OF THE

UNIVERSITY

OF

EDUCATION EIBH;

63$

ELEMENTARY LESSONS

ZOOLOGY

A GUIDE IN STUDYING ANIMAL LIFE AND

STKUCTUKE IN FIELD AND

LABORATORY

BY

JAMES G. NEEDHAM, M.S.

INSTRUCTOR IN ZOOLOGY, KNOX COLLEGE, GALESBURG, ILL.

<*>:*I<

NEW YORK ... CINCINNATI •-.. CHICAGO

AMERICAN BOOK COMPANY

" The invariable adaptation of an animal to the life it leads is one of
nature's most instructive lessons, and can be discovered and appreciated
by every pupil, but never through oral teaching or from reading of
books. Setter a child should learn to handle one animal, to see and
know its structure and how it lives and moves, than to go through the
whole animal kingdom with the best text-book under the best teacher,
aided by the best charts ever made. The former would have learned
what real knowledge is and how to get it, while the latter would have

simply learned how to pass at his school examination. "

ALPHEUS HYATT.

" Therefore I would, in the name of education, urge students to
begin naturally with what interests them, with the near at hand, with
the practically important. A circuitous course of study, followed with
natural eagerness, will lead to better results than the most logical of
programs, if that take no root in the life of the student."

J. ABTHUR THOMSON, in " The Study of Animal Life," p. 361.

EDUCATION MBB7

COPYRIGHT, 1895, 1896, BY
AMERICAN BOOK COMPANY.

NEED. ZOOLOGY.

E-P 8

PREFACE.

THIS book is intended for that increasing class of moderately
equipped schools in which it is desired to make a beginning in the
study of zoology after the scientific method. Its aim is to put the
student in the way of acquiring for himself a knowledge of animal
life and structure. It is not intended to supersede the teacher, but
rather to relieve him from doing that part of the work for the stu-
dent which the student should do for himself, and to give the teacher
a wider opportunity. It is written in the firm belief that the student
will receive that benefit which belongs peculiarly to this study in just
so far as he comes into touch with nature through actual contact with
facts.

The plan presented has been adopted after due deliberation and
repeated trial. In the belief that the simplest animal structures are
best for illustrating the fundamental ideas of zoology, as well as
being easiest understood, four simple types are introduced first.
These are for microscopic study, from material to be provided by the
teacher, and prepared by him for examination. From the study of
these the student may learn the purport of the terms cell, protoplasm,
tissue, organ, differentiation, sexuality, etc. With these fundamental
ideas mastered, he is prepared to study intelligently any of the higher
animals. The novelty of the introductory microscopic work will be
a sufficient guaranty of interest in it, and the succeeding work is out-
lined in accordance with the tastes and in avoidance of the prejudices
of the beginner. Insects are taken up next in order, and the most
attractive insects are studied first.

This is a deliberate but not a purposeless violation of the logical
order. Systematic zoology may well be neglected, so long as the
student is ignorant of the material to be classified. To start the
beginner where the specialist leaves off is an error too often repeated
in the teaching of this as of other sciences. Wherever, in the
arrangement of the subject-matter of this book, the choice has seemed

M577O41

4 PREFACE.

to lie between being logical and being serviceable, the author has
preferred that the arrangement should be serviceable.

The study of animals alive, and in their biological relations to their
environment, is made a prominent feature. It is not morphology, or
physiology, or natural history alone, that constitutes a proper ele-
mentary zoological course, but a comprehensive study of animals, that
develops these sciences in their proper relations, and gives the ele-
mentary student a general view of the whole field, — a correct
" zoological perspective." Morphology may, perhaps, like chemistry,
be learned in the laboratory alone, but zoology may not. It has been
a popular delusion that a term of dissections constitutes a proper ele-
mentary course. Such a course was an improvement on former
methods : the study of dead animals is infinitely better than no con-
tact with animals at all. But to study animals with nature and life
left out is to omit a phase of the subject of deepest scientific interest,
of highest educational importance, and of greatest pedagogical utility.

This book is written primarily for use in the interior : hence
forms of life obtainable only at the seashore receive less attention
than those found inland. The study of animal life is best begun
with forms nearest at hand. The custom of sending to the seashore
for specimens with which to begin the study, and neglecting a wealth
of material at home, does not deserve to be encouraged. At the sug-
gestion of many teachers who live where fresh marine material is
available, a study of the starfish is inserted as the last chapter in the
book. Believing that it will be used in some cases where material to
illustrate it is insufficient, it contains fewer interrogation points, and
more of explicit statement, than preceding chapters. A few diagrams
of structures are inserted for the same reason.

All the work outlined in the following pages has been tested in the
classroom, and has been repeatedly performed by the author while
drawing up these lessons ; and it is hbped by him that they may prove
reasonably free from ambiguity and error. Xo animal is studied
exhaustively : each one lends itself to some special purposes of illus-
tration, and to such ends only is it used. Care has been taken to
introduce no work beyond the capacity of the beginner. The illustra-
tions given are intended to guide the student in finding and identify-
ing for himself the animals recommended in the text for study. Few
drawings are given of things which the student may reasonably be
expected to draw for himself. If such are wanted, the reference
books recommended are filled with them, and may be consulted with
profit.

In the material presented herein the author can lay no claim to

PREFACE. 5

originality : he only wishes to be given credit for an honest effort at
selecting, from the most available materials offered, that best calcu-
lated for introducing the beginner to the ideas and principles of
zoological science. lie respectfully invites the correspondence of
teachers who find difficulty in using the book.

Finally, the author would gratefully acknowledge the assistance of
many friends and teachers and of books which were teachers. He
would speak of the cut on p. 212, which was kindly loaned by
Professor Forbes of the Illinois State Laboratory of Natural History :
and he would especially remember the assistance of Dr. E. A. An-
drews of Johns Hopkins University, who read the manuscript of the
text; of Professor J. H. Comstock of Cornell University, who read
the proof sheets of the pages relating to insects ; of Professor E. A.
Birge of the University of Wisconsin, who read the proof sheets of
the pages relating to crustaceans, mollusks, and vertebrates ; of Mr.
Edward Potts of Philadelphia, who read the manuscript of the pages
relating to the fresh- water sponge ; of his honored friend and teacher,
Professor Hurd of Knox College, who revised the etymological list of
technical terms; and, last but not least, of his wife, Anna Taylor
Needham, who made pen drawings for most of the illustrations.

J. G. N.

CONTENTS.

PAGE

INTRODUCTION 9

PROTOZOANS 12

The Amoeba 12

The Slipper Animalcule 18

CCELENTERATES , 22

The Fresh-water Sponge 22

The Hydra 26

INSECTS 34

Hexapod Insects 36

The Butterfly 36

The Dragon Fly 42

The Grasshopper 48

The Squash Bug 67

The Two-year Cicada 69

The Back-Swimmer 61

The Bumblebee 63 '

The Mud Wasp 70

The Paper Wasp 72

The Honeybee 73

The Black Blister Beetle 74

The Bluebottle Fly 80

The Bee Killer 84

The Cabbage Butterfly 86

The Life Process in Insects 93

A Review Exercise 99

A Lesson in Classification 101

Arachnid Insects . . , 105

The Spider 105

8 CONTENTS.

PAGE

Myriapod Insects 109

The Chilopod or Centiped 109

CRUSTACEANS Ill

The Crawfish Ill

TheAsellus 125

The Cyclops 126

Further Classification 127

WORMS 130

The Earthworm 130

MOLLUSKS 140

The River Mussel 140

The Pond Snail 154

VERTEBRATES 161

The Catfish 161

The Frog 178

The Turtle 198

The Snake .... 208

The English Sparrow 211

The Rabbit 237

The Life Process in Vertebrates 260

ECHINODERMS 266

The Starfish 266

APPENDIX 275

Prerequisites 275

Reagents 276

Directions for the Preparation of Material for Study .... 278

Accentuated List of Technical Terms 288

Suggestions to the Teacher 302

INDEX . . 305

INTRODUCTION.

The Study of Animal Life is begun when we first learn
the names of our household pets, and begin to note the
differences between them. It is continued so long as our
eyes and ears are open to observe the nature and capacities
of the animals with which our daily life brings us in con-
tact. The horses that draw our carriage, the dogs that
answer our call, the birds that delight our ears with their
songs from the tree tops, the insects that flit before our
eyes among the flowers of the garden, — all are continually
illustrating phases of animal life, some of which cannot
escape the notice of the most casual observer.

Every one knows that animals must have food. When
they are young, they require food for growth ; and when
they are grown, they require food to furnish bodily strength.
They require air also, — fresh air, containing oxygen, for
the oxygen is the essential thing. A bird inclosed in an
air-tight box with plenty of food, or a fish placed in a small
quantity of clean water, soon dies, because the available
supply of oxygen is soon exhausted.

Every one knows that, sooner or later, animals die, and
that they leave descendants to perpetuate their race upon
the earth ; and every one should know that not all their
young come to maturity, and that the number of their prog-
eny is proportioned to the vicissitudes to which their life
is exposed.

Every one knows that animals move, that most of them
move freely from place to place, and that those which are

9

10 INTRODUCTION.

fixed in their location, like the oyster, move freely some
parts of their bodies in obtaining their food.

Every one knows that animals feel, that they respond
to stimuli from without and to impulses from within, and
that the most familiar animals exhibit varying degrees of
instinct and intelligence.

These plain facts are fundamental. All the phenomena
of animal life may be grouped under four heads : —

1. All those processes which are concerned with feeding
and growth, — the taking of food, the preparation of it for
the use of the body, the carrying of it in solution to the
various parts, the building of it into the body structure,
the exposure of it to oxygen derived from the air, and the
removal of useless portions and of Avaste materials from
the body (whether performed by simple means or by com-
plex, whether without organs or by means of many separate
organs), — all may be called phenomena of Nutrition.

2. All the phenomena connected with the reproductive
process may be called phenomena of Reproduction.

3. All the phenomena of free and spontaneous move-
ment may be called phenomena of Voluntary Motion.

4. All the phenomena of the senses of instinct and of
intelligence may be called phenomena of Sensation.

It will then need to be borne in mind that this fourfold
division is made for convenience ; that the four groups of
phenomena are not entirely distinct, but interrelated and
interdependent.

In the beginning we must distinguish between that which
is necessary and that which is only accessory in animal
structure. The robin has a beak for eating, and wings for
getting about ; but beak and wings are not necessary for
animal existence. Eating and moving are necessary, but
these might be effected in other ways. The robin is a bird
because of its beak and wings, an animal only because it
eats and moves at will.

INTRODUCTION. 11

In studying each animal, if we ask, (1) What is its food,
how obtained and how used ? How does it get oxygen from
the air? How does it get rid of waste and worn-out mate-
rial from its body? (2) How does it reproduce its kind?
How numerous are its progeny and to what danger exposed?
(3) How does it move ? What are its specially movable
parts ? (4) What powers of sense, of instinct, and of intel-
ligence has it, and what sort of a nervous system as the
seat of these powers ? — and if we follow patiently where
Nature leads until we have found satisfactory answers to
these questions, — we shall arrive at a better comprehension
of the animal's activities, and in the end shall have learned
many lessons of perennial interest and profit. This four-
fold division of animal phenomena will be of service as an
outline for our future study, leading us to learn for each
animal all we can about

I. Nutrition, and its subservient organs.
II. Reproduction, and the adaptation of the reproduc-
tive process to varying conditions of life.

III. Voluntary Motion and motor organs.

IV. Sensation, as manifest through a nervous system in
senses, instinct, and intelligence.

PROTOZOANS.

THE AMCEBA.

The Amoeba is selected as the first animal for study,
because of its extreme simplicity. In it we are dealing
with animal life at its lowest terms.

It is very small, usually less than a hundredth of an
inch in diameter, and can be studied only with the aid of
a microscope. Examine one that has been taken up in a
drop of water, mounted on a glass slip, covered, and placed
in the field of a microscope.1

First find it. This will be task enough for a moment
for a beginner, even if the amoeba be in the field; for it
presents so little likeness to familiar animals, that it might
as readily be taken to be anything else. It appears like a
little drop of jelly spreading out on a flat surface, trans-
lucent in its central portion, and very transparent around
its border. Reference to the accompanying figure will aid
in recognizing it. That it is alive will not be ascertained
at the first glance, but may be learned from watching its
slowly changing outline for a moment or two. After find-
ing it, and after learning by a few trials how, by moving1
the glass slide, to bring it back into the center of the field
when it moves out, and how to keep it in focus by turning
the adjustment screws on the microscope, then study its
general structure and its movements.

1 If the student be working alone, he will follow the directions given
to the teacher (see Appendix, p. 278) for collecting amcebas, and pre-
paring them for examination.

12

THE AMCEBA.

13

Observe : 1. A granular, translucent central portion (the
endosarc), with something of the appearance of ground
glass.

2. A transparent outer border (the ectosarc), so clear it
is liable to be overlooked the first time an amoeba is seen,
and the endosarc taken for the whole animal.

3. Irregular, blunt projections (pseudopodia, or false
feet), which are slowly pushed out from the body wall, or
drawn into it. Observe that in all of these there is the

AMCEBA (X 500), drawn while moving in the direction of the arrow:
nu, nucleus ; v, vacuole ; ps, pseudopodia.

same clear border and granular central portion ; and this
is true of their appearance when they protrude vertically,
as well as when extended laterally. If we can roll an
amceba over, we shall see the same arrangement of parts ;
so that we must conclude that the ectosarc forms a com-
plete outer layer about the whole animal. .

Pseudopodia. — Watch the formation of pseudopodia.
See first a protrusion of the clear ectosarc, then the flowing
of the more fluid granular endosarc out into it. * Observe

14 PROTOZOANS.

that, while pseudopodia are pushed out in all directions,
they grow principally in one direction, and that the direc-
tion in which the amoeba is traveling. Observe that about
as fast as pseudopodia are formed in one direction, the body
follows them, all its granular content flowing into their
bases, swelling them, and uniting them.

Watch also the withdrawal of pseudopodia, first a flow-
ing toward the center of the granular part, leaving an
emptied projection of ectosarc, which follows on in the rear.

Such is amoeba's primitive method of locomotion. The
pseudopodia which are pushed out on one side hold their
ground ; and, when the semifluid body begins to follow,
they advance, and the whole mass is seen setting forward
in an exceedingly slow, flowing or gliding motion.

If an active amoeba be watched a short time, it may be
seen to change its direction. To do this it does not need
to turn around: it simply puts out pseudopodia in the
new direction, and follows them. It has neither head nor
tail. All parts are alike, and one is as well adapted as
another to go first. It may be seen to avoid large objects
with which it comes in contact in its course. If it meet a
conveniently small object, it may sometimes be seen to
encircle it with pseudopodia, and ingulf it into its soft
body mass, — swallow it, so to speak, — after which the
object may be seen within the granular endosarc, where it
is lodged as food for digestion. If it prove indigestible,
it is gotten rid of in a correspondingly simple way. The
body mass flows away from it, and it is left behind.

If the amoeba be irritated in any way, as by touching
the cover glass, it immediately draws in its pseudopodia,
and assumes a more or less spherical form. If not injured
in any way, it soon resumes activity.

Make a series of half a dozen outlines of an amoeba,
drawn at intervals of a minute or two, or less if it be
moving actively, to show the changes in form.

THE AMCEBA. 15

Minute Structures. — If the currents in an active amoeba
have been watched carefully under high power, certain
minute structures will have been discovered within the
body. Three of these are normally present, though not
always easily made out : —

1. A nucleus, a discoid or spherical body slightly more
transparent than the surrounding endosarc, and usually
located toward the posterior end of a moving amoeba.

2. A contractile vesicle, a round clear spot within the
ectosarc. It may sometimes be seen to contract, and dis-
appear temporarily, and will then be certainly recog-
nized.

3. Ingested food particles. These appear darker than
the surrounding endosarc ; or if colored food particles have
been taken, microscopic green plants, etc., the color will
shine through. These are of various sizes.

These structures may be more readily made out in a
specimen that is stained with iodine. Place a drop of
iodine solution on the slide at one edge of the cover glass,
and place a bit of blotting paper at the opposite edge.
The blotting paper, by its absorbent action, will draw the
iodine solution under the cover glass, where it will pene-
trate and stain and kill the amoeba. The nucleus will be
more brightly stained than the other parts.

Make an enlarged drawing of an amoeba prepared in this
way, showing all the points of structure you have been
able to see.

By mixing some very finely powdered carmine or indigo
in the drop of water containing amoebas before covering,
their feeding may sometimes be better observed.

Occasionally an amoeba may be found dividing into two.
Such should be watched carefully.

The Life Process. — The jelly-like living substance which
makes up the body of the amoeba is protoplasm. It is

16 PROTOZOANS.

an almost structureless and colorless substance, in chemi-
cal composition much like the albumen of an egg. It is
the physical basis of life. Neither animal nor vegetable
life is known to exist apart from it. It is everywhere
present in the growing parts of animals and plants. It is
capable, as life's agent, of producing the most complex
structures. The nucleus within the amoeba is but a bit
of the protoplasm of slightly firmer consistency than the
rest ; but it is, perhaps, the most essential part.

Simple as the amoeba is, and wanting in parts, it yet
leads an animal life, and exercises all the essential animal
functions.

I. Nutrition. — That the amoeba takes food has been seen
already. Having neither mouth nor stomach, it ingests and
digests its food at the most convenient point. Its proper
food consists of the smallest microscopic plants. These,
when found within the body of a living amoeba, may, by
continued watching, be seen to dissolve away as they are
digested. The small amount of mineral food and the
larger amount of oxygen necessary for the amoeba are
already in solution in the water in which it lives, and
need but to be absorbed. These dissolved foods penetrate
freely to every part of the protoplasmic mass, and by a
process called assimilation they are incorporated into it,
and become a part of it. But this process means more
than the mere storing of digested food : it means that the
food is built up into complex chemical compounds, like
those which are the constituents of protoplasm, and that
it then becomes a part of the protoplasm, like any other
part, in all its properties. The necessary result of this
process is that the animal grows.

But this process also makes possible the animal's activi-
ties. The complex chemical compounds formed in this
constructive process are highly charged with potential
energy and are very unstable, like a single tier of bricks

THE AMCEBA. 17

that is piled too high, or like a train of gunpowder that
is ready to be discharged. As a light touch will upset
the bricks and cause them to fall with great force, or as a
spark will ignite the gunpowder and cause a violent explo-
sion, so, in a small way, a slight stimulus to the amoeba
will cause some of these complex molecules in the proto-
plasm to break up into simpler ones with the liberation of
the forces manifested in the animal's activities.

The simple compounds (carbonic-acid gas, water, etc.)
formed in this destructive process are of no use to the
amoeba, and must be removed. The name of the process is
excretion. These waste products pass out directly through
the body Avail into the surrounding water. It should be
noted that there is an important difference between this
true process of excretion and the mere egesting of an indi-
gestible bit of carmine : the latter does not become a part
of the animal's structure at all. Many such particles are
ingested in the course of feeding. It shows little choice in
the selection of food, ingulfing any object of convenient
size with which it may come in contact.

II. Reproduction. — The common method of reproduc-
tion in amoeba is simple division. First the nucleus divides
into two. Then the body elongates, and the nuclei move
apart toward the ends. A furrow then appears across the
body, between the nuclei. This furrow deepens until it
entirely separates the body into two pieces, each of which
is at once an independent, perfect amoeba.

The converse of this process has been observed. Two
amoebas have been seen to fuse together into one. It is
believed that this process (conjugation) is necessary for
the continued existence of amoebas. It has been proved to
be necessary in the case of some other microscopic animals
which reproduce ordinarily by dividing.

III. Voluntary Motion. — Protoplasm is contractile, i.e.,
capable of extending in one direction by shortening in

NEED. ZOOL. —2

18 PROTOZOANS.

another. But the movements of amoeba, simple as they
are, are yet more than the independent automatic contrac-
tions of protoplasm ; for they are controlled and coordi-
nated to certain ends, — to reaction in response to stimuli
from without, to locomotion and to securing food in
response to impulses from within.

IV. Sensation. — These latter acts indicate spontaneous
activity, and show that the amoeba possesses in a low
degree sensibility, the dawning of faculties which are the
highest endowment of animal life.

The Cell. — The cell in biology is a minute mass of pro-
toplasm containing a nucleus with or without a cell wall.
The amoeba is a single cell that has developed about itself
a very delicate and pliant cell wall.

The cell is the unit of all organic structure. Every
plant and every animal begins its existence as a single
cell. This cell grows and divides repeatedly; and the
cells thus formed remain together, and with their products
compose the bodies of the higher plants and animals. The
cellular character of the growing parts of all animals may
be easily recognized under the microscope.

When the amoeba divides, its parts separate. It there-
fore retains this simple condition, never becoming more
than a single cell.

THE SLIPPER ANIMALCULE.

(Paramecium.)

Study of Live Specimens. — Examine a drop of water
containing slipper animalcules. They appear as minute
white specks rapidly moving to and fro through the water,
just large enough to be seen without a lens.

Examine under the microscope a drop that has been
mounted on a slide in cotton fibers, or, better, in cherry-

THE SLIPPER ANIMALCULE. 19

gum solution, and covered.1 Use low power at first, and
make a general survey of the contents of the drop. Sev-
eral kinds of animalcules may be present. The slipper
animalcule (Paramecium) may be recognized by its elon-
gated, somewhat slipper-shaped form, and by its rapid pro-
gression with one end always forward.

Study its actions. Observe that paramecium, unlike
amoeba, when it reverses its direction of travel, turns
around ; that it has anterior and posterior ends. Yet it
can and does move backward when cornered, as may be
seen when one swims into a narrow space between two
cotton fibers, and has to batik out.

Find one that may be retained within the center of the
field, and examine it, magnified 300 to 500 diameters.
Observe : —

1. That paramecium has a definite, permanent, though
unsym metrical shape.

2. That its body is a single minute mass, without par-
titions or divisions ; i.e., that it is a single cell.

3. That its body mass is made up of two layers, —
(#) An outer, transparent ectosarc.

(6) An inner, granular, and more fluid endosarc.

4. That the whole body is covered over with delicate,
transparent processes, shaped somewhat like eyelashes, and
hence called cilia. In an active paramecium, these cilia are
moved so rapidly, they may be seen but dimly, like the
spokes of a rapidly revolving wheel. It is by means of
these cilia that the paramecium swims. They are used as
a boy's arms are used in swimming : they are struck back-
ward quickly and forcibly, and are drawn forward again
more slowly. It must be noted that they are not hairs,
but only delicate projections from the body wall.

Observe also, focusing up and down to bring into view
the parts at different levels, —

1 See Appendix, p. 279.

20

PKOTOZOANS.

5. An oblique groove (peristome) extending from the
anterior end halfway along one side of the animal, and so

twisted that its edges form an
elongated 8-shaped figure when
viewed from the side (see cut).

6. A fringe of cilia, longer and
stronger than those of the body,
all around the edge of this groove.
These set up currents in the water,
which may be seen, if there be any
loose sediment in the water, set-
ting to Ward the posterior end of
this groove.

7. A funnel-shaped chamber
(vestibule, or mouth) in the poste-
rior end of this groove. Toward
this the currents in the water tend,
and into it they drive the particles
they sweep along.

Near to this chamber, and in
the central portion of the body, is
an elongated, often spindle-shaped
nucleus, often hardly visible with-
out staining.

In one or two places in the body
there is a clear, round spot of con-
siderable size (usually one near
each end), which regularly ap-
pears and quickly disappears sev-
eral times a minute. Each of these
is a contractile vesicle. If one of
these be watched very closely, it
will be seen to have minute, radi-
ating tubes appearing around it when it contracts.

The remaining objects seen in the endosarc are food

PARAMEOIUM fx300). The
water current is driven in
the direction of the large
arrow by the lashing ac-
tion of the cilia of that re-
gion. Food particles pass
down the funnel-shaped
esophagus (e), and col-
lect in little round pellets
at the bottom. Then they
circulate about the body
in the direction of the
arrows, and indigestible
portions are ejected at «.
Two contractile vacuoles
(t>) are seen near the ends
of the body, and an elon-
gate nucleus (ri) may be
seen after staining.

THE SLIPPER ANIMALCULE. 21

balls and minute fat globules, and various foreign bodies
that have been swept into the mouth with food. The feed-
ing habits of the animal are best studied after putting
some finely powdered carmine or indigo into the drop of
water with it. Bits of these indigestible substances will
be seen swept along the groove by its cilia, through the
mouth, if they be small enough, for this is the only
entrance requirement, and down a sort of short rudimen-
tary esophagus, at the bottom of which they collect into
a little pellet before being ingulfed by the protoplasmic
mass of the interior. Then they may be seen to circulate
slowly about the body, and, after considerable time, to
collect at a point about halfway between the mouth and
the posterior end of the body, where they are egested
directly through the body wall.

The Life Process. — This is essentially as in amoeba ;
but there are some interesting differences in its details.

When any part of an animal becomes so modified as to
be better fitted for doing some one thing, that part is said
to be specialized. Thus in paramecium the cilia are
specialized for locomotion. One circlet of cilia — that
fringing the groove leading to the mouth — is still more
highly specialized for setting up currents in the water as
a means of capturing food. A mouth and short esophagus
are specialized for receiving food, and contractile vesicles
are specialized for circulating the fluids of the body. Every
time a vesicle contracts, it drives its liquid contents out into
the surrounding body mass. These specialized parts in the
one-celled paramecium foreshadow the locomotor, digest-
ive, and circulatory systems of the many-celled animals.

Amceba and paramecium are representatives of the Pro-
tozoa, a large group of microscopic unicellular animals of
wide distribution.

CGELENTERATES.

THE FRESH-WATER SPONGE.

(Myenia fluviatilis.)

Study of Live Specimens. — Examine fresh specimens.1
Note: —

1. Their form.

2. Their attachment: upon what kind of surfaces they

are found growing.

3. Their color.

4. Their odor, pecul-
iar, not unpleasant in
life, but rapidly becom-
ing very disagreeable if
any specimens have died.
This rapid decomposi-
tion of the sponge flesh
betrays its animal na-
ture.

Examine the surface
of the sponge with a

SPICULES OF FRESH-WATER SPONGE (My- d leng t find th t

enia fluviatilis) : a, skeleton spicules ; &

the others, gemmule spicules seen sidewise oles (or exlialent open-
at 6 and d, endwise at c and e. Qut of

life, currents of water are continually flowing.

Examine it still more closely to find the minute but
multitudinous pores (or inhalent openings) which cover

1 Directions for collecting are given in Appendix, p. 279.
22

THE FRESH-WATER SPONGE. 28

almost the whole surface, and through which the water
enters the sponge.

The sponge flesh is called sarcode. Press upon it, and
note its consistency.

Examining it again with a lens, note that it is bristling
with the points of very minute spicules, which are arranged
somewhat in lines, so as to form a sort of skeleton, running
through and supporting the sarcode. These skeleton spic-
ules are about ^-§ of an inch long.

The sarcode is permeated everywhere by minute canals,
which convey the water, taken in at the pores, to large
canals communicating with the osteoles. At certain places
in the smaller canals there are enlargements, which are
lined with cells bearing cilia. The water currents are
believed to be due to the lashing action of these cilia.

Gemmules. — Imbedded in the sponge flesh, and most
abundant near the base of the sponge, observe a large
number of small, round, yellowish or brownish seedlike
bodies; about the size of the smallest mustard seeds. These
are called gemmules.

Study gemmules which have been cleared and mounted
for examination.1 Under low power of microscope, ob-
serve the thick, yellowish coat of the gemmule opening at
one side by a foraminal aperture (called, usually, simply
the aperture) . In the outer coat of the gemmule observe
spicules which differ markedly from the skeleton spicules
in form. These gemmule spicules vary greatly in form in
different fresh- water sponges. If the sponge named at the
beginning of this section furnished the gemmules now
under examination, the spicules found in their outer coat
will be of the form of a spool, with the discoidal ends of
the spool notched to form radiating points, and with the

1 This preparation and the one following it, the student may make for
himself, if desired, by following directions found in Appendix, p. 280.

24 CCELENTERATES.

slender axis of the spool produced into a short point
(umbonate) at each end. The axes of these spicules are
directed toward the center of the gemnmle, so that, on
looking at the surface of the gemmule, only the radiate
disks on the distal end of the spicules are seen. Looking
at the cut edge of the outer coat of a gemmule which
has been divided in halves, a lateral view of some of the
spicules will be obtained, and their somewhat spool-shaped
(birotulate) outline will be recognized.

For a better view of both skeleton and gemmule spic-
ules, examine some which have been isolated with nitric
acid and mounted separately. Draw typical spicules of
both kinds.

Make an outline drawing of the whole sponge. Fill in
the details in a part of the drawing so as to show osteoles,
pores, and gemmules.

The gemmules are reproductive bodies ; and their outer
coats, strengthened with beautiful spicules, however inter-
esting in themselves, are of value to the sponge only as
they form a protective covering for the protoplasmic con-
tents of the gemmule.1 When, in winter, the old sponge
dies down, and the gemmule has been set adrift, the
protoplasmic cells of its interior in some favoring situa-
tion escape through the aperture, associate and attach
themselves in a relatively compact mass, and begin to
take food from the surrounding water, and to grow up
into a new sponge.

In watching the development from gemmules, note the
following.2

1. The protoplasmic contents of the gemmule may be
seen to issue by amoeboid efforts, to grow and develop sar-

1 The gemmule is formed (Marshall) by a number of free amoeboid
sponge cells which come together at some point in the sarcode, and secrete
a thin pellicle about themselves. The surrounding cells secrete the outer
coat of the gemmule, with its supporting spicules.

2 For methods of preparation for this, see Appendix, p. 281.

THE FRESH-WATER SPONGE. 25

code with its supporting spicules, its pores, osteoles, and
communicating canals. The abundant secretion of sili-
ceous spicules by this simple protoplasmic mass, and the
arrangement of them in definite lines to form a skeletal
structure, are easily seen, and are somewhat remarkable
phenomena.

