really modified hairs, and are
scattered among the longer hairs of the ordinary type so
that the spines are ordinarily not very conspicuous. The
spines are especially developed on the tail and on the pos-
terior parts of the body. When the porcupine is attacked
by an enemy, and especially if cornered, he turns his back
toward his pursuer and draws the skin of the body forward,
so that the quills point outward in all directions, and any
attempt to seize him is met by a quick side stroke of the
tail. The quills have a very sharp tip, near which are a
series of backward-projecting barbs. They are also very
loosely attached at the base. The result is that the quills
readily pierce the soft skin of an enemy, become detached
from the porcupine, and remain sticking in the wound.
These facts are the sole foundation of the once widely ac-
cepted belief that the porcupine has the power to shoot
his quills into his pursuer. In the West cattle often come
in contact with porcupines and have their legs and noses
stuck full of quills. On account of the backward-project-
ing barbs the quills cannot fall out, but keep working their
way in deeper and deeper, making bad festering sores.
On this account stockmen hate porcupines and usually
shoot them on sight. In the lumber regions of the North
porcupines also prove a nuisance, — in another way, how-
ever. They gnaw into the handles of axes, oars, or any
wooden-handled implement, especially those that have been
used, apparently for the sake of the salt that comes from
perspiration. Hence tools are not left lying on the ground,
but axes are stuck into trees with the handles standing far
out, oars are laid up in bushes, etc. Porcupines are very
stupid, being so well protected by their spines that they
do not need to use their wits to escape an enemy.

262

Descriptive Zoology.

Rats and Mice. — The rats and mice are of many kinds
and of vast numbers. Man has adopted some kinds of
animals, but these creatures may be said to have adopted
man. They are universal attendants on civilization and
are as cosmopolitan as man himself. The length of time
that they have been associated with man is hinted at
by the fact that the word for mouse, in essentially the

Fig. 154. Chip.nh^xk.
From photograph from Recreation, by permission of G. O. Shields.

same form, is found in many languages. Though they have
many enemies besides man, it seems impossible to exter-
minate them, for they are protected in many ways, espe-
cially by their nocturnal habits, and, as Coues says, by
their very insignificance.

Beavers. — The largest rodent found in the United

Mammalia.

263

States is the beaver. It has webbed hind feet and a broad,
flat, scaly tail. All have read of its remarkable intelli-
gence and skill in felling trees and in constructing dams.
It was formerly widely distributed, but is now rare, owing
not merely to the fact that it has been trapped for its fur,
but also to the spread of civilization itself.

Squirrels. — The squirrels are a very interesting group,
not only on account of their active and graceful movements,

Fig. 155. Common Mole.

but also on account of their human trait of laying up pro-
visions and their human mode of eating. Most attractive
are the tree squirrels, including the fox squirrel, the gray
squirrel, the red squirrel, and the flying squirrel. The
woodchuck, prairie dog, and gophers hve in the ground.
The true gophers have large cheek pouches in which they
carry out the soil in digging their burrows.

The Insect Eaters. — This order is best represented by
our common mole, whose work of raising a ridge of sod is

264 Descriptive Zoology.

familiar to all. They make these ridges in burrowing for
earthworms and grubs, which are their main food. They
are well fitted for digging by the very large front feet and
strong muscles of the frOnt legs. Since they live in dark-
ness, the eyes have become rudimentary, sometimes con-
cealed by the skin. The teeth are like those of a diminu-
tive flesh eater. The nose is long, bare at the tip, and very
sensitive. There are no external ears. The shrews are
mousehke and are probably often mistaken for mice, as
the front feet are not enlarged as in the moles ; but the
nose is more pointed, and one look at the teeth would show
that a shrew is not a "gnawer." This order also includes
the hedgehog of the old world, which has the hairs devel-
oped as sharp spines. The fact that both the hedgehog
and porcupine have sharp spines leads to confusion. It is
unfortunate that many writers are either uninformed or
careless in this matter and further extend an already wide-
spread error. The two animals are entirely distinct, and
the following tabular statement may aid in showing their
points of difference : —

DIFFERENCES BETWEEN A HEDGEHOG AND A

PORCUPINE.

Hedgehog. Porcupine.

Insectivora Order Rodentia

Conical points Teeth . . . Chisel-shaped incisors

Insects, etc Food Herbage

Not barbed [ j j Barbed

Firmly attached ^ ^"^ ^ I . . . . Loosely attached

Less than a foot Size .... Two feet or more

Old world Habitat . . Both old world and new

The Bats. — The bats of this country are insectivorous,
and would undoubtedly be classed with the preceding
order if they were not flyers. The wing is a fold of skin

Mammalia.

265

supported by the arm and the excessively elongated fingers;
the fold in our bats extends to and includes the tail. The
thumb is free from the wing mem-
brane and has a hooked claw by
which the bat can hang, but usually
when at rest it hangs head down-
ward by the hooked claws of the
hind Hmbs. Every one is familiar
with the flight of our bats as they
zigzag after insects. Bats are chiefly
nocturnal. There is much super-
stition concerning them. There are
in the tropics some blood-
sucking bats, but ours ^
are not only harmless f
but beneficial. Our bats ^
hibernate in caves, hoi- ^
low trees, etc. The large c
bats of the East Indies, §
known as flying foxes,
are fruit eaters.

The Whales. — Though living con-
tinually in water, whales are true
mammals; they bring forth their
young alive and nourish them by
means of milk. The fore limbs are
developed into flippers. The tail is
horizontally flattened, and its two
lobes are called flukes. Whales are
devoid of hair. The whalebone whale
has in its mouth a long series of
fringed baleen plates (whalebone), which serve as strainers.
The whale ingulfs whole schools of crustaceans, jelly-

266 Descriptive Zoology.

fishes, etc., and the water passes through these strainers
and out at the sides of the mouth. Underneath the skin is
a thick layer of fat which furnishes the whale oil. Such a
layer of fat protects this warm-blooded animal in the icy
water of the arctic seas. Since the discovery of our oil
fields the whale fishery has declined. The ''spouting" of
whales is not due to a column of water, but to mucus and
the condensed moisture of the breath.

Whales over fifty feet long are not often taken, though
the sperm whale is sometimes seventy-five feet, and the
"sulphur-bottom," found in the Pacific, is said to reach even
a hundred feet. It is the largest living animal. Porpoises
are smaller members of the same group.

The Sea Cows. — Some authors class these with the
whales, but they are herbivorous animals, having grinding
molars and a hairy covering. They seem to stand between
the whales and the ungulates. They live in the mouths of
large rivers ; the manatee is found in Florida and on the
west coast of Africa, the dugo'ng in India and Australia.
They are sometimes killed for their flesh, which is said to
be very much like beef.

The Hoofed Mammals. — The horse and cow may stand
as examples of this order, the ungulates. The hoofs are
excessive developments of what correspond to our nails or
the claws of other animals. In many forms the hoof en-
cases the whole of the lower surface of the foot. It appears
to be a special adaptation for the support of heavy animals,
many of which have to run rapidly over rough or even
rocky ground. The number of toes is typically five, though
no living ungulate has more than four. They are all
digitigrade, — that is, they walk on the toes. They are all
herbivorous, with teeth adapted for grinding. This is a
large order, and its members are of a large average size.

Mammalia. 267

In its domesticated forms it is probably the most useful of
any order to man, as from it are derived beasts of burden.
Members of this order also furnish us with food (meat, milk,
cheese, butter), leather, etc. The domestication of the horse,
cattle, sheep, etc., dates so far back that we know not what
were the wild forms from which they have descended. The
ungulates are divided into two groups, according as the
number of toes is odd or even, — the odd-toed group being
called Perrissodactyls, and the even-toed, Artiodactyls.

The Perissodactyls. — These forms have an odd number
of toes, as shown in the horse, rhinoceros, and tapir.

The Horse. — The horses now in this country are not
natives, but were introduced from the old world ; the
Indians did not know the horse till after what we call the
" discovery " of America. Still, America did have horses
in earher geologic periods, and the history of the develop-
ment of the horse, as shown by fossil remains (largely
found in this country), is exceedingly interesting. The
earliest form was about the size of a fox, and had four
well-developed toes in front, with a rudiment of a fifth
and three toes behind. Later appears a form with four
toes in front and three behind. Then came a horse about
as large as a sheep, with only three fully developed toes
in front, the fourth represented by a rudiment, but still
having three toes in the hind foot. Later still the outer
toe became reduced to a mere remnant. Then came a form
about the size of a donkey, with three toes all around ;
the middle toe persisting and the two on each side becom-
ing dwarfed. Finally, the one-toed horse was evolved, the
single toe being the middle one of the five, that is, corre-
sponding to our middle toes and middle fingers.

The Tapir. — The tapirs are found in South America
and Sumatra. They have four toes in front and three

268

Descriptive Zoology.

behind. The snout is prolonged, suggesting the proboscis of

the elephant, but its relationship is plainly with the horse.

The Rhinoceros. — The rhinoceros has three toes all

Mammalia. 269

around. It is peculiar in having a horn on the top of
the snout. In some species there are two horns, not paired,
however, but one in front of the other. These animals are
found in Africa and East India.

The Artiodactyls. — The artiodactyls, or even-toed un-
gulates, have either two or four toes. These are symmetri-
cally arranged on each side of a median cleft ; hence they
are spoken of as " cloven-footed" animals. Lowest among
the even-toed ungulates are the hippopotamus and the
swine. A species of wild hog, the peccary, inhabits Central
and South America, extending into Texas. It is a slender,
active, fearless animal, in marked contrast to our inactive,
fat-burdened domestic hog. The swine are omnivorous,
the other ungulates are almost strictly herbivorous.

Except the camel, nearly all the artiodactyls have four
toes, — two well developed and two rudimentary. The well-
developed toes are the third and fourth, the first toe (cor-
responding to our great toe and thumb) being wanting.
The second and fifth toes are small, but usually with
distinct hoofs ; they are shorter and back of the two main
parts of the hoof. These rudimentary hoofs are commonly
called the "dewclaws." They do not ordinarily reach the
ground, and are of little if any use, except in the reindeer.

The Ruminants. — With the exception of the hippopota-
mus and the swine, all the even-toed ungulates are cud
chewers and have complex stomachs. As an example, let
us consider the cow. There are no upper incisors ; grass
and herbage are bitten or broken off by pressing the lower
incisors against the hard, toothless pad of the upper jaw.
The molars are well developed, and the lateral chewing
motions of the jaw are well known. In keeping with this
lateral motion, the ridges on the crowns of the molars run
lengthwise in wavy lines. The stomach consists of four

270

Descriptive Zoology.

compartments. When the food is cropped it is swallowed
without chewing. It passes into the large paunch, or first
stomach ; when the ruminant lies down to rest, the soaked
fodder is passed into the small second stomach, the honey-
comb or reticulum, where it is formed into distinct masses
and returned to the mouth for thorough mastication. It
again goes down the gullet, this time to the third stomach,
the psalterium, or manyplies, whence it enters the true
stomach, or fourth stomach, sometimes called the rennet.

The intestine is very long, be-
tween twenty and thirty times
the length of the body. The
ruminants need a large quantity
of food, hence it is easy to see
how it is of advantage to them
to be able to gather their food
quickly, retire to a place of con-
cealment, and digest it at their
leisure, as many of them are
comparatively defenseless. The
males of all the ruminants, except
the camels, have horns, and in
many species the females also
possess them, though usually much smaller than those of the
male.

The Hollow-horned Ruminants. — In cattle, sheep, goats,
and antelopes, the horn consists of a bony core, covered
with a layer of horn, which is not shed except in the case
of the pronghorn antelope of our Western plains.

Sheep. — The rams have large, curved horns, which they
use for butting when fighting. Our native sheep is the
Rocky Mountain, or bighorn sheep, so named from its
immense horns. These, in the old rams, become very much

Fig. 158. Diagram of the
Stomach of a Ruminant.

Showing the course of the food.

From Kingsley's Comparative

Zoology.

Mammalia.

271

battered. Hence arose the story, long widely accepted,
that they jump down precipices, alighting on their horns.
Since the ewes and lambs can go anywhere the rams can,
the absurdity of the account is evident. They are remark-

Lamb. Ram. Ewe.

Fig. 159. Mountain Sheep Family.

From photograph of some of the author's trophies.

able climbers, walking securely on a narrow ledge, perhaps
over a sheer precipice of a thousand feet, with the utmost
unconcern. They are wary animals, usually having a sen-

272 Descriptive Zoology.

tinel, commonly an old ram, posted on a high point of rock,
on the lookout for enemies. They seem to expect attack
from below, so the hunter tries to get above them. They
stay most of the time above timber line.

. Goats. — The Rocky Mountain goat dwells in equally
inaccessible mountain tops. Its color is pure white, though
its coat is usually dingy from the habit of sunning itself in
a bed of dust. Its white coat seems odd for a wild animal.
But when one sees it in its home, up among snow banks

Fig. 160. Rocky Mountain Goat.

From photograph of specimen mounted by L. L. Dyche, in Camp Fires of a Naturalist.
By permission of D. Appleton & Co.

and light-colored rocks, it seems well adapted to its sur-
roundings. It has small, smooth, black horns. Mountain
goats are rather stupid animals. The main difficulties
in hunting them are due to the steepness of ascent and
the rarefied condition of the air.

The Buffalo. — The American bison, usually called
'* buffalo," is now nearly extinct. Buffaloes once roamed

Mammalia.

'^1^

in countless herds over the plains and prairies of almost
all of the United States; to-day probably the only wild
herd in the country is in the Yellowstone Park, and it
numbers hardly more than fifty. There are probably a
limited number in British Columbia. Once the mainstay
of the Indians, furnishing them with food, clothing, and
tents (tepees), they were
doomed to give way before
an advancing civilization.

The Antelope. — The prong-
horn, or antelope of our
Western plains, is a peculiar
animal, the only member of
its family. It stands be-
tween the cattle and the
deer families. It has hol-
low horns, which are shed
annually. The bony core is
a projection from the skull
and is never shed. It is
very swift-footed and wary,
keen of eye and nose. Like
most of our wild ruminants,
it has a white rump. When

hunted it usually runs to a ridge and stops to watch.
Instead of getting out of sight of its pursuer, its policy
is to keep its enemy in sight, but at a safe distance.
The antelope is rapidly disappearing and is doomed to
extermination.

The Solid-horned Ruminants — Deer. — The deer family in
this country includes three species of deer, and the elk,
moose, and caribou. Except in the caribou, only the males
have horns. The horns, which are solid, are shed annually,

Fig. i6i. Antelope.

From Forest and Stream.

274

Descriptive Zoology.

usually ill December or January. They grow out again,
with an added prong for each of the first six or eight years.
Till fully grown the horns, or antlers, as they are often
called, are covered with a soft fur, and are said to be " in
the velvet." When the horns are mature this skin diee

Fig. 162. Whitetatl Deer. Horns in the " Velvet."

From Recreation, by permission of G. O. Shields.

and peels off, the owner assisting by rubbing them against
shrubs and small trees. The two common species of deer
are the whitetail and the blacktail deer. The whitetail
deer is probably identical with the Virginia deer or red
deer. It is the most widely distributed form, extending
from Maine to Florida, and westward to the Rocky Moun-

Mammalia.

27 <;

tains, usually keeping in lowlands. The term " red deer "
IS inappropriate, as all our deer are red when in their
summer coat, turning grayish in the fall. The blacktail
is Western, preferring mountains or hilly country. The
tip of the tail is black. This deer is also called " mule
deer," on account of its very large ears. The horns of the

Fig. 163. Blacktail Deer.

From Forest and Stream.

two species branch differently (see Figs. 162 and 163).
The elk (see Frontispiece) is larger than the other deer,
sometimes weighing eight hundred and perhaps a thousand
pounds. A bull elk surpasses any of the stags of the
old world. Elk are being reduced in number and bid fair
to be exterminated, since they cannot hide so cunningly
as deer.

276

Descriptive Zoology.

The deer family is peculiar in lacking the bile sac.
Deer shed their coats, m the summer time being reddish,
or "in the red," as the hunters say; while in the winter
they are grayish, or "in the blue." In the summer the
males of the elk and deer keep by themselves, ranging

Fig. 164. Moose.

From Forest and Stream.

high on the mountain sides, often upon the rocks near
timber line, while the does and fawns are more likely to be
found on lower slopes or in the valleys.

In hunting squirrels, the hunter has only two senses to
guard against, sight and hearing. But in hunting deer the

Mammalia. 277

hunter must not only keep out of sight and out of hearing,
but must also avoid detection by a third sense, — that of
smell. If he attempts to approach this game from the
windward side, they are almost sure to detect him and to
escape, often without his being aware of their presence,
unless he afterward discovers their tracks.

The moose is an awkward-looking animal, with its long
hump nose. The antlers are spread out into a flattened
"blade" near the tips. The moose lives in marshy for-
ests. There is a considerable number in northern Maine,
Nova Scotia, Alaska, and in British Columbia. A few
remain in Idaho, in the northwestern part of Montana, and
in the region of Yellowstone Park. The moose and deer
feed almost entirely on twigs and leaves, that is, they
"browse," while elk feed to a considerable extent on grass,
like our domesticated cattle.

The Camel. — The camel has but two toes, with large,
soft pads. The hump is a storehouse of fat. They can
go without water longer than most animals, but this is no
more than might be expected of an animal accustomed
to living in a desert country.

The Giraffe. —The giraffe is remarkable for the extreme
length of its neck. Nevertheless, it has but seven cervical
vertebrae, the same number that we have, the increase
being due to the lengthening of the individual vertebrae.

The Elephants. — The elephants are essentially ungu-
lates, having five toes, each incased in its own hoof ; but
on account of the peculiar development of the nose into a
trunk, or proboscis, most authors place them in a separate
order. The excessively long snout is flexible, very muscu-
lar, and serves as a hand in conveying food to the mouth.
This arrangement seems especially desirable for an animal

278 Descriptive Zoology.

with long, stiff legs and a very short neck. Even if he
were not stiff-legged and short-necked, it would be incon-
venient for him to dispense with the trunk so long as he
retains the tusks. These are the long upper incisors,
which are of solid ivory, the slight amount of enamel
which originally covered the tips soon wearing away.
Elephants are herbivorous and have one large grinding
tooth in each half-jaw. The skull is not heavy in proportion
to its size, as it has many large air spaces. The skin re-
tains a few scattered hairs, with a distinct tuft at the end
of the tail. Two species of elephants are found, one in
India, the other in Africa. Still larger than the elephants
were their (now extinct) relatives, the mastodon and the
mammoth.

The Flesh Eaters. — The flesh eaters, or beasts of prey,
are fitted for their life (i) by their activity; (2) by their
sharp teeth, especially the long canines ; (3) by the claws,
usually sharp and strong ; (4) by their color, usually in har-
mony with their surroundings. The lower jaw is so hinged
that only an up-and-down, or true hinge motion, is per-
mitted ; this should be considered in comparison with the
lateral jaw movements of ungulates and the gliding for-
ward-and-back of the rodents. Instead of being flat-topped,
the molars are somewhat like saw-teeth, the upper and
lower shutting past each other like shear blades. The
flesh eaters have simple stomachs and relatively short in-
testines, as the digestion of flesh is short and easy as com-
pared with that of vegetable food. The senses are generally
very acute. As there is considerable variation in adapta-
tion to the conditions of life, let us consider four types of
flesh eaters as represented by the cat, dog, bear, and seal.

The Cats. — Cats are distinguished from the other beasts
of prey by having the claws retractile, that is, they can be

Mammalia. 279

withdrawn into a sheath, where they are kept most of the
time, the animal walking on pads developed on the next to
the last joint of each toe. These pads enable the cats to
walk noiselessly, and this is an important trait, as they
capture their prey by lying in wait or by creeping near it
stealthily, then suddenly pouncing upon it. In a bright
light the pupils are reduced to a narrow vertical sHt. In
the dark they dilate widely ; thus they are fitted for their
nocturnal habits.

Our biggest cat is the cougar or puma, also called the
American panther, and in the West known altogether as the
mountain lion. Its body is about as thick as that of a
sheep and somewhat longer, with a long tail. It is tawny
brownish yellow above, paler beneath. Though fierce
when wounded or cornered, it is a sneaking, cowardly
creature, few instances being known of its attacking a
human being. It follows mountain sheep and other mam-
mals, ready to seize the young or the sickly or wounded
adults. It is found from British Columbia to Patagonia.
The wild-cat and lynx are smaller and are short-tailed,
being in some localities called " bobcats." Other cats are
the Hon, tiger, leopard, jaguar, etc.

The Dogs. — Dogs have the nose more pointed than the
cats. The claws are blunt and not retractile. The dog-
like form includes the wolves, jackals, and foxes. Most
of this group capture their prey by running it down, instead
of by stealth as in the cat tribe, though the fox is rather
catlike in this respect. Proverbial for his cunning, the
fox remains in thickly settled districts, not disdaining birds
that are domesticated. We have two species of wolves.
The prairie wolf, or coyote, has a sneaking, cowardly dis-
position. When an Indian wishes to express his utmost
contempt for an individual he calls him a coyote. The

28o

Descriptive Zoology.

timber wolf is larger and does considerable injury by kill
ing calves and lambs. A bounty is paid for wolf scalps.
Wolves are little to be feared in this country.

The hyenas are between the cats and the dogs. They
have heavy shoulders and fore Umbs, also strong jaws and

Fro. 165. Grizzly Bear, ttrom Photograph.

From Recreation, by permission of G. O. Shields.

teeth to crush bones. They are the scavengers among
the beasts of prey, Hke the vulture among the birds of
prey.

Both the cats and the dogs walk on the toes, hence are
said to be digitigrade.

The Bears. — Bears walk on the whole flat of the foot and
are therefore called plantigrade. Bears are less distinctly
carnivorous than the above groups. They live largely on
berries when they can get them. They eat many insects,

Mammalia. 281

turning over logs and stones and devouring the beetles,
worms, and larvae. They are, in fact, omnivorous and
not only in their food, but in their mode of feeding, re-
semble hogs. The ferocity of bears is greatly exaggerated.
They are extremely shy animals, usually on the lookout
for danger ; even when feeding they look around at short
intervals. One common mode of hunting them is to watch
a carcass of some large animal. When a bear discovers
such a "feast" he feeds greedily, and either stays in the
neighborhood or returns regularly till it is all consumed.
The hunter lies in wait or approaches when the bear is
feeding, usually at dawn or at dusk. The approach must
be made with the utmost care from the leeward, or the bear
is gone without being seen. A bear has no wish to culti-
vate man's acquaintance. But a wounded bear is a most
desperate and dangerous foe. He is quick on his feet and
strikes like a prize fighter, a single blow from his mighty
arm, with its long claws, often completely disemboweHng
a victim. In rare instances a bear, when discovered feed-
ing, becomes enraged and shows fight. Aside from these
conditions almost the only occasion when a bear " begins
a fight " is when a female with cubs is met ; even then she
often ignominiously takes to flight. Though clumsy in
appearance, the bear is a swift runner. In the fall bears
usually become very fat. Through most of the winter they
hibernate, or "hole up," as the hunters say, in a cave of
rocks or under the roots of a big tree. North America
has four kinds of bears : the polar bear ; the grizzly,
including the silvertip ; the black bear, including the cin-
namon bear; and the big brown bear of Alaska.

The raccoon is very much like a diminutive bear, not
only in its plantigrade feet, but also in its food habits.
Coons are shrewd creatures, and make good pets.

282 Descriptive Zoology.

The Weasels. — These are by some placed with the bears,
while others ally them to the cats. In this family are the
weasel, mink, ermine, marten, ferret, otter, badger, wolver-
ine, skunk. All are valuable for their fur. The weasel
turns white in winter. Most of these have strong scent
glands. Several of them are excellent swimmers and
divers, living largely on fish. One otter lives in the sea.

The Seals. — The seals are fitted for aquatic life by hav-
ing the hands and feet developed as paddles or " flippers,"
the limbs being very short. The sea lion can walk on all
fours ; others have the hind limbs permanently turned
backward, forming a sort of "tail fin," so that they swim
very much like the fishes, on which they feed. Seals are
sometimes said to be pinnigrade (walking by fins) in con-
trast to the digitigrades and plantigrades. No seals in-
habit the tropics. The seal grounds of the southern
hemisphere have been depleted by indiscriminate killing,
and the northern fields bid fair to meet the same fate.

The Primates. — This order, highest of all the mam-
mals, includes the monkeys, apes, and man. There is a
great range from the little squirrel-Hke marmoset to the
massive gorilla, and from the horizontal-bodied, four-footed
lemur to the erect biped, man. But structure is the basis
of classification, and many of these lower forms have
almost bone for bone and muscle for muscle similar to
those of man. The higher apes are tailless. The form
differs greatly, the facial angle of the ape being almost
that of a dog, while the Caucasian has an angle of about
95°. As we approach man in the scale the body becomes
more erect and is supported on the flat sole, instead of on
the outer edges as in the lower forms. Man alone has a
well-developed hand, and he distances all other forms in
having the power of speech, although some authors think

Mammalia.

283

Duodenum

apes have a language. The name orang-utan means " man
of the woods." Anatomists do not agree as to which is
nearer man, the chimpanzee or the gorilla. It must be
borne in mind that in the animal world classification is
based on structure, and that the zoological point of view
does not take into con-
sideration the intellectual, ^""''
moral, or spiritual quali- stomach
ties.

Characteristics of Mam-
mals.— (i) Mammals have
a hairy covering. (2) The
young are born alive.
(3) The young are nour-
ished by milk from mam-
mary glands. (4) There
is a diaphragm separating
the body cavity into
thorax and abdomen.
(5) All have teeth set in
sockets. (6) Two pairs of
limbs are usually present.

(7) There are usually
seven cervical vertebrae.

(8) The lower jaw articu-
lates directly with the
skull and not by the inter-
vention of a separate bone
(quadrate bone) as in birds. (9) There is an epiglottis
covering the opening (glottis) to the windpipe. (10) The
blood is warm, and of a nearly constant temperature.
(11) The heart is completely divided by a partition into
rio^ht and left halves.

Rectum

Fig. 166. Stomach and Intestines
OF Man.

284

Descriptive Zoology.

CLASSIFICATION OF MAMMALS.

SUBCLASSES. ORDERS.

Prototheria i. Monotremata— Duckbill and Spiny Ant-eater

{[^Nonplacentals) . 2. Marsupialia Opossum, Kangaroo

3. Edentata Sloth, Armadillo

4. Rodentia Rabbit, Squirrel

5. Insectivora Mole, Shrew

6. Cheiroptera Bat

7. Cetacea Whale, Porpoise

8. Sirenia Sea Cow

9. Ungulata Horse, Cow, Deer

10. Proboscidea Elephant

11. Carnivora Cat, Dog, Bear, Seal

12. Primates Lemur, Ape, Man

2. Theria

{Placentals) . -

CHARACTERISTICS OF CHORDATA.

1. There is a notochord, a long skeletal rod, a sort of
forerunner of the backbone.

2. There are gill slits opening from the throat to the
outside.

3. The central nervous system is a hollow tube and is
wholly dorsal to the digestive tube.

CHARACTERISTICS OF VERTEBRATA.

In the Vertebrata the characters given for the Chordata
are distinctly displayed, and a permanent backbone is de-
veloped. A cross section of a vertebrate shows two cavities
(see Fig. 150), the dorsal containing the cerebro-spinal
nervous system, and the ventral containing the digestive,
circulatory, and respiratory organs. In the vertebrates a
liver is always present. The nervous system is usually
well developed.

Classification of Animals. — An early classification divided
animals into two groups, the vertebrates, or the animals
having backbones ; and the invertebrates, those lacking a

Mammalia.

28j

backbone. A comparatively recent grouping is into Pro-
tozoa, or one-celled animals, and Metazoa, or many-celled
animals. Each of these groupings simply characterizes
one group (one system taking the lower end and the other
the higher end of the animal series) and lumps off all the
rest in one negatively named group. Neither of these sys-
tems pretends to do anything more than call attention to
the presence or absence of a single feature of structure.

Olfactory

lobe
Cerebrum

Mid brain

Sparrow

Diagram of Brains of Vertehrates.

From Kellogg's Zoology.

The Basis of Classification of Animals. — Thebasisdf classi-
fication of animals is structure, only so many branches being
recognized as there are distinct plans of structure. It is
generally understood that the structure considered is that of
the adult, since many animals change greatly during their
development. But in some cases, especially of degenerate
forms, the larval form shows, more clearly than the adult,
the true relationship. Consequently embryology must be
called in as an aid in classification. Fossils also clear up
many doubtful points in classification.

CHAPTER XVIII.
BRANCH PROTOZOA.

THE ONE-CELLED ANIMALS.

Amoeba. — The Proteus Animalcule. — One of the sim-
plest forms of animal Hfe is the Amoeba. It is found in
the slimy coating usually found on submerged leaves and
stems in standing water, or in the slimy ooze resting on
the mud at the bottom. If this ooze be examined under
a high power of a microscope, amoebae may usually be
found, though occasionally one has to search for some time

Endoplastn

Ectopls

Pseiidopods
extending

Pseudopods
retracting

Contractile vacuole

Water vacuoles

Food vacuoles

Fig. i68. Am^ba.

before he is successful. And it is difficult for a begin-
ner to be certain, at first, whether what he has found is
really an amoeba. An amoeba is a speck of clear, color-
less, jellylike substance called protoplasm, with a distinct,
though delicate, outline. There can usually be discerned a
clearer outer layer, the ectoplasm, and a more dotted cen-
tral portion, the endoplasm ; but there is no distinct line
between the two. Sometimes one can see a more dense

286

Protozoa. 287

appearing portion, the nucleus^ and occasionally there ap-
pears a clear space, the contractile vacuole.

If the object is an amoeba, it will usually soon betray
itself by its motion. First there is a bulging out on one
side, and this projection may be prolonged into a distinct
lobe, called a pseudopod. The amoeba may form several
of these pseudopods at the same time, so that it may have
little central body and nearly all of its substance may be
in the pseudopods. These pseudopods may be extended
and retracted without changing the place of the amoeba.
But more often after a pseudopod has been protruded, the
vest of the body follows it, seeming to flow into it; by

f^m .^ ;M, .assise, -^

Fig. 169. Amceba; Changes in Form, drawn at Short Intervals.

repetition of this process the amoeba changes its place,
and thus exhibits not only motion, but locomotiojt. If
watched for some time the amoeba may be seen to change
its shape considerably and to make slow progress, some-
times for a considerable time in the same direction.

Patient watching may reveal how the amoeba takes its
food. If a small plant or animal cell or portion of such
matter lies in its way, a pseudopod is pressed against it
and it becomes embedded in the endoplasm. With any
such food material there is usually taken a small amount
of water. The space occupied by the water and absorbed
food is called a food vacuole. Usually a number of these
food vacuoles may be seen in an amoeba. After a time the
water and other matter disappear, having been digested
and absorbed and assimilated into the substance of the

288 Descriptive Zoology.

amoeba. Occasionally a grain of sand, or other indiges-
tible matter, is taken in ; in this case it is finally passed
out of the body, usually being left behind as the amoeba
moves on. There is no mouth ; food may be taken in at
any part of the surface. There is no stomach ; the space
occupied by the ingested food is an improvised stomach.
There is no anus, residual matter being passed out at the
point most convenient. Still, as the amoeba moves about
in search of food, the surface that happens to be foremost
is likely to take in the new matter, and the part that is,
for the time, rearmost serves as the place of exit. The
amoeba may be said to flow around its food, and to flow
away from, and so leave behind, its waste matter.*

The work of moving about involves the expenditure of
energy. This energy is produced by the oxidation of the
substance constituting the amoeba. Oxygen is constantly
being absorbed through the surface to supply this need,
which varies according to the degree of activity. The oxi-
dation of the matter of the body of the amoeba produces
carbon dioxid and water, which are passed off, invisibly,
through the surface. The new food taken replaces the loss
by such oxidation. This taking in of oxygen and giving
out carbon dioxid is respiration, in its simplest form. In
the oxidation heat is produced, which probably is given
off to the water about as fast as it is produced in excess
of the temperature of the surrounding medium. Actively
moving amoebae warm the water in which they move, as
truly as we warm the water in which we are bathing,
or the air in which we are performing active muscular
work. And as we taint the air with our waste products
and need a constant renewal of the surrounding air, so
the amoeba must not be confined too closely in a limited
quantity of water that is sealed from the air.

Protozoa. 289

The amoeba shows that it has a sense of touch, for it
frequently avoids solid objects with which it comes into
contact, passing to one side. It has the characteristic
termed irritability. This characteristic does not involve
any special degree of sensitiveness, but simply the power
to receive impressions through contact with external objects.
If stimulated by slight electric shocks, the amoeba may
be made to withdraw its pseudopods and remain quiet
in a spherical form. It is said to have contracted, and
is said to be endowed with the property of contractility,
but it is simpler merely to say that it has changed
its form.

But the amoeba does not always wait to be stimu-
lated from without to make it move. It sometimes
appears to move " of its own accord," as we say. That
is, it is automatic, in the sense of self-moving.

^/T^v^x

O 1

i"IG. 170. AMCEBA DFVIDING.

If amoebae are well nourished, they are likely to mul-
tiply. They do this by simple division. An amoeba
becomes constricted in the middle. The constriction
increases until the individual is divided into two.

Encysted Amoeba. — Sometimes an amoeba, when sub-
jected to drouth, or perhaps other unfavorable conditions,
forms a tough outer wall, and remains in a quiet condi-
tion. The tough covering is called a "cyst," and the
amoeba is said to be "encysted." It may thus remain

290 Descriptive Zoology.

dormant for a long time, until more favorable conditions
return, when it ruptures the cyst, crawls out, and once
more renews its former active life.

SUMMARY OF THE CHARACTERISTICS OF AMCEBA.

1. It eats ; it takes in material through its surface from
the surrounding water

2. It digests ; the material thus taken in is made soluble
so that it can be used in building up the body of the amoeba.

3. \\. assimilates ; after suitable preparation the mate-
rial is taken into the actual substance of the amoeba ; it is
"made like," as the word "assimilate" signifies.

4. It grows, as a result of assimilation. Growth is the
increase in size and substance of a living thing as a result
of taking material from the outside and making it over
into its own body. Growth should be distinguished from
the mere increase in size of such dead objects as an icicle
or a crystal by the accretion of more material on the
outside.

5. \\. moves ; it has power, not to change its bulk, but
to change its shape. It is able to rearrange its particles,
which is what is meant by the term ** contract." Contrac-
tility does not mean ability to occupy less space. Distinc-
tion must be made between "motion" and "locomotion";
when an amoeba extends a pseudopod and then withdraws
it, this is motion ; when an amoeba changes its place, or
moves on, this is not only motion, but also locomotion.

6. It breathes ; the energy of motion is maintained by
a process of oxidation going on within the substance of
the amoeba. Oxygen is absorbed through the outer surface
and unites with the materials of the body of the amoeba.
Its energy is furnished by this oxidation as truly as the

Protozoa. 291

energy by which a train is moved is furnished by the
burning (oxidation) of coal in the engine.

7. It produces heat ; heat is another form of energy
which always results from oxidation. We are always pro-
ducing some heat, even when we are as quiet as possible,
and we know that when we are more active we breathe
faster and produce more heat. So with the amoeba. But
the amoeba should be classed with the so-called " cold-
blooded " animals. It should be noted that not only do all
such animals have a rather low temperature, but it is a
variable temperature and usually only slightly above the
temperature of the surrounding air or water. The amoeba
is constantly producing heat, but gives it off to the water
about as fast as it is made.

8. It gives off waste matter^ i.e. it excretes. All oxidation
produces waste matter. Oxidation of wood or coal pro-
duces carbon dioxid, water, and ashes. Our breathing
produces carbon dioxid, water, and other wastes which
we throw off continually. The carbon dioxid, water, and
other wastes thrown off by the amoeba are small in amount,
and, being invisible, pass out into the water unnoticed.

9. It feels ; when a foreign body comes into contact
with an amoeba it usually moves. A slight electric shock
causes it to assume the spherical form. There is good
evidence that amoebae have the sense of touch. They also
seem responsive to light and heat.

10. It reproduces its kind ; this we have seen is done in
the simplest way imaginable ; that is, merely by separating
into two parts, each of which is then a complete individual.
Multiplication takes place by division.

Paramecium, the Slipper Animalcule. — The slipper ani-
malcule is usually to be found in the water collected for
amoebae. In aquariums where clams have been kept,

292

Descriptive Zoology.

or in vases where flowers have been standing for some
time, a film of scum is likely to appear. Just underneath
this film is a good place to look. Often the naked eye
may detect small white objects moving about. These are
paramecia. On examining some of the water with a low
power of the microscope, one discovers that these tiny
white specks are oval or elliptical, that they swim actively,

Cbuise of food vacuoles Contractile vacuole

Cbotiactile vacuole —' ^M^-^y/^^^-..^

Ventral view.

ANTERIOR mAcRO- MICRO- MOOtH
END NUCLEUS NUCLEUS

.:^^£i^V{^;;3S=^^^^ ^ ;;

Oial groove

Side view

Mouth gullet Foo-i ball

Fia 171. Paramecium, the Slipper Animalcule.

usually with the same end foremost, and that when they
run against an obstruction they back off quickly. Thev
evidently have the power of mo\'ing and the sense of
touch. Looked at with a higher power, the shape may be
determined more definitely. They are somewhat flattened,
and one end is more pointed than the other. The dif-
ference between the clear ectoplasm and the more
granular eodoplasm is more marked than in the amoeba

FrotazosL 7.g3

There is also a rather distinct hijer, or cutick; f omung
the outer htycr of the ectoplasm. The wlx^ surface
is covered with small, haiilike prc^ectioiis called cilia.
These are prolongations of the protoplasm whidi makes
the hody of the paiamednm. These have the power of
activety lashing back and forth, acting like so maiijr pad-
dles^ by means of which the paiameciam swim&. At the
more pointed end, nsoalfy kept in the rear, there is a
bunch of longo- cilia, which seem to serre as a roddo-.
Sometimes the animal reverses its direction and proceeds
with the pointed end f oronost, bot ordinaiity onl^ for a
short time, to back oat cxf a tight place and to get a new
start in another directimu

How Banunednm Eats. — Along tiie flat smface is a
groove, which at one end forms a blind passageway d^
inng into tbc body. Both the groove and the tnb^ winch

is a gulet, are lined by cHia. By thdir vibrations these
cilia collect small one^elled plants and aniinal% or other
particles of organic matter, whic^ accnmnlate at the inner
end of the gullet FnHn time to time this inner end is
cut off by constriction, and a coHectioii of food paitidesy
with some water, is pushed into the soft protoplasm of
the body. It then is what is termed a food ball, or some-
times the space with its contents is des^nated a food
vacude. These food vacuoles maiy be r^^aided as so
many improvised stmnadis. The masses dowfy folate
around in the bo^ in the maimer indicated by the aiiows
in die accompanying figure. At a point about opposite
dieir starting^Kiint any undigested leaidne is expelled
through a weak place in the wall, theie being no permanent
anal opening.

ExcietiBU in P^an -:•:•:- — "^r- i.-- •: ^j^."";.- -;;; % dear
spaces in a par^-mec:: _::."-, ..:.- r.-..-^: t.}^:':. tzi. 1 :..-::. ^ may

294 Descriptive Zoology.

be seen to contract at tolerably frequent intervals, appar-
ently discharging liquid to the exterior. Around each of
these '' contractile vacuoles " is a series of radiating canals.
After the vacuole has become obliterated by emptying its
contents, it is gradually filled again by these surrounding
canals, which get watery material from the various parts
of the body. Thus certain waste material is thrown out.
The Nucleus. — Paramecium has two nuclei, a larger
body called the macronucleus and a smaller called the
micronucleus.

How Paramecium protects Itself. — In the outer part,
or cortex, are many small sacs, each containing a tiny
thread. When a paramecium is irritated, it discharges
these thread-cells, which appear to produce a stinging or
benumbing effect on small animals.

Multiplication of Paramecia. — Like the amoeba and
the vorticella, the paramecium forms new individuals by
division. The constriction is transverse, at about the
middle, and finally separates the one into two. Both the
macronucleus and the micronucleus divide, a part going
with each half, which soon after separating becomes a
complete paramecium.

Vorticcila, the Bell Animalcule. — Another interesting
protozoan is Vorticella or the bell animalcule. It is
found on submerged stems and leaves in stagnant water,
sometimes appearing Hke a delicate white fringe. Under
a low power of the microscope a vorticella is seen to be
bell-shaped, attached by a slender, flexible stalk, which
Joins the handle end of the bell-shaped body to some solid
object. When the animalcule is disturbed, the stalk be-
comes coiled, jerking the body up close to its support,
where it is much more secure than when extended.

Protozoa.

295

Examination with a higher power shows more of the
structure of the body. The bell-shaped body is not hol-
low, but is made up of protoplasm. Across the mouth of
the bell is a disk, which is slightly narrower than the
mouth of the bell. Between the disk and the rim of the
bell is a circular groove. At one point the groove dips
down into the body of the bell, forming a mouth and a
gullet. The borders of the disk and the bell are fringed

Groove

Gullet
Contractile vacuole

— - Macronucleus
— Micronucleus

tile axis

Fig. 172. VORTICELLA, THE BELL ANIMALCULE.

with cilia, which by their vibrations create water currents
and 'thus accumulate food material in the inner end of
the gullet. The food material consists largely of minute
plants and animals or fragments of larger forms. As in
the Paramecium, the collection of food particles becomes
pushed farther into the body, becoming a food ball, or food
vacuole, which, with others preceding and following, rotate
around the body in regular order. At the outer end of
the gullet is a space called the vestibule. Into this any
undigested residue is passed, and thus swept out by the

296 Descriptive Zoology.

currents maintained by the cilia. There is also a con-
tractile vacuole, which is near the vestibule and empties
into it. The vorticella has a C-shaped nucleus.

How Vorticella protects Itself. — When a vorticella is
disturbed it is at once jerked up close to its mooring
by the coiling of its stalk. At the same time the body
changes its shape. The disk is drawn in, the rim of the
bell turns in, the cilia are inclosed, and the body becomes
pear-shaped or even spherical, there being no opening left
at the free end. After the disturbance has ceased, the
stalk elongates, the bell opens, the disk protrudes, the
cilia extend, and the operations of active Hfe are all
resumed.

Development of Vorticella. — Vorticella multiplies by
longitudinal division. For some time two bells are attached
to the stalk, but one finally breaks loose and swims away
by means of its cilia. Later it becomes attached and
develops a stalk.

GENERAL CHARACTERISTICS OF PROTOZOA.

1. The protozoans are the simplest animals. Most of
them are one-celled. As a group, they are the smallest
of animals.

2. They are the 7nost numerous, in individuals, of any
branch of animals. It is not true, as commonly believed,
that every drop of water swarms with animal life. One
would find few animalcules in ordinary well or spring
water. But they usually abound in stagnant water. There
is room for vast numbers of these lowly forms which
occupy so little space.

3. They multiply the most rapidly of all animals. In
most cases multiplication consists simply of division into

Protozoa. 297

two equal parts, each of which is very soon a complete
individual, ready again to divide in the same manner.
Their great number is due to their rapid multiplication,
to their small size, which makes it easy for them to find
hiding places, and, further, to their complete adaptation
to the conditions in which they live. MultipHcation does
not depend wholly on division. There is occasionally
what is called " cojoiugation " ; that is, two individuals
come together and more or less completely fuse. At any
rate, it seems to be proved that the species could not con-
tinue to live indefinitely without the occasional occurrence
of conjugation. And this is supposed to be true of most
of the Protozoa.

4. They are the oldest of animals; that is, they are
supposed to have been on the earth longer than any other
kind of animals. We find their remains in very early
geologic formations. Some of them are supposed to have
changed but little as time passed, the conditions of their
surroundings being comparatively stable, while other
groups of animals have been greatly modified by changes
in their surroundings.

5. They are the most independent of animals. The
conditions of their lives are such that they could live with-
out the larger animals, while many of the latter could not
live without them.

Kinds of Protozoans. — There are many kinds of pro-
tozoans, some of them widely different from any of the
three forms we have studied. Some are parasitic. One
of the parasitic forms causes malaria when introduced into
the blood by the proboscis of a mosquito. Some proto-
zoans, instead of having cilia, possess a few longer vibratile
projections called flagella. In the one-celled forms there
is usually one flagellum, or, at most, two. But the colonial

29^ Descriptive Zoology.

protozoans are composed of several or many cells, each of
which may have a pair of flagella. Thus there are three
principal modes of locomotion among protozoans : (i) slow-
creeping by means of pseudopods, as in amoeba ; (2) swim-
ming by cilia, as in paramecium ; (3) more active swimming
by flagella, this mode being not very unlike the second.

The Sheil-bearing Protozoans. — Many protozoans have
shells. Some of these shells are composed of lime, others
of silica, while still others are formed of grains of sand
which the protozoan glues together by a secretion from its
protoplasm. Most of these shelled forms live in the ocean.
Some of the shells are borne where we should expect them,

on the outside, the animal being
able to withdraw into the shell
and project again at will through
an opening. But in many the ani-
mal cannot thus withdraw itself
completely into the shell. Many
of the shells are perforated by nu-

FlG. 173. NOCTILUCA. . . , -

. , , . . , merous mmute opemngs, through

A phosphorescent marine protozoan. ^ o ' ^

which fine threads of protoplasm
are extended, these projecting threads sometimes forming
a network outside of the shell. In many forms the proto-
plasm increases in amount, flows out of the main opening
of the shell, and forms a new shell, larger than the old one,
but attached to it. In this way it proceeds, making a series
spirally arranged, similar in general appearance to a spirally
coiled snail shell, or the chambered nautilus.

Chalk. — One of the most abundant and best known of
geologic formations is made by protozoans. Chalk is
made up of the shells, such as above described, of a kind
of protozoan known as Globigerina. Myriads of these
protozoans live in the ocean. When they die, their skele-

Protozoa. 299

tons slowly settle to the bottom. Dredgings from the
bottom of the Atlantic Ocean contain a gray mud which,
under the microscope, is found to be largely composed of
these shells. So where we find chalk rock on land, we
know that region was once the bed of the ocean. This
once soft mud has become hardened, by drying or by
pressure, sometimes by both, into hard rock, a variety of
limestone known as chalk. A generation ago the car-

Fig. 174. A Shell-bearinCx Protozoan (Globigerina).

From Packard.

penter and the schoolboy used a rough broken lump of
the chalk rock. The ordinary school crayon, however,
usually contains no chalk. Any one who has used the
old lump chalk will recall that occasionally he struck a
hard, flinty place, due to the mixture of other material.

Silicious Earth. — Other kinds of protozoans form their
shells of silica. Beds of this material are found in various
parts of the world and are used as polishing material,
under the names Tripoli, Barbadoes earth, etc. Many of
the shells of silica are exceedingly beautiful in form.

300 Descriptive Zoology.

Distribution of Protozoa. — All protozoans are aquatic,
though some might seem to be exceptions, living as they
do in damp moss ; but they are probably in thin films of
water on the surface. Protozoans are the most widely
distributed of animals, occurring almost all over the globe,
in fresh water and in the ocean, in lakes and rivers, ponds
and creeks, pools and ditches. In the ocean they are
more abundant in shallow water, but are also found at
considerable depths and at the surface of the deeper seas.

The Importance of Protozoa. — Protozoans are highly
important in two respects: (i) they have contributed
much to rock-making, and are still making deposits on the
ocean bottom ; (2) as a source of food to the animals of
the ocean, it is difficult to overestimate their importance.
In countless myriads they serve as food for animals some-
what larger and higher in the scale than themselves.
These animals, in turn, are the food for still higher animals.
The protozoans, then (with the protophytes or one-celled
plants), may truly be said to be the food foundation of all
the higher marine animals.

PROTOZOA AND METAZOA.

Protoplasm. — Protoplasm is the living substance of
animals and plants. It is a clear, jellylike substance,
which does not dissolve in water nor readily mix with it.
When seen in water its outlines are usually quite distinct.
It may appear more or less dotted on account of various
kinds of matter suspended in it. An amoeba is a mass
of protoplasm, and the properties of protoplasm were con-
sidered in connection with amoeba. Protoplasm has the
power of movement, is capable of being stimulated, i.e. is
irritable, it eats, grows, breathes, throws off waste matter,
or excretes^ and has the power of reproduction.

Protozoa. 301

Protoplasm is killed by very high temperature, killed or
its activity checked by low temperature, and, in general,
requires the conditions that we usually recognize as neces-
sary for life.

In its chemical composition protoplasm is exceedingly
complex. Protoplasm is a living substance, and any
attempt to analyze it kills it ; hence its exact composition
cannot be known. But the dead material left when it has
been killed can be analyzed, and consists largely of a sub-
stance called proteid. This consists of carbon, hydrogen,
oxygen, and nitrogen, with some sulphur, traces of iron,
and compounds of phosphorus, potassium, calcium, and
magnesium. Protoplasm seems to be a very unstable
compound, as we should naturally expect from its com-
plexity. Then, too, in its life and growth, it is constantly
changing, and, undoubtedly, changes more or less in its
composition from time to time.

The Cell. — Sometimes protoplasm occurs in a consider-
able mass, without any separation into distinct parts. But
usually it is found in more or less distinct particles, and
these distinct particles of protoplasm are called " cells."
There may be a cell wall distinct from the mass of proto-
plasm, but this is not essential to a cell. Within the cell is
a more dense appearing portion called the "nucleus." A
cell living independently tends to be spherical, though since
it has the power of changing its shape, it often departs
from the typical form. When an amoeba goes into the
resting stage it assumes the spherical form.

Protozoa and Metazoa. — The protozoans are typically
one-celled animals. The other animals are many-celled
and are called metazoans. Their greater size is not due
to their having larger cells, but to the increased number
of cells.

302 Descriptive Zoology,

Development of Metazoa. — Every metazoan begins life
as a single cell (except in multiplication by budding). It
starts as an Qgg (ovum or egg cell), having very much
the same characteristics as an amoeba. After being fer-
tilized it soon divides into two parts, but these halves,
instead of separating, as in the case of the amoeba, re-
main together. These halves divide into quarters, and
so on, into 8, i6, 32, 64, 128, etc., parts, until they become
too numerous to be counted. After a time these numer-
ous cells, still remaining together, arrange themselves in
the shape of the animal that produced the Qgg cell.

Division of Labor in Communities. — A solitary back-
woodsman has to do everything for himself. He gets and
prepares his own food, provides needed shelter, makes his
own clothing. But if he has a partner, there is sure to be
some division of their labor. One can do some things
better than the other, and they find that it is advantageous
for each to do what he can do best. In an Indian family
the men do the hunting and fighting, while the squaws pre-
pare the food, dress the hides for clothing and lodges, etc.
It is hardly necessary to call attention to the saving of time
that results from such a division of labor, or to note the finer
quahty and finish of the various articles of common use
when they are made by one who acquires skill by the con-
stant practice which comes from devoting himself entirely to
one kind of work. It is evident that no one man can do many
things and do them all as well as when the work is divided.

Physiological Division of Labor. — An amoeba does every-
thing for itself. Of course it lives very well in its simple
way, and is well adapted to its mode and place of life.
But it does too many things to do any of them very well.
It can move but slowly, it is dull of sensation, etc. Sup-
pose that, when an amoeba divides, the two parts remain

Protozoa. 303

adhering to each other, and that it divides again, making
four parts, and each of these divides, making eight parts
remaining in one mass. It is easy to see how one might
attend to the moving, another to the work of feeling, a
third to eating and digesting, a fourth to breathing, a fifth
to the work of dividing for the spread of the species, while
the other three became more or less flattened and spread
out over the others to protect them. This will serve to
give an idea of what actually takes place when the Qgg
cell of a metazoan has, by division, become a many-celled
mass. Each cell has primarily all the characteristics
common to an amoeba, — that is, they all have power to
move, eat, digest, feel, breathe, divide. But such a large
mass would be unwieldy unless it had some support ;
hence some cells may, to the advantage of the whole,
become harder and stronger to hold the soft cells in place.
In this now heavier mass there is more danger of mechani-
cal injury to the outside, and the outside layer by harden-
ing will serve to protect the inner, more delicate cells from
harm. If the outside cells harden, the animal will no
longer be able so well to absorb oxygen for the interior
cells, nor can it now take in food at any point. Special
arrangement must be made to take oxygen and food into
the interior, where soft cells can do the work of preparing
it for use in the body. These inner cells have now more
work than before, for they must prepare the material for
building and maintaining the cells that have given up their
power of digesting that they might fit themselves for pro-
tection. In proportion as any given cell devotes itself to
one kind of work, it must lose more or less the ability to do
the other kinds of work that it primarily could do. This
is what is meant by physiological division of labor. All
the cells resulting from the division of a metazoan egg

304 Descriptive Zoology.

cell are at first essentially alike in structure and function.
To fit themselves for the different kinds of work that they
have to do, they grow different. This growing different
is called differentiation. Each becomes fitted for one
special work ; this is specialization.

Tissues. — In the higher metazoans there are many
cells devoted to each of the different kinds of work to be
done. This we should naturally expect, for in such a
body there are myriads of cells, but only comparatively
few kinds of work. As has already been made clear, an
amoeba can do nearly all the kinds of work that any
animal can do, though in a much simpler way. The func-
tions of animals are summed up in saying they move, feel,
eat, grow, breathe, protect themselves, and reproduce their
kind. Stated more formally, the functions of animals are
included in the processes of motion, sensation, support, pro-
tection, reproduction, and mit}itio7t (nutrition including
digestion, absorption, circulation, 7'espiration, and excretion).

For instance, muscle cells are cells devoted to the work
of motion ; they have largely given up the other functions
that they originally possessed. The nerves have lost the
ability to change their form, in devoting themselves to
the special work of sensation. So, too, with the cells
of the supporting and protective tissues.

A tissue is a group of cells having the same structure
and function.

An amoeba consists of a single cell, but it can do a
number of kinds of work. A tissue consists of many cells,
but they all do the same kind of work. In other words,
an amoeba is simple in structure, but complex in function ;
a tissue is complex in structure, but simple in function.

Organs. — In addition to the differentiation of cells into
tissues, there is a still further division of labor by having

Protozoa. 305

certain distinct parts of the body devoted to a special
work; for instance, the hand is adapted to the work of
grasping ; it is an organ and its special work, or function^
is prehension. But the hand is composed of several kinds
of tissues. It is supported by bony tissue, the muscular
tissue gives motion to the fingers, the nerves are composed
of nervous tissue, connective tissue makes up the tendons
and part of the muscle, and the skin is another kind of
tissue. In addition there is usually some fat, which is
considered a still different tissue. The higher animals are
organisms^ — that is, they are made up of organs, each of
which has its special function to perform. In other words,
each organ works for every other organ in the organism,
and every other organ works for it.

The Colonial Protozoa. — This name is given to the
protozoans that have more than one cell, some of them
being actually many-celled. The simplest of these proto-
zoans are little more than an aggregation of cells, each of
which leads a nearly independent life, doing its own diges-
tion, etc. There is almost no division of labor among
them. Others form a true colony, and there is a rather
gradual series in development until in the higher forms
there is a division of labor approaching that found in the
simpler Metazoa. The cells in the simpler colonial proto-
zoans lead lives so nearly independent of their associates
that we might imagine the colony falling to pieces and
each cell again taking up an independent life, like that
of the amoeba. Not so, however, with the metazoans.
After their differentiation in structure and specialization
in function they are so modified that they could no longer
live independently. In developing one function each cell
has neglected other functions till now it is no longer able
to perform them. In other words, it has become dependent.

3o6 Descriptive Zoology.

Each cell lives and works, not merely for itself, but for
all. In their cooperation these units of a lower order have
become so united as to form ** a unit of a higher order," as
the mathematician expresses it.

The cell is the unit of structure in animals, and where
the cells unite and specialize they form a many-celled in-
dividual, in the strict sense of the word, — that is, it can-
not now be divided without destroying the life of the whole
complex individual.

There is one exception : the ^^g cells can, and do, live
separately. This is their work, to separate from the body
as a whole, for the express purpose of growing into new
individuals.

CHAPTER XIX.

BRANCH PORIFERA.

THE SPONGES.

The Simplest Sponge. — The simplest sponge is a vase-
shaped body attached by the base. It is hollow, and has
an opening (osculum) at the free end. Through the wall
are many small holes, and water is constantly entering
these holes (inhalant pores) and passing out of the
mouth of the vase. The cause of
this current is the vibration of many
flagella, which project inward from
the cells lining the cavity. This
current of water brings oxygen and
food, consisting of minute plants
and animals, and remains of larger
animals and plants. The vaselike
body is supported by a large number
of three-rayed spicules, embedded
in the wall of the vase. These are
composed of carbonate of lime, and
they constitute the skeleton, making
the body fairly firm, and yet leaving
it flexible and elastic. An outer layer of cells constitutes
the ectoderm, the lining cells are the endoderm, while
between these is a thin layer called* the mesoderm, in
which the spicules are embedded. (See Fig. 176.)

More Complex Sponge. — Somewhat higher is a sponge
that is vase-shaped, or cylindric, in which the inhalant

307

Fig. 175. Simple Sponge,
Marine.

Water enters minute holes in the
sides and passes out of the
opening at the top of the tube.

3o8

Descriptive Zoology.

pores do not lead directly into the main cavity (as shown in
Figs. 176 and 177), but do so indirectly. The cells bearing
the flagella, instead of lining the main cavity, are here in
the radiating canals that open into the main cavity, and

receive the water through cross
openings from the incurrent
canals. As in the simpler
sponge, there are supporting
spicules in the walls.

The Highest Sponges. —The
general plan of structure of the
highest sponges may be illus-
trated by Fig. 178. The most
noticeable pecuharities are two :
(i) The cilia are limited to cer-
tain cavities, or enlargements,
along the course of the passages
from the outside to the main
cavity. These cavities are called
the "ciliated chambers." (2) The
whole sponge is no longer a
vase or cylinder, but a mass, in
which the cavities are less con-
spicuous. This is due to the
increase of the middle layer, or
mesoderm, a gelatinous mass of
cells. As before, the outer layer
is the ectoderm, and the Hning
the endoderm.

Kinds of Skeletons. — Sponges
may be classed, according to the nature of their skeletons,
into three groups : —

I. Calcareous sponges, whose skeletons consist of

Fig. 176.

One of the Simplest Sponges,

Calcolynthus primigenius.

(After Haeckel.)

A part of the outer wall is cut away to

show the inside. — From Jordan and

Kellogg's Animal Life.

Porifera.

309

spicules of carbonate of lime, as seen in the simple sponge
described. These spicules have various forms, but the
three-rayed form is most common. They often resemble
crystals.

2. The silicious sponges, with spicules of siHca or
flint. These skeletons often appear to be made of spun
glass, and many of them are
of great beauty, one of the
most noted being the Venus's
flower basket, found about
the Philippine Islands.

3. The horny sponges, or
sponges of commerce. These
skeletons are composed of
a substance called spongiuy
whose chemical composition
resembles that of silk. Its
fine, threadlike fibers branch
and interweave, forming a
feltlike structure, with which
all are familiar. Its chief value consists in its absorbing
power, and this, in turn, depends on its softness, fineness,
and elasticity. Its durability is also a factor in its value.
Some sponges have both silicious spicules and horny fibers.

The Commercial Sponge at Home. — If one could "call
upon " one of these sponges, he would find it attached to
rock at the bottom of a warm sea. He would see a round-
ish mass with a smooth exterior, in color and finish not
unlike a dark-colored kid glove. He might see several
large openings, from which currents of water are emerg-
ing, bearing carbon dioxid and other impurities. Over the
surface he might discover smaller holes, into which the
water flows, bearing oxygen and food. If he were to dis-

Fig. 177. Cross Section of Simple
Tubular Sponge.

Showing (i) three-pointed spicules (skele-
ton), (2) cilia which bring in water through
(3) the holes in the sides of the tube.

3IO

Descriptive Zoology.

turb the sponge, these smaller openings would close, and
perhaps the larger ones also. If he now tried to pick it
up, it would be found firmly attached. Effort to detach
it by pulling would probably crush it, and show that the
whole has about the consistency of beef liver. It is easy
to squeeze out all of the soft tissue and leave the elastic
skeleton.

Source of Commercial Sponges. — The most valuable of the
sponges of commerce come from the Mediterranean ; many
also come from the Red Sea, Florida, and the West Indies,

Water
Exit

Water ^
Exit

Fig. 178. Diagram of a Commercial Sponge.

Collecting Sponges. — Sponges are collected by divers, oi
by the use of rakes, or by dragging hooks. They are piled
on shore to allow the soft tissues to decay, after which
they are washed, dried, sorted, trimmed, and shipped to
market. The finer ones are usually bleached. Sometimes,
in trimming away the base where they are attached to
the rock, enough is cut away to leave a large hole ; this
is the lower end of the cloaca, or main cavity.

Fresh-water Sponges. — Most of the sponges are marine,
but there is one family of sponges in fresh water. It is
not uncommon to find them in lakes and rivers, where they

Porifera. 311

form a coating on logs and rocks, usually greenish or
yellowish green. In still water they branch and may
reach considerable height, but in swift streams form a low,
spreading mat. They are of no commercial value. Some-
times in reservoirs supplying drinking water they give an
unpleasant taste to the water.

Relations of Sponges to Other Animals. — None of the
larger animals eat sponges. This may be due to the pres-
ence of the sharp spicules, or to an unpleasant taste or
odor. Many small animals bore into or crawl into them,
some for a safe hiding place, doing no direct injury to
their host. Others are perhaps parasitic. While no
sponge is a parasite, some injure shells, as oysters, by bor-
ing into them. Certain sponges are found only on the
shells inhabited by hermit crabs, where they pay for their
transportation by concealing their bearer.

Reproduction and Development of Sponges. — Sponges
have two ways of multiplying, — by budding and by eggs.

In budding, a group of cells, called a "gemmule," is
formed, which becomes detached, and develops into a
sponge. Fresh-water sponges form these gemmules in the
fall. The gemmules lie dormant over winter, and begin
growth in the spring.

Sponges produce eggs. These eggs are cells, which are
produced by the middle layer of the sponge (mesoderm).
Other cells, called sperm cells (or sperms), are produced
by some other part of the mesoderm, or perhaps by the
mesoderm of another sponge. After the egg cell is ferti-
Hzed by the sperm cell, it begins to divide, and forms a
number of cells which cohere. Part of these cells have
cilia, and by their vibration the embryo sponge swims
about, until finally it settles, attaches itself, and remains
fixed the rest of its life. While it is small and free, the

312 Descriptive Zoology.

vibration of cilia propels it through the water; after it
becomes attached, the vibration of cilia creates water
currents, which bring it food and oxygen.

Rank of Sponges. — The sponges are many-celled and
evidently higher than the colonial protozoans. But there
is no high degree of differentiation of parts. The cells
bearing flagella and the egg and sperm cells are differ-
ent from the others. But there are no special distinct
organs for the performance of special functions. In com-
paring them with other forms, it may be seen that they
are plainly the lowest of the metazoa.

CHAPTER XX.

BRANCH CCELENTERATA.

[This branch includes the Hydroids, Jellyfishes, Sea Anemones,
and Coral Polyps.]

Example. — The Fresh-water Polyp, Hydra.

Naked-eye Appearance of Hydra. — In examining a jar
of aquatic plants one may find attached to them slender
cylindric bodies about half an inch long and of the thick-
ness of a needle. Extending from the free end are several
fine, threadlike tentacles, which may be as long as the
body itself. Hydras are often white or colorless, but occa-
sionally brown or green ones are found. If undisturbed,
the body and tentacles may occa-
sionally sway gently to and fro.
If disturbed, a hydra usually
shortens until it is a tiny ball.
The tentacles also shorten until
they look like a circle of tiny buds.

Structure of Hydra. — Micro-
scopic examination is required to
learn much of the structure of hydra. The cylindric body
is hollow, and the hollow extends through the tentacles,
which are closed at their tips. Above the circle of
tentacles rises a cone-shaped body called the hypostome,
at the apex of which is the mouth. The body wall consists
of two layers, the outer being the ectoderm^ and the inner
the endoderm. Between these two is a layer called the
mesogloea.

3«3

Fig. 179. Hydra Extended.

3H

Descriptive Zoology,

The Ectoderm. — The cells of the ectoderm are clear, and
more uniform in size than those of the endoderm. At
their inner ends they are narrower, and usually end in
slender prolongations, which bend at a right angle to the
main axis of the cell, and help make a sort of middle layer
between the endoderm and ectoderm. These proloAga-

Tentacle

Spermary

Bud

Cross section

Fig. i8o. Hydra, Longitudinal Section.

tions are called muscle processes and are the chief agents
in shortening and moving the body. Between the nar-
rowed bases of the larger ectoderm cells are smaller cells,
which are supposed to be sensitive, and may perhaps be
properly called nerve cells.