2. The sarcode masses produced from few or many
separate gemmules may be seen to meet and coalesce to
form a single sponge, showing further the aggregate nature
of the animal.

The Life Process. — When the amoeba divides, its cells
separate as independent animals ; but when the pr.oto-
plasmic mass of .the sponge gemmule divides off new
cells, these cells remain aggregated together. Although
they arrange themselves so as to inclose water canals
when their whole mass becomes too great for contact of
all parts with the water, and although they cooperate in
the formation of spicules in more or less definite lines,
they yet lead in some respects an independent existence,
in that each cell lives, eats, assimilates, grows, excretes,
and divides for itself. The life process in each cell is
therefore not greatly different from that of the single
cell of amoeba, save that the sponge cell is more limited in
its search for food, being compelled to take such as the
water currents bring to it. But this loss of power to the
single cell is obviously to the advantage of the sponge as
a whole. And just in proportion as the individual cells
lose their individuality, and become arranged and ordered
for the good of the animal they compose, the animal ceases
to be a mere aggregate of cells, and becomes an integrate
organism.

Differentiation is the term applied to the way cells have
of growing different, — of becoming unlike in form when

26 CCELENTERATES.

combined together to form an animal of more than one
cell (a metazoari). Thus the ciliated cells in the water
cavities of the sponge have become differentiated from
those which possess no cilia.1

THE HYDRA.

(Hydra viridis ?)

Study of Live Specimens. — In an aquarium or glass
jar in which hydras are kept2 study the creatures alive.
Observe : —

1. Their shape, — elongated, cylindrical, Avith the body
attached at its posterior or foot end to some support, free
at its anterior end, and crowned with a circle of long,
radiating tentacles.

2. Their color.

3. Their position: if all are in the same position; if all
are attached to the same kind of a support; in what part
of the vessel they are most numerous.

4. Their actions. Note the swaying-about of the long
tentacles in the water. These capture food. A minute
animal that has been captured may sometimes be seen,
before it is carried to the mouth, sticking to one of
the tentacles. Touch the tentacles, and see them con-
tract.

If the hydra jar be so placed that light reaches it
strongly from but one side, after some time the hydras
which are on the opposite side of the jar will move
toward the light, when their slow and very peculiar loop-
ing locomotion may be seen.

1 For a further study of this and of related sponges, the student is re-
ferred to Potts's Monograph of Fresh-Water Sponges. For a good dis-
cussion of the relations and differences between plants and animals, he is
referred to Parker's Elementary Biology.

2 See Appendix, p. 282.

THE HYDRA. 27

5. Their three methods of reproduction : —

(a) By buds. These are blunt processes often seen
sticking out at right angles to the body of the parent
hydra, outgrowths from its sides, destined to become perfect
hydras, and, when well grown, to separate, and lead an
independent existence. All stages of the budding process
may usually be found, from the incipient bud without
tentacles, to the fully formed hydra ready to drop away.

(5) By true sexual organs, — minute cone-shaped or
dome-shaped eminences on the sides of the body, just
visible without a lens.

(c) By a sort of vegetative reproduction, like the starting
of a new plant from a slip or cutting taken from an old
one. To see this will require a carefully conducted exper-
iment, costing a little time and trouble, but worth both.
Cut out a piece of leaf with three hydras on it, and place
it and them in a separate vessel of water. With a pair
of thin, sharp scissors, cut off a tentacle from one of the
hydras, to see it reproduced. Cut the second hydra in two
crosswise, and slit the third one into two pieces length-
wise. If properly done, the pieces will live, and each
will develop into a perfect hydra. The progress of these
specimens should be watched daily, and as much oftener
as is convenient.

Detach a hydra from its support, take it up with a
dropping tube, and place it in a watch crystal containing
water under the microscope, and examine with low power.
Observe : —

1. The broad or flattened foot by which it was attached.

2. The flexible cylindrical body (often distended in
places by food, or extended into buds).

3. The tentacles: their number; their knotted appear-
ance ; their action.

4. The cone-shaped prominence (hypostome) at the
anterior end, between the bases of the tentacles.

28 CCELENTERATES.

5. The mouth, which is at the top of this prominence,
and may be seen in favorable positions; i.e., when it is
turned upward and opened.

Structure. — Mount the hydra alive in a drop of water
upon a slide. Place two minute slips of paper or two
threads alongside the hydra, and lower a cover glass upon
these. Examine first with low, and afterward with higher
power, to make out the following points of structure : —

1. The body is a hollow tube with but one opening to
the exterior, the mouth. The interior of this tube is the
gastric cavity. Observe that this cavity extends out into
the buds, when present, and into the tentacles. When
the tentacles are fully extended, food particles may be
seen in them.

2. The body Avail is double. Its outer coat (the ecto-
derm) is made up of small transparent cells ; its inner
coat (the endoderm), of larger, darker cells. The body is
therefore a double-walled sac, both walls of which are
pushed outward to form buds and tentacles.

3. In the ectoderm, in parts of the body, and especially
in the swollen parts of the tentacles, are certain conspic-
uous round or oval cells surrounded by smaller ones.
These larger ones are called thread cells, lasso cells, or
nettle cells, because they contain a long, spirally coiled
thread, which can be thrown out at will, and is used in
capturing prey. When the long, swaying tentacles ap-
proach some animal suitable for food, as a water flea, these
threads are thrown out, and, coming in contact with the
flea, they seem to paralyze it. It hangs apparently stunned,
adhering to several of these threads, and is quickly swept
into the mouth. If a drop of acetic acid, magenta, or
methyl green be drawn under the cover glass, and the ten-
tacles watched at the same time, the throwing-out of these
threads may be seen. Afterward some of these lasso cells

THE HYDRA.

29

may be found entirely dislodged from the tentacle, and
showing, beside the long stinging filament, a flask-shaped
base, with minute retrorse spines at the neck of the flask
whence the filament springs.

4. The sexual reproductive elements are developed in
low elevations upon the sides of the body. These are of
two kinds : —

(a) Spermariet, — conical, pointed elevations near the
anterior end of the body, just behind the tentacles, of

HYDRA (X 6) : m, mouth; sp, spermaries ; ov, ovary; b, bud.

variable number. In the transparent apex of a ripe sper-
mary, the sperms may be seen swimming actively about or
breaking out into the surrounding water.

(6) Ovaries, — rounded, obtuse elevations nearer the
foot, rather larger than spermaries when ripe, usually
fewer in number, and each containing but a single ovum.

Both spermaries and ovaries are developed from the
ectoderm, as might be inferred from their position and
from their transparency.

30 CCELENTERATES.

Sexual Reproduction consists in the production of male
and female reproductive elements, sperms and ova, and in
their union to form oosperms, and in the development of
the oosperms into new individuals. At first certain cells
are separated off from the other cells of the body, and in
certain parts of the body, specialized for the purpose, are
developed into sperms and ova. Then the sperms of the
hydra escape out into the water, and swim actively about
until some of them come into contact with the ova of
another hydra. One sperm enters and coalesces with
each ovum, changing it into an oosperm. Fertilization
is the name for this part of the process. The resultant
oosperm hardly differs from the ovum in appearance, yet
vitally differs from it, in that the oosperm has the poten-
tiality to become, under proper conditions, a new hydra.

When both kinds of sexual elements are produced in a
single individual, the individual is said to be hermaphro-
dite. In the hydra, spermaries are developed first; and
not until after they are ripened, and their sperms dis-
charged, do the ovaries mature their ova. The ova can-
not, therefore, be fertilized by sperms from the same
individual, but Avill be fertilized by sperms of a later
growth from some other individual. This is called cross
fertilization : it seems to be essential to the healthy con-
tinuance of most animals.

The Life Process. I. Nutrition. — In the hydra we
have our first example of an animal with a distinct gastric
cavity, in which food may be received and retained until
digested. We find, also, better means of securing food than
in any protozoans. After the food is taken by the tenta-
cles and the extensible mouth, it is pressed down into the
digestive cavity, and there the endoderm cells do most, if
not all, of the work of reducing it to soluble form. These
lining cells are large, and capable of considerable amoeboid

THE HYDRA. 31

motion, which may be seen in thin transverse sections
cut from a living specimen. Their combined motions
probably have much to do with comminuting the food.
Their secretions probably act on it chemically to digest
it; but when it is digested, it must pass out to all parts
of the body by simple osmosis from cell to cell, and by
the slight propulsion given by the moving of the parts
of the body upon one another, for there are no circulating
vessels. There being but one external opening to the
digestive tract, the indigestible portion of the food must
be cast out, as it is taken in, through the mouth. The
absorption of free oxygen and of mineral foods in solu-
tion in the water, takes place directly through the body
wall. The assimilation of these various foods from vari-
ous sources, the building of them into the body structure,
and the removal of the waste products of activity, —
these things, in hydra, as in all animals, each cell does
for itself.

II. Reproduction. — That .the hydra is hermaphrodite
has already been seen, and also that it reproduces
greatly by budding. Did these buds remain perma-
nently attached, as in some of the hydra's marine rela-
tives, instead of falling away when fully grown, we
should have it developing a peculiar treelike form.
Hydra does not divide of itself into two equal parts, but,
when so divided artificially, the parts may each become
a new hydra with all lost parts reproduced. Pieces much
smaller than half the animal may grow into perfect hy-
dras. It seems to be only necessary that all the essential
structures be represented, and probably is most essential
that the ectoderm (the reproductive layer) and the erido-
derm (the digestive layer) be present and in their proper
relations together.

III. Voluntary Motion. — The hydra is another of the
animals that "move without muscles." Yet its move-

32 CCELENTERATES.

ments are varied and interesting. They are ceaseless,
too, as may be seen by watching its continually changing
form. Though all its individual cells have the power
of motion, some cells, as those in the tentacles, move
more freely than others. The lasso cells are capable
of a very sudden and remarkable and highly specialized
act, — the thro wing-out of their paralyzing filament.

IV. Sensation. — No nervous system is developed in the
hydra; but a few nerve cells, developed between the bases
of the ectoderm cells, are known to exist. There is a
marked advance in the powers of sensation of this animal
over those previously studied, seen in greater reaction
from disturbances, in greater skill in securing food and
more choice in selecting it, in preference for light, etc.

Tissue and Organ. — The cells of the ectoderm in
hydra, being much alike in form and in the work they
have to do, constitute a primitive tissue. The cells of the
endoderm constitute another such tissue. A tissue may
be defined as an aggregation of similar cells, together with
whatever intercellular substance may be developed from
the cells.

When any part of an animal is set apart for a particular
work, that part is called an organ, and the work it has to
do is called its function. Thus the tentacles of the hydra
are organs, and their function is reaching out after food.

Differentiation becomes very evident in the hydra.
The thread cells of the tentacles are very unlike the
digestive cells of the endoderm in the digestive cavity.
In the work they have to do, there is quite as great dif-
ference as in their form. The thread cells are given a
specific work to do, — the capturing of food. Other cells
do the digesting, and can do it better for being relieved
of the work of capturing the food. This is what is meant
by a physiological division of labor. This sort of spe-

THE HYDRA. 33

cialization, so evident in the development of animals, has
its parallel in the development of civilization or in the
development of a trade. For example, the early cobbler
tanned his own leather, whittled his own pegs, made his
own thread, lasts, etc., and then made the shoe. But, as
the trade of shoemaking developed, one man began giving
his whole time to making the leather ; another, to making
the lasts, etc. ; and another, to making the shoe. To see
how much further than this the division of labor in shoe-
making has gone in our own time, we need only to visit a
modern shoe factory.

When the cobbler gave up to the tanner the making of
the leather, he became a more skillful shoemaker, but lost
his skill at tanning. So, when the thread cell of the
hydra becomes differentiated for capturing food, it excels
in that one thing, but it loses its capacity for doing other
things. Here we come upon the universal principle, that
precise adaptation to any one thing involves limitations in
other things.

Division of labor develops greater skill and better
products in a trade, higher powers and capacities in
animal life. While there are many things which cells
and cobblers may leave to be done by others, to the ad-
vantage of all concerned, there are yet other things which
each must continue to do individually. For example, the
thread cell, though it may be relieved of the work of
digesting its food, must continue to absorb the digested
food as it is furnished, and assimilate it; must absorb
oxygen, and must excrete waste oxidized materials for
itself, so long as it continues a living cell.

The hydra and the sponge are representations of the
Coelenterata, a large and important group of animals,
almost exclusively marine.

NEED. ZOOL. — 3

INSECTS.

Collecting. — Insects are abundant in nearly all locali-
ties throughout the interior of the United States. There
need, therefore, be no lack of material at the proper sea-
son. And because this group illustrates well the principles
of zoology, and furnishes animals of
singular beauty, variety, interest, and
importance, it may profitably be studied
as long as the limitations of time will
permit.

Three special pieces of apparatus will
be needed, — a collecting net, a cyanide
bottle, and a collecting basket.

The net is for catching insects. To
make it, get a light, wooden handle two
or three feet long, a piece of heavy wire
(about No. 8) two feet and a half long,
several feet of small wire (broom wire
will do), and a square yard of " Swiss "
or mosquito netting. Bend the heavy
wire in a circle, crossing the ends and
bending them parallel. Cut a groove
in the end of the handle, and continue
it down the sides. Place the crossed ends of the wire in
this groove on opposite sides of the handle, and wrap them
there securely with the small wire. Make a bag of the
netting, of the same diameter as the wire circle, and about
two feet deep. Sew this on the wire circle, and the net is
complete. With a very little practice, it can be used suc-

34

FRAME FOR INSECT
NET: a, loop of
wire; b, handle;
c, wire and han-
dle in place.

COLLECTING 35

cessfully. When by a stroke the insect is caught, a quick
turn of the hand makes a fold in the net, and prevents
its escape.

The cyanide bottle is for killing insects that are to
be preserved as specimens. Get a wide-mouthed bottle
of a capacity of at least a pint, half an ounce of potas-
sium cyanide, a handful of plaster of Paris, and a poison
label. Break the cyanide into small pieces (avoid its
poisonous fumes), and place them in the bottom of the
bottle. Pour in just enough water to cover them. Add
plaster of Paris until it remains dry over the entire sur-
face. The plaster will quickly set, forming a porous
poison cake in the bottom. Let the bottle stand uncorked
for half a day; then shake out the surplus plaster, wipe
clean the sides, cork, affix the poison label, and keep out of
the way of children. Most insects, when shut inside, die
at once. To transfer a captured insect from the net to the
bottle, push the uncorked bottle carefully up inside the
folded net.

The collecting basket is for carrying insects home alive.
A close-woven basket with a netting cover will answer
every purpose. Any kind of basket will do, if lined with
netting. A place must be fixed at the edge for putting in
and taking out the insects.

In collecting, always observe the following rules : —

1. Collect no more specimens than will probably be used.
The taking of more is but the wanton destruction of life.

2. Get for preservation the finest specimens obtainable,
and preserve them with utmost care. Fine specimens are
always a delight, and poor ones are of no credit to any one.

3. Keep live specimens supplied with food, water, and
fresh air. To let an animal die a lingering death for want
of either of these common necessities, is extreme cruelty.

4. Make each collecting trip an opportunity for study-
ing animal life under natural conditions. Make note of

36 INSECTS.

the haunts of each animal, of its animal associates, of its
food, of its shelter, of its natural enemies, of its home, —
in short, of the life it leads. Such study will lead to
important general truths relating to all animal life, includ-
ing that of man, and is best begun in the field.

5. Remember that fear is inherent in most animals, and
that flashy colors, loud noises, and quick and careless move-
ments will frighten them, and cause the loss of opportuni-
ties for observation. Hence wear quiet colors, avoid
noise, avoid haste, and keep your eyes wide open.

HEXAPOD INSECTS.

THE BUTTERFLY.
(A PRELIMINARY LESSON.)

Characteristics. — The common sulphur butterfly (Eury-
mus philodice J) will serve well for a beginning in the study

of insects. It may be known by its
yellow wings bordered with black,
and by a silvery spot set in a patch
of pinkish brown on the lower sur-
face of the hind wings. Like other
butterflies, it may best be collected
about midday. Any clover field
or meadow will probably furnish a

supply. Any other butterfly that
THE SULPHUR BUTTERFLY,

Eurymus philodice (natu- can easily be collected will answer
ralsize)« the present purpose quite as well.

Study of Live Specimens. — Collect specimens for imme-
diate use and for preservation,2 and while collecting study
the living butterflies and their haunts and habits, noting : —

1 Colias philodice of some authors.

2 Observe that all the specimens captured are not in equally good con-

THE BUTTERFLY. 37

1. The species of the flowers on which you find them
feeding.

2. The manner of their feeding: whether they, like
humming birds, obtain their food while on the wing.

3. The kind of food: it is the nectar of the flowers,
the raw material for honey. To prove its presence in the
flowers, pluck a few corollas from a head of red clover,
and press their bases between your lips : you will taste
the sweet nectar.

4. The organ used in obtaining this food : its position
when in use and when not in use ; its shape; its length.

5. The natural enemies of the butterfly; to what dan-
gers its life is commonly exposed.

6. Its animal associates; with what other animals it
shares its food.

When you get home, liberate a live butterfly before a
closed window, and study its motions.

Observe: 1. The position of its wings when at rest.

2. The unity of their action when in motion.

3. Its irregular flight.

4. Its jerky walk.

5. The number of its feet; the number moved at a time
while walking.

Take time to admire the beauty and harmony of its
form and coloration, the alertness of its posture, and the
exquisite velvet of its wings.

It is at once apparent that in its activities and capacities
the butterfly far surpasses amoeba, sponge, and hydra. The
first few steps up the grade of animal life we took in their
proper order; but now, for the sake of convenience, we

dition. Some have their wings rubbed and torn. Place such in the bas-
ket, and take them home for further study alive. Put the best in the
cyanide bottle. It is well to have two cyanide bottles, — one to kill and
one to carry specimens in, — for the fluttering of live specimens put into
the bottle may rub and mar the beauty of former captives which have not
been removed. See note on mounting insects, in Appendix, p. 283.

38

INSECTS.

ant

pass by those which would succeed in logical order, to
study a group of animals that is highly specialized.

Plan of Structure. — A superficial study of the external
features of the butterfly will give a general idea of the
insect plan of 'structure. Examine a butterfly which has
been killed in the cyanide bottle, and observe its horny
incasement, — an outside skeleton covering the whole sur-
face, but thickest and hardest on those parts of the body

most exposed. This
is a very different
exterior from that
of the sponge or the
hydra : such ani-
mals, if exposed to
the air, would soon
die of evaporation,
if from no other
cause. This hard
exterior is an adap-
tation to aerial life,
as well as a protec-
tion against injury.
This coat of mail in
insects is an out-
growth from the skin, and is composed of a horny sub-
stance called chitin. It is very light and very tough, —
two important requisites in the armor of a flying animal.

Place the butterfly in its erect position, with the head
away from you, and compare the right and left sides with
reference to the arrangement of parts. Observe that
the parts correspond, that the sides are symmetrical.
Bilateral symmetry is the term used in zoology to desig-
nate such arrangement of parts. What animals have you
seen that are not bilaterally symmetrical ?

trn

DIAGRAM OF SULPHUR BUTTERFLY (X2), de-
nuded of scales, right wings removed:
h, head; 1, prothorax; 2, mesothorax;
3, metathorax; a, abdomen; w I, left fore
wing; w 2, left hind wing; black ™'s indi-
cate the points of attachment of right wings ;
ant, antenna ; e, eye ;p, palpus ; m, "tongue ;"
ex, coxae of right legs ; tr, trochanter of right
hind leg ; /, femur ; t, tibia ; trs, tarsus or
foot.

THE BUTTERFLY. 39

Observe that there are three somewhat distinct regions
in the body. These are named, in order, head, thorax, and
abdomen.

Observe that the entire body is made up of rings or seg-
ments. How many segments are there in the thorax? In
the abdomen?

Note now the external parts and appendages.

1. The Head. — 1. The long projections on the front of
the head are antennae. These also have segmented struc-
ture. Study them with the aid of a lens, and count their
segments.

2. The large hemispherical prominences on the sides
of the head are the eyes, called also facets or compound
eyes, because they appear under magnification to be made
up of clustered simple eyes placed side by side.

3. The two more or less hairy appendages in front of
and below the eyes are the labial palpi. Count their seg-
ments, and find their point of attachment to the head.

4. The coiled organ between the palpi is the sucking
organ (or proboscis) . Uncoil it : how many turns in it ?
Notice the permanent bend near the middle of it. Ob-
serving that there is no oral opening on the surface of
the head, what structure will you expect to find within
this proboscis?

With the microscope examine : —

1. A cross section of the proboscis.1

2. A tangential section of the surface (corneal layer)
of the eye.2 Observe that the corneal layer seems to

1 To make the cross section, place the proboscis uncoiled in a split
cork or between two pieces of elder or cornstalk pith, and, holding it
firmly there, with a razor or a very sharp knife shave off thin sections at
the end, shaving the holder and the proboscis together.

2 Cut a section from the surface of- the eye. Holding the section with
fofceps by one edge, scrape out the dark-colored pigment from its inner
concave surface. Place it on a slide, convex surface uppermost, and it
is ready for examination. Use low power.

40 INSECTS.

be composed of many hexagonal corneas. Make a draw-
ing of a portion of it as seen under the microscope.
Count the corneas in a certain visible space. Estimate
what part this space is of the whole corneal layer, and
calculate the number of corneas in the whole layer.

II. The Thorax. — Note that the thorax is composed of
three segments.

1. The small first segment, to which the first pair of
legs is attached, is the prothorax.

2. The large second segment, to which the second pair
of legs and the first pair of wings are attached, is the
mesothorax.

3. The third segment, to which the third pair of legs
and the second pair of wings are attached, is the meta-
thorax. Owing to 'the consolidation of meso- and meta-
thorax, the boundary between these segments may not
be very plainly seen.

Observe that the thorax is in cross section more or less
quadrangular, showing more or less flattened dorsal, lateral,
and ventral surfaces. The dorsal surface is called the
notum, each lateral surface a pleurum, and the ventral
surface the sternum. The convenience of this notation
will be seen in the ease with which, by using it, any part
of the thorax may be designated. The upper or lower
part of the prothorax may be referred to as pronotum or
prosternum ; corresponding parts of the metathorax, as
metanotum or metasternum, etc.

Examine one of the legs. Note that it, too, is made up
of segments, which, like those of the body, have a hard
outer shell of chitin. Flex and extend, and study the
action of the joints.

1. The first small segment, the one by which the leg
articulates with the body, is the coxa.

2. The next is a very small quadrangular segment, not
always easily made out, the trochanter.

THE BUTTERFLY. 41

3. The next is the largest segment of the leg, the femur.

4. The next is a slender segment about as long as the
femur. It is the tibia.

5. The remaining segments comprise the foot (or tarsus).
Count these tarsal segments. Note what appendages are
present, and on which segments. Examine the lower sur-
face of these segments. Discover by what means the
butterfly is able to walk on the lower surfaces of leaves.

Examine the wings, noting: —

1. Their action.

2. Their form.

3. Their overlapping.

4. Their covering of hairs and dust-like scales.

5. Their structure, — each a triangular expanse of thin
membrane supported by chitinous veins. Find five prin-
cipal veins starting outward from the base of a wing.
These are named1 from front to rear, costal, subcostal,
median, submedian, and internal. Their branches, when
present, are called veinules or veinlets. The subcostal and
median are branched in butterflies. The costal and inter-
nal are simple. The internal is often very short and
inconspicuous in the fore wings.

Make a drawing of the butterfly as seen from one side,
with wings closed, first arranging antennae and feet in a
natural position. Make a drawing of it as seen from
above, with wings extended.

With the microscope examine : —

1. The foot.

2. A cross section of one of the larger veins of the wing.
Rub off a few of the dust-like scales of the wing, and

examine, first with moderate and then with high power, —

1. A bit of the wing with scales attached.

2. A bit of the wing with scales rubbed off.

3. The detached scales. Draw.

1 See footnote, p. 87.

42 INSECTS.

III. The Abdomen. — Observe the form of the abdomen;
its markings; the absence of lateral appendages. Count
the abdominal segments, and, by bending slightly, observe
how they are fitted together. Observe a longitudinal
groove on either side of the abdomen. Just above this
groove, in each segment, is the opening (more or less
completely covered by scales) of a breathing pore (or
spiracle).

Make a drawing of the abdomen, lateral view.

THE DRAGON FLY.

(Diplax.)

Haunts and Habits. — The young of the dragon fly lives
in the water on the bottom of brooks and shallow ponds.
The adults live in the air, and may be seen through the day,
poised on glistening wings above the water, or darting
hither and thither with great swiftness. The adults may
be collected with a net, but some little dexterity will be
necessary to catch the larger species. A small brown
species (T)iplax rubicundula), with amber-tinted wings, is
abundant in most places throughout the interior, and is
easily captured about wet meadows, and is a good example
for class use. It is always well to collect a number of
species for comparison. While collecting, observe: —

1. The places frequented.

2. The habit of flight.

3. The hours of flight.

4. The food sought.

The adult female dragon fly may sometimes be seen
hovering low above the water, dipping the end of her
abdomen occasionally beneath the surface, there deposit-
ing eggs. If captured unhurt, and held gently by the
fore wings while the dipping is done artificially in a turn-

THE DRAGON FLY. 43

bier of clean water, the eggs will usually be deposited
there. They should be collected and taken home in water,
and their development studied.

The young of the dragon fly are called nymphs. They
are commonly found sprawling on the bottom of shallow
brooks or ponds, or clinging to submerged trash or to
aquatic plants. Easy marks of recognition are the wide
head and thorax, very rudimentary wings, and a much-
enlarged and armed lower lip, which covers the mouth as
a shield. A water net will capture such as cling to sub-
merged green plants. Those found in trash fallen in the
water's edge may be raked ashore with the trash and
picked up by hand, their active efforts to return to the
water making them easy to find. All may be carried
home in a small pail of water. They live upon aquatic
insects ; and a supply of their insect food should be col-
lected at the same time, and placed in the pail with them.
A few strokes of a water net through a pool will usually
catch a supply of suitable food. A few submerged green
water plants should also be placed in the water with them,
to furnish oxygen. The contents of the pail may be
turned out into a bowl or other improvised aquarium at
home, and there the nymphs will live and grow, and
finally transform into adult dragon flies.

Study of the Adult. — Liberate a live dragon fly in a
•closed room (it has no sting, and is in no way hurtful to
man), and study its actions. Note: —

1. The position of its wings in motion and at rest.

2. The position of its legs.

If you can time its passage across the room, make an
estimate of its speed in number of times its own length
per second. Compare this with the speed of a fast horse
reduced to the same terms.

Put a live dragon fly into the cyanide bottle, and as

44

INSECTS.

soon as it is thoroughly stupefied by the poison, but not
killed, turn it out again upon a paper, and study its re-
spiratory movements. Note the regular expansion and
contraction of its abdomen, and search with a lens for

the minute openings
of spiracles on each
abdominal segment.
Two larger spiracle
orifices may be found
on each side of the
thorax.

Observe the spin-
dle-shaped body; the

DRAGON FLY (natural size).

rounded head, con-
. cave behind; the wide
thorax; the angled and tapering abdomen.

I. The Head. — Note the enormous development of the
eyes.

Find a minute single eye (ocellus) above the base of each
antenna, arid another on the median line slightly farther
forward.

Remove an antenna entire, and examine with a micro-
scope. Compare with the antenna of a butterfly. Draw.

Turn to the mouth. Find an upper, movable lip (the
labrum) and a larger, two-cleft, lower lip (the labiurn).
Turn back the labrum and the labium, and find just beneath
the labrum a pair of toothed, horny mandibles. Beneath-
these find another pair of jaws, also working horizontally
(the maxillce). Remove a maxilla entire, and examine it,
first with a lens, and afterward with low power of the
microscope. Note that it is a compound organ, made up of
a two-jointed basal portion bearing two terminal append-
ages. The inner appendage is the cutting or chewing part
of the maxilla (the lacinia, or blade); the other append-
age, standing behind or beside the lacinia, is the palpus.

THE DKAGON FLY. 45

If these parts are difficult to see, compress a maxilla
between two glass slips, and examine it under slight magni-
fication. Compare this mouth with the mouth of a butter-
fly. To what method of feeding is this mouth adapted?

II. Thorax and Abdomen. — Find in thorax and abdomen
all the parts as mentioned for the butterfly, noting these
special points : —

1. The relative development of the thoracic segments.
Which is smallest, and which largest?

2. The approximation of the legs. Why are the three
pairs thus bunched together; i.e., what advantage is there
to the animal in such arrangement?

3. The richly veined, naked, transparent wings. The
costal vein is on the anterior margin of each wing, and the
subcostal and median veins are parallel with it as far as
the middle of the wing. There a stout cross vein (the
nodus) crosses these three, dividing the wing in halves.
On the costal margin beyond the nodus is a thickened
dark spot (the wing spot, or ptero stigma).

The close correspondence between the appendages of the
dragon fly and those of the butterfly will have been noticed
ere this by every student. That the legs and wings and
other parts have essentially the same structure in the two
animals, is very apparent. Had the origin of these parts
been studied in the developing young of each animal, a
similar correspondence would have been noted. When
the parts of two animals show correspondence in structure
and origin, such parts are said to be homologous; when
they correspond merely in use, and not in either structure
or origin, they are said to be analogous.

The legs of a butterfly are analogous with the cilia of a
slipper animalcule, because both structures have similar
use as locomotive organs ; but they are not homologous.
The wings of the dragon fly and of the butterfly are homol-
ogous, although very different in appearance; for they

46 INSECTS.

have essentially the same structure, — a double fold of
membrane supported by chitiiious veins, — and they are
very similar in development.

Study of the Nymph. — Place a large nymph in a small
dish with just enough water to cover it, and study it
alive, with the aid of a good lens. Observe : —

1. Its sturdy form.

2. Its large eyes.

3. Its short antennce.

4. Its enormous lower lip, covering the lower and front
parts of the head. Seize the edge of it with fine -pointed

forceps, and pull it forward for exami-
nation. Note that it is so jointed to
the head that it can be extended far
forward, and quickly retracted. Note
that it is two-lobed, that the lobes are
triangular, that each bears an incurved
hook at the apex, that each is toothed
along its inner margin, and that the
A DRAGON-FLY NYMPH, whole is a very formidable grasping
organ.

5. Its mouth, with well-developed mandibles and max-
illse inside the labium.

6. Its rudimentary wings. Compare with those of the
adult.

7. Its well-developed legs. Compare them in position
with the legs of the adult.

8. The regular expansion and contraction of its abdo-
men in respiration. Note the striking unlikeness of the
respiratory methods in the adult and in the nymph.
The adult lives exclusively in the air ; the nymph, exclu-
sively in the water. Both must get oxygen from the
air. Internal branching and intercommunicating air tubes,
which open exteriorly at the spiracles in the adult, con-

THE DRAGON FLY. 47

vey currents of air throughout the body. But the nymph
must utilize the air which is in the water, mixed with
the water, or held in solution by it. To get this air, the
water is alternately drawn into the abdomen at the anal
opening, and forced out again. In passing in and out,
the water flows over a number of modified air passages,
called tracheal gills, which are situated just within the
anal opening.1 These tracheal gills have very thin walls,
easily permeable by gases. They contain air to be
purified. In respiration, osmosis (or exchange of gases
through the thin walls of the tracheal gills) takes place;
carbonic-acid and other noxious gases from the body
passing out into the water, and oxygen from the air
contained in the water passing in.

To prove the passage of water into and out of the
abdomen, with a small pipette pass a fine stream of red
ink or other colored fluid close by the anal opening, and
see it alternately drawn and repelled by the water
currents.

Keep some large nymphs half a day without food.
Then put into the water with them an abundance of the
insects they feed upon (such small ones as a net will
catch in any pond), and observe how they capture, hold,
and devour their prey.

Development. — The egg hatches, and a nymph comes
forth. It is at first very small ; but it eats voraciously,
and grows rapidly. It develops a delicate chitinous coat;
and when this gets too small, it splits down the back, and
the nymph crawls out, and grows another of larger size.
This molting takes place a number of times before ma-
turity is reached. On the bottom of a vessel in which
nymphs have been kept for some time, a number of
empty nymph skins (exuvice) may usually be found.

1 Some species have external tracheal gills.

48 INSECTS.

When the nymph is fully grown, it crawls out of the
water upon some convenient rock or reed, and fastens its
feet firmly, preparatory to the last and most remarkable
transformation of all, — the transformation which fits it
for an aerial life.

Keep some of the largest nymphs, supply them with
proper food, and watch their final transformation.

Make a series of drawings of the egg, of nymphs of
different sizes, and of the adult, of one species. This
will be a pictorial life history of the species.

The dragon flies constitute the group Odonata.

THE GRASSHOPPER.

Haunts and Habits. — A large gray species, properly
called the Carolina locust (Dissosteira Carolina), is abun-
dant by every roadside,
and will serve well for
class use. It may be rec-
ognized by its large yel-
low-bordered hind wirlgs,

exposed in flight. It may

THE CAROLINA LOCUST, Dissosteira v t«T,.pn w;fu a ^pf arirl
Carolina (natural size). be taken Wltn a net' anCL

killed with a cyanide bot-
tle. Nymphs will be found in the same situations as the
adults. They resemble the adults quite closely in form,
but are smaller, and lack fully developed wings.

Collect nymphs in all stages.

Collect adults of different species for comparison.

Collect for dissection a few of the very largest speci-
mens obtainable, of any species.

Study in the field (for the Carolina locust) : —

1. Its protective coloring.

2. Its several methods of locomotion.

THE GRASSHOPPER. 49

3. The sounds (stridulatiori) made by some individuals
(males) while on the wing.

4. Its hours of activity.

5. Its natural enemies.

6. The effect of temperature upon its activity. Go out
some frosty morning for this purpose.

Place a live specimen under a tumbler, and study : —

1. Its respiratory movements. Observe the opening
and closing of two lips that guard the entrance to a large
spiracle just above the base of one of the middle legs.
Find other active spiracles.

2. The size and arrangement of its legs in relation to
the locomotor habits of the animal; which legs are most
serviceable in walking, in leaping.

3. Its manner of feeding. Place some fresh leaves of
clover or of lettuce under the tumbler with the insect,
and watch it eat. If kept without food for half a day, it
will eat greedily.

Liberate an active specimen in a warm room, and
measure its longest leap in number of times its own
length.

External Anatomy. — Observe the relative development
of head, thorax, and abdomen.

Examine, as before, the upper parts of the head, eyes,
ocelli, and antennae.

I. Mouth Parts. — Study the mouth parts with especial
care ; for in the grasshopper all the typical mouth parts
of an insect are present and well developed. Find, pro-
ceeding from the front : —

1. A large, two-lobed labrum.

2. A pair of toothed, horny mandibles, covered by the
labrum.

3. A pair of maxilla, jointed, compound organs, each
bearing at its summit three appendages.

NEED. ZOOL. — 4

50 INSECTS.

(a) The lacinia (or blade), the innermost part, the part
used in biting.

(5) The galea, spoon-shaped, and covering the lacinia
externally.

(c) The maxillary palpus, a jointed, tactile organ out-
side. Count its joints.

4. A two-lobed labium (or lower lip), bearing below a
pair of jointed labial palpi.

5. A fleshy tongue, between and below the maxillae.
Separate these mouth parts, and examine each with a

lens. Draw.

II. Thoracic Segments. — Note the relative size of the
three thoracic segments. Note their peculiarities of form,
color, and surface markings. Locate their spiracles.

III. Wings. — Study the wings. Seize the fore wing
by its costal margin, draw it forward, and fasten it at
right angles to the body. Then in the same manner
draw the hind wing forward. Note how it is folded.
Compare the two wings in form, color, size, texture, posi-
tion, and use. The dry, horny fore wings of grass-
hoppers are called tegmina. Find in one of the tegmina
five principal veins, — costal, subcostal, median, sub-
median, and internal, — starting outward from its base.
Observe that each of the tegmina is marked off into three
areas, — the costal, median, and internal areas. The
median area lies between the subcostal and submedian
veins; the costal area, anterior to the median; the internal
area, posterior to it.

Make an enlarged and accurate drawing of a tegmen,
naming all the veins and areas upon the drawing.

It is by rubbing together the lower surfaces of the teg-
mina, and the upper surface of the costal vein of the
hind wing, that the males of this species produce the
sounds called stridulation, in flight. Examine these sur-
faces with a lens.

THE GRASSHOPPER. 51

IV. Legs. — Compare the first and second pairs of legs
with the third pair, in color and surface markings, posi-
tion, size, and use.

Find in one of the hind legs the usual segments, —
coxa, trochanter, femur, tibia, and tarsus. Note : —

1. The large club-shaped femur. Within it are the
powerful muscles used in leaping.

2. The double row of spines on the sides of the
tibia.

3. The two pairs of spurs at its lower end.

4. The tarsus. Examine its lower surface and the
hooks at its tip.

What is the advantage of all these spines and hooks
and pads ?

Make an enlarged drawing (lateral view) of one of the
hind legs in its natural resting position, naming all the
parts in the drawing.

V. The Abdomen. — Count the segments of the abdo-
men as seen on the ventral surface. In the female there
are eight, and in the male nine. The abdomen of the
female terminates in an ovipositor, having four subequal
points, which are used for making holes in the ground
for the reception of eggs. The four points are repeat-
edly pressed together, »pushed into the ground, and there
separated, thus pressing the earth aside, until a hole is
made of sufficient depth, when the eggs are deposited
in the bottom. An elongated, bilobed, subgenital plate
at the ventral surface terminates the abdomen of the
male.

Observe on either side of the abdomen a longitudinal
groove, and just above it a row of evident spiracles.

Observe on either side of the first abdominal segment a
semicircular depression, across which is stretched a thin
membrane. This is called the tympanum, and is supposed
to be an organ of hearing.

52 INSECTS.

Internal Anatomy. — Select for dissection large female
grasshoppers, the larger the better. On the Western
plains the lubber grasshopper (Brachystola magna), and
in the South the American locust (Schistocera americana),
will be obtainable, and will serve better than the Carolina
locust, because larger. Have specimens freshly killed in
the cyanide bottle.

Do not begin a dissection when tired or nervous, for
eager eyes and steady nerves are necessary to success.
Should you injure some one organ in the first dissection,
and so not see it satisfactorily, make a special dissection
to find it in another specimen.

Dissect the grasshopper on a shingle or bit of board.1
Place it back uppermost, and head from you. Spread the
wings, and pin them so. Pin the last segment of the
abdomen firmly to the shingle. With sharp, fine-pointed
scissors, make a shallow cut through the skin of the abdo-
men, from the ovipositor forward, keeping some distance
to the left of the median line, and continue the cut for-
ward to the head along the thorax at the bases of the
left wings. Then with forceps gently lift the right-hand
edge of the skin above the abdomen, and look beneath it
for a delicate, whitish vessel, the dorsal vessel, sometimes
improperly called the heart. It is but a series of thin-
walled chambers, into which the blood flows through
lateral valves, and through which it progresses forward
toward the head. You will find the colorless blood bath-
ing all the internal organs. A microscopic examination
of a drop of it will reveal its white corpuscles. The
dorsal vessel lies close to the roof of the abdomen, is very
liable to be injured in the opening of the skin, and may
sometimes be best approached by a dissection from the
ventral side. Make a second cut similar to the first,
on the right of the median dorsal line of the body, and
1 Or under water, if preferred. See Appendix, p. 283.

THE GRASSHOPPER. 53

carefully remove the roof of skin included between the
two cuts. Observe the thin, longitudinal muscle fibers
lining the roof of the abdomen, and the heavy wing mus-
cles completely filling the upper part of the thorax.

I. Tracheae and Ovaries. — Press the body walls lightly
outward, and observe the numerous white air tubes
(tracheae). Observe that the tracheae arise from the spira-
cles; that their larger branches unite to form longitudinal
passageways along the sides of the body; and that the
smaller branches ramify throughout the entire body, con-
veying air to all parts. Observe a loose, whitish mass of
these smaller branches now lying exposed in the abdomen,
on top of other organs. Place a small portion of this mass
in a drop of water on a slide. Cover it lightly with a
cover slip, and examine with low power to make out : —

1. The branching tracheal tubes.

2. The spiral elastic fiber which is coiled around the
wall of each to keep it open.

Two large and conspicuous yellow egg masses are usually
present in the abdomen of the female. These contain
many cylindrical eggs, piled like cord wood in ricks or
in tierlike masses. Separate the two masses by pushing
a dull instrument between them on the median line. Ob-
serve that each egg mass (ovary) has a white tube (an
oviduct) leading down to the ovipositor. Carefully re-
move the egg masses, and pin back securely both free
edges of the skin.

II. Organs of Digestion. — Study the digestive system.
The alimentary canal, dark-colored and conspicuous, will be
easily seen extending through the body lengthwise. Be-
ginning at the mouth, make out the parts of it, together
with the accessory organs, as follows : —

1. The mouth opens into an esophagus which extends
upward into the head, then backward into the thorax,
bending at right angles.

54 INSECTS.

2. The esophagus dilates posteriorly to form the inglu-
vies (or crop), a large food reservoir, and an important
organ of digestion. Its interior surface is furnished with
many ridges and conical processes which aid in commi-
nuting the food.

3. On the sides of the esophagus lie the delicate, white,
branching salivary glands. These communicate with the
mouth by means of two salivary ducts that run forward
along the sides of the esophagus.

4. The proventriculus (or gizzard) is the portion of the
food canal next succeeding the crop. Between the two
there is no separating constriction, such as there is in many
other insects. The proventriculus has thick, muscular
walls, also armed within for the comminution of food.

5. A circle of conspicuous appendages (the gastric cceca)
marks the posterior boundary of the proventriculus. These
are spindle-shaped appendages extending lengthwise of the
food canal, and attached laterally, having both ends free.
Each is, in fact, composed of two cone-shaped glands placed
base to base. The function of these glands is to secrete a
digestive fluid.

6. Posterior to these is the ventriculus (or stomach),
hardly distinguished by its external appearance in the
grasshopper from adjacent portions of the alimentary
canal.

7. At its posterior end arises a circle of long, slender,
inconspicuous tubes (the Malpighian vessels') which float
free in the body cavity. Their function is urinary.

8. The remainder of the alimentary canal is the intestine.
A study of the parts here disclosed will give a general
idea of the digestive system for all insects.

Let us now review the digestive process. The food is
first masticated by the mandibles and by the lacinise of the
maxillae in the mouth, is acted upon by the secretions of
the salivary glands as it passes from the mouth into the

THE GRASSHOPPER. 55

esophagus, is further comminuted and in part digested in
the crop and gizzard, is acted upon by the secretions of
the gastric caeca as it passes into the stomach, where diges-
tion is in the main completed. The digested food passes
out through the walls of the alimentary canal directly into
the blood, which bathes all the organs, and supplies them
with constructive material thus obtained from the food.
The Malpighian vessels reach out into the blood and
absorb from it noxious waste products of the body, which
they pass along out through the intestine, together with
the indigestible portion of the food. The blood gets
oxygen, necessary for both constructive and destructive
processes, by absorption of it (endosmosis) through the
tracheal walls.

III. Nervous System. — Remove carefully the alimen-
tary canal and its appendages, and look on the floor of the
body cavity for a double nerve cord extending the length
of the body, the two threads of it connecting on nearly
every segment with a double ganglion (a little, roundish
mass of nervous matter). Observe the nerve fibers that
radiate from each ganglion. These go to supply nerve
force to all parts of the body, and to supply nervous com-
munication between the parts. Trace the double nerve
cord to the head; then turn the head on one side, and pin
it firmly there through the front ; cut away the upper parts
until you discover a large ganglion situated above the be-
ginning of the esophagus, the cephalic ganglion (or brain) .
Observe that the double nerve cord begins here and passes
one thread around each side of the esophagus to the first
thoracic ganglion, and thence to the others of the system.

Development. — The development of the Carolina locust
may easily be traced, if the specimens of nymphs collected
alive are placed under a bell jar or glass dish, kept sup-
plied with fresh clover or lettuce leaves and water, and

56 INSECTS.

watched. With no more apparatus than this, specimens
may be reared from the egg to the adult condition. Since
this would require much time, it is better for the student
to get developing nymphs in as many sizes as possible, and
keep them long enough to see different molts gone through
with by different individuals.

Study the molting process, and by careful observations
get at the answers to such questions as the following : —

1. Has the nymph, when first hatched from the egg,
any wings? (Use lens in determining.)

2. Where does the nymph skin split open when molt-
ing occurs?

3. What part of the insect comes out first?

4. Does the insect have any difficulty in withdrawing
any parts of its body from the old skin?

5. What signs that molting is about to occur are dis-
coverable in the appearance or actions of the nymph?

6 What is the condition of the insect's exterior before
molting, and after?

7. What organs are relatively best developed and what
least developed in early stages, and for what organs has
the newly hatched nymph most use ?

Life-History Box. — Make a life-history box for the
Carolina locust. Get a neatly lined cigar box, and mount l
in it a complete series of specimens from egg to adult,
inclusive. The specimens should all be mounted on pins
stuck in thin sections of cork glued fast to the bottom
of the box. The eggs will need to be fastened with
mucilage to a bit of paper, through which the pin may
be thrust. The very smallest nymphs will need to be
mounted in the same way. The larger ones will have the
pins stuck vertically through the middle of the thorax. In
addition to nymphs of all sizes, exuviae should be mounted

i See note on mounting insects, in Appendix, p. 283.

THE SQUASH BUG. 57

separately. One or two nymphs should also be taken while
emerging from the exuviae, killed in the cyanide bottle, and
mounted in that condition. Then two adults of each sex
should be included, — one of each mounted with its wings
closed ; another, with wings fully spread. All the speci-
mens should stand two thirds of the way up the pins. Such
a box is easily prepared. It tells the story of the develop-
ment of the species. If the Carolina locust is not so
easily obtained in full series as another species, any other
grasshopper will do as well.

All the grasshoppers and locusts belong to the group
Orthoptera (or straight- winged insects).

Other Orthoptera are crickets, katydids, walking sticks,
mantes, cockroaches, etc. Some of these should be stud-
ied, and compared with the grasshoppers in size, in relative
development of organs, in relative powers of locomotion, in
food, in habits, in instincts, and in economic importance.
A good general idea of the group will thus be obtained.

THE SQUASH BUG.

(Anasa tristis.)

Haunts and Habits. — This insect is an annoying pest
of the kitchen garden. Adults, young, and eggs may all
be collected from the same vines of squash,
cucumber, or pumpkin. The adults are black-
ish brown above, and dirty yellow beneath.
The nymphs are smaller, and relatively shorter
and more rounded, than the adults. The eggs
are laid in little clusters on the young leaves.

No net will be needed for collecting these SQUASH BuG'
bugs. They may be pushed directly into the cyanide
bottle. While collecting, observe the following points.

58 INSECTS.

1. Their position on the leaf while feeding.

2. Their manner of feeding.

3. The effect of their operations on the leaf.

4. Under what conditions one leaf is ordinarily deserted
for another.

Study of a Live Specimen. — Study the adult.

Examine the head with a lens. Note the position of
its parts. Find eyes, ocelli, and antennae.

Observe that the mouth parts are modified into a jointed
proboscis (the rostrum). Count its joints. Note its posi-
tion. At the base of the rostrum above is the rudimen-
tary labrum. Mandibles and maxillae are represented by
two pairs of bristles within the sheath of the rostrum.
The sheath itself is supposed to be the modified labium
consolidated with its palpi. The whole rostrum is well
adapted to making punctures, and to sucking up through
them the juices of plants.

Observe for the thorax its shape and the relative de-
velopment of its segments.

On the mesosternum at either side, near each middle
coxa, find a small pore (an osteole) surrounded by a small
granular space (the evaporating surface). From these
osteoles is exuded the fluid Avhich gives the squash bug its
peculiar odor. This odor is protective, because it makes
the bug a less dainty morsel of food for other animals.

Examine the legs. For what kind of locomotion are
they adapted? Find coxa, trochanter, femur, tibia, and
tarsus. How many joints in the tarsus ?

Examine the wings. Observe carefully the difference
between inner and outer halves of the fore wing, the former
thickened and horny, the latter membranous and traversed
by numerous veins. Compare fore and hind wings in
form, size, texture, and position. Draw the wings of one
side (enlarged).

THE TWO-YEAR CICADA,

59

Make a life-history box for the squash bug.

The squash bug is a representative of the group Hemip-
tera (or half -winged insects).

Other Hemiptera. — All the " bugs," properly so called,
belong in the order Hemiptera, together with plant lice,
bark lice, tree hoppers, cicadas, etc. But two other types
will be selected here for study.

THE TWO-YEAR CICADA OR DOGDAY HARVEST FLY.

(Cicada tibicen.)

Haunts. — This is the insect commonly but improperly
called "locust." It may be found about shade trees in
late summer and autumn. Its col-
ors are black and green, powdered
with white beneath. The adults
may be followed by ear to their
resting places • on the boughs of
shade trees, their shrill cries being
the most prominent and the best
known of the various insect sounds
of late summer and of autumn.
The nymphs are seldom seen ; but
the exuvise which they shed at
their last molt are large, and con-
spicuous objects of common obser-
vation. They are found clinging
to weeds, bushes, trees, or fences in early summer. The
eggs are laid in slits made in the twigs of trees. When
hatched, the young drop to the ground and bury them-
selves, and feed upon the juices obtained by puncturing
the roots of trees. Two years are required to complete
their growth. The second summer following hatching,

TWO-YEAR CICADA.

60 INSECTS.

the nymph comes above ground, crawls a little way up a
convenient reed or board, fastens its feet firmly, and is
ready to transform. The skin splits down the back of
both head and thorax ; the perfect insect steps out, rests
awhile, and expands and dries its wings, and then flies
away with a noisy "whirr" to its new home in the tree
tops.

Study of a Live Specimen. — Get an adult specimen for
study, and observe : —

1. The shape of its body as a whole.

2. The point where the rostrum arises from the head.

3. The position of the eyes and ocelli.

4. The absence of any neck, and the consequent ap-
proximation of cheeks and coxae of the anterior pair of
legs.

5. The markings on the top of the thorax.

6. The sloping position of the wings.

7. The structure of the fore wings, — that they are not
half horny and half membranous, but wholly membranous.

8. The musical organs at the base of the abdomen
above (found only in the males), — two ribbed and plaited
parchment bags situated in depressions, one on either side
of the median dorsal line, provided with powerful muscles
for driving air against the fluted surfaces. This sets up
vibrations, producing sounds, which vary in different indi-
viduals with the proximity and form of the spaces and
ribs.

If the large rostrum of the cicada be dissected, the two
pairs of punctorial bristles will be easily found within the
sheath.

Compare adults of cicada and squash bug with refer-
ence to shape of head ; place of origin of rostrum ; length
of neck ; structure, position, and method of folding, of
wings.

THE BACK-SWIMMER. 61

Get an exuvia of a cicada, and study it carefully. Do
not fail to note how completely
the hard, external skeleton,
together with its internal pro-
jections, is shed. Compare it
with the adult in form and rela-
tive development of locomotive

organs. NYMPH OF HARVEST FLY.

THE BACK-SWIMMER.

(Notonecta.)

Haunts and Habits. — This insect is abundant in the
pools of brooks and in ponds. It is a little over half an
inch in length. It may readily be recognized by its in-
verted position in the water. It swims on its back, and
rests with its wing tips just touch-
ing the surface of the water, and its
long hind legs poised forward and ex-
tended on either side. When startled,
it darts away toward the bottom : but it
BACK-SWIMMER, NO- wiU rise again immediately when it stops

tonecta (slightly swimming-, unless it holds to some sub-
enlarged). , , ,

merged object; for its body, together
with the air inclosed beneath its wings and between its
thoracic segments, is much lighter than the water.

Back-swimmers are easily taken in a net. All stages
will be found together. They may be kept at home in a
bowl of water, and their habits studied. Care should
be exercised in handling them, for they will sometimes
inflict wounds with their sharp and strong rostrum.
When it is necessary to take one alive with the fingers, it
may safely be picked up by the sides of the body. Back-
ris present many interesting adaptations to aquatic

62 INSECTS.

life, and are especially worthy to be studied alive. Study
them so, either at home or in their native pools.

Study of a Live Specimen. — Observe : —

1. The boat-shaped body.

2. The oarlike position and action of the long hind legs.

3. The winy tips reaching the surface, and admitting
beneath the wings a supply of air, which may be breathed
when the insect is at the bottom.

4. The thin layer of air surrounding the thorax (easily
seen at the joints when the body is bended).

Place one on a dry surface : see it walk.

Throw an adult up into the air : see it fly. It can
arise in flight direct from the water.

Study the external features in order, as outlined for
other insects, noting especially : —

1. The junction of the head with the prothorax.

2. The position of the antennce.

3. The shape, size, and position of the eyes.

4. The absence of ocelli.

5. The sharp, lateral edges of thorax and abdomen.

6. The hairiness of parts.

7. The form, size, and position of the legs.

8. The structure of the tarsi (use a lens).

9. The structure and position of the wings.

10. The relation between the spiracles and the air
inclosed beneath the wings.

Then answer these questions : —

1. What advantages are secured to the back-swimmer
by the peculiar shape of its body?

2. Need locomotive organs be more complex for pro-
gression in the water, or on the land? Why?

3. What other devices for aquatic respiration have
you studied, and what points had each in common with
the respiratory method of this insect?

THE BUMBLEBEE. 63

THE BUMBLEBEE.

Haunts and Habits. — A field of blossoming clover, or a
fence row grown up with bergamot or other mints, is a good
place to observe something of the habits of the bumble-
bee, — to learn something of its part in the economy of
nature, which may not be so
well learned anywhere else. A
half hour spent in studying the
bumblebee among the flowers
from which it feeds may be
made most profitable. It will
not behave normally in confine-

.„ BUMBLEBEE (slightly enlarged) .

ment; but it will not resent

close scrutiny while free, and feeding from its favorite
flowers, if it be approached quietly. Watch a bumblebee
on a head of red clover. See how roughly it tramples
over the tops of the corollas. Observe that it collects
two products of the flowers : —

1. Nectar, from the bottom of the corolla tubes, which
it stops momentarily to sip as it passes over. Note the
position and shape of the organ used in sucking up the
nectar.

2. Pollen, the yellow dust which falls from the anthers
of the flowers when they are shaken. This is collected
into the pollen baskets on the hind legs. The yellowish
lumps of pollen will be conspicuous on some of the in-
dividuals seen.

Note whether the bumblebee visits one species of
flower, or several, in a single trip out from the nest. Fol-
low one from flower to flower, until you ascertain what is
its habit in respect to this.

What other insects have you studied that feed upon
red clover ? The life of quite a number of very common

64 INSECTS.

insects and other animals is more or less dependent on
red clover. The bumblebee is an animal 011 which the
life of red clover is more or less dependent. The bumble-
bee gives value received for all the nectar and pollen it
takes from the clover.

Clover must produce seed, or soon die out. The flower
must be fertilized in order to produce seed. The floAver
can be fertilized only by means of pollen carried to its
pistil from the anthers of another flower. The bumble-
bee is the carrier of the pollen. Its rough-and-tumble
manner of feeding is well adapted to dislodging the pol-
len, much of which falls on its body, and is scattered over
the flowers next visited, securing their fertilization. Thus
the insect's wasteful method of gathering the pollen is seen
to be exactly adapted to the requirements of the plant.

Spray a bumblebee with water, and note the effect on
its power of flight. What becomes of one when caught
out in a shower?

Compare a bumblebee with a butterfly in : —

1. Speed and directness of flight.

2. Relative size of body and wings.

3. Rapidity of wing strokes.

Catch a bumblebee in a net, and observe that the pitch
of its humming when captive is higher by several tones
than when free. Why? Collect with net and cyanide
bottle a few large specimens for use in studying its
anatomy.

External Anatomy of the Adult. — Study carefully to
make out the parts, as mentioned already for other insects.
The same parts are present, and in the same relative *posi-
tions, but modified to meet the needs of an animal of dif-
ferent life and different habits.

I. The Head. — Make a drawing of the head as seen
from above, showing accurately eyes, ocelli, and antennae.

THE BUMBLEBEE. 65

Study the mouth parts, observing another modification
and arrangement of them, as follows : —

1. A short, firm labrum.

2. A pair of strong, horny, biting mandibles.

3. A proboscis (or sucking organ), bent backward at
the middle, and resting against the lower surface of the
head and thorax when not in use, and composed of —

(a) A long, hairy, tubular ligula (or central piece) of
the labium (centrally).

(6) Two margined blades of the maxilla (above).

(<?) Two thin, narrow, elongated labial palpi (below).
Separate, and examine these parts with a lens. Draw.

II. Wings and Legs. — Compare fore and hind wings
in form, size, and position.

Draw the fore wing forward by its costal margin, and
observe that the hind one moves with it. Find the little
hooks (Jiamuli) which hold the two together, securing their
unity of action.

Find coxa, trochanter, femur, tibia, and tarsus in one
leg of each pair. How many segments in the tarsus ?
Which segment of the tarsus is largest? On which seg-
ment of the hindmost legs are the pollen baskets ? Ob-
serve with a lens the surfaces to which the pollen masses
adhere, and the means by which they are protected in
position. Make a detailed drawing of a hind leg.

III. Thorax and Abdomen. — Study the attachments of
both wings and legs of the hindmost pair, to ascertain
the posterior boundary of the thorax and the beginning
of the abdomen. Scrape off the hairs from the top of
the thorax, and observe that the metathorax is a narrow
segment (antero-posteriorly) ; and a wider segment with-
out appendages, the first abdominal segment, is solidly
welded to it. The second segment of the abdomen is but
a short and narrow stalk-like ring, attaching the ovate
hinder portion of the abdomen. Note how the abdominal

NEED. ZOOL. — 5

66 INSECTS.

segments are fitted together, and IIOAV great freedom of
movement is secured by this arrangement.

At the posterior end of the abdomen the slender point
of the sting may be seen protruding. Seize it with for-
ceps, and pull it out full length. Examine with low
power. Observe that it is hollow. Find the poison
glands at its base. The sting itself makes but a slight
puncture, which would hardly be noticed by the larger
animals were it not for the poison poured from these
glands into the wound. These, together with the great
mobility secured by the structure of the abdominal seg-
ments already noticed, make it a formidable weapon of
defense.

Development. — The development of the bumblebee may
be studied throughout in a single well-stocked nest. Find
a bumblebees' nest, and take it with all its occupants.
This will not be hard to do in summer or autumn. Two
methods are recommended : —

1. Having located the nest, go out for it after sunset or
before sunrise, when all its inhabitants are "indoors."
Pour chloroform or ether into the nest. Wait a moment
for the bees to become stupefied. Then take up the nest
entire, keeping the chloroform or ether at hand, ready to
be dashed into the nest should the first not have been
sufficient. But little of it will be required, if judi-
ciously administered. Care should be exercised, in taking
up the nest, to keep it in good shape for further study
of its structure and arrangement.