Stinging Cells. — Among the cells of the ectoderm, both
of the body and of the tentacles, are peculiar bodies called

Coelenterata.

315

thread capsules, stinging cells, or nematocysts. These
are elliptical, and before being disturbed have a fine
thread coiled within. When the hydra is irritated, the
nematocysts are discharged and the threads are suddenly
darted out. At the base of each thread, close to the
capsule, are a few fine barbs, and it is supposed that a

Cell containing
thread capsule

Thread capsule
partly discharged

Thread capsule
fully discharged

Fig. 181. Stinging Cells of Hydra, highly Magnified.

poisonous substance is contained within the capsule. At
any rate, the result of coming in contact with this sort
of apparatus is a stinging sensation, like that caused by
nettles, but, of course, the hydra is so small that it does
not produce much effect except on very small animals.
But let a small crustacean, such as a water flea, swim
against a hydra's tentacle, and it is usually paralyzed at
once. Then the tentacles draw the victim to the mouth
and it is swallowed.

3i6 Descriptive Zoology.

The Endoderm. — The cells of the endoderm are larger
than those of the ectoderm. They are also less uniform
in size. They are darker colored, sometimes containing
brown coloring matter. The green hydra contains chloro-
phyll. The endoderm cells often exhibit amoeboid move-
ments, and frequently show food particles and large
contractile vacuoles, such as noticed in amoeba. Project-
ing from these cells into the cavity are sometimes found
large flagella.

Digestion in Hydra. — When food is taken into the central
cavity it is supposed to be partly digested here, this often
being called the digestive cavity. But, at any rate, parti-
cles not completely digested are taken into the endoderm
cells, where no doubt digestion takes place ; and from the
material digested by the endoderm cells the ectoderm gets
its nourishment. We here see a division of labor, the outer
layer producing the motion, obtaining the food, and pro-
tecting the whole, while the inner cells do the work of
digestion.

Locomotion. — While the hydra is pretty firmly attached
by means of a sticky substance secreted by the cells of the
base, it can let go and move away. It sometimes bends
over, attaches itself by the tentacles, and then lets go at
the base and pulls the base up close to the place where the
tentacles are fastened, and by repeating this action crawls
along like a ** measuring worm." Or it may bend over,
attach itself by the tentacles, let go at the base, and turn
the base clear over, thus turning a complete somersault,
though slowly, instead of with a spring. Sometimes, also, it
appears to crawl slowly by means of the tentacles alone.
But hydra is not a great traveler, preferring to wait for
something to turn up, rather than hunt for food. We see
how well fitted it is for a sedentary life, for with the long,

Coelenterata. 317

outstretched tentacles, with their many stinging cells, it
has a trap continually set for the unwary small swimmers
that abound in such places as the hydra inhabits.

Recovery after Mutilation. — One very remarkable fact
about hydra is its ability to live and grow after injury. If
cut into several pieces, each grows into a complete hydra.

Multiplication by Budding. — Hydra multiplies by bud-
ding. A small part of the wall bulges out and forms a
cylindric branch, with a double wall continued from the
two layers of the body, and the hollow of the branch is
continuous with that of the body (see Figs. 179 and 180).
After a while, a circle of tentacles is formed at the end of
the branch, and an opening appears at the end for a mouth.
Finally the base of the branch is constricted and the branch
separates and is an independent hydra.

Multiplication by Eggs. — Among the cells of the ecto-
derm, we noticed that certain cells are smaller and lie
deeper than the others. Some of these cells develop into
egg cells, or eggs. They are covered by the outer cells,
but make a marked bulging. This is the ovary (from ova,
eggs) and is usually found at about one third of the length
from the foot of the hydra (see Fig. 180). A somewhat
similar growth occurs near the tentacles, but the contained
cells are different. Instead of spherical cells like the egg
cells, here are produced cells resembling a miniature tad-
pole, with an oval head and a vibrating tail. These are
the sperm cells, or sperms, and the enlargement in which
they are developed is called a spermary,

CLASS I. — HYDROZOA.

Hydroids. — Most of the members of this class are called
hydroids, and, as the name impHes, they are hydralike.

.'?i8 Descriptive Zoology.

x3ut instead of being simple most of them are compound,
or, as it is more commonly expressed, they live in colonies.
We have seen that hydra multiplies by budding. Imagine
a hydra in which the budding continues indefinitely, the
new individuals remaining connected with the parent, ana

Fig. 182. A Hydroid.
After Allman. — From Kingsley's Zoology.

you have the hydroid colony. The relation between these
members of the colony is more than a mere mechanical
connection, for the internal cavity is continuous through the
colony, so that whatever one individual takes as food may
serve to nourish any one or all the other members of the
community.

Coelenterata. 319

The idea of community life is well carried out in that
there is a well-marked division of labor among the mem-
bers. Some, called nutritive individuals, devote themselves
to the work of obtaining and preparing food for the whole ;
some develop the stinging cells and protect the others ;
while still others are specialized for the work of reproduc-
tion, and depend on other members for nourishment and
protection.

General Appearance of Hydroids. — Most of the hydroids
are plantlike in appearance, hence are often called zoo-
phytes. Some resemble tufts of moss, others are simply
branched and trailing hke the ground pine. They vary
greatly in color, from white to dark brown, while some are
of a beautiful pink. A form that will serve well for
example is whitish or brownish, and forms a downy or
furry coating on the wooden piles of wharves, piers, etc.
Many threads creep along the surface, while others rise at
right angles to the surface and end in budlike swellings.
Examined more closely, these terminal enlargements are
found to be bell-shaped. These are the individuals borne
on the connecting and supporting stalks. The unit, or
zooid, as it is called, is very much like a hydra. The body
is hollow, with a circle of arms surrounding the mouth,
which is at the free end. It is unHke the hydra in at least
three respects. First, the base, instead of being closed,
opens into the supporting tube, and this is in communica-
tion with all the other zooids of the colony. Second, the
tentacles are solid instead of hollow; but they are like the
tentacles of the hydra in being flexible and provided with
stinging cells that serve for securing food. Third, the
mouth is distinctly raised above the bases of the tentacles,
and is capable of closing into a cone-shaped mass, the
hypostome, or opening into a bell-shaped entrance.

jao Descriptive Zoology.

A Tubularian Hydroid. — The general appearance of a
zooid of a tubularian hydroid may be seen from Fig. 182.
The body is hydralike, but with a prolonged mouth. There
are two layers of the body, the ectoderm and the endo-
derm. The ectoderm of the tentacles is provided with
nettle cells.

Structure of the Stem. — The structure of the common
stem is similar to that of the zooid. The outer covering of
chitin is called the perisarc, while the soft tube within, con-
sisting of ectoderm and endoderm, is called the cenosarc.
The endoderm cells have flagella.

Action of a Live Zooid. — The live zooid captures small
animals by stinging them as does the hydra. It uses the
tentacles to draw them into the mouth. After the food is
softened and reduced to a liquid, it is circulated by the
vibrations of the flagella of the cells of the endoderm. The
nettle cells serve for protection as well as in securing food.
When the zooid is disturbed, it withdraws into the protect-
ing cup, or hydrotheca, and may thus remain for some
time.

Development of a Zooid — Budding. — The colony in-
creases in extent by budding. A bud forms on the side
of a main stem. The bud consists of the same la}/ers as
the stem, namely, the perisarc and cenosarc. The bud
swells into a knob, the cavity of the main stem extending
into it, and the nutritive liquid circulates in the bud. After
a time the perisarc ruptures at the end and expands into
the cup, the cenosarc forms a mouth at the end, tentacles
develop around the mouth, and a new zooid is complete.

How a New Colony is formed — Medusa Buds. — By a

continuation of the process just described the colony is
increased in extent, but no new colony is formed; for none

Coelenterata. 321

of these parts separate from the colony. But certain buds
differ from the above. Usually near the base of the
colony are to be found longer buds which develop differ-
ently. They become long and club-shaped. The soft
cenosarc, blastostyle, develops circular side buds, called
medusa buds, which finally become detached and swim
away, passing out of a hole which is formed at the end of
the gonotheca, as the perisarc is here called.

Medusae. — The medusa bud when developed becomes
an umbrella-shaped body, and is called a medusa, or often
a hydromedusa. It is, in fact, a small kind of jellyfish.
The outside of the umbrella is called the exumbrella and
the inside the subumbrella. Hanging from the center of
the subumbrella surface is a short handle, the manubrium.
It is hollow, and the opening at its end is the mouth. The
cavity extends up through the handle, and continues as four
ladiating tubes to the margin of the umbrella. These
four radiating tubes, or canals, are connected by a circular
canal, running around near the margin. Food is taken in
at the mouth, digested, and circulated through this system
of canals. From the margin of the umbrella a short fold
or shelf extends inward horizontally, and is called the veil
(velum). Around the margin are numerous tentacles, and
on the margin certain spots supposed to be organs of a
sense of direction. Some medusae have around the mar-
gin of the umbrella a series of black spots, which are rudi-
mentary eyes. The umbrella has the power of expanding
and contracting, and by this means the medusa swims.
Sometimes it turns inside out.

How a Medusa Multiplies. — Suspended from the sub-
umbrella surface, close to the four radial canals, are four
spherical bodies. These are the gonads. In one indi-
vidual the gonads produce eggs (ova), and in another

322

Descriptive Zoology.

individual they produce sperms. The gonads set free
their contents in the water, and the eggs are fertilized by
the sperms. After fertilization, the egg develops first into
a simple hydralike polyp, and later, by budding, into a

branched hydroid like the form
that produced the medusa.

Alternation of Generations. —
Thus we see that these hydroids
have two forms, and neither one is
complete. The hydroid form can
spread as a colony, but it can form
no new colony. But by means of
the medusae, which are free-swim-
ming, it forms new colonies, which
may be at a distance from the
original colony. This peculiar
process of development, hydroids
giving off medusae, and medusae,
in turn, producing eggs which
develop into hydroids, is known
as "alternation of generations."
It is found in some other lower ani-
mals, and among the Arthropods.

Other Forms of Hydrozoa. — The
great majority of Hydrozoa have
an alternation of generations as
described. But there are others
in which there is only a medusa
form, no polyp form appearing,
the eggs produced by the medusa
developing directly into a medusa form. In others the
medusa buds are produced, but are not set free. While
remaining attached, they produce and set free the eggs

Fig. 183, Portuguese
Man-of-war.

Coelenterata. 323

and sperms, which develop into polyp form. The siphon-
ophores are in colonies, but, instead of being fixed, are
free. Some swim by means of bell-shaped zooids, resem-
bling a cluster of medusae, while other zooids in the group
devote themselves to nutrition, and others to the work of
protection. In other kinds of siphonophores there is a
bladderlike float, and locomotion depends upon the wind
and current. The Portuguese man-of-war is an example.
All forms are well provided with stinging cells, and one
who handles them carelessly finds that this whole branch
may well be designated "the sea nettles."

CLASS II. — THE SCYPHOZOA.

Jellyfishes. — This class is mostly made up of the larger
jellyfishes. One of the most common on the New Eng-
land coast is the common white jellyfish, known as Aurelia.
It is saucer-shaped and frequently is a foot or more in
diameter. It is gelatinous and semitransparent. In the
center of the subumbrella is a short stalk, or manubrium.
At the end of this is the square mouth, from the corners
of which extend four delicate processes, the oral arms.
The short gullet leads from the mouth to a roomy stomach,
whose four gastric pouches extend halfway to the margin.
There are many fine radiating canals and a small, circular
marginal canal. On the floor of each gastric pouch is a
brightly colored gonad, whose contents, eggs or sperms,
are discharged into the stomach and pass out through the
mouth. Along the inner border of each gonad is a row
of delicate gastric filaments, well supplied with stinging
cells, whose function is to paralyze the animals taken in as
food. The margin has a fine fringe of tentacles. Evenly
distributed on the margin are eight peculiar sense organs.

3^4

Descriptive Zoology.

Development of the Scyphozoa. — The egg, after being
fertilized, divides into many cells. These finally arrange
themselves into a two-layered sac. This becomes cylin-
drical and attaches itself by one end. The other end
opens to form a mouth, around which tentacles develop,

Fig. 184. Jellyfish.

The four long projections are the oral (mouth) appendages. The slender hanging
projections are the marginal tentacles.

thus forming a hydraHke or polyp form. This elongates
and becomes constricted transversely so that it resembles
a pile of saucers, each of which is scalloped. These
saucer-shaped parts become detached in order from the

CcElenterata. 325

top, each, except the first, forming a jellyfish. The sur-
face that was uppermost becomes the subumbrella.

Other Jellyfishes. — Most of the jelly fishes are essen-
tially similar to Aurelia, though they differ considerably in
their shape, some being conical instead of saucer-shaped.
They often are seen in great schools, swimming lazily by
gently opening and closing the umbrella, or floating at
the surface ; or they may sink out of sight at will. They
are mostly marine, and most are free-swimming, though a
few are permanently or temporarily attached by the exum-
brella surface. They are all carnivorous, feeding largely
on Crustacea. Most of them are very beautiful, being Hke
cut glass, or brightly colored, many being beautifully phos-
phorescent. The great blue jellyfish of the New England
coast sometimes is seven feet in diameter with tentacles
a hundred feet long. Smaller specimens of this sort, when
seen by transmitted Hght, as when in an aquarium,
resemble immense amethysts.

CLASS III. — ACTINOZOA.

Sea Anemones. — To this class belong the sea anemones
and most of the coral polyps. The common sea anemone
is hydrahke, that is, it is cylindric, attached by the base.
The tentacles are numerous and are borne on a disk sur-
rounding the mouth at the free end. The mouth is an
elongated slit. The internal structure differs considerably
from that of the hydra. In the first place, the mouth
does not open directly into a simple body cavity, but is
continued as a tubular gullet, which extends halfway down
the body. A series of radiating partitions run the whole
length of the body, extending from the outside of the
gullet to the body wall. Below the lower end of the

326

Descriptive Zoology.

gullet the free inner edges of these partitions, the mesen-
teries, may be seen.

Digestion in the Sea Anemone. — Small animals, such as
crustaceans, moUusks, and fishes, which come in contact
with the tentacles, are partially paralyzed. They are then
drawn into the mouth and passed through the gullet into
the digestive cavity below, which may perhaps be called

Fig. 185. Sea Anemone.

After Emerton. — From Kingsley's Zoology.

the stomach. On the edges of the mesenteries below the
gullet are many threadlike projections, called the mesen-
terial filaments. These filaments are richly provided with
nettle cells, which complete the killing of the prey. The
filaments are also furnished with gland cells, which supply
the liquid for digesting the food. The liquefied food ma-
terial may pass up into all the spaces between the mesen-

Coelenterata. 327

teries, or intermesenteric spaces, as they are called.
There are holes through the mesenteries near the top, so
these chambers may communicate with one another. Be-
tween the mesenteries are ridges, extending inward from
the outer wall, but not reaching the gullet. These are
incomplete or secondary mesenteries.

Change of Form of the Sea Anemone. — When undis-
turbed the animal is cylindrical, sometimes long, some-
times broad, so that many of them resemble the flowers of
the chrysanthemum, daisy, anemone, and sunflower. They
well deserve the name, for many of them are beautifully
colored. The tentacles are often banded with variegated
colors. It is hard for one who has lived all his life inland
to realize that such brilliantly colored, flowerlike forms are
actually animals and not plants. But disturb one of these
flowerlike animals and it shows its real nature. It at
once begins to shorten, to withdraw its tentacles, and
shrink into a rounded mass lying close to its attachment.
The mesenteries are well suppHed with longitudinal mus-
cles, whose shortening draws the body down close. Near
the margin of the disk are strong circular muscles which
shorten and shut in the free end, over the retracted ten-
tacles, like a bag with a draw-string, so that all that
appears resembles an old felt hat, with, perhaps, a little
indication of a hole at the apex. After the disturbance
ceases the sea anemone may gradually expand again.

Development of the Sea Anemone. — Sea anemones lay
eggs, which are developed in the mesenteries near their
free edges. The later development resembles that of the
jellyfishes, but there is no alternation of generations.

General Characteristics of Sea Anemones. — Sea anem-
ones are all marine. They are all single, that is, they
do not form colonies. They have no true skehton. Some

328 Descriptive Zoology.

sea anemones attach themselves to the shells inhabited by
hermit crabs. They thus get transportation, and are
more secure of getting food. In return they protect the
crab, for few animals care to eat so tough and nettling a^
animal as a sea anemone.

Coral Polyps. — The coral polyps are essentially like
the sea anemone in their structure. But, unlike the sea
anemones, they are almost always in colonies. They are
unlike the sea anemone, too, in secreting carbonate of Ume
at the base. The single coral makes a cup or circular

Fig. 186. A Cluster of New England Coral Polyps.

They secrete but little coral.

wall, with radiating partitions, these radiating partitions
alternating with the mesenteries. In the colonies these
individual cups fuse more or less together, making im-
mense masses of coral.

Kinds of Coral Polyps. — Coral polyps are usually
classed in two groups, according to the number of ten-
tacles. In the sea anemone the tentacles are some mul-
tiple of six. Some authors call these Hexacoralla. To
this group, besides the sea anemone, belong all the true
corals which produce coral reefs and islands. As is well

Coelenterata. 329

known, they cannot build coral in cold water, being
limited to about the temperature of 60° F. The other
group have the tentacles on the plan of eight, and are
sometimes therefore called Octocoralla. They make little
coral, but form whiplike and fanlike colonies, the sea

Fig. 187. Red Coral Polyps.

fans, and sea pens, or sea whips. These have a horny
core with loose limy material on the outside. To this
group belongs the well-known red coral of the Mediterra.
nean. The polyps of many of the corals are exceedingly
brilliant.

GENERAL CHARACTERISTICS OF CCELENTERATA.

1. There is no digestive tube separate from the bod}'
cavity.

2. Stinging cells are almost always present.

3. The body is usually radially symmetrical, but in some
there are traces of bilateral symmetry.

330 Descriptive Zoology.

4. In addition to producing eggs, many multiply by bud-
ding, which often results in (5),

5. Colonies, often showing marked division of labor
among the differentiated individuals, or zooids.

6. The body consists of three layers : an ectoderm, and
endoderm, and a middle, supporting layer, called the meso-
glea.

7. The coelenterates are mostly marine.

CLASSIFICATION OF CCELENTERATA.

Class I. Hydrozoa; examples, hydra and the hydroids-

Class 2. Scyphozoa ; examples, most of the large jelly*
fishes.

Class 3. Actinozoa ; examples, the sea anemones and
most stony corals.

Class 4. Ctenophora, the " comb jellies."

k

CHAPTER XXI.

BRANCH ECHINODERMATA.

The echinoderms include the starfishes, brittle stars,
sea urchins, sea lilies, feather stars, and sea cucumbers, all
exclusively marine.

CLASS I. — ASTEROIDEA.
Example. — The Common Starfish.

Occurrence. — The common starfish is found all along
the Atlantic coast from Labrador to Florida. It is more
abundant in the shallower water, especially on the oyster
beds. Other kinds of starfishes are found deeper.

General Appearance. — The common starfish is a five-
rayed star. The central body is called the disk and the
arms are the rays. In the center of the more flattened
surface is the mouth ; hence this surface is called the
"oral" surface in distinction from the opposite "aboral"
surface, which is more convex.

The Skeleton. — One of the noticeable features of the
starfish is its roughness. This is due to the limy skeleton,
which consists of many small pieces (ossicles) of calca-
reous material loosely and, in the main, irregularly joined
together by more or less muscular tissue, so that the star-
fish can turn or twist the rays about to a considerable ex-
tent. The skeleton is embedded in the tough body wall,
which is more or less ciliated, externally and internally.
Many of the ossicles bear rigid projecting spines, while on

331

33^

Descriptive Zoology.

the oral surface, especially along the borders of the
grooves on the oral surfaces of the rays, are movable
spines attached to the ossicles of the body wall.

On the aboral surface are many small pinchers, consist-
ing of a short stalk bearing two calcareous blades. The

Fig. i88. Common Starfish.

stalks are flexible, and the blades of the pinchers may be
seen opening and closing. It is thought they are for the
purpose of keeping the body clean by picking up and re-
moving small particles. These pinchers are called pedi-
cellariae.

The Water Tube System. — Before we can understand
how the starfish locomotes we must get an idea of the
water tube system, or water vascular system, as it is usually
called. In the first place, an examination of a live starfish
will show the rows of soft, flexible, cylindric tube feet in
the grooves in the rays. By watching the live animal it

Echlnodermata.

333

will be seen that these tube feet are retracted, extended,
and variously moved about. For protection the feet can
be withdrawn into the groove. But commonly the feet
are applied to the surface on which the starfish is creep-
ing. Each tube foot is a hollow cylinder, containing
water, and is connected by a slender tube, passing be-
tween the ossicles, with a water bulb in the cavity of the
ray. Both the foot and the bulb are muscular, so when
the bulb contracts it forces more water into the foot and

Madreporic
plate

Stone canal

Radial canal

Fig. 189. Water Tube System of Starfish.

extends it; and when the foot shortens it can send the
water back into the bulb. Around the mouth is a circular
water tube, which sends a tube along each ray ; and side
branches from these radiating tubes supply the tube feet.
On the outside of the aboral surface, between the bases of
two of the rays, there is a wartlike body. This is the
madreporic plate. It is perforated. Water enters it and

334 Descriptive Zoology.

passes down through a madreporic canal or stone canal
(made of the same material as the skeleton), and this
stone canal empties into the circular water tube around
the mouth. Thus water, filtered through the madreporic
plate, is supplied to the whole water tube system. There
is also a series of water bulbs opening into the circular
water ring ; these are the Polian vesicles.

How the Starfish Crawls. — When the starfish wishes to
crawl, it distends the tube feet by the action of the water
bulbs (or water sacs, called ampiillcB) along the inside of
the rays. The flattened disklike ends of the feet are
closely applied to the surface on which it is crawling. Then
the center of the disk is somewhat retracted, making a sort
of " sucker," by which the foot holds firmly. When many
feet are thus holding there is considerable power, and when
the feet are now shortened the body as a whole is pulled
along. The starfish can climb vertical walls or even cling
to the under side of a horizontal surface. And so strongly
can it hold that sometimes, when the collector tries to pull
it away he simply tears the starfish in two. The starfish
can crawl with any ray foremost.

The Digestive System of the Starfish. — The mouth opens
into a large stomach which fills nearly all the space in the
central body, and has, in addition, a large lobe extending a
short distance into each ray. The stomach is thin-walled
and very extensible. This wide part of the stomach is
called the cardiac portion. The stomach narrows above,
and again widens to form the pyloric portion. Into this
portion is poured the secretion of ten digestive glands, a
pair in each ray. The ducts of the two glands in each
ray unite, so there are five ducts entering the pyloric
stomach. These glands are Hke long bunches of small
grapes. The glands are held in place by thin folds of the

Echinodermata. 335

lining membrane of the ray, and are called mesenteries.
From the pyloric stomach a slender intestine extends up
to the aboral wall, a little to one side of the center. Its
opening is hard to find and in some starfishes is entirely
obliterated. There are no jaws nor any teeth in the
starfish.

The Starfish's Food and Mode of Eating. — Starfishes feed
chiefly on mollusks, especially on oysters and mussels.
The starfish arches the body over the oyster, and then
turns its stomach inside out and around the soft body of
the oyster, and, after digesting it, withdraws the stomach
again. This seems an odd way of eating, but certainly it
is an economical way, for the starfish takes only what it
can digest and absorb.

Damage done to Oysters. — The starfish is a very vora-
cious animal, and the injury done by it to the oyster indus-
try is very great. The oystermen have learned that they
must make effort to keep the oyster beds clear of starfishes.

How Starfishes recover after Mutilation. — A starfish
torn in two will grow, and may make two complete star-
fishes. The oystermen know that it will make a bad
matter worse to tear the plunderer into pieces and throw
them back into the water. Experiments show very great
power of recovery after mutilation. Frequently one finds
starfishes with one ray missing, or even two or three.
Occasionally the collector finds a specimen with but one
fully developed ray, the other four having been lost. Four
new rays may, perhaps, be started, which in course of time
will grow to full size.

The Body Cavity. — The starfish is a decided advance
on the coelenterate type of structure in having a distinct
body cavity, separate from the digestive tube.

336 Descriptive Zoology.

Circulation. — There is no well-developed circulatory
system, such as we find in the higher animals. There are
blood corpuscles in the Hquid contained in the general body
cavity. This liquid pervades all parts, and is set in motion
by the cilia of the lining membrane, and by the general
movements of the stomach and the bending of the rays ;
these movements seem to suffice to circulate the contained
liquid, which probably directly receives the absorbed prod-
ucts of digestion.

Respiration in Starfishes. — There is no very complete
system of respiration in starfishes. In fact, no such system
is needed, for the whole body, inside and out, is constantly
bathed in sea water. Still, it is thought by many authors
that the tube feet are the chief agents in absorbing oxygen
from the water and giving off the waste. There are also
many holes through the aboral wall, from which extend
slender projections of the thin, soft fining membrane of
the body cavity. These are now supposed to be gills.

The Nervous System and Senses. — The nervous system
is near the surface, and can be seen without dissection.
Around the mouth is a five-angled nerve ring, which gives
off a radial nerve along each ray. It may readily be seen
by separating the tube feet along the middle line.

At the extreme end of each ray is an eye spot, which
shows as a distinct red spot in a fresh specimen of the
common starfish. In alcohoHc specimens it is hard to see.

Close to the eye is what appears to be a tube foot, but
without the disk at the end. This is called a tentacle, and
is now believed to be an organ of smell. The sense of
smell seems to be a much better guide than sight in bring-
ing the starfish to its food. There is undoubtedly some
sensitiveness to touch, but of this and any other senses
little is known.

Echlnodermata.

337

Development of the Starfish. — The female has a pair of
ovaries at the base of each ray. They are like slender
bunches of tiny grapes. The eggs pass out of minute pores
in the angles between the bases of the rays. In the males
the spermaries occupy a similar position and resemble the
ovaries in form, but are lighter colored, usually white. The
young starfish goes through a remarkable transformation,
the young no more resembling
the adult than in the case of
many insects with which we
are famiUar. The most strik-
ing fact is that the young is
very distinctly bilaterally sym-
metrical, showing no traces of
radial symmetry.

Other Forms of Starfishes. —
Most starfishes are five-rayed,
but in some the rays are so
short that the whole animal is
a pentagon, the rays hardly

extending beyond the disk. Some are brilliant, exhibiting
beautifully complementary colors of purple and orange.
The number of rays may be as many as twenty. A Pacific
starfish sometimes becomes two feet in diameter.

Fig. 190.

Brittle Star; Sand
Star.

CLASS II. — OPHIUROIDEA.

The Brittle Stars. — The ophiuroids are represented by
the brittle stars. Their general form is similar to that
of the starfishes. But the central disk is more distinct and
the arms relatively slender. The arms are more flexible
and the brittle star locomotes by active lateral movements
of the arms, making rapid progress compared to a starfish.

^2^ Descriptive Zoology.

The arms are not hollow as in the starfish, there is no
ambulacral groove and the tube feet project on the side
instead of on the oral surface. On account of the taper-
ing arms, with their active wriggling movements, the
brittle stars are sometimes called serpent stars. They
are also called sand stars. In some ophiuroids the arms
are branched as in the common basket star, whose arms are
many times branched, and become so inroUed as to give
the name basket-fish.

CLASS III. — ECHINOIDEA.

Occurrence. — Sea urchins are found along the Atlantic
coast from low-water mark to fifty fathoms, being more
common among rocks. They are also found clinging to the
piles of wharves. The northern form is greenish, with
slender spines, somewhat resembling a chestnut bur. The
more southern form is of a dark color, with fewer and
stouter spines.

General Form of a Sea Urchin. — The common sea urchin
is apple-shaped, the mouth being where the stem of an
apple is, and the anus at the opposite end, or pole, as the
ends are termed. Running from the mouth to the anus are
meridians, marked especially by the five double rows of
tube feet, which, when fully extended, are long and slender,
reaching beyond the tips of the longest spines. For some
considerable space around the mouth is a leathery mem-
brane, the peristome, where the skeleton is undeveloped.

The Skeleton. — As in the starfish, the leathery body wall
abounds in limy plates, or ossicles ; but instead of being
loosely attached to each other, as in the starfish, they are,
in the sea urchin, firmly cemented together, constituting a
rigid shell. These shells are sometimes sold under the

Echinodermata.

339

name of sea eggs. In a cleaned shell, or corona, as it is
sometimes called, there are found ten double rows of cal-
careous plates, making twenty in all. Every alternate
double row is closely perforated for the passage of the
tube feet. These perforated plates are called the ambu-

FiG. 191. Sea Urchin.

The heavy projections are the spines; the long, slender ones are the tube feet.

lacral plates. Both the ambulacra! and the interambula-
cral plates bear rounded elevations, on which the spines
were borne. Each spine has a hollow in its base, which
hts over an elevation on the shell, making a ball-and-socket

340 Descriptive Zoology.

joint, and is capable of a limited motion in any direction
by means of muscles attached around the base. Between
the spines are the pincherlike pedicellariae, as in the star-
fish, only here they have three blades instead of two.

The Water Tube System. — The sea urchin has a water
tube or water vascular system essentially like that of the
starfish. There is a water ring around the gullet, with
radiating tubes between the rows of feet along the ambu-
lacral rows. Inside the shell are water bulbs, or ampullae,
as in the starfish, and the mechanism for the operation of
these parts is as described for the starfish.

How the Sea Urchin Locomotes. — The injected feet are
extended and attached by means of the suckerlike action
at the end of each foot. Then the muscular shortening of
the feet pulls the sea urchin along. This means of pro-
gression is also aided considerably by the movements of the
spines. The sea urchin can climb perpendicular surfaces.
When placed on the aboral surface, it can turn over, though
it is a very slow process. Sea urchins are sometimes found
in deep holes in rocks, and it is believed that they have
gradually made the holes.

Digestive System of the Sea Urchin. — Projecting from
the mouth are usu-ally to be seen five hard, white teeth.
These teeth are movable, not being set in sockets, but held
in a very complicated apparatus, somewhat like a five-angled
top, known as Aristotle's lantern. The whole apparatus is
under muscular control. Through the center of the whole
runs the gullet. Above the tooth apparatus the intestine
runs around the body wall, then reverses, making in all
about two and a half turns around the body wall. It then
extends up to the apex, where it ends in the anus, guarded
usually by four calcareous plates. It is held in place by
a thin membrane, the mesentery.

Echlnodermata. 341

The food is varied. Sea urchins sometimes eat sea
weeds. At other times they are found eating fish, etc.,
that have been thrown out as refuse by the fishermen.
Sea urchins are of no special economic importance, neither
being of any use nor doing any damage.

Respiration in the Sea Urchin. — Around the mouth, on
the leathery membrane known as the peristome, are some
specially modified tube feet which are supposed to act as
gills. But, as in the starfish, the whole body, inside and
outside, is so thoroughly bathed in water that there hardly
seems a need of any special organs of respiration.

The Nervous System of the Sea Urchin. — This, too, is
very similar to what we have seen in the starfish. There
is a nerve ring around the gullet, from which a radial nerve
passes along the ambulacral hne, between the rows of tube
feet, just within the body wall.

At the end of the series of ambulacral plates is a single
plate, known as the ocular plate, on which is an eye, at the
very tip of each radial nerve.

There are also, over the surface of the body, a number
of small spherical bodies, borne on movable stalks. These
bodies (spheridia) have ganglion cells in them, and are
regarded as sense organs.

Development of the Sea Urchin. — The ovaries are situ-
ated in the aboral part of the body cavity and are placed
in the interambulacral spaces. A duct from each ovary
opens through a plate at the end of the series of interam-
bulacral plates. These plates with the genital pores are
called the " genital plates," and alternate with the ocular
plates that have been described as occurring at the apex of
the series of ambulacral plates. In the male the sperma-
ries occupy a similar position, and have similar genital
pores. In the Southern sea urchin the ovaries are red

34^ Descriptive Zoology.

from the color of the contained eggs, while the spermaries
are white. The ovaries and spermaries are similar in form,
resembling small bunches of grapes ; and if it were not for
the difference in color, it would require microscopic exami-
nation to distinguish the two sexes. Both the eggs and
sperms are discharged into the water. The sperms are
microscopic, tadpole-Hke bodies, swimming actively by the
vibration of their tails. If the sperms do not gain access
to the eggs, the eggs do not develop, but soon die. But
usually the sperms surround the eggs, there being, ordi-
narily, many sperms to each egg. One sperm gains en-
trance to an egg, at least the head fusing with part of
the egg. The egg is now said to be fertilized.

After fertilization, the egg mass contracts, leaving a
clear space around it inside the outer coat, or cell wall.
Soon the egg mass within divides into two equal parts,
each of these halves again divides into two, the four then
become eight, sixteen, thirty-two, and so on until the num-
ber can no longer be counted and the egg looks like a
spherical mulberry. This process of division is known as
segmentation. The berrylike mass now becomes hollow,
consisting of a single layer of cells. Next one side is
pushed in like a rubber ball with one side punched in ;
it now has a wall made of two layers of cells. On the
outside are little hairlike projections of the cells, called
cilia, which by their vibrations propel the body through the
water. A set of needlelike rods develop within the
embryo, which soon make a skeleton, shaped somewhat
Hke a common chair. This skeleton has a covering of soft
tissue, and the projections, which correspond to the legs of
the chair, are covered with strong cilia for locomotion.
The digestive tube has at first but one opening, that made
by the doubling in of the outer wall, as above mentioned,

Echlnodermata.

343

and the cavity of this depression forms the digestive cavity.
The mouth is formed later by a new opening made through
the outer wail into the first cavity, and the original opening
becomes the anus. So far the young sea urchin is very
unHke the adult ; but after a time this larva begins to
transform into the real sea urchin, and soon the little sea
urchins, about the size of pins' heads, are found crawling
up the sides of the glass vessels in which they are kept. It
should be noted that the larval sea urchin is bilaterally
symmetrical, whereas the adult
is, apparently at least, radially
symmetrical.

Other Forms of Echinoids. —

In addition to the common
apple-shaped sea urchins, we
find very greatly flattened
forms, such as the sand cake,
or sand dollar, also called cake
urchin. The mouth is central,
but the anus is at one edge.
Slightly different is the key-
hole urchin, with narrow open-
ings through the shell (not
communicating with the body cavity). There are some elon-
gated urchins, showing rather marked bilateral symmetry.

'-■-•'""^•t..\Kp.';-j

Fig. 192. Sand Dollar; Cake
Urchin.

The spines are removed from most of
the surface.

CLASS IV. — HOLOTHUROIDEA.

Sea Cucumbers. — Our larger holothurians are cucumber-
shaped, hence the common name, sea cucumber. The
mouth is at one end and the anus at the other. Around
the mouth is a circle of tentacles, with which food is
taken. Along the sides, usually in five distinct rows, are

344

Descriptive Zoology.

the tube feet. Sometimes the radial symmetry is more
or less altered, for some of these forms so habitually rest,
or creep, on one side that they are said to have a dorsal
and a ventral surface. A sea cucumber may be compared
to a sea urchin that has been drawn out in the direction
of the poles — that is, from mouth to anus — and further
to have lost most of the ossicles in the body wall so that
it is now flexible instead of being rigid. There are many

Tube feet

Tentacles

Fig. 193. Sea Cucumber.

microscopic spicules in the integument that give it rough-
ness and sometimes some degree of stiffness. Various
forms of holothurians are found along the Atlantic coast.
Some of the holothurians are so extremely elongated that
they are frequently mistaken for worms. Among the
Chinese and other West Pacific peoples, sea cucumbers,
under the name trepang, are variously prepared for food.
They are used principally for soups, and are considered
a great delicacy.

Echinodermata.

345

CLASS v. — THE CRINOIDEA.

Sea Lilies. — The stalked crinoids are borne on a slender
stalk of calcareous disks, so connected as to allow of con-
siderable freedom of motion. The body is flowerlike, with

branching arms surround-
ing the central mouth.
Most of the living crinoids
are found in deep seas,
and are known
as the sea lilies.
In shallow water
is found a form
that is stalked in
its earlier life, but
later the body,
with its feathery
arms, is set free
and swims away by the
motions of the arms. These
are known as the feather stars.
Crinoids. — Many fossil crinoids are
found in the Mississippi Valley. The
heads are less common, perhaps be-
cause, being softer, they have been
ground to powder. But it is common
to find portions of the stems, which
look like a series of buttons piled
one upon another, with a more or
less evident hole running through the
center. These appear to have been so abundant in the
seas of former ages that they have formed whole strata of
limestone rock.

Fig. 194. A Crinoid, or
Feather Star.

From Kellogg's Zoology.

346

Descriptive Zoology.

GENERAL CHARACTERISTICS OF ECHINODERMATA.

1. The body and its various organs are radially arranged.
But many show more or less bilateral symmetry.

2. In their development they all undergo a marked meta-
morphosis, the young being bilaterally symmetrical, and

only in a later stage acquiring
the radiate arrangement.

3. The surface has an exoskel-
eton of calcareous plates, with
movable spines.

4. There is a well-developed
digestive tube, distinct from the
body cavity.

5. There is a peculiar system
of water tubes by which tube feet

are extended and locomotion effected in the
free forms.

6. They reproduce by means of eggs, and
do not bud.

7. They do not occur in colonies.

8. They are all rather sluggish.

9. They are all, without exception,
marine.

10. They have remarkable power of
regeneration after mutilation.

The echinoderms were formerly
classed with the coelenterates on ac-
count of the radial arrangement of the
parts of the body ; but the echinoderms differ sharply
from the coelenterates in having a digestive tube distinct
from the body cavity, and in having a much higher devel-
opment, as shown in the variety and perfection of their

Fig. 195. Stone Lily
(Crinoid).

From Packard's Zoology,

Echinodermata. 347

organs. The echinoderms are a very distinct group,
standing apart from all other branches of the animal
kingdom.

CLASSES OF ECHINODERMATA.

Class I. Asteroidea — Starfishes.

Class II. Ophiuroidea — Sand Stars and Brittle Stars.

Class III. Echinoidea — Sea Urchins and Cake Urchins.

Class IV. Holothuroidea — Sea Cucumbers, or Sea Slugs.

Class V. Crinoidea — Sea Lilies and Feather Stars.

L

CHAPTER XXII.

BRANCH PLATYHELMINTHES.
The Flatworms.

[The word " worm " is used in a very loose and indefi-
nite way. In popular language it is applied indiscrimi-
nately to the legless earthworm, the insect larva with
segmented appendages (caterpillar), and to the elongated
mollusk styled the shipworm. All that is required to
merit the title is a soft, elongated, bilaterally symmetrical
body. This superficial view makes no distinction as to
whether the body is segmented or unsegmented, whether
appendages are present or absent, whether the form is
that of an adult or only in the larval stage, and asks no
questions as to internal structure. The old group of
" Worms " had no fundamental unity in plan of structure ;
in fact, they had nothing in common except a general simi-
larity in form. Hence it is natural that an increasing
knowledge should break up the old branch " Vermes."
In its stead we find what were formerly reckoned as
classes of the branch elevated to the rank of branches, as
follows : Platyhelminthes, the flatworms ; Nemathelmin-
thes, the roundworms ; Trochelminthes, the rotifers or
Wheel Animalcules ; the Molluscoida ; and the Annulata,
the segmented or ringed worms, such as the earthworm.]

The Platyhelminthes. — As the name indicates, the body
is flattened. They are bilaterally symmetrical, and with-
out skeleton or body cavity. There is no system of blood-
tubes. The body has three embryonic layers, ectoderm.

348

Platyhelminthes.

349

mesoderm, and endoderm. Many of them are parasites,
and some wholly lack a digestive tube. When present
the digestive tube has but one opening, the mouth. They
show a tendency to reproduction by self-division, and most
of them when cut in two develop two individuals.

The Tapeworm. — Probably the most widely known of
the flatworms are the tapeworms. These are parasites in
the digestive tube of various verte-
brates, including man. As the name
indicates, the body is ribbon-shaped,
sometimes attaining a length of thirty
feet. The body consists of segments,
or proglottids, a tapeworm ten feet
long having about eight hundred
segments. There is no mouth nor
digestive tube ; none is needed, as the
worm lives surrounded by material
digested by another animal, and the
parasite simply absorbs nourishment
through its skin. There is a distinct
head, whose chief work is that of at-
taching the worm to the lining of the
intestine ; this is secured by a circle
of hooks at the end of the head and
four sucking disks on the sides. For
a short distance from the head the body is unsegmented ;
then segments are formed by constrictions at intervals ;
farther on, the segments grow larger.

Development of the Tapeworm. — The hinder segments
of the tapeworm contain embryos. These segments drop
off and the embryos are set free, passing out with the
excrement. They are eaten by another animal, the hog,
for instance; in the intestine the embryo bores through the

Fig. 196. Tapeworm
{Tcenia solium).

In upper left hand corner of
figure the head much mag-
nified. After Leuckart. —
From Jordan and Kel-
logg's Animal Life.

350 Descriptive Zoology.

wall of the intestine into the muscles or other tissues.

Here it becomes flask-shaped (bladder worm) and develops

a head with hooks and suckers; but in this condition it

must remain unless eaten by some other animal. If the

flesh be cooked, the bladder worm (cysticercus) will be

killed. The danger comes in eating raw or half-raw meat.

If taken into the intestine of another animal, it attaches

by hooks, or suckers, or both, and the body elongates by

the formation of segments as above noted.

Kinds of Tapeworms. — Man is infested by at least

three different kinds of tapeworms, — one obtained from

pork, another from beef, and a third from fish ; but the

latter kind is seldom, if ever, found in this country.

Various animals have their own kinds of tapeworms,

usually getting them from a certain kind of animal on

which they prey; thus the dog has tapeworms which

have passed their larval stage in the muscles of the rabbit.

The cat gets a tapeworm from the mouse.

The Liver Fluke. — This is another of the flatworms. It

is a parasite in the liver of the sheep, living in the larger

bile ducts. The eggs develop into embryos which escape

with the excrement.

Then they pass into the

bodies of snails. Here

they reach the larval

stage. After leaving the

snail, they attach them-
FiG. 197. Liver Fluke, •'

Atrematodeworm. ^elvCS tO damp graSS

under water. If eaten
by sheep, they become fully developed worms like the adult
from whose eggs they developed. In England it was esti-
mated that 3,000,000 sheep were killed by the liver fluke in
1880, and that the average yearly loss is 1,000,000.

Platyhelminthes.

Nemathelminthes. 351

CLASSES OF PLATYHELMINTHES.

Class I. Trematoda — Liver Fluke.
Class 2. Turbellaria — (ciliated).
Class 3. Cestoda — Tapeworm.

BRANCH NEMATHELMINTHES.

THE ROUNDWORMS.

The roundworms have long, cylindrical bodies. They
are not segmented, but some of them have the appear-
ance of segmentation. Some are parasites in animals and
plants, while others live a free life. Most of the round-
worms belong to the class Nematoda.

Hair Worms. — These are often found as parasites in
grasshoppers and other insects, but later they live free
outside. They are by many ignorant people believed to
be horsehairs that have
"come to life" by soaking
in water.

The Vinegar EeL — This is
another small roundworm

, . , . ,, , Fig. iq8. Hair Worm.

which IS well known.

Intestinal Worms. — Two forms of roundworms are not
uncommon in the human intestine, especially in those of
children. The eggs or larvae have been swallowed with
food. The pinworm is well known ; it is small and white
and usually inhabits the rectum. The other is larger,
sometimes somewhat resembling an earthworm in size and
general appearance, though lacking the segments. It
belongs to the genus Ascaris.

Trichina. — The most dangerous of the parasitic round-
worms is Trichina. It is small, not exceeding an eighth

352

Descriptive Zoology.

of an inch in length. It is sometimes called the " pork-
worm." As is well known, this parasite is obtained by
eating raw or partially raw pork, and there is no danger
when the flesh is thoroughly cooked. If they gain access
to the intestine of the pig, the females bring forth alive a

Fig. 199. Trichina encysted in Human Muscle.

Highly magnified. — From Packard's Zoology.

large number of young. These bore their way outward
into the muscles and there inclose themselves in a sac or
capsule, where they may remain an indefinite time. If
this pork, uncooked, is eaten by man, the capsule is di-
gested and the larvae are set free. The young soon bore
through into the muscles and each worm gets into a muscle
cell and coils up in a case or "cyst," which it forms for
itself.

The Guinea Worm. — In the East Indies occurs another
parasite, the guinea worm. It is sometimes found two
feet long, embedded in the connective tissue under the
human skin. It is supposed that the eggs or larvae are
introduced in drinking water.

BRANCH TROCHELMINTHES.

THE ROTIFERS.

The Wheel Animalcule. — The word "Rotifer" means
wheel bearer, from the two circular disks at the anterior
end, around the borders of which are circles of cilia whose

Molluscoida. 353

motions resemble the rotation of a wheel. These disks
can be retracted when the animal wishes. The common
name for one of these animals is the " wheel animalcule."
As implied by the term animalcule, the animals are small,
usually not exceeding a thirtieth of an inch in length.
They occur in fresh water, and are usually to be found
when looking over minute water plants under the micro-
scope. They are transparent and are easily examined, all
their organs showing without dissection. Though small,
they are highly organized, having a complete digestive
system, the food being swept to the mouth by the cilia
bordering the disks. There is also a nervous system, with
one or more eyes.

They can swim by the action of the cilia and they also
progress by a looping movement, attaching alternately by

Fig. 200. Wheel Animalcule (Rotifer).

From Packard's Zoology.

the two ends of the body. The posterior part of the body
is a segmented *' tail " which can be withdrawn like a
telescope. It is said that after being dried for years,
they will revive when placed in favorable conditions, though
some authors think it is contained eggs that survive instead
of the adults.

BRANCH MOLLUSCOIDA.

This group gets its name from the fact that some of the
forms were once supposed to be mollusks. There are two
principal classes.

354 Descriptive Zoology.

The Polyzoa. — These are chiefly, though not entirely, ma-
rine and are known as the "sea mats" or "corallines."
They are also known as the "moss animals." These
names come from the fact that they grow in colonies like
mosses. They often incrust rocks with their skeletons,
which are either gelatinous, chitinous, or calcareous.
Each individual is frequently contained in a sort of cup,
into which it can retract or from which it can protrude to
a certain extent. There is a row of tentacles around the
mouth. One of our fresh-water forms (Pectinatella) has a
gelatinous basis or common body, which is found in spher-
ical masses as large as a man's head,
being attached to branches in the water.
The living animals are on the outside.
Such masses are often called "sponges"
by the fishermen.

The Brachiopods. — These are in-
closed in a bivalve shell, and are named
the " lamp shells." Their resemblance
to mollusks is very superficial, the
Fig. 201. Lamp Shells internal structure of the two being

(BRACHIOPODS). ^^^^jjy ^j^j.j^^ ^j^gj.^ jg ^g^^lly ^

circle of tentacles somewhat as in the Polyzoa. The
brachiopods are exclusively marine. They are attached
by a stalk which extends through the larger valve near the
hinge. There are many fossil brachiopods.

CHAPTER XXIII.
CLASSIFICATION OF THE ANIMAL KINGDOM.

(Parker and Haswell.)

Branch I. — Protozo'a.

Class I. RhTzop'oda — Amoe ba, Globigerrna.

Class II. Mastigoph'ora — Eugle'na, Vol'vox, Noctiruca.

Class III. Sporozo'a — Gregari'na.

Class V. Infuso'ria — Parame'cium, Vorticel'la.

Branch II. — PorKf'era.
Class I. PorTfera — sponges, fresh-water and marine.

Branch III. — CffiLENTERA'xA.

Class I. Hydrozo'a — Hy'dra, sea anemone.

Class II. Scyphozo'a — jellyfish.

Class III. Actinozo'a — corals.

Class IV. Ctenoph'ora (ten-oif -o-ra) — comb jellieSc

Branch IV. — PlAtyh£lmin'thes.

Class I. Turbella'ria — planarian worms.
Class II. Tremato'da— liver fluke.
Class III. Cesto'da — tapeworm.

Branch V. — NfiMATHELMiN'xHES.
Class I. Ngmato'da — roundworms, Trichina.

Branch VI. — Troch£lm!n'thes.

Class I. Rotlfera — wheel animalcules.
355

356 Descriptive Zoology.

Branch VII. — Molluscoi'da.

Class I. Polyzo'a — sea mats.

Class II. Brachiop'oda — lamp shells.

Branch VIII. — £chin6d£r'mata.

Class I. Asteroi'dea — starfish.

Class II. Ophiuroi'dea — brittle stars.

Class III. Echinoi'dea — sea urchins.

Class IV. Holothuroi'dea — sea cucumbers.

Class V. Crlnoi'dea — sea lilies.

Branch IX. — Annula'ta.

Class I. Chaetop'oda (ke-top'-o-da) — earthworm.
Class II. Gephyre'a (jef-e-re'-a).
Class III. Htrudin'ea — leech.

Branch X. — ArthrSp'oda.

Class I. Crusta'cea — ^^ crayfish, crab, barnacle, cy clops.

Class II. Myrlap'oda — centiped, milliped

Class III. Insec'ta — grasshopper, dragon fly, water bug, butterfly.

Order I. Thysanii'ra — small, wingless insects.

Order II. Orthop'tera — grasshopper, cricket, cockroach.

Order III. Odona'ta — dragon fly, damsel fly.

Order IV. HemTp'tera — water bug, iquash bug, cicada.

Order V. Neurop'tera — ant-lion.

Order VI. Lepidop'tera — butterfly, moth.

Order VII. DIp'tera — housefly, horse fly, flesh fly, mosquito.

Order VIII. Coleop'tera — May beetle, potato beetle, tiger beetle

Order IX. Hymenop'tera — bee, wasp, ant, gallfly, ichneumon fly
Class IV. Arach'nida — spiders, ticks, mites, daddy longlegs.

Branch XL — Mollus'ca.

Class I. Pelecyp'oda — clam, oyster, scallop, mussel.

Class II. Amphineu'ra — chl'ton (ki'-ton).

Class III. Gastrop'oda — snails, fresh-water and marine.

Class IV. Cgphalop'oda — squid, cuttlefish, oc'topus, nau'tilus.

Classification of the Animal Kingdom. 357

Branch XII. — Chorda'ta (kor-da'-ta).

Subb ranch I. Adglochor'da — Balanoglos'sus.
Subbranch II. Urochor'da — sea squirts.
Subbranch III. Vertebra'ta.

Division A. Acra'nia (without cranium) — lancelet.
Division B. Crania'ta — all other vertebrates.
Class I. Cyclostom'ata — lamprey eels.
Class II. Pifs'ces (pts'-sez) — fishes.

Subclass I. ElasmLbran'chii — shark, ray.
Subclass II. Holoceph'ali — Chimera.
Subclass III. Teleos'tomi.

Order I. Crossopterygii — Polyp'terus.
Order II. Chondrostei — sturgeon.

Order III. Holostei — gar pike, dogfish (of Central states).
Order IV. Teleos'tei — most bony fishes, such as catfish,
salmon, herring, mackerel, codfish, perch.
Subclass IV. Dip'noi — lungfish.
Class III. Amphib'ia.

Order I. Urode'la — mud puppy, siren, salamander.
Order II. Anu'ra — frog, toad.
Order III. Gymnophio'na — blind snake.
Class IV. Reptil'ia.

Order I. Squama' ta — lizard, snake.
Order II. Chelo'nia (ke-lo'-ni-a) — turtle.
Order III. Crocodtria — alligator, crocodile.
Class V. A'ves.

Division A. Ratl'tae (breastbone without keel) — emu, ostrich.
Carina'tae (breastbone keeled).
Pygop'odes — loon, grebe.
Impen'nes — penguins.
Turbina'res — pet'rels.
Steganop'odes — cormorant, pelican.
Herodio'nes — heron, stork.
An'seres — duck, goose.
Order VII. AccTp'itres — hawk, owl, vulture.
Order VI 1 1 . Crypturi — tinamou.
Order IX. Galli'nae — grouse, quail, turkey.
Order X. Gral'lae — rail, crane.
Order XI. Ga'viae — gull, tern.

Division B.

Car

Order

I.

Order

II.

Order

III.

Order

IV.

Order

V.

Order

VI.

J58

Descriptive Zoology.

LlmTc'oIce — snipe, plover.

Pterocle'tes — sand grouse.

Colum'bae — pigeon, dove.

Psit'tacI (sit'-a-si) — parrot, cockatoo.

Stri'ges (stri'-jez) — owls.

PIca'riae — woodpecker, cuckoo, humming bird,

Pas'seres — robin, lark, sparrow, thrush, crow.

Order XII.
Order XIII.
Order XIV.
Order XV.
Order XVI.
Order XVII.
Order XVIII.
Class VI. Mamma'lia.

Subclass I. Protothe'ria — duckbill, spiny ant-eater.
Subclass II. The'ria.

Section A. Metathe'ria (marsupials) — opossum, kangaroo.
Section B. Euthe'ria.

Order I. Edenta'ta — sloth, ant-eater
Order II. Ceta'cea — whale, porpoise, dolphin.
Order III. Sire'nia — manatee, dugong.
Order IV. Ungula'ta : —

Odd-toed (PerTssodac'tyls) — horse, tapir, elephant
Even-toed (Artiodac'tyls) — ox, sheep, deer, pig.
Order V. CarnTv'ora — dog, cat, bear, wolf, fox, seal.
Order VI. Roden'tia — rat, mouse, rabbit, squirreL
Order VII. InsectTv'ora — mole, shrew, hedgehog.
Order VIII. Chirop'tera — bat.
Order IX. Pri'mates — lemur, baboon, ape, man.

INDEX TO PART I.

Abalone, 136.

Abdomen of grasshopper, 2.

Aboral surface of starfish, 331.

Acrania, 148, 153.

Actinozoa, 325.

Adaptation, 15.

Adelochorda, 148.

Air bladder of fish, 155, 163.

Sacs of grasshopper, 5.
Of pigeon, 216.
Of snake, 201.

Tube of grasshopper, 5.
Albatross, 226.
Albumen, 219.
Alligator, 206.

Gar, 177.
Alternation of generations, 322.

In tunicates, 151.
Ambulacral plate, 339.
Ammonites, 144.
Amoeba, 286.

Dividing, 289.

Encysted, 289.
Amphibia, 181.
Amphioxus, 151.
Amphipoda, 84.
Ampullae, 333.
Angle, facial, 282.
Animalcule, bell, 294.

Slipi)er, 291.

Wheel. 352, 353.
Annulata, 87.
Anolis, 197.
Ant, 50, SI.

Ant-eater, 256, 257, 260.
Ant lion, 24.
Antelope, 273.
Antenna of grasshopper, 4.
Anthropoidea, 282,
Antidote for snake bites, 204.
Antlers, 274.
AnuiA, 195.

Aortic arches of earthworm, 95.

Aperture of snail shell, 127.

Apes, 282.

Aphids, 23, 50.

Appendix vermiformis, 283.

Arachnida, 55.

Arches, aortic, 95.

Aristotle's lantern, 340.

Armadillo, 259, 260.

Arms, oral, of jellyfish, 323, 324,

Of squid, 139.
Arrowfish, 140.
Arteries of crayfish, 68.
Arthropoda, i, 54, 77, 86.
Artificial selection, 218.
Artiodactyls, 267, 269.
Ascaris, 351.
Ascidians, 148, 149.
Assimilation in amoeba, 290.
Asteroidea, 331, 347.
Auks, 225.
Aurelia, 323.
Automatic action, 289.
Aves, 208.

Badger, 282.
Balancers, 32, 36.
Balanoglossus, 148.
Baleen plates, 265.
Barb of feathers, 208.
Barbadoes earth, 299.
Barbels of catfish, 173.
Barbules of feather, 208.
Bark lice, 24.
Barnacles, 81, 82.
Basket fish, 338.

Star, 338.
Bass, 166.
Batrachia, 181.
Bats, 264, 265.
Beach fleas, 84.
Beak of pigeon, 214.

359

36o

Index.

Beak of squid, 141.
Bear, 279, 280, 281.
Beavers, 262.
Bedbug, 24.
Bee glue, 47.
Bees, short-tongued, 49.
Bell animalcule, 294.
Belostoma, 20.
Benacus, 20.
Bend of wing, 209.
Berry lobster, 74.
Bighorn sheep, 270.
Bile duct of pigeon, 215.

Sac of snake, 201.
Bill of woodpecker, 237.
Bird, external features of, 210.
Birds, fossil, 242.

Game, 244.

Value of, 244.
Bison, 272.
Bittern, 229.
Black bass, 172.
Blackbirds, 239.
Black snake, 200,
Blacktail deer, 274, 275.
Bladder of crayfish, 70.

Urinary, of perch, 157.
Bladder worm, 350.
Blastostyle, 321.
Blind snake, 195.
Blister beetle, 41, 52.
Blood of earthworm, 94.
Blood tubes in earthworm, 94.
Blowfly, 35.
Bluebird, 240, 241.
Blue racer, 200.
Bobcat, 279.
Bobolink, 239.
Bob-white, 231.
Body cavity of earthworm, 89.

Of hydra, 314.

Of starfish, 335.
Borers, 40.
Botfly, 35.
Bowfin, 178.
Boxshell turtle, 205.
Brachiopods, 354.
Brachyura, 84.
Braconids, 52.
Brain of fish, 285.

Brain of mouse, 285.

Of pigeon, 217.

Of snake, 285.

Of sparrow, 285.

Of toad, 285.

Of vertebrates, 285.
Branchiostegal membrane, 160.
Branchiostoma, 151.
Breastbone of pigeon, 211.
Bristles of earthworm, 90.
Brittle stars, 331, 337.
Brood comb, 47.
Browsing, 277,
Bud of hydra, 314.
Budding of hydra, 317.

Of hydroid, 320.
Buffalo, 272.
Buffalo fish, 166, 173.
Bugs, 20.
Bulb, spinal, 285.
Bumblebees, 49.
Butcher bird, 240.
Byssus, 119, 125.

Cabbage butterfly, 27.

Cake urchin, 343.

Calcareous sponge, 308.

Camel, 277.

Canal, marginal of jellyfish, 323,

Canvasback, 228.

Capsule, egg, of earthworm, 88,

Thread of hydra, 315.
Carapace, 205.
Carinatae, 222, 223.
Carnivora, 278.
Carp, 166, 173.
Carpet beetles, 41.
Carrion beetles, 41.

Crow, 236.

Eaters, 217.
Cassowary, 222.
Catbird, 240.
Catfish, 166, 173.
Cats, 278.
Caucasian, 282.
Ceca of grasshopper, 7, 9.

Of perch, 157.

Of pigeon, 216.
Cecropia, 30.
Cecum of man, 283.

Index.

36

Cecum of rabbit, 250.
Cell, 301.

Wall, 301.
Celom, 89.

Cenosarc of hydroid, 320.
Centiped, 54.

Skein, 55.
Cephalization, 80.
Cephalopods, 138.
Cerebellum, 285.
Cerebrum, 285.
Cestoda, 351.
Chalk, 298.
Chameleon, 198.
Channel cat, 173.
Chickadee, 241.
Chimney swallows, 238.
Chinch bug, 23.
Chipmunk, 262.
Chitin, 84.
Chiton, 136.
Chordata, 148, 246, 284.
Chromatophores of squid, 141.
Cicada, 20, 22.
Cilia of earthworm, 96.

Of Paramecium, 293.

Of rotifer, 353.

Of vorticella, 295,
Ciliated chambers, 308, 310.
Circulation in clam, 116.

In crayfish, 68.

In earthworm, 94.

In frog, 184.

In grasshopper, 6.

In perch, 157, 159.

In pigeon, 216.

In rabbit, 251.

In snail, 130.

In snake, 202.

In squid, 142.

In starfish, 336.
Cirripedia, 83.
Clam, foot of, 105,

Fresh-water, 102.

Giant, 125,

Hard, 121,

Long, 120.

Muscles of, 109.

Razor-shell, 124.

Round, 121.

Clam, siphons of, 105, 108.

Soft, 120.
Clam shell, 102, 103,

Growth of, no.

Structure of, 109, no
Clavicle of pigeon, 213.
Claws of cat, 278.

Of dog, 279.
Click beetles, 41.
Climbing birds, 237.
Clitellum of earthworm, 88.
Cloaca of pigeon, 216.

Of snake, 201.

Of sponge, 310.
Cloven-footed animals, 269.
Clypeus of grasshopper, 2.
Cochineal insect, 24, 52.
Cockatoo, 237.
Cockroaches, 13.
Cocoons of ants, 50.

Of lepidoptera, 30,

Of spider, 59.
Codfish, 165, 172.
Codling moth, 30.
Coelenterata, 313.
Cold-blooded animals, 291.
Coleoptera, 36, 43.
Collar bones of pigeon, 213.
Colon, ascending. 283.

Descending, 283.

Transverse, 283.
Colonial protozoans, 305.
Colony of hydroids, 318.
Color dimorphism, 235.

Of fishes, 164.

Of frog, 185.

Of jellyfishes, 325.

Of rabbit, 252.

Of squid, 141.
Colorado potato beetle, 39.
Colors of birds, 219.
Commercial sponge, 309, 310.
Conchology, 146.
Condor, 236.

Condyle, occipital, in bird, 243.
Conjugation of protozoans, 297.
Constrictors, 200.
Contour feathers, 209.
Contractile vacuole, 286, 287, 295.
Contractility. 289.

362

Index.

Copepoda, 83.
Copperhead, 203.
Coracoid bone, 214.
Coral islands, 328.

Polyps, 325, 328.

Red, 329.

Reefs, 328.
Corallines, 354.
Cord, spinal, 285.
Cormorant, 227.
Corpuscles of birds, 245.

Of earthworm, 94.
Cougar, 279.
Cow, 269.
Cowbird, 220, 230.
Coxa of grasshopper, 2, 4.
Coyote, 279.
Crabs, 78.

Development of, 79.

Fiddler, 80,

Hermit, 81.

Horseshoe, 85.

King, 85.

Oyster, 79, 80.

Sand, 80.

Swimming, 79.
Crab's eyes, 75.
Crampfish, 170.
Cranes, 230.
Craniata, 148, 153.
Crayfish, 61, 65.

Blind, 81.

Distribution of, 76.

Enemies of, 73.

Holes, 61.
Crayons, 299.
Crickets, 13.
Crinoidea, 345, 347.
Crocodiles, 206, 207.
Crop of earthworm, 89, 93.

Of grasshopper, 7.

Of pigeon, 214, 215.
Croton bug, 13.
Crows, 239.

Carrion, 236.
Crustacea, 61.
Cubs, 281.
Cuckoos, 221, 237.
Cud chewers, 269.
Cunner, 171.

Curculios, 41.
Currant worm, 51.
Cuticle of vorticella, 295.
Cuttlefish, 145.
Cyclops, 83, 84.
Cyclostomata, 148, 153.
Cyst, 289.

Cyst of trichina, 352.
Cysticercus, 350.

Daddy longlegs, 60.

Damsel flies, 13,

Darning needles, 14.

Darters, 171.

Decapoda, 84.

Deer, 273, 274.

Deer flies, 34.

Development of ascidians, 149

Of clams, 118.

Of crabs, 79.

Of earthworm, 97.

Of frog, 187, 189.

Of grasshopper, 10.

Of honey bee, 47, 48.

Of house fly, 32.

Of hydroid, 320.

Of jellyfish, 324.

Of lepidoptera, 28.

Of metazoa, 302.

Of oyster, 122.

Of perch, 162.

Of rabbit, 254.

Of retrograde, 150.

Of sea anemone, 327.

Of sea urchin, 341.

Of sponge, 311.

Of starfish, 337,

Of tapeworm, 349.

Of vorticella, 296.
Devilfish, 170.
Devil's needles, 14.
Dewclaws, 269.
Diamond rattlesnake, 203.
Diaphragm of rabbit, 249, 251.
Differentiation, 304.
Digestion in amoeba, 290.

In crayfish, 65.

In hydra, 316.

In sea anemone, 326.
Digestive gland in clam, 115.

Index.

i63

Digestive gland in starfish, 334.
Digestive system of clam, 115.

Of crayfish, 65.

Of earthworm, 89, 92.

Of frog, 181, 183.

Of grasshopper, 7,

Of perch, 156.

Of pigeon, 214.

Of rabbit, 250.

Of sea urchin, 340.

Of snail, 129.

Of snake, 200, 201.

Of squid, 141.

Of starfish, 334.
Digitigrade animals, 280.
Dingo, 259.
Diphycercal tail, 162.
Diplocardia, 95.
Dipnoi, 180.
Diptera, 32.
Discoid shell, 128.
Disk of starfish, 331.

Of tapeworm, 349.
Distribution of crayfishes, 76.

Of earthworms, 97.

Of feathers, 209.

Of fishes, 166.

Of oysters, 123.