2. Another method, and one by which the nest may
be taken during the day, is the following : Set a clean
jug, uncorked and with some water in it, close by the
nest. Then disturb the nest (if possible, without injuring
its structure), and retire to a good place from which to
watch. The bumblebees will attack the jug, and then

THE BUMBLEBEE. 67

fly into it and get into the water, where they must
remain. When all have gone into the jug, or settled,
disturb the nest again. Repeat once or twice. Then all
those of the occupants which have been accustomed to
defend the nest will be in the jug ; and the few remaining
may be sprinkled with water, and picked up while wet
and unable to fly, or caught singly in a net. Obviously,
the entire population of the nest will not be caught in
this way, for in the daytime some are absent foraging in
the field. Why do the bumblebees go into the jug ?

Whatever the method of taking the nest, all its occu-
pants, as well as the nest itself, should be preserved for
future study. The bumblebees will not all be killed at
once by either of the methods suggested ; but they may
be killed in alcohol or in a cyanide bottle. Those taken
in a jug may be poured out with the water, and picked
up with forceps before their wings have dried.

Study the adult bumblebees found in the nest. Find
among them four sorts of individuals : —

1. Numerous small ones, built for activity, — the workers
(undeveloped females).

2. Others of larger size, but of the same general shape
as the workers, — the small females.

3. Others about the size of the small females, or some-
what larger, but thicker, clumsier, and more hairy, — the
males (or drones).

4. A few very large ones (an inch long), the large
females (or queens). Until late in the season, but one
of these will be found in each nest.

The Nest. — Study the nest. Note : —

1. The location of it.

2. The materials used in its construction.

3. The structure of it.
(a) The entrance to it.

68 INSECTS.

(6) The passageways inside.

(c) Its roof : will it shed water ?

(d) Its floor.

Within the nest find : —

1. Yellowish food masses of mixed pollen and honey,
containing —

(a) Small clusters of white, oblong, or elliptical eggs.

(5) The young which have hatched from other eggs, —
white, wormlike creatures of various sizes, feeding on the
pile of common food.

2. Cells: —

(a) Standing open, like yellow pots (or sometimes filled
and closed), containing stored honey.

(6) Capped over, and containing young.

Within the nest may often be found some of the smaller
insects, which are parasites of the bumblebee.

Life History. — Here in the nest is disclosed the life
history of the bumblebee. In its life there are four
stages.

The first stage is the egg.

The second stage is the wingless, footless, wormlike
creature which we call the larva. The larva is very
small when it emerges from the egg, but it grows rapidly,
for its sole business is eating; and. when it is fully grown,
it spins a silken cocoon about itself and enters upon the
next stage.

The third stage is the pupa. In the pupa stage it
remains quietly concealed within its cocoon, over which
the workers spread a thin layer of wax, making a cell
out of it. But though inactive, very important changes
are taking place in the pupa; for when, after a time, it
cuts a way for itself through the top of its cell, it comes
forth, not the wormlike larva which went in, but a fully
developed bumblebee.

THE BUMBLEBEE. 69

The fourth stage is the imago, the adult bumblebee.

Select one of the largest larvae for comparison with an
imago. Note their resemblances and their differences in
structure.

Open a number of the cells, and examine the pupse con-
tained in them. Observe the gradual evolution of the
perfected organs of the imago. Since the adult partakes
only of soft food, what use has it for horny, biting man-
dibles?

Make a series of drawings showing the life history of
the bumblebee.1

Compare the transformations of the bumblebee with
those of other insects studied. When, as with the bumble-
bee, there are four stages, — egg, larva, pupa, and imago, —
the metamorphosis is said to be complete. When, as with
the grasshopper, there are but three distinct stages, — egg,
nymph, and the perfect insect, — with no pupal or resting
stage and with greater likeness to the adult in the second
stage, the metamorphosis is said to be incomplete.

The History of a Colony of bumblebees, that is, of a
single nest and its occupants, is about as follows: In the
spring each colony is founded by one of the adult females
(or queens) which alone survive the winter. Such may
be seen in spring, searching the meadows over for a place
to establish a nest. When proper food flowers open, each
bumblebee takes possession of a suitable bunch of dried
grass, or preferably of an old mouse nest, and carries into
it pollen and honey, and deposits beside the food a few
eggs. All the work of providing food and shelter, and of
caring for this first brood, is done by the queen. The
bees of this first brood are workers, and as soon as they
come forth from their pupal cells they assume most of the

1 In its preparatory stages, the insect is best preserved in alcohol. Eor
a suggestion as to the use of alcohol, see Appendix, p. 277.

70 INSECTS.

duties of the colony, the queen continuing to lay eggs,
and the colony growing rapidly in numbers. In mid-
summer a brood is produced of small females and males.
The broods of autumn produce only large females (or
queens), and only these survive the winter. With the
coming of cold weather, all others perish.

A study of the life of a colony explains the scarcity of
bumblebees in spring and early summer. Considered in
connection with their fertilizing agency for red clover,
it explains the scarcity of seed in the first crop, and gives
a reason why the second crop (the late crop) is always the
one to be cut for seed.

The bumblebee is a representative of the group Hyme-
noptera (or membrane- winged insects).

Other Hymenoptera are ants, bees, hornets, wasps, saw-
flies, gallflies, etc. The three mentioned below are per-
haps most easily procurable.

THE MUD WASP (OR MUD DAUBER).

The Mud Wasp is a solitary hymenopter. The adult
female lives and labors alone. The nests may be found

in abundance, adhering to the
rafters in any barn loft or wood-
house attic, and are too familiar
to need description.

In very dry weather in summer
or autumn, the adults may be ob-
served by any brookside, at the
edge of the water, rolling up lit-
OUTLINE DRAWING AND DIA- tie balls of mud and flying away
GRAM OF A WASP (wings with them. The same operation

and legs of right side not _ , , . t n

shown): a, abdomen. niay often be seen beside a well

THE MUD WASP. 71

where water has been spilled, converting the dust into
mud. The peculiarities in the flight and walk of the wasp
may be studied in such places ; and specimens for study
may easily be taken with net and cyanide bottle.

Study the external anatomy of the adult, noting the
development of all the parts, and especially of the mouth
parts and the first three abdominal segments.

Study of a Live Specimen. — Go into loft or attic, or other
place where these insects are building their nests of mud,
and watch them at work. They will not sting unless
much molested, and they seem to have little objection to
being watched. Find one that is bringing in a ball of
mud, and follow it to its nest. Observe : —

1. How the ball of mud is carried.

2. How it is deposited and worked into place.

3. The peculiar sound the wasp makes while at work,
and how this sound is made.

4. The position and attachment of the nest.

5. The arrangement of its cells.

The nest may easily be removed, when the old wasp is
absent, by pushing a knife blade under it. Study the
development of the insect as shown in the contents of the
nest. Examine the contents of all the cells. Their walls
may easily be cut away with a knife. Find : —

1. A cell or cells unfinished, and containing at the bot-
tom a single egg.

2. Cells uncapped, and partly filled with little spiders
or other insects. These are for the food of the larva that
will hatch from the egg in the bottom of each cell. Note
the condition of the spiders, — not dead, but paralyzed.
A number of days elapse after they are put into the cell
before the larva is ready to eat them, and they would de-
compose if killed outright. The mother wasp stings them
in such a manner, that they are only paralyzed, and remain

72 INSECTS.

alive but inactive till wanted, — a wonderfully successful
way of providing her offspring with "fresh meat."

3. Cells in which there is a larva feeding on the spiders.

4. Cells in which the spiders have all been eaten (save
their skins, which are pushed to the bottom of the cell), and
in each of which there is a larva fully grown, or perhaps
transformed into a pupa, and lying quiescent within its
thin brown pupa skin.

5. Other cells showing a gradual approximation to the
adult form.

6. A cell from which an adult has just emerged, leav-
ing pupa skin and spider skins behind in the cell.

If all these stages be not found in a single nest, several
nests should be examined. Is the metamorphosis of the
mud was^omplete, or incomplete ?

THE PAPER WASP.

The Nest consists of a single tier of gray, papery cells
opening downward, and attached above by a short stalk to
the eaves of a building, or to a fence, or to the horizontal
twig of a small bush. This description ought to be suf-
ficient for identifying so common an object. The adult
wasps are always found upon the nest. It is an easy mat-
ter to obtain the nest, not so easy to get all the wasps.

Get a nest. It may be detached with a long pole.
When it falls, all the adult wasps leave it. Should it be
a large and heavy nest, located high above a hard surface,
some soft material, as straw, should be placed below it to
break its fall ; otherwise many of the cells will be injured.

Study the nest.

I. Construction. — Note the size, shape, and position of
its cells, and the attachment of its stalk. Draw.

II. Material. — Examine with a lens the paper of its
cells. It is made from fibers of wood torn from boards

THE HONEYBEE. 73

and splintered trees. The fibers are treated with salivary
secretions, and reduced to a pulp in the mouth of the
wasp. The pulp is then fashioned into cell wall, where
it quickly dries and hardens. How is paper made from
wood in paper factories ?
III. Contents :-

1. Is there any food stored in it?

2. Where is the egg placed in the empty cell?

3. Is the larva shut up with a store of food, or given
food as it needs it?

4. At what stage in the life of the young is its cell
capped over?

Study the metamorphosis, as before directed for the
mud wasp, and make a serial drawing showing its life
history.

THE HONEYBEE.

The Honeybee is the best known of the Hymenoptera.
It may be sought wherever there are flowers.

Make a study of its foraging habits and of its structure,
following the directions given for the bumblebee. Then
get a bee-keeper friend to show you through a movable-
frame hive in his apiary. Ask him to show you the sol-
itary female called queen, and the clumsy males called
drones. Ask him about the swarming habits. If. you
have not this privilege, then read in Quinby's " New Bee
Keeping," or Professor Cook's "Manual of the Apiary,"
the chapters on the natural history of the honeybee.

The Comb. — Examine a piece of empty honeycomb,
and note : —

1. The shape and arrangement of the cells on one side.

2. The meeting, at their bases, of cells on opposite sides
of the comb. What mechanical and economical advan-
tages do you discover in such construction? Does this

74 INSECTS.

indicate high or low rank in the insect's instinctive
endowments*?

Compare together all the Hymenoptera studied.

Which eat animal food? Which vegetable? Which both?

Which live in the largest colonies ?

Which show the highest instincts in the construction of
their nests ? In the care of their young ? In the division
of labor in the colony ?

Which are the best walkers? Which are swiftest of
flight?

Which are of most importance to man?

Compare as to the relative development of all the parts.

If the paper wasp bites wood, and the honeybee bites
nothing harder than wax, which should you expect would
have the stronger mandibles? Is it so in fact? Have
you discovered that there is a similarly close relation
between the structure of all organs and the work they
have to do?

THE BLACK BLISTER BEETLE.

(Epicauta.)

Haunts. — This beetle is very common in autumn, and
is very easily collectible. It will answer well for class
use, though a larger species, if avail-
able, might be more satisfactory for
a first examination. It is narrowly
oblong in outline, uniform jet black
in color, and is found on the flower
clusters of goldenrod, thorough-
wort, and ragweed, and not infre-
quently on the vines of potato,

tomato, and clematis. In some local-
BLACK BLISTER BEETLE . . , . , , , , ,

x 2. ities this beetle is replaced by re-

THE BLACK BLISTER BEETLE. 75

lated species, which resemble this one closely in size and
form, but which are variously striped. These afre all blister
beetles.

Blistering Property. — In collecting and studying them,
they should be handled with forceps and needles, and not
with the fingers ; for, when handled, there exudes from
the joints of the abdomen a yellowish fluid secretion con-
taining cantharidin, and possessing the power of blistering
the skin when coming in contact with it in sufficient
amount. This property is retained even when the insects
are dried, making them valuable to the apothecary.

Collecting. — A bottle is all the apparatus needed for
collecting this insect, — an empty bottle for live speci-
mens, or a cyanide bottle for dead ones. They may be
pushed from the flowers or leaves directly into the bottle
with its stopper.

Study the Live Insect. — Observe the nature and extent
of its injury to the plants on which it feeds. Has it any
competitors for the food these plants supply ?

Observe the action of its wings. Pick up with forceps
a live specimen by an antenna, and observe how it opens
and uses its wings. Put it down again, and observe how
it folds them up.

Study specimens from the cyanide bottle.

External Features. I. The Head. — Observe that the
head is narrowed behind, to form a sort of neck at its
junction with the prothorax.

Observe the size and position of eyes and ocelli.

Examine an antenna, and study its structure and
action. Draw.

Find in the mouth parts labrum, well-developed man-
dibles, maxilla3 with prominent palpi, and labium with

T6 INSECTS.

shorter palpi. Separate and draw. For what kind of
feeding is this mouth adapted ?

II. The Thorax. — Note the relative development of the
thoracic segments. Which is largest ? Observe the con-
tour of the surface of the thorax at the junction of the
legs and of the wings with the body. The cavities into
which the coxae are fitted are called the coxal cavities.
The coxal cavities of the fore legs are open behind; i.e.,
not surrounded posteriorly by the thoracic wall.

III. The Legs. — Examine the legs. Flex and extend
them, and observe the action of the joints. Find in each,
leg coxa, trochanter, femur, tibia, and tarsus. How many
segments in the fore and middle tarsi ? How many in
the hind tarsi ? Which segment of the hind tarsi is
largest ? Observe that the two claws of each tarsus are
cleft to their bases, and appear as four claws.

IV. The Wings. — Lift the chitinous sheaths (wing
covers or elytra) which meet by smooth edges along the
median dorsal line, completely covering the posterior part
of the body.

Extend them at right angles to the body, and examine
the wings. Observe how they lie folded. With forceps
seize a wing by its costal margin, and draw it forward.
Observe how it opens automatically when drawn forward.
Compare this method of folding with that already studied
in the grasshopper.

V. The Abdomen. — Study the abdomen. Compare
upper and lower surfaces. Count the segments. Com-
pare this abdomen in form and structure with that of the
Hymenoptera studied. Why has the beetle less need for
flexibility in this part than the bee ?

Development. — From July to October inclusive, the
eggs of the black blister beetle are laid in masses of more
than a hundred in shallow excavations in the soil. The

OTHEK BEETLES. 77

warm, sunny locations frequented by locusts are usually
chosen. The eggs are usually covered lightly with earth,
and are left to hatch.

The metamorphosis of blister beetles is very peculiar
and exceptional. An active larva (triungulin), with good
legs for getting about, is hatched from the egg. It runs
about, searching the ground over for a buried cluster of
locust or grasshopper eggs. At this stage it possesses
great powers of endurance, being able to live a fortnight
without food. If successful in finding an egg cluster, it
settles down, and begins to eat the eggs. After two molts,
it becomes a heavy, footless larva. After several additional
molts, and after attaining its growth, it quits the remains
of the egg cluster, goes deeper into the soil, and trans-
forms into a pupa. Later it emerges as the imago already
studied. For a full account of the transformations of this
and of other blister beetles, read the articles by Dr. C. V.
Riley, in Vol. XII. of the "American Naturalist."

If eggs of the blister beetle, and also the locust eggs
on which it feeds, can be found and suitably placed, all
the transformations may be seen taking place in the
course of a few weeks.

This insect is a representative of the group Coleoptera
(or sheath- winged insects). NO. i.

Other Beetles. — Perhaps no other beetle
is so easily obtainable in autumn, in supply
sufficient for class use, as the black blister
beetle ; yet, lest it should not be found
when wanted, cuts of four other common
beetles, which will answer equally well SOLDIER BEETLE

. , . . , (Chauliognathus).

for study here, are subjoined : —

No. 1 is a soldier beetle, closely resembling the black
blister beetle in structure, and frequenting the same
haunts. It is yellowish brown in color above, with a

78

INSECTS.

No.

large black spot on each elytron, and another on the
pronotuin. It is found on the flower clusters of many

Composite, and may confidently
be looked for on thoroughwort *
blossoms.

No. 2 is an elegant black
beetle, beautifully banded with
yellow. It is often found in
the clusters of goldenrod, or on
the leaves of locust trees, in
which it deposits its eggs.

No. 3 is a brick-red beetle,
with round, black spots. It is
found singly, or a very few to-
gether, on the leaves of the
LOCUST BORER BEETLE (slightly larger species of milkweeds.2

enlarged). ,T . .. , , ,

No. 4 is a smooth, black

beetle, with polished head and prothorax, and striated
elytra. It is often seen running about brick walks in

No. 4.

No. 3.

RED MILKWEED BEETLE,
Tetraopes (natural size).

HARPALUS BEETLE
(slightly enlarged) .

damp weather, and is nearly always to be found by over-
turning boards, logs, stones, etc.

Situations for Collecting. — Beetles are found every-
where, and are easily recognized by their elytra and

1 Eupatorium. 2Asclepias.

OTHER BEETLES. 79

biting mouth parts. A number of the common forms
should be studied and compared, in order to get a good
general idea of the group. A number of species, both
large and small, are attracted by a light at night. If a
strong light be placed in a window, they may be expected
on the screen outside, together with swarms of moths
and other insects. Beetles are very commonly found
under the bark of logs and stumps and in decaying
wood. They may be found along a railroad track, under
discarded "cross-ties" or "sleepers." Some gayly colored
little beetles are found on flowers; others are common
in shallow ponds, where they may easily be taken with
a net. These are among the most interesting and attrac-
tive of aquarium specimens. "Whirligig beetles" may
usually be found on the surface of still water, gyrating in
large companies.

Study a number of the most diverse forms obtainable,
following the outline given for the black blister beetle.
Then make a comparative study of the structure of all
the beetles collected.

Other common larval forms may be found, as " grubs "
and " wire worms " in the soil, and as " borers " in wood.
Some larvae may easily be dug with a strong knife from a
well-rotted log or stump.

Pupae will often be found in similar situations.

Test of Strength. — Select one of the stoutest-looking
live beetles to be found, and make this simple test of
its strength : Mold a saddle of stiff putty that will just
fit over its back without interfering with the action of
its legs. Hollow this out above, and pour shot into it.
Make the load all that the beetle can walk away with.
Then, with delicate scales, weigh the load, and also the
beetle. If a man weighing one hundred and fifty pounds
were as strong in proportion, how much could he carry ?

80 INSECTS.

THE BLUEBOTTLE FLY.

(Lucilia ccesar.)

Characteristics. — This is the loudly buzzing fly that
gets into our pantries and cellars. Its body, especially
its abdomen, is of a brilliant bluish-green color. It is
larger than the common house fly, and therefore better
for a first examination.

If a bit of fresh meat be exposed out of doors in warm
weather, in a very few minutes a number of these flies
will be attracted to it. They may be taken with a net.

Study of a Live Specimen. — Note the sound of their
buzzing in ordinary flight. Then catch one, and, being
careful not to disable it in any way,
hold it by the feet, leaving its wings
free. Note that the buzzing is in a
higher key. Then hold both wings
and legs so that neither can move,
and note that the sound still con-
tinues, and that the pitch is again
BLUEBOTTLE FLY raised. This last sound is probably
produced by vibrations set up in the
spiracles by manipulation of the currents of air.

Study its feeding habits. It is not shy : it will eat
freely from a bit of meat held with the fingers. Watch
it with a lens. Study the appearance and action of its
proboscis. Observe that it is somewhat two-jointed; that
the first joint is somewhat retractile into a cavity in the
base of the head; that the second joint folds up on the
first with a hingelike action when not in use; and that
the second joint ends in blunt expansion, which consists
of two flaps, that are separated in feeding, and applied to
the surface of the food.

THE BLUEBOTTLE FLY. 81

The action of these flaps may be studied under the
microscope. For this purpose the common house fly is
better, being smaller. Proceed as follows : Wet one side
of a large crystal of granulated sugar, place it on a slide,
and let it dry fast. Place the slide on the stand of the
microscope, blocking up one edge at a decided angle.
Focus on the crystal of sugar with the lowest power of
your instrument. Take your apparatus thus prepared
into a room, or other place where there are many hungry
flies, and wait for one to alight on the slide, and apply the
opened leaves or flaps of the end of its proboscis to the
sugar. Focus carefully, and record your observations on
the action of this part.

Examine a bluebottle fly that has been freshly killed
in a cyanide bottle.

External Anatomy. — Observe the general contour of
the body, the shortness of the abdomen, and the speciali-
zation of the thoracic region.

Note the shape of the head, the freedom of its movements,
the position and size of the eyes and ocelli.

Find the short antennae. Remove one, being careful
to get it off entire, and examine it with the microscope.
Find in it six segments, as follows: —

1. A small subquadrate first or basal segment, bear-
ing on one side, near its base, four conspicuous bristles.

2. A roundish second segment, bearing one stout,
straight bristle, and a number of smaller ones.

3. A large, oblong segment, much the largest in the
antenna, its surface sprinkled with minute pits and hairs.
This segment at first appears to be terminal, but it is in
fact much produced laterally.

4. Two minute segments, attached near the base of the
third segment, and forming a sort of pedicel for the ter-
minal segment.

NEED. ZOOL. — 6

82 INSECTS.

5. The terminal segment, which is expanded into a long,
feathery tip. Draw.

Mouth Parts. — The study of the mouth parts is not so
easy. The parts, being soft, are difficult of separation.
That they are all combined into a sort of proboscis has
been seen already. The sheath of this proboscis consists
of labium and labial palpi, grown together, and split down
the median line of the second joint of the proboscis in
front. At its tip are the two flaps already noticed. The
structure of this tip may be studied as follows: Kill a fly
in the cyanide bottle, and at once cut off its head. Place
the head flat on a slide, face upward, and apply pressure
to the center of the head with the point of a pencil. This
will cause the proboscis to expand fully. When so ex-
panded, apply a drop of turpentine and a cover glass to its
tip, and fasten the cover glass down with a clip before
removing pressure. The inner surfaces of the two flaps
will be fully exposed, and may be studied at leisure.
Observe the nearly parallel ridges on these surfaces.
Observe that they run transversely. Consider, then, that
the proboscis is moved backward and forward in feeding,
and you will see that the structure of these parts explains
their action, and that the rasping, back-and-forward motion
utilizes the rasping surfaces formed by these transverse
ridges. Draw.

Within the sheath of the proboscis there are two small,
elongated organs, one above the other, channeled along
their inner faces, making a tubular passage, through which
food is sucked into the pharvnx. Mandibles are wanting.
Maxillae are represented by rudimentary, one-jointed palpi,
which arise from near the middle of the basal joint of the
proboscis.

Thorax, Abdomen, and Appendages. — Observe the shape
of the thorax, and the extreme specialization of its middle

THE BLUEBOTTLE FLY. 83

segment. Remembering that the top of the thorax con-
tains the wing muscles, can you see any reason for the
specialization of the mesothorax, and for the suppression
of the other segments ?

Observe the shape, size, position, and texture of the
single pair of developed wings. Observe that these are
produced backwards at their bases in two short mem-
branes (the alulets). Draw.

On the sides, half concealed by the alulets, find a
pair of knobbed, threadlike appendages (the halteres, or
balancers). Observe that these spring from the narrow
inetathorax. They represent the second pair of wings.
Remove, examine with low power, and draw.

Observe the size and position of the legs. For what
kind of locomotion are they adapted ? Examine one with
a lens, to find the usual parts. How many segments in
the tarsus ? Observe the two claws at the end of the ter-
minal segment, and the pulvilli (or sucking disks) beneath
it. It is by means of these pulvilli that a fly walks up a
windowpane or across the ceiling. Count the segments
of the abdomen externally visible. Three terminal seg-
ments are withdrawn within the end of the abdomen, and
concealed like the small joints of a spyglass within the
large one. Search the sides of both thorax and abdomen
for spiracles.

Development. — The development of this insect can be
watched with less time and trouble than that of almost
any other; and, although its early environment is far from
being attractive, it teaches an important lesson in the
economy of nature. We cannot know the important place
this fly fills without knowing something of its larval life.
This is true of all insects.

The eggs of the bluebottle fly are laid on flesh, —
ordinarily on the carcasses of animals that have fallen

84 INSECTS.

in the woods and fields, — and the larvae hatched from
them are popularly known as maggots. These render great
service in the speedy removal of offensive substances.

The developmental changes may be studied without
discomfort, as follows: Expose out of doors a bit of lean
meat, so that the eggs may be laid upon it. Fill a flower-
pot or tin can or small box with sand, and on a chip
in the center of it place the bit of meat with the eggs
on it. Invert a tumbler over it, and push the rim of the
tumbler down into the sand. This will prevent the
escape of offensive odors, should such arise ; and the whole
can easily be arranged so that the developmental changes
may be witnessed through the glass. In a few hours the
eggs will hatch, and in a few days the larvae will be fully
grown. They will probably crawl beneath the chip or
into the sand, to transform into pupae. Upon the disap-
pearance of larvae, the oval pupae may be looked for. They
may transform speedily, or may continue as pupae through
the winter, according to the temperature and the season.

The bluebottle fly is a representative of the group Dip-
tera (or two-winged insects).

Other Diptera in general may be recognized by their
having but one pair of developed wings. They are always
and everywhere abundant except in winter. Many beau-
tiful and interesting species will be found about the
flowers of autumn. The following illustrative form is
recommended for further study here.

THE BEE KILLER.

(Asilus.)

Characteristics. — This is the dust-brown insect that
flits by our path in summer and autumn with such sud-
den and high-pitched sound of wings. This sound

THE BEE KILLER. 85

alone, once heard, is sufficient for recognition of the
insect. It is one of the largest and fiercest of our Dip-
tera. It is an inch or more
in length. It feeds princi-
pally on honeybees, pouncing
upon them with great swift-
ness while on the wing. It
frequents dry pastures where
bees are feeding. It is often-
est seen when startled from
its resting place upon a stick
or stone beside our path. It

.. .. BEE KILLER, Asilus (natural size).

may be captured by dexterous

use of the net. It should be introduced into the cyanide
bottle without handling, for its beak is powerful enough
to wound the fingers.

Study of Live Specimens. — Having flushed a bee killer
from its resting place, it may be followed at a proper
distance, and something may be seen of its predaceous
habits. Take time, while in the field collecting, to ob-
serve : —

1. The character of its flight as to speed, directness, etc.

2. The length of time spent on the wing at one flight.

3. The course of its flight. After one of its swift sal-
lies, does it usually return to the same resting place from
which it started out, or to a new one ?

4. The purpose of its flight. Does it seem to be intent
on catching a bee at every flight, or does it sometimes
seem to fly for sport?

5. Its feeding habits. Try to see one catch a bee and
carry it away to be eaten. Wait quietly by until the
bee killer has finished its repast ; then go and look for
the remains of the bee. What part is left? Search the
spots from which other bee killers are flushed, for the re-

86 INSECTS.

mains of other bees. In this way 3-011 will get an idea of the
extent of its depredations on the population of the hive.

Capture a few good specimens to be used in studying
the external peculiarities. Note specially the length of
the abdomen, the strength of the beak, the size and rough-
ness of the legs, and the position, size, and strength of the
wings. Make drawings of antennee, mouth parts, legs,
wings, halteres, etc., and compare with those of the blue-
bottle fly.

THE CABBAGE BUTTERFLY.

(Pieris rapce.)

This is the small white butterfly with black wing tips,
too abundant about our gardens. Something of its habits

will have been seen already,
for it is commonly found
feeding with the sulphur
butterfly. Collect now a
number of specimens to be
used in studying it.

External Anatomy. —

FEMALE CABBAGE BUTTERFLY, Pieris Follow the plan of study
rapK (from Riley). . . r /

laid down in the " Prelimi-
nary Lesson" for the sulphur butterfly. When studying
the mouth parts, note that the coiled organ, which has
been called the tongue, consists of two elongated organs,
grooved on their inner edges, and placed side by side, so
that the grooves meet, and form a tubular food passage
between them, and that these two organs are, in fact,
the much modified lacinia of maxillae.

A few convenient descriptive terms applying to the
wings need to be learned here. The wings, being some-
what triangular in outline, present three margins and
three angles. The anterior margin is called the costal

THE CABBAGE BUTTERFLY. 87

margin, or more commonly the costa; the margin farthest
from the body is called the outer margin; the other mar-
gin is called, on the fore wings the hind margin, on the
hind wings the internal margin. The angle by which the
wing joins the body is called the base; the angle between
the costal and outer margins is called the apex; the
other angle is called the posterior angle on the fore wings,
the anal angle on the hind wings. The branches of the
subcostal vein are called the subcostal veinules, and like-
wise those of the median vein are called median veinules;
and both are numbered first, second, third, etc., from the
front. On the basal half of each wing, between the sub-
costal and median veins, is an obovate inclosure, called
the discal cell, or more often simply the cell. The space
outside this, occupied by the terminal veinules, is called
the discal space, or often simply the disk. Extending
across the ftisk from the cell to the outer margin of the
wing is a short, straight vein situated about halfway be-
tween the subcostal and median veins, but appearing not to
be a branch of either, and hence called the independent vein.1

1 The names of veins here given are those found in nearly all our
descriptive works on butterflies and moths. There has been little uni-
formity hitherto in the names used by writers in the different groups,
each of the principal groups having developed a nomenclature of its own.
Professor Comstock has proposed for the veins of the wings of all insects
a uniform nomenclature which seems likely to be adopted. Applying
this system to butterflies and moths (Lepidoptera) , the principal veins are
as follows : —

Costa. — On the costal edge of the wing.

Subcosta. — Improperly called the costa by writers on the Lepidoptera.

Radius.' — Improperly called the subcosta by writers on the Lepidoptera.

Media. — The base of this vein is wanting, and its branches are joined
to adjacent veins. It is three-branched. Its middle branch is the so-called
independent vein.

Citbitus. — This vein is two-branched, but appears to be three-branched
in most butterflies, as the third branch of media is joined to it.

Anal Veins. — There may be one, two, or three of these. In most
butterflies there is one anal vein in the fore wing, and there are two in
the hind wings.

Costa, subcosta, and the anal veins are simple in all Lepidoptera.

88

INSECTS.

Make an enlarged drawing of both wings of one side,
naming all these parts on the drawing.