Of protozoans, 300.
Diving birds, 224.
Division of amoeba, 289.

Of labor, 302, 303.
Dogday harvest fly, 22.
Dogfish, 168, 169, 178.
Dogs, 279.
Doves, 233.
Down, 209.
Dragon fly, 13, 15.
Drones, 46.
Duckbill, 256.
Ducks, 228.
Dugong, 266.
Dung beetles, 40.
Duodenum of man, 283.

Of pigeon, 215.

Eagles, 233.
Ears of owls, 234.
Ear-shell, 136.
Earthworms, 87,

Earthworms, distribution of, 97.

Muscles of, 89.
Eating in amoeba, 290.

In crayfish, 64.

In Paramecium, 293.

In ruminants, 269.

In starfish, 335.
Echinodermata, 331, 346.
Echinoidea, 338, 347.
Ectoderm of hydra, 313.

Of sponge, 308.

Of vorticella, 295.
Ectoplasm, 286.
Edentates, 259.
Eels, 176.

Lamprey, 153.

Round-mouthed, 153.
Efts, 192.
Eggs of birds, 218.

Of crayfish, 73.

Of earthworm, 97.

Of fishes, 164.

Of hydra, 317.

Of jellyfish, 323.

Of medusa, 321.

Of snail, 134.

Of snake, 202.

Of sponges, 311.

Shell, 219.
Egret, 229.

Elasmobranchii, 168, 180,
Electric fishes, 164.

Light bugs, 18.

Ray, 170.
Elephant, 277.
Elk, 273, 275 (Frontispiece),
Embryo of sponge, 311.

Of tapeworm, 349.
Emu, 222.

Enamel of rabbit's teeth, 248.
Encysted amoeba, 289.
Endoderm of hydra, 313.

Of sponge, 308.

Of vorticella, 295.
Endoplasm, 286.
Entomostraca, 83.
Epicranium of grasshopper, 4.
Epidermal plates of turtle, 205.
Epidermis of clam, 109.
Epiglottis of rabbit, 250.

3^4

Index.

Equilibrium sense of crayfish, 72.

Of perch, 161.
Ermine, 282.
Esophageal collar, 70.

Of grasshopper, 8, 9.

Ring, 70.
Ewes, 271.
Excretion in amoeba, 291.

In crayfish, 69.

In earthworm, 95.

In frog, 185.

In grasshopper, 8.

In Paramecium, 293.

In perch, 161.

In pigeon, 216.

In rabbit, 252.

In snail, 130.

In snake, 202.
Exumbrella, 321.
Eyed elater, 41.
Eyes of grasshopper, 8, 9.

Of snail, 133.

Of snake, 199.

Of squid, 139.

Facial angle, 282.
Falconidae, 233.
Fangs of snakes, 203, 204.
Feathers, development of, 208.

Distribution of, 209,

Kinds of, 209.

Structure of, 208.
Feather stars, 331, 345, 347.
Feet of pigeon, 212.
Femur of grasshopper, 4.
Ferret, 282.

Fertilization of sea urchin's egg, 342.
Filament, gastric, of jellyfish, 323.

Mesenterial, 326.
Finches, 239.
Fins of fishes, 163.

Of perch, 154.
Firefly, 42,
Fish, 154, 170.

Brain, 285.

Hatcheries, 166.

Laws, 166.
Fish ways, 166.
Flagella, 297,

Of hydroJd, 320.

Flagella of sponges, 307.
Flatfishes, 163, 175.
Flatworms, 348.
Flesh eaters, 278.
Flight of pigeon, 208.
Flippers of seals, 282.
Floating of fish, 155.
Flounder, 166, 175, 176.
Flukes of whale's tail, 265.
Flycatchers, 239.
Flying fish, 176.

Foxes, 265.

Muscles of pigeon, 211.
Food of clam, 113.

Of crayfish, 64.

Of earthworm, 92.

Of frog, 181.

Of perch, 156.

Of pigeon, 214.

Of rabbit, 247.

Of sea urchin, 341.

Of snake, 200.

Of squid, 142.

Of starfish, 335.
Food balls of Paramecium, 292, 293.
Food fishes, 165.
Food vacuole, 286, 287.
Foot of clam, 105, 106, 108.

Of snail, 129.
" Form " of rabbit, 246.
Fossils, 285.

Birds, 242.

Bird tracks, 207.

Brachiopods, 354.

Crinoids, 345.

Reptiles, 207.
Fox, 279.
Fresh-water clam, 102.

Sponges, 310.
Frogs, 181, 192.
Function, 305.
Functions of animals, 304.
Fur of rabbit, 246.

Gall, 51.

FHes, 51.

Gnat, 35.
Gallinaceous birds, 330.
Gallinae, 230.
Game birds, 244.

index.

365

Game fishes, 172.
Ganglions of clam, 117.

Of crayfish, 70,71.

Of frog, 188.

Of grasshopper, 8-
Ganoids, 177.
Gar pike, 177.
Garter snake, 200.
Gastric filaments of jellyfish, 323.

Pouches of jellyfish, 323.
Gastropods, 127.
Geese, 228.
Gemmule, 311.

Genital plates of sea urchin, 341.
Gephyrea, loi.
Giant water bug, 18.
Gila monster, 198,
Gill chamber of crayfish, 68.

Paddle of crayfish, 68.

Rakers of perch, 160.

Scoop of crayfish, 68.
Gills of clam, iii, 113.

Of crayfish, 66, 67.

Of dragon-fly larva, 13.

Of mud puppy, 191.

Of perch, 158.

Of sea slug, 135.

Of siren, 190.

Of snail, 134.

Of tadpole, 189.
Giraffe, 277.
Gizzard of earthworm, 89,93.

OiF pigeon, 215.
Gland cells of sea anemone, 326.
Glands, digestive, of crayfish, 65, 66.

Digestive, of starfish, 334,

Green, of crayfish, 69.

Salivary, of rabbit, 250.

Scent, 282.

Setigerous, 90.
Glass-snake, 199, 205.
Globigerina, 298, 299.
Glochidia, 118.
Glowworm, 42.
Gnathostomata, 148.
Gnawers, 260,
Goats, 272.
Gonads of jellyfish, 323.

Of medusa, 321.
Gopher, pouched, 263.

Gopher turtle, 206.
Gorilla, 282, 283.
Gossamer, 58.
Grasshopper, i, 12, 15.
Grebes, 224.
Grizzly bear, 281.
Grosbeak, cardinal, 239.

Rose-br6asted, 239.
Ground beetle, 39,
Grouse, 231.
Growth of amoeba, 290.

Lines of clam, 103.

Of clam shell, no.

Of crayfishes, 74.
Grubs, 38.
Guinea fowl, 232.

Worm, 352,
Gullet of cow, 270.

Of earthworm, 89, 93.

Of man, 283.

Of Paramecium, 292.

Of perch, 157.

Of rabbit, 250.

Of sea anemone, 325.

Of snake, 201.
Gulls, 225.
Gymnophiona, 195.

Haddock, 165.
Hagfishes, 153.
Hair worms, 351.
Hake, 165,
Halibut, 166, 176.
Hal teres, 36.
Hand, 282.
Hare lip, 255.
Hares, 260.
Harvestmen, 60.
Hawk, cooper's, 233.

Fish, 233.

Sharp-shinned, 233.
Hawkbill turtle, 205.
Hawk moth, 28, 29.
Head of pigeon, 214.

Of squid, 139.

Of tapeworm, 349.
Heart of crayfish, 68, 69.

Of grasshopper, 6.

Of rabbit, 249, 250, 251.
Heat-production in amceba, 291.

3^6

Index.

Hedgehog, 264.

Heel of pigeon, 212.

Hell-diver, 224.

Hemiptera, 18.

Hermit crab, 81, 82.

Herons, 229.

Herring, 166.

Hessian fly, 35.

Heterocercal tail, 162.

Hexacoralla, 328.

Hibernation of frog, 186.

Hind wing of grasshopper, 4.

Hinge ligament of clam, 103, 106, 107.

Teeth of clam, cardinal, 104.
Lateral, 104.
Hippopotamus, 269.
Hive of honey bees, 46.
Hog, 269.

Hollow-horned ruminants, 270.
Holothuroidea, 343, 347.
Homocercal tail, 162.
Honey, 47.

Bee, 44, 45.

Comb, 47, 48.

Comb of cow, 270.

Dew, 50.
Hoofs, 266.

Hooks of tapeworm, 349,
Horned toad, 198.
Hornets, 49.

Horns of ungulates, 270, 273.
Horny sponges, 309.
Horse, 267.

Fly, 33. 34-
House fly, 32.
Humming bird, 238,

Moth, 28.
Humming miller, 28.
Hydra, 313.

Hydroids, 317, 318, 319,
Hydrotheca, 320.
Hydrozoa, 317.
Hyena, 280.
Hymenoptera, 44.
Hypostome of hydra, 313.

Of hydroid, 319.

Ichneumon flies, 51.
Iguana, 198.
Incisors of rabbit, 248.

Incubation, 219.

Indigo bird, 239.

Individual, 306.

Ink bag of squid, 140.

Ink galls, 52.

Insecta, i.

Insect eaters, 263.

Interambulacral plates of sea urchin

339-
Intestinal worms, 351.
Intestine of clam, 115.

Of crayfish, 64, 66.

Of frog, 182, 183.

Of man, 283.

Of perch, 157.

Of pigeon, 215.

Of rabbit, 249, 250.

Of snake, 201.

Of starfish, 335.
Irritability, 289.
Isopoda, 84.
Itch mite, 60.

Jackal, 279.
Jack rabbit, 260.
Jacksnipe, 230.
Jaguar, 279.
Jay, 239.

Jellyfishes, 323, 324.
Joint-snake, 199.
June bug, 36, 37.

Kangaroo, 259.
Katydid, 12.
Keel of pigeon, 211,
Keyhole urchin, 343.
Kidneys of clam, 115, 116.

Of crayfish, 69.

Of earthworm, 96.

Of frog, 182, 185.

Of perch, 157, 161.

Of pigeon, 215, 217.

Of rabbit, 249, 252.

Of snail, 130.

Of snake, 201, 202.
Killdeer, 230.
Kingbird, 239.
King crab, 85.
Kingfisher, 237.
Kiwi, 222.

Index.

367

Labrum of grasshopper, 4.
Lac insect, 24.
Ladybug, 41, 44.
I^ke trout, 165.
Lamb, 271.
Lamp shells, 354.
Lamprey eels, 153.
Lancelet, 151.
Language, 283.
Larva of dragonfly, 13,
Lateral line of perch, 154.
Leaf rollers, 31.
Leech, 100.
Left-hand shells, 128.
Lemur, 282.
Leopard, 279,
Lepidoptera, 25.
Lice, 24.
Limestone, 299.
Limnea, 134.
Limpet, 136.
Lingual ribbon, 129.
Lion, 279.

Mountain, 279.

Sea, 282.
Lip of snail shell, 127.
Liver of frog, 182,

Of pigeon, 215.

Of rabbit, 249, 250.

Of snake, 201.
Liverfluke, 350.
Lizard, 196, 197,
Lobster, 63, 'j'j.

Pot, 77.
Locomotion of amoeba, 287, 290.

Of clam, 108.

Of crayfish, 62.

Of earthworm, 91.

Offish, 155.

Of frog, 181.

Of grasshopper, 3.

Of hydra, 316,

Of rabbit, 247.

Of sea urchin, 340.

Of snake, 200,

Of starfish, 332, 334.
Locust, II, 12.

Long-winged swimmers, 225.
Loon, 224, 225.
Lung-book of spider, 56,

Lung-fish, 179.

Lungs of frog, 182, 183.

Of pigeon, 215, 216.

Of rabbit, 249, 251.

Of snake, 201.

Of spider, 56.
Lymphatic system of frog, 185.
Lynx, 279.

Macaws, 237.

Mackerel, 165, 171.

Macronucleus of Paramecium, 292.

Of vorticella, 295.
Macrura, 84.
Madreporic body, 332.

Canal, 334.

Plate, 333.
Maggot, 34.
Malacostraca, 83.
Mallard, 228.
Mammalia, 246, 256.
Mammoth, 278.
Man, 282.
Manatee, 266.

Mandible of grasshopper, 2, 4.
Mantid, 13.
Mantle of clam, 104.

Lines, 109.

Of squid, 139.
Manubrium, 321.
Manyplies, 270.
Maple scale insect, 23.
Marmoset, 282.
Marsipobianchii, 153.
Marsupial, 257.

Bone, 257.
Marten, 282.
Martin, 240.
Mascalonge, 167.
Mastodon, 278.
Maxilla of grasshopper, 4.
May fly, 14.
May beetle, 36.
Meadow lark, 239, 242.
Measuring worm, 31.
Medusa bud, 320.
Medusae, 321.
Megatherium, 260.
Menhaden, 165.
Mesenterial filaments, 326.

368

Index.

Mesenteries of sea anemone, 326.

Of starfish, 335.
Mesentery of rabbit, 251.
Mesoderm of sponge, 308.
Mesogloea of Hydra, 313.
Mesothorax of grasshopper, 2.
Metamorphosis, 30.
Metathorax of grasshopper, 2.
Metazoa, 300.
Mice, 262.
Micronucleus of paramecium, 292.

Of vorticella, 295.
Mid brain, 285.
Midges, 34.
Migration of birds, 220.

Of fishes, 165,
Milkweed butterfly, 25.
Milliped,54.
Mimicry, 31.
Mink, 282.
Mite, 9, 60,

Mocking bird, 240, 241.
Molars of rabbit, 248.
Mole, 263.
Mollusca, 102.
MoUuscoida, 353.
Monarch butterfly, 25, 26, 31.
Monitor, 198.
Monotremata, 256.
Moose, 273, 276, 277.
Mosquito, 35.

Hawk, 14.
Moss animals, 354.
Mother Carey's chickens, 226.
Mother-of-pearl, 136.
Moths and butterflies, 28.
Motion of amoeba, 287, 290.
Molting of birds, 219.

Of crayfishes, 74.

Of king crab, 85.

Of snakes, 204.

Of spiders, 56.
Mountain lion, 279.

Sheep, 271,
Mourning doves, 233.
Mouse brain, 285.

Hawk, 240.
Mouth of earthworm, 92.

Of hydra, 313, 314.
Mud eel, 190.

Mud fish, 178.

Nest, 180.

Puppy, 191.
Mule deer, 275.
Mullet, 165.
Multiplication of amoeba, 289.

Of hydra, 317.

Of hydroids, 321.

Of Paramecium, 294.

Of protozoa, 296.
Muscle pectoral of pigeon, 211.

Scars of clam shell, 103, 104.

Subclavian of pigeon, 212.
Muscles of clam, 106, 109.

Of crayfish, 62.

Of earthworm, 89, 92.

Of grasshopper, 3.

Of sea anemone, 327.

Of starfish, 331.
Mussel, salt-water, 124.
Myriapoda, 54.

Natica, 134, 135.
Nautilus, 144.
Neck of pigeon, 214.
Necturus, 191.
Nemathelminthes, 351.
Nematocysts of hydra, 315.
Nereis, 99.

Nerve collar of earthworm, 89.
Nerve ring of crayfish, 71.

Of earthworm, 96.
Nervous system of clam, 117.

Of crayfish, 70, 71.

Of earthworm, 96.

Of frog, 187, 188.

Of grasshopper, 8.

Of pigeon, 217.

Of rabbit, 249, 254.

Of sea urchin, 341.

Of snail, 130.

Of squid, 142.

Of starfish, 336.
Nettle cells of sea anemone. 326.
Neuroptera, 24.
Newts, 192.
Nighthawk, 238.
Noctiluca, 298.
No-see-ems, 34.
Nolochord, 148.

Index

369

Nucleus, 286, 287, 301.

Of Paramecium, 294.
Numbfish, 170.
Nuthatch, 241.
Nymph, 13.

Octocoralla, 329.

Octopus, 143.

Odonata, 13, 15.

Odor of snakes, 204.

Oil gland of pigeon, 215, 217.

Olfactory lobe, 285.

One-celled animals, 286.

Opercle of perch, 154, 160.

Operculum of snail, 128, 129.

Ophiuroidea, 337, 347.

Opossum, 257, 258.

Oral arms of jellyfish, 323.

Surface of starfish, 331.
Orang-utan, 283.
Organism, 305.
Organs, 304.
Orioles, 239, 243.
Orthoceras, 144.
Orthoptera, 12.
Osculum of sponge, 307.
Osphradia of snails, 130.
Osprey, 233.
Ossicles of sea urchin, 338.

Of starfish, 331.
Ostracoda, 83.
Ostriches, 222, 223.
Otter, 282.
Ovary of bird, 218.

Of crayfish, 65.

Of earthworm, 89, 91.

Of frog, 182, 183.

Of grasshopper, 10.

Of hydra, 313, 317.

Of perch, 157.

Of sea urchin, 341.

Of snake, 201.
Oviduct of crayfish, 65.

Of earthworm, 97.

Of frog, 182, 183, 189.

Of grasshopper, 10.

Of perch, 157, 162.

Of pigeo.i, 215, 219.

Of snake, 201.
Ovipositor of grasshopper, 10.

Ovum, 302.
Owls, 234, 235.
Oyster, 122.

Crab, 79, 80.

Distribution of, 123.

Season, 123.

And starfish, 335.

Palp of clam, iii, 114.
Palpus of grasshopper, 4.
Pancreas of pigeon, 215.

Of rabbit, 249, 250.

Of snake, 201.
Panther, American, 279.
Paramecium, 291, 292.
Parasites of grasshopper, 9.

Of rabbit, 252.
Parasitic arachnids, 60.

Birds, 220.

Crustacea, 83.

Hymenoptera, 52.

Protozoa, 297.

Worms, 349, 351, 352.
Parrakeet, 236, 237,
Parrots, 236.
Partridge, 231.
Paunch of cow, 270.
Peafowl, 232.
Pear-tree slug, 51.
Pearls, 126.
Peccary, 269.
Pectinatella, 354.
Pedicellariae of sea urchin, 340.

Of starfish, 332.
Pelecypoda, 102.
Pelican, 228.
Pen of squid, 139.
Penguins, 225,
Perch, 154.

Development of, 162.

Fins of, 154.

Opercle of, 154, 160.

Ringed, 154.

Sea, 171.
Perching, 213.

Birds, 239.
Pericardium of clam, 115.
Periodical cicada, 22.
Perisarc of hydroid, 320.
Perissodactyls, 267.

370

Index,

Peristaltic action, 94.

Peritoneum of rabbit, 251.

Petrels, 226.

Pewee, 239, 240.

Pharynx of earthworm, 89, 92.

Pheasants, 232.

Phyllopoda, 83.

Phylloxera, 24.

Physa, 134.

Pickerel, 166, 167.

Pigeon, 208.

Origin of, 218.
Pigment in fishes, 1&4.
Pike, 166, 167.

Perch, 171.
Pinchers of crayfish, 73.

Of sea urchin, 340.

Of starfish, 332.
Pin feathers, 209.
Pinnigrade animals, 282.
Pinworm, 351.
Pisces, 168.

Placental mammals, 259,
Plaice, 176.
Planorbis, 127, 134.
Plant lice, 23.
Plantigrade animals, 280.
Plastron, 205.
Plates, epidermal, of turtle, 205.

Genital, of sea urchin, 341.
Platyhelminthes, 348.
Plovers, 230.
Plumes of egret, 229.

Of ostrich, 222.
Poison gland of honey bee, 46.
Poisonous snakes, 203.
Polishing powders, 299.
Pollen baskets, 46.
Polyp, coral, 325, 328.

Fresh-water, 313.
Polyphemus, 30.
Polyzoa, 354.
Pond snails, 129, 133.
Porcupine, 261.
Porifera, 307.
Pork worm, 352.
Porpoise, 266.
Portal vein of perch, 159.
Portuguese man-of-war, 322, 323.
Potato beetle, 39.

Prairie dog, 263.

Hen, 231.

Wolf, 279.
Prawns, 77.
Prey, birds of, 233.
Primaries, 210, 211.
Primates, 282.
Proboscis of elephant, 277.

Of snail, 133.
Proglottids, 349.
Pronghorn, 273.
Propagation of fishes, 166.
Propolis, 47.
Proteid, 301.

Prothorax of grasshopper, 2.
Protoplasm, 286, 300, 301.
Prototheria, 256,
Protozoa, 286, 296, 300.

Colonial, 305,

Distribution of, 300.

Shell-bearing, 298.
Proventriculus of pigeon, 215:,
Psalterium of cow, 270.
Pseudopod, 286, 287.
Ptarmigan, 231.
Puffins, 225.
Puma, 279.
Puparium, 33, 34.
Purple finch, 239.

Quahog, 121.

Quail, 231.

Queen, honey bee, 46.

Cells, 48.
Quills, 209.

Of porcupine, 261.

Rabbit, 246.

In Australia, 253.

Development of, 254.

Nervous system of, 254,

Structure of, 249.
Raccoon, 281.
Rails, 230.
Raptores, 233, 235.
Ratitae, 222.
Rats, 262.

Rattlesnake, 203, 204.
Rays, 168, 169,

Of starfish, 331.

Index.

37'

Recovery of earthworms, 98. .

Of hydra from mutilation, 317.

Of starfish from mutilation, 335.
Rectum, 283.
Red coral, 329.

Deer, 274.
Rennet, 270.

Reproduction of amoeba, 289, 291.
Reptiles, 196.

Age of, 207.

Extinct, 207.
Respiration in amoeba, 290.

In clam, no.

In crayfish, 66.

In earthworm, 95.

In frog, 183.

In gastropods, 130.

In grasshopper, 5.

In perch, 158.

In pigeon, 216.

In rabbit, 251.

In sea urchin, 341.

In snail, 133.

In snake, 201.

In squid, 142.

In starfish, 336.
Restoration of limbs in crayfish, 75.
Reticulum of cow, 270.
Rhinoceros, 268.
Ribs of snake, 199, 200.
Right-hand shell, 128.
Ringed perch, 154, 171.
Robin, 241.
Rodents, 260.
Rose slug, 51.
Rotifers, 352, 353.
Roundworms, 351.
Rove beetles, 41.
Ruffed grouse, 232.
Ruminants, 269.

Solid-horned, 273,

Sage hen, 231.
Salamanders, 191.
Salmon, 165, 174.
Sand cake, 343.

Dollar, 343.

Hoppers, 84.

Star, 337, 338.

Worm, 99.

Sapsucker, 238.
Sardine, 165.
Sawflies, 51.
Scale bugs, 24.
Scales of butterfly, 25.

Of fishes, 162.

Of lizard, 196.
Scallop, 125.
Scent gland, 282.
Scorpion, 60.

Scutellum of grasshopper, 4.
Scutes of snake, 200.
Scutum of grasshopper, 4.
Scyphozoa, 323.
Sea anemone, 325, 326.

Cucumber, 331, 343, 344,

Eggs, 339-

Fans, 329.

Lilies, 331, 345.

Lion, 282.

Mats, 354.

Pear, 149.

Pen, 329.

Perch, 171.

Squirt, 149.

Turtle, 205.

Urchin, 331, 338, 339.

Whip, 329.
Seals, 282.

Secondaries, 210, 211.
Segmentation of egg, 343.
Senses of clam, 118.

Of crayfish, 72.

Of earthworm, 97.

Of frog, 187.

Of gastropod, 130.

Of grasshopper, 8.

Of jellyfish, 323.

Of perch, 160, 161.

Of pigeon, 217.

Of rabbit, 255.

Of snake, 202.

Of squid, 142.

Of starfish, 336.
Sepia of squid, 141.
Serpent stars, 338.
Setae of earthworm, 90.
Seventeen-year locust, 2a.
Sexton beetles, 41.
Shad, 165.

372

Index.

Sharks, i68, 169.
Shedding of horns, 273.
Sheep, 270.

Shell of sea urchin, 339.
Shipworm, 123.
Shore birds, 230.
Shrews, 264.
Shrike, 240.
Shrimp, ^^.
Silica, 299.
Siliceous earth, 299.

Sponges, 309.
Silkworm, 30.
Silvertip bear, 281.
Sinus, blood, of crayfish, 69.
Siphon of squid, 140.

Of clam, 105, 108.
Siren, 190.
Skate, 169, 170.
Skeleton of arthropods, 86.

Of birds, 245.

Of bony fishes, 170.

Of insects, 52.

Of pigeon, 208, 213.

Of sea urchin, 338.

Of shark, 168.

Of sponge, 308.

Of starfish, 331,
Skin of earthworm, 90.
Skipjacks, 41.
Skippers, 35.
Skunk, 282.
Slaves of ants, 51.
Slipper animalcule, 291.
Sloths, 259.
Slugs, 132.

Sea, 135.
Smell in birds, 217.

In crayfish, 72.

In deer, 277.

In rabbit, 255.

In snails, 130.
Smelling patches, 130.
Smelt, 165.
Snails, land, 131.

Pond, 133.

River, 134.

Sea, 135.

Shell, 127.
Snake doctors, 14.

Snake feeders, 14.
Snakes, 199, 205.

Brain, 285.

Poisonous, 203, 204.
Snipe, 230.
Snout beetles, 41.
Social bees, 49.
Sole, 176.

Solid-horned ruminants, 273,
Solitary bees, 49.
Sowbug, 84.
Spanish fly, 41.
Sparrows, 239.

Brain, 285.

English, 239.
Specialization, 304.
Speech, 282.
Sperm cells of hydra, 317.

Of sponge, 311.
Spermary of fish, 162.

Of hydra, 314, 317.

Sea urchin, 341.
Sperms of hydra, 317.

Of jellyfish, 323.

Of medusa, 322,

Of sponges, 311,
Sphinx moth, 28.
Spicules of sponge, 307, 308, 309.
Spiders, 55.

Jumping, 56.

Trapdoor, 59.

Web, 57.
Spinal bulb, 285.

Cord, 285.
Spindles, 14.
Spines of sea urchin, 338, 339.

Of starfish, 331.

Of sting cells, 315.
Spinnerets of spider, 57.
Spinning of spiders, 56.
Spiny-rayed fish, 171.
Spiracles, 5.
Spleen of snake, 201.
Sponges, 307.

Calcareous, 308.

Commercial, 309, 310.

Development of, 311.

Flagelia, 307, 308.

Fresh-water, 310.

Horny, 309.

Index.

373

Sponges, in reservoirs, 311.

Siliceous, 309.
Spongin, 309.
Spoonbill catfish, 178.
Spouting of whales, 266.
Spring beetles, 41.
Squash bug, 20, 21.
Squid, 138.

Giant, 143.
Squirrels, 263.

Flying, 263.

Fox, 263.

Gray, 263.

Red, 263.
Stable flies, 34.
Stag-beetles, 40.
Stake driver, 229.
Starfish, 331, 332.

Development of, 337.
Sting of honey bee, 46.

Cells of hydra, 314.

Cells of jellyfish, 323.

Rays, 169.
Stomach of crayfish, 65, 66.

Of frog, 182, 183.

Of jellyfish, 323.

Of man, 283.

Of perch, 157.

Of pigeon, glandular, 215.

Of rabbit, 249, 250.

Of ruminant, 270.

Of sea anemone, 326,

Of snake, 201.

Of starfish, 334.
Stone canal of starfish, 333, 334.
Stork, 229.
Striped bass, 171.
Sturgeon, 165, 177.
Subumbrella, 321.
Suckers, 166, 173.

Squid, 139.
Sulphur-bottom whale, 266.
Sunfish, 171.

Sutures of snail shell, 127.
Swallows, 240.

Bank, 240,

Bam, 240.

Chimney, 238.

Eave, 240.

Fork-tail, 240.

Swallowing in snakes, 199, 200.

Swallow-tail butterflies, 30.

Swarming, 48.

Swifts, 197, 238.

Swim bladder of perch, 155.

Swimming of crayfish, 62.

Offi-og, 181.

Of jellyfish, 321, 325.

Of perch, 155.

Of squid, 140.
Syrinx of pigeon, 218.

Tadpole, 189.

Tail fin of crayfish, 62.

Of squid, 140.
Tails of fishes, 162.
Tapeworm, 349.
Tapir, 267, 268.
Tarantula, 59.
Tarsus of grasshopper, 4.

Of pigeon, 212.
Taste in crayfish, 72.
Teeth of rabbit, 248.

Of sea urchin, 340.

Of snake, 199.
Teleostei, 180.
Teleostomi, 180.
Temperature of amoeba, 291.

Of frog, 186, 187.

Of insects, 7.

Of mammals, 251, 283.

Of pigeon, 216.

Of rabbit, 251.
Tentacles of hydra, 313.

Of jellyfish, 323.

Of sea anemone. 325.

Of sea slug, 135.

Of snail, 130, 131.
Terns, 225.
Tertiaries, 210, 211.
Theria, 256, 257.
Thistle bird, 239.
Thornbacks, 170.
Thousand legs, 54.
Thread capsules of hydra, 315.
Thrush, brown, 240.

Wood, 240.
Thumb of bird, 211.
Tibia of grasshopper, 4.
Ticks, 60.

374

Index.

Tiger, 279.

Beetle, 40.
Timber wolf, 279.
Tissues, 304.
Toads, 192.

Brain, 285.
Toes of pigeon, 212.
Tomato worm, 28.
Tongue of snake, 199.

Of frog, 182.

Of woodpecker, 237.
Torpedo, 170.
Tortoise shell, 205.
Totipalmate birds, 227.
Touch in amoeba, 291.

In catfish, 173.

In clam, 118.

In crayfish, 72.

In earthworm, 97.

In frog, 187.

In grasshopper, 9.

In perch, 161.

In pigeon, 217.

In rabbit, 255.

In snail, 130.
Tracheae in grasshopper, 5.
Tracks of rabbit, 247.
Tree frog, 193.

Toad, 193.
Trematoda, 351.
Trepang, 344.
Trichina, 351, 352.
Tridacna, 125.
Trigger-hair of hydra, 315.
Tripoli, 299.

Trochanter of grasshopper, 2, 4.
Trochantine of grasshopper, 2, 4.
Trochelminthes, 352.
Trout, 174.

Tube feet of starfish, 332.
Tube-nosed swimmers, 226.
Tubularian hydroid, 320.
lunicates, 148, 149.
Turbellaria, 351.
Turkey, 231, 232,

Buzzard, 235, 236.
Turtle, boxshell, 205.

Gopher, 206.

Green, 205.

Hawkbill, 205.

Turtle, sea, 205.

Snapping, 206.
Turtledove, 233,
Tusks of elephant, 278.
Tympanum of frog, 187.
Typhlosole, 92, 94.

Umbo, 102, 103.

Ungulates, 266.

Ureter of rabbit, 249, 252.

Of snake, 201.
Urochorda, 148.
Urodela, 195.

Vacuole, 286, 292,

Contractile, 295.
Vane of feather, 208.
Veil of jellyfish, 321.
Veins of insect wing, 3.
Velum of medusa, 321.
Velvet of antlers, 274.
Ventral plates of snake, 200,
Vermiform appendix, 283.
Vertebrata, 148, 284.
Viceroy butterfly, 31.
Vinegar eel, 351.
Voice of frog, 193.

Of pigeon, 218.
Vorticella, 294.
Vulture, 235.

Waders, 230.
Walking stick, 12, 13.
Wall-eye, 171.
Warblers, 240.
Wasps, 49, 50.
Water beetles, 42.

Bug, 18.

Bulbs, of starfish, 334.

Dog, 191.

Flea, 83, 84.

Moccasin, 203.

Snakes, 200.

Tubes of sea urchin, 340.

Tubes of starfish, 332, 333.
Wax of bees, 47.
Weasels, 282.
Weevils, 40, 41.
Whalebone, 265.
Whales, 265.

Index.

375

Wheat midge, 35,
Wheel animalcule, 352, 353.
Whip-poor-will, 238.
Whiskers of rabbit, 255.
White bass, 172.
Whitefish, 165, 174.
White-tail deer, 274,
Whorl of snailshell, 127.
Wild canary, 239.

Cat, 279.
Windpipe of snake, 201.
Wing of pigeon, 209.
Wireworm, 41.
Wishbone, 213.
Wolf, 279.
Wolverine, 282.
Woodchuck, 263.

Woodcock, 230.
Wood duck, 228, 229,
Woodpecker, 237.

Yellow-bellied, 238.
Worker, honey bee, 46.
Worpis, 348.

Intestinal, 351.
Wren, 240.

Yellow bass, 172.
Jacket, 49.
Perch, 171.

Zooid, 319.

Action of, 320.
Zoophytes, 319.
Zygodactyl feet, 237.

ZOOLOGY

DESCRIPTIVE AND PRACTICAL

BY
BUEL P. COLTON, A.M.

AUTHOR OF " PHYSIOLOGY, EXPERIMENTAL AND DESCRIPTIVE," " PHYSIOLOGY

ILLUSTRATED BY EXPERIMENT," "ELEMENTARY PHYSIOLOGY,"

"PRACTICAL ZOOLOGY"; AND PROFESSOR OF NATURAL

SCIENCE IN THE ILLINOIS STATE NORMAL

UNIVERSITY

Part M
PRACTICAL

D. C. HEATH & CO., PUBLISHERS
BOSTON NEW YORK CHICAGO

•*If you study Nature indoors, when you go outdoors
you cannot find her." — Agassiz,

" He is a good naturalist who knows his own
parish thoroughly." — Kingsley.

Copyright, 1886 and 1903,

BV BUEL P. COLTON.

2d4

Printed in U.S. A

PREFACE.

The principal change from the earlier edition consists in the
addition of directions for field study and for the laboratory
study of the live animals. In the nature of the work these
directions must be somewhat general, and should be modified
by the teacher to suit local conditions and the requirements of
tne class. Because of the fact that conditions greatly vary in
different localities, it is not to be supposed that each teacher
can accomplish all the work here outlined. It is hoped that
there is variety enough to suit most localities. Other types
may often serve the purpose better than these here presented.
The work must also be adapted to the age and experience of
the students and to the time allotted to the subject. The
author's reasons for the order of study here presented are given
in the preface of the descriptive part of the book.

For convenience, the practical part follows the descriptive
text, but, of course, the actual study of the types should precede
any assigned lesson or reading in reference books.

The " Suggestions to the Student " have been entirely re-
written.

The " Suggestions to the Teacher " have become so extended
that they are no longer included in the book, but are printed in
a separate pamphlet, which can be obtained of the publishers.
In this pamphlet are hints as to laboratory equipment, class-
room management, notes and drawings, supervision of dissec-
tion, collecting outfit, field work, preservation of material, etc.

A full-pa^e cut of the microscope has been introduced to
accompany the directions for its manipulation. The author
takes this occasion to thank the firm of Bausch and Lomb for

B

IV Preface.

their kindness in furnishing the electro for this cut. A few
other cuts are added to illustrate the work of dissecting.

The importance of the actual study of types cannot be too
strongly urged. Without some real knowledge derived from
his own observation, the student has no foundation on which
to build the structure of information that he gets from reading
and from lectures. To a few fixed facts of experience he can
firmly fasten that which he acquires through the experience of
others, but which would otherwise be vague and fleeting.

The earlier edition of the author's " Practical Zoology " was
corrected by the late Professor Alpheus Hyatt of the Boston
Society of Natural History ; President David Starr Jordan of
Leland Stanford, Jr., University; Professor N. S. Shaler, Har-
vard University; Professor H. Garman, State College of Ken-
tucky; Mr. B. H. Van Vleck; Mr. J. Y. Bergen, Jr., of the
English High School, Boston ; Professor R. E. Call ; Mr. E. P.
Jackson, Boston Latin School ; and Professor L. M. Under-
wood, Columbia University.

The proofs of this edition have been critically read by Pro-
fessors M. F. Arey, State Normal School, Cedar Falls, la. ;
A. C. Boyden, State Normal School, Bridgewater, Mass. ; M. J.
Elrod, University of Montana ; J. W. Folsom, University of
IlHnois ; H. Garman, State College of Kentucky ; W. S. Jack-
man, University of Chicago; H. S. Jennings, University of
Michigan; J. M. Johnson, Peter Cooper High School, New
York; S. J. Hunter, University of Kansas; Louis Murbach,
Detroit High School; Frank Smith, University of Illinois;
H. B. Ward, University of Nebraska.

The directions for the study of the honey-bee were written by
Mr. Charles H. Allen, Bioomington, III, High School.

To these gentlemen the author is deeply indebted, and offers
them his most sincere thanks.

CONTENTS.

PAGB

Introduction— To the Student; Use of the Microscope . , . vii

CHAPTER

I. Collection and Preservation of Insects . . . . i
II. The Grasshopper lo

III. Other Insecta 17

Cricket, Dragon Fly, Squash Bug, Butterfly, House Fly,
Beetle, Bumblebee, Ant-lion.

IV. Arachnida and Myriapoda . . . • . . , .30

Centiped, Milliped.

V. Crustacea 33

Crayfish, Sow Bug, Cyclops.

VI. Annulata 47

Earthworm.

VII. MOLLUSCA , , .54

Fresh-water Clam, Snail,

VIII. Pisces 66

Perch.

IX. Amphibia 82

Frog.

X. Reptilia 95

Snake, Turtle.

XI. AvES 104

Pigeon, Hen's Egg.

XII. Mammalia 123

Rabbit.

XIII. Mammalia {continued) . 133

Rabbit, Dissection of Heart, Head, and Kidneys; Arteries
and Veins.

VI Contents.

CHAFTBR PAGB

XIV. Mammalia {concluded^ 146

Rabbit, Nervous System, Muscles, Eye, Larynx, Skeleton.

XV. Protozoa 163

Amoeba, Paramecium, Vorticella.

XVI. PORIFERA 168

Commercial Sponge.

XVII. CCELENTERATA c, . • l?!

Hydra, Sea Anemone, Corals, Sea Fan.

XVIII. ECHINODERMATA ^ ^77

Starfish, Sea Urchin.
XIX. Trochelminthes c . . . 190

Index .... c .... c ... 191

INTRODUCTION.

TO THE STUDENT.

Class-room Notes. — You should make careful notes of all your
observations and work, both in the class room and the field.
The temporary notes may be written with a pencil in any conven-
ient notebook. The following plan, however, is recommended.
Get a pad of unruled paper, about six inches long and four inches
wide. On this, the notes and temporary drawings are to be
made, using only one side of the paper. Remove the sheets as
they are filled. Keep them in a strong manilla paper envelope,
half an inch wider and an inch shorter than the sheets. Label
the envelope " Zoology " ; or, better, have a number of envelopes
labeled with any convenient subdivisions of the subject. As
much or as little of the notes as desired may be carried. These
envelopes can be carried in the pocket, and the notes are avail-
able at short notice, and can be consulted many times where a
notebook, with all the notes of a term, would not be at hand.
A still further advantage is that any notes or drawings on the
same subject, made later, can be inserted at the right place,
which could not well be done with a regular bound notebook.
As the notes accumulate those not in immediate use may ^be
stored in larger envelopes and kept as best suits your conven-
ience. A part of the " pad " of note paper should be carried to
all class-room exercises, whether it be a laboratory exercise or a
recitation, to take any needed notes. Record should be made
of all animals studied, whether those given to students for de-
tailed examination or dissection, or the exhibition specimens
brought in from day to day. Many statements made by teacher

viii Introduction.

or fellow-pupil are worth copying in the notes. Notes should also
be made of your reading about the animals that are brought in.

Field Notes. — For field notes a well-bound notebook is usually
better. It should be leather-covered and smaller than the class-
room note paper. In this book you should make record of your
outdoor observations. In the directions for " Field Study " are
many questions for you to answer. It is to be hoped that you
will ask many other questions and record your answers. If
you can give no immediate answer, do not give it up. Keep on
looking and keep on thinking. Your " field notes," " outdoor
study," " Saturday book," or whatever you choose to call it,
should be your constant companion. If the book has not a loop
to hold a pencil, see to it that you have two or three short stubs
of pencil in your pockets.

Equipment for Field Work. — Suggestions will be found in
connection with the field study of insects, birds, etc. But the
student should always carry a convenient lens, for there are
many specimens which ought to be examined when found.
Almost any small, compact lens of moderate power will be sufii-
cient, such as the linen-tester, which folds into very small space,
the lenses in hard rubber or metal cases, etc. The tripod lens
is rather inconvenient to carry in the field, but better than
many others for class-room work. When possible carry a field
glass. It will enable you to bring close to you many birds and
other animals that will not allow you to come close to them.
Even if your excursion is for insects, or other specimens which
you can easily approach, you do not know what opportunities
you may have to see distant specimens. The modern field
glasses, with prisms instead of lenses, are superior to those of
the old style, and in addition are very light, hardly weighing
more than ordinary opera glasses. They are, however, rather
expensive. Common opera glasses serve very well for all the
ordinary purposes of studying birds.

Permanent Notes. — The permanent notes should be written
with ink on ruled paper ten inches long by eight inches wide.

Introduction. ix

The paper should be ruled on both sides, with ruled marginal
spaces, an inch on one edge and an inch and a half on the
other ; the wider margin should be perforated for binding. For
the drawings, good, unruled paper with the same marginal lines
and perforations should be used. Pads of these two kinds of
paper, with labeled covers, are furnished by school-supply
dealers. This system allows any desired arrangement of the
notes and drawings, irrespective of the time when they were
made. They may also be put together temporarily in any way
desired. When you hand in to your teacher any detached
papers, write your name and the date on the perforated margin,
where it will not mar the completed notes. On the cover
should appear the subject, your name, the name of the school,
and the date. Brief marginal headings are often helpful, to
yourself as well as to your teacher. The permanent notes are
usually to be derived from the temporary notes " revised and
enlarged." They should be in your own words, and your very
best language should be used. The notes should be not only
accurate, but they should be interesting. Avoid long-drawn
sentences. Brevity is the soul of wisdom as well as of wit.

Drawings. — These should first be made in pencil. Have a
medium hard pencil and keep it sharp. Avoid shading, but
make outline drawings. Make the first lines faint, and then, if
they suit you, that is if they conform to the thing itself, go over
them again and make them heavier. Make no line or mark that
does not correspond to something you see in your specimen.
Proceed slowly, and whenever you are dissatisfied erase the line,
using the kneaded rubber eraser. Do not abandon the drawing
to begin another; keep "doctoring" the drawing with which
you start. Often it is desirable to make some feature more dis-
tinct than it appears in the specimen itself. For instance, in
representing the back of a bug or a beetle, the mode of over-
lapping of the wings is the important fact to be brought out.
But the line of union or of overlapping may be decidedly indis-
tinct, whereas some ridge that is of no significance may be

X Introduction.

prominent. Bring out the important features ; often ignore
features that are of no significance. Drawing should show
structure rather than mere appearance. Represent things not
so much as they appear, but rather as they really are. To make
the suggestions more definite, suppose you are to make a draw-
ing of the perch. Prop the fish up so you get a square view of
its left side. In the first place the drawing should be of good
size, so there will be room to put in details without having them
crowded. About eight inches will be a good size to place
lengthwise on the drawing paper. It is better to make the orig-
inal drawing of the same size you wish for the finished drawing.
Determine the place of the drawing on the sheet, leaving about
equal space at each end, and with the drawing .a little above the
middle, as the general label should always be beneath the draw-
ing. First draw a straight line for the longitudinal axis. Next
determine where the greatest depth of the fish is, and draw a
line, the transverse axis, at right angles to the main axis. Note
carefully whether or not the transverse axis is divided into two
equal parts by the longitudinal axis, i.e. whether the body of the
fish is more above or more below the main axis. Having these
points located, proceed to draw the outlines of the fish, watching
closely to see that you get the right proportions. Go no faster
than you can give satisfaction to your own criticism. After com-
pleting the general outline, draw the lateral line. Then make a
dot for the hindmost tip of the gill cover, which marks the pos-
terior end of the head. Proceed to put in the details of the
head, the parts of the gill cover, the mouth, the eye, etc. In
drawing the mouth, show it as it is and be careful not to be
guided by any preconceived notions of it. Block out and then
fill in the different fins. Unless you have an abundance of
time, do not attempt to represent the scales, and it is not essen-
tial to show the colors.

When the above features are satisfactory to you as drawn in
pencil, proceed to trace over the lines with ink. This is not so
easy, as you cannot readily erase. Have confidence in the

Introduction. xi

steadiness of your hand and you will probably get along all
right. Use a good, black drawing ink, and a clean, fine-pointed
pen. Trace from left to right, drawing the pen slanting well
back so it will slide easily. Work always on the " out curve," —
i.e. supposing the drawing is right side up, begin at the head
and trace the outline of the back ; when you have reached the
tail, turn the drawing upside down, and trace the ventral mar-
gin, beginning with the tail end. By this method you will always
be making an easy curve, with the elbow as the center of the
curve. Follow this plan wherever there is a curved line, always
turning the drawing so that the concave side of the curve is
toward you. Try to give an even, steady motion. Whenever
possible avoid going over the line a second time with the pen.
If necessary to trace over, or especially if you stop to re-ink,
begin a little back of where you stopped, in order to make the
line smooth and even. If you attempt to trace by pushing the
pen, or even by drawing it sidewise, it may occasionally " stick
and sputter " ; drawing the pen lengthwise, as above suggested,
seldom makes any such trouble.

Now comes the labeling. Place the label on each part, or
very close to it. Never letter, or number, the parts, with ex-
planations below. This method is wasteful of time and eye-
sight. Plan the labeling carefully before you begin. Do not
make the labels crowded in one part and scattered in another if
you can distribute them more evenly. Avoid drawing a dotted
line across one organ to the one designated. Organs near the
margin may well be labeled outside, using dotted lines if neces-
sary. Organs far from the outside are best labeled on the organ
itself in the most available place. Print all labels, using the
gothic type, that is, without crosses at the ends of the lines. To
insure uniformity in the letters make parallel guide lines with
the pencil ; then letter with pencil ; after tracing the letters
with ink, erase the guide lines. The general label, below,
should be larger than the detail labels. See the cut of the perch
as an example of labeling.

xH Introduction.

If water-color drawings are to be made, first draw the outlines
in black ink. After this is dry, paint in the water color. Do
not use colored pencil crayons. Only solid organs, such as the
liver, should be represented in solid color. Hollow organs,
such as the digestive tube, should be represented in outline to
show that they are open. The following colors may be taken
to represent the different systems : arteries, red ; veins, blue ;
digestive tube, brown ; liver, green ; kidneys, purple ; lungs,
pink; nervous system, gray; reproductive glands, orange.

Do not be discouraged if your first drawings do not satisfy
you. Drawing requires time and patience. Without these even
the most gifted artist produces nothing worthy. The majority
of students say at first, " I can't draw." After some sugges-
tions, and a little practice, almost every one can show creditable
results. The first thing is to see clearly. See each line in the
specimen, and make each mark in'your mind, before you put it
on paper. In such simple drawings as are here required, failure
to draw well, after a little experience, usually indicates failure to
see well. It is more head work than hand work. Perhaps the
best definition of drawing is that given by the little girl who said
" drawing is thinking, and then marking around the think."

Dissecting. — The instruments needed are : a pair of scissors,
a pair of forceps with roughened tips that will hold objects
securely, a scalpel, a cartilage knife, a blowpipe, two dissecting
needles, and a lens. The needles may be made by thrusting the
eye end of a strong needle into a wooden handle. These in-
struments are usually sold in sets in a convenient carrying case ;
the cloth-lined leatherette cases are more compact than the
wooden boxes. The cutting instruments should be kept sharp,
for which a small oilstone is desirable. Often the reason why
scissors do not cut is because they are loose at the joint. They
should sharply snip a hair, or thin paper, at the very tip of the
blades. Avoid straining the scissors by trying to cut tough or
hard objects near the tip ; cut such things near the joint. Use
the cartilage knife for the rougher work, where you are likely to

Introduction. xili

strike bone ; keep the scalpel for the finer work. Be careful to
keep the joint of the scissors dry. Do not get blood in it while
dissecting, nor water when cleaning. If the joint is kept well
oiled, watery liquids are usually kept out. Always clean the in-
struments after dissecting, using no more water than is needed ;
often a moist cloth will be sufficient. See that they are dry
before you put them away. If they are to remain unused for
some time, rub them with an oiled rag, or slightly smear them
with vaseline.

The scissors should be used much more than the beginner
would suppose. All small objects and especially thin mem-
branes are better cut with the scissors than with the scalpel, for
the reason that each blade of the scissors holds the object for
the other blade, whereas the knife tends to push out of the
way the object to be cut, and often leads to the cutting of under-
lying tissues that should be left uninjured. While cutting with
one hand, whether with scalpel or scissors, always use the for-
ceps in the other hand to steady the object, and especially to
hold the edge while cutting any thin membrane. This is
especially necessary when cutting through the wall into any cavity.
Hold the forceps as you would a pen, and not as a pair of
tongs. Delicacy and not strength is required. By holding
the forceps as you would a pen, you keep the wrist down in a
restful position, and can often let it rest on the edge of the dis-
secting pan ; your hand is thus less likely to be in your light.
Do not touch objects with a blade of a cutting instrument unless
you intend to cut them. If you wish to push an organ aside,
or turn it over, use the fingers, forceps, or the handle of the
scalpel. In much of the dissecting the handle of the scalpel
should be used, chisel-fashion, scraping and pushing, rather
than cutting. In fact, the handle of the scalpel should be used
more than the blade. Many tissues are tough and will stand
dragging or tearing, whereas a slight cut will cause bleeding
enough to interfere seriously with the work, not only making
the work unsightly, but obscuring the view. This is especially

XIV Introduction.

true of such delicate tissues as that of the liver. The blowpipe
should be used to inflate thin-walled tubes and cavities. It is
also useful as a probe. A piece of copper wire, or an aluminum
hairpin straightened out and tipped with sealing wax, serves
well as a probe. For tracing very slender ducts use a bristle
tipped with a very small drop of sealing wax. When dissecting
specimens under water do not lift the specimen out to see any-
thing. The soft tissues sink down together in a mass that pre-
vents seeing as well as before, whereas while under water they
are partly floated up and thus made more distinct. It may be
necessary, however, occasionally to lift the specimen from the
water to make a cut near the ends, or to make some new adjust-
ment, as inflating through the mouth. Always follow directions
closely when dissecting. By not doing so you are likely to
waste both time and material. Read the whole sentence before
making a new cut. It is a good rule not to cut anything unless
you know what it is. Keep your thinker just ahead of your
cutter. If in doubt, ask help of your teacher.

General Suggestions. — Arrange your table, and your position,
so as to get enough, but not too much, light. If two work to-
gether, be careful not to let the heads or hands shut out needed
light. At the beginning of the term learn the rules regulating
the laboratory, and carefully observe them. But whatever the
rules, be sure and keep your own table neat and clean. If other
students use the same table, put away all your belongings. If
you have the exclusive use of it, keep books, instruments, etc.,
in order. Take pride in making your notes and drawings the
best possible. The book is yours to keep, and, if well done,
will likely be useful to you later. It is a worthy ambition to
desire to excel. In all your work, thi7ik about what you are
doing. Do not let yourself drift along thoughtlessly. No work
succeeds without live interest in it, and thoughtful attention.
Try to think out the use of each part or organ, the ways in
which the animal is adapted to its place of living and to all its
surroundings. This habit of thinking about the things you are

introduction, xv

working over will fill them with an interesting meaning, and the
work will cease to be drudgery and become a source of increasing
entertainment.

Books of Reference.

1. The American Natural History, Hornaday.

2. Riverside Natural History, Kingsley.

3. A Manual for the Study of Insects, Comstock.

4. Key to the Birds of North America, Coues.

5. Manual of the Vertebrates, Jordan.

6. A Naturalist's Rambles about Home, Abbott.

7. Animal Life, Jordan and Kellogg.

The first five of these should be used for reference. Each student ought to
read the last two.

USE OF THE MICROSCOPE.

General Rules. — i. Do not touch lenses, nor allow them
to touch anything. 2. Keep the instrument away from dust.
3. If dust gets on a lens blow off as much as you can and
then wipe with chamois skin, or clean soft cloth, such as old
linen. Handle the microscope by the pillar below the stage.

Setting up a Microscope. — The eyepiece should slip easily
into place by its own weight. To attach an objective, first run
the tube up by the coarse adjustment, till the lower end of the
tube is two or three inches from the stage. Then hold the ob-
jective with the thumb and finger of one hand while the other
hand screws it to place. See that the threads catch fairly ; do
not use force or you may ruin the threads. Take care not to
touch the lens.

Use of a Low-power Objective. — Place on the stage a slide
holding a mounted preparation. Slip the ends of the slide
under the clips. Place the specimen over the center of the
hole in the stage. Turn the mirror so that it throws light
through the hole upon the mounted object. Lower your head
to the level of the stage and watch while running the tube down
by the coarse adjustment ; stop when the objective is a quarter
of an inch from the glass slide. Take hold of the milled head

XVI

Introduction,

Introduction. xvu

of the coarse adjustment ; look through the eyepiece and slowly
raise the tube until you see the object distinctly. Move the
slide till the object, or the part you wish to exarnine, is in
the center of the field of view. Now use the fine adjustment.
Never turn the milled head of the fine adjustment more than
two or three turns in either direction.

Use of a High-power Objective. — Begin as with the use of a
low-power objective. Lower the tube until the objective almost
touches the cover glass, watching closely with your head
down on a level with the stage. Look through the eyepiece ; by
means of the coarse adjustment, slowly raise the tube till the
object comes into view. Then use the fine adjustment till the
outlines become sharp and distinct. Be very careful not to run
the objective against the cover glass. If you do this, you may
ruin the preparation and injure the lens.

The Diaphragm. — Use an opening in the diaphragm of about
the same size as the front lens of the objective.

Use of the Eyes. — Always keep both eyes open when using a
microscope. This may be a little confusing at first, but you will
soon learn to ignore what the other eye sees.

Read " Practical Methods in Microscopy," Clark (D. C
Heath & Co.).

Parts of a Microscope.

A. Base. J. Coarse adjustment.

B. Pillar. K. Milled head of coarse adjustment.

C. Arm. L. Micrometer screw of fine adjustment.

D. Body. M. Stage.

E. Nose piece. N. Qips.

F. Objective. O. Mirror.

G. Eyepiece, P. Mirror bar.
H. Draw tube. Q. Substage.
I. Collar. S. Diaphragm.

ZOOLOGY: DESCRIPTIVE AND
PRACTICAL.

>>K«

PART II. PRACTICAL,

CHAPTER I.
COLLECTING INSECTS.

Apparatus. — i. Killing Bottle. Get a wide-mouthed bottle,
two or three inches wide and five or six inches high, with a good,
sound cork which fits well ; half a pint of plaster of Paris ; and
a lump of cyanide of potassium, about an inch square and half
an inch thick, though the equivalent of this in smaller pieces serves
as well or even better. In handling the cyanide of potassium
great care must be observed, for it is a violent poison ; not only
is it a stomach poison and a blood poison, but even its fumes
are poisonous. It is much safer to handle it with forceps, or, if
these are not at hand, pick it up with a piece of paper. Lay the
pieces of cyanide of potassium in the bottom of the bottle, and
pour in just enough water to cover them ; then sift in plaster of
Paris till the water is all taken up. The bottle should be left
ancorked for a few hours ; during this time it should be set away
where it can harm no one, for the poisonous fumes will escape.
If any loose plaster of Paris remains, empty it out ; cork the bottle
tightly. It should be labeled " poison " and kept out of reach
of children. Such a bottle is usually called a *' cyanide bottle."

Insects may also be killed by chloroform, by putting a few
drops into a bottle with the insect. This method is desirable fox

I

2 Practical Zoology.

moths and butterflies, which often become damaged in a cyanide
bottle. A drop or two of gasoline placed on the thorax and
abdomen of an insect will usually kill it quickly and not injure it.
Hard-bodied insects, such as beetles, may be dropped at once
into weak alcohol ; but this would not do for delicate insects, such
as butterflies.

Many insects may be captured directly in the bottle ; especially
is this convenient when insects are found on leaves and flowers.
Bring the bottle up under the insect with one hand ; with the
cork in the other hand quickly push the insect into the bottle.
This is very desirable in capturing bees or other stinging insects,
ill-smeUing bugs, bHster beetles, etc.

2. Insect Net. Get a light wooden handle about three feet
long, and the same length of No. 8 brass wire. Bend the wire
into a circle about ten inches in diameter, cross the ends, and
bend them so that after crossing they will extend alongside the
handle. Bend each end at a right angle, so it may be driven into
the handle to keep it from slipping ofl". Cut a notch in the end
of the handle, fit the ring to it, and bind it on firmly with fine
wire. The common error is to get too long and heavy a handle.
A light, quick swing will secure more insects than a long reach.
A piece of cane pole would be excellent if a ferrule were made to
fit over the end; otherwise it would be hkely to spht. The
bag should be of cheese cloth or Swiss, about eighteen inches
deep and rounded at the bottom. The net is likely to become
frayed out along the ring, from striking over bushes ; hence it is
best to sew a strip of strong muslin along the ring, and then sew
the bag to this strip. When a flying insect, such as a butterfly, is
caught, the net should be thrown over to one side by a quick turn
of the wrist, so the insect cannot escape. Often the collector is
more successful if, instead of running down a butterfly, he watches
it till it lights, and then quietly claps the net over it. After the
insect is caught in the net, the bottle, uncorked, may be pushed
into the net and around the insect, or the insect pushed into the
bottle by means of the cork. Many specimens may be obtained

Collecting Insects. 3

Dy sweeping the net along over the top of the grass and over the
tops of bushes, even where no insects are seen.

3. Boxes. The collector should also carry an extra bottle or a box
or two, into which insects may be put after they have been killed.
This makes room for new insects in the cyanide bottle, and keeps
them better, as the newly introduced specimens sometimes strug-
gle and may injure other specimens. Baking-powder cans and
cocoa boxes are very convenient. A shallow cigar box is good
for butterflies, as they may be pinned to the bottom so they will
not slip about and be injured.

4. Shell Bag. For carrying the above apparatus, the most con-
venient thing is what is known as a shell bag. It is of strong
canvas, and provided with a good shoulder strap. Ordinary
pockets do not serve well for all the needed material. While the
net is in use, the bottle and the boxes may all be safely held in
the bag and out of the way of the arms and hands. The common
" schoolbook bag " may be used, but they are often very weak,
and likely to give way when one is forcing his way through weeds
and bushes, and may be lost without being noticed. A good
shell bag will last almost a lifetime for this work.

General Suggestions on Collecting. — For most insects the best
time is in the middle part of a bright, warm day, for insects are
most active in warm weather. But one should not neglect col-
lecting on dark or cold days. At such times one may learn where
insects hide. Not only the places where insects hide, but their
colors and positions should be carefully noted, as these help to
conceal them. Turn over boards, stones, and pieces of bark;
pry off pieces of loose bark from logs and stumps ; kick to pieces
rotten stumps ; and look into the crevices in fences, and about
porches, etc., for insects in hiding. Careful work will secure many
specimens on days when almost no insects are seen moving, and
when the casual observer would say that there are none to be
found. Butterflies are well kept in a fold of paper as follows :
Take a piece of paper two inches longer than wide ; three and a
half by five and a half inches is large enough for most specimens.

4 Practical Zoology.

Fold the paper diagonally, with about an inch of each end
projecting ; drop the butterfly in, and fold the edges over to keep
it from slipping out. This may safely be carried in a box, a
pocketbook, notebook, or inside the sweat band of the hat. If
one catches an insect, with no other way of carrying it, it may be
pinned into the crown of the hat on the inside ; here is room for
it, and no one will be likely to notice the projecting tip of the pin.
An umbrella may be very useful in collecting. Hold the umbrella
spread and inverted under the branches of shrubs and trees, and
beat the branches with a stick, or jerk them with the handle, if it
has a hook.

Collecting by Artificial Light. — A lamp at a window, as when
studying, often brings valuable specimens. Electric lights along
the streets draw swarms of insects. It will pay the collector
to visit a number of lamps during the evening. Early in the
morning one may find some specimens, though many will have
flown or crawled away, and some may have been ruined by being
trampled upon.

Sugaring. — Many moths fly only at night. A favorite method
of capturing these is to make a thick sirup of brown sugar ; daub
this on the bark of trees, then visit these places to catch the
moths feeding on the sweet bait. The collector sets a series of
these baits, as a trapper sets a " Hne " of traps, and visits them in
series. A lantern should be carried ; the ordinary lantern serves
about as well as a dark lantern. Sometimes the bottle can be put
over the moth before it attempts to escape. In this way some
of the finest night moths are taken, and of kinds that are rarely
seen in the daytime.

Breeding Cages. — All the foregoing modes of capture are
likely to injure the specimens. The surest way to get perfect speci-
mens is to rear them. For this one may gather the cocoons and
keep them till the insects emerge. Better still, get the larvae,
keep them and supply them with food till they spin their cocoons,
or go into the pupa stage ; then one can be sure he knows the

Collecting Insects. 5

kind of larva from which any given adult comes. There are many
adult insects whose larval stage is unknown, or little understood.

When a caterpillar or other larva is taken, the collector should
note on what it is feeding, and it should be supplied with the
same, or very similar, food, as long as it continues to eat. If
the larva is not on any plant, but is crawling over a walk or on a
fence, it may be because it was shaken off the plant on which it
was feeding ; very often, however, the larva, when thus found, has
done eating and is seeking a convenient place to go into the pupa
stage. If so, it will not need food. It is safe to offer food in any
case.

Larvae should be kept in roomy cages. And, since many larvae
go into the soil to pass their pupa stage, it is best to provide soil
for any larva whose habits are not known. A convenient breeding
cage may be made of a starch box by sawing off about one third
of the length of the wooden cover and sliding it into the farthest
end of the top. Then set the box on end, with this covered' part
down, and fill with soil as far as the wooden cover extends. Cut
a glass cover to slide in and fill the rest of the opening ; make
a hole for ventilation and cover it with wire screen. If a larva
that does not pupate underground is reared in such a box, no
liarm will result. It is well to have several such boxes in readi-
ness for the work. A jelly tumbler serves very well as a breeding
cage for small insects. A lamp chimney may be used as a breed-
ing cage ; tie netting over the top.

PRESERVATION OF INSECTS.

Pinning. — Most insects are mounted upon a pin passed
through the center of the thorax. One third of the pin should
project above the back. Beetles are usually pinned through the
right wing cover, at such distance from the base of the wing that
the pin emerges between the second and third pairs of legs. It is
better to get regular insect pins, which are to be obtained from
dealers in naturalists' supplies. Common pins may be used, but
they are likely to rust. Medium-sized insect pins are best for

6 Practical Zoology.

most specimens (No. 4, Klager), though, if an extensive collection
is to be made, there should be an assortment of pins.

Labeling. — The name of the insect, with date and locality,
should be on a small label, on the pin about halfway between
the insect and the bottom of the box. The name of the order
or family should be at the beginning of the group, whether this
occupies a whole box or less.

Boxes. — For ordinary small collections, the common cigar boxes
are very convenient. Pupils can usually get them for nothing.
The bottom should be lined with sheet cork, or thin shces of
common corks can be fastened in at the place where the insects
are to be pinned. It is best to devote a box to each order of in-
sects, or even to families where many insects are collected. The
boxes should be labeled on the outside near one end, so that they
may be set on end on a shelf, and the label will show Hke the
title on the back of a book. A set of shelves should be made
of the right hight to accommodate the boxes as thus set on end.

Spreading Insects. — Beetles, bugs, flies, etc., are usually mounted
with the wings folded. But the wings of moths, butterflies, dragon
flies, etc., should be spread. And it is well to mount some locusts,
beetles, bugs, etc., with the wings spread, for the sake of com-
parison.

Spreading Boards. — For spreading the wings of insects, a
spreading board or setting board is used. This consists of two
strips of soft board, fastened to a base, with a groove between
them for the body of the insect, while the wings rest on the two
side strips. At the bottom of the groove there should be a strip
of cork to receive the pin. Place the insect in the groove, pinned
firmly to the cork. Then insert a pin into the wing, back of the
large veins, near the anterior border, and draw the wings forward
until the hinder borders of the two hind wings are in a straight
line. First fasten the wings in this position with narrow strips of
paper held by pins. Then place a larger piece of paper over the
wings and pin firmly. Sometimes strips of mica are used instead

Collecting Insects. 7

of paper. Sometimes strips of glass are used, the weight being
enough to hold the wings in place.

Relaxing Insects. — If insects become dry before they are
spread there is danger of breaking them. They need softening.
This is done by placing them in a moist place. They may be
placed on dry paper over wet sand ; or put wet paper into a jar,
lay dry paper over this, and place the insects on the dry paper
and cap the jar tightly. In a day or two they will be relaxed so
they may be safely handled. A few drops of carbolic acid will
retard the growth of mold.

Mounting Microscopic Insects. — Minute insects, such as fleas,
or small parts of insects, such as an eye, leg, sting of a bee, etc.,
can readily be mounted and permanently preserved, ready for
examination at any time. Such material should first be placed in
alcohol. If it is soft material it should first be put into fifty per
cent alcohol, in which it should not remain more than half a day ;
then it should be transferred to seventy-five per cent alcohol for
twenty-four hours, and then kept in strong (ninety-five per cent)
alcohol till ready for mounting. Pour a small quantity of oil of
cloves into a watch glass and place the object to be mounted in it ;
this is to remove the alcohol and make it clear. Then lay it on
the center of a slide in the desired position, cover it with a drop
of Canada balsam, and lay a clean cover glass on it. Keep it on a
level surface, so the cover glass will not slip, for a few days till the
balsam has hardened. Label it at one end of the sUde and keep
in a suitable tray.

GENERAL PLAN FOR FIELD STUDY OF INSECTS.
Insects vary so greatly that no one plan of study will serve well

for all. But the following scheme will serve in a general way for

the main line of work, which must be varied to suit special cases.
Find out by direct and continuous observations in the field : —
I. Where does the insect live? On the ground? In water?

On plants? If the latter, does it stay mostly on the stem or

on the leaves?

h Practical Zoology.

2. What is its fitness for its place of living?

a. In locomotion. Does it swim, creep, walk, jump, or fly?
Or has it more than one of these modes of locomotion ? How is
it fitted for moving?

If. General form. Is it slender or stout? Rough or smooth?
Does it fold the wings when at rest, or keep them extended?
Why?

c. Color. How is its color related to that of its surroundings ?
Would some other color be as suitable for it?

3. What does it eat? What kind of mouth parts has it, and
how are they adapted for the food ? Does it eat Uttle or much ?
Does it store food, or depend on foraging daily?

4. Does the insect grow? If so, is the growth like that of other
animals ?

5. What enemies has this insect? How does it escape or
avoid them?

6. Has this insect a home ? Or any regular place to which it
resorts? Where does it stay at night ? In rough weather? Does
it work by day or at night ?

7. Does it lead a solitary life? Or is it social? If social, to
what extent is there division of labor in the community ?

8. How many kinds of insects in the community? How do
the sexes differ in appearance, structure, and habits?

9. Do they live over winter? What provision is there for the
continuation of the species? How long does an individual live?
Are the different forms equally long-lived ?

10. What are the stages of its development? Is there a meta-
morphosis, or merely an increase in size? How long is it in
reaching maturity?

11. What senses does it use in its daily round? Are these well
developed? Has it a sense of direction? Does it ever get lost?

12. If it visits plants, does it show preference for any particular
plant? Does it visit many kinds of plants? What does it get
from the plant? Does it do the plant any harm? Does it do
the plant any good?

Collecting Insects. 9

13. Can it display any colors that are ordinarily concealed?
If so, why is this ? How are such colors concealed ?

14. Does this insect resemble any insect of another group? If
there is resemblance, is u of any advantage?

15. How do insects compare with other animals in strength?

CHAPTER IL

INSECTA.

THE GRASSHOPPER.

The Parts of the Body.

(i) The foremost, or anterior, part is the fega^. (2) The
middle part is the thorax, (3) The hinder, or posterior, ringed
part is the abdomen.

THE HEAD.

1. Describe its shape and mode of attachment to the thorax.

2. The two slender projections are the feelers, or antennae.
Observe how and where they are attached to the head. Use a
lens to count the parts, or segments, of which each antenna is
composed.

3. Note the situation and shape of the eyes. Examine one of
the eyes under a microscope, using a one-inch objective ; make a
drawing of what you see. These eyes are compound, and each of
the parts is called a facet.

4. Just in front of the compound eyes look for a pair of the
simple eyes, the ocelli. Find a third ocellus on the head, using
a lens if necessary.

5. At the lower part of the front of the head is a movable flap,
the upper lip, or liibrum ; raise it with the dissecting needle. Ob-
serve how it is hinged ; cut or break it off".

6. This lays bare the true jaws, or mandibles. Examine their
black, toothed tips with a lens ; find, by prying, how they move.
Study their action in the live grasshopper, raising the labrum. Study
carefully the way in which they move, and how they are hinged ;
then remove with the forceps, and again examine thoroughly.

7. Turn now to the back of the lower part of the head; pry
back the lower lip, the labium-; carefully remove it.

10

Insecta. 1 1

8. At the base of the labium is the brown tongue.

9. Attached to the base of the labium is a pair of short, jointed
appendages, the labial palps. What is the relation between the
tongue and the labium ?

10. If the above-named parts have been carefully removed,
there will remain one pair of appendages, smaller jaws, called the
maxillae. Make out that each maxilla consists of three parts : —

a. An outer, jointed part, the maxillary palp.

b. A spoon-shaped piece covering c.

c. The brown, incurved maxilla proper. Examine with a
lens, then with forceps remove the whole maxilla, being sure to
get the basal part.

11. Cut the head off a fresh specimen ; lay it on the table and
make a careful drawing of the face, naming all the parts.

12. Draw the head as seen from the side.

THE THORAX.

1. The wide collar, or cape, back of the head is the main part
of the prothorax ; make a drawing of it as seen from the side.

2. The remainder of the thorax is formed by the union of two
parts, each bearing a pair of legs, the part to which the middle
pair of legs is attached being the mesothorax, the hinder legs aris-
ing from the metathorax. Look for the line separating these two
parts of the thorax.

3. Look just above the second pair of legs for a narrow opening,
guarded by a pair of lips, which, in the live grasshopper, keep
opening and closing; this. is a breathing pore, or spiracle. Look
for another spiracle on the soft skin under the posterior edge of
the prothorax on each side.

4. Carefully compare the prothorax, mesothorax, and meta-
thorax in size, shape, and structure.

THE WINGS.

I. Notice the position of the outer (upper or anterior) wings,
and their mode of overlapping.

12 Practical Zoology.

2. With the forceps seize one of the outer wings by its lower
edge, near the anterior end, and draw it horizontally forward, till
it makes a right angle with the body, and pin in this position.
Seize the inner wing by its lower edge near the posterior end, and
pull forward to its fullest extent, observing how it is folded ; pin
this wing as expanded, and make a drawing of both wings as thus
seen. Cut a piece of paper the same size and shape as the inner
wing, and fold it as the inner wing is folded.

3. The framework of the wings is composed of veins.

4. Compare the inner and outer wings in size, shape, color,
texture, position, and use.

THE LEGS.

1. Note their number, arrangement, and mode of attachment.

2. Study carefully one of the hind legs.

a. A short segment, near the body, is the coxa.

b. A smaller segment is the trochanter.

c. The large segment is the femur.

d. The slender segment is the tibia.

e. The remainder is the foot, or tarsus ; count its segments,
and examine thoroughly, using a lens. Examine the joint be-
tween the femur and tibia, moving the parts .back and forth.
Note, also, how these parts fit together when the leg is drawn up.
Remove a hind leg, and make a drawing showing all these parts.

3. In how many ways does the grasshopper travel? In what
order are the legs moved in walking?

4. Grasshoppers make a shrill sound (stridulation) by rubbing
the inner surfaces of the hind legs against the outer wings.

5. In what different ways does the grasshopper keep from slip-
ping when it jumps ? Remove the legs and wings ; make drawings
)f the thorax as seen from the side, from above, and from below.

THE ABDOMEN.

1. Count the abdominal rings. ^" ^

2. Observe two grooves running along the under surface of the

Insecta. 13

abdomen. The under part of the abdomen, included between
these grooves, is the sternum, the side of the abdomen is called the
pleurum, and the upper part is the tergum.

3. Just above the groove that separates the sternum from th»
pleurum is a row of small holes, the breathing pores, or spiracles ;
count them.

4. In a live specimen, watch the movements of breathing.
All insects breathe by means of a complicated system of air
tubes, the tracheae, which branch from the spiracles throughout the
body. Can the grasshopper be drowned by holding its head
under water? Connected with the air tubes, in grasshoppers and
other strong flying insects, as bees and flies, are large air sacs,
which fill with air, and are said to aid, hke balloons, in keep-
ing the insect in the air. By carefully cutting away the roof of
the abdomen, these air sacs may be seen, marked by their white
walls ; the white air tubes, or tracheae, may also be readily seen.

5. Under the bases of the wings, on the first abdominal ring, is
a pair of thin, shiny, oval membranes, the tympana, or ear-
drums. The inner surface of each tympanum is connected with
a nerve.

6. The abdomen of the female ends in four points ; in laying
the eggs these points are first pressed together, then thrust into
the ground, and then separated ; this process is repeated till a
hole is made, sometimes as deep as the abdomen is long, at the
bottom of which the eggs are deposited, passing out between the
four points, which together are called the ovipositor. The males
are smaller than the females. Draw the abdomen, as seen from
the sides, of both the male and the female. Take now an entire
specimen and draw a side view of it.

INTERNAL STRUCTURE OF THE GRASSHOPPER.

This work would better be done after the student has dissected
the crayfish. Dissect under water in the dissecting pan.

I. Get a large female grasshopper, freshly killed. Cut off the
wings, and place the specimen, back uppermost, in the dissecting

14 Practical Zoology.

pan; pin the hindermost ring of the abdomen firmly to the bottom
of the dissecting pan ; turn each hind leg outward and pin down.
With sharp, fine-pointed scissors, cut through each side of the
roof of the next to the last abdominal ring ; lift, with the forceps,
the cover of this ring ; continue to cut forward, on each side of
the abdomen, pulling the tergum upward and forward as it is
loosened. Thus carefully unroof the whole abdomen.

2. The heart is a delicate tube, running along just under the
tergum, and probably was torn away with the tergum.

3. On each side there is a row of air sacs, with their white air
tubes.

4. In the anterior part of the abdomen a mass of yellow eggs
is usually to be found ; this mass may be easily separated into two
parts, right and left, from each of which a tube, the oviduct, leads
to an opening between the parts of the ovipositor.

5. Under the eggs is the dark intestine, running lengthwise.

6. Remove the roof of the thorax ; more air sacs should be
found here. In the upper part of the thorax are the white muscles
which move the wings. Removing these muscles exposes more
of the digestive tube ; as the food is swallowed, it passes upward
into a brown tube, which soon turns backward into the thorax ; in
the prothorax, the enlargement is the crop, in which is produced
the dark liquid which the grasshopper ejects from the mouth when
held captive. The crop may be removed, spHt open, washed, and
examined under the microscope with a half- inch objective to
show the rows of hooked teeth with which it is provided. A Httle
farther back the digestive tube is surrounded by a set of double
cone-shaped pouches, which extend parallel with the main chan-
nel of the digestive tube. These are the gastric ceca. Behind
them is the stomach, followed by the intestine. The products of
digestion pass through the coatings of the digestive tube, and
mingle with the currents of blood which pass along the ventral
and lateral parts of the body.

7. The veins of the wings are air tubes, and are very different
from the veins in our bodies.

Insecta. 15

8. The nervous system of the grasshopper consists mainly of a
white cord extending along the floor of the whole body cavity. In
most of the abdominal rings the nerve cord has enlargements
called ganglions, from which nerves branch to the surrounding
parts.

THE DEVELOPMENT OF THE GRASSHOPPER.

1. Late in summer watch grasshoppers to discover the process
of laying eggs. If the eggs can be obtained, keep them till they
hatch, and watch the growth of the young.

2. Early in the season catch a number of as young grasshoppers
as you can find ; cage and feed them, and watch their growth.
What changes take place during development?

GRASSHOPPER CARD.

Take a card six inches by four. Make a faint mark length-
wise in the middle to aid in placing the parts symmetrically.
Separate the parts of the grasshopper, and place them on the
card in their proper order. Before beginning, plan the whole
arrangement. First, cut off the head ; leaving a central place for
the head, remove the mouth parts, pasting each to the card as it
is removed. In separating the parts use the forceps, being care-
ful to get hold of the very base of each piece ; then, holding each
part with the forceps, dip the side that is to go next to the paper
into the glue, and carefully place just where it is to stay. This
method avoids smearing the card. Avoid getting too much glue.
The mouth parts should surround the head ; the wings should be
opposite the parts to which they were attached, as also the legs.
The legs should be separated to show all the segments; the
thorax should be separated into its parts, but the abdomen would
better be kept entire. As the parts become very brittle when
dry, it is well, if the card is to be kept, to make a little bridge of
a slip of paper, on which to string the rings of the thorax and
abdomen. The soft parts should, of course, be removed. To
presenre the card, place it in a shallow box and fasten it to the

1 6 Practical Zoology.

bottom. Perhaps the best way is to make a glass cover to the
box and then seal it, dust and moth proof, by means of passe
partout binding.

Topics for Reports. — The Rocky Mountain Locust Scourge.
Cockroaches. The Mole Cricket. Walking Sticks. Katydids.
The Praying Mantis.

CHAPTER III.

INSECT A {Continued),

THE CRICKET.

1. In what respects are the cricket and grasshopper alike?

2. In what respects do they differ?

3. The female cricket has a long, slender ovipositor. Compare
its parts with the parts of the grasshopper's ovipositor, picking
them apart with a dissecting needle. Use a lens.

4. A pair of tapering, jointed projections from the abdomen
are the stylets. Of what use are the stylets ?

5. Compare the wings of the male and female. Look on the
under surface of the outer wings of the male for a vein, running
crosswise, near the anterior end, which has on it a row of teeth.
By rubbing this file on the veins of the other wing, the cricket
makes its chirping noise. Watch crickets to see how the wings
are managed during this process.

6. With a lens look for the so-called hearing organ on the tibia
of each fore leg.

7. Make a drawing showing all that can be seen from above
(dorsal view), and name all the parts shown.

Grasshoppers and crickets belong to the order of insects called
Orthoptera, or straight-winged insects.

THE DRAGON FLY.

1. Compare the shape and relative size of the parts of body
with those of other insects. In some dragon flies the eyes have
as many as 12,500 facets each.

2. What kind of mouth parts has the dragon fly?

17

1 8 Practical Zoology.

3. How does the dragon fly compare with other insects in
power of flight? To what bird should the dragon fly be com-
pared in its habits?

4. Has the dragon fly a sting? Is it dangerous to man in any
way?

5. Watch the dragon fly dipping the end of its abdomen into
the water to lay its eggs. Compare the ovipositor with that of the
grasshopper.

6. The larva of the dragon fly is called a nymph. It may be
found on the bottoms of ponds and streams, and is very noticeable
on account of its wide head and prominent eyes, wide abdomen,
and short wings.

7. When the larvae are ready to transform, they crawl up out of
the water, their skins spUt along the back, and the adult dragon
flies escape, leaving their dry, empty skins, which may be found
clinging to the stems of water plants, projecting logs, or rocks.

8. Draw a dorsal view.

9. The dragon fly belongs to the order Odonata, or nerve-winged
insects.

THE SQUASH BUG.

1. Find the sucking tube bent back under the thorax.

2. Are there both simple and compound eyes?

3. What peculiarities of the prothorax?

4. Draw a dorsal view, showing how the wings overlap.

5. Fasten the squash bug's wings out at right angles to the
body, and make another drawing, showing how the outer wings
appear when extended, and how the inner wings are disposed.

6. Draw a ventral view.

Look for eggs. Compare young and old squash bugs. Squash
bugs belong to the order Hemiptera, or half-winged insects. What
is the propriety of this name? Insects belonging to this order
are the only ones that are properly called "bugs."

Topics for Reports. — The Periodical Cicada. Plant lice. The
Cochineal Insect. Scale Insects. The Chinch Bug.

Insecta. 19

THE BUTTERFLY.

The large brown monarch butterfly, or " milkweed butterfly,"
with dark markings along the veins of the wings, is a good one
to study.

1. Notice the position of the eyes, and their relative size.

2. Where are the antennae attached? Compare with those of
the grasshopper.

3. The short projections in front of the head are the labial palps.

4. Between the palps is the coiled sucking tube ; uncoil, and
examine it.

5. The wings : —

(a) Their shape and their mode of overlapping.

(^) The dark, shiny veins ; where are they strongest ?

{c) Scrape sdme of the scales ofl" a wing ; examine under a
high power of the microscope, making drawings.

(d) Examine with a low power of the microscope a piece
of a wing, with the scales on it, to see how they are attached and
arranged. Look at a part of the wing where the scales have been
removed.

6. Spread the wings of a butterfly, and draw them as seen
from above.

7. Examine the legs, and compare their use in this insect and
others.

8. Make a drawing of the butterfly as seen when at rest, nam-
ing all the parts visible.

9. Compare the colors and markings of the upper and lower
surfaces of the wings.

10. Carefully compare a moth and a butterfly.

11. Butterflies and moths belong to the order Lepidoptera, or
scaly-winged insects.

The orders of insects are divided into families ; this butterfly
belongs to the family Nymphalidae.

Families are divided into genera; this butterfly belongs to the
genus Anosia.

30 Practical Zoology.

Genera are divided into species ; this species is plexippus. So
his butterfly belongs to the class, Insecta; order, Lepidoptera;
amily, Nymphalidae ; genus, Anosia ; species, plexippus.

The males are distinguished by an elevated black spot on one
Df the veins, near the middle of the hind wings.
. Where is this butterfly found most abundantly ?

Development of the Cabbage Butterfly.

The cabbage butterfly is small, yellowish beneath, paler above,
with black tips to the anterior wings. The male has one round
black spot only on each upper wing, while the female has two, and
sometimes three.

1. Open the abdomen and look for eggs. They are yellow,
oval bodies, ribbed lengthwise, with cross markings on the ridges,
resembling stunted ears of yellow corn. Look also for these eggs
on cabbage leaves, or where the butterflies are seen hovering.
Watch the butterflies closely as they hght on the cabbage leaves,
to see the egg deposited on the leaf; on which side of the leaf
are the eggs usually laid ? How are they fastened to the leaf ?
Make a drawing of the egg as found attached to the leaf.

2. Get a chalk box with a sliding cover ; substitute a glass cover
a little longer than the box. Keep the box on end, so that the
door will keep closed, yet may be easily opened. Put into this
box a cabbage leaf with eggs on it ; examine several times a day.
What becomes of the egg ? In another box, similarly arranged,
put some large cabbage worms; give them fresh leaves every
day, and keep the box in a light, well-ventilated room. Watch
closely, and keep record of the date of the beginning of the
experiment, and note the date of any change ; describe carefully
all actions and changes in the worms. Make careful drawings of
each stage of growth : —

{a) The egg.

{d) The larva, at different stages of growth ; keep one worm
in a cage by itself, and make a drawing every third day.
{c) The pupa, showing how it is suspended.

Insecta. 21

{d) The perfect butterfly.

3. The cabbage butterfly belongs to the family Pieridae, genus
Pieris, species rapae.

There are several species of the genus Pieris, just as there may
be several persons in one family ; as in a directory we read ;
" Smith, Charles," " Smith, Edmund " ; so we read : Pieris rapae,
Pieris protodice.

What is the meaning of the word " rapae " ?

Occasionally a larva will fail to go through its proper changes ;
this is generally caused by some parasite, the most common of
which is an ichneumon larva. The adult of some ichneumon fly
lays it eggs on the body of the cabbage worm ; these eggs hatch
out as worms, bore into their host, and live on the juices and tissues
of the cabbage worm, till it dies from exhaustion (though the
cabbage worm often lingers, and the parasitic larvae complete their
transformation first), and the parasitic larvae become pupae, and
hatch out as perfect ichneumon flies.

Look for holes in pupae which fail to complete their transforma-
tion ; often holes may be found in them where the ichneumon flies
have made their escape. If a pupa blacker than usual be found, put
it in a vial, or pill box, and catch the ichneumon flies as they emerge.

Topics for Reports. — The Clothes Moth. The Silkworm. The
Tent Caterpillar. The Codling Moth. Cecropia. Polyphemus.
Cutworms.

THE HOUSE FLY.
The Parts of the Body.

1. The head, the foremost, or anterior, part.

2. The thorax, or middle portion.

3. The abdomen, the hinder, or posterior, part.

The Head.
I. Examine the eye with a strong lens, and under a low power
of the microscope, to discern its parts or facets. What shape
have the facets?

22 Practical Zoology.

2. Cut off the head, lay it on a glass slide, and with a one-inch
objective examine the short antennae in front of the head.

3. Look on the top of the head for simple eyes.

4. With a lens examine the under part of the head to see the
tongue. How does it move? Remove it and look at it with a
one-inch objective. How is the tongue used?

The Thorax.

I. How many legs are there? To what are they attached?
How many segments has each leg?

' 2. The wings; how many are there? Back of each wing find
a short membrane, the winglet. Note the folded portion connect-
ing the wing and the winglet.

3. A little farther back are two slender stalks ending in rounded
knobs ; these are the balancers, and are considered as representing
the hinder wings found in most insects. Note the effect of re-
moving the balancers.

4. The wings describe a figure 8 in flying, and make over 300
vibrations {i.e. go up 300 times and down 300 times) in a second.

5. On each side of the thorax, just back of the head, find a
narrow opening with a yellow, liplike border; examine closely
with the aid of lens and microscope. It is a breathing pore, or
spiracle.

The Abdomen.

Are there spiracles on the abdomen? How many rings has the
abdomen? Draw the fly as seen from above (dorsal view).

The house fly lays its eggs about stables; after a day or two
the egg hatches out as a maggot, which eats voraciously and
grows rapidly ; in about a week it ceases eating, becomes dry
and brown, resembles a seed, and does not move ; from this pupa-
rium the fly emerges.' The adult fly is short-lived, tho some live
over winter. Watch the development of the egg which the flesh
fly lays on meat and dead animals. How many kinds of flies do
you know? How do they differ? How does the fly walk on the

Insecta. 23

window pane? Examine the feet? In what order does the fly
move its feet in walking? For the study of this point, take a
fly that is sluggish from cold, or from partial drowning. Do flies,
on the whole, injure man, or benefit him? FHes belong to the
order Diptera, or two-winged insects. What other insects have
but two wings ?

Topics for Reports. — The Mosquito and Disease. House Flies.
Horseflies. Botflies.

THE BEETLE.

1. What are the characters that appear peculiar at first sight?

2. Note the position and shape of the eyes.

3. The antennae, their attachment, parts, and mode of extension.

4. A small upper lip, the labrum.

5. A pair of strong jaws, the mandibles, often very large, and
projecting forward as pinchers, or " horns." How do they move ?

6. Back of these are two small jaws, the maxillae, bearing a
pair of jointed appendages, the maxillary palps.

7. Back of (posterior to) the maxillary palps is another pair of
similar appendages, the labial palps.

8. The part of the body back of the head is the prothorax.
Why not call it the thorax ?

9. Pry up the hard outer wings. How do they meet each
other ? Each outer wing is called a wing cover, or elytnim. In
what direction does the beetle move the elytra in raising them?
How are they held during flight? Do they rise vertically?

ID. How are the inner wings folded? Compare the inner and
outer wings in length and size. Cut a piece of paper of the same
shape as the inner wing, and fold it as the inner wing is folded.
How does the beetle perform the act of folding the inner wings?
Capture live beetles and watch this process.

1 1 . Make a drawing of the back, with the wings closed ; an-
other drawing, with the wings fully expanded, as in flight.

12. Count the segments of the legs. Examine each segment
closely. Seize the foot of one of the hind legs with the forceps,

24 Practical Zoology.

and pull it about in all directions, to see how many joints the leg
has, and what motions are allowed by each joint. The segment
nearest to the body is the coxa. Then come, in order, trochanter,
femur, tibia, and tarsus (foot).

13. What marks the line of division between the thorax and
abdomen ?

14. Draw a ventral view on a large scale, showing especially the
parts of the legs, and the mouth parts.

15. Watch a crawHng beetle, to see in what order the legs are
moved.

16. What can you tell of the habits of beetles? The different
kinds of beetles, and their development ? What is a grub ? Com-
pare beetles with other insects in strength. The large beetles are
good insects for dissecting, to show the internal structure. Beetles
belong to the order Coleoptera, or sheath-winged insects.

Topics for Reports. — Fireflies. Blister Beetles. The Carpet
Beetle. Water Scavenger Beetles. Whirligig Beetles. Carrion
Beetles.

THE BUMBLEBEE.

1. Find three simple eyes on the top of the head. How are
they arranged ?

2. Describe the antennae.

3. The mouth parts : —

a. A pair of true jaws.

b. The long, hairy tongue.

c. Above the tongue the two blades of the maxillae.

d. Below the tongue two thin, narrow labial palps.

The last three form a proboscis. Pick the parts asunder, and
make a drawing of the front of the head, showing all these parts.

4. How does the bee take its food ? Is the honey stored by
the bee the same as the nectar taken from the flower?

5. Compare the segments of the legs with those of the grass-
hopper. How does the bee get pollen? What does the bee do
with the pollen?

Tnsecta. 25

6. Examine the wings ; compare the front and hind wings.

7. Get a bumblebees' nest ; examine the contents of the cells,
and note the different stages of development of the young
bees.

8. The sting is a modified form of ovipositor. Near its base
are poison glands, and a sac for storing the poison. Remove a
sting with the poison sacs and examine under a low power of
a microscope.

9. How do bees compare with other insects in intelligence?

10. Ants, bees, and wasps belong to the order Hymenoptera, or
membrane-winged insects.

Topics for Reports. — Bumblebees. Wasps. Solitary bees.
Ants.

STUDY OF THE DEVELOPMENT OF THE HONEY BEE.

Through the glass sides of the hive observe the comb. The
depressions or holes in it are the cells. Find cells that are empty,
others that are partially filled with a substance whose glassy sur-
face reflects the light. These cells contain honey. Find cells
apparently empty, but which upon close observation are found to
have a small, oblong, white body at the bottom of them. These
may be seen attached by one end to the bottom of the cell near
its center. They are not as large as the head of a pin, and are
often overlooked. They are eggs. Record the date upon a small
piece of paper, and paste it on the glass opposite the cells contain-
ing eggs, and note the changes from day to day. Determine the
number of days elapsing between the time the egg was laid and
the time of hatching. Make several trials. Begin with empty
cells, and note when the eggs are laid, as some of the eggs may
have been in the cells a day or two before you found them.
Determine the length of time the young bee is in the grub or
larval stage. The larva may be seen one or two days after hatch-
ing, floating in a small drop of gray-colored liquid at the bottom
of the cell. Note its rate of growth. What care has it received ?
Has it been nursed, fed, and cared for, or has it, like Topsy,

l6 Practical Zoology.

"jest growed"? Find other cells near the brood (by brood is
meant young bees in all stages of development) which are partially
filled with a yellowish or brownish pastelike mass. This is stored
pollen, or " bee bread." Its color varies according to the kind of
flowers from which it is gathered. Now look for larvae in all
stages of development, from the smallest, which are Httle larger
than the egg from which they came, to those which almost fill the
cells they occupy, and in which the segments may be easily counted.
Find other cells each covered with a brown cap. Observe them
closely from time to time, and try to determine what they contain.
Cells near the ends and top of the brood frame, which are covered
with white caps of wax, contain honey. The caps of the latter
may appear dark if the honey touches the caps, but usually there
is an air space between the honey and the caps, and the caps
appear white. Look for both of these conditions. What changes
have you noted through a period of ten or twelve days in the cells
in which you first found eggs ? Can you now see the interior of
the cells ? Can you discover the bees placing brown caps on cells
containing the largest larvae ? If so, note the date and determine
the length of time the caps remain on them. Determine how and
by whom these caps are removed. Watch to see some of the
occupants of these cells come out. Note any difference in appear-
ance between these and older bees. If these directions have been
followed through a period of several weeks, you have observed all
of the stages of development of a honey bee, and noted the length
of time the young bee was in each stage. Which of these stages
corresponds to the caterpillar stage of a butterfly? Which to the
cocoon stage of a moth ?

Honey Bees at Work.

Watch the bees as they come and go at the entrance of the hive.
Dust a little flour upon some that are entering, and note to what
part of the comb they go. Determine, if you can, whether they
remain in the hive for some time or soon leave it again. Look for
bees coming in loaded with yellowish or brownish pellets attached

Insecta. 27

to the outside of the large segments of the hind legs. Where
and how do they unload? What are they carrying? Why do
they bring this substance ? In the latter part of the season bees
sometimes carry propolis, a sort of glue, in the manner above sug-
gested. This latter substance is used to seal cracks and crevices.
Observe that some of the bees on the comb move about from cell
to cell, putting their heads into the cells where there are larvae.
What is the work of these bees? Are they young or old bees?
What is pollen ? What is nectar ? How does honey differ from
nectar? What is beeswax? Is it gathered by the bees, or do
they make it? What difference in color between new honeycomb
and the brood comb you have just been studying? Why this
difference in color?

Study of the Structure of Honeycomb.

Obtain two pieces of empty honeycomb, one with cells the
same size as those in the brood comb in the hive, and the other
with cells somewhat larger. Note the shape of the cells. What
geometrical figure is represented by a cross section of a cell?
Why not have round or square cells instead of this form? Lay a
foot rule upon a row of cells across the face of one of the pieces
of comb. How many cells in one inch ? Make several measure-
ments to obtain an average number. The average diameter of the
cells may be expressed by what common fraction? Repeat with
the other piece of comb and compare results. For what especial
purpose do the bees use each kind ? Do they ever use both for
the same purpose ? Draw a face view of each kind of comb, being
careful to show correctly the relation of each cell to the cells
adjoining it. Cut a piece of comb so as to show a freshly exposed
edge. Note the shape of the bottom of the cell and the relation
of those on one side of the comb to those on the other. Draw an
edge view of a piece of comb, using care to show this relation.
Note the number of parts in the bottom of each cell. Shape of
each part. Make a pinhole in each part of the bottom of a cell.
Turn the comb over and find how many cells have holes in the

28 Practical Zoology.

bottom. Why this number? What new fact in regard to the
relation of the bottom of a cell to the cells on the opposite side of
the comb? Why should the bottom of a cell be of this form and
not flat ? Why this relation to the cells on the other side ?

THE ANT-LION.

Field Study of the Larva. — In dry, sandy places look for
conical depressions, as evenly made as if rimmed out by a
mechanic. Many of these pits may be found near each other, in
the neighborhood of ants' nests. Drop a few grains of sand into
the center of the pit, looking closely meanwhile, for the protruding
jaws at the bottom of the pit.

Quickly scoop up the whole pit, aiming to go an inch deeper
than its greatest depth. This can be done very well with the
hand, though a garden trowel is best. A tin cup or dipper would
serve very well. Sift the sand thus scooped up through the fingers
or over the edge of the hand, and look closely for the dull gray
larva of the ant-lion (Fig. i6). It has an oval body, and a pair
of long, hooked jaws. Place the larva on sand held in the hand,
cup, or can, and see how it buries itself.

Home Study of the Ant-lion Larva. — Take several larvae home.
Place each on sand in a separate tumbler or can. Two or three
inches deep will be enough. Watch again how the larva buries
itself. Watch patiently to find how it digs the pit. Drop an ant,
a crippled fly, or almost any small insect into the pit and see
what the larva does. How does it eat ? How much of its victim
does it consume ? For the appearance of the adult ant-lion see
Fig. 15, in the descriptive text.

REVIEW OF INSECTS.

Take any insect not yet studied, and examine it thoroughly.
Write a full description, and make drawings of it. Which of the
insects previously studied is this most like ? To what order, then,
does it probably belong ?

Insecta. 29

Select two pages in your notebook that face each other. On
the left-hand page make a list of characters common to all the
insects you have studied, numbering the points ; on the right-
hand page write briefly the characters peculiar to each insect.
The first list ought to be a very nearly correct definition of an
insect, so far as external features are concerned. The second list
should serve as a definition of each of the orders of insects.

All the orders of insects belong to the class Insecta.

Write now a list, in vertical series, of the orders of insects
studied, with the name of the insect representing that order oppo-
site it, and include all within a brace opposite the word Insecta.

Read Insect Life^ Comstock.

CHAPTER IV.
ARACHNIDA AND MYRIAPODA.

STUDY OF LIVE SPIDERS.

Spiders and Spider Webs. — Find a spider at home near you, where
you can conveniently watch it for some time each day. What is
the shape of the web? Do all spiders make the same kind of a
web? Does the same spider always make a web in the same way?
How is the web situated? Does the spider stay on the web? If
so, on what part of it? What reason for this position? If you
cannot find a spider beginning a new web, destroy a web and
watch to see if a new one is begun soon. Does the spider take
the same place for the new web ? How does it begin the work ?
Is every part kept as first made, or is any part comparable to
the scaffolding erected by the carpenter? Do spiders repair
broken places in webs? If so, how is this done? How is food
secured? Watch the whole process of capturing and eating food.
Does the capturing of the food injure the web? Are spiders
equally active at all times ? Visit a spider in the evening and see
if it is awake, and " ready for business " ? Are spiders affected by
cold ? Do they like sunshine ? Do they live over winter ? What
can you learn about the development of spiders ? Why are there
sometimes so many spider webs floating in the air? What relation
have these floating webs to the weather? Are these floating webs
of any use to spiders? How are they set afloat, and what keeps
them afloat ? Can you discover the beginning of such work ? How
and where do spiders lay their eggs? Watch the development of
the eggs.

39

Arachnida and Myriapoda. 31

External Features of the Spider.

Spiders are best preserved in alcohol, as they shrink in drying.

1. The anterior division of the body is the cephalothorax,
or united head and thorax.

2. The large posterior division is the abdomen.

3. How many legs are there? To what are they attached?
How many segments are there in each ? Examine the feet under
a microscope. Make a drawing of one of the feet. Can a spider
cHmb out of a tumbler? Compare it with the beetle in this
respect.

4. With a dissecting needle pry apart the mandibles, at the
front of the head. The duct of the poison gland opens at the
tip of each mandible.

5. Back of the mandibles find a pair of small jaws, the maxillae.

6. To the maxillae are attached a pair of jointed appendages,
resembling a pair of legs, the maxillary palps.

7. With a lens look for the simple eyes above the jaws. How
many are there, and how are they arranged ?

8. With a lens examine the spinnerets at the posterior end of
the abdomen. With a pair of forceps hold a live spider by one
leg, and watch the beginning of spinning.

9. Besides air tubes, some spiders have one or two pairs of lung
sacs, composed of several leaves, into which blood flows, and is
thus aerated.

Place the description of the spider alongside the list of charac-
ters common to insects, and note what features are common to the
spider and all the insects ; also the points wherein they differ.
Spiders belong to the class Arachnida.

Read Emerton's Spiders^ their Structure and Habits.

MYRIAPODS.

One form of " thousand legs," commonly found under stones
and under the bark of dead stumps and logs, is well known by its
cylindrical body, by its numerous, short, hairlike feet, and by its

32 Practical Zoology.

habit of coiling its body into a spiral when disturbed. This is a
milliped.

1. How many segments has the body?

2. How many appendages has each segment?

3. Make a drawing of the thousand legs.

4. What are the chief differences between this animal and
insects ?

Another common form of thousand legs is that called centiped.
It is, when full grown, about an inch long, with a broad, flat head,
a brown, shiny back, the segments being generally about the same
size, with one pair* of jointed appendages to each segment. The
antennae are many-jointed. It is found under boards and about
rubbish and manure heaps, where it feeds on insects and earth-
worms. It usually runs actively when uncovered.

1. Examine the jaws and mouth parts carefully; how many
pairs of jaws are there?

2. With a lens examine the legs. How many are there?

3. What kind of eyes are there ? How many, and how placed?

4. Arrange the legs so they can be distinctly seen, and make a
drawing as seen from above.

5. Make an enlarged drawing of the mouth parts as seen from
below.

6. What are the differences between this form and the thou-
sand legs mentioned above ?

7. In what are the two aUke? Both belong to the class Myria-
poda. Carefully compare them with the insects, and make a list
of points common to insects and myriapods ; also a list of the
characters which insects have and the myriapods do not have j
and a list of points peculiar to myriapods.

CHAPTER V.
CRUSTACEA.

STUDY OF THE LIVE CRAYFISH.
Field Study.

Where to find Crayfishes. — Look under stones in shallow
creeks, under ledges of rock, or overhanging banks of streams.
Remember that crayfishes are nocturnal and are usually hiding
during the daytime. Note all the kinds of places in which you
find them, and where they are most numerous. Are they in deep
or shallow water? In clear water or muddy? In fresh water or
foul ? In quiet water or in rapid currents ? Over mud, or gravel,
or sand ?

How they Escape. — In turning over stones or tin cans in a
stream, note closely how the crayfish escapes. Which end goes
foremost? What is the chief organ of locomotion? How is this
used ? How far does a frightened crayfish ordinarily go before
stopping, if not closely pursued? Does it stir up mud in its
flight? If so, how is this done? Does the stirring up of mud
benefit the crayfish? If the crayfish goes some distance, is the
rate of motion uniform ? Explain.

Color of the Crayfish. — Note the color of the crayfish in rela-
tion to its surroundings, especially the color of the bottom over
which it passes. Is its color an advantageous one ? What if it
had the color of a boiled crayfish? Are all crayfishes of the same
color? How account for the difference?

Crayfish Holes. — Where are these most abundant? Do they
all have "chimneys"? Is the chimney of the same color as the
surface soil? How high are the chimneys? Are these built

33

34 Practical Zoology.

during the day or during the night? How does the crayfish build
the chimney? How deep are the holes? What are they for?
Do all kinds of crayfishes dig holes ? In what part of the hole
does the crayfish stay? Are the holes used equally at all seasons?

Molted Shells. — If you find what appears to be a dead cray-
fish, examine it carefully to see whether it is really a dead animal
or only the cast-off shell. Do you find any dead ones ?

Enemies of the Crayfish. — Have you seen any animal eating or
attacking a crayfish? Or any evidences of such action?

Home Observations.

Walking. — If one has no aquarium, a dish pan or homemade
trough serves very well. Watch a crayfish crawling in the water.
What appendages are used ? Can it walk in other directions than
head foremost? Are the legs moved in regular order? Place a
crayfish on the floor. Does it walk equally well in water and out?
Why should there be a difference ?

Swimming. — Frighten a crayfish by thrusting a stick at it to
see how it swims. Study closely the parts used and their action.
Suppose a crayfish could propel itself rapidly forward, how would
the resistance compare with the resistance it meets while going
backward? Note closely the condition and position of the tail
fin while making the stroke and while darting through the water
between strokes. Observe all the points of structure that aid the
efficiency of the stroke ? What is true of the amount of resistance
in the recover stroke ? With the thumb and finger, take a cray-
fish just back of the big pinchers and hold it with the head up, so
that the tail fin is covered with water ; if it is now excited, the
effectiveness of the tail fin will be well demonstrated.

Mode of Defense. — With a stick or pencil, make motions at a
crayfish to see how it defends itself. Allow it to grasp a pencil to
show the strength of its grip. Does a crayfish prefer to fight, or
would it rather avoid an attack? In an aquarium does a crayfish

Crustacea. 35

stay in open places, or where the Hght is strongest, or does it
seek sheltered places?

Feeding. — Offer a crayfish various kinds of food, bread, meat,
cheese, vegetables, etc. Find what it prefers. Learn how it eats,
what organs are used and how they are used. Does a crayfish
eat much or little? Is it a rapid or a slow eater? Examine the
mouth parts in this connection, (In these experiments be careful
not to let the water become foul.)

The Water Currents to the Gills. — While a crayfish is at rest
in shallow water, carefully introduce a few drops of ink near the
bases of the hinder legs. Where is it drawn in and where does it
reappear? Try placing the ink at various points along the edge of
the carapace. Place a crayfish in a candy jar. Watch it from the
front and below to see the vibratory motions of the outer branches
of the maxillipeds. Their motions indicate the rate of movement
of the gill scoop, or gill paddle, within. Count the vibrations for
a minute. How is it that a crayfish, while breathing by gills, can
live so long out of water?

Senses. — Note the range of motion of the eyes. Can an
enemy approach a crayfish from any direction without being seen ?
Can a crayfish see small objects as well as large ones? Does it
notice slow motions as readily as quick ones? Does a crayfish
see where it is going when it is frightened and darts backward by
swimming?

What advantage is there in having the eyes on movable stalks?
What disadvantages? In what ways is the eye protected? Touch
one of the eyes. What follows?

With a straw, broom-straw, or feather, test the sense of touch
over all the outside of the body. Where does the crayfish seem
most sensitive to touch? Is there any special reason for having
two pairs of " feelers " ?

Which reach farther forward, the big claws or the antennae?
Can the antennae extend back as far as the tip of the tail fin ?

Make noises near the crayfish to test its sense of hearing. In

^6 Practical Zoology.

these experiments take care not to produce such vibrations of air,
water, or mud as might eifect the sense of touch.

Test the sense of smell by placing various odorous substances
near the crayfish, when in air as well as in water. Is any attention
paid to scents ?

Recall any choice of food the crayfish has made? Is this
choice determined by a sense of taste ? Place various substances
that affect your sense of taste on the crayfish's food. Does it
make any difference in his choice? Place on the mouth organs
drops of various liquids that affect your taste. Is the crayfish
affected thereby?

Molting. — Sometimes when one has left a single crayfish in an
aquarium he is surprised to find two. The molted shell looks like
a complete crayfish. Watch a crayfish closely for this change.
Before the molt a crayfish is dull and quiet. What are the first
stages of the process, and in what order does he cast off the old
shell? Feel of the newly emerged animal. For several days test
the hardness of the shell. How long does it take for a " soft-
shell " crayfish to become a *' hard-shell "? What makes the shell
hard? Drop a piece of the old shell in weak hydrochloric acid
(vinegar will serve). Hold a piece of shell in flame. Does it
burn?

Development. — Find a female crayfish with eggs. To what are
the eggs attached ? Watch till the eggs hatch out. How long
are the little crayfishes when first hatched ? Do they go free or
remain attached to the mother? If they separate from her, do
they return to her? Does she make effort to keep near them
or keep them near her? Does she feed them? What do they
eat at first? Do crayfishes ever eat each other? Do they kill
each other?

External Parts of the Crayfish.

I. Note the two distinct parts of the body, (i) the anterior,
rigid part, the cephalothoraz ; (2) the posterior, flexible part,
the abdomen.

Crustacea. 37

2. The covering of the cephalothorax is the carapace. Run-
ning across the carapace is the cervical groove. The anterior
projection of the carapace is the rostrum.

3. Bend (flex) the abdomen, and straighten (extend) it re-
peatedly, observing how the segments are jointed together, and
how they move one upon another. Count its rings or segments.

4. Separate the third ring (counting from the front) from the
rings in front of and behind it. To do this hold the cephalo-
thorax and fore part of the abdomen by the thumb and fore
finger of the left hand, with the posterior end of the abdo-
men projecting toward the right hand; then, grasping the
dissecting needle firmly with the right thumb and forefinger,
thrust the point of a dissecting needle obliquely forward between
the third and fourth segments, and work it up and down, severing
all connection between them without breaking either ; with scissors
cut the membrane between the under sides of the rings, and
entirely separate them. In like manner detach the third segment
from the second. The ring has these parts : —

a. The upper part, the tergum.

b. The under part, the sternum.

c. The side piece, the pleurum (projecting downward).

d. Two appendages, the swimmerets. (See Fig. 46.)

5. Observe that each swimmeret has a main stalk, the protopod,
and two branches, an outer, or exopod, and an inner, or endopod ;
examine these appendages thoroughly. Lay the ring on its front
side, make the branches of the swimmerets diverge enough to
appear distinct, and make a drawing of the whole ring as seen
from behind.

Compare the other segments of the abdomen with the third.

In the male the appendages of the first and second rings are
larger than those of the other segments and are specially modified.
In the female the swimmerets of the first and second abdominal
segments are smaller than the others. The abdomen of the female
is wider than that of the male, probably for the purpose of pro-
tecting the eggs and young, which are attached to the swimmeret*?

38 Practical Zoology.

6. Study carefully the structure and action of the tail fin. Its
middle piece is the telson, underneath which is the external
opening of the intestine, the anus.

Remove the telson, and without disturbing the side parts of the
tail fin, separate the sixth abdominal ring from the fifth. Now
carefully compare this (sixth) ring and its appendages with the
third ring and its appendages.

7. Are the appendages of the thorax borne upon rings Hke
those of the abdomen? If so, where are the rings? With forceps
seize the base of one of the hindmost pair of walking legs, and
move it backward and forward ; are these borne on a distinct
ring? Carefully clean the sternum between the other walking
legs, and look closely for indications of rings.

8. With the forceps break away one side of the carapace,
beginning at the lower edge. This lays bare the white, feathery
gills. Cover the specimen with water in the dissecting pan to
show the gills more clearly. Move the legs of this side back and
forth, watching the gills.

9. Study now the hindmost of the walking, or thoracic, legs.
Count its segments. Observe how the first segment is joined to
the body. Flex the leg as far as possible, in every direction,
noting the number of joints, and the motions allowed by each.
With the forceps seize the squarish, basal segment of this leg, and
pull off the leg.

10. Remove in like manner the legs in front of this, again
being careful to get a firm hold of the short, wide segment next to
the body. What is the relation between the leg and the gill
nearest to it? Lay this leg on a paper in front of the one previously
removed. In this way pull off all the legs of one side, from the hind-
most to the foremost, laying them in order. Compare them all
with the one first taken. In the legs bearing pinchers is there
any real new part added, or is the pinching apparatus produced by
some change in a part presented in all the legs? How do the
legs which bear the big claws differ from the walking legs? Com-
pare them, segment with segment.

Crustacea. J9

11. Anterior to the big legs are several pairs of appendages
surrounding the mouth. Probe between them to find the mouth.
These mouth parts are numbered fi-om the front, but on account
of the way in which they overlap, it is easier to remove and study
them in the reverse order.

12. The appendages just in front of the big claws are the hind-
most of three pairs of jaw feet, or maxillipeds. Gently raise them
to see how they cover the other mouth parts. Note that these
maxillipeds, or foot jaws, have an inner branch (endopod), which
meets the corresponding part of the opposite maxilliped, and an
outer branch (exopod). Observe that both these branches are
attached to one segment (protopod) , next to the body. Seize this
basal segment, and remove the whole maxilliped. Compare it
with one of the swimmerets of the third ring of the abdomen. In
the same way remove the second and first maxillipeds of this side,
keeping them in order. Are there gills attached to the maxilli-
peds ? Is there more than one gill on each leg ? Are there other
gills than those attached to the legs? Pick one of the gills to
pieces under water to determine its structure. After removing the
gills, look in this region for further traces of thoracic rings.

13. Anterior to the maxillipeds are two pairs of maxillae. These
are very thin, and He close to each other, so that if great care be
not taken, they are likely to be pulled off together. Investigate
closely, and then, inserting the forceps well down, remove them,
one at a time. Attached to the base of the hinder maxilla is a thin,
double spoon-shaped structure, the gill scoop, or gill paddle. It
lies in the front part of the cavity in which the gills are, the gill
chamber. With the forceps move back and forth the second
maxilla of the other side, to see how the gill scoop is thereby
moved. The gill scoop, swinging back and forth, pushes the
water out of the front end of the gill chamber. The water thus
expelled is replaced by fresh water, which comes up under the
lower edge of the carapace, about the bases of the legs ; thus the
gills are constantly bathed with water containing a fresh supply of
oxygen.

40 Practical Zoology.

14. The mandibles are short, hard, and toothed. Each mam
dible bears a jointed appendage, the mandibular palp, which
curves around the anterior edge of the mandible in a groove.
Move a mandible about to see how it is hinged.

15. Closely fitting against the posterior surface of each mandi-
ble is a thin, leaflike structure, the metastoma. The metastoma
diff'ers from the maxilla in pointing outward and in being un-
divided. Remove it and complete the series of mouth parts, —
mandible, first maxilla, second maxilla, first maxilHped, second
maxilHped, third maxilUped. Remove the corresponding append-
ages of the other side, lay them in a row facing those of the oppo-
site side as before removal, but not now overlapping each other,
and make a drawing of the series, naming them.

16. The long projections in front of the head are the antennae.
Seize one of them with the forceps, and pull about in all directions,
to make out the large segment, at its base, under the head. On
this basal segment find a small white cone, with a hole at its sum-
mit. This is the aperture of the kidney, or green gland. Remove
the antenna, with the whole of this big segment at its base. What,
probably, is the use of the bladelike branch of the antenna
just under the eye? Compare the antenna and its branches with
a swimmeret.

17. Above the antennae are the antennules.

18. In the base of each antennule, just underneath the eye, is
the ear sac.

19. With the forceps pull the eye about to see its range of
motion. Pull it out by its stalk, and examine with lens and micro-
scope its black tip, or cornea. Each distinct area is a facet, and
the eye is compound.

20. After removing the cephalothoracic appendages, and the
carapace, carefully clean and thoroly examine the framework
of the cephalothorax, still looking for traces of thoracic rings.

21. The skeleton of a crayfish, like that of insects, is an external
skeleton, or exo-skeleton. Compare it with the internal skeleton, or
endo-skeleton^ of vertebrates.

Crustacea. 41

Crayfish Card.

Get a piece of stiff, smooth cardboard six inches by eight ; select
some dark color such as will make a good background for the
crayfish. With pencil make three fine lines lengthwise, one in the
middle, the others an inch from the middle. Make a cross at
the center of the middle line. Now dot all three Hnes at intervals
of half an inch, starting from the center.

Separate the parts of a crayfish as in previous study. For this
the specimen should be slightly moist. If too dry, it will be brit-
tle. If too wet, it will stain the card. If the work is interrupted,
it is well to keep the parts on a damp paper or cloth, and covered
so they will not be scattered. The parts of a crayfish are so
compactly put together that it is impossible to see them all, while
in their natural place. One object of this work is to make a per-
manent preparation with the parts separated enough to show them
distinctly. The crayfish is supposed to be crawling along the
middle line of the card, and to have become dismembered and
strung out. The carapace is to be in the middle line, with its
hinder edge half an inch from the center of the card. The ab-
dominal rings are to follow this at intervals of half an inch. The
appendages are to be arranged along the side lines at intervals
of one half inch, with their bases at the side line, and extending at
a suitable angle forward. To support the carapace and abdominal
rings, make a cardboard bridge of the same material as the card.
This bridge should be just high enough to reach the under surface
of the arch of the carapace. The rings should be strung on this
bridge, and both the rings and the carapace sewed to the bridge at
the top, with a thread of such color as to be as inconspicuous as
possible. The ends of the bridge should be sewed to the card,
and the lower edges of both rings and carapace fastened so they
will not slip about. All needle holes through the card must be
made from above to avoid leaving a rough place. Determine
where each hole is needed, and pierce from the upper surface of
the card, whether the thread is to be passed through from above

42 Practical Zoology.

or below. In fastening the appendages, first decide just where
the part is to lie. Then, directly under the basal part, make a
hole from the upper side. Then pass the thread through, from
below, over the appendage, and down again through the same
hole. The loop thus made will hold the appendage securely and
be little noticed if the thread has a suitable color. In this way
fasten each of the longer legs at three points. Leave the eyes at-
tached to the carapace, but arrange all the other appendages, from
the antennules to the last thoracic legs. Label the whole series
on one side, placing the name below each appendage.

Dissection of the Crayfish.

1. Place the crayfish in the dissecting pan, dorsal surface up,
and cover it with water. Place a double-pointed tack astride the
narrow part of each of the first pair of thoracic legs just back of
the big pinchers. By pressing strongly with the thumb the tack
can be set firm enough to need no hammering. Now pull the
body of the crayfish back taut and tack firmly through the telson.

2. Insert the point of one blade of the scissors under the
hinder edge of the carapace, about an eighth of an inch to one
side of the middle Hne. Cut forward to the groove which sepa-
rates the head from the thorax. Break away the whole of the side
of the carapace. Push the gills downward, and cut them off at
their point of attachment. Observe the thin wall separating the
cavity in which the gills were, the gill chamber, from the body
cavity. Clear away the other side likewise.

3. With the forceps pick away the narrow remaining strip of the
carapace, carefully, as the heart lies just under it. The heart is an
oblong, whitish body. Look for small white tubes, arteries, running
forward from it toward the head. How many are there? Be on
the lookout for other arteries. With the forceps gently hft the
hinder end of the heart ; note its angularity. Look for holes in
the dorsal surface of the heart ; how many do you find ? Look also
for holes on the sides and on the ventral surface.

Crustacea. 43

4. Under the heart, and projecting in front of it, are the repro-
ductive organs : in the female, the ovary, in which the spherical
eggs may be distinguished ; in the male, the whitish spermary oc-
cupies a corresponding position. The ovary sends downward on
each side a tube, the oviduct, or egg tube, to the first segment of
the third thoracic leg, where it opens externally. The spermary
has a much longer, coiled white tube, which opens on the first
segment of the hindmost thoracic leg.

5. Carefully cut away the roof of the head. The space within
the head is almost com.pl etely occupied by the stomach, a round-
ish sac, with a thin wall, in which is a hard framework. Gently
scrape away the soft tissues around the stomach, and examine it
closely. Observe the narrow gullet or esophagus leading from the
mouth to the stomach.

6. Along the sides of the posterior end of the stomach and the
anterior end of the intestine lie the large digestive glands. They
are yellow or greenish in fresh, reddish in alcoholic, specimens.
Pick one of these masses to pieces to learn its structure. Find
the duct leading from each gland into the intestine.

7. Observe the white muscles which extend forward from the
abdpmen along each side of the body cavity.

8. Beginning at the front end of the abdomen, close to each
side, cut with scissors through the roof of the abdomen to the
telson. Seizing the forepart of this roof with the forceps, care-
fully lift it and turn it backward. A thir layer of white muscle
may adhere to it, or may remain connected with the organs in the
abdomen. This is made up of the muscles that straighten (ex-
tend) the abdomen. Pick them away carefully with the forceps.

9. Running lengthwise, in the middle line, is the intestine, a
thin-walled tube, often of a dark color from its contents. Trace
it back to the anus and forward to the stomach. Carefully re-
move the intestine.

10. A large mass of muscle remains. This is composed of the
muscles that bend (flex) the abdomen. How do these flexor
and extensor muscles compare in size ? Why the difference ?

44 Practical Zoology.

1 1. Draw the point of a knife blade or dissecting needle along
the middle line of this muscle, at the bottom of the groove in
which the intestine lay. After a thin layer has been cut through,
the whole muscle may be easily separated into two rolls the whole
length of the abdomen. Roll these carefully aside, pushing
equally right and left; otherwise the nerve cord may be injured.
Find in the middle line of the floor of the abdomen a slender
white nerve cord, with enlargements at intervals. How many of
these enlargements, ganglions, are there in the abdomen? What
relation do the ganglions have to the segments? Observe the
branches, nerves, given off to the muscles on each side. Trace
the nerve cord forward to the thorax, where it disappears in the
hard framework of the floor of the thorax. Break away as much
of this framework as is necessary to follow the cord to the head.
Make out that the cord is double. How many ganglions are
there in the thorax? Note the branches extending to the legs
and other organs. From the large ganglion back of the gullet
trace two branches forward, one on each side of the gullet, till
they unite in a large ganglion above the gullet, thus forming the
esophageal collar. From the ganglion above the gullet trace nerves
to the eyes, antennae, and antennules.

12. Cut open the stomach, wash it out with water, and look on
its inner walls for teeth.

13. Below and in front of the stomach, find a pair of pale green
bodies. These are the kidneys or " green glands." Remove the
stomach and study the structure of the kidneys. Find where they
open externally.

14. Study the joint in one of the big pinchers. Pick out the
muscle from the end of the segment, and find the thin, tough
white tendons. Seize these with the forceps and pull alternately,
to see how the claw is shut and opened. Which is larger, the
muscle that opens the claw, or the one that shuts it ? Explain.

15. In what characters is the crayfish like the grasshopper?
In what do these animals differ? Make a concise list of these
points of likeness and difference.

Crustacea. 45

1 6. Why should the name Crustacea be applied to such animals
as the crayfish ?

Read The Crayfish, Huxley.

Topics for Reports. — The Lobster Industry. Shrimps. Crabs.
Hermit Crabs. Sea Spiders. Fiddler Crabs. Cocoanut Crabs.

THE SOW BUG.

Sow bugs are usually to be found under boards and stones, and
in other damp places. Get the largest specimens for this study.

1 . The first part is the head, or carapace.

2. Find and describe the eyes.

3. What are the peculiarities of the antennae? How many?

4. The jaws and maxillae are closely pressed together, forming
a short, blunt projection under the head. The tip of this blunt
proboscis is usually black. A longitudinal groove shows the line
of union of the hinder maxillae. By pinching the body of a live
sow bug, the mouth is sometimes more clearly shown by the
exudation of a liquid, as in the case of a grasshopper.

Where is the fine of division between the head and thorax?
Count the appendages which may be supposed to belong to the
head ; how many rings do these indicate?

5. The fine of division between the thorax and abdomen is
indicated by an abrupt change in the size of the segments. How
many segments has the thorax? Compare the numbers of seg-
ments in thorax and abdomen with those of the crayfish.

6. How many segments are there in the abdomen ?

7. How many pairs of legs are there? How many segments
has each leg ? Do the legs all extend in the same direction ?

8. A series of thin, overlapping plates under the abdomen are
the gills. In the anterior plates observe the white air chambers.
Beginning at the foremost of these gills, pick them apart with a
needle. Remove them, and with a lens make out their shape and
arrangement.

9. Under the thorax of the female there is a series of thin
membranes attached near the bases of the legs. These are the

46 Practical Zoology.

egg covers. The eggs, after being expelled from the body,
undergo their development in the space under the thorax in-
closed by these egg-covers. Look for specimens carrying iggs in
this manner.

10. In what respect are the sow bug and crayfish ahke? In
what respect do they differ from each other?

The crayfish and sow bug both belong to the Crustacea. The
class Crustacea is divided into several orders. The order to
which the crayfish belongs is the Decapoda, or ten-footed ; the
sow bug belongs to the order Tetradecapoda, or fourteen-footed.

CYCLOPS.

Along the sides of aquaria, and sometimes in drinking water,
there may be seen minute white animals swimming with a jerky
motion. Cyclops has a pear-shaped body, and is just large
enough to be seen readily with the naked eye. The females carry
two egg masses attached to the sides of the abdomen. With a
lens, watch these animals through the side of the aquarium.
Place a female cyclops with a few drops of water in a watch
crystal, or a piece of glass. Examine under a three-legged lens,
or under a low power of the microscope.

1. The foremost division of the body is the carapace.
How many segments has the thorax?

2. The egg sacs are attached to the first ring of the abdomen.

3. The eye ; note its color, position, shape, and parts.

4. The antennae and other appendages.

5 . How does Cyclops swim ?

Make a careful drawing of cyclops as seen from above. Cyclops
belongs to the subclass Entomostraca (water fleas) .

CHAPTER VI.
ANNULATA.

FIELD STUDY OF EARTHWORMS.

1. In what kind of places does the fisherman dig for earth
worms ?

2. Are they more abundant in one kind of soil than another?

3. Look for the coiled excrement, or " castings," at the mouths
of the holes. How many holes can you find in any square yard?
Find the number in several square yards at different places in a
rich meadow or pasture, and compute the number in an acre.

4. Do you find earthworms during the daytime ? If so, in what
conditions ? Hunt for them at night with a lantern. Are they far
from their burrows? Do they appear frightened? Do they re-
treat into their burrows?

5. If a worm is found partly extended from its burrow, seize
and try to pull it out. Is it easy to do so ? Why not ?

6. Carefully dig up a number of earthworms. How deep is the
burrow ? And what is its course ? In what part of the burrow is
the earthworm? Does the depth at which the earthworm rests
depend on the time of day? The condition of the soil? The
weather? Is the worm always the same end up? Is the hole
much wider than the worm? Could it turn around in the hole?

7. Do earthworms ever plug up the mouths of their burrows?
If so, when and with what material ? How is this work done ?

8. Do you find evidence of what earthworms eat? Do they
eat their food outside or in their burrows? Do they store food?
Do they spend much or litde time eating ?

9. Having- quiedy approached an earthworm that is out, or
partly out, of its burrow, suddenly make a loud noise. Does it

47

^ Practical Zoology.

seem to hear? Fire a pistol or cracker ; does it notice the noise?
Stamp hard on the ground ; does this affect the worm ?

ID. In what month are earthworms most active? When least
active ? Do earthworms hibernate ? How early are they seen in
spring ? How late in the fall ?

11. What enemies has the earthworm? Has it any means of
defense ? On what does it rely for protection ?

12. Do you discover anything to prove that earthworms lay
eggs? If so, when and where does this take place?

LABORATORY STUDY OF EARTHWORMS.

Get a box a foot deep and a foot or two square. Fill it with
fine, rich, black soil and press it down firmly, leaving an inch or so
of space above the soil. Keep the soil fairly moist. Earthworms
may be kept alive through the winter in boxes, or flowerpots of
soil, covered with sod and watered occasionally. The soil should
be kept cool and moist, but not wet. Put some dead leaves just
under the sod, and occasionally place cabbage leaves or lettuce
leaves on the sod for them to feed on. The boxes or flowerpots
may be kept in a greenhouse or in a cellar. Cover the box with a
large plate of glass. It is well also to have glass windows at the
sides and bottom.

i'. Place two dozen live earthworms on the soil. Watch them
as they burrow into the soil. Do the worms soon become settled,
or are they restless ? How soon do they reappear at the surface ?

2. Test the worms with various kinds of food, meat, both lean
and fat, bits of cabbage, celery, onion, turnip, apple, etc. Which
do they prefer? Do they show evidence of a sense of taste? Of
a sense of smell ? Do they eat on the surface or in their burrows?
Do they eat the material at once or keep it for a time? Do they
eat little or much? Do they exercise choice in selecting bits of
food according to their size or shape? When do they eat? Is
the process slow or rapid ? How is the eating done ?

3. Place an earthworm in a glass tube with good black soil, and
watch it from day to day.

Annulata. 49

4. Try the effect of sound on earthworms, being careful that
they do not get vibrations that affect the sense of touch during
the experiments.

5. Try the effects of Hght, being careful not to apply heat at
the same time. Place the worm in a glass tube, and let the light
fall upon one part at a time, covering the rest of the tube with a
cylinder of black paper. Try also the effect of heat without
light.

6. Repeat any experiments given under "Field Study" that
may profitably be reviewed.

7. What is the appearance of the surface of the soil as a result
of the work of earthworms ? What effect do earthworms produce
in the condition of the soil ?

STUDY OF A LIVE EARTHWORM.

1. Place a live, active earthworm on a large sheet of paper and
watch its behavior. Does it move with the same end always fore-
most ? Touch the end that is foremost to see if it will reverse its
motion. What changes take place in its body during locomotion?
Can you explain how it progresses ?

2. Take the earthworm in the fingers of one hand and draw it
over a finger of the other hand to feel the bristles ; of what use
are they? Can you learn how they are arranged? Do they point
more toward one end of the body than the other? Place the
worm on glass; can it crawl as well as on paper? Why should
the condition of the surface affect the worm's locomotion ?

3. Touch various parts of the body to learn the degree of
sensitiveness of different parts.

4. Turn the worm over on its back; does it remain in this
position ?

5. Take hold of the posterior end of the worm and drag it
backward along the paper ; listen for any sound thus produced.
How explain this result?

6. Rap sharply on the table ; does this affect the worm ?

7. Place the worm on a wet surface, and after a while on a dry

JO Practical Zoology.

surface; does it appear equally comfortable in both conditions?
Try also the effect of heat and cold, dust, mud, water, etc.

8. Observe along the middle of the back a blood tube; watch
its pulsations. Can you discover any other evidences of circula-
tion of blood ?

EXTERNAL FEATURES OF THE EARTHWORM.

1. The end that usually goes foremost is the anterior end; the
other end is the posterior end. Are the two ends of the same
color? The surface on which the earthworm ordinarily rests is
the ventral surface ; the surface usually uppermost is the dorsal
surface. The earthworm has right and left sides, that correspond
to each other ; such an animal is bilaterally symmetrical.

2. The earthworm is segmented, or marked off into rings called
segments. How many segments has your specimen? Are the
segments all equal in width ?

3. About one fourth or one fifth of the length from the head
observe a place where the segments are less distinct, often enlarged
and with a different color. This is the girdle, or clitellum. How
many segments does it occupy ? How many segments are anterior
to it?

4. Is the worm exactly cylindrical, that is, is the cross section
a circle ?

5. At the anterior end find the mouth. Overhanging it is a
sort of upper Hp called the prostomium. At the posterior end find
the anus. Is it circular?

6. Find the rows of bristles on the sides and ventral surface.
How many rows are there and how many bristles in a segment ?

7. On the ventral surface of about the fourteenth segment are
the rather distinct openings of the oviducts, and on the fifteenth
the openings of the sperm ducts. Between the ninth and tenth
segments are the openings of a pair of sperm receptacles, and
another pair open between the tenth and eleventh segments.
The positions of these openings vary in different kinds of earth-
worms, and they are not always easily discovered.

Annulata. 51

DISSECTION OF THE EARTHWORM.

Material : dissecting pan, forceps, scissors that cut well at the
point, dissecting needles, two dozen pins. Ribbon pins are best
for this work. Dissect under an inch of water and renew if it
becomes turbid.