Development. — In almost any cabbage patch during
summer and autumn this insect may be found in all
stages of development. Collect and observe : —

1. Eggs. These will be found attached singly, usually
to the lower surfaces of cabbage leaves. They are quite
minute, and are pale yellowish in color.
They should be taken with the leaves
to which they are attached, and not
removed from the leaves until they
are to be studied.

2. Larvce. These are found most
abundantly on the fresh but slightly
expanded leaves and on both surfaces.
Some will be found feeding, others
resting. All sizes will be found com-
mingled.

Lift one that is resting, from the
leaf, to observe the layer of silk in
which its feet are entangled. This silk is spun from a
spinneret (modified labrum) below the mouth. A small
larva may sometimes be seen actively, and even somewhat
violently, swinging its head from side to side as it lays
down this layer of silk, thread by thread.

Watch a large larva that is feeding, to see how methodi-
cal is its habit.

How does a larva walk? Can it walk more easily on
the side, or on the margin, of a leaf ?

Observe the nature and extent of the injury done to
the cabbages by these larvae.

Observe later their hours of feeding.
Observe whether they are found in the same positions
on sunshiny as on cloudy days.

LARVA AND PUPA OF
CABBAGB BUTTER-
FLY (from Riley).

THE CABBAGE BUTTERFLY. 89

Observe the effect on them of wet weather and of dry ;
of hot weather and of cold.

Collect larvae of all sizes, and keep them supplied with
cabbage leaves until wanted for further examination.

3. Pupce or chrysalides. These have an angular, chi-
tinous case, something less than an inch long, and pale
and inconspicuous. One will occasionally be found at-
tached to a cabbage leaf, but more often to the under side
of a fence board, or to a post some few yards distant from
the cabbages. There is little or no attempt at conceal-
ment; but, if one be 'not found readily, it may easily be
obtained in a few days by keeping in confinement a few
full-grown larvae, and this will afford opportunity for ob-
serving the transformation. For this purpose a few of
the largest larvae (they should be more than an inch long)
may be placed in an ordinary jelly glass, with pieces of
fresh cabbage leaves, covered with the tin top to prevent
the drying-up of the leaves, and left there until the trans-
formation takes place.

When a chrysalis has been obtained, note its location
and attachments. At its posterior end is a circlet of
hooks, called a cremaster, fastened firmly into a button
of silk that was spun by the larva. Around its thoracic
region is a supporting loop of silk attached at both ends
to the support above. How does a thing so inert become
suspended in such a peculiar fashion ?

4. Imagoes. These should be obtained from the chry-
salides. All that is' necessary is the keeping of the chry-
salides in a moderately warm place, and in a good place
for observation, for a short time. This will be advan-
tageous on two accounts : (1) it will afford an opportunity
for observing the final transformation, — the rupture of the
chrysalis, the emergence of the imago, and the expansion
and drying of its wings, — a truly wonderful transforma-
tion, that ought to be seen by every one ; and (2) it will

90 INSECTS.

afford an opportunity for seeing something of the effects
of certain parasites of the cabbage butterfly, chief among
which is a little black ichneumon fly. This fly lays its eggs
in punctures in the skin of the larva. The eggs hatch out
little fly larvae, which feed upon the vitals of the butterfly
larva. The latter, if not killed by these parasites before
attaining its growth, becomes a chrysalis, inside which the
fly larvae continue their growth and transformations.
Finally there issues from the chrysalis, not a butterfly,
but a swarm of little black ichneumon flies. If half a
dozen chrysalides be kept, an infested one, or several, will
probably be found. If a chrysalis looks much blacker
than the others, it is surely infested; and, if placed in a
small vial, the ichneumon flies may be caught when they
issue forth.

Immature Stages. — Study the three preparatory stages.
I. The Egg. — Study the egg to make out : —

1. Its attachment to the leaf.

2. Its shape.

3. Its surface markings.

II. The Larva. — Study the larva. Observe : —

1. The plainly distinguishable head.

2. The cylindrical body, without distinguishable thorax
and abdomen. Count the segments.

3. Three pairs of true legs on the first three body seg-
ments. These mark the portion of the body which is
later to become the thorax.

4. Five pairs of false legs, called prolegs (abbreviated
from " prop legs "), borne on the sixth, seventh, eighth,
ninth, and last body segments. -

5. Spiracles, a pair on each of the body segments ex-
cept the second, third, and the last two, opening at the
sides. The absence of spiracles on the second and third
segments marks these as the ones which are to bear the

THE CABBAGE BUTTERFLY. 91

wings. Powerful wing muscles are to be developed
within them.

Kill a large larva by placing a drop of chloroform upon
its head, or by any other convenient method, and with a
good lens examine : —

1. Its head, as seen from
the front and from be-
neath. Make out : —

(a) Ocelli situated on

the front of the lateral DIAGRAM OF LARVA (x 2): e, simple

prominences of the head. fes. ?n, ^ f™nt °f*a£ hfd;

* I, ]omted legs attached to the three

How many, and how ar- thoracic segments; sp, spiracle

ranged? openings; pr, prolegs.

(5) A labrum, a little flap of membrane above the mouth.

(c) A pair of rather prominent biting mandibles which
meet by serrated edges.

(d) On either side of these a very rudimentary stump
of an antenna, here found situated lower on the head than
in the perfect insect.

(e) Below the mandibles, a pair of very rudimentary
maxillce. They are but fleshy prominences here, made
recognizable by a pair of minute appendages (palpi) at
the tip of each.

(/) Between and below the maxillae is the larger la-
brum with its very minute rudiments of palpi, and a
median appendage of special structure (a slender horny
tube, which serves as a spinneret) . Through it is exuded,
from glands in the head, a liquid, which dries, immediately
on exposure to the air, into the silken thread which the
larva spins over the leaves.

Compare this mouth with that of an adult.

2. The covering of the skin. What kind of out-
growths can you find with a lens ?

3. Its thoracic legs. Make out : —
(a) That they are jointed.

92 INSECTS.

(5) That they end in a horny, hook -like tip.
4. Its prolegs. Make out : —

(a) That they are more membranous.

(6) That they end in a circlet of minute hooks exactly
adapted for catching into a layer of silken threads, and
probably more serviceable to the caterpillar than are its
true legs.

Compare this locomotor apparatus with that of an adult.
III. The Pupa. — Study the chrysalis. Observe : —

1. The consolidation of head and thorax.

2. The relative freedom of the abdomen and its capacity
for a slight twisting motion.

3. The shape and surface markings of the chrysalis, and
the structure of the cremaster, in which the abdomen
terminates.

4. The chitinous sheaths or cases of the appendages of
the body overlapping on the ventral surface. The cen-
tral ridge is that formed by the tongue case. Those next
on either side of it cover the first pair of legs. The next
cover the second pair of legs. The next are the antennae
cases. The next and largest are the wing cases. The
third pair of legs is concealed beneath the wing cases.
When the chrysalis is first formed, these parts are soft and
easily separable, but they become very solidly coherent
in an old chrysalis.

5. The spiracles of the abdomen in their normal posi-
tion. The one on the first thoracic segment has been
crowded backward until it appears between the first and
second segments.

From a comparison of larva and imago, it becomes evi-
dent that the quiescent pupal period is the period of
greatest developmental changes. It should be noted, how-
ever, that these changes have been begun in the larva;
that the insect begins its pupal period in possession of
the rudiments of its perfect organs.

THE LIFE PROCESS IN INSECTS. 93

It should be noted also, in comparison of larva and imago,
that there is an entire change of life habits and of instincts.
That there is no traceable connection between the instincts
of the larva and those of the adult, is an interesting fact.

PUPA (x 3) : h, head; e, eye case; th, thorax; ant, antenna case; tc, tongue
case; Ic, cases of front and middle legs; we, wing cases; sp, spiracles;
a, abdomen ; cr, cremaster.

Butterflies and moths constitute the group Lepidoptera
(or scaly-winged insects). Capture a few of the moths
that are attracted to a light at night, and examine them,
to discover wherein moths differ from butterflies.

THE LIFE PROCESS IN INSECTS.

I. Nutrition. — The food of insects is so various, that
diverse organs are necessary for seizing and preparing it
for digestion. The mouth parts normally present are
(1) a labrum; (2) a pair of mandibles; (3) a pair of max-
illae, each with three free appendages, — lacinia, galea,
and palpus ; and (4) a labium, with its jointed palpi.
Any of these parts may be specialized, modified, or sup-
pressed, according to the needs of the animal.

94 INSECTS.

The seizure of food is effected by some or all of these
parts, assisted in a few cases by armed fore legs. Masti-
cation, when necessary, is effected by the mandibles and
lacinise of the maxillae

Two types of insect mouths may be noted, adapted
respectively (1) for sucking and (2) for biting. Sucto-
rial mouths are widely different in structure, some being
armed for making punctures, others wholly unarmed. In
some insects with suctorial mouths, the pharynx (some-
times other parts of the alimentary canal) is provided
with muscles, and capable of distention, and, thus modified,
it becomes a pumping organ.

Digestion is effected jby the crop (when present), gizzard,
and stomach, aided by secretions from the salivary glands
and gastric caeca.

Circulation is effected at first by the passage of the
digested food through the walls of the alimentary canal,
out into the blood. The blood bathes all the internal
organs, taking to each the material needed for cell con-
struction. It courses posteriorly through the body cavity,
enters the dorsal vessel by lateral valves, is propelled
forward, and passes out toward the head through the
single rudimentary artery.

Respiration is effected either by spiracles or by tracheal
gills. The former are adapted for aerial, the latter for
aquatic, respiration. Spiracles are situated on the sides
of the body, and open into tracheae, which unite into
longitudinal lateral trunks, and send their numerous
branches to every vascular part of the body. Some
aquatic insects have aerial respiration ; i.e., they obtain
their air supply from above the surface of the water.
In these the spiracles usually open beneath the wings,
where air is stored that has been obtained at the surface
and carried down below.

Tracheal gills are adapted for breathing the air that

THE LIFE PROCESS IN INSECTS. 95

is mixed with the water, or held in solution. These are
delicate expansions of the body wall, and contain trachese,
which divide and subdivide until the smallest branches
are separated from the water only by exceedingly thin
membrane. Through this the air in the tracheae effects
exchange of gases with the air in the water outside, and
is thus purified and fitted for respiration. Tracheal gills
are usually situated on the abdomen, and must, of course,
project into the water.

By either of these means, oxygen from the air is sup-
plied to all parts of the body; and that is the essential
thing in respiration.

Assimilation of food is the business of each individual
cell. As no division of labor in society can relieve any
person of the necessity of eating, sleeping, and taking
exercise, so no physiological division of labor can exempt
any living cell in the body from the necessity of taking
from the blood supplied the material necessary for its
own growth. Each individual cell of the insect must,
like the one cell of the amoeba, absorb and assimilate food
and excrete worn-out material for itself.

It is oxygen that puts the body material in shape for
excretion. The food of animals, being organic, is made
up of complex chemical compounds, of which carbon and
hydrogen are abundant elements. Oxygen, in combining
with these elements, forms simple compounds, and breaks
up the complex ones, liberating their potential energy in
the form of various physical and vital forces, — heat,
electricity, nerve force, etc.

The commonest products of oxidation are carbonic-
acid gas and water. These have to be removed from
the body.

Excretion is the name of the process, and it is effected
by various organs. Such gaseous molecules as escape into
the minute air tubes may be exhaled through the tracheae.

96 INSECTS.

Such as get into the blood may be removed through the
secreting action of the Malpighian vessels, or may escape
by osmosis directly through the walls of the alimentary
canal.

II. Reproduction. — All insects are dioecious; i.e., the
sexes are distinct. Paired generative organs are found in
the abdomen beneath the dorsal vessel.

Nearly all insects are produced from eggs. For the
few remarkable exceptions, and for the presentation of
the interesting questions connected therewith, the student
is referred to the larger works on entomology.

Of the metamorphoses of insects there are two general
types: 1. When incomplete, there emerges from the egg
a nymph, which differs from the adult principally in size,
and which, when grown, transforms directly into a perfect
insect ; 2. When complete, the egg produces a larva,
usually a little wormlike creature with little external
likeness to its parents. This, when grown, transforms
into a pupa, which, after a quiescent period, again trans-
forms when an imago issues.

It must be borne in mind that a few transformations
will not conform strictly to either of these types, also
that there is no difference in kind between the two types.
Convenience is the best reason for naming the growing
stage of the one nymph, and of the other, larva.

It must be observed that the growth of the insect is
completed during the larval or nymph stage. Eating is
the sole business of nymph or larva. But of adults, some
do not eat at all, and those that eat to keep alive do not
grow. To reproduce their kind, to fulfill their part in
Borne one of nature's little groups of diverse forms of life,
and perhaps to enjoy their brief existence, seem to be
their mission.

It will be noticed, that of the inhabitants of field, forest,

THE LIFE PROCESS IN INSECTS. 97

garden, and orchard, popularly called worms, the great
majority are not worms at all, but the larvse of winged
insects. The student needs to be reminded here, that
little or nothing is known of the preparatory stages of
many of our native insects, and that in consequence
neither their place in nature, nor their importance to man,
can be rightly understood and appreciated.

III. Voluntary Motion. — The muscular system of in-
sects consists, for the most part, of isolated muscular
fibers, attached to prominences on the inside of its hollow,
chitiiious skeleton. Those fibers which move the body
segments are seen, upon dissection, arranged in whitish
bands along the sides of the body cavity. The strong
wing muscles fill the top of the thorax. Some of the
fibers that move the appendages of the body are attached
to tendons.

The usual movable appendages of the insect body are
antennse, mouth parts, legs, and wings. The adaptations
of legs and wings to the habits of their possessors are not
less striking than those of mouth parts. Insects have
been studied which have legs adapted by their size, position,
and arrangement, for standing, for walking, for running,
for jumping, for swimming, and for seizing prey. The
most striking modifications of wings are the very common
ones already studied, — the tegmina of Orthoptera, the
fore wings of many of the Hemiptera, and the halteres of
Diptera.

But no account of muscles and motive organs will con-
vey any adequate notion of insect activity. This needs
to be seen to be appreciated ; and half an hour spent in
the open field on a warm afternoon, " amid hurrying
wings and scurrying feet," in careful observation of the
doings of these tiny creatures, will be of profit in learning
a few of the valuable lessons that cannot be put into

NEED. ZOOL. — 7

98 INSECTS.

books. The athletic powers of a few insects, the student
has had an opportunity to test for himself. When size is
taken into account, it is probable that the champion ath-
letes of the world will be found to be insects, at least in
running, jumping, and flying.

IV. Sensation. — The nervous system consists of a
double chain of ganglia, extended lengthwise on the
floor of .the body cavity, and connected anteriorly with
a large cerebral ganglion in the head by a nerve each
side of the gullet. From the cephalic ganglion or brain,
nerves go to the eyes and other parts of the head, while
each segment of the body is supplied with nerve fibers
from a subjacent ganglion.

The five senses known to us are probably possessed by
all insects. The sense of touch, while common to most
parts of the body, is somewhat specialized in antennse,
palpi, and various tactile hairs. Organs of sight have
reached a wonderful development in the compound eyes.
We have no means of knowing what may be the limits of
the power of vision in such organs. The sense of smell
(or some other to us unknown sense) is undoubtedly
present, enabling insects to find hidden food. Certain
microscopic structures in the antennse are believed to be
organs of smell. No undoubted organs of hearing are
yet known; but it is probable that insects can hear, for
many of them possess elaborate sound-producing appara-
tus. Supposed organs of taste have been found in the
labium and lower side of maxillae.

The instincts 1 of insects are the subject of many books.
They are shown in manifold ways, and in no two species
of insects in precisely the same way. They are too
diverse to admit of summarizing here. But the instincts

1 "An instinct is a propensity prior to experience, and independent of
instruction." — PA LEY.

A REVIEW EXERCISE. 99

perhaps most commonly noted are those which guide to
proper methods of seeking security from enemies, to the
selection of proper places for depositing eggs, and to the
construction of nests in which to properly provide for
their young. The hunted moth, alighting on a leaf of
her own color, and remaining motionless, concealed; the
aerial dragon fly, immersing her eggs beneath the water ;
the butterfly, depositing her eggs upon the leaves of a
plant which has furnished her, as an adult, no food ; the
wasp, making cells of mud, and stocking them with
paralyzed spiders ; and the bee, constructing her math-
ematical cell, and feeding daily by hand her growing
young, — all are but the commonest illustrations of a
faculty which culminates in the social order of some ant
communities.

A REVIEW EXERCISE.

1. Which of the insects studied have mouth parts
adapted for biting? For sucking? Which of the latter
have mouth parts armed for puncturing, as well as adapted
for sucking ? Which have the mouth parts adapted for
both biting and sucking ?

2. What mouth parts are specialized in seven of the
insects studied (one from each group), and what is the
advantage to the insect of such specialization? What is
the food of each ?

3. Which of the insects studied breathe by spiracles?
Which of these are aquatic ? Which breathe by tracheal
gills?

4. Give examples of insects having legs adapted (1) for
standing, (2) for walking, (3) for running, (4) for leap-
ing, (5) for swimming, and (6) for seizing prey.

5. Bring together the drawings that have been made
of legs, of wings, of mouth parts, and of antennae, and,

100 INSECTS.

placing like parts together, study them comparatively, to
note the diverse modifications of parts that are homologous.

6. Bring together, for comparative study, the drawings
that have been made of entire insects, and note which
body segments are specialized in each. Dissection of these
insects would have revealed a corresponding diversity in
the development of the internal organs ; and the study of
all shows one plan of structure, with great variety in the
details of its execution.

7. Study the drawings to ascertain whether the modifi-
cations of wings and legs, and other organs, is always in
harmony with the habits of the insect. Does the insect do
with its locomotive appendages just what they seem fitted
for doing ? Could you not tell, by looking at an unknown
insect, whether it spends the greater part of its time
afoot, or a-flying?

'8. Special organs of touch (antennae and palpi), and
special organs of sight (eyes and ocelli), are evident in the
insects studied. In the adult dragon fly, the eyes are
specialized, and the touch organs reduced. Which of
these two senses is probably more serviceable to the
dragon fly, and why? Why are the eyes reduced, and
the tactile organs specialized, in some beetles ?

9. Take some unfamiliar insect collected and killed by
another person, and after studying carefully the devel-
opment of its parts, and their probable uses, write out
some inferences — not guesses, but inferences from facts
of structure observed — as to the habits of the insect,
particularly as to its habits of feeding and of locomo-
tion. Then compare your inferences with the facts as
you can learn them from later observations, on the insect
alive, or from reading.

10. Compare the wings of a grasshopper, bug, and bee-
tle. Observe that in the first two the fore wings are pro-
tective coverings, as well as organs of flight. And do not

A LESSON IN CLASSIFICATION. 101

fail to note, that, just in proportion as they become service-
able for protection, they become useless for flight. This
is a good illustration of the universal law, that precise
adaptation to one thing brings limitations in other things.
Observe, also, that with the decrease in usefulness of
the fore wings, there is an increase in size of the hind
wings, — that the hind wings become disproportionately
large, and have to be folded when at rest. Compare their
several methods of folding.

11. Which of the insects studied have complete, which
incomplete, metamorphoses ?

12. Which are injurious to vegetation, and during what
stage of metamorphosis are they most injurious ? Which
are directly beneficial to man?

13. Which eat different food in different stages of life ?

14. Which are most musical (or noisy, if you please),
and by what means do such produce their sounds ?

15. Mention examples of the dependence of insects
upon mimicry for protection. Which of the insects
studied show the highest instincts in the care of their
young? In the construction of their nests?

A LESSON IN CLASSIFICATION.1

Have a good supply of butterfly specimens on hand,
before beginning the following work; the more different
kinds, the better.

1 This lesson outlines a simple and natural introductory method which
has proved very serviceable. First steps in classification may be illus-
trated with other insects as well as with butterflies, perhaps better with
some others. The teacher will probably find 'this method most service-
able when applied in the group with which he is best acquainted. In
applying the method to butterflies, the groups as laid out in the works
most commonly found in school libraries have been recognized here as
sufficiently answering the purpose of this lesson. Recent changes and
improvements in the classification of butterflies may be introduced when
they have made their way into available literature-

102 INSECTS.

The Species. — Select two of the large swallow-tail but-
terflies (the large black ones with tailed hind wings) that
differ plainly in coloration, markings, outline, etc. These
are two different species. Find out all you can about the
two species, first by studying them, and afterward by read-
ing about them (you will find them described in French's
44 Butterflies of the Eastern United States"), and note
the kind of differences between them : —

1. Differences of color and markings throughout all
stages, — very obvious differences, but not alone sufficient
for distinguishing species, for color is a very variable and
somewhat unreliable characteristic.

2. Slight differences in outline, in external ornamenta-
tion, etc.

3. Differences in size.

4. Differences in habits.

5. Differences in food of larvse.

6. Differences in egg, larval, and pupal periods, etc.
Such minor differences as these are the ones commonly

used for distinguishing species. Make a list of the points
that distinguish the two species selected.

Get the two common kinds of cabbage butterflies. The
most prominent mark, within the border of the fore wings,
is in one a black spot, and in the other a black dash.
Compare these, and observe that the differences are of the
same kind as before. These are two species.

The Genus. — Now compare a swallow-tail with a cab-
bage butterfly. Note that while the two are alike in the
possession of relatively broad wings and slender bodies,
and in having six fully developed feet, their differences
are yet greater than those which distinguish species.
Note the differences : —

1. In the shape of the hind wings.

2. In their position in relation to the abdomen.

A LESSON IN CLASSIFICATION. 103

3. In the structure of the second segment of the body
of the larvae, etc.

Such differences are used to distinguish genera. The
swallow-tails belong to one genus, the genus Papilio ; and
the cabbage butterflies to another, to the genus Pieris.
Make a list of the characters which distinguish these two
genera.

Every species has two names, — the name of the genus
to which it belongs, and its own specific name. A man has
two names, — a surname and a given name. The surname
corresponds to the name of the genus ; the other, to the
name of the species. Just as there may be several John-
sons (John, Henry, and Eleazar), so there may be several
Papilios, — Papilio asterias, Papilio troilus, Papilio turnus,
etc. The surname serves to locate the man among the
Johnsons ; the generic name Papilio locates the butterfly
among the swallow-tails. And just as the name John
tells which Johnson is meant, so the name asterias tells
which Papilio is meant. Observe that the names are
written, as men's names are written in a directory, sur-
name first. Which species of the genus Papilio have you
had for comparison ?

The Family. — Get, for comparison with these, one of
the small, thick-set, swift-flying "skipper" butterflies,
which rest with wings thrown backward until the costal
margins of the two pairs are side by side. Compare and
observe the marked difference in form, — a difference
of the kind used to distinguish families. This skipper
butterfly is not only of a distinct species and genus, but
its diverse form shows a relationship still more remote.
It is of a different family, the family Ifesperidce. The
genera Papilio and Pieris are members of the family
Papilionidce. Make a list of the characters which dis-
tinguish these two families.

104 INSECTS.

The large, red-brown milkweed butterfly, with dark
markings along the veins, is of the family Nymplialidce.
Compare it with a representative of each of the two other
families mentioned.

Notice that all the names of families end in -idee.

The Order. — Note that the smallest group among ani-
mals is the species, and comprises those animals which are
essentially alike. Note that as species are put together to
form a genus, so genera are put together to form a family.
Families, in like manner, make up an order. The three
families mentioned, together with several other families
of butterflies and moths, comprise the order Lepidoptera
(or scale-winged insects). The names of orders usually
end in a.

This grouping of animals is called classification.

Note that all groups are founded upon certain likenesses
in structure and development. A system of classification,
therefore, expresses the structural and developmental rela-
tionships which exist between animals.

Seven of the orders of insects have been studied in a
few of their representatives. Write the names of these
orders in a column, and opposite each write the characters
peculiar to that order. Your list should approximately
define these orders.

Then make a list of the characters which all these have
in common.1 Your list should characterize approximately
the group Hexapoda (or insects proper).

1 If there be time enough, each student so disposed should select, with
the advice of the instructor, some small group of insects for a little special
study, — some genus which offers a number of local species, and one the
metamorphoses of which can be followed through in reasonably short
time, and one for which systematic works that will enable him to identify
the species are at hand. If undertaken at all, the group should be studied
as thoroughly as possible, especially as to its metamorphosis, and its
place in the economy of nature and of man. Full notes should be made
of the things observed during this study; and at its close an account

THE SPIDER. 105

ARACHNID INSECTS.
THE SPIDER.

Haunts. — This much-maligned insect is a very inter-
esting one when we come to study its habits and the won-
derful silken web it spins. Because it bites sometimes
in self-defense, and because it sometimes spins its web
where a web is not wanted, it is very generally hated.
But its bite is seldom serious to human
flesh, and may be avoided by simply
avoiding handling the live spider.
And its web (out of doors) is a thing
of beauty.

No one needs to be told where to
find spiders in warm weather, for they
are everywhere abundant. The largest
ones are best for a first examination.
The spiders which spin their rich geo-

j_ • 1 i • , i . -, SPIDER (Semidiaerram-

metncal webs in the spaces in garden matic) . a> abdomen;
fences or in tangled shrubbery, or the c» cepnaiothorax ; p,
ones which spin their calla-shaped
webs on the ground, spreading the free border out over
the grass at the edge of a sidewalk or beside the founda-
tions of buildings, or the fleet-footed spiders common in

should be written of the genus, stating all the points of structure, haunts,
habits, economy, and development, which all its local species have in
common. This should be concluded with descriptions of each of the
species, for which the following outline is suggested : —
I. Names (scientific, common) .
II. Measurements (length, extent of wings, etc.).

III. Structure (points not already stated in the account of the genus).

IV. Coloration (a detailed description).
V. Haunts and habits.

VI. Preparatory stages (a full account). There is yet room for pioneer

work in this line.
VII. Economic importance of the species.

106 INSECTS.

long grass, which lay no snares at all, but catch their prey
in a fair chase, will serve well for study. There is a
large and gayly colored spider very abundant sometimes
in stubble fields, and often the one most easily obtainable
for class use. It spins a small geometrical web between
the Aveeds that overtop the stubble; and when its web is
jarred by the shaking of the weeds, it drops to the ground,
and feigns death. It may then be picked up with forceps,
and dropped into a cyanide bottle or into alcohol.

In winter, spiders may be found under the bark of dead
trees, or aquatic species may be taken with a net among
the green, submerged plants that grow on the borders of
brooks and ponds. But in winter there will be scant
opportunities for observing their habits or their webs.

Specimens are best preserved in alcohol.

Habits. — Observations on the habits of spiders are best
made while out collecting. The following are but meager
suggestions of what may be done in field study.

1. To see how its silk is spun, pick up a live spider by
a hind leg with forceps, and watch for the formation of a
thread from some blunt protuberances (spinnerets) beneath
and near the posterior end of the abdomen. Draw this
thread out with a pencil, and observe that it is composed
of separate strands. Put at least one spinning spider
into a vial or pill box, and take it home alive.

2. Various methods of spinning may be easily observed.
Certain small spiders will be seen aimlessly trailing a
thread after them as they run about over the grass or
fences, making, not a web, but a tangle of threads ; but
those that make webs of artistic patterns have a uniform
and very curious method of procedure, easily seen where
such spiders are abundant.

3. On a hot afternoon certain very small spiders may
be seen floating in mid-air upon a few gossamer-like

THE SPIDER. 107

threads. This spider climbs to the top of some pile of
boards or of brick, on which the sun has been shining
until a current of hot air is arising from it, elevates its
spinnerets, and starts a thread, which is caught up by
the rising current of air, and drawn out to a length suffi-
cient, by its buoyancy, to support the weight of the spider.
The spider then lets go of earth, and sails away.

4. Of webs, and especially of those in which the spiders
spend most of their time, the shape, position, location,
and construction should be noted. A pair of spiders will
often be found on different parts of one web. The male is
usually much smaller than the female. Of flat webs not
placed vertically, it should be observed whether the spider
walks on the upper, or on the lower, side of the web. It
should be noted that the webs which show the greatest
skill in their construction are made of the fewest threads.

5. That the web is a snare for capturing prey, must
not be forgotten. Note the position of the spider on its
web while waiting for its prey. Throw a small grass-
hopper nymph against the web, and watch the spider's
method of securing its prey. Examine such insects as
you find entangled in webs, and note whether they are
dead or alive. Note the kinds of insects you find snared
by spiders.

6. Examine such old and tattered webs as you find
clinging to fences, and to rafters in attics, for the exuviae
of young spiders. These skins will show the close resem-
blance in form of young and adult.

7. The eggs of most spiders are inclosed in a round
silken capsule which is hidden beneath the bark of posts
and logs, or buried among rubbish, or, in a few species,
carried about by the mother attached to her spinnerets.
It is often a third of an inch in diameter, and of a gray-
ish or dirty yellowish color. Within it the young ones
are hatched, and live for a time by eating one another.

108 INSECTS.

Structure. — Observe that the body is divided into two
regions. The anterior one is the cephalothorax. As the
name indicates, it corresponds to both head and thorax
of insects proper. The posterior region is the abdomen.
Observe the relative size and shape of the two divisions,
and on the lower side of the body find the pedicel con-
necting them.

I. Cephalothorax. — On the anterior prominence of the
cephalothorax find the eyes. With a lens make out their
number, kind, and arrangement.

Examine the two large mandibles that hang down from
the front of the cephalothorax, attached above, and free
below. Study their action. Find a strong, incurved
poison fang at the lower end of each. These fangs are
hollow, and into the wounds they make is poured a poison
secreted by glands situated in the bases of the mandibles.

Observe (from below) a pair of jointed maxillary palpi
arising behind the mandibles, and extending forward,
appearing like a pair of dwarfed legs. Observe that their
basal segments are movable upon each other, and closely
surround the mouth. These, by rubbing together, assist
in comminuting food, and are called maxillae. Find, in
all, six segments in each palpus.

Find eight legs, and in each one seven segments. Ob-
serve the size and arrangement and action of the legs.