1. Lay the specimen lengthwise on the board, stretch it, and
pin firmly at each end, slanting the head of the pin away from
the worm. Cut through the skin of the back near the posterior end,
and continue the cut forward a little to one side of the middle Hne.
With the forceps lift the edge of the cut and run the dissecting
needle along under it to cut the partitions that hold the body wall
down. Turn the edges of the body wall out and pin them down,
slanting the pins at an angle of about thirty degrees so they will be
out of the way.

2. As soon as the edges of the cut are separated the intestine
is seen. It is cylindrical, nearly filling the body cavity. It is
usually dark-colored from its contents.

3. Along the top of the intestine is the dorsal blood tube.

4. Observe now more closely the partitions which extend from
the intestine to the body wall between adjacent segments. Com-
pare the positions of the partitions with the external markings and
bristles. Are there as many segments as indicated by the external
appearance ?

5. Continue the cut to the anterior end, being careful not to
cut into the intestine, especially in the part anterior to the girdle.
Pin well out, and free the intestine by drawing the dissecting
needle along its sides to cut the partitions.

6. In the region of the tenth segment are several pairs of white
bodies, the sperm sacs.

7. Alternating with these are several red masses. They are the
aortic arches, which spring from the dorsal blood tube and arch
around on each side to join the ventral blood tube beneath the
digestive tube. In some earthworms each aortic arch has several
enlargements, making it resemble a nfecklace. The enlargements

52 Practical Zoology.

are sometimes called "hearts." In a recently killed specimen
they may be seen pulsating.

8. In the first six segments is a wide portion of the digestive
tube, the pharynx. It has threads of muscle connecting it with
the body wall. The pharynx is used as a proboscis, being pro-
truded from the mouth and everted.

9. The pharynx narrows behind into the gullet. This extends
through several segments, but is hidden by the sperm sacs and the
aortic arches. Clear these away.

10. In removing the sperm sacs there may be seen in the ninth
and tenth segments two pairs of small, white, spherical bodies, the
sperm receptacles. The still smaller ovaries may be found in the
thirteenth segment.

11. Back of the spermaries are two enlargements of the diges-
tive tube. The first is the crop and the second the gizzard.

12. From the gizzard to the posterior end of the body extends
the intestine. Is it uniform in diameter? If not, where is it
wider and where narrower?

13. Cautiously dissect away the intestine. Under it is the
ventral blood tube. From it as well as from the other principal
blood tubes there are smaller branches to supply all the tissues.

14. On the very floor of the body cavity, in the middle Hne, is
the nerve cord, resembling a white thread. Trace it from behind
forward. In each segment is an enlargement, or ganglion. From
the ganglions proceed branches to supply the surrounding organs
with nerve fibers.

15. Under the anterior end of the pharynx the nerve cord
separates into two parts, one passing up on each side to enlarge
into a ganglion. These two ganglions are the cerebral ganglions,
or brain, and the ring of nerve cord around the pharynx is the
nerve ring or nerve collar.

16. Attached to the ventral body wall, on each side of the
digestive tube, are many small, threadlike, coiled bodies. Exami-
nation with a lens shows a pair of these in each segment. They
are the kidneys or nephridiA. Each is a tube thrown into iopps

Annulata. 53

The kidneys open to the outside usually between the inner and
outer rows of bristles, but sometimes above the lateral row of
bristles. And each tube kidney begins as a funnel, which is in
the segment in front of the one in which the loops of the kidney
are found.

17. The outer layer of the skin is thin and easily peels off.
This is the cuticle, and is noticeable on account of its pearly luster.
The bulk of the body wall is composed of two layers of muscles,
the outer of circular and the inner of longitudinal fibers, by means
of which the worm moves.

18, In a freshly opened earthworm mount a drop of the milky
liquid found in the body cavity and examine it under a one-sixth
objective. The corpuscles should be distinctly seen.

CROSS SECTION OF AN EARTHWORM (MICROSCOPIC).

1. Examine cross sections under the microscope, with a low
power, one-half or two- thirds inch objective. The body wall may
be seen to consist of several layers. The intestine has an extension,
the typhlosole, from its dorsal wall, occupying considerable of the
space within, and adding much to the inner surface of the intestine.

2. Examine with a higher power, one-fourth or one-sixth inch
objective. There are five layers of the body wall : (a) the thin
cuticle ; (^) a thicker layer of skin, the hypodermis, or epidermis,
which produces the mucus which coats the outside of the worm ;
(c) the layer of circular muscle fibers ; (d) a thicker layer of
longitudinal muscle fibers ; (e) a very thin layer of peritoneal
epithelium.

3. The dorsal blood tube lies embedded in cells on the dorsal wall
of the intestine. Under the intestine is the ventral blood tube. Still
lower is the nerve cord, or ganglion, as the section may strike.

Read T/te Formation of Vegetable Mold through the Action
of Earthworms, Darwin ; or the chapters on the earthworm in
General Biology, Sedgwick and Wilson.

Topics for Reports. — Varieties of Earthworms. Marine Worms,
Leeches.

CHAPTER VII.

MOLLUSCA.

HELD STUDY OF FRESH-WATER CLAM.

Look for clams in the shallow water of creeks and lakes. Note
the natural position. How much of the shell is embedded ? Is the
shell open or shut ? Can you see any openings by means of which
the clam communicates with the water? Touch the clam and
note any changes that take place. Quickly pull up the clam and
note the extended foot. Watch clams to see if they move. Do
they move with the same end always foremost? How does
the foot point with reference to the direction of locomotion?
Does a clam make a track? Can you tell by the track in which
direction the clam traveled ? Does the direction of travel have
any relation to the current of the stream? Why do clams
travel? If possible, make a series of observations to find out the
rate of locomotion. Where are clams more abundant, on sandy or
on muddy bottoms ? How many kinds do you find ? Do differ-
ent kinds show preference as to soil? Has the color of clams
any relation to the surroundings? Do you find any evidence that
clams have enemies? Of what kinds? How are clams protected
from enemies? What conditions are unfavorable to clams? Do
they prefer deep or shallow water? Do they occur singly or in
groups? Do different kinds occupy the same region?

AQUARIUM STUDY OF A LIVE CLAM.

If a good aquarium is not obtainable, a battery jar, a tub, or a
large pail will serve. Put in three inches of sand and add enough
water to stand three inches above the sand. Let this stand over
night to allow the water to become clear.

54

Mollusca. 55

Position of the Clam. — Drop several clams into the water and
note carefully the place and position of each. Watch them as
closely as possible to see if they change their place or position,
and if so, learn how this is done.

Locomotion. — Watch clams that have established themselves in
their natural position, to find out how they travel. Do they
leave a track ? If so, of what sort is it ? Is the motion slow or
rapid? Is it at a uniform rate, or irregular? Quickly pull up a
clam that is moving and note the projecting foot. Place a clam
close to the side of a glass aquarium ; the foot may be protruded
so close to the glass as to be seen. Why do clams travel? Can
a clam crawl on a hard surface?

Water Currents. — Note that a clam, when established in a
natural position and left undisturbed, has the shell sHghtly open.
Near the upper edge of the more exposed end look for two
eUiptical holes ; these are the siphons. Watch to see if there is any
evidence of currents through these holes. Reduce the amount of
water so that it is about half an inch deep over the siphons of a large
clam. Look closely at the surface of the water over the siphons for
evidence of water currents. Take a slender glass tube, dip one
end in ink, place a finger over the upper end of the tube and lift
out a little ink. Carefully introduce a drop of this above the
siphon opening. The currents may also be revealed by a little mud,
but care should be taken not to drop coarse mud or sand on the
siphons. What happens when the margins of the siphons are
touched? Pull up a clam that is in "full blast," watching closely
the siphons. Describe what you observe.

Senses of the Clam. — Test in various ways the senses of the clam.
Touch it lightly and heavily; jar the floor near the aquarium.
Throw strong light (without heat) upon it. Try heat without light.
Test for all the senses you think a clam may possess.

Protection of the Clam. — Note again the changes that take place
when an active clam is taken from the water. Now try to open
the shell with the hands alone. Why does the clam have such a

^6 Practical Zoology.

hard covering and the ability to shut it so tightly and remain shut
so long?

EXTERNAL FEATURES OF THE CLAM SHELL.

If a live clam is used, place it on a plate, or in the dissecting pan.

1. Notice the two parts of the shell, — the valves.

2. The edge along which the shell opens is the ventral margin.

3. The edge by which the two valves join each other is the
dorsal margin, or hinge margin.

4. The concentric lines parallel to the ventral margin are the
lines of growth.

5. The raised point around which these lines center is the beak,
or umbo. The umboes are nearer the front, or anterior, end of
the clam.

6. Toward the posterior end, back of the umboes, between
the valves, and uniting them, is the hinge ligament.

7. Hold the closed shell with the hinge margin uppermost, the
hinge ligament nearer, and the umboes pointing away from you.

The end pointing from you is the anterior end.

The end pointing toward you is the posterior end.

The upper edge is the dorsal margin.

The lower edge is the ventral margin.

The half-shell to your right is the right valve.

The half-shell to your left is the left valve.

Fix these relations firmly in mind.

8. Make a drawing of the clam as seen from the left side,
naming all the parts.

9. Observe the color, the degree of cleanness, and general
condition of the different parts of the shell, and consider the
relations between these facts and the position of the clam when
first found.

DISSECTION OF THE CLAM.

How to open a Clam. — It is difiicult for beginners to open
clams without mutilating the soft parts. It is better to have them
opened by the teacher. If any student is following these direc-

Mollusca. 57

tioiis without the aid of a teacher, he will find directions for
opening clams, without using hot water, in the Suggestions to the
Teacher of Zoology, in a separate pamphlet.

Put the hve clam for a few minutes into water as warm as the
hand can well bear. This causes the muscles to relax, so that
the shell can be readily opened. Pry apart the two valves, and
insert a half-inch block to keep them from shutting.

1. Observe a soft white membrane, the mantle, adhering to the
inner surface of the shell. Look in at the posterior end for
the two siphon openings. Now hold the clam in the left hand,
with the left valve up and the ventral margin toward you. Insert
the chisel-like handle or the blade of a scalpel between the mantle
and the left valve, and gently separate them by sliding the scalpel
handle along the inner surface of the shell. In this way proceed
backward, around the posterior end of the shell, then forward
along the dorsal margin. Back of and below the hinge is a large
white muscle, which extends directly across from valve to valve.
Cut this off close to the left valve if it is not already severed. In
like manner loosen the mantle at the anterior end, and find another
muscle connecting the two valves near the anterior dorsal margin.
Sever as before, close to the left valve, and loosen the mantle
completely from the left valve,

2. Press the shell shut ; now release the pressure. What makes
the shell spring open ? Repeat the closing and releasing until you
have a satisfactory explanation of the method of opening. Be on
the lookout later for the means by which the clam shuts its shell.
Break off the left valve by bending it forth and back, twisting it
off if necessary.

3. Lay the clam in the dissecting pan and cover it with water.
Renew the water as often as it becomes turbid. To keep the
clam level use the left valve, hollow side down.

Observe that the left mantle lobe now covers the body, and that
the right lobe lines the right valve. Notice the thicker margin of
the mantle. Pinch this thick edge ; if it has not already shortened
as much as possible it may draw up slightly. Observe a thin,

58 Practical Zoology.

dark-colored membrane bordering the edge of the shell. This is
the periostracum, an extension of the outer covering of the shell
Scrape off some of it to see its relation to the limy shell. Care-
fully study the relations of the periostracum to the mantle. Pinch
the edge of the right mantle lobe, and observe the effect on this
free border. Trace the right and left mantle lobes to their points
of union before and behind.

4. Examine the thick, dark-colored, hinder edge of the mantle
lobes, and see how by their manner of meeting they form the two
short tubes, the siphons. Prove the great sensitiveness of the
margins of these siphon tubes. Are the margins of the two
openings alike?

5. Examine the ends of the anterior and posterior adductor
muscles where they were cut off in opening the shell ; scrape away
any part of these muscles that may remain attached to the left
valve, and note the marks or muscle scars which are shown.

6. Turn the mantle lobe back as far as it will go, and observe
the soft central body ; its tough lower border is the foot ; prick it
with the dissecting needle, and observe what follows.

7. Along each side of the body and extending back of it are
two thin membranes, the gills, showing vertical parallel markings.
Study closely the relations of the gills to each other, to the body,
and to the mantle.

8. With a knife scrape off a little of the surface of the gill and
examine under the microscope to see the vibratory motion of the
hairlike projections, or cilia, borne on the cells thus obtained.

9. In front of the gills, on each side of the body, are two thin
triangular flaps, much smaller than the gills, the labial palps.

10. Raise the hind border of the left mande lobe, and observe
that the gill next to the body unites with the corresponding gill of
the other side, thus forming a separate channel above the gills,
from which the upper siphon leads, while the lower siphon leads to
the lower cavity, outside of and below the gills.

11. With the thumb and all the fingers of the left hand seize
the left lobe of the mande and pull it toward the ventral margin,

Mollusca. 59

thus drawing the body away from the dorsal margin. Just under
the hinge a pale organ may be seen, pulsating every few seconds ;
this is the heart.

12. Holding the mantle stretched, again examine the upper
siphonal opening ; probe to see how it extends forward above the
united hinder portion of the gills. In the upper part of this cavity
find a tube running back over the posterior adductor muscle, and
ending in a conical elevation ; this tube is the intestine, and the
opening at its end is the anus ; hence the siphon leading from this
cavity is called the anal siphon ; the lower siphon, which conducts
water to the gills and mouth, is called the branchial siphon or gill
siphon. Examine the gills from above, i.e. examine their dorsal
margins ; observe that the two outer walls of each gill are a short
distance apart at this edge, while below these walls unite, so that
if the gill be cut across, these walls, as seen at the cut, are like the
letter /. These diverging walls are connected by cross partitions,
thus forming a series of compartments within the gill, whereas if
these partitions were absent, each gill would be a deep, narrow,
undivided trough. The lateral walls of the gills are sievelike, and
the surface of the gill and the edges of the holes are covered with
cilia. The vibrations of these cilia drive the water which is around
the gin through these holes into the cavities within the gill ; the
water from each compartment of the gill passes up into the
chamber leading to the anal siphon.

13. Beginning at the upper edge of the anal siphon, in the
middle line, cut carefully forward just above the intestine as far as
the umbo. This lays bare the cavity in which the heart lies, the
pericardial cavity. Carefully cut away the thin covering of this
cavity and make out the following parts of the heart : —

a. The large yellowish ventricle in the anterior part of the cav-
ity ; time its pulsations ; observe that the intestine runs directly
through the ventricle, though it has no communication with it. An
artery runs forward from the ventricle along the upper surface of
the intestine ; another artery runs from the ventricle backward
under the intestine. Again pull the mantle ventralward to show b.

6o Practical Zoology.

b. A thin sac, triangular as seen from the side, with its apex join-
ing the ventricle, and its base attached just above the upper edge
of the gills; this is the left auricle. Each auricle receives the
blood from the gills of the corresponding side.

14. Just in front of the posterior adductor muscle are the dark
kidneys.

15. Above the kidney, and in front of the posterior adductor,
is a small muscle, which extends backward from the side of the
body to join the valve near the posterior adductor. This muscle
pulls the foot upward s.nd backward, hence is called the posterior
retractor muscle.

16. Below and a little back of the anterior adductor muscle,
find the protractor muscle, which pulls the body and foot forward.

1 7. Just above and back of the anterior adductor is the anterior
retractor muscle, which pulls the foot and body up and backward.

18. To find the mouth, hold the clam, anterior end uppermost,
still attached to the right valve ; press down the point of the foot,
and find the mouth opening posterior to the anterior adductor;
observe that the two outer palps unite above the mouth, and the
two inner palps unite below the mouth. Back of the anterior ad-
ductor a dark-colored mass may be seen within the body ; this is
the digestive gland, which surrounds the stomach. The intestine
has several coils in the body before emerging on the dorsal surface
a short distance in front of the heart. The intestine can be traced
much better in an alcoholic specimen.

.9. Beginning at the posterior adductor, cut away all the free
flap of the left mantle lobe, following the upper edge of the gills
(being careful not to cut away the labial palps) to the upper edge
of the anterior adductor. Make a drawing of all the parts above
named, as they lie in the right valve.

20. Remove all the remaining soft parts except the adductor
muscles. Since the chief characteristic of muscle is its ability to
shorten, it should now be clear how the clam shuts its shell. Turn
back to No. 2 of these directions and consider the relations of the
mechanisms for opening and shutting. What actions take place

Mollusca. 6 1

during the closing ? What actions during opening ? Thoroughly
clean the inside of the shell, and keep it for further study.

DEVELOPMENT OF THE CLAM.

Occasionally a clam may be found with the outer gills greatly
thickened. Cut into such a gill and remove some of the con-
tents. Place a httle of the material on a shde and spread it out
in a drop of water. Examine with a low power of the micro-
scope. The parts of the young clams should be seen. How does
the shape of the shell compare with that of the adult ?

THE NERVOUS SYSTEM OF THE CLAM.

This dissection requires the utmost care and patience. Take a
clam that has been hardened in alcohol, or by boiling. Dissect
under water ; rinse the specimen often.

1. Immediately under the posterior adductor muscle find a
double yellowish body ; this is composed of the two visceral gan-
glions ; dissect away the thin membrane covering them.

2. From these ganglions trace nerves backward to the gills and
to the posterior borders of the mantle lobes ; trace also two nerves
forward, carefully dissecting away the soft parts that cover them
anteriorly, and trace them to the sides of the mouth where they
join 3.

3. The cerebral ganglions ; these lie near the surface at the
bases of the labial palps. Trace a small nerve which connects the
two cerebral ganghons over the mouth.

4. From each cerebral ganglion trace nerves backward and
downward to 5.

5. A pair of orange- colored pedal ganglions, lying together
deeply embedded between the foot and the body.

In the alcoholic specimen the stomach and intestine may be
traced. Cross sections of alcoholic specimens may be made with
a razor, which show admirably the relations of the different parts
of the clam.

6a Practical Zoology.

THE INSIDE OF THE CLAM SHELL.

1. Observe the color of the lining layer. Is it uniform? How
would you describe the surface finish.

2. The hinge teeth. These are of two sorts : (i) the cardinal
teeth, blunt, toothlike projections near the umbo; (2) the lateral
teeth, long, ridgelike projections below the hinge ligament. Note
how many of each of these kinds there are in each valve. How
do they fit into each other? What is their use? Do you find
them in all clam shells?

3. The muscle scars: (1) the anterior adductor muscle scar,
near the anterior dorsal margin ; (2) the posterior adductor muscle
scar, near the posterior dorsal margin ; ( 3) the anterior retractor
muccle scar, just above and back of the anterior adductor scar, not
very distinct ; (4) the posterior retractor muscle scar, just above
and in front of the posterior adductor scar; (5) the protractor
muscle scar, just below and back of the anterior adductor scar ;
(6) the mantle line, running parallel to the ventral margin, from
the anterior adductor to the posterior adductor scar.

4. The movements of the muscle scars. When the clam was
smaller than it now is, where were the adductor muscle scars?
Can you see any traces of the positions of these muscles at an
earlier stage of life? Is there an evidence of growth over any
part of the muscle scars that now show? Does the mantle line
shift its position with growth?

5. The ligament. Examine the hinge ligament where it was
broken off. Has it a definite structure? What is its chief charac-
teristic?

6. Take an empty shell with the valves still hinged together ;
cut and fit into this a piece of paper showing the shape of the
whole mantle.

7. Make a plaster of Paris cast of the inside of a whole shell.

• 8. Make a drawing of the inside of the right valve, labeling all
the features above noted.
Take a large flat shell and label (with ink) both the external

Mollusca. 62

and the internal features ; it may be found convenient to label part
of the features in one valve and part in the other.

Structure of the Clam Shell. — For this work get the thickest and
heaviest shells, at least one valve for each member of the class.
Weigh them and then roast them by laying them on an old shovel
or layer of sheet iron, and placing them on the coals in a stove or
furnace. After roasting handle them carefully so as to keep them
entire. Weigh them again after roasting and compare with the
former weight.

Hold a roasted valve by the dorsal margin in the left hand,
with the inside of the valve toward you. With the fingers of the
right hand supporting the outside of the valve, press with the
thumb on the ventral border of the valve, outside of the mantle
line. The shell should separate into two parts, the inner begin-
ning very thin at the mantle line and becoming thicker toward the
umbo ; the outer portion extending the whole width of the valve,
but becoming thicker from the umbo to the mantle line and thin-
ner again from this line to the ventral margin. It will be seen
that the plane of division is the plane along which the mantle line
has traveled during the growth of the shell. Break a burnt shell
across from the umbo to the ventral margin, and make a drawing
of the edge thus exposed, showing the arrangement of these sets
of layers.

Composition of the Clam Shell. — Put pieces of the burnt shell
into dilute hydrochloric acid. The acid decomposes the limy
compound, setting free carbon dioxid. If a fresh shell is placed
in acid, the mineral matter will be slowly dissolved, leaving the
flexible animal matter, which is called conchiolin. The hinge liga-
ment is nearly pure conchiolon, being simply a part of the shell
in which no limy matter has been deposited. When the shell is
burned the animal matter is burned. The remainder after roast-
ing is of about the same composition as Hme. Put into acid
a piece of the ligament. Does it cont^m lime? Place an entire
valve of a thin-shelled clam in acid for forty-eight hours; what
remains? Are shells ever found in rocks?

64 Practical Zoology.

Topics for Reports. — The Oyster Industry. The Pearl Fisher-
ies. Pearls from Fresh-water Clams. Kitchen Middens. Clam-
bakes. Wampum. Tridacna. Mother-of-pearl. Pearl Button
Factories. The Chambered Nautilus. The Paper Nautilus. The
Giant Squid. The Octopus. Snails as Food.

THE POND SNAIL.

A dipper with a perforated bottom, attached to a wooden
handle, will be found convenient in scooping up the sand and
mud from the bottoms of ditches and streams; the dirt being
washed out, the shells and other objects will be left behind. . Get
a number of live snails, and keep them in a fruit jar.

1. The broad disk on which the snail creeps is the foot.

2. The "horns" are the feelers, or tentacles; touch them;
what would seem to be their use ?

3. The dark spots at the bases of the tentacles are the eyes ;
are they borne on a stalk in any common snails?

4. Watch the snail crawling on the glass ; near the front of the
foot the mouth may be seen ; observe its opening and shutting as
the snail gathers food from the surface of the glass. Do snails
clean the glass or foul it? Most snails have a ribbonlike tongue,
fastened at each end, and covered with teeth ; as this tongue is
applied to an object, and drawn rapidly back and forth, it acts like
a rasp.

5. Watch the snails, to see if any of them come to the surface
to get air ; how is this done ?

6. Collect also land snails and river snails. Keep them and
watch them to learn their structure and habits.

The Snail Shell.

1. The pointed end is the apex.

2. The opening at the large end is the aperture.

3. The outer edge of the aperture is the lip.

4. The lines parallel to the lip are the lines of growth.

5. The spiral groove on the outside is the suture.

Mollusca. 65

6. The turns of the shell between the groove are the whorls. "

7. The whorls, taken together, make the spire.

8. The lid closing the aperture is the operculum ; is this present
in all the snails you find ?

9. Lay the snail shell beside a common screw; if the whorls
turn like the threads of the screw, it is a right-hand, or dextral,
shell, if they turn the other way, it is a left-hand, or sinistral, shell.

10. Make a drawing, naming all the parts, of the snail shell
with the aperture toward you ; with the aperture away from you ;
with the apex toward you.

Read The Chambered Nautilus ^ Holmes.

CHAPTER VIII.
PISCES.

FIELD STUDY OF FISHES.

Difficulties. — In order to study fishes in their own homes with
any degree of success, the student should know what are some of
the main difficulties. First, a difficulty that is found in studying
any wild animals, their shyness. The student must learn to ap-
proach them carefully. Second, the colors of fishes, as of many
other animals, is such as to render them very hard to see. Third,
the difficulty in seeing them is increased by the refraction of light
leaving the water to enter the air, and also by the reflection of light
from the surface, which greatly interferes with seeing what is below.
This is especially noticeable in trying to see fishes from a boat, in
which case the angle is quite oblique. Having in mind these
difficulties and the determination to overcome them so far as pos-
sible, let us proceed to study the fishes in their homes.

Frightening Fishes. — When a fish darts away at your approach,
endeavor to learn by what sense he first became aware of your
presence. Was it by sight ? If so, what can you do to overcome
the trouble ? Is it the color of your clothing, or of your boat ?
Is any given color, or group of colors, preferred for fishing boats ?
Which will frighten more, oars or a paddle ? Should the paddle be
hfted from the water, or used wholly in the water by making the
recover stroke with the edge of the blade cutting thru the water?
What part does the sunlight play in the use of oar or paddle ? Does
quickness of motion make any difference, the range of motion being
the same ? In using an anchor, which is better, a rope or a chain ?
Which is to be preferred, a wooden or a metal boat? Do fishes
hear one who talks in a boat? Do sounds made by hitting the

66

Pisces. 67

boat, as with the heel, communicate with the water ? Is it well to
have bright metal, such as nickel or silver, on fishing rods?

The Water Glass. — The difficulties of seeing into water may, to
a considerable extent, be overcome by the use of a water glass.
This is a box or cyHnder with a glass bottom. When the glass
bottom is pushed down into the water, the face over the open end
shuts out most of the light from above, thus getting rid of the con-
fusion from reflection. It is possible to make such a glass as
part of the boat, so one can view what is under the boat.

Food of Fishes. — Find what the fish you are studying prefers to
eat. If you are fishing, examine the stomach of the first fish you
catch to see what it has been eating. The wise fisherman will do
his best to cater to the taste of the fish he would catch. Why does
the fly-fisher drag the fly on the water, or make it dance about?
Find the time of day at which a fish prefers to eat. Does this
vary with any discoverable conditions ? Do fishes eat during the
night? What do the various artificial baits imitate?

Hiding Places. — What sort of places do fish hide in? Do they
hide to escape enemies, or that they may catch unsuspecting prey
that passes by their lurking place ? In what situations does the
fisherman look for different kinds of fishes ?

Sociability. — What fishes hve a solitary life ? What kinds go in
schools? What advantages in community life? What disadvan-
tages ? Does a school of fish scatter when frightened ? Do they
come together again soon ?

Position in a Current. — When in a current do fishes maintain
any fixed relation to the current, that is, do they rest crosswise,
or lengthwise, in the stream? If lengthwise, is the head up or
downstream? Why this position ?

Egg Laying. — At what season does the fish you are studying
lay its eggs? Are they usually deposited in the same surroundings?
How long time is taken in depositing them ? Are they guarded ?
^hat animals may destroy them? What conditions are favorable

68 Practical Zoology.

or unfavorable to their development? If possible, learn tlie rate
of growth of fish.

Fish in Winter. — Do fishes migrate ? Are most fishes to be
found in the same place, winter and summer? Are they equally
active at different seasons?

AQUARIUM STUDY OF FISHES.

Respiratory Movements. — Watch minnows or goldfish in an
aquarium. Note the movements of the mouth and the gill covers.
In what order do these movements proceed ? Watch closely to
see if there is any water current in connection with these move-
ments. If there is no floating matter by which to get evidence of
a current, introduce a drop of ink near the fish's head and thus
determine the direction of the current.

Mode of Swimming. — How does the fish swim ? Watch especially
the slow movements, during which the facts can be more readily
learned. What is the main propelling power? How is the course
guided ? How is the shape adapted for movement in the water ?

Uses of the Fins. — Take a light rubber band and pass it round
the fish, holding down the various fins in successive experiments.
Watch the resulting movements and conditions of the fish.

How a Fish Floats. — Does a fish make effort to maintain its
place in water? Does it make any apparent effort in rising or
sinking? Do any fishes habitually remain on the bottom? Do
any stay at the surface ? Is there any difference in their structure
or habits that fits each for its place ?

Comparison of a Minnow and a Darter. — These two forms are to
be found in most creeks. In using a minnow seine, be careful to
"keep the lead line down" and you will be much more likely
to get darters. These are small fishes, with double-cone-shaped
bodies. They habitually rest on the bottom. Watch carefully their
movements. What takes place when they cease to make active
effort? Do they swim in the same way as the minnows? Open a
minnow and also a darter to see if tb^re is any essential difference

Pisces. 69

in the structure of the two. Why should the darters have this
habit of staying on the bottom ?

Senses of Fishes. — Watch the movements of the eyes of a fish.
What range of movement have they ? Do the eyes move simulta-
neously? Does a fish see any better than you do? Devise means
of testing the sense of hearing without affecting the other senses.
Test the different senses in various ways. On which senses does
the fish most rely for safety ?

Food and Mode of Eating. — Offer a fish various kinds of food and
find what it hkes best. How does it take its food ? What relation
has the shape or size of the mouth to the kind of food taken?
Does a fish eat much, or little, relatively? In feeding fishes take
care not to give too much at one time, for fear of fouling the water.
Do fishes suffer from overeating?

Sleep. — Do fishes sleep? Have they any special resting place
or resting position ?

EXTERNAL FEATURES OF A FISH.

For this work, and the dissection that follows, the perch is pref-
erable for inland students, though the bass, croppie, or sunfish
serves very well. On the seacoast the cunner or the sea perch
is more accessible.

Lay the fish on a sheet of thick paper, on a plate, or in the dis-
secting pan.

I. Notice the shape of the fish as a whole ; how is it adapted for
motion through the water? Hold the fish with the back uppermost
and the head directly away from you ; instead of speaking of the front
and hind ends, it is better to call them the anterior and posterior
ends. The upper surface, or back, is the dorsal surface, and the
lower the ventral surface. The right and left sides are counter-
parts of each other ; that is, the fish is bilaterally symmetrical.

The perch is flattened from side to side, and is therefore said to
be compressed. A fish is properly described as " flat " only when
flattened on the dorsal and ventral surfaces, or depressed, as in the
case of the rays.

yo Practical Zoology.

In the following directions, relative and not absolute measure-
ments are intended. Instead of using a foot rule, take a strip of
paper and mark the entire length, head, depth, etc., either by
pencil or by folding. Compare these so as to be able to say
whether the head is one third, one fourth, or what part, of the
length of the body.

Close the mouth of the fish, and measure from the foremost
point of the head, the tip of the snout, to the front edge, the
base, of the tail fin ; this is the length of the fish. Measure from
the tip of the snout to the hinder point of the hard part of the
flap which covers the side of the head ; this is the length of the
head. How many times is the length of the head contained in
the length of the fish? Measure from above downward at the
deepest part ; this is the depth of the fish. How many times is it
contained in the length? Compare the width and the depth of
the fish.

2. The fins on the back are the dorsal fins; spread them out
to their fullest extent, and study them thoroughly ; their framework
consists of fin rays, some of them spinous rays, or spines (un-
jointed, or inarticulated) , others soft rays (jointed, or articulated).
Study carefully one of the soft rays, using a lens ; spread the fin
and hold it between you and the light to see the joints, which ap-
pear as fine cross lines on the soft rays ; count each kind of rays ;
observe the membrane connecting the rays. This membrane is
double ; the fin is really a fold of the skin, with supporting parts
within the fold.

Measure along the base of each fin; this is the length of the
fin ; extend the fin fully, and measure the length of its longest
ray ; this is the hight of the fin. Compare the length and the hight
of the fin. In some fishes the dorsal fin is single ; in others it is
divided, forming two or more dorsal fins.

The tail fin is the caudal fin; is it symmetrical? The fin in
front of and below the caudal is the anal ; compare this fin with
the dorsal. The fins above named, being in the middle line, are
called median, or vertical, fins.

Pisces. 71

The remaining fins are called paired fins ; the pair back of the
head are the pectoral fins, and are considered as representing
the fore limbs of the higher animals ; the lower pair (usually farther
back) are the pelvic fins, representing the hind Hmbs of higher
animals. Take the pelvic fins between the thumb and finger to
feel their bony support; rest the fish on its back, and press the
thumb and forefinger of the other hand on the bony structures
at the bases of the pectoral fins; move the pelvic fins about to
determine, as far as possible by feeHng, the relations between
the bones supporting the two pairs of fins.

3. Open the mouth of the fish by pulling its lower jaw down as
far as possible ; the bone which forms the border of each side of
the upper lip is the premaxillary ; note its extension backward on
the middle of the snout ; observe the fine teeth on it. Observe
their size, shape, arrangement, and the direction in which they
point. The paddlelike bone back of the premaxillary, outside of
the mouth, is the maxillary. The bone on each side of the lower
jaw is the dentary.

Which of the above-named bones bear teeth? Open and shut
the mouth repeatedly, watching the movements of these parts,
and their relations to each other.

Back of the premaxillary, in the front part of the roof of the
mouth, is a patch of teeth, borne on a bone called the vomer;
extending backward from the vomer, on each side of the roof of
the mouth, are rows of teeth on the palatine bones.

Examine the short tongue ; feel its surface with the tip of the
finger, or scrape it with the head of a pin ; examine also the whole
of the inside of the mouth, to see if there are more teeth than
those mentioned.

4. Note the shape and position of the eyes ; with the handle of
the forceps press on the eye at various points near its margin, to
see its range of motion ; watch the roof of the mouth while press-
ing the eye, also press outward on that part of the roof of the
mouth nearest to the eye. Compare the eyes with human eyes.
Are eyelids present? Observe a thin bone embedded in the skin

72 Practical Zoology.

immediately in front of the eyes ; it is the anteorbital bone. This
and several smaller bones just under the eye are known as sub-
orbital bones.

5. Examine the nostrils in front of the eyes. How many are
there? Probe them with a bristle tipped with sealing wax, or
with the head (never the point) of a small pin ; do they open into
the mouth? Do any of them communicate with each other?

6. The flap at the side of the head is the gill cover, and the
opening back of it is the gill opening. The upper, hinder piece
of the gill cover is the opercle ; along its lower posterior border,
and rather closely attached to it, is the subopercle ; in front of the
opercle, and below and back of the eye, bordering the part known
as the cheek, is the preopercle. If the margin of this be toothed,
it is said to be serrate ; under the preopercle, and in front of the
lower end of the subopercle, is the interopercle.

The thin membrane below the gill cover is the branchiostegal
membrane ; the curved bones supporting it are the branchiostegal
rays ; count them. The narrow part of the body between the
branchiostegal membranes is the isthmus.

7. Raise the gill cover and examine the gills ; each gill has a
central bony arch ; on the hind and outer border of this arch is a
fringe of red gill filaments ; on the front and inner border of the
arch are the teethlike gill rakers. Are these ahke on all the
gills? A red streak along the arch, at the base of the filaments,
is made by the blood tubes, which bring the blood to and carry
it away from them.

Thrust a finger into the mouth, and depress the tongue. What
effect has this on the gills? What effect on the gill rakers? The
slits between the gills, which allow communication from the
mouth to the gill openings, are the gill clefts. How many gills
are there? How many gill clefts? After this study of the gills in
their natural position, remove the foremost gill, severing it at its
upper and lower ends, and note more fully the parts above named,
especially the structure and arrangement of the gill filaments and
gill rakers ; tear away some of the filaments, and find the groove

Pisces. 73

along the posterior, outer border of the bony arch in which run
the blood tubes. Look on the inside of the gill cover for a red
spot, the false gill.

8. Observe the arrangement of the scales. Pull out a scale and
study its shape and the radiating and concentric markings. Com-
pare its inner and outer surfaces, its anterior and posterior margins ;
make a drawing of it, naming its parts ; pull out a scale from a
black spot ; compare that part of its surface which was exposed
with the part overlapped by other scales ; scrape the portion that
was exposed ; thrust one point of the forceps under the hind edge
of a scale, and watch closely this edge, while slowly raising it, to
see that a thin skin covers it and passes on to the scale behind.
This thin outer skin is chiefly epidermis. In this epidermis lie the
black pigment cells which make the dark spots. A scale with a
smooth hinder border is a cycloid scale ; if the hinder portion is
toothed or spiny, the scale is ctenoid.

9. A raised line along the side is the lateral line. Remove
one of the scales on this line, and find what makes the line. Is
the line continuous?

10. Make a drawing of the fish as seen from one side, naming
all the parts visible. Describe fully all the parts above noted,
including the general color and markings.

Use Jordan's Manual of the Vertebrates for finding the names
of the fishes of your neighborhood.

DISSECTION OF A FISH.

Dissect on a board covered with paper. A few carpet tacks
will be needed.

Hold the fish with its back in the palm of the left hand and the
tail toward you. Thrust the point of one blade of the scissors
obliquely forward through the body wall just in front of the anus,
and continue the cut forward half an inch. Now rest the fish on
its back and get hold of the edge of the cut with the forceps ;
as you cut forward in the middle line lift the edge of the body
wall to see that no internal organ is injured. When the pelvic fins

74 Practical Zoology.

are reached, the body wall is stronger and cannot be cut with the
tips of the scissors without danger of straining them ; lift with
the forceps almost enough to raise the fish ; insert nearly the
whole length of one blade so as to cut near the joint of the scis-
sors between the pelvic fins. Continue the cut to the narrowest
part of the isthmus, where it joins the branchiostegal membranes.

1. Observe that most of the internal organs are in one large
cavity, called the body cavity. Its silvery lining is the peritoneum.

2. Near the anterior end of the opening, about opposite the
posterior border of the gills, find a transverse partition, the false
diaphragm ; back of this is the main body cavity ; in front of the
partition is the pericardial cavity, which contains the heart.

3. Keeping the fish still on its back, turn now to the posterior
part of the body cavity. While holding the edge of the body
wall, use the scalpel handle to push aside the internal organs.
Note how yielding is the membrane on which the internal organs
rest. Beyond this membrane is the air bladder. Be careful not
to cut into it until directed to do so.

4. Turn the abdominal wall outward and note the projections
made by the ventral ends of the ribs. Begin again at the point
of beginning of the first cut, just in front of the anus, and, with
scissors, cut the right side of the body wall along the ends of the
ribs as above noted. Continue the cut as far as the bony pectoral
arch, just back of the gill opening. Repeat this cut on the left
side. Look again at the false diaphragm and its relations to sur-
rounding organs, as it will probably be torn in following subsequent
directions. Now turn the two flaps of the body wall well out and
forward, and tack them down so as to hold the fish securely resting
on its back.

5. In the front part of the body cavity is a dull pink or brownish
mass, the liver, lying chiefly on the left side of the fish. Raise
the hinder edge of the liver, and observe how closely it fits the
organs next to it. Press the liver backward, and observe the hepatic
veins passing forward from the liver through the thin partition, the
false diaphragm, in front.

Pisces. 75

6. Turn the liver to the right, gently tearing away its threadlike
attachments. This uncovers a pinkish sac, the stomach. Pass a
probe back from the mouth and wide gullet into the stomach to
determine its shape and extent. Such a stomach as that of the
perch, ending blindly at the posterior end, and with the intestine
arising from near its anterior end, is said to be cecal. Sometimes
the posterior end of the stomach of the perch is found turned in,
like an inverted glove finger, occasionally to such an extent as
to be seen projecting from the gullet into the mouth. Observe a
white thread, the vagus nerve, distributed over the side of the
stomach.

7. Find a large tube, the intestine, arising from one side of
the stomacR. A short distance from its origin, the intestine has
several short, blind branches, the pyloric ceca. How many are
there and how are they arranged ? Make a small hole in the end
of one cecum ; insert the point of a blowpipe and inflate to show
the intestine and ceca.

8. Just beyond the ceca, on the posterior surface of the liver, is
a thin-walled sac, of a greenish or yellowish color, the bile sac.
If it contains bile, press on it to show the course of the bile duct
to the intestine. When empty, it often has a wormlike appear-
ance. Snip it open with the scissors, or prick it with a dissecting
needle to see the bile.

9. Trace the intestine to the anus, observing that it is held in
place by a thin, transparent membrane, the mesentery ; observe
the blood tubes in it ; tear this away in following the intestine ;
near the intestine find a small, deep red body, the spleen.

10. In the hinder part of the body cavity of the female is the
yellow, or pink, ovary (varying greatly in size, according to the
season). The two white spermaries occupy a corresponding posi-
tion in the male. In some fishes the ovary is single, in others it
is double. If double, the two ovaries unite in one tube, which
discharges the eggs, the egg tube, or oviduct. Trace the oviduct;
has it a separate outlet ? Sometimes the eggs in the ovary can
be discerned.

76 Practical Zoology.

11. Back of the oviduct or hinder part of the spermaries is a
small, pink (sometimes pale green) sac, the urinary bladder. Look
for its external opening back of the anus.

12. Gently separate the parts of the digestive tube, and remove
any fat that is in the way. Make a diagrammatic sketch of the
digestive organs as seen from the ventral aspect, showing and
labeling- the stomach, intestine, ceca, and the anal opening.

13. Turn now to the pericardial cavity and examine the heart.
The red, angular portion of the heart, which in the natural posi-
tion of the fish lies lowest and hindmost, is the ventricle ; the
darker, more irregular portion lying (in the natural position)
above the ventricle, is the auricle ; the larger blood cavity back
of the auricle, and extending across the body cavity, above the
false diaphragm, is the venous sinus ; in front of the ventricle is
the light-colored conical arterial bulb. This narrows forward into
an artery which gives off branches on both sides, one to each gill.
Make a drawing of the heart and arterial bulb. After passing
through the gills, the blood tubes unite to form the dorsal aorta, which
passes backward just underneath the spinal column. From above
the gills branches also run forward to the head. Cut away and
remove the liver, stomach, intestine, and" ovary (or spermaries).

14. In the dorsal part of the body cavity is the air bladder.
Carefully scrape away some of the thin peritoneal covering and
note the thin, transparent wall of the air bladder itself Scrape
away as much as possible of the peritoneum covering the air
bladder, in order to see if there are any blood tubes in the walls
of the air bladder. Make a puncture in the center of the air
bladder. What is the result ? Slit the air bladder along most of
its length and explore its extent and relations. Except on its
ventral surface it is attached to the inside of the walls of the
body cavity.

15. Dorsal to the air bladder, extending along the roof of the
body cavity, are slender, dark red bodies, the kidneys. With
the forceps tear away the false diaphragm and as much as possible
of the air bladder. This should disclose the most distinct part of

Pisces. 77

the kidney, lying anterior to the air bladder and dorsal to the
gullet. See if you can trace the kidneys to the urinary bladder.

1 6. If the mouth and gill covers are not already widely
stretched, loosen one or both tacks and set them farther out.
Examine the branchiostegal membrane and its supporting rays.
Look into the mouth to see the relations between the gills, gill
covers, and gullet. Note also the position of the tongue. Cut
forward and inward on each side between the gills and the gill
covers till the two cuts meet in front of the tongue. Again
examine the gills from the front. Pull up the tacks and press the
ventral ends of the gills toward the roof of the mouth. Study the
action of the joints in the gills. What is the use of the gill rakers?

Observe, where the gills unite above and below, patches of
closely set teeth, the superior and inferior pharyngeal teeth. The
bones supporting these teeth, above and below, are the pharyngeal
bones. Again depress and raise the lower ends of the gills, ob-
serving how the pharyngeal teeth are brought together. What is
the probable use of these teeth, and what is the work done by the
teeth previously examined?

Remove the gills by cutting the thin membrane back of them,
between the isthmus and their ventral ends ; above, cut close to
the base of the skull.

17. Examine the bones in the posterior border of the gill
opening ; these are together called the pectoral arch. Cut away
the flaps of the body wall bearing the fins.

18. Note also the bones supporting the pelvic fins; these are
considered as representing the pelvis. In the higher fishes the
pelvis is fastened to the clavicle ; in the lower fishes it is separate
from the rest of the skeleton and embedded in the flesh. How is
it in the specimen you are studying? Carefully remove the pelvic
fins, with the bones which support them ; examine and describe
them, after scraping away all muscles and other soft tissues.

19. Hold the fish in the left hand, with its back up and it?-
head away from you ; insert the point of one blade of the scissors
at the base of the caudal fin and cut the skin forward, passing t<>

jS Practical Zoology.

the left of the dorsal fin and on to the head. Remove the skin
of this side, carefully leaving the white muscles beneath undis-
turbed ; scrape part of the skin clean on the inside ; note the
arrangement of the scales as seen on each side of the skin ; look
also for traces of the lateral line on the inside of the skin. Hold
the skin up and look through it toward the light, alternately
stretching and shortening it, noting especially the lateral line.
Roll the skin lengthwise, with the scales outermost, to see how
the epidermis passes from one scale to another.

20. Observe the parallel transverse markings on the muscles
along the body.

2 1 . Cut and scrape away all the muscle of this side of the body
down to the bones, and make out the central backbone, with its
bony projections above and below. Bend the dorsal and anal fins
from side to side, to show the bones which support these fins and
the relation of these fin supporters to the projections of the
backbone.

22. Break across the backbone under the center of the second
dorsal fin, and remove one piece, or vertebra, of the backbone ; clear
away all muscle and other tissue, and make out the following parts : —

a. The central body, or centrum, shaped like an hourglass
and hollowed at each end.

^. Two projections extending upward, soon uniting to form
one spine, the neural spine.

<r. The archway formed above the body of the vertebra is the
neural arch.

d. A similar arrangement below, forming the hemal arch and
hemal spine.

Make a drawing of this vertebra as seen from the side ; another
as seen from the front.

23. In like manner remove and study a vertebra from a point
opposite the center of the first dorsal fin, with the ribs attached
to it. What are the differences between these two vertebrae ?

24. Thoroughly clean the last vertebra, and study carefully its
relations to the caudal fin.

Pisces. 79

25 . Observe the white spinal cord in the tube formed by the neural
arches above the bodies of the vertebrae. This is the nerve tube, or
neural tube ; note also the blood tubes in the corresponding hemal
tube, below.

THE BRAIN OF THE FISH.

Cut off the head ; clear away the muscles at the back of the
head ; carefully slice off the top of the skull with a strong, sharp
knife ; with extreme care cut away the roof of the brain cavity ;
a mass of loose, gray tissue covers the brain, which is of a white
or pinkish color; cautiously pick away this loose tissue, using a
small syringe, or medicine dropper, to wash away the loosened
matter. Make out the following parts of the brain, beginning at
the posterior end : —

1. The cut-off end of the spinal cord.

2. The widened part of the spinal cord, where it passes under
the hinder part of the brain, is the spinal bulb.

3. The hinder, undivided part of the brain is the cerebellum.

4. In front of the cerebellum are the two large, rounded optic
lobes, forming the widest part of the brain.

5. In front of the optic lobes are two oval masses which meet
in the middle line; these are the cerebral hemispheres, and to-
gether they constitute the cerebrum.

6. Observe the olfactory lobes tapering forward in front of the
cerebral hemispheres; from these trace the olfactory nerves to
the nasal cavities.

Make a drawing of the brain as seen from above, naming all
these parts. Cut open one of the optic lobes and note that it is
hollow ; push the eyes outward and find a white cord extending
inward and backward from each. These are the optic nerves.

THE MUSCLES OF THE EYE.
I. Cut away the upper part of the eye sockets and find in each
a muscle extending outward and backward from the anterior part
of the socket to the top of the eyeball. This is the superiof
oblique muscle.

8o Practical Zool

ogy-

2. Another muscle coming from the posterior part of the socket
will be seen passing forward to be attached under the oblique
muscle. This is the superior rectus. Make a drawing showing
these muscles. The other eye muscles may be more easily ex-
amined from beneath.

If the under surface of the skull of the specimen previously
studied be not injured, it may be used ; otherwise, cut off the
head of another fish, and cut away completely the lower jaw and
the floor of the mouth. Move the gill covers in and out to show
more clearly the thin plates of cartilage between the eyes and the
roof of the mouth ; with scissors slit in the middle line the tough
membrane lining the roof of the mouth, and strip it out to the
sides. Observe a muscle running outward from each side of the
base of the skull to the corresponding gill cover. Cut these at
their inner ends and turn them outward. With scissors cut away
the cartilages covering the under surfaces of the eyes.

3. Observe a muscle passing outward from the front part of the
socket to the eyeball, the inferior oblique muscle.

4. The muscle running forward close to the partition between
the eyes is the internal rectus.

5. On the under surface of the eye is the inferior rectus.

6. Attached to the hinder border of the eye is the larger ex-
ternal rectus. Note carefully the origin of each of these, theii
place of insertion on the eyeball, and their change of shape in
their course ; consider the effect of each on the eye.

Observe the thin-walled sweUings at the sides of the base of the
hinder part of the skull ; cut into these ear capsules and find in
each a membranous sac, the vestibule of the ear. In this sac
lies the " ear bone " or otolith. Find the white optic nerve arising
from the inner surface of the eyeball ; with a sharp knife cau-
tiously cut away the base of the skull and trace the optic nerves to the
brain ; demonstrate that they cross each other, the optic nerve from
the right eye entering the left half of the brain, and vice versa.

Make a drawing showing this view of the brain and eyes ; open
one of the eyes and remove the spherical crystalline lens.

Pisces. 8 1

Topics for Reports. — The Sources, Methods of Capture, and
the Commercial Importance of Food Fishes, — such as Codfish,
Mackerel, Flounder, Halibut, Herring, Shad, Sardines, Whitefish,
Lake Trout, Catfish, Carp, Buffalo, etc. Fish Hatcheries. The
Salmon Industry. Life History of a Salmon. United States Fish
Commission. Caviar. Isinglass. Cod-liver Oil. Fish Oil.

Read American Natural History y Hornaday.

CHAPTER IX.
AMPHIBIA.

FIELD STUDY OF FROGS.

Clad in rubber boots, the student can visit the frogs at theii
home. Walk along the bank of a creek, or wade through a marsh.
Try to " see the frogs before they see you." But if they see you
first and jump or swim away, try to follow them up and see where
they go. Do they soon reappear? How does their color suit
their surroundings? Would you suggest a more suitable color?
What seems to be the main idea in the colors they show ? What
reason for the difference of color of the dorsal and ventral sur-
faces? What enemies has the frog that would discover it from
above? How does its dorsal color serve it? Compare its color
with that of its surroundings. Why should a frog be white
beneath? What enemies has a frog that would see it from
beneath? What effect would the white color have? Suppose
the frog were dark below ; would it make any difference in the
ease with which it could be seen from below? Suppose it were
spotted over the ventral surface as it is over the dorsal surface?
When a frog is floating, how much is out of water? What parts
of it are out of water? In the spring watch the frogs that con-
gregate in ponds. Do they all croak? If not all, which ones do
the croaking ? Watch to see how the eggs are laid. What are the
eggs like? How are they placed? In still water or in a current ?
In deep water or shallow ? Do any animals eat the eggs ? How
long does it take for the eggs to hatch? Take the temperature
of the water and see if this makes any difference. Do the eggs all
hatch nearly at the same time, or is there considerable difference ?
Do many of the eggs fail to hatch ?

82

Amphibia. 83

Again in the fall study the frogs when they gather once more
along the banks. See if you can find any of them in the act of
diving into the mud. Mark carefully some of these places, and
watch to see if the frogs come out again. Some very slight cover-
ing of leaves or sediment may serve to show whether or not the
frog has come out. How deep do they go? Do they change
their depth or position during the winter? What is the tempera-
ture of the mud at this time? How cold does the mud at the
bottom of creeks and rivers become during the coldest part of
winter ? Does it vary much during the winter ?

LABORATORY STUDY OF THE LIVE FROG.

1. Put a live frog into a tub of water and study carefully its
mode of swimming and floating.

2. Notice how the frog sits when at rest. Make drawings of
the live frog in the sitting posture.

3. What has the frog in common with other animals that jump
well?

4. Watch closely the frog's breathing, paying especial attention
to the throat, nostrils, and sides.

5. Touch the eyeball with a pencil, and note what follows.
Note the motions of the eyehds. Note the color of the frog's
eyes. What is the shape of the pupil?

6. Test the frog's sense of hearing.

7. What does the frog eat, and how does it take its food?

8. Look for slight pulsations near the end of the backbone on
each side, near the anus. These are the beatings of the lymph-
hearts.

9. Keep one frog in the light and another in the dark and com-
pare their colors after an hour. Vary the color surroundings to
see whether they affect the color of a frog.

EXTERNAL FEATURES OF THE FROG.

Kill a frog by wrapping it in a towel or piece of cloth of any
kind, and moistening the latter with chloroform ; or put a tea-

84 Practical Zoology.

spoonful of ether in a fruit jar nearly full of water, immerse the
frog in it, and cap the jar.

1. Has the frog a neck? Find the division between the head
and the body by bending the parts and feeling for the joint.

2. Back of and below each eye is an oval area, the membrane
of the eardrum, or tympanum.

3. The fore limb consists of the arm, forearm, and hand.

4. The hind limb consists of the thigh, leg, and foot.

5. Count the fingers and toes.

6. What differences are there between the fore and hind limbs?

7. Open the mouth, seize the tongue with the forceps and draw
it forward ; observe that it is attached in front, but free behind.
How is such a tongue used ?

8. Look closely for teeth. Where are they?

9. Pass a bristle tipped with sealing wax into one of the nostrils.
Where does it enter the mouth ?

10. Make a small opening in one of the tympanic membranes,
pass a bristle through this opening, and look for its appearance in
the mouth. The opening through which it appears is the Eusta-
chian tube.

11. The mouth narrows back into the gullet.

12. In the back part of the floor of the mouth is a small slit,
the glottis, leading to the lungs.

13. Compare the colors and markings of the upper and lower
surfaces of the frog ; draw dorsal and ventral views of the dead
specimen, naming all visible parts.

Use Jordan's Manual of the Vertebrates for finding the names of
any amphibians.

DISSECTION OF A FROG

I. Lay the frog on its back in a dissecting pan. Stretch out the
fore limbs close to one end of the board and tack to the board
through the hands ; then stretch the hind limbs well back and out
and tack the feet so the body will be firmly held. Common carpet
tacks can be set firmly enough by pressing with the thumb, and
will not need hammering. With forceps pinch up a fold of skin

Amphibia. 85

near the pelvis. With scissors snip through the skin in the middle
line. Holding the edge of the skin with the forceps, sUt the skin
from the pelvis to the chin. Loosen the skin wherever it adheres
to the underlying tissues, and turn it back. Cut outward in the
middle of each flap of skin, and pin out if necessary to keep it out
of the way. Now cut through the muscular wall of the abdomen in
the same way, but be careful to keep to one side of the middle line,
and thus avoid cutting the central blood tube. Be also especially
careful to Hft the edge of the cut with the forceps, and watch closely
the lower point of the scissors to see that none of the abdominal
organs are injured. When the breastbone is reached, raise it to
see the heart. Now cut through the breastbone a little to one side.
Loosen the tacks in the hands and set them farther out to expose
the organs ; tack out the flaps of the abdominal wall. Keep the
specimen covered with water; renew the water if it becomes
turbid.

2. Covering most of the internal organs is the dark liver, con-
sisting of several lobes ; note how many lobes there are and how
they are arranged. Slip the handle of the scalpel under the pos-
terior border of the liver and tip it forward. Observe the bile sac,
a dark, usually bluish, spherical sac, connected with the liver.

3. Between the lobes of the liver at its anterior edge is the
reddish heart. It is inclosed in a very thin sac called the peri-
cardium. Pinch this up with the forceps, cut through it, then
remove most of it. The heart consists of two auricles at the base,
and the single ventricle at the apex, or posterior end. In a freshly
killed frog the heart often may be seen beating. Time its pulsa-
tions. Running forward from the ventricle is the main artery.
This divides into two branches, right and left, each of which has
three subdivisions : —

a. To the head, the carotid artery.

b. To the body generally, the aorta. The two aortae unite in
the posterior dorsal part of the body cavity.

c. To the lungs and skin, the pulmo-cutaneous.

What is the effect of applying gentle heat to the heart, as by

86 Practical Zoology.

breathing on it? Touch it with the point of the forceps. Does
this affect it?

4. Push the liver to the right and expose the pale stomach.
Use the blowpipe as a probe and push it back through the mouth
into the stomach. For this it may be necessary to lift the anterior
end of the board. Looking back into the mouth, the puckering of
the gullet may be seen. Are the mouthfuls that the frog swallows
small or large, relatively ? What is the real width of the gullet ?

5. At the posterior end of the stomach begins the intestine;
carefully trace it throughout its course.

6. The widened portion of the intestine near its end is the
cloaca. The external opening is the anus.

7. The thin membrane that holds the intestine in place is the
mesentery. To what is it attached dorsally? In a freshly killed
specimen blood tubes may be seen in the mesentery. The
mesentery is a double membrane and the blood tubes and
pancreas He between the two folds.

8. Turn the stomach and intestine forward; the pancreas
should be seen in the loop formed by the intestine and stomach.
It has the appearance of a yellow cord, and is often hard to dis-
tinguish.

9. At each side of the body cavity, usually concealed by the
lobes of the liver, are the two lungs. In frogs killed by chloro-
form the lungs are usually collapsed, that is, emptied of air;
hence they are small and dark-colored. If they contain air, they
may be very conspicuous and bright-colored. Find again the
glottis, or entrance of air from the floor of the mouth ; insert the
tip of the blowpipe and inflate the lungs. They are nearly plain,
hollow sacs, and not spongy all the way through like the lungs
of the mammals. Tie a thread tightly around the base of each
lung while it is inflated ; cut the lungs out and hang them up till
they are dry. Then cut one of them open and compare it with
the lung of a turtle similarly prepared.

10. Insert the scalpel handle under the posterior end of the
stomach, and tip it forward with the intestine and the liver. On

Amphibia. b7

each side of the cloaca is a flattened reddish body, the kidney.
The ventral face of each usually shows a yellowish streak.

11. Near the ventral surface of each kidney, in the male frog,
is the white, oblong spermary.

12. In the female, the ovary occupies a corresponding posi-
tion ; but often the ovaries are found greatly distended by eggs, so
much so that they occupy the larger part of the body cavity. The
eggs are black and white. The ovaries are held within the two
folds of the mesentery, hence, when distended with eggs, they
present a much folded and plaited appearance. The oviducts are
long, convoluted, whitish tubes, occupying considerable space in
the dorsal part of th-e body cavity on each side. With fine scissors
make a small slit in one of the oviducts near the posterior end,
and insert a dark bristle to find the opening into the cloaca.
Make a similar opening near the anterior end of the oviduct and
probe to find the opening by which the eggs enter the duct at its
free end in the body cavity near the base of the lung.

13. Connected with the ovaries and spermaries are usually
several fingerlike masses of yellow fat.

14. Close to the anterior end of the cloaca is the small, red,
spherical spleen.

15. In the extreme posterior end of the body cavity is the
urinary bladder. It is a thin, delicate sac, which is usually found
empty, and floats upward in the water like a mere fold of nearly
transparent membrane. Insert the blowpipe through the anus
and inflate. This should reveal its shape and size, if it has not
been perforated.

The Circulation of Blood in the Web of a Frog's Foot. — For
this get a frog with a pale web. Take a piece of shingle six inches
long and three inches wide. Cut a round hole, half an inch in
diameter, near one end of it. Wrap the frog in a wet cloth, with
one leg projecting, and tie it, thus wrapped, to the shingle. Tie
threads around two of the toes, and stretch the web, but not too
tightly, over the hole. Place the shingle firmly on the stage of a
microscope. Examine first with a low power. The large tubes

88 Practical Zoology.

which grow smaller by subdivision are arteries. The large tubes
which are formed by the union of smaller ones are the veins. The
finer tubes, forming a network in every direction, are the capil-
laries. They receive the blood from the arteries and pass it on to
the veins.

Put on a higher power, a one-fifth or one-sixth objective. Study
the little bodies floating in the blood. These are the corpuscles.

1. The colored corpuscles. The faintly colored elliptical cor-
puscles ; do they change their shape when pressed, as in turning a
corner ? What is the color of these corpuscles ? Mold a bit of
clay into the shape of one of these bodies.

2. The colorless corpuscles. The smaller, rounder, paler cor-
puscles, fewer in number and moving with a slower and more un-
steady motion along the sides of the channel, — what must be the
shape of these? Place a drop of frog's blood on a slide, cover
with a cover slip, and examine with a high power. Make careful
drawings of the two kinds of corpuscles.

THE NERVOUS SYSTEM OF THE FROG.

The nervous system is better seen in alcoholic specimens. Slir
the skin along the back from the snout to the anus ; with a sharp
knife cautiously cut away the top of the skull, and find ; —

1. Between the eyes, side by side, two elongated white bodies,
the two halves, or hemispheres, of the cerebrum. Observe two
small, pear-shaped bodies, the olfactory lobes, in front of the cere-
bral hemispheres. These taper forward into nerves running to the
nasal region ; these are the nerves of smell, or olfactory nerves.

2. Back of the cerebral hemispheres are the optic lobes, forming
the widest part of the brain. Prove that a white cord, the optic
nerve, connects each of these lobes with one of the eyes ; does
the optic nerve extend directly from each eye to the correspond-
ing optic lobe? Loosen and raise the brain from the front to
prove these points.

3. Extending backward from the under side of the optic lobes
is the spinal bulb.

Amphibia. 89

4. The spinal bulb narrows and becomes the spinal cord. Trace
the spinal cord back into the spinal column, cutting away the part
of the backbone that covers it.

5. In the body cavity find nerves emerging from the sides of
the spinal column, hence called the spinal nerves. Find that
several of these, after running backward, unite to form one large
nerve. Trace the nerve down between the muscles of the thigh ;
this is the sciatic nerve.

REFLEX ACTION OF THE FROG'S SPINAL CORD.

Chloroform a frog as directed on page 8^. As soon as it becomes
insensible find, by bending the head, the joint between the head
and the backbone ; lay the frog on a board, and quickly thrust
the blade of a knife through the body at this joint, and completely
sever the spinal column and spinal cord. This is essentially the
same as cutting off the head. Run a wire into the brain cavity and
stir it about in order to destroy the brain. In a few minutes hang
the frog by a hook through the jaw.

1. Pinch the toes; what follows? Repeat the experiment sev^
eral times. Pinch the skin near the anus.

2. Slit the skin along the back side of the thigh ; tear apart the
muscles, and find the sciatic nerve ; with a sharp pair of scissors
(while watching closely the foot) sever this nerve ; what takes
place ?

3. Hang up as before, and pinch the toes of each foot; what
difference is now observed?

4. With the forceps alternately pinch the two ends of the
severed sciatic nerve ; what takes place as these two ends are
pinched?

5. Run a wire down the spinal column, twisting it about to
destroy the spinal cord ; what occurs while this is doing ?

6. Pinch the toes as before ; what results ?

7. Again pinch the end of the sciatic nerve, still connected
with the parts below, being careful to pinch a little lower than
before.

pO Practical Zoology.

The Action of a Frog's Muscle. — Kill a frog thus : Into a fruit
jar of water put a teaspoonful of ether ; imnierse the frog in it and
cap the jar. As soon as the frog is motionless cut off its head and
run a wire down the cavity of the spinal column, to destroy the
spinal cord. Cut through the skin around the base of one of the
thighs, and strip off the skin from the whole of the limb. Note
that the muscles are of a pale color. The muscles of a frog's
thigh are nearly the same in number and arrangement as in man.
Examine more thoroughly the calf muscle ; the end by which it is
attached below is its insertion, and the upper attachment is its
origin. The white cord in which it ends is its tendon. This ten-
don is often called the " heel cord," or Achilles' tendon.

Sever the limb from the body at the hip joint. Separate the
muscles along the outer back part of the thigh, and find the white,
threadlike sciatic nerve. The nerve must be handled with great
care ; it must not be pinched or dragged. Carefully separate it
from the surrounding muscles, and turn it down upon the calf
muscle. Cut away all the muscles of the thigh, being careful not
to touch the nerve where it runs down by the knee. Sever the
heel cord below the heel, and separate the calf muscle from the
rest of the leg, leaving undisturbed its attachment above; just
below the knee cut away the shin bone, with all the muscles of the
leg except the calf muscle.

There should now remain the thigh bone, with the sciatic nerve
mnning to the calf muscle suspended below. Fasten the thigh
bone to some support, such as a clamp on a retort stand. Attach
a small hook to the tendon, and suspend from it a slight weight,
such as a small key.

Such a preparation is called a nerve-muscle preparation. It
should frequently be moistened with a .7 per cent solution of
common salt in water, called normal saline solution.

Now take a sharp pair of scissors, and snip off the shortest possi-
ble portion of the upper end of the sciatic nerve. If the muscle
is closely watched at the time when the nerve is cut, it will be
seen to thicken and shorten, and to lift the weight. If the muscle

Amphibia. 9 1

be held between the thumb and finger while the nerve is pinched
(and the scissors are the surest pinchers), it will be felt to harden.

This experiment should be repeated, varying the weight, until it
is made very clear that when the nerve is stimulated the muscle
shortens (which is the most important fact about the action),
thickens, and grows harder.

Observe the thin, transparent membrane covering the muscle,
the muscle sheath. Tear the muscle to pieces, and note its fibrous
structure. Put a bit of the muscle in a drop of water on a slide,
and cover with a cover slip ; examine first with a low, and then
with a high, power, to see the cross markings of its finest fibers.
This kind of muscle is called striped or striated.

PREPARATION OF A FROG'S SKELETON.

Remove the skin and all the soft tissues. If you have a speci-
men that has been used for dissection, of course the anterior Hmbs
vvill come apart where the breastbone was severed. Remove the
soft tissues mainly by means of the scissors, being careful not to
cut too close to the joints. If the work is not completed at once,
return the specimen to the water. Renew the water frequently
and do not allow it to " get bad." If the hgaments decay, the
bones will fall asunder and make great difficulty on account of
their number and smallness. Do not boil the skeleton, or put it
into alkali. These processes may be useful for larger skeletons,
btt are not good for such small ones as that of the frog.

MOUNTING A FROG'S SKELETON.

Get a piece of stiff, dark cardboard about six by eight inches.
Before mounting the skeleton on the card, get it nearly dry by
placing it on blotting paper or on cloth. If it is too dry, it will be
brittle ; if too wet, it will stain the card. Draw a fine pencil hne
along the middle of the card. Place the skeleton along this line
and double up the limbs as if the frog were in the resting position.
A block of cork must be placed under the anterior end of the
spinal column to hold it up to the level of the skull. A small

g2 Practical Zoology.

cork wedge should be placed between the jaws. The skeleton is
to be sewed to the card with a single thread of the color of the
bones. The bones are to be held by loops that pass up from
the under side of the card, around the bone, and back through the
same hole. A// holes are to be punctured from the upper sur-
face of the card, and are better made with a pin slightly larger than
the needle used in sewing. It is important to determine exactly
where each bone is to lie, so that the hole may be made exactly
under the middle of the bone. Now puncture holes as directed
under the front and hind angles of the jaws, and under the pelvis
beneath the hip joints. After securing the head and pelvis, deter-
mine carefully where the bones of the limbs are to rest. Pass
loops around near each end of the longer bones, but a single loop
in the middle will serve for the short bones of the fingers and toes.
If the skeleton is from a specimen used for dissection, the breast-
bone will have been severed. Bring the cut ends together and
sew firmly in place. The shoulder blades should meet in the
middle line a short distance back of the skull. Print the label
" Skeleton of a Frog " at the foot of the card and write your name
on the back of the card.

To preserve the skeleton get a shallow box, such as a shallow
cigar box. Fit the card to the box and tack it to the bottom. A
good plan is to remove the wooden cover and replace it with a
glass lid. Paste strips of paper or suitable cloth along the edges,
and the case will exclude dust.

THE FROG'S SKELETON.

1. Note how open and Hght the skull is, and how easily the
bones are cut.

2. Count the parts of the spinal column ; these are the verte-
brae. The long bone terminating the spinal column is the urostyle.

3. Observe the long bones of the pelvis, parallel with the uro-
style. What makes the frog humpbacked ?

4. The fore limb has, in the upper arm, the humerus ; in the
forearm, the radius (same side as the thumb) and the ulna ; in the

Amphibia. 93

wrist are several small bones, the whole collectively called the
carpus ; in the hand are the digits.

5. The hind Hmb has, in the thigh, the femur; in the leg, a
bone which shows, by grooves near its ends, that it is formed by
the union of the two bones corresponding to the tibia and fibula
of man ; the several small bones of the ankle are together called
the tarsus ; the bones of the toes are the digits.

6. Are there any ribs?

STUDY OF A TADPOLE.

Get a number of frog's eggs and place them in a jar of water.
If many eggs are placed in a small amount of water, the eggs are
not likely to develop well. Set different jars in different places
with regard to light and heat, and note any differences in results.
It is best to have some aquatic plants in the jar, especially after
the young have hatched out. How long before the tadpole within
the egg begins to move ? How long till it breaks away from the
egg mass? How early do the gills show themselves? What are
the parts of the tadpole? What is the shape of the tail? What
is its use? How is it used? How early do legs appear? Which
legs develop first? Is there any reason for this? Are tadpoles
relatively active or inactive ? Do they move much " of their own
accord"? Or chiefly when they are disturbed? Does the tail fin
have supporting rays like the fin of a fish? What do tadpoles eat?
How do they eat? Have they teeth? Is the growth slow or
rapid ?

Put a tadpole in a watch glass of water under the microscope,
with a half-inch or two-thirds-inch objective, and watch the cir-
culation of blood in the gills. What becomes of the gills? Watch
the sides of the body for a hole where water escapes. Where is
it? Why is the tadpole not symmetrical in this respect? What
becomes of the tail as the tadpole becomes a frog?

Examine a dead tadpole to see if there are teeth. What is the
size of the mouth in proportion to that of the adult ? Look again
for the hole on one side of the body. Are there ever limbs con-

94 Practical Zoology.

cealed? Open the body cavity. Is the digestive tube long or
short as compared with that of the frog? What reason for this?
Can you find any traces of gills? Of lungs? Is there a backbone?
Do you find a brain and spinal cord ?

Make a series of drawings showing the different stages of
development.

Topics for Reports. — Frogs as Food. The Axolotl. Value of
Toads. The Tree Toad.

Read American Natural History^ Hornaday.

CHAPTER X.
REPTILIA.

FIELD STUDY OF SNAKES.

First try to rid yourself of prejudice against snakes. It is not
necessary to handle them, and poisonous snakes are now rare in
most places. If the snake has been frightened by you, try to learn
how he became aware of your presence. Was it through sight,
hearing, or some other sense? Is there any plan in his escape?
Does he seek shelter, or simply move away from you? Are his
colors such as to aid him in escaping enemies? Why are we
usually surprised when we happen upon a snake? Is the snake
also surprised?

Study the snake's mode of locomotion. Have you ever seen
the trail made by a snake, as in a dusty road? Does the nature
of the surface make any difference in the ease with which it
travels? Does a snake ever crawl otherwise than in a wavy line?

If you happen upon a snake that has not already discovered
you, watch it. Try to find out what it is doing. Especially if you
find a snake eating, take time to learn how it eats. Does it kill
the prey before swallowing it? Does it chew its food? If you
kill a snake, or see one killed, where you cannot take it home,
find out, if possible, what it has been eating. If the snake is much
bulged out at, or in front of, the middle, you may suspect that it
has just swallowed a meal. Do snakes " charm " birds?

Have you ever found a shed skin of a snake? If you find one,
bring it to the class. How much of the external markings is
shown on the shed skin? Can all snakes swim? If you get a
garter, or other snake, not a water snake, and do not wish to keep
it, throw it into water to see if it can swim. Will the body of a

95

96 Practical Zoology.

freshly killed snake sink or float ? Do snakes dive ? How do snakes
strike, when capturing prey or in self-defense? How far can a
snake strike? Let it strike some object, for example a stretched
paper, to show with what force it strikes. Do you know of any
case where a snake, unmolested, pursued a human being?

LABORATORY STUDY OF A LIVE SNAKE.

A snake may be kept in a large glass jar, but it is better to have
a shallow box, with glass lid. Test the snake's vision. Does it
see well? Does it see small objects as readily as large ones?
Does it notice slow motions as well as quick ones? Test its sense
of hearing. Try music. Does the snake protrude the tongue? If
so, for what purpose ?

Liduce the snake to strike ; study the position and mode of
striking. Study the process of respiration in the snake. Is there
a pause ? What movement is first after the pause ? Compare the
snake's respiration with your own. Does a snake need much or
little oxygen as compared with man ?

How soon does a snake become hungry after a meal? Offer
various articles of food. Does a snake drink? Offer it water in
a shallow dish from time to time. Will a snake eat a dead animal ?
Do snakes of different kinds in the same box offer to molest each
other ? Do snakes ever eat snakes of any kind ? Do snakes sleep ?
At what times are they most active ? When least so ? Watch a snake
to see the shedding of the skin. At what point does the skin begin
to loosen ? How is the skin peeled off? What is the condition of
the snake before shedding ? What is the appearance and condition
after shedding? How often does a snake shed its skin?

EXTERNAL FEATURES OF A SNAKE.

Examine the scales ; observe their relation to each other and to
the skin. A scale having a ridge running lengthwise in the middle
line is carinated; if there be no such ridge, the scale is called
smooth. How many rows of scales are there, not counting the

Reptilia. 97

wide ventral plates below? It is usually easier to keep the count
by following the row of scales obliquely across the body.

Use Jordan's Manual of the Vertebrates for finding the names
of any reptiles found in your vicinity.

DISSECTION OF A SNAKE.

Get a large snake, a paper of tacks, and a board as long as
the snake. The board should be of dressed soft pine so that the
tacks may be inserted by the thumbs ; a hammer should be un-
necessary, tho if the spinal cord is not destroyed, the body may
pull with considerable force, and it may be desirable to drive a six-
penny nail firmly through the tail just back of the anus. Lay the
snake on its back, with the head at one end of the board. Push the
point of a tack into the mouth at one side, and drive it through the
upper jaw, leaving the lower jaw free. Repeat with the other side.
Stretch the snake out straight, and tack through the tail, just back
of the vent. With the forceps pinch up a fold of the skin of the
throat, and cut through it with the scissors. The greatest danger is
that of cutting into the air sac, which, when distended, fills most of
the space of the body cavity. To guard against cutting into it push
the handle of a small spoon, or the bowl of an " after-dinner coffee
spoon," along under the skin ahead of the scissors so the lower
point of the scissors shall be constantly guarded. Continue the cut
back along the middle line of the ventral wall, being very careful
not to cut anything within. As the cut proceeds, stretch the skin
out at the sides, and tack it down every two or three inches. Cut
away the thin membrane which extends across from the ribs on
each side, avoiding blood tubes.

1. With forceps seize the lower jaw and pull the mouth open.
Note how dilatable the mouth is, and how loosely the lower jaw is
hinged to the upper ; note, also, that the right and left halves of
the jaws do not unite in front. Examine closely the teeth, their
shape and arrangement. In what direction do they point ?

2. Seize the tongue, and draw it forward from its sheath in the
floor of the mouth. Observe its black, forked tip.

98 Practical Zoology.

3. Above the tongue find a small opening, the entrance to the
windpipe. It is called the glottis.

4. Take six inches of glass tubing half an inch in diameter ; slip
over the end of this a piece of rubber tubing a foot long; this will
enable you to see the effect while you are inflating. Insert the
glass tube into the throat through the mouth ; pinch the walls of
the gullet closely around the blowpipe, and inflate the wide gullet
and stomach.

5. For inflating the lung, a tube with a small point is better;
draw out a small glass tube, and connect with a rubber tube ;
insert the point in the glottis, and inflate. This locates the pink
lung, with its posterior, thin-walled extension, or air sac. How
far back does the air sac extend?

6. Trace from the glottis to the lungs the ringed windpipe, or
trachea. Only one lung is developed ; look for the rudiment of
the other.

7. In a freshly killed snake the heart will be noticed on account
of its beating ; the part of it farthest from the head is the ventricle ;
nearer the head find two parts, the right and left auricles. These
two contract at the same time, just before the contraction of the
ventricle. The heart is in a thin sac, the pericardium ; pinch up
a fold of this with the forceps, and cut into it, and remove that
part of it covering the heart, very carefully avoiding blood tubes.

8. Find a blood tube arising from the ventricle just between
the auricles, and passing forward between them, curving around
over the gullet to the posterior part of the body. This is the main
artery, or aorta ; look for its branches running to the head.

9. Look also for an artery running to the lung, the pulmonary
artery.

10. Find several veins, of a darker color than the arteries,
leading to the heart.

11. Alongside the stomach is a dark red body, the liver ; a large
vein runs along its surface.

12. Backoftheliver is the dark bile sac ; the ducts from the liver to
the bile sac, and fi-om the bile sac to the intestine, are not easily seen.

Reptllia. 99

13. Just posterior to the bile sac is the spherical, reddish
spleen.

14. Closely following the spleen is the pale, roundish pancreas ;
the duct by which its secretion is conveyed to the intestine is hard
to find.

15. Clear away any masses of fat that may hide organs in the
posterior part of the body, and expose the intestine from the
stomach to the anal opening.

16. The enlargement of the intestine near its termination is
the cloaca. Again inflate the stomach ; does this also inflate the
intestine ?

1 7. If the specimen is a female, there may be found, in the
posterior part of the body, the whitish ovaries, with a row of white
eggs ; from the ovary, the oviduct, a slender pinkish tube, extends
back to enter the cloaca. Are the ovaries of the two sides opposite
each other? Slit into one of the oviducts near the cloaca; insert
a bristle and find where it enters the cloaca.

18. In the male the white spermaries have similar positions.
Their ducts are called sperm ducts.

19. Farther back than the ovaries are the dark red, elongated
kidneys. Describe them. Trace their ducts, the ureters, to the
cloaca.

20. Count the ribs of one side.

21. Draw the points of the forceps quickly along the muscles
over the ribs; note the shortening of the muscles that follow;
such action of the muscles is wholly involuntary (as the brain now
has no connection with the body) , and is called reflex action of the
spinal cord. It is the same kind of action as that seen in the case
of a chicken with its head cut off.

PREPARATION OF A SNAKE SKIN.

After finishing the dissection according to the above directions,
completely remove the skin, retaining only the skull. Thoroughly
rub the inside with arsenic. Make a wooden body, around
which wrap a little cotton, and sew up ^s neatly as possible. Try

lOO Practical Zoology.

to preserve the original size of the snake. Lay the prepared skin
on a shelf till it is drv. Keep it in a dust-proof case.

Topics for Reports.— The Cobra. Other Venomous Snakes. Do
Snakes swallow their Young ? The Python. The Boa Constrictor.

FIELD STUDY OF TURTLES.

The student soon learns that the common pond and mud turtles
are shy creatures. Along ponds and streams one may see them
on logs and stumps. But one must go quietly and cautiously, or
he will scare them all into the water. On which sense do they
rely, sight or hearing, to discover enemies ? Watch their method
of getting into the water. Do they soon return, if the observer is
quiet? What seems to be their object in thus perching on logs?
Find out, if you can, what they eat, and whether they eat on land
or in water. Do they require much or little food ?

Can you find where and how they lay their eggs? Do they
care for the eggs? How long does it take the eggs to hatch?
Do the parents care for the young? What are the prevailing
colors of turtles? How do these colors compare with their sur-
roundings ?

STUDY OF A LIVE TURTLE.

Watch a turtle walk on a floor. Does it walk or crawl ? Is the
body lifted above the surface or does it drag? How are the limbs
used? Put the turtle in water and find out how it swims. Does
it use the front feet alternately or at the same time ? Are the feet
webbed? Does it swim rapidly or slowly? Does the turtle dive?
If there is mud at the bottom, does it attempt to burrow into or
bury itself in it?

Feed the turtle and find what it likes best. Does it eat Httle
or much? Do turtles become tame in captivity? Do they recog-
nize those who care for them, and distinguish them from strangers ?

Can you see how the turtle breathes ? Can it stay under water
long ?

What parts of the turtle can be protruded beyond the margin

Reptilia. loi

of the shell ? How does it protect these parts ? Can any part of
the shell be moved, or is it wholly rigid ?

EXTERNAL FEATURES OF A TURTLE.

1. The upper part of the shell is the carapace.

2. The under part is the plastron.

3. Observe the large sections, or plates, marking the shell.
How many of these plates are there on the carapace ? How many
on the plastron ? How are they arranged ?

4. Study the motions of the head, legs, and tail ; observe the
scales on these parts.

5. Note the shape of the feet; for how many purposes does
the turtle use its feet ? Are the feet of all turtles alike ? Count
the claws ; compare the front and hind feet.

6. With a strong pair of pinchers seize the head, pull it well
out, and chop it off; examine the mouth; are teeth present? Is
there a tongue? Look for a third eyelid. Compare with the
pigeon in this point of structure.

DISSECTION OF THE TURTLE.

Saw through the bridge which connects the carapace and plastron
on each side. Carefully raise the plastron, and, keeping the blade
of the knife or scalpel close to its inner surface, cut away all its
attachments to the organs within, and remove it entirely.

1. In front are the bones supporting the fore limbs.

2. Behind are the bones of the pelvis, supporting the hind limbs.
Were these two sets of bones attached to the plastron ?

3. A thin membrane covers the internal organs ; through it the
heart may be seen beating. Cautiously avoiding blood tubes, cut
away this thin covering, and distinguish the following parts of the
heart : —

a. The large, hinder part, the ventricle.

b. In front, on each side, the two auricles.

c. Between the auricles are blood tubes, branching toward the

I02 Practical Zoology.

head. As in the frog, there are two aortae, the right and left,
which unite posteriorly.

4. Make out the following order of the heart's beat : —

a. The contraction of the blood tubes leading to the auricles.
d. The contraction of the auricles.
c. The contraction of the ventricle.

5. On each side of the heart appears the dark liver, consisting
of two main lobes, connected by a cross-band. Search the liver
to find the bile sac.

6. Under the left lobe of the liver is the stomach.

7. From the stomach trace the intestine to the transverse vent
under the tail.

8. Masses of eggs may be found in the ovary (if a female).

9. Find a large bladder near the pelvis.

10. Raise the liver to find the lungs ; pull forward the neck,
find the windpipe, and insert a blowpipe. By inflating, the lungs
may be better seen. When the lungs are fully inflated, tie a string
tightly around the windpipe ; carefully remove the lungs, and hang
them up to dry. When they are thoroughly dry and firm, cut them
across, and compare with the lungs of the frog and rabbit.

11. How does the turtle draw in its head?

12. How long does the heart beat after the head is cut off?

THE SKELETON OF THE TURTLE.

1. Clean away the muscles and all soft parts. Boiling loosens
the outer plates ; these are parts of the skin, and not of the skeleton
proper ; they are called the epidermal plates.

2. When these plates are removed from the carapace, there
appears a series of bones extending outward on each side ; these
are the ribs, very wide, and united by their edges. How many of
these flattened ribs are there?

3. On looking at the inner surface of the carapace, the series
of vertebrae will be found ; and attached to the sides of the bodies
of these vertebrae are the heads of the ribs.

4. Along the middle line of the outside of the carapace, between

Reptilia. 103

the/ ribs of the two sides, is found a series of bony plates ; these
are the enlarged and flattened projections of the vertebrae ; they
correspond to the spines which make the sharp ridge along the
backs of most vertebrates.

5 . Compare the bones of the pelvis and of the limbs with those
of the rabbit.

Topics for Report. — The Terrapin. The Hawkbill Turtle.
Tortoise-shell. The Loggerhead Turtle. The Green Turtle. The
Snapping Turtle. The Soft-shell Turtle. The Gopher.

Read American Natural History^ Hornaday.

CHAPTER XL
AVES.

OUTDOOR STUDY OF BIRDS.

The following set of questions is general and may be applied to
any bird that comes within our range of observation. The English
sparrow serves well for study, since — like the poor — it is always
with us. These studies should include a careful study of the
domesticated birds.

Place of Living. — Does the bird stay most of the time on the
ground or in the trees ? In open fields or in thickets ? In open
woods, or dense forest ? On dry soil, or along the water ? Is it
fitted for perching, running, swimming, wading, climbing, or for
what general kind of life ?

Flying. — Does it fly swiftly or slowly? Do the wings vibrate
rapidly as in the quail, or slowly as in a hawk ? Is the vibration
uniform, or do the wings make a series of rapid motions, followed
by a rest during which time the bird sails, as with the quail ? Is
the flight quiet as in owls,''or accompanied by a whirring sound as
with a quail ? Is the flight in comparatively straight lines, or in
loops or festoons, as with woodpeckers? Does the bird ever
" soar," or " hover " ? What is the use of the tail in flying? How
are the legs and feet held during flight ? Why do some birds fly
most of the time while others fly little? What characteristics have
the birds that spend much of the time flying? Name some of the
best flyers you know. Name some of the poorest flyers that live
near you.

Walking. — What birds really walk? Why do so many birds
hop, while on the ground, instead of walking? Do you know any

I04

Aves. 105

birds that prefer walking or running and seldom fly unless fright-
ened ? Is there any special adaptation of the feet in birds that
spend most of the time on the ground ? Compare the size and
strength of the legs in birds that Uve on the ground with those oi
ordinary perching birds.

Food. — What does the bird eat? How does it discover this
food? How does it secure it? Does it eat much or Httle? Has
it any special time, or times, of day (or night) for feeding? Give
particulars of the manner of feeding. Does it store food, or simply
get what is needed for the present? If stored, how and where?
Name any special adaptations for obtaining special kinds of food.
How do birds drink?

Sociability. — Do birds live singly, in pairs, or in flocks ? Do
any birds that live in pairs during the breeding season ever flock
at other seasons? Does the kind of bird you are studying mingle
freely with other birds, or does it keep aloof ? If they " meet by
chance," are they shy? Do they quarrel? Are they inclined to
be " quarrelsome " ? Does one kind try to drive another away?
Does the larger always defeat the smaller?

Nesting. — Does a bird habitually build in the same kind of
place? Is the place selected with reference to enemies? To
shelter? Do any prefer to rebuild in the same place? Of what
m.aterial, or materials, is the nest made? How is this material
obtained? How is it carried? How is it "handled" during the
building? Do both sexes share in the nest building? Is the size
of the nest, as seen from the outside, in keeping with the size
of the bird? Is the space inside in proportion to the body? How
many eggs are laid ? Are they arranged in any definite way ?
Their color? Size? Shape? Is the shell thick or thin? How
long from the time of beginning to "sit" till the young hatch out?
Does the male ever " sit " ? Does the male ever bring food to
the female while she is "sitting"? What proportion of the eggs
hatch? Do birds ever lay eggs in the nests of other birds? If so,
do they lay them in nests of the same kind of bird? Are the

io6 Practical Zoology.

young able to get their own food as soon as they are hatched, oi
are they helpless? How fully feathered are they when hatched,
and are the feathers the same in color and texture as in the
parents? Which do they more nearly resemble, the adult male, or
the female? On what are the young fed? Is food ever especially
prepared for the young? Do both parents bring food? Do the
young require much or little food? Are their eyes opened as soon
as they are hatched? How long till they leave the nest? Till
they can fly? Are they cared for after they leave the nest? Is
the nest a " home " ? Do the young return to the same spot? Do
they ever occupy an old nest? Do they use any of the material
of an old nest ?

Migration. — Make a list of the birds that you see remaining
here during the summer. Make another list of those that stay
with us during the winter. Why do some of these birds go south
in winter while others remain the year round ? Is the blue jay
any more warmly clad than the robin? Or is there some other
reason than mere ability to '' stand the cold " that leads one to
stay while the other migrates ? Do you see birds in the fall and
spring that are not seen here either in winter or summer? How
do you account for these facts? Make a list of birds that are
seen only during fall and spring. Do birds migrate singly or in
flocks ? Or in pairs ? Do you see in winter any birds that are
not here in the summer?

Songs. — How many objects have birds in using the voice?
How many distinct kinds of calls has this bird? Can this bird
be said to sing? Do birds have a language?

Care of Feathers. — How do birds arrange their feathers and
keep them in good condition?

Molting. — When do birds appear brightest and freshest? What
makes the difference? Are all birds alike in these changes?
Examine birds to find evidence of change.

Senses. — Can birds see well? Hear well? Experiment to
test their senses.

Aves. 107

i^ttitude. — Note closely the attitude assumed by the bird when
*t rest. In the case of tree birds observe whether they rest cross-
wise or lengthwise on a branch, whether erect or nearly horizontal,
whether they prefer large branches or small ones, etc. Where
und how do the different kinds of birds spend the night? What
birds are astir at night ?

Color. — Note the relation of a bird's color to its ordinary sur-
roundings. What differences in the color and markings of the
male and female? How do you account for these differences?

INDOOR STUDY OF BIRDS.

While the writer does not wish to encourage the caging of birds,
it may sometimes be profitable to keep a bird in confinement for
a time to study some of its habits that might escape observation
in the free bird. A pigeon or canary will serve very well for this
work. Suitable cages should be provided, and the bird should
be well cared for. Try to make the bird feel as much at home as
possible. Find what it prefers to eat, and learn its habits of eating
and drinking. Learn how a bird winks. How does it sleep?
How does it perch? Watch the breathing movements. Count the
respirations for a minute when the bird is not especially excited.
If possible, test the temperature of a bird by holding a cHnical
thermometer under its wing for a few minutes. (In this experi-
ment be careful not to let the bird knock the thermometer out of
your hands.) Close all the doors and windows and let the bird
fly about the room to see how it flies. Study the actions of the
wings and tail. Hold the bird by the body and when it flaps its
wings learn what you can of their action. Can you determine
definitely how the wing is moved in what we call the "down
stroke "? At what angle is the wing held during this stroke? In
the same way study the up stroke. Hold the bird above you and
below you, with the head toward you and with the tail toward
you, and note in which direction it fans the air most strongly.

In this work make use of canaries, parrots, and other of the com-
monly caged birds. Study the birds found in zoological gardens.

lo8 Practical Zoology.

To what extent, and in what manner, do birds evince emotion
such as anger, fear, etc. ? Try bringing close together cages con-
taining different kinds of birds. How much attention do they
pay each other? Try placing a mirror close to a caged bird.
Are birds affected by music ? By harsh or loud noises ?

If an owl can be captured alive, much can be learned from it.
Give it a dead bird or mouse. See how it eats. Watch to see
the pellets of hair and feathers that it ejects from the mouth after
digesting the soft tissues. If a swimming bird can be kept, one
may see how it swims. A tame duck may serve well for this.
Drop a dead bird into a pail of water. Does it sink ? Pluck the
bird and again drop it into the water. Does it sink or float?
Explain. How is it that birds keep so warm while flying in
very cold air, as in winter when it is below zero? Do birds have
parasites? Do they make effort to get rid of them? Can you
help the birds get rid of them?

EXTERNAL FEATURES OF A BIRD.

How to handle a Bird. — Feathers are delicate structures and,
if once crushed or broken, cannot be made over again. Never
stroke feathers unless necessary. Above all, never draw a feather
through the fingers. This ruins the texture forever. When needed
smooth the feathers and deftly rearrange those that are displaced
or twisted. When possible pick up a bird by the bill, not by the
legs or tail. To take a bird in hand, pick it up by the bill and
gently draw it into the other hand, back down. To lay it on the
table, draw it lightly from the palm upon the table. To examine
the tail feathers, hold the bird with its head toward you and with the
thumb and fingers of the two hands take hold of the base of
the tail and spread the feathers. Do not take hold of the tip of a
feather, and it is seldom necessary to take hold of any part but the
base of the quill. To examine the wing quills have the head of the
bird toward you, and, passing the thumb and fingers by the front
edge of the wing, hold the quills by their bases. Never pull a bird
backward on the table by the legs or tail.

Aves. 109

The Head.

1. The beak consists of the upper and lower mandibles; hold
the pigeon's head with one hand, and with the other take hold of
the tip of the upper mandible and see if it is movable.

2. Raise the upper eyehd, and look in the front angle of the
eye for the third eyelid ; seize the edge of this with the forceps,
and pull it backward over the eye.

3. Brush forward the feathers below and back of the eye to
find the ear opening; observe the pecuHarities of the feathers
which cover this opening.

4. Examine the nostrils ; open the mouth and insert the head
of a pin into the nostril, and probe, to discover its place of appear-
ance in the mouth.

5. With the forceps pull forward the tongue for careful exami-
nation.

6. Just back of the tongue is the opening, the glottis, of the
windpipe, or trachea.

7. The mouth continues backward to become the gullet.

The Legs.

1 . Feel of the parts, beginning close to the body, to be sure to
find the first division of the limb ; this is the thigh, or " second
joint."

2. Below this is the tibia, or " drumstick."

3. The next division is the tarsus ; it is a consolidation of sev-
eral bones that were distinct in the young bird ; this part of the
bird's leg, then, really corresponds to the tarsus and metatarsus of
the human foot, or that part between the ankle and the toes.
Where, then, is the true heel ?

4. Bend and extend the toes to find how many bones there are
in each.

5. The scales on the front of the tarsus are called scutella ;
hence the tarsus of the pigeon is said to be scutellate in front ;
the back of the tarsus of the pigeon is reticulated.

no Practical Zoology.

6. Bend the leg up close to the body in the position it has when
the bird settles on its perch. What effect has this on the toes?
Note the position of the toes when the leg is straightened.

The Tail.

1. Count the quills of the tail; spread the tail to see their
mode of overlapping ; make a diagram to show their mode of
overlapping as seen from behind ; compare the middle and outer
tail feathers.

2. The feathers which lap over the base of the tail are the
upper and lower tail coverts.

3. Raise the upper tail coverts to find the conical tip of the
outlet of the oil gland ; press the oil gland to get a drop of oil.

4. In front of the lower tail coverts is the anus.

The Wings.

1. Feel of the wing to make out the division into arm, fore-
arm, and hand.

2. The foremost angle of the wing is called the bend of the wing.
To what part of your arm does this bend of the wing correspond ?
Just outside of the bend of the wing find the false wing, a cluster
of short quills, borne on the thumb.

3. The long quills borne on the hand are the primaries ; count
them. The quills on the forearm are the secondaries ; count them.
When quills are found on the arm, they are called tertiaries.

4. The shorter feathers which overlap these quills above and
below are the upper and lower wing coverts.

5. Extend the wing; compare its upper and lower surfaces;
observe the shape of the quills, and the way they overlap one
another ; put all these facts together and consider their effect in
the down stroke of the wing. What is the result of this arrange-
ment when the wing is moved quickly upward?

6. Extend the wing and hold it squarely in front of your face.
Send a quick puff of breath squarely against the under surface of

Aves. Ill

the wing. What effect does this have on the individual feathers
and the wing as a whole?

7. Repeat the experiment with the outer surface of the wing,
noting carefully how each separate feather is acted on, and what
is the effect on the wing itself. What is the effect of the wing on
the air current in each of these experiments?

The Feathers.

I. Pull out one of the. large wing quills and study its parts;
the central axis is the shaft ; the expanded part is the vane ; the
side branches of the shaft are the barbs, and the side branches
of the barbs are the barbules. Wiih a lens examine the upper and
lower surfaces of the vane ; then tear one of the barbs loose from
the barbs in front of and behind it, and study it carefully ; again
watch closely while tearing two barbs apart, to see how the barbules
are related to each other; now examine the vane of the same
quill at the very beginning of the vane, near the end that was
attached to the wing. What is the difference between the arrange-
ment of the barbs in these two places? Observe the hole in
the tip of the shaft ; run the point of a dissecting-needle along the
groove in the under surface of the shaft toward the base of the
shaft. This should lead the point of the needle into another
opening, communicating with the cavity of the shaft. Examine
this region with a lens, and determine that the two sides of the
vane meet at this point. Make drawings of a quill, as seen from
above and below, showing all these points.

With sharp scissors cut across the feather in the middle of the
vane. Look at the cut end ; observe that the vane is attached to
the upper edges of the shaft ; compare the place of attachment
of the vane to the shaft, with the place of attachment of the wing
to the body. Cut part of the wider side of the vane at right angles
to the barbs ; with a lens, or a low power of the microscope,
examine the edge of this cut. Make drawings showing these
arrangements of the parts of the quill. What are the advantages
of such arrangement?

112 Practical Zoology.

2. Take one of the body feathers, and compare it with the
quill. In what lies the chief difference?

3. Find a feather that is wholly composed of "down," if there
be such ; examine the " down " with a microscope.

4. Pick a small part of the breast, and study one of the fine,
hairlike pinfeathers. How does it differ from the feathers already
examined ?

5. Take a primary feather that is in good condition and set it
erect in the hole in the end of a trunk key. The hole should
be deep enough to hold most of the length of the free end of the
quill, but must not be so deep as to catch the vane and interfere
with the free rotation of the feather. Instead of a key you may
use a spool, piece of glass or metal tubing, or anything with a
smooth hole of suitable depth and width. Now hold the feather,
thus supported, vertically before your face and gently blow against
it. How does the feather turn? In what position does it remain?
Try this with the feather in different positions at the beginning of
the experiment. Compare the results of this experiment with the
observations made in blowing against the inside and outside of the
wing, and explain the advantages of the shape, structure, arrange-
ment, and mode of overlapping of the feathers. Try the breath
on the secondary feathers as above directed. If you were using
a quill for a pen, would it make any difference what kind of a
feather you took? Would it make any difference whether it came
from the right wing or the left wing?

6. Study the arrangement of the feathers ; do feathers grow on
all parts of the body ? A fledgeling shows this point well. Push
aside the feathers along the line of the ridge of the pigeon's
breastbone and examine the skin ; do feathers grow here ? Look
for other unfeathered areas. Note how the feathers overlap.

7. Pick the feathers from one side of the pigeon, just to the
middle Hne ; lay the bird on the feathered side, and make a draw-
ing, showing (i) the outline of the feathers, and (2) the outline
of the body within.

8. Pick off all the feathers of a pigeon or hen and weigh them

Aves. 113

What is their weight? What fraction is this of the weight of the
entire bird?

Use Jordan's Manual of the Vertebrates for finding the names
of our native birds.

HOW TO PREPARE A BIRD SKIN.

Materials Needed. — i. A freshly killed bird, in good condition.
2. Arsenic, or arsenic and powdered alum in equal parts. 3.
Cotton. 4. Several sheets of paper ; stiffer paper than newspaper
is preferred. 5. A plate. 6. Scissors. 7. Knife (scalpel, if pos-
sible). 8. Forceps. 9. String. 10. Corn meal, to sprinkle on
for absorbing blood or other liquid escaping.

Process. — First make a wad of cotton and with the forceps
push it into the throat. This is to keep moisture from escaping
and soiling the feathers. Do the same with the anal opening.
Break both wings as close to the body as possible. Now lay the
bird on its back, with the head toward your left. Part the feathers
along the breast and abdomen. Hold them apart with the thumb
and fingers of the left hand, while with the scalpel you cut through
the skin, beginning at the center of the breast and going straight
back to the anus. Here make a fork in the cut and go around the
anal opening. With forceps hold up the edge of the skin while
loosening it with the handle of the scalpel. Be careful during the
whole process to keep the feathers turned back so they will not be
soiled by coming in contact with moist tissues. Sprinkle with corn
meal to absorb moisture. Loosen the skin on one side down to
the thigh, and around the. knee. Then with the thumb and finger
take hold of the tarso-metatarsal joint (heel) and push the knee
out, at the same time pressing the skin back so as to expose the
knee. Run one blade of the scissors under the bend of the knee
and cut through the joint (cut close to the joint of the scissors to
avoid straining them ) . Cut through the remaining flesh, being care-
ful not to cut the skin. Take hold of the leg with thumb and fingers
of one hand, thus suspending the whole body. With the thumb
and fingers of the other hand carefully scrape the skin away from

fi4 Practical Zoology.

the flesh, using the thumb and finger nails. It will not do to pull
on the skin, as it is too tender. On reaching the heel remove all
the flesh, leaving the bone. Now pour about half a teacupful of
arsenic on a plate. Hold the everted leg over the plate and apply
arsenic thoroughly to the skin and the bone. Take hold of the toes
and pull the skin right side out again. Repeat this with the other
side. After loosening the skin well back on the sides, lift the bird,
rest the front end of the breast on the table, and turn the tail toward
the back. Cut through the bones supporting the tail close to the
bases of the tail feathers, but care must be taken not to loosen them.
Over the rump there is almost no flesh and the skin adheres to the
bone. Especial care must be taken here not to tear the skin.

Continue toward the head, turning the skin wrong side out.
From this point on, it is very convenient to have a suspended
hook by which to hang the bird so you can use both hands in
skinning. Otherwise hold the body just in front of the hips. If
pressure is applied to the abdomen its soft contents may be forced
out. When the shoulders are reached, skin as far as the elbow
and cut off the wings where the bones were broken. When the
head is reached great care must be exercised. Proceed slowly,
pressing the skin loose with the nails. At the ear, the thin sac,
lining the ear down to the drum, must be pulled out. In skinning
past the eyes be sure not to cut the eyelids. Continue to the base
of the bill. Sever the neck close to the skull, cut out the base of
the skull and remove the brain by scooping it out with the handle
of the scalpel. Remove the eyes, tongue, and all soft tissues on
the head. Now return to the wings and cut away all the muscle
from the humerus. It is not safe to try to skin beyond the elbow
because it would loosen the secondaries; but the fleshy inner sur-
face of the forearm may be uncovered, part of the muscle removed,
and arsenic pushed in to poison what remains. Remove any par-
ticles of muscle or fat still adhering to the skin. Now lay the skin,
still turned inside out, on the plate of arsenic. Roll it over and
over in the arsenic and thoroughly rub the preservative on every
part of the skin, skull, and other bones, especially at the wings, legs.

Aves. 115

and tail. Roll balls of cotton and place in the eye sockets. Now
proceed to turn the skin. Placing the thumbs at the base of the
skull, use as many fingers as can work in pulling (or rather roUing)
the skin back over the head, the thumbs meanwhile pushing. Care
and patience must be used here, otherwise a good skin may be
ruined. When the skin has been turned back over the head it is
easy to grasp the bill, and the entire skin is again outside out. It
will probably look rather dilapidated, but do not be discouraged.
Shake it, holding by the bill, to get rid of the loose powder and to
rearrange the feathers. With forceps or scalpel handle arrange the
leathers where needed. Lay the skin on its back. Make a slender
roll of cotton for a neck, and with the forceps insert it so it will
reach the base of the skull. Next make a body of cotton (you have
ihe model before you) . In inserting the body, see that the feathers
around the edge of the cut are not turned in. Draw together the
edges of the ventral cut ; it is not necessary to sew, but the feathers
should be made to overlap naturally. Cross the feet and tie them
together, thus crossed. Make a stiff paper cylinder, and tie or
pin it so it will not spread. Slip the skin in, head first of course,
taking care that the feathers overlap properly. Especial attention
needs to be paid to the region of the shoulders. Attach a label,
with the name of the bird, sex, date, locality, and your name. Lay
away in a safe, dry place for at least a week, before removing from
the cyhnder. Birds may be mounted on a board with wings spread.

DISSECTION OF THE PIGEON.

In dissecting the pigeon place it on a smooth board about twelve
inches wide and eighteen inches long. If a sheet of paper be
fastened to the board by thumb tacks, the board may be kept clean
for repeated use. In dissecting it is better to turn the board than
to turn the specimen on the board. The wings and legs or any
flaps of muscle may be stretched out and tacked down to suit
convenience at different stages of the work.

Pluck the pigeon before dissecting it ; dipping the Wrd in hot
water makes this easier.

ii6 Practical Zoology.

1. Insert a large tube into the mouth and inflate the crop, com-
pressing the neck to prevent the escape of the air. Note the
shape of the crop.

2. Beginning at the posterior end of tlie breastbone, cut through
the skin along the line of the ridge, or keel, of this bone, and
loosen the skin on each side, continuing forward over the crop,
being careful not to tear the crop ; again inflate the crop, and
examine it more fully. Observe the fine lines running crosswise
and lengthwise in the walls of the crop ; these are the muscle
fibers, transverse and longitudinal.

3. Loosen the crop from the front of the breast and from the
neck. Find the windpipe, or trachea, with its white rings of
cartilage.

4. On each side of the neck is the jugular vein. If it does
not show distinctly, let the bird's head and neck hang over the
edge of the table, and the vein will soon fill with blood.

5. Close to the jugular vein is a white cord, the vagus nerve.

6. Insert the tube into the glottis, and inflate ; observe the
swelling of the whole body, and the inflation of the thin-walled
air sacs in the hollow in front of the breastbone.

7. Break the bone of the upper arm, the humerus ; cut through
the skin and muscles, and push out through this opening the end
of the bone next to the body ; note that it is hollow ; slip one end
of a rubber tube over the end of the bone, and inflate ; what is
the result of this experiment? Keeping another tube connected
with the windpipe, determine whether air can be sent in through
the windpipe and out' of the humerus, and vice versa.

8. Slit the skin back over the abdomen to the anus, loosen
it well back on each side, and cut through the abdominal wall
just behind the breastbone ; inflate once more, and observe the
abdominal air sacs.

9. Cut down into the muscle of the breast, close alongside
the ridge (keel) of the breastbone, and around the outer border
of the breastbone ; thus loosen and raise a great flap of muscle,
the pectoralis major. Note the nerve and blood tubes entering

Aves. 117

its inner surface ; separate it from a smaller muscle lying
under it, which will be known by the glistening appearance
of the muscle sheath ; sever the attachment of the pectoralis
major to the breastbone, and all other organs except at the
extreme front end ; here the muscle narrows into a tough
white cord, or tendon ; trace this tendon to. its attachment to the
bone of the arm ; now lay the pigeon on its back in one hand,
and pull this muscle backward, noting the effect on the wing.
In like manner loosen all the posterior attachments of the sub-
clavian muscle which was covered by the pectoralis major,
lying in the angle between the keel of the breastbone and the
body of the breastbone ; prove its action, this time holding the
pigeon right side up. Compare these two muscles in size, and
in the amount of work they have to do. The hinder attachment
of each of these muscles is called its origin ; and the place of
attachment of the tendon to the wing bone is the insertion. Cut
through the body wall around the margin of the breastbone,
through the ribs, coracoid bones, and wishbone, and entirely
remove the breastbone.

10. Covering a considerable part of the abdominal organs is
the reddish brown liver.

11. Lift the liver and disclose, at the left of the body cavity,
a hard mass, the gizzard. Slit the abdominal wall in the middle
line back to the anus, push aside any fat that may cover the in-
ternal organs, and turn the gizzard to the left of the bird to find
where the intestine arises from it ; trace the intestine from the
gizzard backward.

12. The part of the intestine nearest to the gizzard is the
duodenum.

13. In a long loop formed by the duodenum is a pinkish
organ, the pancreas.

14. Trace the intestine, tearing away the fat and the thin
walls of the abdominal air sacs, observing that it is held in place
by a thin, transparent membrane, the mesentery.

15. The intestine has two short side branches, the oeca.

Ii8 Practical Zoology.

1 6. Just before the intestine ends, it widens, forming the
cloaca.

17. Turn the gizzard to the right of the bird; entering it
from the front, find a mottled, bulging tube, the glandular stom-
ach; pull the crop forward, to shew the connection between it
and the glandular -stomach. To the light of the glandular
stomach is the small, red spleen ; pull the gizzard backward, and
cut off the glandular stomach as far forward as possible ; remove
the gizzard and intestines. Note the relations of the tubes
which enter and leave the gizzard ; open the gizzard, observing
the thick outer muscular coat, from which the gizzard is some-
times called the muscular stomach. Note also its tough lining;
examine the contents of the gizzard ; why does the gizzard have
such a thick coat of muscle ? Do all birds have this kind of
gizzard ?

18. In front of the liver is the heart, in a thin sac, the pericar-
dium. Cut into its posterior wall, and turn the heart forward,
to see the dark vein, the postcaval vein, running to it from the
liver ; pull the heart backward, to see the whitish arteries running
forward from it. The main artery runs forward, and turns to
the right before going backward, while in man the corresponding
artery turns to the left. Prick a hole in one of the large veins
near the heart ; insert the point of a blowpipe, and inflate the
heart ; its red, conical part is composed of the ventricles ; the
dark base is made up of the two auricles. Tie a thread around
the veins at the anterior and posterior borders of the liver, and
cut this organ away.

19. On each side are the pink lungs. Pick away the thin
membranes bordering the outer hinder borders of the lungs ;
look for holes through which the lungs communicate with the ab-
dominal air sacs ; look for the trachea. Remove the lungs, not
failing to see how closely they are attached to the back, being
indented by the ribs.

20. In the hinder part of the body cavity are the dark-
colored, irregular kidneys. Tear them away, observing how

Aves. 119

they are composed of several lobes, which fit into the hollows
of the pelvis. After removing the kidneys, observe the white
nerves extending outward from the sides of the spinal column to
pass to the thighs.

21. In front of the kidneys are the two white oval spermaries,
in the male ; in the female, the ovary, often showing many eggs in
different stages of development. The kidneys and reproductive
organs send tubes to the cloaca ; the tube which conveys the eggs
from the ovary to the cloaca is the oviduct.

22> Remove the heart, cut off the auricles, and look down
into the ventricles ; cut across the middle of the ventricles, and
make a drawing of this cross section.

23. Observe the fold of skin extending across the angle be-
tween the arm and forearm ; dissect away the skin, and find a
membrane within the skin fold.

24. Observe the muscles connecting the hinder edge of the
breastbone and the pelvis (which were cut through in opening the
abdomen) ; these are the abdominal muscles. How does the bird
perform the act of breathing ? Compare the bird, snake, frog,
and man, in their modes of breathing.

25. Bend the leg up close to the body, to the position of
perching ; what effect does this bending of the leg have on the
toes? How does the bird stay securely on the perch when
asleep ? Dissect the leg to find the mechanism by which the
toes are clenched as the leg is bent.

26. Dissect out the tongue, and compare it with the tongue
of the snake.

27. Clean away as much as possible of the soft tissues, and
keep the skeleton for later study.

THE BRAIN OF THE PIGEON.

Cut away the top of the skull with a sharp knife, using great care
not to injure the soft brain, and make out the following parts : —

I. In front, the large cerebrum, consisting of two hemispheres,
which are separated by a deep groove.

lao Practical Zoology.

2. Behind the cerebrum is the undivided cerebellum.

3. Running backward from the under side of the cerebellum is
the spinal cord ; trace it back into the backbone. Make drawings
of the brain, as seen from above and as seen from the side.

THE SKELETON OF THE PIGEON.

Notice the lightness of the whole skeleton. What part of the
pigeon's weight is bone? Compare the eye cavity with that of
man. The lower jaw does not join the skull directly, as in
man, but is joined to an irregular bone, which, in turn, joins the
skull. This is the quadrate bone. The hole by which the spinal
cord leaves the brain cavity is the occipital foramen ; in front of
this foramen is a Httle, rounded projection, the occipital condyle.
Observe how this condyle fits into a cavity in the first vertebra of
the neck. Count the vertebrae of the neck, or cervical vertebrae.
Observe the consolidation of the vertebrae in the back ; note
the joint in each rib, and the arrangement for bracing the ribs
together. Press the breastbone alternately toward the back
and away from it, meanwhile watching the joints in the ribs.

The " wishbone " corresponds to the two " collar bones " of
man. Alongside the two branches of the wishbone are the cora-
coid bones ; what especial need of such bones in this place ? In
the wing find, in the arm, the humerus ; in the forearm, the ulna
and radius. The hand has only part of the fingers developed ; a
little bone, representing the thumb, is present (which bore the
feathers of the "false wing"). In the thigh is the femur; in the
leg is the tibia ; and alongside it, the small fibula. The bone
above the foot represents the consolidated bones of the human
ankle and foot as far as the toes. What evidence is there of such
consolidation ?

THE HEN'S EGG.

So place a hen's egg in a basin of water that it cannot roll,
mark the upper side plainly, and boil it hard ; keep track of the
side that was uppermost.

Aves. 121

1. Crack the shell, and pick it away; put a piece of it in
strong vinegar, or other acid. Of what is the shell made?

2. Note the thin membrane Hning the shell.

3. Does the egg completely fill the shell? Where is the air
space? Does the lining membrane, in this region, adhere to the
shell or to the " white " ? How can a fresh egg be distinguished,
without breaking? Does a fresh egg, in water, lie in the same
position as when on a table ? What is the use of this air space ?

4. How is the yolk situated in the white? How in reference
to the position during boiling? Compare a number of eggs, to
see if there is any regularity about this.

5. Note the round spot on the yolk, where it comes nearest
to the surface. This is the germ spot, in which the chick begins
to form.

6. With a sharp knife, split the egg lengthwise. Is the white
alike throughout? Is the yolk alike throughout? Has the yolk
a coat? Cut and tear these parts to make out their structure, if
they have any definite structure.

7. Boil an egg hard, as before ; mark a line lengthwise around
the egg, passing through the point that was uppermost while boil-
ing ; carefully break away the shell on one side, and with a clean
cut remove this half of the white and yolk ; place the other half
in the position it had while cooking; make a drawing of this
section, using different colors to show the shell, shell membrane,
air space, white, yolk, germ spot, etc.

8. Prop an egg on end, and boil in this position. Is the yolk in
a different position in consequence? The white of the egg has
interlacing fibers and partitions which keep the mass together;
the white cannot be mixed with water till these membranes are
cut or broken ; hence an egg, to be eaten raw, should be whipped
to break these membranes. The white is not a part of the true
egg. In dissecting a bird, the eggs, of various sizes, according to
their stages of development, may be found in the ovary. At this
time the egg consists of the yolk, with a thin coat ; the white is
deposited around this later, during its descent through the oviduct ;

Ill Practical Zoology.

the shell is last formed, and is absent in the case of most animals.
In the development of birds all their nourishment, before hatching,
must be stored in the egg ; hence its large size.

9. Set a hen on a dozen eggs ; mark the date ; open and
examine an egg each day ; if the egg was fertilized, the cells
of the germ spot multiply by division, and soon take definite
arrangement ; at the end of twenty-four hours the backbone is
outlined ; during the second day the brain begins to develop, and
the heart appears ; on the fourth day the legs and wings make
their appearance as flattened buds ; during the first few days it is
hard to say whether the embryo was that of a bird, a reptile, or a
mammal ; after this, the characters peculiar to birds become evi-
dent, the feathers begin to develop, and, later, the particular kind
of bird may be recognized.

Egg-laying animals are called oviparous. If the young develop
within the body of the parent, receiving nourishment from the
blood of the parent, the animal is said to be viviparous ; ''or,
the young may complete its development while the egg remains
in the interior of the body of the parent, but quite free and un-
connected with it, as in those vertebrates which are termed ovo-
viviparous."

The study of development is called embryology.

Topics for Reports. — Ostrich Farming. Origin of our Domestic
Fowls. Origin of the Domestic Pigeon. Varieties of Pigeons.
Game Birds. The Guinea Fowl. The Turkey. Hawking. Carrion-
eating Birds. Birds whose Plumage is used for Ornament. Birds
and Millinery. Laws for Bird Protection. History of the English
Sparrow. The " American " Eagle. The Fishhawk. The Whip-
poor-will. Introduction of New Game Birds. The Road Runner.
The Mocking Bird. The Water Ouzel. Hawks and Owls.

Read A?nerican Natural History, Hornaday.

CHAPTER XII
MAMMALIA.
THE RABBIT.
Field Study.

1. Learn where to look for rabbits at different seasons.
Keep in mind that they are timid creatures and seek sheher, and
that they prefer to be near a good supply of food.

2. In what kind of places are rabbits usually found in warm
weather ? Look in tufts of grass along hedges and fence cor-
ners. Do rabbits seek more sheltered places in winter ? Is
this on account of cold ? Or for concealment ? The smoothed
and sometimes slightly hollowed place in which a rabbit squats is
called its " form." Is this form equally exposed on all sides ?
Can it enter and leave in any direction ? Has the direction in
which it is headed any relation to the wind ? In what position
does it rest ? Are the ears erect or laid back while it sits in its
form ? Does a rabbit leave its form in the daytime, if undis-
turbed ? Does it sleep during the day ? Are the eyes open or
shut while it sits in its form in daytime? As you quietly ap-
proach the rabbit squatting in its form, does it seem aware of
your presence ? Does it ever turn the head to see you ? Does
it need to turn the head to see you ? Can a squatting rabbit see
an object in any direction without turning its head ? Stand
near a rabbit in its form and watch its eye. Does it wink?
How much of the time is a rabbit in its form ? How much of
the time out of it ? Find a rabbit in your neighborhood and
frequently visit it to become as well acquainted with it as possi-
ble. On moonlight nights visit a form that you have lately

123

124 Practical Zoology.

found occupied. Is " Brer Rabbit " at home ? Are rabbits
sociable? Do they associate with each other more at one
season than at another ? Do they seem to have any special
means of communicating with each other ? Do they ever give
signals of danger? Does one ever call another to share
food that it has found ? Do they ever aid each other in any
danger or injury ? Has the rabbit a voice ? If so, on what
occasions is it used ? How do rabbits protect themselves from
cold ? How does the squatting position economize heat ? Do
rabbits ever stretch out and lie at full length ? Or are they al-
ways bunched up when resting ? In what situations do you find
rabbits in warm weather? In very cold weather? In dry
weather ? After heavy rains ? Do rabbits ever burrow ? Do they
hide in holes ? What are the effects of substituting barbed wire
fences for rail fences and hedges ? What is the effect of grubbing
out bushes in clearing land for cultivation ? How does the cul-
tivation of farm and garden crops affect rabbits ? Is the num-
ber of rabbits ordinarily increased or diminished in " settled "
districts ?

3. Study carefully the rabbit's modes of locomotion, the slow
hopping as well as the running. Study the tracks and be sure
you can tell by which foot each track is made, and how the legs
are moved. Can you tell by the tracks whether or not the rabbit
was frightened ? How far can a rabbit jump ? Are the front
and hind tracks farther apart when running than when hopping ?
Can a rabbit run i?r without stopping? Follow a frightened
rabbit ; does it run far in a straight line ? Can you stop a run-
ning rabbit by whistling ? Do rabbits ever zigzag when running
away ? If so, why ? Are rabbits long-winded ? Compare a
rabbit and a greyhound in this respect. What reasons for the
difference? Can a rabbit swim? Does it often take to
water ?

4. What evidences do you find in fields and among bushes as
to the rabbit's food ? When does it eat ? Does it need much
or little food ? Does it usually go far from its form for food ?

Mammalia. 125

Does the kind of food vary much with the season ? Does it
need to make much effort to get its food ? Do rabbits drink
water ? Look along creeks and around springs for evidences of
their visits. Is it clear that they come to such places to drink ?
Does the amount of water in their food make any difference in
the amount of water that they take as such ? Do they need the
same amount of water at different seasons ? What reasons for
these differences ? Do they ever suffer for water in severe win-
ter weather, when streams are frozen over ?

5. What harm is done by rabbits? Do they do any good?
What means are employed to keep them from doing damage ?
What means to kill them off ?

6. What are the enemies of rabbits ? In what different
ways do they avoid or escape enemies ? Is there any advantage
in having the exposed part of the tail so white and conspicuous :
What kind of shelter does a rabbit seem to prefer when pursued
by dogs ? Do rabbits ever " double " on their tracks ? Or re-
sort to other tricks to escape pursuit? What is meant by
" circling " ?

7. In spring and early summer look for the nests containing
young rabbits. They are not conspicuous, being pocketlike
depressions lined with fur, and narrowed at the opening,
which is at the level of the surface. If a nest is found, watch
it closely day and night. If you have a dog, be careful not to
allow him to accompany you, for even if he does not disturb the
nest while with you, he may return and kill the young. Does
the mother stay with the young ? If not, does she remain near ?
When and how often does she visit the young, and how long
does she stay with them ? Do rabbits have more than one
litter in a year ? How many in a litter ? Is their natural rate
of increase slow or rapid as compared with most mammals ?
Are the young of the same color as the adults ? Are there any
peculiar markings ? How long does it take a young rabbit tc
reach full size ? Are young rabbits as speedy or as cunning in
escaping enemies as the old ones ?

126 Practical Zoology.

HOME STUDY OF RABBITS.

1. For this study use a wild rabbit caged, a tame rabbit, or a
Belgian hare. Study many of the points to which attention has
been called in the suggestions for the study of wild rabbits in
their homes, such as the modes of hopping, jumping, running,
modes of moving the feet, the tracks, etc. Study also the vari-
ous attitudes of rest and motion, of timidity, of effort at con-
cealment, of hunger, the use of the ears and eyes. Do they give
any signals when alarmed ? Do tame rabbits recognize dogs as
enemies ? After an alarm do rabbits soon become quiet, or
does fright have a more lasting effect ? Has a rabbit any means
of defense against enemies ? Are the claws ever used when it is
attacked by a dog ? Or when it is seized by a man, as when
pulled out of a brush heap or a hole ? Do rabbits ever fight
each other ?

2. Find what food the rabbits prefer. Does a rabbit eat
much, relatively ? Does it eat rapidly or slowly } Watch the
process of eating. How do the jaws move ? What is the use
of the "harelip"? If possible, in this connection, get a well-
cleaned rabbit's skull, and study the teeth and the hinge by
which the jaw joins the skull. Why is there a vacant space
between the gnawing teeth and the grinding teeth ? How are the
front teeth kept sharp ? How do the ridges run on the grinding
surfaces of the back teeth ? Why is this so ?

3. Is a rabbit's eye large or small, in proportion to its size?
Is. its sense of sight keen ? Test this in various ways. What is
the shape of the pupil of the eye ? Is it relatively large or
small ? Does it vary with the amount of light ? Do you ever
see color in the pupil ? If so, in what situations ? Is the iris
of the same color in all rabbits ? Compare wild and tame rab-
bits in this respect. Test a rabbit's sense of hearing. Is the fact
that a wild rabbit often sits motionless in its form, sometimes
till actually kicked out, any proof that it did not hear or see the
hunter ? What is it probably thinking in such a situation ?

Mammalia. 127

Test the sense of smell in rabbits. Does it use this sense in
judging food ? Has it a keen sense of taste ? Try to test the
sense of taste without also bringing into use the sense of smell.
Test the sense of touch. What is the use of the " whiskers " ?
Do you think a rabbit possesses any sense that you do not have,
or lacks any that you have ?

4. Are rabbits cleanly in their habits ? Do they wash their
paws and faces as do cats ? Do rabbits shed hair ? Do they
change their color during the year ? Do rabbits have parasites ?
If so, what kinds ? Do they do anything to get rid of them ?
Can you do anything for such troubles ? Are rabbits espe-
cially subject to any diseases ? If so, what are they, and what
can you do to prevent disease, or to cure it if it has become
established ?

EXTERNAL FEATURES OF THE RABBIT.

1. Note the shape and proportions of the body. The ante
rior part of the body, distinguished by the ribs, is the chest, or
thorax; the soft-walled, posterior part is the abdomen. Note
the relative size of the fore and hind limbs. Are the soles of
the feet bare or hairy? How many toes has each foot? Are
there claws ? Are they weak or strong ? How do they differ
from those of a cat ? In the hind limb how much belongs to
the foot ?

2 . How many kinds of hair do you find on a rabbit ? The
short hairs, making the most of the coat, are the fur. How do
the hairs of the fur differ from the other hairs ? Press hair and
fur aside till you can see the skin ; is the color the same in the
deeper parts as near the outside? Pull out hairs of different
sorts ; has an individual hair the same color from end to end ?
Are the different hairs of the same thickness and strength ? Are
they all rooted to the same depth in the skin ? Are the hairs
glossy or dull-surfaced ? Do they seem oily ? Do they become
wet easily ? Compare them with the hairs of a mink or muskrat
in these respects. Examine different hairs under a micioscope

126 Practical Zoology.

HOME STUDY OF RABBITS.

1. For this study use a wild rabbit caged, a tame rabbit, or a
Belgian hare. Study many of the points to which attention has
been called in the suggestions for the study of wild rabbits in
their homes, such as the modes of hopping, jumping, running,
modes of moving the feet, the tracks, etc. Study also the vari-
ous attitudes of rest and motion, of timidity, of effort at con-
cealment, of hunger, the use of the ears and eyes. Do they give
any signals when alarmed ? Do tame rabbits recognize dogs as
enemies ? After an alarm do rabbits soon become quiet, or
does fright have a more lasting effect ? Has a rabbit any means
of defense against enemies ? Are the claws ever used when it is
attacked by a dog ? Or when it is seized by a man, as when
pulled out of a brush heap or a hole ? Do rabbits ever fight
each other ?

2. Find what food the rabbits prefer. Does a rabbit eat
much, relatively ? Does it eat rapidly or slowly ? Watch the
process of eating. How do the jaws move ? What is the use
of the " harelip " ? If possible, in this connection, get a well-
cleaned rabbit's skull, and study the teeth and the hinge by
which the jaw joins the skull. Why is there a vacant space
between the gnawing teeth and the grinding teeth ? How are the
front teeth kept sharp ? How do the ridges run on the grinding
surfaces of the back teeth ? Why is this so ?

3. Is a rabbit's eye large or small, in proportion to its size?
Is its sense of sight keen ? Test this in various ways. What is
the shape of the pupil of the eye ? Is it relatively large or
small ? Does it vary with the amount of light ? Do you ever
see color in the pupil ? If so, in what situations ? Is the iris
of the same color in all rabbits ? Compare wild and tame rab-
bits in this respect. Test a rabbit's sense of hearing. Is the fact
that a wild rabbit often sits motionless in its form, sometimes
till actually kicked out, any proof that it did not hear or see the
hunter ? What is it probably thinking in such a situation ?

Mammalia. !27

Test the sense of smell in rabbits. Does it use this sense in
judging food ? Has it a keen sense of taste ? Try to test the
sense of taste without also bringing into use the sense of smell.
Test the sense of touch. What is the use of the " whiskers " ?
Do you think a rabbit possesses any sense that you do not have,
or lacks any that you have ?

4. Are rabbits cleanly in their habits ? Do they wash their
paws and faces as do cats ? Do rabbits shed hair ? Do they
change their color during the year ? Do rabbits have parasites ?
If so, what kinds ? Do they do anything to get rid of them ?
Can you do anything for such troubles ? Are rabbits espe-
cially subject to any diseases ? If so, what are they, and what
can you do to prevent disease, or to cure it if it has become
established ?

EXTERNAL FEATURES OF THE RABBIT.

1. Note the shape and proportions of the body. The ante
rior part of the body, distinguished by the ribs, is the chest, or
thorax; the soft-walled, posterior part is the abdomen. Note
the relative size of the fore and hind limbs. Are the soles of
the feet bare or hairy ? How many toes has each foot ? Are
there claws ? Are they weak or strong ? How do they differ
from those of a cat ? In the hind limb how much belongs to
the foot ?

2 . How many kinds of hair do you find on a rabbit ? The
short hairs, making the most of the coat, are the fur. How do
the hairs of the fur differ from the other hairs ? Press hair and
fur aside till you can see the skin ; is the color the same in the
deeper parts as near the outside ? Pull out hairs of different
sorts ; has an individual hair the same color from end to end ?
Are the different hairs of the same thickness and strength ? Are
they all rooted to the same depth in the skin ? Are the hairs
glossy or dull-surfaced ? Do they seem oily ? Do they become
wet easily ? Compare them with the hairs of a mink or muskrat
in these respects. Examine different hairs under a micioscope

128 Practical Zoology.

What are the qualities that make some kinds of hair or fur pref-
erable to others for making furs, felts, and fabrics ? What are
some of the chief articles made of fur after it is separated from
the skin ?

3. Examine the eyes and eyelids. Can you find a third eye-
lid? Is it useful?

4. Examine the mouth. What is the use of the " hare-lip " ?
What is the shape of the nostrils ? Look closely at the inside
of the cheek. How many front teeth are there and how are
they arranged ? Are they alike in size and color ? Have any of
them any peculiar markings ? Examine the tongue and palate.

5. Examine the ears. Hold one of them up toward a good
light.

6. Examine the tail. What is its usual position ? Can you
make it stay in any other position ? Is its color uniform ? Of
what use is it ?

Use Jordan's Manual of the Vertebrates in finding the names
of all the mammals met with in your neighborhood.

DISSECTION OF THE RABBIT.

The rabbit should be dissected on a board eighteen inches
long by twelve inches wide. This should be covered with
heavy manilla or straw paper, fastened down by tacks. The
specimen should be a freshly killed, uninjured one, those ob-
tained from the markets being usually so mutilated as to be
unfit for this work.

I. Lay the rabbit on its back, stretch out the front and hind
limbs and tack firmly through the feet. Slit the skin in the
middle line from the base of the neck to the pelvis and strip it
well back along the sides. Compare the walls of the thorax
and abdomen. With forceps pinch up a fold of the wall of the
abdomen, and with scissors cut through the wall in the middle line.
In all this work be careful that the lower point of the scissors
does not injure anything within. • Cut forward in the middle line
to the breastbone.

Mammalia. 129

When the chest is first opened, look in to see the position of
the heart. The attachment along the inside of the breastbone
must be cut close to the bone.

When the breastbone is reached, let the cut fork to each side
along the line where the bony part of the ribs ends and the
cartilaginous part begins. At the anterior end cut across the
breastbone and entirely remove it. Extend the slit in the ab-
dominal wall to the pelvis. Make slits outward in the middle
of each side of the abdominal wall ; turn the flaps outward, pin-
ning them down if necessary. There are now disclosed the two
parts of the body cavity, the chest cavity, or thoracic cavity,
containing the heart and lungs, and the abdominal cavity, con-
taining the digestive organs. Between these two cavities, and
the sole partition separating them, is the thin muscular dia-
phragm. Examine the diaphragm from the anterior side. Can
you see that its central part is thin and nearly transparent?
This is the tendinous part of the diaphragm. Note the shape
of the diaphragm as seen from the front. Gently press the liver
backward to see the posterior surface of tte diaphragm. Take
hold of the diaphragm with thumb and finger on its opposite
surfaces to learn its thinness, its smoothness and flexibility. Is
the diaphragm flat or arched ? How is it arched ?