Examine the terminal segment to discover by what means
the spider is able to run easily over webs which hopelessly
entangle other insects. Find two pectinated claws, and
(sometimes) a third, which fits, forceps-like, against them.

II. Abdomen. — On the under side, just behind the hind-
most pair of legs, and on either side of the median ventral
line, find two smooth, hard patches covering the openings
to a pair of breathing organs. Each breathing organ is a
sort of rudimentary lung, through the leaves of which the
blood flows for aeration.

THE CHILOPOD OR CENTERED, 109

On the median line, usually a little farther back, are
the openings of the reproductive organs.

Near the posterior end are the spinnerets, usually three
pairs of blunt protuberances, each of which, when magni-
fied, appears to be covered with hollow, jointed hairs.
Through these tubular hairs a fluid substance, secreted
by glands within the abdomen, is exuded ; and the fluid
is of such a nature that it immediately hardens on expo-
sure to the air. When the spider spins its web, it simply
exudes this fluid through the hundreds of openings ; and
the liquid streams, uniting and hardening, form a silken
cord of very many delicate strands. A good way to see
these strands is to allow a live spider, brought in from
the field, to attach its web, when it begins spinning, to
the middle of a glass slip, and then to examine the point
of attachment under the microscope.

Development. — The development of the spider cannot
well be traced in the time allotted to a beginning course
in zoology; suffice it, therefore, to say, that the young
spider, which hatches from the egg and molts a number
of times in coming to maturity, shows much resemblance
to the adult in both form and habits. Its palpi are pro-
portionately longer, more closely resembling true legs,
of which they are modifications.

MYRIAPOD INSECTS.
THE CHILOPOD OR CENTIPED.

Haunts and Habits. — Overturn boards, logs, or stones
that have been lying on the ground for a long time in one
place, and you will find beneath them often numbers of
elongated, wingless insects, of a brownish color, with linear
bodies and numerous laterallv extended feet. Find speci-

110

INSECTS.

mens with long antennae and stout feet, mostly a single
pair to each body segment. These are popularly known
as centipeds. They may be picked up with forceps and
put into the cyanide bottle.

The seclusive and predatory habits of the live chilopod
should be studied, and also the use of its antennae, and
the order of moving its feet in walking.

Thousand-legs will be found in similar situations, distin-
guishable by its smaller size, shorter antennae, two pairs
of legs (apparently) to each segment, and by its disposi-
tion to curl up when touched. Specimens should be col-
lected for comparison.

External Features. — Write a description of the chilo-
pod which shall embody the answers to the following
questions : —

1. How is the body divided into
regions, as compared with other in-
sects ?

2. How many segments in the
body?

3. How many eyes are there, and
of what sort ?

4. What is the shape of an an-
tenna, and how many segments in it ?

5. How many appendages has the
first segment back of the head, and
of what sort ?

6. Where are the poison fangs
situated ?

7. Of what character are the
mandibles ?

8. Why are not the legs underneath the body ?

9. What adaptations do you discover of the shape and
structure of the body to the life the insect leads ?

CHILOPOD OR CENTIPED
(X2).

CRUSTACEANS.

THE CRAWFISH.

(Cambarus.)

Haunts. — In warm weather this animal may be found
crawling upon the bottom of brooks and natural ponds.
The largest specimens will be found in creeks and in
ponds which are not dried out in summer. A water net
will be of service in securing specimens. Large specimens
may often be obtained in abundance under rocks in shallow

CRAWFISH, natural size (after Morse).

rapids of creeks. A bright light on the bank of a creek
at night will attract many to the edge of the water, where
they may be taken with a dip net. This is perhaps the
easiest way to obtain a supply. It requires only a little
waiting and careful watching. The light should be so
placed, that, as it shines down into the water, the bottom
is visible. Different species will be found in different

111

112 CRUSTACEANS.

situations. Some live in holes in the soil ; others do not.
Some of the former build chimneys of mud about the
entrance to their holes ; others do not. Some live at the
surface of ponds, on the floating or submerged leaves of
aquatic plants.

In many localities throughout the interior the species
that live in holes are very abundant. The following
questions suggested for field study of their habits may
be useful : —

1. What are their hours of activity ?

2. At what depth of water do you find them ?

3. Do they live singly, in pairs, or in communities ?

4. Do those that live in holes make the holes for them-
selves ? Are their holes ever found sheltered beneath
stones and tree roots ?

5. What is the general shape, size, and direction of
these holes, and at what level do they terminate below ?

6. In such as build chimneys, how is the chimney con-
structed? Is the chimney ever found plugged up with
mud, except in very dry weather ?

7. How many species do you find, and what are the
haunts of each ?

In winter, numbers of certain species may often be found
huddled together under the sheltering edge of some loose
stone in the bed of a creek. Where the holes of other
species are common in the banks of brooks, they may be
dug out when the ground is not frozen.

Habits. — Live specimens may be kept for a long time
in any sort of aquarium supplied with food. They will
eat snails and insects greedily, and will live on almost any
kind of flesh.

Startle a crawfish at rest upon the mud, and observe the
cloud it raises in the water, behind which to escape.

Watch a crawfish walking about in an aquarium, and

THE CRAWFISH. 113

see how many feet it walks with, and in what order they
are moved.

Startle it by thrusting a stick toward its eye, and see
its rapid locomotion backward. How is this effected ?

Observe its feeding habits.

Place a live crawfish in a small dish, and barely cover
it with water. Take hold of its body with forceps, and
observe its way of defending itself.

Observe that its eyes are stalked and capable of pro-
trusion outward.

Gill Currents. — Observe that on each side of the body
that portion of the hard crust beneath which the legs are
attached is marked off from the rest by a shallow curved
groove. Within the portion so marked off at the base of
the legs is the gill chamber, containing true gills. This
chamber is open at both ends for the passage of currents
of water. Determine the direction of the currents by
placing a drop of ink or other colored fluid in the water
near each end of the chamber, and watching it move.

Study the structure of a crawfish which has been a
short time in alcohol.

Plan of Structure. — The body is divided into two
regions. The anterior one is the cepTialothorax ; the
posterior one, the abdomen.

Observe that the body is made up of a series of seg-
ments. These segments are very evident in the abdo-
men, but not so plain in the head and thorax, where they
will have to be looked for on the ventral surface. It will
be seen that each pair of legs, at least, is attached to a
single segment, though no traces of segments may be dis-
coverable on the dorsal surface.

Observe that every distinguishable segment, except the
hindmost, bears on its lower surface a pair of appendages,

NEED. ZOOL. — 8

114 CRUSTACKANS.

Mild that these appendages vary greatly in si/e on I lie
different segments.

I. Cephalothorax. - - The hard shell, which entirely
-•(•\ci's I li«- cephalothorax in its normal position, is tlie
carapace. 'I 'In-, stout beak extending forward from the
front of it, between the eyes, is the rostrum. Observe
that the whole is divided into portions corresponding

l,o head ;ind thorax by a shallow n-n^'rn/ //rm>/v lha! runs

transversely across the top of the carapace, and extends
obliquely l'or\v;ml along the sides. The two longitudinal
grooves on the carapace hack of t he cervical groove, which
mark the line of separation of the two gill chambers from
the thorax proper, have been noticed already.

II. Abdominal Segments. — Note the number and form
of the abdominal segments. Flex and extend the abdomen,
and study their action. Take the third or fourth abdomi-
nal segment as a type, and in it locate the parts as named.
The convex dorsal plate of the segment is the notwm, or
teryum ; the projecting plate that hangs down on either
Hide like the eaves of a roof is (he //A-///-/////.; I he ventral
transverse bar between the bases of the two appendages is

the sternum. The appendages themselves are jointed, and
two-parted at the tip.

Observe the soft membranous parts connecting the ab-
dominal segments, and the pivotal joining of the segments
together at their lateral edges, facilitating the ilexion
and extension of the abdomen, but preventing lateral
motion.

At the posterior end of the body is the tail fin, and its
central piece is the terminal segment of the body, and the
seventh abdominal segment, called the telson. It bears no
appendages, and has but slight external resemblance to
the other body segments, being much modified to suit a
special purpose. The two pairs of similar broad flaps,
which, together with the telson, comprise the tail fin, are

THE CRAWFISH. 115

the specialized two-parted tips of the appendages of the
sixth abdominal segment.

Dissection. — The remaining parts to he mentioned are
best seen upon dissection. The crawfish is best dissected
under water.1 Pin it to the bottom of your dissecting
pan, with the right side of the body upward, and the head
from you. Fasten one pin through the base of the ros-
trum, draw the body out full length, and fasten another
pin through the left appendage of the sixth abdominal
segment. Cover the specimen with water, dissect slowly
and carefully and as directed, and change the water as
often as it becomes cloudy.

I. Appendages. — Begin with the series of appendages,
and, for convenience in dissecting, proceed from the pos-
terior end forward. Remove each appendage of the right
side in order, and be very careful to get each one off
entire. Preserve all in their proper order for drawing.

The absence of appendages from the terminal segment
has already been noted. The broad finlike character and
the extension backward of the appendages of the sixth
abdominal segment have also been noted. The smaller
appendages of the remaining five abdominal segments are
extended forward, close under the abdomen, and are called
swimmerets. Each consists of a short pedicel of two seg-
ments, with a pair of jointed and fringed filaments at the
tip. The swimmerets of the fifth, fourth, and third ab-
dominal segments are very similar, but those of the second
and first segments . are reduced and smaller, or the first
entirely wanting in the female, while in the male they
are specialized, bent forward strongly under the thorax,
and variously forked, hooked, or twisted at the tip.

The next five pairs of appendages are the legs, and
belong to the thorax. Before removing these, it will be

* See Appendix, p. 283.

116 CRUSTACEANS.

well to remove that part of the carapace which covers the
right gill chamber at their bases. To do this, cut through
the carapace with fine-pointed scissors, along the groove
that marks the boundary between the branchial chamber
and the thorax proper. Begin at the posterior end of the
carapace, and cut forward along this groove to the cervi-
cal groove, and obliquely forward to its anterior end.
Turn down and break away the cover of the gill chamber,
and expose the gills. Observe their feathery appearance.
Observe that they fill the chamber, and come in contact
with all the water that passes through it. Move the legs
backward and forward, and note the effect on the gills.
Observe that the gills are arranged in vertical series cor-
responding in position with the legs. Observe that they
are also arranged in longitudinal series, the lower series
being attached to basal segments of the legs, and the
upper series (a double series) attached to a membrane
extending between the wall of the thorax and the legs.

Examine with a lens, and compare in structure, the gills
of one complete vertical series. Tear a small gill to pieces
with needles, under water, to make out its structure.

Remove now each leg, with its attached gill, proceeding
from the rear. To do this, place a knife blade between
the bases of the leg to be removed and the one in front of
it, and, by prying, break its hard attachments, and then,
with a sharp knife or scalpel, cut its membranous attach-
ments. Of the five pairs of legs, the first is used for
prehension and defense, and the others for walking. The
openings of ducts from the reproductive organs are little
pores perforating the inner angles of the basal segments
of a pair of legs, — in males, the fifth or hindmost pair ;
in females, the third pair.

Having removed the five legs of the right side, study
the foremost. Note its great size. Flex and extend it,
and study the structure and action of its joints, esDeciallv

THE CRAWFISH. 117

of the powerful forceps at its end. Why are the blades
of the forceps roughened on their inner edges ?

Is there any part in the foremost leg that is not present
in the other four ?

There yet remain three pairs of small thoracic appen-
dages. These are the maxillipeds (or foot jaws). They
cover the mouth, being directed forward. The mouth opens
directly upward : probe between the maxillipeds to find
it. These maxillipeds, by the rubbing together of their
opposed segments, assist in the comminution of the food.

Remove the hindmost maxilliped, and compare it in
structure with the typical abdominal appendage already
studied. Observe that it has a pedicel of two small seg-
ments, bearing two branches ; that it has (and the swim-
meret has not) a gill on the inner side of the basal segment.
Remove the second maxilliped, and find in it all the parts
present in the third.

Remove the first maxilliped, and find the same parts
found in the other two, except the gill. In the place of
the gill, there is a broad plate, on the inner side of its
basal segment. The vertical series of gills begins with the
second maxilliped. Observe that the second and first
maxillipeds are much smaller and softer than the third.

The remaining appendages are believed to belong to
the head.

Closely following the maxillipeds, and covered by them,
are two pairs of very thin and delicate maxillae. These
are small, and closely appressed, and in removing them
care must be taken to separate them, and to take them
with the forceps by their basal segment.

Before removing the maxillye, the gill scoop attached to
the second one should be seen in place. It is a curved
plate, attached to the outer side of the maxilla ; it plays
backward and forward in the anterior opening of the gill
chamber, and by a sort of sculling action propels the water

118 CRUSTACEANS,

forward, out of the chamber. Watching it closely, pull
the maxilla of the opposite side backward and forward,
and you will see how it acts. Because it keeps the water
moving, it is a very important accessory organ of respira-
tion. The water that bathes the gills must continually be
renewed, in order that sufficient oxygen may be obtained
from it for the needs of the body.

In front of the maxillae, find a pair of short, hard,
toothed mandibles, each with a small, three- jointed palpus
lying in a groove on its anterior surface. Study the action
of the mandibles. Find a thin, leaf -like, un jointed plate
(the metastoma), fitting closely against the posterior sur-
face of the mandible. This is not considered as a true
serial appendage, but only as an outgrowth from the
border of the mouth.

On the front of the head are two very long antennas.
Draw one of these downward, and find a large, basal seg-
ment, bearing on one side a light-colored, conical process.
In this process the duct from an excretory gland in the
head terminates. Find, also, a blade-like branch of the
antenna beneath the eye. What is it there for ?

The evidently two-forked, short appendages above the
antennae are the antennules. Beneath the eye, in the base
of each antennule, is a so-called ear sac.

Compare in structure an antennule with an antenna ;
with a mandible ; with a maxilla ; with a maxilliped ;
with a leg ; with a swimmeret. Observe that they all
exhibit modifications of one type of structure ; and the type
is a two-jointed pedicel, bearing (normally) a pair of
jointed branches. In the legs, one of the branches is
suppressed, and the other is enormously developed to form
the part of the leg comprised in the five terminal segments.
In all the thoracic appendages, except the first and the
last, there is an internal process from the basal segment,
forming a gill.

THE CRAWFISH. 119

Preserve all these appendages in their proper order until
the dissection is finished.

II. The Eye. — Examine the eye. Pull • it outward
with forceps, and note the length of its stalk. Its stalk
is muscular, and capable of turning the eye, when pro-
truded, to look in any direction, — an admirable compen-
sation for the stiffness of the creature's neck. Examine
a section of its cornea with low power, to make out
whether it is a compound eye or an ocellus.

III. Internal Organs. — Now carefully dissect away
from the thorax the wall that is uppermost, and cut
away all of the carapace as far, at least, as the median
dorsal line, taking care not to injure any of the deli-
cate organs that lie beneath. Cut away, also, all the
part that is uppermost of the notum (tergum) of the
abdomen ; also the right pleurum.

(1) Organs of Circulation. — In the inner wall of the
branchial chamber, observe the vertical canals which
convey the blood from the gills toward the heart. These
canals may sometimes be seen through the wall before
dissection of this part.

The heart lies in the top of the thorax, under the center
of the carapace, in a sort of membranous inclosure called
the pericardial sinus. AVhen the carapace is cut away,
beneath it should be found the thin, upper wall of this
cavity. Cut through this, and expose the heart, a thin
transparent, angular sac, suspended normally in the color-
less blood that fills the sinus. Find five small arteries
starting from its anterior end. Three of these, the central
ones, proceed directly forward toward the head ; and the
other two, the lateral pair, proceed downward and forward
toward the lobes of the liver, which they supply with blood.
Find a large artery starting from the posterior end of the
heart, and immediately dividing into two branches, one
of which continues backward along the upper side of

120 CRUSTACEANS.

the abdomen, while the other turns downward toward the
ventral surface. All these arteries convey blood out from
the heart directly to the tissues, through their many
minute branches. The blood has no such channels for
return, but finds its way back to the gills by percolating
through the interspaces of the tissues and internal organs.
It comes back, necessarily, laden with carbonic-acid gas,
the product of oxidation in the tissues, and must needs
go to the gills to exchange this noxious gas for a fresh
supply of oxygen. There is a passageway for the blood
up one side of the central supporting portion of the gill,
and down the other ; and to get from one into the other,
the blood must flow through very delicate capillary tubes
that lie out in the most delicate gill filaments, and connect
the two passages. In passing through these capillary
tubes, the blood currents on the inside of them are sepa-
rated from the water currents outside only by very thin
membrane, through which the necessary exchange of gases
takes place. The blood is then returned from the gills
through the vertical canals already noticed in the thoracic
wall, to the pericardial sinus. It reenters the heart
through six apertures which are guarded by valves iii-
side. One of these apertures may be seen on each side
of the heart, a pair on its upper surface, and a pair on
its lower surface. Find them, using a lens. When the
heart is filled with blood, it contracts ; and the blood,
being prevented by valves from flowing back into the
pericardial sinus, is forced out through the arteries.
When the heart relaxes again, the valves fly open, and
the blood from the sinus rushes in and fills it, and is
driven outward through the arteries at its next contrac-
tion. The currents coming up from the gills continually
renew the supply in the pericardial sinus.

Several delicate fibrous bands may be seen connecting
the heart with the walls of the pericardial sinus.

THE CRAWFISH. 121

(2) Organs of Reproduction. — The reproductive organs
will be found just beneath the floor of the pericardial
sinus, whitish in the male, and with a pair of very long
convoluted tubes or ducts (one on each side), yellowish
(sometimes dark colored from the presence of eggs), in
the female, and with a pair of short, descending ducts.

(3) Organs of Digestion. — Study next the organs of
digestion, the alimentary canal and its appendages. Dis-
sect away all the organs that cover it. In doing this-,
observe in the abdomen a thin layer of muscle above the
straight intestine, and a thick layer below it. The upper
muscle extends to the abdomen, and the lower flexes it.
What reason is there for the much greater size of the
flexing muscle ? Make a shallow cut along the median
line of this lower muscle, and remove the upper half of
it. It will separate easily, if taken in a single long roll.

A pair of big forceps, three pairs of maxillipeds, two
pairs of maxillae, and one pair of mandibles, have already
been found to be the external agents for the communica-
tion of food. The food passes from the mouth directly
upward through a short esophagus, into a large, bag-like
stomach, which nearly fills the head cavity, and extends
backward a little way into the thorax. It is divided into
two chambers by a constriction. On either side of its
posterior end are a pair of large yellow or brown glands,
which are accessory organs of digestion, called liver.
Find the ducts by which they pour their secretions into
the alimentary canal. Posterior to these is the straight
intestine.

The comminution of the food is continued in the
stomach, the internal surface of which is armed with
hard teeth and ossicles, which make it a grinding organ.
Cut it open, and find these hard parts. The food passing
out from the stomach is mixed with secretions from the
liver, and is digested. It then passes through the walls

122 CRUSTACEANS.

of the intestines, directly into the blood, and is ready
for distribution, and for use in the cell construction.

Tear a bit of liver to pieces in water on a slide, and
examine with low power to make out its structure.

In the base of the head, in front of the mouth, are
two small excretory glands of light-greenish color. The
ducts from these open on the basal segments of the
antennae, as already noticed.

IV. Nervous System. — Find now the parts of the
nervous system. On the floor of the abdomen a longi-
tudinal chain of nervous ganglia will be readily seen.
Count the ganglia of the abdomen. Observe the deli-
cate white nerve fibers radiating from them.

In the thorax, the chain seems to disappear in a sort of
canal formed on the ventral surface by the hard plates
arising from the floor, and forming a sort of internal
skeleton. These plates are for the attachment of the
powerful muscles of the legs and of the abdomen. By
carefully cutting away the hard parts that hide the nerve
chain, it may be followed forward to the head. A large
ganglion will be found just behind the esophagus, and a
larger cephalic ganglion or brain will be found just behind,
and a little above, the bases of the antennules. These
two large ganglia are connected by fibers passing on either
side of the esophagus, and forming the esophagal nerve
collar. From the cephalic ganglion, nerves may be traced
to the eyes, antennae, and antennules.

V. Concluding Work. — If any of the paired organs
mentioned have not been found thus far, they may be
looked for in what remains of this dissection (the left
side), or in another specimen. Finally remove carefully
the series of appendages belonging to the left side of the
body.

Gather together in pairs all the appendages of the
body, in order, as follows : —

THE CRAWFISH. 123

One pair of antennules.

One pair of antennae.

One pair of mandibles.

Two pairs of maxillae.

Three pairs of maxillipeds.

Five pairs of legs.

Six pairs of swimmerets.

Draw all these accurately and in order, twice natural
size. If the parts of the smaller appendages are not
easily made out, place such between two glass slips, and
examine with low power of microscope.

Make a diagrammatic drawing of a longitudinal section
of the body, showing the relative size and position of the
principal internal organs.

Make a drawing of a crawfish in its natural position,
as seen from above.

Serial Homology. — Observe the striking similarity in
structure which underlies the great diversity in size and
use in all the appendages. Similar likeness in the
arrangement of the parts of the segments which bear the
appendages is also evident; and these things, together
with a more marked correspondence during the early
stages of development, indicate that each segment is
homologous with every other. The segments being
serially arranged, this is called serial Jiomology.

Development. — If crawfishes be collected in early spring,
the females will be found with large, berry-like clusters
of small, round, dark-colored eggs, glued fast to the
swimmerets. As these are lashed backward and forward
through the water, the eggs are continually washed, and
kept free from mud and other impurities. When the
eggs hatch, they split in halves, and the emerging young,
already armed with well-developed forceps, cling to the

124 CRUSTACEANS,

swimmerets. The young, when hatched, are nearly a
quarter of an inch long, almost transparent, and in struc-
ture show much resemblance to the adults. The points
of their forceps are variously hooked, enabling them the
better to hang on to the maternal swimmerets. In the
process of development, molting takes place several times.
The carapace splits down the back, and the animal crawls
out limp and defenseless. It has great difficulty in with-
drawing its legs, and sometimes breaks them off ; but new
ones will grow out from the broken stumps. Specimens
will be found occasionally with one forceps smaller than
the other : the smaller one is replacing one that has been
lost.

The time of each molt is a critical period in the life of
the animal ; for when its hard coat of mail is gone, its
muscles overwrought with the struggle of extrication, and
even its defensive weapons soft and pliant, it becomes an
easy prey to even its weaker enemies. It therefore seeks
the closest seclusion at such times.

The exuvia of the crawfish is not broken in molting,
except by the one longitudinal slit ; and after the animal
emerges, the edges of this slit come together again elas-
tically, and the exterior looks much as it did before the
molting. The hard parts of the stomach are shed also
at every molt.

Crawfishes live a number of years. They grow rapidly
during the first season, after attaining a length of an inch
and a half. They grow more slowly in later years, and
rarely attain a length of more than five or six inches.

Crawfishes belong to the group Crustacea.

Other Crustaceans. — Two other very common crusta-
ceans are excellent subjects for study here, as they illus-
trate important differences in crustacean structure.
These are the Asellus and the Cyclops.

THE ASELLUS.

125

THE ASELLUS.

Haunts. — This animal lives amid the submerged plants
of our streams and ponds. It is about an inch long,
and of a uniform slaty gray or pale-brown color. If plants
be drawn out of the water, it will be found clinging
to them, and may be picked up with
forceps, and dropped into alcohol for
preservation. Live specimens should
be kept in a glass jar, in water, with
aquatic plants, in order that their
feeding habits and method of getting
about may be studied.

External Features. — Place a live
asellus in a watch crystal with water.
Add a few drops of chloroform or
ether. Observe as to its general form
the following points : —

1. A nearly linear body, much flat-
tened dorsally.

2. A distinguishable head, with a
pair of sessile eyes, and greater and
lesser antennae, easily seen from above.

3. A long, distinctly segmented thorax, bearing seven
pairs of legs.

4. A short, broad abdomen, with a pair of terminal sty-
lets projecting posteriorly.

As soon as the animal has become quiet, place the watch
glass on the stand of the microscope, and with low power
(100 diameters) focus upon various parts of the abdominal
stylets. They are sufficiently transparent to permit the
blood in them to be seen circulating.

Obtain a specimen which has been a short time in alco-

ASELLUS.

126

CRUSTACEANS.

hol, and examine the gills (which are beneath the abdomen
in this crustacean) and the mouth parts. Then remove
all the appendages of the body, arrange them in order
in glycerine upon a slide, cover with another slide, and
make a serial drawing of them as seen, magnified 10 to
25 diameters. Make a larger drawing of the terminal
segments of one of the first pair of thoracic legs, and
explain the action of these parts.

THE CYCLOPS.

Haunts and Habits. — The water of an aquarium in
which aquatic plants have been growing is almost certain
to contain this animal. It is large
enough to be seen without a lens
(about a twenty-fifth of an inch long).
It appears as a white speck in the
water, is very active, and swims with
a peculiar jerky movement. Each
large female cyclops will usually carry
a pair of egg sacs attached at the sides
of the abdomen.
*

External Features. — Take up half
a dozen such specimens with a drop-
ping tube, place them in a watch glass
with water, and add a little ether.
Place them under the miscroscope,
and, having found one that presents a
good dorsal view, study it with low
power, to make out the following points as to its general
form : —

1. An oval body, tapering posteriorly.

2. A dome-shaped carapace, covering the front of the

CYCLOPS (X120).

FURTHER CLASSIFICATION. 127

cephalothorax, followed by four free thoracic segments of
gradually decreasing width.

3. A tapering abdomen terminated by a pair of long,
bifurcated stylets.

4. A pair of relatively large egg sacs attached to the
first of the four apparent abdominal segments. This first
segment is really composed of two segments which have
grown together in the development of the female, but
which remain distinct in the male (see cut).

On the extreme front of the carapace find a pair of eyes
so close together that they appear as one under low power.

At the front find also two long, conspicuous first an-
tennce, and just beneath them a pair of small second antennce.

The remaining appendages may be seen in a ventral
view of the animal. They are a pair of blunt, dark-
colored mandibles, and two pairs of bristling maxillce,
surrounding the mouth, and some distance behind these
five pairs of thoracic appendages (legs), the fifth pair
rudimentary.

Note the absence of breathing organs. Respiration
takes place through the skin.1

FURTHER CLASSIFICATION.

We have illustrated, by examples, species, genera, fam-
ilies, and orders, among animals. We have said that the
species is the smallest zoological group, and comprises
animals that are essentially alike. We have combined
related species into a genus, related genera into a family,
and related families into an order. And now we have
extended our study far enough to have material for illus-
trating the higher groups. Orders are in the same way

1 Read "Anatomy and Metamorphosis of Cyclops," in Brooks's Hand-
book of Invertebrate Zoology.

128 CRUSTACEANS.

combined into classes. The centiped, spider, and all
the orders of six-footed insects already studied, belong to
the class Insecta. Make a list of the characters which all
these have in common. This will approximately charac-
terize the class.

The crawfish, asellus, and cyclops represent separate
orders, which are included in another class, the class Crus-
tacea. Make a list of the characters these have in common.

Classes are in like manner combined to form branches.
Thus the two classes, Insects and Crustaceans, constitute
the branch Arthropoda (or jointed-footed animals).

Branches are the primary divisions of the animal
kingdom.

All animals having the body made up of a definite
number of rings or segments with the hard parts outer-
most, and with jointed appendages, comprise the branch
Arthropoda.

All arthropods that breathe by trachese (or tracheal
gills) comprise the class Insecta.

All insects with scaly wings and complete metamor-
phosis comprise the order Lepidoptera, etc.

It often happens that the constituent members of one
of these groups show different degrees of relationship
toward each other. For example, in the class Insecta the
orders of six-footed insects show much closer relationship
to each other than they show toward the orders to which
the spider and the centiped belong. In a case like this
it is convenient to recognize intermediate groups. Accord-
ingly all the orders of six-footed insects are combined into
a subclass, Hexapoda; the spiders are placed in another
subclass, Arachnida; and the centiped and thousand-legs,
etc., are placed in still another, the subclass Myriapoda
(or many-footed insects). So intermediate groups, when
found in nature, may be interpolated between any of the
other groups.

FURTHER CLASSIFICATION. 129

Do not fail to learn that these groupings are but the
result of an attempt to represent systematically the like-
nesses and differences of animals. The boundaries of the
groups were but roughly laid out by the early systematic
zoologists. They have had to be changed in the past as
the structural and developmental relationships of animals
have become better known. They are changing now, and
are liable to further change with increasing knowledge in
the future. Any proposed system of classification, to be
acceptable, must be natural; i.e., founded on existing
important relationships.

NEED. ZOOL. 9

WORMS.

THE EARTHWORM.

(Lumbricus.)

Haunts and Habits. — This animal is familiar enough to
the man who tills the soil, and to the boy who goes fishing
and digs his own bait. It is common in garden soil every-
where. It is strictly nocturnal in its habits. In warm
weather it may be observed, with the aid of a lantern at
night, extending itself from its burrow, and searching the
ground over within a radius of its own length.

.XT

EARTHWORM (Lumbricus terrestris).

It swallows earth in great quantities, and, having
extracted from it whatever organic matter it contains,
ejects it again in the form of castings. These broken
vermiform castings are familiar objects to every observ-
ing person, for there is hardly a path in garden or meadow
that is not strewn with them. They are often found
abundantly, late in autumn, under piles of fallen leaves.
The worms in this way bring great quantities of subsoil
to the surface, and greatly increase the porosity of the
soil by eating holes through it.

130

THE EARTHWORM. 131

Specimens for study may be obtained by digging, and
at night by simply picking them up when they are out
of their burrows and extended on the ground. At sun-
rise they may be seen in the mouths of their burrows, or
partly extended, not having retired for the day. This
explains why "the early bird catches the worm."