The Organs of the Abdominal Cavity.

1 . Observe that the ventral wall of the abdomen is composed
of muscle. Its smooth lining is the peritoneum. Feel of it.

2. Study the abdominal organs in their natural position.
Filling most of the space of the abdominal cavity is the coiled
intestine ; next to the diaphragm is the dark-colored liver ; back
of the liver, and partly covered by it, is the stomach ; and in
the posterior part of the abdomen is the bladder.

3. Pull the intestine backward, and make out the shape, size,
position, and color of the stomach. Observe how the liver and
stomach fit together ; push the liver forward, and turn the
stomach back to find z white tube entering its anterior surface ;

ijo Practical Zoology.

this is the gullet, or esophagus. Just back of the stomach Is a
small, red body, the spleen.

4. Find now the connection between the stomach and mtes-
tine. Make a drawing of the stomach, showing its sha^e and
the connections with the gullet and intestine.

5. Trace the intestine ; that part which forms a long loop
near the stomach is the duodenum. Within this loop is an
irregular, fatty-looking mass, the pancreas. Find the pancreatic
duct entering the intestine. This is more easily found in the
dog.

6. Observe that the intestine is held by a thin membrane in
which are branching blood tubes ; this is the mesentery ; find
its supporting attachment. In tracing its course drag the in-
testine out of the abdominal cavity, but do not tear the mesen-
tery.

7. The large, greenish side branch of the intestine is the
cecum. All the intestine from the stomach to the entrance of
the cecum is the small intestine; that part of the intestine
posterior to the entrance of the cecum is the large intestine.

8. In handling the liver remember that it is very delicate and
easily torn, also that it contains much blood, and if torn is
likely to bleed enough to interfere with the dissection. Do not
touch the liver with any sharp instrument ; even the finger nails
may tear it unless one is careful. Pull back the liver to see
how snugly it fits against the diaphragm. Are the two attached
to each other ? Note the divisions, or lobes, of the liver. Tip
the liver up and forward to see the stomach, and how the organs
fit each other. On the posterior surface of the liver find the
dark bile sac. If its duct to the intestine is not readily seen,
press on the sac and some of the bile may be forced along the
tube, thus showing its course. Later snip a small hole in
the bile duct, insert a bristle tipped with sealing wax, and find
where the duct enters the intestine.

9. Tie the gullet in two places half an inch apart and cut
through between them. Do the same with the hinder part of the

Mammalia. 131

large intestine, the rectum, and sever it. Remove the stomach
and intestines, carefully cutting the mesentery along its whole
attachfnent to the intestine, and uncoil the latter. How many
times is the length of the body, including the head, contained
in the length of the intestine ? Compare the lengths of the small
intestine, cecum, and large intestine. Cut out about an inch of
the small intestine in the middle of its course, slit it open length-
wise, wash it thoroughly, and examine, under water, its inner surface
with a lens, to see the threadlike projections, or villi. In the
same way examine a piece of the large intestine. These points
may be made out in the intestine of a dog, or from specimens of
the calf's intestine obtained from the butcher. Tie the postcaval
vein just in front of the diaphragm and just back of the liver ;
cut away and remove the liver.

10. Observe the two bean-shaped kidneys attached to the
dorsal wall of the abdomen. They are covered by a thin layer
of membrane, the peritoneum, which lines the whole of the
abdominal cavity, and turns downward to form the mesentery,
which, like a sling, holds the intestine in place ; the mesentery
also covers, and almost completely surrounds, the stomach as
well as the liver. An artery, a branch of the aorta, extends into
each kidney, and from each kidney there runs a vein to join the
large postcaval vein. There is also a tube, the ureter, from
each kidney, running back to the urinary bladder.

The Heart and Lungs in Natural Position.

I. It should be noted that the heart and lungs collapse when
the chest is opened, and that they do not now show their natural
size. Slit the skin along the middle of the throat and find the
windpipe. Cut a slit in it lengthwise. Insert a tube, connected
by rubber tubing with a pair of bellows ; or inflate by the breath.
The lungs may be swelled to their natural size, filling the chest.
This will also show the natural relations of the heart and lungs.
Note how the lungs nearly surround the heart. Compare the

132 Practical Zoology.

color of the lungs when inflated with the color when collapsed.
Notice the subdivisions, or lobes, of the lungs.

2. In another rabbit, later, open the abdominal cavity ^^ithout
injuring the thorax. Pull back the liver, and the pink lungs
will show through the thin central part of the diaphragm. Keeping
the eye fixed on the lung, prick a hole through the diaphragm
near one side, and note the collapse of the lung. Is the lung of
the other side affected by this operation ? Open the chest and
note the thin partition separating the two sides of the chest.
This partition, the mediastinum, is a double membrane, and the
heart lies between its two layers. The following study of the
heart and lungs may be made with the heart and lungs of
the rabbit ; but if the same organs of a pig, sheep, or calf can be
obtained, it will be better to use them on account of their
greater size.

Topics for Reports. — The Fur-bearing Animals, such as the
Beaver, Otter, Sable, Mink, Muskrat, etc., with Accounts of their
Homes, Habits, and the Modes of trapping them. The Hudson
Bay Company. The Native Ruminants of North America, such
as the Musk Ox, Caribou, Moose, Elk, Deer, Sheep, Goats, and
Antelope. The Kinds of Bears native to North America. The
Mountain Lion. The Coyote. The Timber Wolf. The Wild
Cats. Prairie Dogs. The Weasel. The Badger. Jack Rab-
bits. Porcupines. The Buffalo.

Read American Natural History ^ Hornaday.

CHAPTER XIII.

MAMMALIA {Continued).

DISSECTION OF THE HEART AND LUNGS.

The heart and lungs of a sheep, pig, or calf are better to
study on account of their greater size.

1. Hold up the mass by the windpipe, with the heart away
from you. The end now uppermost is the anterior end, that
below is the posterior end ; the lung to your right is the right
lung, the one to your left is the left lung ; the surface nearest
you is the dorsal surface, and that opposite is the ventral surface.

2. Observe the windpipe, or trachea, with the stiff rings of
gristle, or cartilage. The thick part of the anterior end is the
larynx.

3. Running along the dorsal surface of the windpipe is a soft
red tube, the gullet or esophagus. At about the middle of the
windpipe separate the gullet and windpipe for three or four
inches. Note that next to the gullet the windpipe is soft and
yielding, where the gaps of the C-shaped cartilages are filled
with muscular and elastic tissue. Make a slit two inches long
in this soft membrane.

4. Inflate the lungs as follows : Take a wooden faucet, slip
the small end of the faucet into the slit just made in the wind-
pipe, and hold or tie firmly, but do not cut off either gullet
or windpipe. Inflate through the spout, then shut ofT the air ; if
the lungs have not been punctured they should now remain
distended. In holding up the lungs, take hold of the windpipe
above where the faucet enters, and hold in such a way as to pull
the windpipe up and at the same time press the faucet down.
If this is done, it will not be necessary to tie the faucet in. Note

133

134 Practical Zoology.

{a) the conical shape of the whole ; compare this with the chest
cavity, as shown in a skeleton ; (b) how the lungs nearly sur-
round the heart ; {c) the concave posterior surface of the lungs
where they fitted the convex anterior surface of the diaphragm ;
{d) the groove between the dorsal surfaces of the lungs in which
the spinal column fitted ; {e) the smooth, undivided dorsal
surface of the lungs, and their division ventrally into lobes ;
(/) the relative lengths of the dorsal and ventral surfaces of
the lungs. The anterior end of the lung is the apex ; the
posterior end is the base. Open the valve of the faucet.
What makes the air go out? Again inflate. Does it require
effort to do so ? Why ? Cut off the end of one lobe and again
inflate. Does the air escape ? Throw a piece of lung on water.
Pinch a piece of lung, holding it near the ear. The smooth,
moist, glistening membrane covering the lung is the pleura.
. 5. Observe a large whitish or yellowish tube running in the
groove between the dorsal surfaces of the two lungs. It is
usually covered with fat. It may have been cut off short, so that
its open end is easily seen near the windpipe. This is the main
artery, the aorta. Take hold of its free end and separate it
from its attachment to the other tissues, cutting close to it with
the scissors, so far as where it arches over the root of the left
lung. Now turn the free end forward.

6. Find where the gullet is cut off posteriorly ; slit it open for
an inch or two, and note its whitish lining, the mucous coat.
The thick red coat is the muscular coat ; it has an inner layer of
circularly arranged muscular fibers and an outer longitudinal
layer. Beginning posteriorly, separate the gullet from the wind-
pipe, cut off the windpipe about the middle, and entirely remove
the gullet and larynx.

7. Examine the windpipe ; insert a finger, and stretch it ; note
its C-shaped cartilages. Its lining is a mucous membrane.

8. Lay the heart and lungs on their ventral surface, with the
posterior end near you. Using the handle of the scalpel as a
chisel, clear away any tissue covering the windpipe, and trace it

Mammalia,

135

to the lungs ; its branches are the bronchi. How many bronchi
are there ? Here are often found small, oval, brownish masses,
the lymphatic glands, embedded in connective tissues. Scrape
these loose with the scalpel handle.

9. Lay the lungs on their dorsal surface, with the anterior
ends toward you. Note how easily the heart may be moved
about in its case, the pericardium. Slit the pericardium along its
ventral side, and note the smoothness of its lining and of the
surface of the heart. Observe the pericardial fluid.

10. Carefully compare the right and left sides of the heart.
Running obliquely across the surface of the heart is a groove
in which are blood tubes, often covered with fat. The part at
the right of the groove is the right ventricle ; at the left is the
left ventricle.

11. At the base (anterior end) of the heart on each side are
the right and left auricles.

12. Tip up and toward you the apex of the heart. Compare
its width and thickness ; compare the ventral and dorsal surfaces
as to length, convexity, etc. Press the two ventricles, and com-
pare them in firmness.

13. Turn the heart to the left, and examine the right auricle ;
find a large, flabby, red tube entering its anterior surface, the
precaval vein. Prick a small hole in it, and insert the blowpipe ;
hold firmly around the opening and inflate. This shows the
outline of the right auricle. Meanwhile, watch closely the dorsal
part of the auricle ; the postcaval vein should now be discovered
entering the auricle from the posterior region. Look for it out-
side, and on the dorsal side of the pericardium, where it runs
anteriorly from the diaphragm.

14. Turn the heart to the right, and observe a large, light-
colored tube arising from the base of the right ventricle be-
tween the two auricles ; this is the pulmonary artery. Again
turn the heart to the left, and raise the right auricle ; find the
aorta arising from the center of the base of the heart. Care-
fully separate the aorta from the pulmonary artery, and trace

138 Practical Zoology.

experiment. Hold the heart in the left hand, with the ventral
surface in the palm, and the tips of the fingers against the
right ventricle. Hold the heart under a faucet, or pour from a
pitcher, and let the water run first gently, then strongly, through
the right auricle into the right ventricle. Watch the tricuspid
valves as they float up and separate the auricle from the ven-
tricle. Empty the heart and fill it again, and as soon as the
valves rise, press with the fingers on the outside of the ventricle.
What effect has this pressure ? Let the nozzle of the faucet
project down between the valves, and again turn on the water.
Where does the water escape ?

4. Empty the heart and examine the valves. They will be
found lying close against the walls of the ventricle. Note the
white tendinous cords attached to the valves.

5. Push the finger past these valves to the very bottom of
the ventricle ; from the outside cut through the wall of the ventri-
cle at this point, and cautiously cut upward in both directions
along the border of the ventricle. Raise the outer wall of the
ventricle, and study the valves more thoroughly ; with the scalpel
handle raise them from the walls of the ventricle. How many
flaps are there ? How are they arranged ? The conical eleva-
tions of the muscle to which the tendinous cords are attached
are the papillary muscles. How are the valves held in place ?
How are they acted on, and how do they act ?

6. Find the connection between the right ventricle and the
pulmonary artery ; pass a probe up into the pulmonary artery.
Cut away enough of the wall ' of the ventricle to show the
beginning of the artery. Cut off the pulmonary artery just
before it forks to the two lungs ; slip over the faucet the end of
the artery connected with the heart, and turn on a little water.
Watch closely the base of the artery ; turn on more water, and
look from below at the base of the artery, to see the filling of
the pocketlike semilunar valves. Note their number, shape,
and arrangement. What is the effect of the stream of water
upon them, and what is their effect upon the stream of water ?

Mammalia. 139

7. Examine the left auricle, and find where the pulmonary
veins enter it. Cut away the lobe of the left auricle ; examine
its inner surface, and find the openings of the pulmonary veins.
Hold under a faucet, and prove the action of the mitral valve,
between the left auricle and the left ventricle. Insert the nozzle
of the faucet between the valves, and again turn on the water.
Where does it escape ? Cut off the aorta half an inch from its
base, and repeat the last experiment with the water, meanwhile
closely watching the semilunar valves of the aorta.

8. Above the pockets of the semilunar valves look for the
openings of the cardiac (coronary) arteries, which supply the
walls of the heart. Probe them. How many are there ?

9. Pass the handle of the scalpel between the semilunar
valves of the aorta into the left ventricle ; it passes back of one
flap of the mitral valve.

10. Cut open the left ventricle. Note the strong muscular
columns, the strong papillary muscles ; the mitral valve, though
ending in two main flaps below, is continuous at the top. The
valves between the auricles and ventricles are sometimes called
the auriculo-ventricular valves. This may be shortened to " aur-
vent " valves, and will be easily remembered, as the parts of the
word indicate the two cavities between which the valves lie.
Compare the walls of the right with those of the left ventricle.
Why this difference ? Note the partition between the ventricles.
Is there any direct communication between the right and left
halves of the heart ?

11. SUt open the aorta between two of the semilunar valves,
and study the valves more closely. In the middle of the free
border of each valve note the little thickened point, the corpus
arantii. When the valves close, these three little points fill up
a small, three-cornered opening that would otherwise be left
between the valves. These valves are sometimes called the
ventriculo-arterial, or, for short, the " vent-art " valves, as they
lie between the ventricles and the arteries. Again examine
the cardiac arteries.

140 Practical Zoology.

12. In another heart, carefully cut around the base of the
pulmonary artery, tie its outer end tightly over the end of a
glass tube or spool, and show the action of the semilunar valves,
by blowing suddenly and forcibly into the tube. To keep the
glass tube from slipping out, slip an inch of thick rubber tubing
on the end of the glass tube, so that the rubber tube is even with
the end of the glass tube. The valves work better when moist
and flexible ; therefore keep the preparation standing in a jar of
water until it is to be used. Slit open the artery, and study the
valves.

13. Longitudinal and cross sections of a frozen heart are
instructive.

The Distribution of the Arteries and Veins in the Cat or Rabbit
(injected). — Directions for injecting are given in suggestions
*'To the Teacher." i. The main artery, the aorta, is a thick-
walled tube, springing forward from the center of the base of
the heart. It soon arches over to the left, and runs along the
middle of the dorsal wall of the chest cavity.

2. At the bend, or arch, the aorta gives off two branches
(three in man). The first of these soon subdivides, giving off
a branch to the right fore limb, the right subclavian artery ; two
branches running along the side of the windpipe are the right
and left carotid arteries. The second branch of the aorta runs
to the left fore limb, and is the left subclavian artery.

3. During its course through the thorax the aorta is called
the thoracic aorta. Trace it to the point where it runs through
the diaphragm. It then becomes the abdominal aorta. Turn the
stomach and intestine over to the right, and observe the ab-
dominal aorta running along the dorsal wall of the abdomen.
Just posterior to the diaphragm, a branch is given off which
subdivides, and gives branches to the stomach, liver, and spleen.
Farther back a large branch is given off to the small intes-
tine. Follow it as it branches into the mesentery. This is the
anterior mesenteric artery. Find the branches of the aorta that
lead to the kidneys, the renal arteries. Some other branches may

Mammalia. 141

be seen, and finally the aorta divides into two large branches,
the common iliacs, supplying the two hind limbs.

4. Turn the stomach and intestines to the left, and observe
the two veins running forward from the two hind limbs. These
are the two external iliac veins. By their union they form the
postcaval vein.

5. Observe the veins from the kidneys, the renal veins.

6. Trace the postcaval Vein to the liver. Observe the vein
that gathers the blood from the intestine, the mesenteric vein.
This vein is joined by a vein from the stomach, the gastric
vein, one from the spleen, the splenic, and one from the pan-
creas, the pancreatic; together these form the portal vein,
which empties into the liver. Unlike other veins, the portal
vein subdivides, distributing the blood into the liver. The blood
thus distributed through the liver is re-collected, and by the
hepatic veins joins the postcaval vein, close to the diaphragm,
and almost wholly concealed by the liver.

7. The postcaval vein passes by the liver, through the dia-
phragm, and on to the right auricle.

8. On removing the skin of the neck, there should be found
on each side the large jugular vein. Each of these is formed
by the union of the internal and external jugular veins.

9. Just before each jugular vein enters the chest cavity it
is joined by a vein coming from the corresponding fore limb,
the right and left subclavian veins. The union on each side
forms the innominate vein. The two innominate veins, uniting,
make the precaval vein, which enters the right auricle. In the
rabbit there are two precaval veins.

THE VALVES IN THE VEINS.

Dissect back the skin from the throat of the rabbit, cat, or
dog, till the jugular veins are well exposed. Let the head of
the animal hang over the edge of the table ; note that as the
blood presses back toward the head it causes marked bulging
at certain points ; with the handle of the forceps slightly stroke

142 Practical Zoology.

the vein toward the head, watching the bulgings. Dissect out
the jugular vein from the head to the shoulder ; insert the nozzle
of a syringe, first into one end and then into the other, and
show the effect of forcing currents in each direction. Cut the
vein open along one side, pin inside out to a piece of a shingle,
and examine the thin, pocketlike valves. Test the elasticity of
the vein. Note the smoothness of its inner coat. Remove a
piece of an artery and experiment in the same way with it.

THE KIDNEY.

The structure of the rabbit's kidney may be made out by the
following directions, but the sheep's kidney, being larger and
essentially similar, may be conveniently used. If the sheep
kidney be used, its dissection may be made later.

1. Observe the depression in the inner border of the kidney,
the hilum.

2. From the hilum trace a slender white tube, the ureter, back
to the bladder. Find also the renal artery and vein, branching
as they enter the kidney through the hilum.

3. With a sharp knife split the kidney like a bean, beginning
at the outer border, stopping the cut when a white membrane is
reached near the hilum. With forceps pry about to explore the
cavity between this white membrane and the body of the kidney.
Note the branches of this cavity into the kidney. Note also the
extension of the white membrane into these cavities. Make out
that the blood tubes extend through these white branches to the
outer parts of the kidney. Count these branches.

4. In the center of the white membrane find the opening of
t\]e ureter, by which the urine is conveyed to the bladder. Pass
a probe through this opening into the ureter.

5. Note the difference in color of the outer and inner parts of
the kidney. At the line of change of color find where the blood
tubes first branch into the real kidney substance. Examine
carefully the cut surface of the kidney to see its markings.

Mammalia. 143

6. Make a drawing of one half of the kidney as seen from the
inside, showing all the above-named points.

7. Cut across the middle of the kidney at right angles to its
length, and make a drawing of this cross section. The projec-
tion of the kidney substance into the cavity opposite the ureter
is the urinary pyramid, and from its apex, from many fine holes,
issues the urine which the kidney has secreted from the blood.

DISSECTION OF THE HEAD OF A RABBIT.

1 . Remove the skin from the head. Observe the cartilages of
the ears and cut them off close to the head.

2. Below and back of the ear is an irregular pinkish mass, the
parotid salivary gland. The duct which conveys the saliva runs
forward over the cheek and opens on the inside of it. The
duct is usually hard to see, as it is thin-walled, slender, and of
about the same color as the sheaths of the muscles on which it
lies. It may easily be mistaken for a nerve, several of which
should now be in sight. This duct is much more readily traced
in a dog. With sharp, fine pointed scissors cut into the edge of
the duct, insert a black bristle, and push toward the front.

3. Just back of the angle of the lower jaw find a roundish
body, the submaxillary salivary gland. Its duct runs forward
inside the lower jaw and opens under the front part of the
tongue. It is rather difficult to trace in the rabbit, but is much
easier in the dog.

4. The infraorbital gland is just below the front of the eye
and its duct opens near that of the parotid gland.

5. The sublingual gland is a small, slender gland close to the
inside of the lower jaw in front of the base of the tongue, and its
duct opens near that of the submaxillary.

6. Observe the muscle that covers the outside of the back
part of each lower jaw. This is the masseter muscle. Place the
fingers on the angles of your own jaw and note the action of
the masseter muscles in shutting the teeth firmly together.
In the rabbit note the attachment of the masseter muscle to the

144 Practical Zoology.

under edge of the cheek bone. Trim the muscle entirely away,
noting carefully all its connections.

7. The temporal muscle is attached to the thin wing, or
process, of the jaw in front of the hinge, and passes up inside
of the arch of the cheek bone and spreads over the temple.
The shortening of the masseter and temporal muscles is what
shuts the jaws together. Remove this muscle, observing closely
all its relations. Place the tips of the fingers on your temples
and shut the teeth firmly together ; the hardening of the tem-
poral muscle is felt.

8. After removing the submaxillary glands a muscle may be
found on each side attached to the inside of each half-jaw near
their union in front. These are the digastric muscles; prove
that when they shorten they depress the lower jaw. Trace these
muscles to their connections at both ends. Review these points
till you see clearly how the jaw is opened and shut.

9. Cut away the soft membrane on the side of the mouth.
Note its inner surface. Split the two halves of the lower jaw
apart in front by a strong knife used from below. Entirely re-
move one half-jaw, noting a muscle attached to the inner surface
of the back part of the jaw. Look at its inner side for the hole
where the nerve and blood tubes entered it. Do you find a
hole on the outside of the jaw ?

10. Examine the tongue; how much of the space does it fiU
when the mouth is closed ? What is its shape ? The projections
on its surface are called the papillae.

11. Examine the roof of the mouth. Press against it to find
whether or not there is bone back of the soft membrane. This
is the hard palate ; note any markings or peculiarities of appear-
ance. Follow it back till you reach the soft palate, which has
no bony wall just beyond it. Follow the soft palate back,
cutting away as much as is necessary of the lateral wall, making
the opening cut along the level where the teeth meet.

12. Back of the soft palate is the cavity called the pharynx;
it is a continuation of the mouth. Trace forward the passage

Mammalia. 145

from the pharynx, over the soft palate, into the nasal passages
above the hard palate. Trace the pharynx downward and
backward to two passageways ; the farther one is the gullet, or
food tube, leading to the stomach ; the nearer opening i3 the
glottis, or opening to the windpipe, leading to the lungs. Be-
tween the glottis and the base of the tongue find the epiglottis,
a spoon-shaped cartilage, which most of the time stands up
close to the base of the tongue ; but when food passes it turns
down and back and covers the glottis, so that food does not
enter the air tube. Study these parts and their movements till
their action is clear to you.

13. Split the soft palate and turn the parts aside to find on
the sides of the pharynx the small openings of the Eustachian
tubes, that lead outward on each side to the cavity of the middle
ear.

CHAPTER XIV.

MAMMALIA {Concluded^,

The Brain and Spinal Cord of the Rabbit. — It will be found
helpful to have at hand a well-mounted skeleton of a cat or
rabbit. Note carefully {a) the cavity of the cranium, {p) the
cavity in the spinal column, and (r) the sides of each neural
ring where the bone is to be cut by the bone forceps, as indi-
cated in Figure i.

1

Fig. I. Diagram for dissecting Spinal Cord.

I. Cut along I 2 with cartilage knife. 2. Cut along 3 2 with cartilage knife.

3. Cut along 4 with bone forceps.

It is best to remove the skin completely before beginning the
work, as the fur is likely to be troublesome.

Cut away the muscles from the back of the neck and along
the sides of the backbone. This can be done rapidly by making
long, deep cuts with the cartilage knife along the sides of the
backbone, in the planes indicated in the accompanying figure.

146

Mammalia. 147

Between the skull and the first vertebra is a space covered
by a thin membrane, through which the spinal cord may be seen.
Carefully cut through this membrane, and insert the point of one
blade of a pair of bone forceps at one side of the spinal cord.
Cut through this side of the arch of the vertebra ; repeat this on
the other side, and so on, through the whole length of the spinal
column, removing the dorsal parts of the vertebrae, held together
in one strip by the connective tissue. The bony cavity in which
the spinal cord lies is the neural cavity.

The work may be more easily done if the rabbit is supported
on the edge of a short piece of " two by four " scantling nailed
to a baseboard eight inches wide and a foot and a half long.

Now look for the spinal nerves, which leave the spinal cord
in pairs, right and left, between the successive vertebrae. It
will probably be necessary to cut away considerably more bone
to expose the nerves. The whole of this work requires the utmost
care and patience, and involves a good deal of hard labor.

Note carefully the variations in the diameter of the spinal
cord in its course. The anterior swelling is called the cervi-
cal enlargement, and the posterior is the lumbar enlargement.

When the spinal nerves have all been laid bare, count and
compare them in reference to : (i) size ; (2) intervals between
successive pairs ; (3) angles at which they leave the spinal cord.

Carefully cut away the bone around some of the nerves in
the region of the shoulder, and find the two roots by which
each nerve is connected with the cord, one nearer the back,
the dorsal root, and one nearer the ventral surface of the body,
the ventral root. Trace these two roots, and note that they unite
and form a spinal nerve.

On the dorsal root, just before it joins the ventral, is a small
swelling, the ganglion of the dorsal root.

In the region of the shoulder carefully trace several of the
nerves as they unite to form the brachial plexus, from which
nerves supply the fore limb.

In the region of the hips trace several of the spinal nerves

148 Practical Zoology.

to their union in the large sciatic nerve, which runs down the
thigh.

Turn now to the head, and cut into the bone between the
eyes. Cautiously working backward, the whole of the brain
may be unroofed. Great care must be exercised, for here we
have one of the softest of the tissues of the body lying very
closely beneath one of the hardest. It is possible to do this
work with a strong knife, but the bone forceps save a vast
amount of extra work. The bone must be broken away bit by
bit.

Compare the color of the brain with that of the spinal cord.

The tough membrane covering the brain is the dura mater.

The fore part of the brain is the cerebrum. Note the groove
separating it into the right and left hemispheres. Observe the
ridges, or convolutions, of its surface. The prolongations of the
brain between the eyes are the olfactory lobes.

Back of the cerebrum is the cerebellum. Look at the human
skull to see whether there is a bony partition corresponding to
that which separates the cerebrum from the cerebellum in the
rabbit.

The widening part of the spinal cord within the skull is the
spinal bulb.

Make a drawing of the brain and spinal cord, showing as
many as possible of the points above noted. If desired, the
brain and cord, with a short part of each nerve, may be re-
moved from the body and laid on a cushion of cotton in weak
alcohol.

Directions for preparing the Brain of a Cat or Rabbit. — Direc-
tions have been given above for uncovering the brain. To
remove the brain, it will be necessary to cut through the tough
dura mater that covers it.

Removing this, there will be found an inner covering, the
pia mater, a membrane richly supplied with blood tubes, from
which the brain gets its nourishment. After the dura mater has
b«en removed, the anterior end of the brain may be gently lifted

Mammalia.

49

with the handle of the scalpel and the under surface studied,
following the directions in finding the cranial nerves.

The brain may be studied while it is fresh, but it is more
easily handled after it has been hardened. Lay the brain in
weak alcohol, about twenty-five per cent. It should rest on a
layer of cotton, otherwise it may be very much flattened by its
own weight, and get a good deal out of shape. Later transfer
it to fifty per cent alcohol, and then to seventy-five per cent ; or
use a solution of alcohol and formalin as follows : ninety-five
per cent alcohol, sixty parts ; two per cent formalin, forty parts.
The liquid need not be changed if used in sufficient volume.
When it is well hardened, it may be sliced with a sharp scalpel
as directed.

The Brain of the Rabbit {Alcoholic Specimen). — The brain of a
cat or dog is better, being larger. Take a brain well hardened,
and review the parts as named above. It is very desirable to
have a specimen in which the arteries have been injected.

1. Press down the cerebellum, to see the deep groove between
it and the cerebrum. The thin membrane covering the brain
and dipping into the grooves is the pia mater.

2. Press down the spinal bulb and tear away the pia mater
where it passes from the cerebellum to the spinal bulb. Note,
between the bulb and the cerebellum, a space covered by a thin
membrane. Cut into this membrane ; the cavity is the fourth
ventricle of the brain. Observe the two ridges bounding the
sides of the fourth ventricle. At the point of their divergence,
observe the opening of the central canal of the spinal cord.

3. Gently separate the cerebral hemispheres, and note the
transverse band of white fibers connecting them.

4. Examine the under surface of the brain, and find the roots
of the cranial nerves.

The Cranial Nerves. — i . The olfactory lobes (probably cut or
broken off) extend forward from the fore part of the cerebral
hemispheres.

2. Note that the optic nerves join each other before reaching

150 Practical Zoology.

the brain. Only the first and second pairs of cranial nerves
directly enter the cerebrum.

3. Back of the optic nerves, near the middle line, is the third
pair of nerves.

4. The fourth pair extend up on each side into the groove
between the cerebrum and the cerebellum.

5. Back of these is the larger fifth pair. This pair supplies
part of the face, and sends branches to the teeth. It is the
nerve affected in neuralgia of the face.

6. Back of and inside of the fifth pair is the sixth pair.

7. The nerves of the seventh pair are larger, and are farther
back and outward. These are the facial nerves, and control the
muscles of the face and the facial expression.

8. Close to the seventh are the eighth, or auditory nerves.

9. The ninth, tenth, and eleventh arise close together, farther
back and well up on the sides of the spinal bulb.

10. The ninth supplies the back of tongue and the pharynx,
and is called the glosso-pharyngeal nerve.

11. The tenth pair pass down out of the brain cavity, give
off branches to the pharynx and larynx, and are distributed to
the heart, lungs, and stomach. These are the vagus nerves.

12. The last pair of cranial nerves, the twelfth, arise near the
middle line of the spinal bulb. This pair supply the muscles of
the tongue, and are called the hypoglossal nerves.

Draw the brain as seen from below, showing all these nerves.

Separate the cerebral hemispheres, and with a sharp knife
split the brain lengthwise in the middle line. Make a drawing
of the inner face of one half. Note the branched appearance,
the arbor vitae, of the cerebellum. Trace the cavities of the
brain.

THE LEGS OF THE RABBIT.

Most of the following structures may be made out from a
shin bone of a sheep, readily obtained from the butcher.

I. After removing the skin from the legs, observe the muscles.

Mammalia. 1 51

covered by a thin, glistening membrane, the muscle sheath.
Study the shapes of the muscles.

2. In the hind limb of the rabbit observe the heel cord, or
Achilles tendon, passing upward from the heel along the back
of the leg. The tendon is the termination of the calf muscle,
which lies on the back of the shin bone. Trace this muscle
toward the body, and note that it passes between two large, flat
muscles, one on the inner, the other on the outer, back part of
the thigh. Separate these two flat muscles, using mainly the
handle of the scalpel. Remove any fat that may be in the way.
Deeply embedded between these muscles is a white cord, the
sciatic nerve. Trace this nerve toward the body, cutting away
any muscles or soft tissue covering it. How far can you trace
it? Now follow the nerve outward. Is it of the same size
throughout? What are its relations to the muscles?

3. Study carefully the calf muscle, its shape, color, covering,
ends, etc. The end by which its tendon is attached to the heel
bone is the insertion ; the other, less movable end is the origin.
From what bone does it arise, and by how many tendons ? Cut
across the muscle at its thickest part, the belly of the muscle,
and study its structure. Note that the tendons at the ends
of the muscle are continuous with the muscle sheath and
with the partitions running through the muscle. Pull the tendon
toward the body ; this straightens, or extends, the foot ; the calf
muscle is therefore called an extensor muscle. With the handle
of the scalpel loosen the muscle on the front of the shin bone ;
prove that its action is to bend, or flex, the foot. It is a flexor.
Find its origin and insertion.

4. By further dissection find how the different movements of
the toes are effected.

5. Cut into the knee joint. Observe the liquid, the synovia,
which oils the joint. Rub a drop of it between the thumb and finger.

6. Observe the glistening bands which hold the ends of the
bones together. These are the ligaments. Carefully study
their arrangement and uses.

152 Practical Zoology.

7. Note the thin layer of cartilage over the ends of th«
bones. Feel of it. Cut it. What are its properties, and what
its uses ?

8. With the forceps strip off a little of the muscle sheath from
one of the muscles and note the color of the latter. Cut one of
the muscles across in its middle and examine the cross section.
Each fiber has its own thin sheath, and the small bundles of
fibers have separate sheaths, which make the white markings
seen in chipped dried beef.

9. Tear off a few fine fibers of the muscle, mount on a slide
in water or glycerine, cover with a cover slip, and examine first
with a low and then with a high power. The fine cross-
markings of the fibers give to this kind of muscle the name of
striped, or striated, muscle.

10. The covering of the bones is the periosteum. Thoroughly
clean one of the long bones and make a drawing of it. Saw it
m two lengthwise and make a drawing of the surface thus ex-
posed. Put a bone into weak acid, and after a day or two com-
pare it with another that has been burned.

THE MUSCLES OF THE EYEBALL.

With bone forceps, or a strong knife, cut away the bone at the
outer angle of the eye socket of the rabbit (almost any mammal
will serve for this, but the bone is so thick in the calf or sheep
that it will be difficult work without the aid of a good pair of bone
forceps) .

1. With scissors trim away the white, membrane around the
front of the white of the eye ; this was continuous with the lining
of the eyelid, and is the conjunctiva.

2. Find a muscle running along the roof of the eye socket,
which passes over a loop of tendon, near the edge of the orbit,
and turns outward to its attachment to the top of the eyeball.
This is the superior oblique muscle.

3. Beneath the eye find a muscle, having its origin in the
inner front part of the socket, and passing outward to be

Mammalia. 153

inserted in the lower surface of the eyeball ; this is the inferioi
oblique muscle.

4. Four straight muscles, the superior rectus, inferior rectus,
internal rectus, and external rectus, are attached to the top, bot-
tom, and sides of the eyeball ; find the origin of these, with that
of the superior obhque, at the bottom of the eye socket.

5. Dissect away the fat and other tissue around these muscles,
and find a cone-shaped muscle attached to the back of the eye.
Within this find the cylindrical optic nerve.

External Parts of the Eye. — The eye of the rabbit may be
used, but that of the ox is better.

1 . Observe the clear front part of the eye, the cornea. Note
its shape. Its wider end was at the inner angle of the eyelids.

2. Around the cornea find a whitish membrane, the conjunctiva,
which, a short distance back from the cornea, separates from
the eyeball to turn forward and line the eyelid.

3. The several muscles of the eyeball, a mass of fat which
forms a cushion for the eye, and other tissue, should be trimmed
away, leaving the optic nerve.

4. Place the eye in its natural position, and make drawings
of it, as seen from the front and from one side, naming the
parts.

Dissection of the Eye. — Beef eyes are of good size for dis-
section. Each member of the class should have an eye to
dissect. To supply a large class it is best to send to a slaugh-
tering house in the nearest large city. If the eye muscles and
other external parts have already been studied, it will not be
necessary to remove the muscles and fat around the eye ; in
fact, they may well be left untouched, as they serve as a cushion
to support the eye during dissection. The eye may be con-
veniently dissected on a small piece of board or shingle ; and
if it is desirable to turn the eye, it is better to do so by turning
the support, as the eye usually sticks to the support and the dis-
section may be injured by trying to move it.

Caution. — After the eye is opened be careful not to compress

1^4 Practical Zoology.

it. If the eye be held hi the hand while trying to cut its tough
outer coat, the jellylike contents are easily squeezed out, ruin-
ing the dissection. Let the eye rest on the board all the time, and
after first cutting into the cornea it is not necessary nor ad-
visable to touch it with the fingers. When studying the lens, be
very careful to tip it up gently and compare its front and back
surfaces before removing it from the eye..

1. Lay the eye on the board, with the cornea uppermost.
Hold the eye firmly with the thumb and fingers of one hand ;
with the thumb and forefinger of the other hand hold the blade
of the scalpel half an inch from its tip ; with a steady motion
push the blade horizontally through the cornea, near its edge.

2. The liquid in the cavity back of the cornea is the aqueous
humor.

3. Slightly enlarge the cut horizontally ; then with the forceps
take hold of the upper edge of the cut, and with the scissors
cut around the margin of the cornea and remove it.

4. The dark membrane now exposed is the iris. Pinch the
eye slightly at the sides to make the iris show more distinctly.
The hole in its center is the pupil. With the forceps raise the
edge of the iris around the margin of the pupil to see that it is
here unattached to the structures underneath. Observe the
color and markings of the iris.

5. From one end of the pupil cut outward to the outer
margin of the iris ; then cut arouuJ its outer margin and re-
move it. Observe the color and markings of the posterior
surface.

6. The body now laid bare is the crystalline lens. Touch it.

7. Lay a piece of newspaper close to the eye, on which to
receive the lens, which sometimes pops out suddenly. With
a very sharp blade make a quick, light gash across the surface
of the lens to cut through the thin coat which envelops it, the lens
capsule. Usually the lens may be made to come out by applying
gentle pressure to the sides of the eye with the thumb and finger.
If not, enlarge the opening thus made, and carefully pry up the

Mammalia. 155

lens with the handle of the forceps, noting closely, in so doing,
the difference between the front and back surfaces. Lay the
tens on the piece of newspaper, and look through it at the letters.
Make a drawing of the lens as seen from the front, and as seen
from one side, naming the front and back surfaces.

8. (Caution. — In removing the strip of eye coating, as di-
rected below, be extremely careful not to drag the clear, jelly-
like vitreous humor. The strip must not be unwound, as in
peeling an apple, but must be left in place. The parts must be
lifted gently by the forceps, and the clear, jellyHke mass must
be cut through horizontiUy, with the scissors.) With the scissors
now cut outward about one half of an inch from the edge of the
hole made in front of the eye, merely cutting through the outer
wall of the eye. Beginning at the lower end of this last cut, with
scissors cut through the coats of the eye, horizontally, all around
the eye. With forceps take hold of the upper edge of the coats
of the eye, and lift very gently and steadily while cutting horizon-
tally through the jellylike contents of the eye, in the plane of the
circular cut just made. Lay the part thus cut off wrong side up
on the board. On the inside of the strip removed there may be
found radiating black ridges, the ciliary processes.

9. Carefully pick away with the forceps, and snip away with
the scissors, everything on the surface of the clear mass beneath.

10. The substance filling the remainder of the eye cavity is
the vitreous humor.

11. Through the vitreous humor the entrance of the optic
nerve may be seen with the blood tubes radiating from it. If
necessary, carry the dissecting board to a window to let the light
enter from above.

12. The tough outer coat of the eye is the sclerotic coat.

13. Inside the sclerotic is the dark choroid coat.

14. The inner, nearly transparent, pinkish or whitish coat is
the retina. At this stage of the dissection it has probably become
slightly wrinkled, and the white ridges may be seen radiating from
the entrance of the optic nerve.

156 Practical Zoology.

Drag out the vitreous humor and note the soft whitish 01
pinkish retina; observe that it is a continuation of the optic
nerve. Tear away the retina, noting its consistency. Note the
color and luster of the inner surface of the choroid coat. The
dark layer on the inside of the choroid coat is the pigment layer
(outer part) of the retina, which adheres to the choroid, and is
torn loose from the rest of the retina.

The reflection of light from this surface of the choroid coat
causes the color seen in the eyes of some animals. Turn the
remaining coats inside out, and tear the choroid coat from the
sclerotic. Observe the blood tubes passing from one to the other.

DISSECTION OF THE LARYNX.

The Larynx of the Calf. (As the larynx of the rabbit is so
small, it will be better to examine a larger one.) — i. The front
of the larynx is readily distinguished by the projection of cartilage
known as the Adam's apple.

2. Along the back of the larynx runs a thick, muscular tube, the
gullet, with a whitish lining, the mucous membrane.

3. Trim away the muscles and other tissues from the front and
sides of the larynx. The large cartilage forming the greater part
of the front of the larynx is the thyroid cartilage.

4. Observe the band of muscles attached to either side of
the thyroid cartilage and passing horizontally back around the
gullet or esophagus.

Cut away this muscle as completely as possible, and entirely
remove the gullet. Note that the whitish or yellowish mucous
membrane which lines the gullet is continuous with the lining
of the larynx. Study now more fully the shape of the thyroid
cartilage.

5. Back of the upper part of the thyroid cartilage, covering
the upper end of the larynx, is the arched epiglottis. Feel of
it to learn its consistency. Press it upward and forward, then
downward and backward ; observe that it now covers the entrance
to the larynx ; note the position it takes when released.

Mammalia.

157

I

6. Just back of the upper angle of the thyroid cartilage find
a muscle connected with the base of the epiglottis; pull this
muscle to determine what effect its shortening produces on the
epiglottis.

7. Under the thyroid cartilage in front observe a narrow ring
of cartilage not much wider than one of the rings of the trachea.
Move this up and down to prove that it is distinct from the thy-
roid. This is the cricoid cartilage.

8. Observe the sheet of muscle passing from the cricoid to the
thyroid. Again move the cricoid toward and from the thyroid.
What does this muscle do ? Cut away this muscle from one side,
and see that the cricoid cartilage widens as it passes backward.
How are the cricoid and thyroid hinged together ?

9. Projecting upward and backward from the top of the larynx
are two curved yellowish cartilages, the arytenoid cartilages.
Move them about to see that they are movable, and that they
rest on the upper edge of the back part of the cricoid cartilage.

10. Move the arytenoid cartilages backward and forward, mean-
while watching the inside of the larynx from its lower opening.
The projecting ridges, which meet just back of the Adam*s apple,
are the vocal cords. What effect is produced on the vocal cords
by the movements of the arytenoid cartilages?

11. Observe the connection of the thyroid cartilage with the
cricoid by means of a downward projection of the former. Cut
away all of this half of the thyroid cartilage. Notice the slender
hyoid bone loosely connected with the upper horn of the thyroid.

12. Examine now the muscles which move the arytenoid
cartilages.

a. On each side of the posterior surface of the cricoid is
a muscle passing upward to be attached to the corresponding
arytenoid ; this is the posterior crico- arytenoid muscle. Dissect it
loose from the cricoid at its origin below. By pulling, determine its
action on the arytenoid, and through the arytenoid on the vocal cord.

b. Arising from the upper edge of the side of the cricoid
cartilage, and passing upward and backward to the arytenoid, is

158 Practical Zoology.

the lateral crico-arytenoid muscle ; cut it away at its origin close
to the cricoid, and demonstrate its action on the arytenoid cartilage
and vocal cord.

c. A broad muscle arising along the whole length of the angle
of the thyroid, whose fibers converge to the arytenoid cartilage.
This is the thyro-arytenoid muscle ; cut it across near its origin,
dissect it loose, and by pulling it toward its origin prove itf,
action.

d. On the posterior surface of the arytenoids is the small
arytenoid muscle.

13. Cut between the arytenoid cartilages and remove one of
them. Examine the joint between the arytenoid and cricoid.
Note the synovia lubricating the joint.

Trim away the muscle from the arytenoid cartilage and study
its shape more fully. Fit it again to its place, and recall the
motions given by each muscle.

14. Now examine the arytenoid cartilage and the vocal cord
of the opposite side ; move the arytenoid back and forth, watch-
ing the vocal cord.

15. Remove the epiglottis, and cut into it to see its structure.

16. Dissect away the parts of the other side from the inside,
reviewing the above points.

THE SKELETON OF THE RABBIT.

Carefully clean the skeleton after dissecting away the muscles.

.In preparing the skeleton in this way the student will learn many

facts as to the relations of the bones to the other tissues, that

he would not learn if he began with a well-mounted museum

skeleton.

In removing the muscles, observe that the muscles of the
limbs lie parallel to the bones ; that the bones are largest at the
ends, while the muscles are thickest near the middle, thus
making the two fit each other better. Note that in the limbs
the muscles narrow at one end, or both, into a tendon, which,
usually at one end, passes over a joint to be attached to a bone

MammaHa. 159

in the next part of the limb. Examine the ligaments that hold
the adjoining ends of the bones together. Examine the
cartilage on the end of the bones. Between the ends of the
bones of the limbs, note a small quantity of slippery liquid, the
synovia. In cleaning the bones, notice the nerves and blood
tubes passing in and out of the holes along the sides of the
bones.

Weigh a rabbit, freshly killed, but from which the blood has
not been removed. Thoroughly clean the skeleton, and when it
is dry, weigh it. What part of the whole weight of a rabbit is
the skeleton ?

1. The skeleton consists of two parts, the axial part, made up
of the skull and spinal column, artd the appendicular part,
consisting of the limbs and the bones supporting them.

2. In the skull, the joints are called sutures. The bones
surrounding the brain constitute the cranial part ; those parts in
front make up the facial part. Note that the face is large,
compared to the cranium. How do these two parts compare in
the rabbit, dog, horse, frog, ape, and man ? Why so much
difference ? Note the cavities and apertures in the skull : the
brain cavity; the opening (foramen magnum) through which the
spinal cord passes to join the brain ; the cavity, or orbit, of
the eye, with its holes for the optic nerve ; the nasal apertures at
the front of the snout ; the auditory apertures, or ear holes. On
each side of the foramen is a smooth, rounded elevation ; these
are the occipital condyles. See how they fit the first vertebra ;
what kind of a joint do they make ? Study again the way the
lower jaw joins the skull, and consider the motions that this joint
permits. Compare it with the corresponding joints in the
skulls of a cat, cow, and man.

3. Make a more careful study of the teeth than before, as
they are now fully exposed. The front teeth are the incisors ;
what is their shape ? How many above ? How many below ?
Are they all alike? How are they arranged ? Are they all
marked alike ? How do the upper and lower incisors meet, —

i6o Practical Zoology,

squarely, edge to edge, or does one pair naturally rest back of
the others ? If so, which are in front in the resting position ?
Can the lower jaw be moved forward and back ? Do the lower
incisors always come up in the same position in relation to the
upper incisors ? Note the angle at which the incisors are set.
Now examine the grinding teeth, or molars. How many are
there in each half-jaw? What is their shape? Are there
ridges on their grinding surfaces ? If so, in what direction do
they run ? How is this related to the chief chewing motion ?
Are all the molars set at the same angle ? Why any difference ?
At this point, if possible, look again at a live rabbit and watch
the process of eating. How are the jaws moved, and how do
the motions stand related 'to all these facts about the teeth ?

4. Take a well-cleaned lower jaw of a rabbit. Embed it in
sealing wax on a small block of wood, with the inner face of the
jaw uppermost. With a grindstone, grind away half of the
incisor and the surrounding jawbone. Is there a distinct root ?
Is the tooth equally hard throughout? The front part is enamel.
The bulk of the tooth consists of dentine, or ivory. Grind away
half of the molars and the bone in which they are set. Do any
of these teeth continue growing after the rabbit has reached
maturity ? Is it a serious matter for a rabbit to lose one of its
front teeth ? Why ?

5. Each separate piece of the backbone is a vertebra. The
vertebrae of the neck are called cervical vertebrae. The vertebrae
that bear ribs are thoracic. Following the thoracic vertebrae are
the lumbar vertebrae. After these, are several grown together
and supporting the bones of the pelvis ; they constitute the
sacrum. Last, the vertebrae of the tail, the caudal vertebrae. How
many are there of each of these kinds ? How many in all ?
Review the whole spinal column, comparing the different parts.

Take a vertebra from the middle of the thorax and examine it
carefully. Its main part is the body or centrum. On the dorsal
side is an arch, the neural arch, through which the spinal cord
passed. Above the arch is a projection, the neural spine, the

Mammalia. i6i

row of neural spines forming the ridge of the backbone.
Extending outward on each side are the two transverse processes.
Near the end, on the dorsal surface, are the two smooth facets,
where the vertebra joined the vertebrae before and behind it;
these are the articulating processes. Do all the vertebrae have
the same number of the processes ? Where the same number
is present are they alike ? What range of motion is allowed
between two vertebrae? Is this equal in different parts of the
spinal column ?

6. Study carefully the first and second vertebrae. The first is
the atlas. Has it a body ? Note how the two hollowed facets
on each side of the hole fit the two occipital condyles of the base
of the skull. How is the nodding motion of the head accom-
plished ? The second vertebra is the axis. Projecting forward
from it is a peg which extends into the opening in the atlas ;
this peg is the odontoid process. Observe that when the head
turns from side to side it is by turning on this axis.

7. Examine one of the middle ribs. Find that it joins the
backbone in two places, by its head on the side of the vertebra,
and by a little projection called the tubercle, with the tip of a
transverse process. What range of motion has a rib? Note
that at the ventral end the rib is cartilaginous. What is the
advantage of this fact ? Compare the series of ribs. Examine
the breastbone. Is it of one piece ? Is there any cartilage in
it ? What are the uses of the ribs ? Is there a collar bone ?

8. In the fore limb look at the shoulder blade or scapula.
How does it make up in strength for its thinness ? Why should
it be flat ? Note the shallow cavity by which it articulates with
the bone of the upper arm, the humerus. This is a ball-and-
socket joint. Look closely for a slender collar bone, or clavicle.
In the forearm the longer bone is the ulna; the other is the
radius. Do they rotate on each other as in our forearms?
Compare them also with the corresponding bones of a cat. Do
they need the same freedom of motion as in a cat, squirrel, ape,
or man ? The bones of the wrist are the carpal bones. The

1 62 Practical Zoology.

bones of the palm are the metacarpal bones. Beyond them are
the finger bones, or phalanges. Find how many there are of
each of these sets.

9. In the hind limb each half of the pelvis consists of the long
hip, or innominate bone. Note the deep socket of the ball-and-
socket joint. Fitting into this is the romided head of the femur,
or thigh bone. Compare this joint with that of the shoulder.
Which has the greater range of motion ? Which the greater
strength ? Study the kneejoint. Note the kneepan, or patella,
in the tendon running over the kneejoint. The large bone of
the leg, or shank, is the tibia. Beside it is the fibula; is it
wholly free from the tibia ? If it is found united with the tibia,
where and to what extent ? Corresponding to the carpus of the
wrist, there is a series of short bones in the foot constituting
the tarsus. Then comes a row of longer bones, the metatarsal
bones. And after these are the toe bones or the phalanges. How
many in each of these series and how arranged ? Are the bones
of the same number as in the fore limbs ?

CHAPTER XV.
PROTOZOA.

AMCEBA.

Amgeb^e are to be found in standing water, where they live in
the slimy coating on the leaves and stems of submerged plants,
or on the upper layer of mud or ooze at the bottom. Such water
with mud and plants should be collected sometime beforehand
and kept undisturbed in the laboratory.

1. Take a drop of water from the bottom or the surface of a
leaf, mount on a slide, and cover with a cover slip. Examine
with a high power of the microscope, using a one-fifth or a
one-sixth inch objective.

2. General Appearance. — An amoeba looks like a small drop
of clear jelly, but after watching it a short time it may be seen
to change its form. The body is composed of a substance called
protoplasm.

3. Structure. — The following parts should be identified : —

a. A clear outer margin, the ectosarc.

b. A dotted or granular inner portion, the endosarc.

c. A denser, spherical body within the endosarc is the nucleus.

d. A clear space that from time to time contracts and dis-
appears. This is the contractile vesicle or vacuole. Are its
pulsations regular? Time them.

e. Other vacuoles that do not pulsate but are filled with
granules of food materials. These are called food vacuoles.

4. Movements. — Watching the amoeba closely shows that it
not only changes its form, but also its position ; it not only
moves, but moves from place to place. It has not only motion,
but locomotion. By closely watching an amoeba it may be seen

163

164 Practical Zoology.

that at one place there is a bulging out of the ectosarc, some-
times forming a long projection called a pseudopod. The granu-
lar endosarc then flows into this projection, and by repetition of
this process the whole amoeba moves forward. Is there any
part that can be called the head ? Does it move constantly in
any one direction ? Make sketches at intervals to show the
changes in form.

5. Feeding. — It may be discovered that occasionally an amoeba
ingulfs a particle with which it comes in contact. This is its
mode of eating, for it has no mouth. Does it show choice in
what it thus takes in ? Is there any refuse of digestion ? If so,
where and how does it leave the body ?

6. Feeling. — Does the amoeba ever appear to feel an object
against which it presses ? Does it avoid obstacles ? What evi-
dences as to its having a sense of touch ?

7. Reproduction. — Can you find an amoeba that is dividing
into two parts ? This is its simple mode of reproducing, and is
called division or fission. If possible, find out how long it takes
to complete the division. Make sketches to show the process
of division.

PARAMECIUM, THE SLIPPER ANIMALCULE.

Paramecia are often found in water containing decaying ani-
mal or vegetable matter. If a white film forms on the sur-
face of such water, look through the sides of the jar, and there
may often be discovered tiny white particles moving actively
about. Mount a drop of this water, with a little of the scum,
and examine with a low power of the microscope, say a two-
thirds or one-fourth inch objective. Small oval or elliptical
bodies may be seen swimming around at a lively rate. These
are paramecia. Find one that is fenced in by surrounding
matter, or prepare another mount ; a few threads of cotton often
serve well as a "corral." With a higher power, one fifth or
one sixth, examine a paramecium, whose movements are thus
restricted. Note : —

Protozoa. 165

1. The shape, oval or elliptical, often decidedly slipper-shaped.
It further resembles a slipper in being somewhat flattened.

2. Structure. — The clearer, firmer, outer layer is the ectosarc.
The more jellylike inner part is the endosarc. Covering the ecto-
sarc is a thin, transparent layer, the cuticle. Extending from the
ectosarc through the cuticle are many fine, hairlike projections, the
cilia. Near the center is a large, ovoid body, the macronucleus.
Beside it is the much smaller micronucleus. These nuclei are
hard to see. Place a little dilute acetic acid on the slide close
to the cover slip to bring out the two nuclei.

3. Locomotion. — The Paramecium swims by means of the
vibrations of the cilia. Does it swim with the same end always
foremost ? Does it change its shape ? Watch it when trying to
pass into a narrow opening. Are the cilia of the same size all
over the body ? Place a drop of iodine solution on the slide at
the edge of the cover slip. The cilia, thus stained, show
better.

4. Feeding. — Along one of the flattened surfaces find a groove,
the oral groove. Note the cilia lining this groove. Observe that,
near the center of the body, the oral groove becomes a tube
dipping into the body. The tube is the gullet, and its be-
ginning is the mouth. Sift finely powdered carmine or indigo
into the water, and watch to see the particles swept into the
gullet by the action of the cilia. The masses of particles that
accumulate at the end of the gullet become separated from the
gullet, and as distinct masses in the body are called food vacuoles.
Do the food vacuoles remain in the same place? Or do they
move about ? Do they move in any regular order ? Can you
find a place where the residue is expelled from the body ?

5 . Pulsating Vacuoles. — About one third of the way from each
end, look for a clear space, which contracts and disappears, and
then reappears ; these are the pulsating vacuoles, or contractile
vesicles. How often do they pulsate ? Which takes more time,
contraction or dilation ? Look closely for radiating canals after

1 66 Practical Zoology.

the disappearance of a vacuole. Do the two vacuoles contract
at the same time ?

6. Means of Defense. — Observe in the ectosarc many small,
oval sacs, with their ends toward the surface. These are the
thread cells. They contain a thread, which can be shot out, serv-
ing as a means of defense.

7. Reproduction. — Do you find a Paramecium that is becom-
ing constricted in the middle like a dumb-bell or hourglass?
Paramecium divides into two by narrowing in the middle, pre-
ceding which is a division of the nuclei. If such a specimen
can be found, watch the process to completion, if possible. Draw
and describe all the stages of division, or fission.

VORTICELLA, THE BELL ANIMALCULE.

Vorticellae are often found on the stems and leaves of water
plants, or on stems and leaves that have fallen into the water.
Mount slender stems from water and examine with a low power.
If you find a bell-shaped form attached by a slender, flexible
stalk, and especially if the stalk is suddenly thrown into a coil,
jerking the bell close to the stem to which it is attached, you
may be sure you have vorticella or a near relative. Some of
these forms occur in colonies, all growing from one main stalk.
Some have the power of coiling the stalk, while in others the
stalk is not contractile. Some of the colonies can be seen by the
naked eye, appearing like tiny spots of mold. If such a colony
is found, the part of the stem or leaf to which it is attached
should be carefully cut out and mounted on a slide. With a
higher power the details of form and structure may be studied.

I. Form and Structure. — The body is bell-shaped, with a
long, slender, flexible stalk in place of a handle. The outer
layer is a thin cuticle, next is the ectosarc, and the inner is the
endosarc. The extension which nearly fills the mouth of the
bell is the disk. The border of the bell is the peristome. On
one side find a groove between the disk and the peristome. This

Protozoa. 167

is the oral groove. Observe the cilia along the margins of the
disk and the peristome. The extension of this groove into the
body forms the gullet. Vorticella has a long, curved macro-
nucleus and a small, spherical micronucleus, but these are not
easily seen. Add a little dilute acetic acid.

2. Movements. — Observe carefully the stalk during and after
the coiling. The stalk does not contain any of the endosarc,
but only the ectosarc and cuticle. Note also the changes in the
shape of the body and the rearrangement of the parts. In what
order are the parts folded in during the act of closing, and in
what order are they expanded when the vorticella extends
again ? Tap on the slide while watching to see these changes.
Make sketches showing the fully expanded and the closed forms.
Why does the vorticella thus draw itself close to its support ?

3. Feeding and Digestion. — Watch the vibrations of the cilia.
Can you see that food particles are swept into the oral groove
and down to the blind end of the gullet ? Add powdered car-
mine or indigo to the water. Can you see food balls at various
points in the endosarc ? Are they stationary, or do they move ?
If they move, do they go in any regular order ? Look closely for
the expulsion of residue into one side of the gullet, and so out
by the return current. Does a vorticella move toward food ?
Could it do so ? Does it need to do so ? Does vorticella show
choice in the particles that it takes as food ?

4. Excretion. — Find the pulsating vacuole. Time its con-
tractions.

5 . Senses. — What senses does the vorticella appear to possess ?

6. Reproduction. — Look for two vorticellae on one stem. You
may find one in the early stages of division. When one of these
becomes separated, learn how it swims away. Study vorticellae
a long time to find out about the mode of development, making
sketches of what you observe.

Topics for Reports. — Chalk. Barbadoes Earth. Malaria.
Infusorial Earth.

CHAPTER XVI.
PORIFERA.

SPONGES.

Each pupil should have a small specimen of a commercial
sponge, showing large holes at the top, but not with large holes
running straight through.

The teacher will need several specimens of larger sponges ;
one of the simple calcareous sponges, in alcohol ; a piece of
commercial sponge in alcohol, showing the sponge flesh still in
place ; a siliceous sponge ; and slides showing sponge spicules.

The pupil should make out the following points from his
specimen of common sponge : —

1. Its elasticity; test first the specimen dry, and again after
wetting it. Compare the elasticity of different kinds of sponges.

2. The fibrous structure; with forceps tear off a bit of the
sponge and examine with a lens. Then examine under the
microscope.

3. The sponge was attached by its basal surface to rock.
Find where it has been trimmed away with shears ; perhaps if
this has not been thoroughly done, some bits of rock may be
found clinging to the base.

4. Examine now the different channels by which the sponge
is perforated.

a. Large, craterlike tubes, opening at the top of the sponge.
Looking into these, it may be seen that they give off branches.
If you can see right through the sponge by looking into these
openings, you may know that too much of the base has been cut
away, and your specimen is not a good one. With a razor or

16S

Porlfera. 169

sharp knife, cut the sponge in two down one of these large tubes,
and examine from the inside.

b. Trace the branches of the large tubes by gently pushing
into them a probe (a wire with a little knob on one end). These
lead, usually, to holes seen on the outside.

c. Grooves on the surface of the sponge, some shallow, others
already becoming inclosed by the union of the tufts of fibers
outside of them ; in this way is formed another set of tubes {d').

d. Tubes running parallel to the surface of the sponge, whose
cut-off ends may be seen near the margins of the split sponge.
Hold the half sponge up to the light to see the radiating fibers
and the concentric series of holes indicating the mode of growth
of the sponge.

e. Minute branches of the above tubes penetrating the sponge
in all directions.

It must be borne in mind that the sponges we buy are only
the skeletons of sponges. In the living sponge the skeleton is
entirely embedded in soft living matter, and the skeleton cannot
be seen on the exterior ; in fact, its fibers are not very evident
in a section of a fresh sponge. The outside of the sponges
whose skeletons we buy, when alive resembles, in color and gen-
eral appearance, the back of a kid glove, varying from dark
reddish brown to almost black. The consistency of the living
sponge is about the same as that of beef liver. If one of these
live sponges be watched, a current of water is found to come out
of the larger holes at the top, and currents pass in through the
numerous smaller holes on the exterior.

If the sponge be handled, many of the smaller holes close and
entirely disappear.

In order to understand a little more clearly the structure of
the common sponge, and to see how the currents of water are
maintained, an examination of a simple sponge will be useful.
Our simplest sponges have no elastic skeleton composed of
horny fibers like those of the commercial sponge, but have little
needle-shaped and three-pronged spicules of limy matter.

lyo Practical Zoology.

One form common on the northern Atlantic coast is a simple
or branched white tube, an inch or so in height, and sometimes
as thick as a pigeon's quill. These are in clusters, attached by
one end and open at the other. Embedded in the wall of each
tube are the spicules above mentioned, projecting both on the
outside and on the inside. The inside of the tube is lined with
cells bearing cilia w^hich, by their vibration, drive the contained
water out of the mouth of the tube ; to replace which, water
enters through many holes which pierce the wall of the tube. In
sponges a litde more complicated, the cilia, instead of lining
the main tube, are limited to small pouches, or lateral branches
of the main tube, extending into the body wall and communi-
cating with the exterior through small pores. In others the cilia
are found only in certain enlarged portions of these radiating
tubes. This represents the condition in the commercial sponges;
certain cavities are lined with cilia and are connected on the
one hand with the smaller tubes entering the whole surface of
the sponge, and on the other with the large tubes opening at the
top. These cilia cause the currents above mentioned. Thus
the sponge gets both food and oxygen.

Sponges (including, besides those already mentioned, siliceous
sponges, whose spicules are flinty) constitute the branch Porifera.

Read Commercial and Other Sponges, Hyatt.

Topics for Reports. — Sponge Fisheries. Experiences of
Divers. Sources of our Sponges. Fresh-water Sponges.

CHAPTER XVII.
CCELENTERATA.

THE FRESH-WATER HYDRA.

The fresh-water hydra has a cylindrical body, varying in
diameter from the size of a fine needle to that of a common pin,
and from one fourth to one half an inch in length. It is found
in fresh-water ponds and streams, usually attached by one end
to submerged stems, leaves, etc., frequently on the under surface
of a leaf. Surrounding the free end of the hydra is a circle of
threadlike appendages, the tentacles, which often are longer
than the body itself.

Two species of hydras are found: one green, the other brown
or flesh colored, often whitish. Put the leaves and stems to
which the hydras are attached into shallow dishes, such as fruit
dishes, and keep them in a light but shaded place ; watch their
behavior when thus kept undisturbed. Cut off a bit of leaf
bearing a hydra, and transfer it to a deep watch crystal half
full of water. Without the aid of any lens watch the hydra for
several minutes. When it is expanded, gently touch it with the
tip of a pencil or other blunt object.

Examine a hydra with a hand lens ; are all parts colored
alike ? Place the watch crystal on the stage of a microscope
and examine with a one-inch objective. The following points
of structure should now be made out : —

1. That the body is a hollow tube closed at one end and open
at the other. This opening, within the circle of the tentacles,
is the mouth.

2. That the tentacles are also hollow tubes, closed at their
outer ends, but at the inner communicating freely with the body
cavity.

171

172 Practical Zoology.

3. That the body wall consists of two layers, which are con-
tinuous with the corresponding layers of the tentacles. How do
these layers differ from each other ?

The body is, then, a double-walled sac, and the tentacles are
simply extensions of this sac. Watch the movements of the
different parts of the body. Can hydras move from place to
place ? If so, how is this accomplished ? Look in the body
cavity for foreign matter which has been taken in through the
mouth as food. Look also for minute particles obtained by the
digestion of such food matter. These particles may often be
seen in motion, caused by contractions of the body walls, or by
the action of flagella lining the body cavity. Look for knoblike
extensions of the side of the body. Buds are formed as out-
growths of the body walls with a cavity continuous with the
body cavity. Place in a dish by itself with some aquatic plants,
a hydra bearing buds, and watch from day to day the develop-
ment of the bud into the form of the parent. Observe the free
circulation of food material from the parent to the bud. Watch
the formation of tentacles. Look also for a thinning away of
the free end of the bud.