Field Study. — In the field, observe : —

1. The quickness with which they retreat when dis-
turbed by a heavy step on the earth near their burrow.

2. The force with which they cling to their burrows
when an attempt is made to drag them forth.

3. Their insensibility to sounds, however loud, and
their slow sensibility to light.

4. The size, direction, and depth of their burrows.

5. The plugs found stopping the mouths of the bur-
rows in the daytime, the materials used, and the skill
shown by the worms in their method of plugging.

In winter, specimens obtained by digging may be placed
in a box, or large flowerpot, of earth, and kept in a warm
place, where they will quickly resume activity. They
may be fed on bits of raw meat, preferably fat, of onion,
celery, cabbage, etc., thrown on the surface of the soil;
and when they are feeding at night, their habits may be
observed with a lamp. By hiding bits of food beneath
the surface of the soil, the student may determine whether
worms have anything corresponding to the sense of smell,
enabling them to find food with which they would not
ordinarily come in contact.

Study of a Live Specimen. — Place a live worm on a
sheet of wet paper, and observe : —

1. In its body —

(a) Definite anterior and posterior ends.

(6) Correspondence of right and left sides (bilateral
symmetry).

132 WORMS.

(c) The numerous similar transverse segments compos-
ing the body.

(d) The absence of appendages.
2. In its motions —

(a) Rhythmic contractions and corresponding changes
in form of its body.

(6) Irregular progression forward.

Place the worm on a smooth, clean pane of glass, and
observe, that, while its contractions continue, its progres-
sion ceases.

Draw the worm backward across a finger, to feel the
minute setae (or bristles) by means of which it holds its
ground on any except the smoothest surfaces.

Observe how it crawls backward when touched near
the anterior end, performing reflexly the acts which under
its ordinary conditions of life would carry it to a safe re-
treat within its burrow.

Turn it over on its back and observe what follows.

Tap the paper, or jar the table, on which it lies, and note
the result.

External Features. — For a study of the general struc-
ture of the earthworm, use specimens that have been
anaesthetized with chloroform. Select the largest speci-
men obtainable, and dissect it under weak alcohol ; but,
before dissecting, observe with a lens the following
among its external features : —

1. The darker color of the dorsal surface.

2. The greater length of the body -segments at the
tapering anterior end.

3. The dorsal flattening of the posterior end of the
body.

4. The mouth at the anterior end, and the prostomium
projecting forward above it, from the dorsal side of the
foremost segment.

THE EARTHWORM. 133

5. A swollen region (the clitelluni) between the thirti-
eth and fortieth segments (counted from the front), em-
bracing several segments.

Find a pair of small pores on opposite sides of the
median ventral line of the fifteenth segment, and another
similar but smaller pair on the fourteenth segment. These
are the external openings of the reproductive organs.
Two other pairs of pores may be made out, sometimes
with difficulty, on opposite sides of the median ventral
line, — a pair on the groove between segments 9 and 10,
and another pair on the groove between segments 10 and
11. These are the openings of the seminal receptacles,
(accessory organs of reproduction).

A row of pores is present on the median dorsal line,
one at the anterior edge of each segment, opening directly
into the body cavity. These are not very evident.

Find two pairs of sette (or locomotor bristles) on each
side of each segment, — one pair at the edge of the flattened
ventral surface ; the other a little higher, on the side of
the body. Observe that these are arranged in four longi-
tudinal double rows.

Pin the specimen down for dissection beneath weak
alcohol, with one pin through the prostomium only, and
another through the last segment, with the body slightly
stretched between the pins. Very great care will be
necessary to successfully complete the following dissec-
tion. Cut no more than directed.

Dissection. — With thin, sharp scissors make a shallow,
longitudinal cut through the body wall, along the dorsal
surface, the entire length of the body, taking care not to
injure the organs which lie beneath. At the middle of
the body draw the edges of the cut apart, and observe the
septa (or partitions) which extend transversely across the
body cavity. Observe that these correspond in position

134 WORMS.

with the depressions between segments seen on the exte-
rior, and show internal segmentation. Observe that each
of the septa is perforated at the center for the passage of
the alimentary canal and other vessels. Observe, also,
that the segmentation of the body extends to the alimen-
tary canal, which in this region is somewhat expanded in
each segment.

Beginning at the anterior end, cut the septa close to the
body wall on each side down to the uppermost row of
setae, and pin back the flaps, exposing the internal organs.
Most conspicuous among these will be the large-lobed,
white seminal vesicles, nearly filling the body cavity
between the tenth and the fifteenth segments, and
the darker-colored alimentary canal extending straight
through the center of the body longitudinally.

Find a dorsal Hood vessel extended along the upper side
of the alimentary canal, with five pairs of aortic arches
extending downward from it in segments 7 to 11, and
meeting below the alimentary canal in the ventral blood
vessel, which extends backwards longitudinally.

I. Organs of Digestion. — Beginning at the posterior
end, lift out the alimentary canal, carefully dissecting it
free from the septa, and avoiding disturbing other organs.
Make out in the alimentary canal the following parts : —

1. A wide pharynx, posterior to the mouth, with many
radiating muscle fibers extending from its walls to the
outer body walls. When the soft margins of the mouth
are applied to any object that is to be seized, these muscle
fibers, contracting, dilate the pharynx, creating within it
a partial vacuum, and exerting a powerful sucking action
upon the object seized.

2. An esophagus, a slender, thin-walled tube, extending
backward from the pharynx.

3. Three pairs of minute yellowish white calciferous
glands attached to the esophagus in segments 10 to 12.

THE EARTHWORM. 135

These secrete a milk-white fluid of unknown function,
containing carbonate of lime.

4. The crop, a thin- walled dilatation of the alimentary
canal in segments 15 and 16.

5. A muscular gizzard, lined with membranes elevated
in chitinous ridges, usually occupying segments 17 to 19.
This is the principal organ for grinding and comminuting
the food.

6. The remainder of the alimentary canal is the intes-
tine. It probably possesses digestive functions through-
out its length.

II. Organs of Reproduction. — Cut the alimentary canal
in two at the back of the pharynx. Leave the pharynx
in place, but remove the remainder of the digestive tract.
After it is lifted out from between the lateral lobes of
the seminal vesicles, these organs will be fully exposed.
These cover the male reproductive organs ; and a pair of
ducts extend backward from them, to open to the exterior
at the pores already noticed on segment 15.

The earthworm is hermaphrodite, and ovaries will be
found (sometimes with difficulty) on the floor of the
body, — a pair of minute, whitish bodies on either side
of, and close to, the median ventral line of segment 13.
The disconnected oviducts, posterior to the ovaries, pene-
trate the septum between segments 13 and 14, and open
to the exterior at the pores already noticed on seg-
ment 14.

Attached to the septa, between segments 9 and 10
and 10 and 11, are two pairs of minute, whitish sacs,
which open, directly downward. These are the seminal
receptacles, the accessory organs of reproduction already
noticed. In them the sperms from another individual are
stored until the time when the eggs are laid ; for, though
the earthworm is hermaphrodite, cross-fertilization seems
to be the invariable rule.

136 WORMS.

III. Nervous System. — Remove the seminal vesicles.
This will entirely expose the nerve cord which lies -ex-
tended along the floor of the body cavity its entire
length. Observe the ganglion-like swellings in each seg-
ment. Observe the nerves given off from it to each seg-
ment. Trace it forward to the pharynx. Observe that
it forks, surrounds the pharynx, and unites again above in
the cephalic ganglion (or brain). Compare this arrange-
ment of the central nervous system with that already seen
in crustaceans and insects.

IV. Organs of Excretion. — Observe the segmented
organs (nephridia), — little, tangled, thread-like bodies,
attached to the posterior side of each septum, one on
each side of the body in each segment. Each of these
organs opens to the exterior by a minute pore, not here-
tofore noticed, and not easily discovered. Each opens
internally at the end which floats free within the body
cavity, by a minute ciliated orifice (discoverable only by
careful microscopic examination). These are excretory
organs, and drain out waste and worn-out materials from
the body.

V. The Body Wall. — Spread out the body wall per-
fectly flat, and pin it so. Observe its muscular lining.
Note that the longitudinal, fibrous bands are discontinu-
ous, as such, along the lines occupied by the locomotor
setae. These setae are moved by small muscles of their
own, not the least in importance in the animal's mechan-
ism. Strip up some of the longitudinal muscles, and
observe the circular ones that lie beneath. Outside these
is a layer of epidermis.

VI. The Body Cavity. — Cut a clean transverse section
of another specimen which has been hardened in alcohol,
using a very sharp knife or scalpel, and examine the cut
end with a lens. Note that the body is made up of two
tubes, one within the other, — the inner one, the diges-

THE EARTHWORM. 137

tive tract, muscular on its outside ; the outer one, the tube
formed by the body wall, muscular on its inside. Note
that the body cavity between these two is bridged by
the numerous transverse septa. Compare the earthworm
with the crawfish and the grasshopper in respect to this
structure.

Microscopic Examination. — Obtain another anaesthe-
tized worm. Insert a slender pointed pipette through a
puncture into the body cavity, and draw out a drop of
the fluid filling that cavity. Place the drop on a slide,
cover, and examine with high power of microscope to
discover : —

1. Chloragogue cells, large and irregular, and yellowish
in color. These cells form a layer surrounding the ali-
mentary canal for a great part of its length. They are
believed to perform the functions which the liver per-
forms in higher animals, at least to the extent of secreting
a fluid to aid in the digestion of food.

2. Amoeboid blood corpuscles, so transparent they may
be overlooked at the first glance. These show pseudo-
podia, and, if kept warm, may be seen to be in action,
like amoeba, whence the name. It must be borne in mind
that these cells do not have an independent existence like
amoeba, but that they are constituent cells of a many-
celled animal, dependent for their life upon conditions
supplied by other parts.

3. Sperms. Lay open the body cavity. P-uncture one
of the seminal vesicles, and take from it with a pipette a
drop of its fluid contents. Mount, cover, and examine this
with high power of microscope. It should contain many
minute filiform sperms, some of which may be seen actively
swimming about. They may often be better seen (but
not in motion) after running a drop of magenta under
the cover. »

138 WORMS.

Mechanical Movements of Blood Vessels. — The me-
chanical action of the parts concerned in nutrition can
best be understood by studying them in a live worm.
Small specimens can be found so nearly transparent, that
the blood vessels can be seen from the outside, and their
pulsations watched with a lens. But it will be found
more satisfactory to study these things in a large living
specimen that has been stilled with chloroform or ether.
Pin the specimen out in the dissecting pan in a |-per-cent
salt solution, as before directed, and open it by a longi-
tudinal cut a little to one side of the median dorsal line.

Expose the blood vessels, and observe their contrac-
tions. Note that the contractions pass along the vessels
in successive waves, which mark the course of the blood
in them. Their red color is due to the blood they con-
tain, and the color of the blood is in its liquid part
(plasma), and not in its corpuscles.

These and other contractions, sometimes observable in
the alimentary canal, are performed by the automatic action
of muscles within the walls of the organs themselves.
These, contracting, push the contents forward, much as
water in a rubber tube would be pushed forward if the
tube were drawn tightly between the fingers.

Development. — The eggs of the earthworm are laid in
May or June, and may be found at that time, a number
together, inclosed within ovate, tough, yellowish or brown
capsules, in- loose earth, beneath logs and stones. These
capsules are formed in the following peculiar manner :
Certain glands of the clitellum become very active at this
season, and pour out on the surface of the body a fluid
which hardens into a tough membrane, forming a girdle
about the body. A thick jelly-like fluid is retained
within this girdle, between it and the body. The girdle
is gradually worked forward, toward the head. When

THE EARTHWORM. 139

it passes the openings of the oviducts on segment 14,
ova are discharged into it ; and in passing segments 11
to 9 it receives sperms that have been stored in the
seminal receptacles. When it is passed off over the head,
it closes elastically at both ends, forming a capsule.
Within this capsule fertilization takes place, and the
fertilized ova develop, and give rise to little worms,
which feed upon the nutrient fluid in which they float,
until they are able to make their own way in the world.1

1 Read Darwin's Formation of Vegetable Mould through the Action of
Worms.

MOLLUSKS.

THE RIVER MUSSEL.
(Unio.)

Haunts. — This animal is common in all our rivers and
small lakes. It is found on the bottom, usually partly
buried in sand or mud. As it moves about, it makes a
trail through the mud or sand, — a shallow groove, with
abruptly sloping sides ; and, by observing its track at
the edge of the water, it may often be more easily found.
Occasional specimens may be picked up at the bank,
but usually larger ones will be found farther out. They
may be raked ashore with a long-handled garden rake,
or drawn up with a long-toothed lawn rake from a boat,
or, in warm weather, most rapidly obtained by wading
out on a submerged sand bank and picking them up by
hand. The dead and empty shells strewing the banks
will be a guide to the best places to search for live
specimens.

When a river is falling after a flood, many mussels will
be found close to the banks, and many others may be seen
out on the banks, where they have been left high and dry
by the receding waters, and where they have died. This
is a casualty of a very common kind among the lower
animals.

Specimens collected in the field may be carried home in
a bucket of water, and kept alive in an aquarium impro-
vised from a tub or a water-tight box, with a layer of sev-

140

THE RIVER MUSSEL. 141

eral inches of sand in the bottom and several inches of
water above the sand. Here something of their habits
may be seen.

Study of a Live Specimen. — Take a live specimen in
hand, and note : —

1. That the animal has entirely withdrawn itself
within its shell.

2. That its shell is composed of two equal pieces
called valves.

3. That the valves are hinged together at one side.

4. That they are firmly held together at their free
margins. Try pulling them apart.

5. That there is a central prominence in each valve
(the beak or umbo) near the hinge.

6. That each umbo is a center of growth, with lines of
growth arranged concentrically around it.

Now observe one of the mussels that have been placed
on the sand in the aquarium, — one which, having been
left for awhile to itself, has gotten up on edge and started
to travel. Observe : —

1. That the hinge is up. It is on the back or dorsal
margin.

2. That the free margins of the valve are down. They
form the ventral margin.

3. That they are slightly separated, and that the animal
is partly extended between them.

4. The direction in which the mussel is traveling. Take
some measured observations and compute its rate of speed.

5. That the umbones are nearer the forward or anterior
end. Looking at the moving mussel from behind, the
valve on the right hand is the right valve ; the other, the
left valve.

6. That the animal moves by a succession of pulls.
Find out what does the pulling.

142 MOLLUSKS.

7. That there are two round fringed openings at the
posterior end of the dorsal margin. These are the siphon
openings. If the water be shalloAv enough, there may be
seen near these a play of wavelets on the surface, indicat-
ing currents. Place a drop of india ink or other colored
fluid in the water near these openings, and discover the di-
rection of the currents in each of them. Record the result.

8. That there is an exserted membrane fringing the
free border of each valve all around. This is the edge of
the mantle. Touch it in various places, and note its sensi-
tiveness.

9. That there is a white, flexible, muscular foot pro-
truded downward and forward between the mantle margins
into the sand. By quietly placing a finger horizontally
in the sand in front of the mussel, and directly in its
course, and waiting for the animal to travel over it, you
may discover how the foot is used.

Pick up an active mussel quickly out of the water, and
see how quickly the foot is retracted.

Place a sheet of tin or a pane of glass on the sand, and
lay a mussel on it at its center. Note how the animal
protrudes and uses its foot, in its efforts to rise.

Explain its inability to rise on edge and move away.

Discover by experiment whether the fringes of the
siphons are sensitive to light.

Structure. — In dissecting a river mussel, the first thing
to be done is to get the shell open so as to get at the
animal so securely locked inside. The valves are held
together by two stout, transverse muscles. Select a live
specimen of large size for the first dissection. Place it
for a few moments in water as warm as the hand can
bear. This will relax the muscles. The valves may then
be opened slightly, and a block inserted between them
to keep them so.

THE RIVER MUSSEL.

143

Observe a soft, whitish membrane, with a narrow, dark-
colored, ruffled border lining each valve. It is the mantle.
Loosen the edge of the mantle from the edge of one valve
by pushing a knife blade between the two, and drawing
it entirely around the free border of the valve. Keep
the point of the blade close to the shell. Observe that
the mantle clings to the valve along a line within and
parallel to its margin. Observe that the point of the
knife blade meets with an obstruction near the dorsal sur-

DIAGRAM OF UNIO: u, umbo; h, hinge; s, siphons; small arrows indicate
the direction of the water currents; large arrow indicates direction of
travel, and also depth to which the animal is usually found buried in the
sand in locomotion ; /, foot ; e, edge of the valves ; I, concentric lines of
growth ; m, mantle margins extruded in front.

face, at both anterior and posterior ends : it encounters
the strong muscles which hold the valves together. Cut
these off close to the valve. Notice the valves spring
apart when these are severed. Free the one valve from
all connection with mantle and muscles, and turn it back
like the lid of a watch case.

I. The Different Parts. — Study the following parts,
doing no more dissecting than is absolutely necessary : —

1. The mantle. Observe the thinness and transpar-

144 MOLLUSKS.

ency of its inner part, and the sensitiveness and mobility
of its border.

Observe that it consists of two lobes corresponding in
size to the two valves of the shell, and that its border is
continuous from one to the other.

Observe how loosely it infolds the body, and covers it
above and on the sides.

2. The siphons. Observe that the siphon orifices are
formed from the edge of the mantle, and that the adjacent
mantle margins are grown together between the upper and
lower orifices, entirely separating them, and that below
the lower orifice the mantle margins are free. The upper
tube leads out from the cloacal chamber, and is therefore
called the cloacal siphon. The lower opening leads into
the branchial (or gill) chamber, and is therefore called the
branchial siphon.

3. The principal muscles. Observe the severed ends
of the two stout, white adductor muscles projecting ver-
tically through the mantle.

Close beside each of these find the end of a much
smaller, oblique muscle, which was also severed in open-
ing the shell. These two are the retractor muscles. They
retract the foot. Prick the point of the foot, and watch
the posterior adductor muscle. Prick the back part of
the foot, and watch the anterior adductor muscle. If
these were fast to the shell, instead of being drawn down,
they would draw the foot up, as may be seen later by
pricking the retractors of the other side, near their origin,
before severing them from the valve.

In the thickened border of the mantle are many muscle
fibers, to which its mobility is due, and by which it was
attached to the shell along the pallial line.

4. The gills. Turn the loose part of the mantle back
upon the dorsal surface, and expose the gills. They hang
suspended in the branchial chamber at the posterior part

THE RIVER MUSSEL. 145

of the body. Observe that they are thin, ribbed and per-
forated folds of membrane extending longitudinally beside
the body, a pair on either side. Between the two pairs
observe the soft, white, muscular abdomen, extending
downward and forward, and terminating insensibly in the
retracted and minutely wrinkled foot.

Examine the surface of the gills with a lens.

Lift with forceps the lower edge of one of the gills (if
the outer gill appear dark and distended, lift the inner
one), stick a sharp knife or scalpel through it, and make
a vertical slit out to the edge. Then look at the cut edge
of the piece held in the forceps, and see that the gill
membrane is double and V-shaped in cross section, and is
suspended by the arms of the V from above. Insert the
point of a knife blade into the end of the piece held in the
forceps, and split it lengthwise. Then take a small piece
of the single gill membrane thus obtained, and mount, and
examine it (without cover glass) with low power. Note
the shape and arrangement of the openings in the mem-
brane, the location and action of the cilia.

Pass a bristle or other probe into the cloacal chamber
from its siphonal orifice. Observe that this chamber lies
entirely above the gills, and that it has no communication
with the branchial chamber below, except through the gills.

Lay open the cloacal chamber for half an inch by a
single cut with scissors through the wall of the cloacal
siphon. Observe the minute openings leading from the
floor of the cloacal chamber down into the gills. Pass
a bristle into one of these, and observe that it ends blindly
at the lower edge of the gill.

Make a short longitudinal cut through the posterior
part of the attachment of both gills to the cloacal cham-
ber. Then lift with forceps the cut edge of the outer
layer of the outer gill, and observe the numerous septa
or partitions extending transversely between the outer

NEED. ZOOL. — 10

146 MOLLUSKS.

and the inner layers, connecting the arms of the V.
Observe also that the inner layer of the outer gill is
continuous with the outer layer of the inner gill.

Having already observed that the water passes in at
the branchial and out at the cloacal siphon, give now an
explanation of the course it takes, and of the manner in
which it is propelled onward in its course.

5. The blood vessels. Turn the free lobe of the mantle
down again, and loosen the dorsal portion from both
valves. Then pull downward gently on the free lobe so
as to bring the dorsal aspect of the body better into view.
The dorsal portion of the mantle is very thin and trans-
parent, and through it may be seen, in the part that was
directly beneath the hinge, an oval or elongated trans-
parent vessel regularly but slowly pulsating. This is the
ventricle. Pinch up the mantle with forceps, and cut it
away from this region, and the parts will be better seen.
The blood comes to the ventricle from a pair of auricles
located one on either side. Each auricle lies directly
between the gills and the ventricle, and is somewhat coni-
cal in form, with the apex of the cone toward the ventri-
cle. A branchial vein brings the blood from the gills to
the lower end of the auricle. The ventricle is emptied
principally through a pedal artery which curves forward
and downward toward the foot.

Observe that the dark-colored intestine runs directly
through the ventricle, like a draught pipe through a loco-
motive boiler, there being no open communication between
the two vessels.

Observe the pulsations of the heart.1 First the auricle

1 A very satisfactory demonstration of the action of the heart may be
made by cutting away with bone snips the portion of the shell which
immediately surrounds the hinge, and covers the heart, leaving the ani-
mal intact within. A thin-shelled specimen should be selected for this.
If kept under water, or, better, under f-per-cent salt solution, the pulsa-
tions may be observed for a long time.

THE RIVER MUSSEL. 147

swells up with limpid transparent blood from the gills,
and then it contracts and fills the ventricle, which then
contracts in turn, sending the blood out through the pedal
artery.

II. Digestive System. — On either side of the front
part of the abdomen observe two soft triangular flaps
narrowing toward the front. These are the labial palps.
Between them, directly in front, is the mouth, which
leads through a short esophagus into the stomach. The
stomach is surrounded by a dark brown mass called
liver, easily seen when the mantle is removed. The course
of the digestive tract is difficult to trace in a fresh speci-
men, but may be followed more readily in one that has
been hardened in alcohol. Posterior to the stomach there
are several turns of the intestine l before it emerges from
the abdomen to pass into and through the pericardial
cavity, where it has already been noticed running through
the ventricle. It terminates in the cloacal chamber. If
the heart and the part of the intestine posterior to the
abdomen be removed, two dark-colored renal organs will
be seen below them. These organs open below into the
cloacal chamber, and above into the pericardial cavity,
thus connecting the body cavity with the exterior, as do
the renal (segmental) organs in the earthworm.

III. Nervous System. — This will be studied with ex-
treme difficulty in a fresh specimen. It will require
less time and patience if a specimen which has been
hardened in alcohol or by boiling be used. It may best
be studied in a specimen which has been soaked for a few
days in 10-per-cent nitric acid.

Remove the mussel entirely from its shell, and pin it
in a dissecting pan, with its dorsal surface down. Sepa-

1 It may be demonstrated by injecting the alimentary canal through
the mouth with starch mass (see Appendix, p. 284) colored with lamp-
black, and dissecting away the sheet of overlying muscle of one side.

148 MOLLUSKS.

rate the two pairs of gills on the median ventral line, and
find directly beneath the posterior adductor muscle a pair
of yellowish ganglia more or less united. These are the
visceral ganglia. Trace from them as a center a pair of
lateral nerves to the gills, a pair of posterior nerves
to the edges of the two mantle lobes, and a pair of very
long commissural nerves forward, to join a pair of cere-
bral ganglia which lie near the surface at the bases of
the labial palps, on either side of the mouth. From these
ganglia trace a pair of nerves downward to the pedal
ganglia, which lie deeply imbedded where the foot joins
the abdomen. The nerves appear as fine white threads ;
the ganglia are usually more easily seen because of their
yellowish color. These three pairs of ganglia, with their
connecting commissures, constitute the central nervous
system of the mussel, and of a large group of animals of
which it is a type.

IV. Reproductive Organs lie in the posterior part of the
abdomen, one on each side, and each opens by a slit on the
upper surface just above the long commissural nerve traced
forward to the cerebral ganglia.

The eggs of the river mussel are passed into the cavity
of the outer gill, where they hatch, and where the young
are retained for a time. If there be found a specimen in
which the outer gills appear swollen and dark colored,
open one of them, and mix a little of the contents with a
drop of water on a slide. Examine with low power, and
look for little mussels. Draw several of them. Notice
whether any of them move about.

V. The Shell. — Remove all muscles from the inside,
and dirt from the outside, of the shell, and observe again
the concentric lines of growth about the umbones. Hold
the shell up toward the light, and observe the fine lines
radiating from the umbones.

Inside the shell, notice the large adductor muscle scars,

THE RIVER MUSSEL. 149

and close beside them the smaller but often deeper scars
of the retractor muscles. Observe a narrow linear muscle
impression, — a curved line marked around the free border
of the valve, about half an inch from the edge. This is
the line along which the mantle was found clinging. It
is therefore called the pallial line.

Observe the hinge teeth between the dorsal edges of the
two valves. Open and close the valves, and see how these
interlock. They hold the valves together very firmly,
when closed. The blunt, irregular, serrated ones between
the umbones are the cardinal teeth. The long, narrow,
shelf -like folds of pearl beneath the hinge are the lateral
teeth.

Observe that the shell consists of three layers : —

1. An outer layer of horny, brownish, or greenish epi-
dermis, which was continuous at the edges of the shell
with the border of the mantle. The hinge at the back is
a modified and very elastic portion of the epidermis.

2. An inner, pearly layer. This is seen, under magnifi-
cation, to consist of thin, flat layers of pearl, the edges of
which appear as fine, sinuous lines. These cause inter-
ference in the light waves that fall upon them, and give
rise to all the singularly beautiful colors seen within the
fresh shells of some Unios.

3. A darker middle layer, seen, under magnification, to
consist of polygonal prisms placed perpendicular to the
surface of the shell.

Dissolve out the mineral matter from a shell by placing
it for a time in dilute acid. What properties has the
remaining part ?

Burn out the animal matter from a number of shells.
Weigh them before throwing them into the fire and after
taking them out, and note the proportional loss. Pick a
burned shell to pieces, and note the disposition of layers
in its thickened part.

150 MOLLUSKS.

The Life Process. — Since, in connection with each of
the organs studied, the work it has to do has been already
mentioned, it only remains to summarize these various
operations as parts of the process by which the life of the
animal is maintained.

I. Nutrition. — This part of the process is dependent
to a marked extent upon the aquiferous system, and the
water currents it keeps up. The siphons are the most
conspicuous part of this system ; but the cilia lining the
openings into the gills, although the least conspicuous,
are the most important part of it, for it is by their lash-
ing action that the water is drawn into one siphon and
driven into and through the gills and out through the
other siphon. In the gills the usual exchange of car-
bonic-acid gas for oxygen takes place between the
water flowing freely over the thin-walled blood vessels
distributed throughout the gills and the blood flowing
inside those vessels. In other animals that breathe by
gills this exchange seems to be the sole purpose of the
water currents, but in the mussel these currents also assist
in the procuring of food and in excretion. The food con-
sists chiefly of low plant organisms found free in the water.
These are carried into the branchial chamber by the enter-
ing current. The current does not all enter the gills, but
a branch of it is driven forward toward the anterior end
of the body, and the bits of food carried along by it are
directed by the labial palps into the mouth. Excreta are
expelled with the current passing through the cloacal
siphon. Thus all the operations connected with nutrition
are more or less directly dependent on the water currents.

For convenience in summarizing, we may say that ru-
trition is effected in the river mussel through the agency
of the following interdependent systems of organs : —

1. A digestive system, comprising the alimentary canal
and the large accessory gland called liver.

THE RIVER MUSSEL. 151

2. A circulatory system, comprising (1) veins which col-
lect blood from all the tissues and convey it to the gills ;
(2) other (branchial) veins, which convey the aerated
blood from the gills to the heart ; (3) auricles, which
receive the blood from the gills, and, contracting, pass it
on into (4) the ventricle, which in turn contracts, and
drives it through (5) the arteries, out into the tissues
again.

Four important changes take place in the blood during
its course through the body : —

(a) It is enriched by the digested food, which it
receives directly through the walls of the alimentary
canal.

(6) In the tissues the cells with which it comes in con-
tact take from it whatever material they need for growth,
and return to it their waste products of oxidation.

(<?) On its return to the gills, part of the blood passes
through the renal organ, where nitrogenous waste products
are taken from it for excretion.

(d) In its passage through the gills it loses waste car-
bonic acid, and absorbs oxygen.

3. A respiratory system, comprising the gills, with
their numerous small blood vessels.

4. An aquiferous system, comprising the siphons and
the ciliated passageways through the gills.

5. An excretory system, of which the renal organs and
the gills comprise the most important part.

Metabolism is in this, as in all other animals, performed
by the individual cells.

Certain of the mantle cells take calcium carbonate from
the blood, and deposit it as a precipitate, thus forming the
mineral part of the shell. The soft inner part of the
mantle thus continues through life to deposit on the inside
of the shell a layer of pearl. If a foreign body get into
the substance of the mantle, or get between the mantle

152 MCXLLUSKS.

and the shell, it will be covered with a layer of pearl.
This is the way that the pearls of commerce are produced ;
and inferior pearls are often found in dissecting our com-
mon river mussels.