What is the greatest number of buds found on any one speci-
men ? Are buds borne on buds ? By means of a pipette trans-
fer a hydra in a large drop of water to a slide. Cut two strips
of paper a quarter of an inch long and one sixteenth of an inch
wide, and lay one on each side of the drop of water. Carefully
place the cover slip on the water, with its edges resting on the
papers so as not to crush the specimen.

Examine now with a quarter or one-fifth inch objective. Ob-
serve the cells of which the body walls are composed. Note
the knotty appearance of the tentacles. In these projections
of the tentacles and in the walls of the body are certain distinct
oval cells, the thread cells. Place a drop of acetic acid on the
slide at one edge of the cover slip, and touch the opposite edge
of the cover slip with a piece of blotting paper, meanwhile watch-
ing the specimen closely. Examine carefully to see the thread

Coelenterata. 173

cells which have been discharged as a result of the irritating
acid. Small animals coming in contact with the tentacles are
paralyzed by means of these thread cells which are suddenly
shot out ; the tentacles then carry the victim to the mouth, and
it is swallowed.

Note the simplicity of the structure of hydra — the absence of
any distinct nervous system, and all special organs of circulation
and respiration. On the side of a hydra, near the base, may
sometimes be seen a conical elevation, the ovary, in which the
eggs are produced. Also on the side of the body, but near the
tentacles, may sometimes be found several elevations, the sper-
maries, in which the sperm cells are produced.

THE SEA ANEMONE.

Look for sea anemones attached to rocks. The beginner in
this sort of collecting and observation is usually not prepared
for what he sees ; he does not usually realize that the name " sea
anemone " is exceedingly appropriate, and he is not likely to
look for brilliant forms, like sunflowers, asters, and chrysanthe-
mums. Watch them both in their expanded and in their con-
tracted condition. When they are expanded gently touch them.
Are they firmly or loosely attached ? Do they ever move about ?
Have they any means of getting food ?

In its general form the sea anemone resembles a hydra, having
a cylindrical, hollow body attached by one end to some foreign
object, and at the free end a mouth surrounded by tentacles.
In its internal structure, however, the sea anemone presents
some new features. The mouth, instead of opening directly into
the body cavity, as in the hydra, opens into an esophagus which
hangs like a bag suspended in this cavity ; the esophagus has no
bottom, but at its lower end communicates freely with the body
cavity.

The body wall and esophagus may be represented by a glove
finger with its tip cut off and the open end turned back part
way into the larger part of the finger.

174 Practical Zoology.

The cavity of the body is divided into a series of radial com-
partments by fleshy vertical partitions, the mesenteries, which ex-
tend inward from the body wall, some reaching the esophagus and
being attached to it, others not extending so far inward as the
esophagus. Each tentacle communicates with one of these radial
compartments, and is to be regarded as a mere extension of part
of the body cavity.

Alcoholic specimens should be sliced transversely and longi-
tudinally. In a transverse section of the lower part of the body
there will be seen the body wall with a series of partitions ex-
tending inward and ending in a free edge. The section across
the upper part of the body shows an outer circle, the body wall,
an inner circle, the stomach wall, and, connecting the two, the
radially arranged partitions, or mesenteries. Like the hydroids.
the sea anemone is well provided with thread cells.

Food is taken into the mouth, digested in the stomach, then
passed, mixed with sea water, into the body cavity, through which
it is made to circulate by the contractions of the body walls. The
indigestible portions of the food are expelled from the stomach
through the mouth.

STONY CORALS.

{Coral Proper.)

In a piece of stony coral, or compound skeleton of a colony of
coral polyps {Galaxea is a good form to study), make out the
following points : —

1 . The nature of the material itself ; test by putting a very
small piece into weak acid, or by touching the specimen with a
drop of acid.

2. The cup, or theca, formed by an individual polyp, often
traceable as a long tube. Observe : —

a. The outer wall of the cup.

b. The partitions, or septa, extending inward from the wall of
the cup.

3. Between the cups, the porous limy secretion, which was

Coelenterata. 175

secreted by the common body substance, or cenosarc, connecting
the individual polyps.

Imagine the sea anemone depositing limy matter in the base
of its body wall, forming a cup ; fleshy radial ridges rising from
the floor and wall of the cup between the mesenteries, and a
similar deposit in these ridges ; thus it will be seen how the cup
is formed by the individual polyp. By the continued growth of
the polyp, and the continuation of the limy deposit, the cup be-
comes an elongated tube. By budding are formed the branches
of these tubes, increasing in size and in the number of partitions
as they grow.

4. Between the cups, a porous secretion of the same material
as that in the cups. This is deposited in the common fleshy
base, filling up, in some forms, the spaces between the cups ; and
when one polyp dies, its cup is covered over and buried out of
sight by this secretion of the common base. •

5. Make a drawing of a mass of stony coral, showing the gen-
eral arrangement of the cups, their mode of branching, and the
common secretion between them.

6. Draw a cup as ^een from its free end. Make also a draw-
ing of a cross section of the same cup toward the smaller end.

In the stony corals the mesenteries are always in pairs, and the
fleshy ridges, in which are secreted the septa, arise between
them.

The tentacles are generally in multiples of six, and are not
fringed. It is of this kind of coral that the reefs are formed.

SEA FEATHER, OR SEA FAN.

In a sea feather, e.g., Murkea, note: —

I. An outer barklike layer; with the thumb nail scrape off a
little of this layer and pulverize it between the thumb and
finger ; mix this powder with water and examine under a micro-
scope. A better way to see the spicules is to clean them thor-
oughly by boiHng some of the outer layer in caustic potash. In
this layer are holes from which the polyps protruded. In this

176 Practical Zoology.

form, then, the secretion is wholly in the living matter between
the polyps, the barklike layer being composed of the dried flesh
in which the spicules lie embedded.

Strip off a piece of the barklike layer and note the grooves
on its inner surface. By examining the end of this piece it may
be seen that these grooves are caused by a series of tubes run-
ning lengthwise near the inner surface of this layer. Find
the openings of the tubes where they were broken ; these tubes
connect the polyps of the colony.

2. The central axis of hornlike substance. Test its flexibility
and strength. Observe the grooves on its surface, and the
relation between them and the tubes above noted. This horny
axis is excreted by the walls of these tubes, and is not pene-
trated by living matter like the outer layer. In the precious red
coral the central axis is formed in the same way, but is calcare-
ous instead of horny, and the outer barklike layer has been
removed.

3. Note the mode of branching in a sea fan, comparing the
margin with the central portion to see how the meshes are
formed. "Remove some of the outer layer; and compare with
the sea feather. In this group (including sea feathers, sea fans,
the precious red coral, etc.) each polyp has eight fringed ten-
tacles ; also eight mesenteries, which are never in pairs. An
alcoholic specimen, with the polyps expanded, should, if pos-
sible, be examined.

Topics for Reports. — Coral Islands and their Formation.

CHAPTER XVIII.
ECHINODERMATA.

STUDY OF A LIVE STARFISH.

Students who can visit the coast may make profitable study
of starfishes in their native haunts. At low tide wade along the
shore, lookijig in tide pools, among rocks and seaweeds, under
wharves, etc., for starfishes. Are they found in any special
situation ? Are they more abundant on one kind of surface
than another ? Do they seem to prefer sheltered places ? Has
their color any relation to their surroundings ? Are they found
in strong light, or do they seem to prefer shaded spots ? Do
they move ? If so, at what rate ? Do you find them on the
vertical walls of rock ? Can they climb ? Do they adhere to
the surface ? If so, how strongly ? Try to pull one away from
a smooth surface on which you find it. Are they extended flat,
or more or less curled up ? Are the rays evenly spread out i
Do they change the position of the rays to any extent ? Are
they found singly or in groups ? Do they seem to live in col-
onies ? Do you find them eating ? If so, what do they eat,
and how ? Has the situation where you find them in numbers
any relation to a food supply ? Have they any preference as to
the temperature of the water ? Are they seriously affected by
extreme changes in temperature ? At how great depth are they
found ? Have starfishes any natural enemies ? Have they any
means of defense ? As you reach out to take a starfish, does it
seem to be aware of your presence ? Is it aifected by strong
light ? By your shadow ? By additional heat ? By sound ?
Does it in any way appear to shrink away from you as you take
hold of it ? Has it any means of stinging or irritating your hand ?

Put a live starfish in an aquarium filled with sea water and
watch it. Does it move about ? Does it crawl up the sides ?

177

1 78 Practical Zoology.

How strongly can it hold to the surface it is on ? Watch the
actions of the tube feet through the glass. Will it climb on
a slender support, such as a cane, or large glass tube ? Can
you learn about its food and mode of eating? Try to get
answers to the questions asked above as to the live starfish
at home. Do you find any evidences as to the mode of develop-
ment and growth of starfishes ? Do the adults have any care of
the young? Do starfishes do any good ? Have they economic
importance ? Do they do any harm ? How can their ravages
be checked ?

EXTERNAL FEATURES OF THE STARFISH.

For this work there is needed : —

1. A set of dried specimens, one for each student ; such a set
may be used with successive classes and will last for years if
carefully handled and kept in a dry place.

2. Alcoholic specimens for dissection.

3. It is desirable to have a set of prepared slides, showing
cross sections of a decalcified ray of a young starfish, and a
ground-down section of a calcareous plate, etc.

4. An injected starfish and a number of injected rays.

Dried Specimen.

1. Observe, first, the shape of the body as a whole. The
central portion is the disk, and its radiating extensions are the
arms, or rays. Note that the rays are bilaterally symmetrical.

2. The mouth is at the center of a thin membrane in the
middle of the oral surface ; the opposite surface is called aboral.

3. Cut into one of the rays. Observe that the body cavity is
bounded by a leathery wall, in which are embedded hard plates.
Compare a piece of a ray of an alcoholic specimen with the
dried one.

4. Test the flexibility of the integument of the alcoholic
specimen. By picking with forceps, prove that there is soft
matter, both on the outside and on the inside of the hard plates.

Echinodermata. 179

To show the real nature of the plates and their relation to the
integument, proceed as follows ; —

a. Handle a starfish which has been decalcified, i.e. has had
its calcareous matter removed by very weak (two per cent) nitric
acid, chromic or other acid. Observe that the body wall is still
present, but lacks the hard parts.

b. Examine a microscopic section of a decalcified ray of a
young starfish ; in such section it should be more clearly seen
that the calcareous plates are wholly within the integument.

c. To show still further the relation between the plates and
the integument, prepare a thin section of a calcareous plate, as
follows : select some pieces of a starfish (left from previous dis-
section) ; boil a few of the larger plates in caustic potash in
order to remove all the organic matter ; wash, and when thor-
oughly dry, smooth down one side on a fine file ; polish on a
perfectly clean oilstone ; cement the surface of the plate to a
glass slide by means of a drop of Canada balsam which has been
boiled on the slide, until, on becoming cold, it is with difficulty
indented by the thumb nail. Proceed then to plane off, by
means of a file, and when quite thin, scrape carefully with a
sharp knife, finally smoothing it on an oilstone. The speci-
men should be examined from time to time under the micro-
scope, in order to ascertain when the proper degree of thinness
has been reached. Dissolve the balsam by means of turpentine,
or better, if properly managed, melt the balsam over a lamp,
and carefully push the section into a watch crystal containing
turpentine; when thoroughly freed from balsam, carefully brush
it with a camel's-hair brush, and mount in Canada balsam in
the ordinary manner.

5. Observe the arrangement of the plates and spines in dif-
ferent regions of the . body wall. Along the middle of the oral
surface of each ray may be seen the shriveled remains of the
tube feet, or ambulacra. The region in which they lie is the
ambulacral area. The plates along this tract are the ambulacral
plates. One row of plates on each side of these ambulacral

i8o Practical Zoology.

plates are known as the interambulacral plates. Examine these
closely for comparison with the sea urchin.

6. The wartlike elevation on the aboral surface is the madre-
poric body. Note that it is situated opposite one of the inter-
radial angles. Examine it with a lens.

7. Make drawings of the oral and aboral surfaces of the
starfish.

Alcoholic Specimen.

1. Briefly review the points noticed in examining the dried
specimen. Bend the rays ; their flexibility is now much less than
in life.

2. Compare the spines of different areas as to their shape, size,
and degree of mobility.

3. Between the spines are soft, tapering projections, the
aboral tentacles.

4. Observe a circle of projections surrounding the spines ;
delicately pinch them with the forceps to determine their con-
sistence ; remove some of these bodies to strong alcohol ; mount
temporarily in turpentine on a slide, cover, and examine with
a low power. There should be distinguished a short stalk bearing
a pair of pinchers ; these bodies are the pedicellariae. In the live
starfish these pinchers may be seen continually snapping; they
are supposed to serve in removing foreign matter from the
body.

5. The soft, cyUndrical projections along the median tract of the
oral surface of each ray are the ambulacra or tube feet. Remove
one of them and examine it with care. Note the arrangement of
the series.

6. Press apart the tube feet and find running along the median
line of the ambulacral groove, a yellowish or whitish ridge, the
nerve of the ray. Trace it to the soft membrane bordering the
mouth, the peristome, and find the nerve ring around the mouth.

7. Trace the nerves also to their outer ends and find a reddish
or yellowish elevation, the eye-spot, borne at the base of a median
terminal tentacle, resembling a tube foot.

Echinodermata. 1 8 i

8. The eye-spot is borne on a distinct, but minute, plate.
Compare young and old specimens to see that whatever the size,
this single ocular plate with its eye-spot is always at the end of
the ray. Count the ambulacral plates in a short and in a long
ray. Where do the new plates develop?

DISSECTION OF THE STARFISH (IN WATER).

1. The ray opposite the madreporic body is the anterior ray.
Cut into its aboral wall near the outer end, and from this point
cut along the upper part of each side of the ray, an inch or two
toward the disk; raise the flap thus freed, and, avoiding internal
organs, continue the cut on each side to the disk.

2. Attached to the aboral wall find a pair of elongated, branched
bodies, the digestive glands, or ceca. Note how each cecum is
held in place by the thin mesentery.

3. Along the middle line of the aboral wall, inside, is a
yellowish streak, the extensor muscle of the ray ; with forceps
prove its general structure.

4. Along each side of the ridge in the floor of the ray, observe
rows of thin-walled sacs, sometimes distended, but more often
collapsed in alcoholic specimens. These are the ampullae, or
ambulacral vesicles. Watch the ampullae while pressing on the
tube feet, and vice versa. If a specimen injected with coloring
matter be at hand, it should now be examined.

5. Near the base of the ray find, on each side, an elongated
body resembling a bunch of grapes, and of a lighter color than the
ceca; these are the ovaries and spermaries, and are very much
alike in appearance in the two sexes, and only distinguishable by
color (the spermaries being hghter colored), or by microscopic
examination in the living specimens. Find the point of attach-
ment of one of them. The openings in the interradial angle are
not very evident.

6. Cut along the sides of the two rays lying on the right and
left of the anterior ray, connect the cuts at the interradial angles,
and turn back the cover of the three rays and disk. Within the

1 82 Practical Zoology.

disk is the large, thin-walled stomach. Examine this organ care-
fully. Pass a blunt probe into the mouth and explore its interior.

7. Observe the large lobes of the stomach extending a short
distance into the rays ; lift one of these lobes and trace the thin
retractor muscles of the stomach to the sides of the ridge in the ray.

In the live starfish the stomach is often found protruded and
surrounding a mussel or an oyster ; after digesting and absorbing
its soft parts the stomach is retracted.

8. Turning to the ceca of the anterior ray, trace them toward
the stomach ; find the union of their tubes and the entrance of
their common duct into the stomach. Observe the place where
this tube enters the stomach, in reference to the corresponding
lobe of the latter.

Carefully cut the mesentery along the aboral wall and wholly
free the ceca of this ray from all attachment above. Note that
the mesentery is double.

9. Hold the starfish inverted and pour water through the mouth
into the stomach to show its shape.

10. In the other two rays which have been opened, cut
across the common ducts of the ceca close to the stomach, and
leave them attached to the aboral walls.

1 1 . Find the extremely short intestine connecting the stomach
with the upper wall of the disk, near the junction of the extensor
muscles of the rays. Find, also, some small branched append-
ages of the intestine. The anal opening is minute.

12. Sever the intestine close to the aboral wall, cut across
the disk close to the madreporic body, and remove entirely the
roof of the disk and the three rays.

Make a drawing of the organs now exposed, showing the
ceca in one ray, the reproductive bodies in another, and the
ampullae in the third.

13. Thoroughly examine the stomach, and remove it after
cutting across the short esophagus.

14. The S-shaped stone canal may now be seen passing down
ward from beneath the madreporic body.

Echinodermata. 183

15. Traced to its lower end, the stone canal may be found
to enter a membranous hollow ring, whose outer border rests
against the inner surface of the hard parts surrounding the
mouth ; this tube is the circumoral water ring. Connected with
its inner surface, find several pairs of pouches, which in the
contracted state are mere buttonlike projections. How many
of these are there, and are they all in pairs ?

Observe also the pouches, like ampullae, connected with the
upper part of the hard ring around the mouth. Press on the
water ring at the level of the peristome, and watch the effect of
this action on these last-named pouches or vesicles. Is there
any connection between them and the water ring?

16. Inclosing the stone canal is a thin membrane, the peri-
cardium. Carefully tear it away. Alongside the stone canal is
a soft tube, sometimes called the " heart," but whose function is
doubtful.

17. Cut across the middle of a ray in two places, about an
inch apart, and make a careful study of the part included
between the cuts. Remove the hepatic ceca, observing again how
they are suspended by the mesenteries. Cut into the aboral
wall in the middle line and spread open the ring. Observe the
depressions in its inner surface ; in the bottoms of these de-
pressions find small holes. What is the relation between these
holes and the nearest structures seen on the outside ?

18. Slowly peel away the thin membrane which lines the
interior of the ray, noting especially the connection between
this membrane and the depressions above noticed. Also watch
closely the aboral tentacles while tearing away this lining mem-
brane.

19. Turn now to the outside of the ray and gently scrape
the surface. A thin layer here may also be easily removed.
Thoroughly clean a small area, noting that the aboral tentacles
come away with this layer.

There will now remain a tough white layer in which are
embedded the calcareous plates which constitute the skeleton.

184 Practical Zoology.

Bend this membrane to see the relations of the calcareous
plates to the membrane and to each other.

20. By picking with the forceps prove that the membrane is
continuous over both the inner and outer surfaces of the plates,
as well as between them. This is an important point, as the
calcareous plates are developed in and by the membrane.

Part of the membrane, if not all, has the power of contract-
ing, by means of which motion is effected. Note the perfora-
tions in the membrane in its thinner portions between the plates
where the aboral tentacles passed out.

21. Reviewing what was noticed in the examination of the
inner and outer membranes, it will be evident that the aboral
tentacles are tubular extensions of the body formed by the pro-
trusion of the inner membrane through the middle membrane, these
tubes being covered by the outer membrane.

22. Turn now to the tube feet and their ampullae and make
out their relations to each other and to the adjacent parts of the
skeleton. The calcareous plates which form the sides of the
ambulacral groove are the ambulacral plates.

23. Pick away a few of the ampullae and then the cor-
responding tube feet, comparing the arrangement of the two.
In this way clean the ambulacral plates and examine them
carefully.

24. Alternately press the ambulacral plates of the two sides
together and separate them to see the range of motion allowed
by the joint. Observe the muscles connecting the ambulacral
plates of the opposite sides, just inside of the nerve.

25. In the angle formed by the ambulacral plates, find the
cut-off end of the water tube of the ray. Insert in the end of
this the point of a drawn-out glass tube, and inflate. When the
ampullae are distended, press on them with the finger and note
the effect on the tube feet ; with a lens examine the distended
ampullae. In fresh specimens the ampullae may be injected
with a colored liquid or with gelatine to be kept as permanent
preparations. In such preparations and in a microscopic section

Echinodermata. 185

of a properly prepared ray, it may be seen that the water tube of
the ray sends off side branches to the tube feet, and also that the
cavities of the tube feet and ampullae are continuous. By the
contraction of the ampullae the tube feet are extended, and by
the muscles in their walls they are moved from side to side and
applied to the surfaces on which the starfish rests. The end is
fixed by means of the suckerlike disk at the tip of the foot to
some foreign object ; then, by the contraction of the tube feet,
the starfish pulls its body along.

The water finds its way through the madreporic body into the
stone canal, thence to the water ring around the mouth, and from
this to the radial canals. The water thus taken in probably
serves for respiration as well as for locomotion.

26. Make a drawing of a cross section of a ray, showing as
many as possible of the above-noted points of structure. A slide
with a series of very small starfishes shows well how the rays are
formed as outgrowths of the disk.

Read Seaside Studies in Natural History^ Agassiz.

Topics for Reports. — Starfishes and the Oyster Industry.

THE SEA URCHIN.
Study of a Live Sea Urchin.

At low tide search the tide pools for sea urchins. For collec-
tion and study, follow the directions given for the study of the
live starfish. Keep sea urchins in a salt-water aquarium and
study their habits. Turn a sea urchin upside down in the aqua-
rium. Can it turn back? How does it accomplish this, and how
long does it take to right itself ?

The requisites for this work are, cleaned skeletons, or tests,
alcoholic specimens, microscopic sections, etc., as in the case of
the starfish.

The Cleaned Test.

I. Observe the radial distribution of the parts around an axis,
at one pole of which, the oral pole, is a large opening. At the

i86 Practical Zoology.

opposite pole, the aboral pole, is a circular area composed of
several small plates, near the center of which is the anal opening.

2. Note that the test is composed of distinct pieces or plates.
Put one of the plates into a little dilute acid and note what
occurs.

3. To make out the real nature of the skeleton, proceed thus : —

a. Handle an entire decalcified specimen, i.e. one from
which the calcareous matter has been removed by chromic or
other acid. Observe that the body walls and spines are still
present.

b. Examine a microscopic section of the decalcified body wall
to see that there was soft living matter, both on the outside and
on the inside of the calcareous plates.

c. Grind down and mount a thin section of a plate, as in the
case of the starfish, and see that not only is the plate wholly
inclosed in the body wall, but that it forms a network whose
meshes were penetrated by the soft living substance of that body
wall. It should now be clear that the plates were formed by the
deposition of calcareous matter within the living tissues of the
body wall. The joints, or sutures, between the plates are formed
by the absence of the deposit of calcareous matter.

4. Returning to the entire test, study the arrangement of the
plates, their variations in shape, size, etc. Into how many simi-
lar areas may the surface of the test be divided ? To make out
these points, and the shapes of the plates, pull apart a piece of
a dried test that was left over from previous dissection.

5. At the aboral pole, observe a small, distinctly marked-off
area, including numerous small plates. This is the anal area,
and the plates are the anal plates. Unlike the other plates,
these, in the living sea urchin, are movable. They surround
the anus.

6. Surrounding the anal area are the five large genital plates,
each having a genital opening near its outer angle.

7. With a lens examine the largest of the genital plates; its
perforated portion serves as a madreporic body.

Echinodermata. 1 87

8. Radiating from the apex of each genital plate is the zig-
zag interradial suture. How many kinds of plates are found
within the area included by two adjacent interradial sutures ?
The perforated plates are the ambulacral plates, and the unper-
forated, the interambulacral plates. Compare these two sets of
plates with the corresponding parts of a starfish.

9. The ambulacral plates form the ambulacral areas. Trace
each of the ambulacral areas to its aboral end, and find at its
apex a small plate wedged in between two adjacent genital plates.
These smaller ones are the ocular plates. Note the small open-
ing from which projects an unpaired tentacle, the end of the
radial water tube.

10. Carefully compare the hard parts of the starfish and sea
urchin. Wherein are they alike, and wherein do they differ ?
What changes in growth would be necessary to convert one of
these forms into the other ? What part of a starfish is homolo-
gous with the anal area of a sea urchin ?

1 1 . Make careful drawings of the oral surface, of the aboral
surface, and of the side of the test.

Alcoholic Specimen.

For the sake of review and comparison, it is well to have the
cleaned test before you during this study.

1. Observe the soft membrane, the peristome, on the oral
surface and the teeth projecting from the mouth.

2. At the aboral pole look for the anus and genital plates.

3. Examine one of the largest spines ; move it about to see
its range of motion. Remove it and make out how it is articu-
lated to the test. The fleshy tube ensheathing the base is
muscular tissue, by the shortening of which the spine is moved.
Clean the spine and make a drawing of it.

4. Note any variations in the size and shape of the spines in
various regions.

5. Study carefully the arrangement of the spines, using the
cleaned test for comparison.

1 88 Practical Zoology.

6. Between the spihes in certain areas find soft tubular pro-
jections, the tube feet, or ambulacra. In life they may be
extended a considerable distance beyond the spines, being used
for locomotion, as in the starfish ; carefully examine the tips of
the tube feet to find what is therein contained.

7. Find also among the spines and on the peristome, slender,
flexible stalks, bearing three-pronged pinchers. In life these
pinchers keep opening and shutting.

8. Pick away the spines and other projections preparatory to
dissection.

Dissection of the Sea Urchin.

After removing the spines, cut, or better, saw with the blade
of a metal saw, through the equator of the test ; place under water
and carefully raise the aboral portion at one side.

1. Press on the tips of the teeth to show their connection with
the complicated apparatus known as the lantern ; now open the
test till the two halves are side by side and complete the dissec-
tion under water.

2. Arising from the middle of the inner surface of the lantern
find the brown esophagus. Trace this as it passes in festoons
about the body walls, widening to become the stomach. Trace
the intestine to the anus, describing carefully its course.

3. Pick away the digestive tube from the oral half of the test.
Note the five double rows of ampullae; between each of these
double rows runs the radial water tube, and between the water
tube and the test is the radial nerve.

4. In the aboral half, note the ovaries and spermaries in the
loops of the intestine. Trace their ducts to the genital pores.

5. After cleaning away the intestine, ovaries, and spermaries,
trace the ampullae as they converge to the ocular plate. Compare
the inside and outside of the test to see if the ampullae are
really opposite the ambulacral pores noticed in the dry test.

6. Study the lantern, make out how it is supported, and how
its various parts are moved, and how they are used.

Echinodermata. 189

Place in water the pieces of test left after dissection and
macerate till the spines are readily detached. Then clean and
keep them for the next class. They will be useful for pulling to
pieces to make out the structure of the test.

Topics for Reports. — Boring Sea Urchms

CHAPTER XIX.
TROCHELMINTHES.

THE WHEEL ANIMALCULE (ROTIFER).

Rotifers are often found in the water of an aquarium where
clams and crayfish have been kept ; pick out clusters of plant
growth, found in the rubbish and sediment in the aquarium, or
on the shells of clams ; with a lens look at the walls of the
aquarium for small, white, wormlike forms.

The body of the wheel animalcule is tapering, ending in a two-
forked foot. At the larger end, when expanded, are two circular
disks, fringed with cilia ; the disks are retractile, as in Vorticella.
Between the disks is the mouth ; this opens into the pharynx,
lined with teeth ; back of the pharynx are the stomach and
intestine.

Rotifers are classed with the worms ; though small, the pres-
ence of a distinct digestive tube, a distinct nervous system, and
organs of sight and hearing, show the Rotifer to be much more
highly developed than the protozoans.

Rotifers have been dried and kept for years, and yet when put
into water they revived.

Study carefully : —

1. The mode of locomotion.

2. The action of the disks and cilia.

3. The motions of the pharynx.

4. The contraction and expansion of the body as a whole.
Make drawings showing the body both in the expanded and in

the contracted state.

Read the " General Characters of Rotifers " in Packard's

Zoology; "Rotifera" in Claus and Sedgwick's Text-book

of Zoology; '* Trochelminthes " in Parker and Haswell's Text-

book of Zoology,

190

INDEX.

Abdomen ot crayfish, 36.

Of grasshopper, 12.

Of rabbit, 127.

Of spider, 31.
Abdominal cavity of rabbit, 129.
Aboral pole of sea urchin, 186.

Surface of starfish, 178.
Achilles' tendon, 90.
Adam's apple, 156.
Adductor muscles of clam, 58.
Air bladder of fish, 74, 76.

Chambers of sow bug, 45.

Sacs of grasshopper, 13, 14.

Sacs of pigeon, 116.

Sacs of snake, 98.

Space in egg, 121.

Tubes of grasshopper, 13.
Ambulacra of sea urchin, 188.

Of starfish, 179, 180,
Ambulacral plates of sea urchin, 187.

Of starfish, 179.

Vesicles of starfish, 181.
Amoeba, 163.

Division of, 164.

Movements of, 163.
Amphibia, 82.
Ampullae of starfish, 181.
Anal plates of sea urchin, 186.
Animalcule, bell, 166.

Slipper, 164.

Wheel, 190.
Annulata, 47.
Anosia, 19.
Antennae of crayfish, 40.

Of grasshopper, 10.
Antennules of crayfish, 40.
Anteorbital bone of fish, 72.
Anterior end of earthworm, 50.

Of fish, 69.
Ant-lion, 28.
Ants, 25.
Anus of frog, 86.

Aorta of fish, 76.

Of frog, 85.

Of mammal, 134, 135, 140.
Aortic arches of earthworm, 51c
Aperture of snail shell, 64,
Apex of heart, 136.
Aquarium, fishes in, 68.
Arachnida, 30.
Arch of aorta, 140.

Neural, of vertebra, 78.

Pectoral, of fish, 77.
Arches, aortic, of earthworm, sic
Arterial bulb offish, 76.
Arteries, cardiac, 139.

Of crayfish, 42.

Of distribution, 140.

Of frog, 85, 88.

Of pigeon, 118.

Of snake, 98.
Artery, carotid, 140.

Iliac, 141.

Mesenteric, 140.

Pulmonary, 135, 136.

Renal, 140.

Subclavian, 140.
Artificial light, in collecting, 4,
Atlas, 161.

Atiditory nerve, 150.
Auricle of clam, 60.

Offish, 76.
Aur-vent valves, 139.
Aves, 104.
Axis, 161.

Balancers of fly, 22.
Ball-and-socket joint, 161,
Barbs of feathers, iii.
Barbules, iii.
Beak of bird, 109.

Of clam shell, 56.
Bee bread, 26.
Qlue, 27.
191

192

Index.

Beeswax, 27.
Beetle, 23.

Bell animalcule, 166.
Bile sac offish, 75.

Of frog, 85.

Of rabbit, 130.

Of snake, 98.

Of turtle, 102.
Bird, beak of, 109.

Ear of, 109.

External features of, 108.

Glottis of, 109.

Head of, 109.

Heel of, 109.

Leg of, 109.

Nostrils of, 109.

Oil gland of, no.

Scutella of, 109.

Skin, preparation of, 113.

Tail of, no.

Tarsus of, 109.

Thumb of, no.

Tongue of, 109.

Trachea of, 109.

Windpipe of, 109.

Wing of, no.
Birds, 104.
Bladder, urinary, of fish, 76.

Urinary, of frog, 87.
Blood tube of earthworm, 51, 52.
Board, spreading, 6.
Body cavity of earthworm, 51.

Cavity of fish, 74.

Cavity of rabbit, 129.

Of clam, 58.

Of hydra, 171.
Bones, anteorbital, 72.

Carpal, 161.

Collar, 161.

Dentary, 71.

Hip, 162.

Hyoid, 157.

Innominate, 162.

Metacarpal, 162.

Metatarsal, 162.

Premaxillary, 71.

Quadrate, 120.
Bottle, cyanide, i.
Boxes, insect, 3, 6.
Brain of earthworm, 53.

Brain of fish, 79.

Of pigeon, 119.

Of rabbit, 146.
Branchiostegal membrane, 72^

Rays, 72.
Breathing of frog, 83.

Pore of fly, 22.
Breeding cages, 4.
Bristles of earthworm, 49, 50,
Bronchi, 135.
Buds of hydra, 172.
Bugs, 18.
Bulb, spinal, offish, 79.

Of frog, 88.
Bumblebee, 24.
Burrows of earthworm, 47.
Butterflies, preserving, 3.
Butterfly, milkweed, 19.

Monarch, 19.

Cabbage butterfly, 20.
Cages, breeding, 4.
Calf muscle of frog, 90.
Canal, stone, of starfish, 182.
Capillaries of frog, 88.
Carapace of crayfish, 37.

Of turtle, loi.
Carbolic acid, 7.
Card, crayfish, 41.

Grasshopper, 15.
Carpal bones, 161.
Cartilage, 152, 159.

Arytenoid, 157.

Cricoid, 157.

Thyroid, 156.

Of windpipe, 133.
Castings of earthworm, 47.
Ceca of fish, 75.

Of grasshopper, 14.

Of pigeon, 117.

Of starfish, iSi.
Cecum of rabbit, 130.
Cells of honeycomb, 27,

Pigment, 73.
Cenosarc, 175.
Centiped, 32.
Centrum of fish, 78.

Of rabbit, 160.
Cephalothorax of crayfish, 36.

Of spider, 31.

Index.

'9T

Cerebellum of fish, 79.

Of mammal, 148.

Of pigeon, 120.
Cerebral hemisphere of fish, 79.
Cerebrum of fish, 79.

Of frog, 88.

Of mammal, 148.

Of pigeon, 119.
Cervical groove, 37.

Vertebrae, 160.
Chest of rabbit, 127.

Cavity of rabbit, 129.
Chirping of cricket, 17.
Chloroform, i.
Choroid coat, 155,
Cilia of clam, 58.

Of Paramecium, 165.

Of rotifer, 190.

Of sponge, 170.
Ciliary processes, 155,
Circulation in frog's web, 87.
Clam, auricle of, 60.

Body of, 58.

Cilia of, 58.

Development of, 61.

Digestive gland of, 60.

Dissection of, 56,

Foot of, 58.

Fresh-water, 54.

Ganglions of, 61.

Gills of, 58.

Heart of, 59.

Hinge ligament of, 56.

Hinge teeth of, 62.

Kidneys of, 60.

Labial palps of, 58.

Locomotion of, 55.

Mantle of, 57.

Mouth of, 60,

Muscles of, 58, 60.

Nervous system of, 61.

Pericardial cavity of, 59.

Position of, 55.

Protection of, 55,

Senses of, 55.

Siphons of, 55. 58, 59.

Ventricle of, 59.

Water currents of, 55.
Clam shell, 56.

Beak of, 56.

Clam shell, composition of, 63.

Hinge ligament of, 56, 62.

Inside of, 62.

Lime in, 63.

Lines of growth in. 56.

Muscle scars of, 58, 62.

Periostracum of, 58.

Structure of, 63.

Umbo of, 56.
Clavicle of rabbit, 161.
Claws of rabbit, 127.
Clitellum of earthworm, 50.
Cloaca of frog, 86.

Of pigeon, 118.

Of snake, 99.
Coat, choroid, 155.

Mucous, 134.

Muscular, 134.

Sclerotic, 155.
Coelenterata, 171.
Coleoptera, 24.
Collar bone, 161.

Esophageal, 44.
Collecting insects, i, 3.
Color of birds, 107.
Composition of clam shell, 63,
Compound eyes, 10.
Compressed fish, 69.
Conchiolin, 63.
Condyle of pigeon, 120.

Of rabbit, 159.
Conjunctiva, 152.
Contractile vacuole, 163.

Vesicle, 163.
Convolutions of brain, 148.
Coral reef, 175.

Stony, 174.
Cord, spinal, offish, 79.

Spinal, of frog, 89.

Vocal, 157.
Cork, 6.
Cornea of crayfish, 40.

Of ox eye, 153.
Corpuscles of frog, 88.
Coxa of grasshopper, 12.
Cranial nerves, 149.
Crayfish, 33.

Arteries of, 42.

Card, 41.

Chimneys, 33.

\^

194

Index.

Crayfish, colors of, 33.

Dissection of, 42.

Esophagus of, 43.

Gullet of, 43.

Heart of, 42.

Holes of, 33.

Muscles of, 43.

Ovary of, 43.

Spermary of, 43.

Stomach of, 43,
Cricket, 17.
Crop of earthworm, 52.

Of grasshopper, 14.

Of pigeon, 116.
Croppie, 69.
Crustacea, 33, 45.
Crystalline lens, 154.
Ctenoid scale, 73.
Cunner, 69.
Cup of coral, 174.
Cuticle of earthworm, 53.

Of Paramecium, 165.
Cyanide bottle, i.
Cycloid scale, 73.
Cyclops, 46.

Darter, 68.
Decapoda, 46.
Dentary bone, 71.
Dentine, 160.
Depressed fish, 69.
Development, 122.

Of cabbage butterfiy, 20.

Of clam, 61.

Of crayfish, 36.

Of grasshopper, 15.
Dextral shell, 65.
Diaphragm, false, of fish, 74.

Of rabbk, 129.
Digestion in vorticella, 167,
Digestive gland of clam, 60.

Tube of sea urchin, 188.
Diptera, 23.
Disk of rotifer, 190,

Of starfish, 178.

Of vorticella, 166.
Dissection, of brain, 146.

Of clam, 56.

Of crayfish, 42.

Of earthworm, 51.

Dissection, of eye, 153.

Of fish, 73.

Of frog, 84.

Of grasshopper, 13.

Of head of rabbit, 143.

Of heart and lungs, 133.

Of kidney, 142.

Of larynx, 156.

Of pigeon, 115.

Of rabbit, 128.

Of sea urchin, 188.

Of snake, 97.

Of spinal cord, 146.

Of starfish, 181.

Of turtle, loi.
Distribution of arteries, 140.

Of veins, 140.
Division of amoeba, 164.
Dorsal surface of earthworm, 50c

Of fish, 69.
Downy feathers, 112.
Dragon fly, 17.
Duodenum of pigeon, 117.

Of rabbit, 130.
Dura mater, 148.

Ear bone offish, 80.

Drums of grasshopper, 13.

Of bird, 109.

Sac of crayfish, 40.
Earthworm, 47.

Body cavity of, 51.

Brain of, 52.

Bristles of, 49.

Crop of, 52.

Cuticle of, 53.

Dissection of, 51.

Epidermis of, 53.

External features of, 50.

Ganglions of, 52.

Girdle of, 50.

Gizzard of, 52.

Gullet of, 52.

Hearts of, 52,

Hypodermis of, 53.

Intestine of, 51, 52.

Kidneys of, 52.

Locomotion of, 49.

Mouth of, 50.

Muscles of, 53.

Index.

»95

Earthworm, nephridia of, 52.

Nerve cord of, 52.

Nerve ring of, 52.

Ovaries of, 52.

Pharynx of, 52.

Typhlosole of, 53.
Ectosarc, 163, 165, 166.
Egg of cabbage butterfly, 20.

Of crayfish, 36.

Of grasshopper, 14.

Of hen, 120.

Of honeybee, 25.

Shell, 121.
Elytra of beetle, 23.
Embryology, 122.
Endopod, 37, 39.
Endosarc, 163, 165, 1,66.
Enlargement, cervical, 147.

Lumbar, 147.
Entomostraca, 46.
Epidermis of earthworm, 53.

Of fish, 73.
Epiglottis of calf, 156.

Of rabbit, 145.
Epithelium of earthworm, 53.
E^sophageal collar, 44.
Esophagus of crayfish, 43.

Of rabbit, 130.

Of sea urchin, 188.
Eustachian tube of frog, 84.

Of rabbit, 145.
Exopod,37, 39.
Extensor muscle, 151.

Of crayfish, 43.
Eye, compound, 10.

Dissection of, 153.

Muscles of fish, 79.

Muscles of ox, 152.

Offish, 71.

Spot of starfish, 180.

Facets of eyes, 10, 17, 40.
Facial nerves, 150.
False diaphragm, 74.

Gill, 73.
Family, 19,
Feathers, iii.
Feelers of crayfish, 35.

Of grasshopper, 10.
Feeling in amoeba, 164.

Feeling in crayfish, 35.

In Paramecium, 165.

In vorticella, 167.
Femur of grasshopper, 12.

Of pigeon, 120.

Of rabbit, 162.
Fibula, 120, 162.
Field study of insects, 7,
Filaments of gills, 72.
File on cricket's wing, 17.
Fins of fish, 70.

Median, 70.

Paired, 71. '
Fish, air bladder of, 74, 76.

Aorta of, 76.

Arterial bulb of, 76.

Auricle of, 76.

Bile sac of, 78.

Brain of, 79.

Cerebellum of, 79.

Cerebrum of, 79.

Dissection of, 73.

Ear bone of, 80.

External features of, 69.

Eye muscles of, 79.

False diaphragm of, 74.

Feeding, 69.

Fins of, 70.

Food of, 67.

Gills of, 72.

Kidneys of, 76.

Liver of, 74.

Mesentery of, 75.

Muscles of, 78.

Neural spine of, 78.

Olfactory lobes of, 79.

Optic lobes of, 79.

Optic nerves of, 79.

Otolith of, 80.

Ovary of, 75.

Oviduct of, 75.

Pectoral arch of, "jt.

Pelvis of, ^T.

Pharyngeal teeth of, jj.

Scales of, 72.

Senses of, 69.

Skin of, 78.

Sperm ary of, 75.

Spinal bulb of, 79.

Spinal cord of, 79.

196

Index.

Fish, spleen of, 75.

Stomach of, 75.

Tongue of, 71.

Urinary bladder of, 76.

Vagus nerve of, 75.

Venous sinus of, 76.

Ventricle of, 76.

Vertebrae of, 78.
Fission of amoeba, 164.
Flat fish, 69.
Flesh fiy, 22.
Flexor muscles of crayfish, 43.

Of mammal, 151.
Floating offish, 68,
Flying of birds, 104.
Food of birds, 105.

Of fishes, 67.

Vacuoles, 163, 165.
Foot of clam, 58.

Of grasshopper, 12.

Of rotifer, 190.

Of snail, 64.
Frog, 82.

Aorta of, 85.

Arteries of, 85, 88.

Bile sac of, 85.

Breathing of, 83.

Capillaries of, 88.

Circulation in web of, 87.

Cloaca of, 86.

Corpuscles of, 88.

Dissection of, 84.

Eustachian tube of, 84.

External features of, 83.

Gullet of, 84.

Heart of, 85.

Kidneys of, 87.

Liver of, 85.

Lungs of, 86.

Mesentery of, 86.

Nervous systems of, 88.

Olfactory lobe of, 88.

Olfactory nerves of, 88.

Optic lobes of, 88.

Optic nerves of, 88.

Ovaries of, 87.

Oviduct of, 87.

Pancreas of, 86.

Pericardium of, 85.

Skeleton of, 91, 92.

Frog, spermary of, 87.

Spinal bulb of, 88.

Spinal cord of, 89.

Spinal nerves of, 89.

Spleen of, 87.

Swimming of, 83.

Urinary bladder of, 87.

Veins of, 88.
Fur of rabbit, 127.

Ganglions of clam, 61.

Of crayfish, 44.

Of earthworm, 52.

Of grasshopper, 15.

Of spinal nerve, 147.
Gastric ceca of grasshopper, 14.
Genital plates of sea urchin, 186.
Genus, 19, 21.
Germ spot in eggs, 121.
Gill chamber of crayfish, 39,

Clefts, 72.

False, 73.

Filaments, 72.

Openings, 72.

Paddle, 39.

Rakers, 72.

Scoop, 39.
Gills of clam, 58.

Of crayfish, 38.

Of fish, 72.
Girdle of earthworm, 50.
Gizzard of earthworm, 52.

Of pigeon, 117.
Glands, digestive, of clam, 60.

Digestive, of crayfish, 43.

Green, of crayfish, 40, 44.

Lymphatic, 135.

Oil, of pigeon, no.

Salivary, of rabbit, 143.
Glandular stomach of pigeon, 118
Glottis, of bird, 109.

Of frog, 84.

Of rabbit, 145.

Of snake, 98.
Grasshopper, 10.

Card, 15.
Green gland, 40, 44.
Groove, cervical, 37.
Grub, 24,
Gullet of crayfish, 43.

index.

197

Gullet of earthworm, 52.
Of frog, 84.
Of mammal, 133.
Of rabbit, 130.
Of snake, 98.
Of vorticella, 167.

Hairs of rabbit, 127.
Head of bird, 109.

Of rabbit, 143.
Heart of clam, 59.

Of crayfish, 42.

Of earthworm , 52.

Of fish, 74.

Of firog, 85.

Of grasshopper, 14.

Of pigeon, 118.

Of rabbit, 131.

Of snake, 98,

Of turtle, loi.

Structure of, 137.
Heel of bird, 109.

Cord, 90.
Hemal arch of vertebra, 78.

Spine, 78.
Hemiptera, 18.
Hemispheres of brain, of fish, 79.

Of frog, 88.

Of mammal, 148.

Of pigeon, 119.
Hepatic veins, of fish, 74.

Of rabbit, 141.
Hilum of kidney, 142.
Hinge ligament, 56, 62.

Teeth, 62.
Hip bone, 162.
Hive of bees, 25.
Honey, 24, 25.

Bee, development of, 25.

Comb, 25, 27.
House fly, 21.
Humerus of pigeon, 120.

Of rabbit, 161,
Humor, aqueous, 154. "

Vitreous, 155.
Hydra, 171.
Hymenoptera, 25.
Hyoid bone, 157.
Hypodermis of earthworm, 53.
Hypoglossal nerves, 150.

Ichneumon fly, 21.
Incisors of rabbit, 159.
Innominate bone, 162.
Insect net, 2.

Pins, 5.
Insecta, 10, 29.
Insects, collecting, i.

Field study of, 7.

Relaxing, 7.

Review of, 28.

Spreading, 6.
Insertion of muscle, 90.
Interambulacral plates, 180.
Intestine of crayfish, 43.

Of earthworm, 51, 52.

Offish, 75.

Of grasshopper, 14.

Of rabbit, 130.

Of sea urchin, 188.

Of snake, 99.
Iris, 154.
Isthmus of fish, 72.

Jaw feet of crayfish, 39.
Joints, ball-and-socket, 161.

Kidneys, dissection of, 142.

Of clam, 60.

Of crayfish, 44.

Of earthworm, 52.

Of fish, 76.

Of firog, 87.

Of pigeon, 118.

Of rabbit, 131.

Of snake, 99.

Structure of, 142.
Killing bottle, i.
Kneepan, 162.

Labeling insects, 6.
Labium of grasshopper, 10.
Labrum of grasshopper, lo.
Lantern, collecting insects by, 4.

Of sea urchin, 188.
Larva of honey bee, 26.
Larynx, 133.
Lateral line, 73.
Left-hand shell, 65.
Leg of bird, 109.

Of grasshopper, 12.

198

Index.

Leg of rabbit, 150.
Lens capsule, 154.

Crystalline, 154.
Lepidoptera, 19.
Ligament, 151, 159.
Lime in clam shell, 63.
Lines of growth, 56.
Lip, of snail shell, 64.

Upper, of earthworm, 50.
Liver of fish, 74.

Of frog, 85.

Of pigeon, 117.

Of rabbit, 129, 130.

Of snake, 98.

Of turtle, 102.
Lobes, olfactory, offish, 79.

Optic, of frog, 88.
Locomotion of amoeba, 163.

Of clam, 55.

Of earthworm, 49.

Of Paramecium, 165.
Lung sacs of spider, 31.
Lungs, dissection of, 133.

Of frog, 86.

Of pigeon, 118.

Of rabbit, 131,

Of snake, 98.

Of turtle, 102.
Lymphatic glands, 135.
Lymph hearts, 83.

Macronucleus, 165.
Madreporic body, 180, 186.
Maggot, 22.
Mammalia, 123.
Mandibles of crayfish, 40.

Of grasshopper, 10.
Mantle of clam, 57.
Maxilla of cra)rfish, 39.

Of grasshopper, 11.

Of spider, 31.
Maxillary bone, 71.
Maxilliped of crayfish, 39.
Median fins, 70.
Mediastinum, 132.
Membrane, mucous, 134, 156.
Mesentery of sea anemone, 174.

Of fish, 75.

Of pigeon, 117.

Of rabbit. lao.

Mesentery of starfish, 181.
Mesothorax of grasshopper, 11.
Metacarpal bones, 162.
Metastoma, 40.
Metatarsal bones, 162.
Metathorax of grasshopper, il.
Micronucleus, 165.
Migration of birds, 106.
Milkweed butterfly, 19.
Milliped, 32.
Minnow, 68.
Molars of rabbit, 160.
Mollusca, 54.
Molting of birds, 106.

Of crayfish, 36.
Monarch butterfly, 19.
Mounting insects, 5.
Mouth of clam, 60.

Of crayfish, 39.

Of earthworm, 50.

Of hydra, 171.

Of Paramecium, 165.

Of sea urchin, 187.

Of snail, 64.
Movements of amoeba, 163.

Of vorticella, 167.
Mucous membrane, 156.
Muricea, 175.
Muscle, digastric, 144.

Extensor, 151.

Flexor, 151.

Insertion of, 90.

Masseter, 143.

Of frog, action of, 90.

Of starfish, 181.

Origin of, 90, 151.,

Papillary, 138.

Pectoralis, 117.

Scars of clam shell, 58, 62.

Sheath, 91, 151.

Striated, 91, 152.

Striped, 91, 152.

Subclavian, 117.

Temporal, 144.
Muscles, abdominal, of pigeon, II9.

Extensor, of crayfish, 43.

Flexor, of crayfish, 43.

Of clam, 58, 60.

Of crayfish, 43.

Of earthworm, 53.

Index.

199

Muscles of eyeball, 152.

Of fish, 78.

Of fish eye, 79.

Of grasshopper, 14.

Of larynx, 157, 158.

Of pigeon, 116.

Of starfish, 182.
Myriapoda, 30, 31, 32.

Nectar, 24.

Nephridia, 52.

Nerve collar, 52.

Nerve cord of crayfish, 44.

Of earthworm, 52.

Of grasshopper, 15.

Of starfish, 180. .
Nerve, optic, 153.

Ring, of earthworm, 52.

Ring, of starfish, 180.

Sciatic, of frog, 89.

Vagus, offish, 75.

Vagus, of pigeon, 116.
Nerve-muscle preparation, 90.
Nerves, auditory, 150.

Cranial, 149.

Facial, 150.

Hypoglossal, 150.

Of crayfish, 44.

Olfactory, of frog, 88.

Optic, of fish, 79.

Optic, of frog, 88.

Spinal, of firog, 89.

Spinal, of rabbit, 147.
Nervous system of clam, 61.

Of fi-og, 88.

Of grasshopper, 15.

Of rabbit, 146.
Nesting of birds, 105.
Net, insect, 2.
Neural arch, 78.

Spine, 78.
Nostrils of birds, 109.

Of fish, 72.
Nucleus, 163.
Nymph, 18.
Nymphalidae, 19.

Observation hive, 25.
Ocelli, 10.
Ocular plates, 187.

Odonata, 18.
Odontoid process, 161.
Oil gland of birds, no.
Olfactory lobes of fish, 79.

Nerve of frog, 88.

Nerve of mammal, 148, 149.
Olfactory nerve of frog, 88.
Opercle of fish, 72.
Operculum of snail, 65.
Optic lobes of fish, 79.

Of frog, 88.

Nerve of fish, 79.

Nerve of frog, 88.

Nerve of mammal, 149, 153.
Oral groove of Paramecium, 165.

Pole of sea urchin, 185.

Surface of sea urchin, 187.

Surface of starfish, 178.
Orbit of eye, 159.
Order, 19.

Origin of muscle, 90, 151-
Orthoptera, 17.
OtoHth, 80.
Ovary of crayfish, 43.

Of earthworm, 52.

Of fish, 75.

Of frog, 87.

Of hydra, 173.

Of pigeon, 119.

Of sea urchin, 188.

Of snake, 99.

Of starfish, 181.

Of turtle, 102,
Oviduct of crayfish, 43.

Of earthworm, 50.

Of fish, 75.

Of frog. 87.

Of grasshopper, 14.

Of pigeon, 119.

Of snake, 99.
Oviparous animals, 122.
Ovipositor of cricket, 17-

Of dragon fly, 18.

Of grasshopper, 13.
Ovoviviparous animals, 138-

Paired fins, 71.
Palate of rabbit, 144.
Palatine bones, 71.
Palps of butterfly, 19.

200

Index.

Palps of clam, 58.

Of crayfish, 40.

Of grasshopper, 11.

Of spider, 31.
Pancreas of frog, 86.

Of pigeon, 117.

Of snake, 99.
Papillae of rabbit's tongue, 144.
Paramecium, 164.
Parasites, 21.

Partitions of earthworm, 51.
Patella, 162.
Pectoral arch, 77.

Fin, 71.

Muscle, 116.
Pedicellariae of starfish, 180.
Pelvis of fish, 'jj.

Of rabbit, 162.

Of turtle, loi.
Perch, 69.

Sea, 69.
Perching of birds, 119.
Pericardial cavity of clam, 59.

Fluid, 135.
Pericardium of frog, 85.

Of mammal, 135.

Of pigeon, 118.

Of snake, 98.
Periosteum, 152.
Periostracum of clam shell, 58.
Peristome of sea urchin, 187.

Of starfish, 180.

Of vorticella, 166.
Peritoneum of fish, 74, 76.

Of rabbit, 129.
Phalanges, 162.
Pharyngeal teeth of fish, 77.
Pharynx of earthw^orm, 52.

Of rabbit, 142.

Of rotifer, 190.
Pia mater, 148, 149.
Pieridae, 21,
Pigeon, air sacs of, 116.

Arteries of, 118.

Brain of, 119.

Ceca of, 117.

Cerebellum of, 120.

Cerebrum of, 119.

Cloaca of, 118.

Crop of, 116.

Pigeon, dissection of, 115

Duodenum of, 117

Gizzard of, 117.

Heart of, 118.

Kidneys of, 118.

Liver of, 117.

Lungs of, 118.

Mesentery of, 117.

Muscles of, 117.

Ovary of, 119.

Oviduct of, 119.

Pancreas of, 117.

Pericardium of, ii8.

Skeleton of, 120.

Spermaries of, 119.

Spinal cord of, 120.

Trachea of, 116.
Pigment cells of fish, 73.
Pinchers of crayfish, 44.
Pin feathers, 112.
Pinning insects, 5.
Pins for insects, 5.
Pisces, 66.
Plaster of Paris, i.
Plastron of turtle, loi.
Plates, ambulacral, 187.

Anal, of sea urchin, 186.

Epidermal, of turtle, loi.

Genital, of sea urchin, i86»
Pleura, 134.
Pleurum of crayfish, 37.

Of grasshopper, 13.
Plexus, brachial, 147.
Poison, I.

Poison gland of bee, 25.
Pollen, 24.
Pond snail, 64.
Pore, breathing, of fly, 22.
Porifera, 168.
Position of clam, 55.
Posterior end of earthworm, 50.

Of fish, 69.
Premaxillary bone of fish, 71.
Preservation of insects, 5.
Primaries, no.
Proboscis of bee, 24.
Processes of vertebrae, 161.
Propolis, 27.

Prostomium of earthworm, 50.
Protection of clam, 55.

Index.

20 1

Prothorax of grasshopper, 11.
Protoplasm, 163.
Protopod of crayfish, 37, 39.
Protozoa, 163.
Pseudopod, 164.
Pulsating vacuoles, 165.
Puparium of fly, 22.
Pupil, 154.
Pyramid, urinary, 143.

Quadrate bone, 120.
Quill feathers, iii.

Rabbit, 123.

Abdomen of, 127.

Abdominal cavity of, 129.

Bile sac of, 130.

Body cavity of, 129.

Brain of, 146.

Cecum of, 130.

Chest of, 127.

Chest cavity of, 129.

D'aphragm of, 129.

Dissection of, 128.

Duodenum of, 130.

Epiglottis of, 145.

Fur of, 127.

Glottis of, 145.

Gullet of, 130.

Heart of, 131.

Intestine of, 130.

Kidneys of, 131.

Legs of, 150.

Liver of, 130.

Lungs of, 131.

Mesentery of, 130.

Peritoneum of, 129.

Pharynx of, 144.

Rectum of, 131.

Skeleton of, 158.

Spinal cord of, 146, 147.

Spleen of, 130.

Stomach of, 129.

Thoracic cavity of, 129,

Thorax of, 127.

Villi of, 131.
Radius of pigeon, 120.

Of rabbit, 161.
Rays, 70,

Of starfish, 178.

Rectum of rabbit, 131.

Red coral, 176.

Reflex action of spinal cord, 89.

Relaxing insects, 7.

Reproduction of amoeba, 164.

Of Paramecium, 166,

Of vorticella, 167.
Reptilia, 95.
Retina, 155.
Right-hand shell, 65.
Roots of nerves, 147.
Rostrum of crayfish, 37.
Rotifer, 190.

Salivary gland, 143.
Scales, 19.

Ctenoid, 73.

Cycloid, 73.

Of butterfly, 19.

Of fish, 73.

Of snake, 96.

Of turtle, loi.
Scapula, 161.
Sciatic nerve of frog, 89, 90.

Of rabbit, 148, 151.
Sclerotic coat of eye, 155.
Scutella of birds, 109.
Sea anemone, 173.

Fan, 175.

Feather, 175.

Perch, 69.

Urchin, 185, 188.
Secondaries, no.
Segments of earthworm, 50.
Senses of clam, 55.

Of crayfish, 35.

Of fishes, 69.
Septa of coral, 175.
Shaft of feather, ni.
Sheath of muscle, 91.
Shell bag, 3.
Sinistral shell, 65.
Siphons of clam, 55, 58, 59.
Skeleton of crayfish, 40.

Of frog, 91, 92.

Of pigeon, 120.

Of rabbit, 158.

Of sponge, 168.

Of turtle, 102.
Skin of fish, 78.

202

Index.

Slipper animalcule, 164.
Snail p>ond, 64.

Shell, 64.
^nake, 95.

Air sacs of, 98.

Arteries of, 98.

Bile sac of, 98.

Cloaca of, 99.

Dissection of, 97.

External features, 96.

Glottis of, 98.

Gullet of, 98.

Heart of, 98.

Intestine of, 99.

Kidneys of, 99.

Liver of, 99.

Lung of, 98.

Ovary of, 99.

Oviduct of, 99.

Pancreas of, 99.

Pericardium of, 98.

Scales of, 96.

Skin, preparation of, 99.

Spermary of, 99.

Sperm duct, 99.

Spleen of, 99.

Stomach of, 98.

Teeth of, 97.

Tongue of, 97.

Ureters of, 99.

Veins of, 98,

Ventral plates of, 96.
Snout of fish, 70.
Songs of birds, 106.
Sounds made by grasshopper, 12.
Sow bug, 45.
Species, 20, 21.
Sperm duct of snake, 99.

Receptacles of earthworm, 52.

Sacs of earthworm, 51, 52.
Spermaries of crayfish, 43.

Of fish, 75.

Of frog, 87.

Of hydra, 173.

Of pigeon, 119.

Of sea urchin, 188.-

Of snake, 99.

Of starfish, 181.
Spicules of sea fan, 176.

Of sponge, 169.

Spider, 30.

Web, 30.
Spinal bulb of fish, 79.

Of frog, 88.

Of mammal, 148.
Spinal cord of fish, 79.

Of frog, 89.

Of pigeon, 120.

Of rabbit, 146, 147.

Reflex action of, 89.
Spinal nerves of frog, 89.

Of rabbit, 147.
Spines of fish, 70.

Of vertebrae, 78.

Of sea urchin, 187.
Spinnerets of spider, 31.
Spinning of spider, 30.
Spiracles of fly, 22.

Of grasshopper, 11, 13.
Spire of snail shell, 65.
Spleen of fish, 75.

Of frog, 87.

Of rabbit, 130.

Of snake, 99.
Sponge, 168.

Cilia of, 170.

Simple, 169.

Skeleton of, 168.
Spreading board, 6.

Insects, 6.
Squash bug, 18.
Starfish, 177.

Dissection of, 181.

External features, 178.
Sternum of crayfish, 37.

Of grasshopper, 13.
Sting of bee, 25.

Stomach, glandular, of pigeon, 118.
Stomach of clam, 60.

Of crayfish, 43.

Offish, 75.

Of frog, 86.

Of rabbit, 129.

Of sea urchin, 188.

Of snake, 98.

Of starfish, 181.

Of turtle, 102.
Stone canal of starfish, 182.
Stony corals, 174.
Striated muscle, 91.

Index.

203

Stridulation of grasshopper, la.
Striped muscle, 91.
Structure of clam shell, 63.

Of heart, 137.

Of kidney, 142.
Stylets of cricket, 17.
Sugaring, 4.
Sunfish, 69.
Sutures, interradial, of sea urchin, 187.

Of rabbit's skull, 159.

Of snail shell, 64.
Swimmerets of crayfish, 37.
Swimming of crayfish, 34.

Of fish, 68.

Of frog, 83.
Symmetry, bilateral, of earthworm, 50.

Of fish, 69.
Synovia, 151, 159.

Tadpole, 93.
Tail of bird, no.

Fin, of crayfish, 38.
Tarsus of bird, 109.

Of grasshopper, 12.

Of mammal, 162.
Teeth, pharyngeal, of fish, tj.

Of rabbit, 159.

Of sea urchin, 187.

Of snake, 97.
Telson of crayfish, 38.
Tendon, 158.

Achilles, 90.
Tentacles of hydra, 171.

Of snail, 64.

Of starfish, 180.
Tergum of crayfish, 37.
Tertiaries, no.
Test of sea urchin, 185.
Tetradecapoda, 46.
Theca of coral, 174.
Thigh of bird, 109.
Thoracic cavity of rabbit, 129.
Thorax of rabbit, 127.
Thousand legs, 31.
Thread cells of hydra, 172.
Thumb of bird, no.
Tibia of grasshopper, 12.

Of pigeon, 120.

Of rabbit, 162.
Toes of bird, 109.

Tongue of bee, 24.

Of bird, 109.

Of fish, 71.

Of grasshopper, 11.

Of snake, 97.
Trachea of bird, 109, 116.

Of rabbit, 131, 133.

Of snake, 98.
Tracheae of grasshopper, 13.
Transformation of dragon fiy, 18.
Trochanter of grasshopper, 12.
Trochelminthes, 190.
Tube feet of sea urchin, 188.

Of starfish, 179, 180.
Tubercle of rib, 161.
Turtles, 100.

Bile sac of, 102.

Dissection of, loi.

External features of, loi.

Heart of, loi.

Liver of, 102.

Lungs of, 102.

Ovary of, 102.

Pelvis of, loi.

Scales of, loi.

Skeleton of, 102.

Stomach of, 102.

Vertebrae of, 102.
Tympanum of frog, 84.

Of grasshopper, 13.
Typhlosole of earthworm, 53.

Ulna of pigeon , 120.

Of rabbit, 161.
Umbo of clam shell, 56.
Ureter of mammal, 142.

Of snake, 99.
Urinary bladder of frog, 87.

Pyramid, 143.

Vacuole, contractile, 163.

Food, 163.

Pulsating, of Paramecium, 165.

Pulsating, of vorticella, 167.
Vagus nerve of fish, 75.

Of pigeon, 116.
Valves, aur-vent, 139.

Of clam shell, 56.

Mitral, 139.

Semilunar, 138.

204

Index.

Valves, tricuspid, 138.

In veins, 141.

Vent-art, 139.
Vane of feather, iii.
Veins, cardiac, 137.

Caval, 135.

Distribution of, 140.

Of frog, 88.

Gastric, 141.

Hepatic, of fish, 74.

Hepatic, of mammal, 141.

Iliac, 141.

Innominate, 141.

Jugular, of mammal, 141.

Jugular, of pigeon, 116.

Mesenteric, 141.

Pancreatic, 141,

Portal, 141.

Postcaval, 141.

Precaval, 141.

Pulmonary, 136.

Renal, 141.

Of snake, 98.

Splenic, 141.

Subclavian, 141.

Valves in, 141.

Of wings of insect, 12, 14.
Venous sinus of fish, 76.
Vent-art valves, 139.
Ventral plates of snake, 96.
Ventral surface of earthworm, 50.

Offish, 69.

Ventricle of brain, 149.

Of clam, 59.

Of fish, 76.

Of mammal, 135, 138.
Vertebras of fish, 78.

Of pigeon, 120.

Of rabbit, 160.

Of turtle, 102.
Vesicle, contractile, 163.

Ambulacra), 181.
Villi of rabbit, 131.
Viviparous animals, 122.
Vocal cords, 157.
Vomer offish, 71.
Vorticella, 166.

Walking of birds, 104.

Of crayfish, 34.

Of fly, 23.
Wasp, 25.
Water currents of clam, 55.

Glass, 67.

Ring of starfish, 183.

Tubes of starfish, 184.
Wax, bees', 26.
Wheel animalcule, 190.
Whorls of snail shell, 65.
Windpipe of bird, 109.
Wing of bird, no.

Of fly, motion of, 2t.

Of grasshopper, 11.
Winglet of fly, 22.

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