II. Reproduction. — The eggs, as already noticed, are
fertilized, hatched, and the young are nurtured for a time
in the outer gills of the female. Their number is pro-
digiously great. The young, when found in the gills
(then called glochidicC), differ very markedly in appearance
from the adults, in their widely gaping, triangular valves,
hooked at the tip. When they are expelled from the gills
into the water, to shift for themselves, they fasten them-
selves by means of these hooks to some floating or swim-
ming object, preferably to the fins of a fish or to the tail
of a tadpole, where they lead for a time apparently a para-
sitic existence. Later they fall to the bottom, and begin
life independently. Doubtless multitudes of those that
fall to the bottom are buried in the shifting mud and
sand ; many more are eaten by other aquatic animals be-
fore their shells have attained sufficient size and strength
to afford them protection ; and even in adult life some are
eaten by minks and otters, and very many are left out on
the banks by receding floods to die of evaporation : so
that the vast number of eggs produced appears, in the
end, after taking all casualties into account, to be only
sufficient to maintain for the species its accustomed num-
bers, and to keep up the biological balance in the life of
the river beds.

III. Voluntary Motion. — The muscular system serves
the river mussel the double purpose of performing its
movements, and of holding it in its shell. The strongest
muscles are the adductors, which close the shell. Opposed
to these is only the hinge ligament, which, upon their
relaxation, opens the shell automatically.

The foot is principally a muscular organ consisting of

THE KIVER MUSSEL. 153

longitudinal fibers of the oblique pedal muscles, capable
of retracting it, or of moving it sidewise, and of circular
fibers capable of extending it. It is adapted for plowing
through mud or sand, and for no other kind of locomotion.
Only by sinking the foot into mud or sand is the animal
able to rise to its erect position. Blood is forced down
the pedal artery through the center of the foot into its
point, as an additional aid to its extension; and by the
distension of its tip a firmer hold is obtained in the sand,
to aid in locomotion. The flat muscle of the mantle is
capable of moving its entire margin.

IV. Sensation. — The nervous system of the mussel
consists of the three pairs of ganglia already noticed, and
of nerves radiating from each pair extending to every
vascular part of the body, giving sensibility to. every part,
and furnishing nervous communication with every other
part.

The senses are not very acute. Touch is well devel-
oped, and is most acute in the point of the foot and in the
mantle margin, particularly in the part which forms the
outer border of the siphons. Taste and smell are prob-
ably developed slightly, and aid the animal somewhat in
the selection of food. Sight and hearing are developed
but feebly, if at all. There is a so-called ear sac in
the foot, near the pedal ganglia. That it is an organ of
hearing is very doubtful. It seems more probable that it
is an organ of the sense of equilibrium, enabling the ani-
mal to distinguish between a flat or inclined position and
an erect position. Though incapable of hearing sound,
the animal may feel vibrations when they become suf-
ficiently intense. The siphon fringes are so sensitive to
light, that a heavy shadow thrown across them will cause
them to be retracted.

The instincts of this animal are of a low order : they
seem to be limited to self-preservation and the selection

154 MOLLUSKS.

of food. A complete retreat within its shell is its only
means of defense. But the hard, closed shell is protec-
tion, strong in proportion as the instincts are weak.

The river mussel is a representative of the group Mol-
lusca (or soft-bodied animals).

Other Mollusks. — There are three forms of snails,
very common throughout the interior : (1) land snails,
found under the fallen leaves and decaying logs in hard-
wood groves, and easily collectible in warm weather ;
(2) pond snails, found on the submerged vegetation of
ponds throughout the year; (3) river snails (opercu-
lates), found in the same situations with river mussels.
The most available of these for study in the winter is the
pond snail.

THE POND SNAIL.

(Limnea.)

Haunts. — This animal may be found in almost every
natural small pond, adhering closely to the stems and
leaves of aquatic plants, to the dead stems of " cat-tail
flags," to sticks, boards, old boots, etc. ; in fact, to almost
anything that may have chanced to get into the water.
These things may be slowly drawn out of the water, and
the snails picked off them by hand. . The only apparatus
necessary for collecting pond snails is a small vessel of
water to carry them home in.

Aquarium Study. — They may be kept in an aquarium,
or, better for study, in a bowl, or dish, or fruit jar, in
water. The vessel should be kept clean, and they should
be fed daily with leaves of cabbage or lettuce. They
are very easy to keep ; there is much that is novel
and interesting in their habits that is quite easy of

THE POND SNAIL.

155

observation ; and every student should keep a number
of them awhile for his own study.

In a fully extended specimen, observe, first, the three
distinctive and obvious characters of mollusks: (1) the
foot beneath the body, (2) the mantle covering its back,
and (3) the shell secreted by the mantle. The foot is the
broad, flat disk on which the ani-
mal creeps ; the mantle edge is just
visible within the edge of the shell.

The Shell. — Study the shell.
Observe that it is in one piece
(univalve), whereas the shell of the
mussel is in two pieces (bivalve).
Its parts are named as follows : —

1. The apex is the pointed end.

2. The aperture is the opening
at the large end.

3. The lip is the outer edge of
the aperture.

4. The lines of growth are par-
allel to the lip.

5. The suture is the spiral groove
on the outside.

DIAGRAM OF POND SNAIL :
a, apex; s, suture; sp,
spire; I, lip; 1, 2, 3, 4,
whorls of shell, the larger
ones showing lines of
growth (the aperture is
filled with the body of
the animal) ; c, collar
(edge of mantle) pro-
truding beneath the lip;
h, head;/, foot; e, eye;
t, tentacle ; 6, breathing
aperture.

6. The spire comprises all the whorls or turns of the
shell taken together.

7. The columella is the axis of the spire.

If, when holding the shell with the apex toward you,
the whorls, as they proceed from you, turn to the right,
above the axis of the spire, the spire is right hand, or
dextral ; if they turn the other way, it is left hand,
or sinistral.

In the river snails an operculum will be found, — a lid-
like piece which completely closes the aperture when
the animal is retracted within the shell.

156 MOLLUSKS.

External Features. — Study the external features of the
snail by careful inspection of live and active specimens
moving about in a glass vessel. Observe that the foot
is bilaterally symmetrical, that it tapers to an obtuse
point behind, that it is squarish or truncated in front,
and that its foremost part is marked off from the rest by
a transverse groove on the ventral side. Observe, on the
dorsal side of this part, a pair of long motile and retrac-
tile tentacles, 'and a pair of eyes appearing as dark spots at
their bases. On the ventral side of this part is the mouth,
easily seen in a specimen that is crawling on the side of
the glass vessel.

Observe the long, flexible body, extending upward from
the foot into the spire.

Observe that the mantle is thickened at its edge where
it lines the edge of the aperture. This part is the collar.

Observe in snails, at the surface of the water, a conspicu-
ous orifice in the collar at the right side of the body.
This is the respiratory orifice. The mantle is pushed in
at this point, and distended within into a sort of bag-
like rudimentary lung, in the walls of which the minute
blood vessels are distributed.

Habits. — Study the actions of the snail. How is its
peculiar crawling, creeping, or gliding locomotion effected ?
Note that it moves with equal ease on the bottom, on the
sides, and in inverted position along the surface of the
water. It will be seen to come to the surface at more or
less regular intervals for a fresh supply of air, and may
sometimes be seen expelling a bubble of impure air before
taking in a fresh supply. It will be seen to close its respir-
atory orifice before going down again. Occasionally a
snail may be seen to let itself down from the surface
by a floating thread of mucus secreted by glands in the
foot. When a number of snails going in opposite direc-

THE POND SNAIL. 157

tions meet, one may sometimes be seen using its shell as a
means of offense, clearing its track by striking about with
its spire. If the mouth of one that is crawling on the
side of glass be watched with a lens, its ribbon-shaped
radula, covered with rows of minute, recurved teeth, may
sometimes be seen slightly protruded. By means of
muscles attached at both ends, the radula is drawn back-
ward and forward like a rasp across the objects on which
the snail feeds. Cabbage leaves on which the snail has
been fed will show areas which have been " scraped " by the
radula. All these things and many more may be seen by
carefully watching a few live snails in a tumbler of water.

Development. — The eggs of the pond snail are very
easily procured, and they offer exceptionally fine advan-
tages for the study of those stages of development which
immediately succeed fertilization. They are laid in gelat-
inous, transparent capsules, half an inch to- an inch in
length, flattened, and linear or oblong in outline. After
a few snails have been kept a short time in a small vessel
of water with their appropriate food, these egg capsules
may be looked for on the bottom and sides of the vessel,
or closely adherent to the stems or leaves of plants placed
in the water. They are so transparent as to be easily
overlooked.

Detach one of these egg capsules by pushing a thin
blade between it and its support. Place it in a watch glass
with a little water, for examination.

Examine it with a lens, and draw it. How many eggs
does it contain? How are these eggs arranged in the
capsule? What is the shape of each egg?

Note that each egg contains a minute oosperm (or fer-
tilized ovum), which is less transparent than other parts.
It is the development of this oosperm that especially
invites our study.

158 MOLLUSKS.

I. Segmentation. — Place the watch glass upon the stage
of the microscope, and examine the eggs with IOAV power.
If a freshly laid capsule has been obtained, the oosperm
of each egg \vill appear perfectly spherical in form, and
slightly yellowish in color, from the large number of
minute food-yolk granules distributed through it. If it
be kept covered with water, and watched at intervals of
half an hour or less during the first day, and at intervals
of half a day thereafter until hatched, the following
changes may be confidently expected : —

The oosperm is practically a single large cell, formed
by the fusion of two specialized reproductive cells called
ovum and sperm. The fusion of the two we have
already called fertilization, and have said that it is essen-
tially the same process in all animals except the pro-
tozoans. Fertilization necessarily precedes and initiates
the changes which we are now to study.

The oospeima divides, and becomes two spherical cells
instead of one ; after a short quiescent period, the two
divide, and become four ; after another short period, the
four divide, and become eight ; and so on, with decreasing
regularity. This process is called segmentation.

If all the eggs in a freshly laid capsule be examined,
some of the oosperms will be sure to show a lighter and
a darker side. This is owing to a greater accumulation
of yolk granules at one side of the sphere. Some will
show, also, one or two minute transparent polar bodies
pushed out from the middle of the lighter side. That pole
of the sphere at which they appear is called the formative
pole. In segmentation, a groove first appears at the forma-
tive pole, extends meridionally around the oosperm, and
deepens until two separate cells are formed. These cells
appear to partly coalesce again, before the next division.
Then a second groove starts at the formative pole, and ex-
tends meridionally around the two cells at right angles to

THE POND SNAIL. 159

the first groove, and deepens until the two cells are divided
into four. Then an equatorial groove at right angles to
both first and second grooves divides the four cells into
eight. This last division is an unequal one, however ;
for the groove is not at the equator of the sphere, but
nearer the formative pole. It therefore pinches off four
small cells at the formative pole, and leaves four large
ones, composing the greater part of the sphere.

It must be observed here that these grooves are but the
external evidence of processes going on inside. They are
the result, and not the cause, of the division. The cell
material separates into two portions ; and the two portions,
moving apart, leave grooves between.

After the eight-cell stage has been reached, the cells
divide with less regularity. The small, active cells, of
nearly clear protoplasm, at the formative pole, divide
very rapidly ; the large, yolk-encumbered cells divide very
slowly, so that the later stages in segmentation are ob-
scured, and sixteen-cell, thirty-two-cell, sixty-four-cell,
etc., stages are not discoverable. But the one-cell, two-
cell, four-cell, and eight-cell stages are very plain, and
easily followed ; and these illustrate the process of seg-
mentation.

II. Later Stages. — Two later stages, which are com-
mon to most of the higher animals, may be observed in
the development of the snail. These are : —

1. The Uastula stage, in which the segmentation pro-
cess results. In this stage there is a hollow sphere of
cells, its walls a single layer. The Uastula is not quite
spherical, and its walls are not of uniform thickness,
being formed of a few large cells on one side, and of
more numerous small ones on the other.

2. The gastrula stage, in which one side of the hollow
sphere has become pushed in, as it were ; the other side
extending its edges, forming a cup-shaped depression.

160 MOLLtTSKS.

This depression deepens, its aperture narrows, and a more
or less spherical form is again assumed. It is obvious
now that the sphere has double walls, and that its cavity
has an open communication with the exterior. It is now
called a gastrula.

Compare the gastrula, as to the type of its structure,
with a hydra stripped of its tentacles.

The later stages within the egg are not such as are
common to most of the higher animals. They are difficult
of study, and they will not be described here in detail.
The student will readily see that the gastrula grows,
transforms into a creature less simple, and begins to turn
round and round in the albumen of its egg by means of
a circlet of cilia which it has acquired. As it increases
in size, dorsal and ventral surfaces become distinguish-
able, a transparent matrix of a shell appears, and a foot,
with a head imperfectly marked off at its anterior end.
A pair of blunt processes at the sides of the head fore-
shadow tentacles, and two very black pigment spots repre-
sent the eyes. A pulsating heart becomes visible through
the shell, and near it a tubular esophagus ; and by the
time it has eaten all the egg contents, and is ready to
come forth, most of the adult structures are recognizable.

It will, no doubt, be more convenient to find all these
stages in eggs taken from different capsules than to try to
follow the transformations through with a single capsule.
If a goodly number of capsules are obtainable, it is quite
possible to find all these stages at one time.

The young snail within the egg is called an embryo,
and all the transformations by which it comes, from being
a simple, undifferentiated cell, to the possession of perma-
nent and serviceable organs, constitute its embryology.*

1 Try on' s Structural and Systematic Conchology is recommended for
reference, and for use in making a further study of mollusks.

VERTEBRATES.

THE CATFISH.

The following directions are written with special refer-
ence to the common channel cat or white catfish (Ictalu-
rus punctatus), but they are general enough to be applied
without difficulty to the study of any other common cat-
fish.

THE CHANNEL CAT (after Todd, by permission).

Description. — The channel cat is abundant in all oui
rivers and small streams. It has the characteristic cat-
fish contour of body, which needs to be seen but once
to be remembered. It is olivaceous above, and whitish
below, with silvery sides ; and its tough, scaleless skin is
sprinkled with many small, round, dark olive spots. It
may be angled for at the proper season, and may be
obtained in the market or from fishermen at all seasons,
for it is a good food fish.

Like all the other catfishes, it is very tenacious of life,
and there is little trouble in obtaining live specimens from

NEED. ZOOL. 11 161

162 VERTEBRATES.

a distance, when this is necessary. Specimens are often
seen alive in the markets, in cool weather, twenty-four
hours or more after they have been taken from the water.

Aquarium Study. — Study a live specimen that has
been placed in an aquarium, or tank, or tub of water.
Observe its form, its coloration, its markings, its method
of getting about. What adaptations can you discover in
its form to locomotion in water ? To living on the muddy
bottoms in river channels ?

Observe the large eyes, the mouth' opening directly for-
ward, the long barbels at the corners of the mouth, a
pair of smaller barbels above and behind the mouth, and
two pairs below and behind the mouth.

Observe on either side of the head, where it joins the
body, a wide strip of membrane overlapping a long ver-
tical slit. Notice the regular opening and closing of this
aperture, and also of the mouth, and note the concerted
action between the two. Place a drop of ink in the water,
close in front of the mouth, to discover the direction of
the current of water through these openings.

I. Fins. — Four of these are paired fins, — the pair at
the sides of the body, just back of the head, are the
pectoral fins ; the pair low down on the sides of the body,
much farther back,- are the ventral fins, — the others are
single or unpaired fins. The two fins on the median dorsal
line are dorsal fins. The one on the median ventral line is
the anal fin. The large one at the posterior end of the
body is the caudal fin.

As the fish swims about, watch it to discover the use of
each of these fins. That the large caudal fin is the one
principally concerned in locomotion will be seen at once.
To learn the use of the pectoral and ventral fins, catch the
fish with the hand, avoiding the sharp spines at the front
of pectoral and anterior dorsal fins ; fold the pectoral fins

THE CATFISH. 163

backwards, flat against the sides of the body; pass a rubber
band back over the head and around these fins, to keep
them so. Keep the fish under water while attempting
to depress the pectoral spines, for in air it will keep
them rigidly erect. Pass another rubber band about the
ventral fins. Then liberate the fish, and watch it. What
position does its body assume ?

Release the paired fins, and fasten down the dorsal and
anal fins with rubber bands. Liberate the fish again, and
observe how it gets along without the use of these fins.
What kind of a course does it take through the water ?

II. Circulation seen in Fins. — Observe that the broadly
expanded part of the fin is very thin and transparent, and
that it is traversed by minute blood vessels, which appear
as fine red streaks. Connecting these that are visible to
the unaided eye, are many smaller capillary vessels in
which the circulation can be advantageously studied with
a microscope, as follows : —

Wrap the fish in a wet towel, leaving the caudal fin
exposed, and place it on a low box beside the microscope,
with its caudal fin extending across the center of the micro-
scope stage. Spread the fin out flat on a glass slip upon
the stage, so as to bring a thin portion of it into the field,
and examine it with low power. If the fish refuses to lie
quietly, pour a little chloroform on the towel near its
mouth.

Observe the conspicuous, dark, irregular pigment cells
scattered throughout the epidermis of the fin.

III. Blood Vessels. — The larger ones are of two kinds :
(1) arteries, bringing blood out into the fin, and (2) veins,
conveying the blood back to the body again. The smaller
ones are the capillaries, connecting the arteries with the
veins, aiid distributing the blood throughout the tissues of
the fin.

Observe that the blood consists of a fluid plasma, in

164 VERTEBRATES.

which float numerous corpuscles. Observe that the blood
appears red in the arteries and veins, where the corpus-
cles are accumulated, but only slightly reddish or yellow-
ish in the capillaries, where corpuscles form but a thin
layer.

Does the blood travel faster in the arteries and veins, or
in the capillaries ?

Place a bit of cover glass over a very thin portion of the
fin, and study it with higher power. Find two kinds of
corpuscles in the blood : (1) red corpuscles (red only when
a number are seen together), very numerous, and carried
along in the center of the larger currents closely packed
together ; and (2) white corpuscles, resembling the amoeboid
corpuscles of the mussel and earthworm, not very numer-
ous, and usually seen trailing along the edges of the blood
currents, or escaping out into the tissues.

External Features. — Kill the fish with chloroform, and
make a closer study of its external features.

Observe the exact correspondence of the two sides, —
perfect bilateral symmetry.

Observe the broad head, dorsally depressed, the absence
of neck, and the long, tapering body.

On the upper surface of the head, just behind the mouth,
find four nostril openings, the posterior pair close behind
the barbels of this surface. Probe these openings with a
bristle to see whether they have any connection with each
other or with the mouth.

Examine the bases of the large barbels at the corners
of the mouth, to find the bones which extend out into
them from the head.

Examine the eyes. Are there any eyelids or other
means by which they may be closed ? Press on the edges
of the eyeball to discover how far it may be turned to look
in different directions. Press with a finger against the

THE CATFISH. 165

roof of the mouth inside, and observe how the eyeball is
affected.

I. The Mouth. — Stretch the mouth wide open, and look
into it. Observe a band of numerous sharp, small teeth
extending across its margin, above and below. Rub a
finger across these teeth to discover in what direction
they point. What advantage to the animal in their incli-
nation ?

The bone which forms the border of the lower jaw is
called the mandible. The bone of the upper jaw which
bears the teeth is called the premaxillary. In other fishes
several- bones of the roof of the mouth bear teeth. One
of these is the maxillary, which in the catfish is reduced
to the pair of rudiments already found supporting the
bases of the lateral barbels.

The tongue is a slight angular elevation on the floor of
the mouth. Its boundaries are marked out by correspond-
ing grooves on the lower surface of the head.

The posterior funnel-shaped part of the capacious cavity
seen on looking into the mouth is the pharynx. The phar-
ynx tapers into the esophagus "in the distance." On
the floor of the pharynx are two large prominences cov-
ered with teeth. Rub a finger across these teeth to dis-
cover their direction.

On either side of the pharynx are the gill arches, bear-
ing the gills on their outer convex edges, and separated
by five vertical slits. Pass a pencil in at the mouth, and
out through one of these slits to the exterior. On the
outside observe that the pencil has lifted a semicircular
flap, which is divided by an oblique groove into two por-
tions. The lower marginal portion is the operculum, and
the upper anterior portion is the prce-operculum. The
latter is directly behind the eye, and forms the cheek
of the fish. The inner surface of the operculum is cov-
ered by a soft lining membrane called the branchiostegal

166 VERTEBRATES.

membrane, which is supported by bony rays called the
branchiostegal rays (or simply branchiostegals) . When
the operculum is lifted, the four vertical series of red
gills may be seen inside. They may be studied more
advantageously after dissection.

Observe a longitudinal lateral line on each side of the
body of the fish.

II. Structure of the Fins. — Study the structure of the
fins. Each is made up of a double fold of membrane sup-
ported (except in the posterior dorsal fin) by bony rays.
The rays are wanting in the posterior dorsal fin, and
usually fat is deposited between the folds of membrane,
whence it is called an adipose fin. The first ray in each
of the pectorals and in the anterior dorsal fin is hard and
unjointed. It is developed as a stout, sharp-pointed spine,
with two serrated edges. It is articulated with the bones
of the pectoral arch by a beautiful joint, which secures it
great rigidity when erected, and makes it a formidable
weapon of defense. The other rays are soft and jointed.
Examine them carefully with a lens. Observe that they
are branched or split into parallel, jointed strips at their
outer ends. Make an enlarged drawing of one of the
pectoral fins, and another of the caudal fin.

The two pairs of paired fins are homologous with the
two pairs of limbs of higher animals. The pectoral fins
are articulated upon a bony pectoral arch and the ventral
fins upon a smaller and more rudimentary pelvic arch,
which in the catfish is unconnected with other parts of
the skeleton.

Dissection. — Dissect the fish under water, and study
its internal structure. If a prepared skeleton be at hand
for reference in locating bony parts, it will be of great
assistance in the following work. With a pair of stout
bone snips or shears, or with a hatchet, cut off the dorsal

THE CATFISH. 167

spine, so that the fish may be placed on its back in the
water. With forceps pinch up a transverse fold of the
tough skin of the ventral surface opposite the anterior
dorsal fin, and cut through the fold with sharp scissors.
Continue the cut backward to the vent, and forward to
the bones of the pectoral arch, taking care not to injure
or displace any of the organs which lie directly beneath
the thin body wall. Turn back the flaps and expose
these organs. Observe a silvery membrane, the perito-
neum, lining the body cavity.

Internal Features. — The large red organ close up under
the pectoral arch is the liver. Two conic-pointed lobes
run from it forward and downward ; and two broad, flat
lobes extend backward. Turn these latter forward, and
observe under the one on the right side of the body a
capacious yellow gall bladder.

Under the other, the left lobe, the esophagus extends
backward to the stomach, which lies entirely posterior to
the liver. Pass a probe into the stomach from the mouth.
The intestine arises from the left side of the stomach, and
curves forward and to the right side, and posteriorly around
the stomach, and makes a number of irregular turns in
passing through the posterior part of the body cavity.

Behind the stomach it is partially concealed by the
reproductive organs, — whitish organs in the male ; large,
yellowish organs in the female, — varying much in size
with the age of the specimen and with the season.

Observe that the intestine is looped up, and held in
place by a transparent membrane (the mesentery). Lift
this, and observe the blood vessels in it. Observe the
blood vessels and the nerve branches spread out over the
anterior end of the stomach. Turn the stomach over to
the right side, and observe an elongated, narrow, white
organ, the pancreas, lying along its dorsal side.

168 VERTEBRATES.

Observe two ducts entering the intestine together, near
its origin, appearing to come directly from the liver.
One of these comes from the gall bladder, and the other
from the pancreas. The former may be recognized, if dis-
tended with bile forced into it by squeezing the gall
bladder. The other should be traced from its origin by
dissection.

Posterior to the pancreas is a conspicuous dark-red
organ, abundantly supplied with blood vessels, — the
spleen.

Remove the reproductive organs. Cut through the
bones of the pectoral arch. Open wide this incision by
pressing downward on both pectoral spines at once.
Wash out any blood that may have flowed from the
last incision. Turn backward the anterior lobes of the
liver, and observe that the peritoneum rises at this point
to meet the pectoral arch, and is perforated by the esoph-
agus, and by the blood vessels extending forward from
the liver. Trace the blood vessels through it to the
heart. In the heart observe three principal divisions:
(1) a postero-lateral, irregular, thin-walled part, the
auricle ; (2) a larger, oval, muscular, strongly contractile,
central part, the ventricle; (3) a smaller, oval, anterior
portion of lighter color, and noncontractile, the arterial
bulb. This is continued forward into the branchial artery,
which soon divides, sending one branch (aortic arch) to
each gill.

Cut off the branchial artery at its origin, and remove
the heart. Cut off the esophagus close to the pharynx.
Notice how muscular its walls are. Remove the digestive
tract entire, beginning with the esophagus, and proceed-
ing posteriorly, cutting only the peritoneum where it
meets the body wall. Observe other internal organs
lying dorsal to the peritoneum. Central among these is
a large, white bag filled with air, the air bladder or swim-

THE CATFISH. 169

ming bladder, an organ by means of which the specific
gravity of the fish may be increased or diminished at will.
Find a duct connecting it with the esophagus. In a
few fishes its walls contain capillary blood vessels in which
the blood is aerated. It is homologous with the lungs of
higher animals.

In front of the air bladder is a dark, reddish-brown
organ called the pronephros (or head kidney). Its function
is not well understood.

Cut the duct of the air bladder, and lift out the diges-
tive organs. Three parts of the intestine not heretofore
noticed are easily distinguishable : (1) A wide portion
immediately succeeding the stomach, called, the duodenum.
Into this part the ducts from the liver and from the pan-
creas enter. (2) A narrow, much convoluted portion, not
well marked off from the preceding, called small intestine.
(3) A wider terminal portion, well marked off from the
latter by a hoodlike fold in the walls of the canal, and
called large intestine.

Entirely remove the peritoneum, and find the special
excretory organs, the kidneys, lying dorsal to its posterior
portion. These are of a dark purplish or brownish color,
and are more or less united into one mass. They send
back a duct to communicate with a small white urinary
bladder beneath the vent, and to open to the exterior by
a separate pore a little farther back.

A string of irregular, fatty bodies is often found ex-
tended lengthwise on either side of the median line, near
the kidneys.

The Axis of the Body. — Remove all these organs, and
observe the bones, now partially laid bare on the dorsal
side of the cavity they occupied. A chain of bones con-
stituting the spinal column extends along the median line
from the head to the posterior end of the body. The

170 VERTEBRATES.

separate bones of the spinal column are the vertebrce.
The slender, curved bones extended laterally, a pair
from each vertebra, are the ribs. Between the ribs
observe the white spinal nerves, coming out from the
spinal cord, which is a part of the central nervous system
located in a hollow that extends longitudinally through
the center of the spinal column.

Gills. — Study the gills. Continue the ventral incision
forward exactly on the median line to the mouth. The
narrowed, anterior portion of the chest between the gill
openings is the isthmus. Observe the branches of the
branchial artery going to each gill. These will be better
seen in an injected specimen.1 Deepen the cut until it
divides the upper wall of the pharynx, the floor of the
mouth, and the mandible. Then draw the edges of the
cut apart, and expose the white gill arches. Observe
the vertical series of teeth on the concave side of each
arch. These are the gill rakers. Note their position, and
the size of the teeth on the different arches. What is
their probable use ?

Raise and depress the floor of the mouth of one side,
and study the action of the gill arches and the rakers.
Observe the joints in the arches.

Cut through the isthmus of one side between the first
gill and the branchiostegal membrane, and expose the red
gills on the back or convex side ^ of the gill arches. Ob-
serve that they are in a double row on the back of each
arch.

Find on the branchiostegal membrane an elongated
reddish patch, which is a rudiment of an anterior gill.
With sharp scissors cut out of a gill arch a thin trans-
verse section bearing one or two pairs of gill filaments,
and examine the section under lowest power of a micro-

1 See Appendix, pp. 284, 285.

THE CATFISH. 171

scope. Observe in the groove on the gill-bearing surface
of the arch the two blood vessels, branches of the branchial
artery and vein. Observe the distribution of the minute
blood vessels in the gill filaments. Examine the fifth gill
arch. How does it differ from the other four ?

The Dorsal Surface. — Turn the fish over. The bones
of the head constitute the skull. Observe that the thick,
dark skin of the dorsal surface rests directly upon the top
of the skull. Find a narrow backward process from the
skull extending to the dorsal spine.

Cranium and Cranial Nerves. — Remove the skin from
the right side of the body and head, and from the whole
upper posterior portion of the skull. Then cut away the
top of the skull and expose the brain. Remove the bone,
with great care not to injure the soft, nervous tissues be-
neath it. The bony cavity in which the brain lies is the
cranium. When the top of the cranium is cut away, it
will be seen that the white brain does not fill the cranial
cavity, and that it is surrounded within the cavity by a
transparent, semifluid substance.

Study the brain as to its general features.

Observe that it tapers posteriorly into the spinal cord,
which has been already noticed, extending through the
spinal column.

Observe the nerves that start out from the brain. Aris-
ing within the cranium, these are called cranial nerves.
Observe that the cranial nerves are paired. Several pairs
of them may be easily distinguished. The two extending
forward from the brain nearest the median line are the
olfactory nerves, or nerves of smell. Cut away its bony
covering, and trace one of these to its termination in an
olfactory bulb, beneath the communicating nostrils.

The Optic Nerve and the Eye. — Just behind the olfac-
tory nerves is a larger pair of optic nerves extending direct

172 VERTEBRATES.

to the eyes. Trace the course of one of these. Examine
the location and attachments of the eyeball. The bony
socket in the skull in which it rests is the orbit. Find
six delicate whitish bands of muscle extending outward
from the orbit, and attached to the sides of the eyeball.
Observe that four of these are straight, and two are
oblique, in their attachment ; and that all are in pairs,
opposed in their action. Determine in what direction the
contraction of each would move the eyeball.

A small cranial nerve (the oculomotor) is distributed
to these muscles.

Cut away the muscles, and observe that the optic nerve
gives off no branches, but runs directly into the posterior
part of the eyeball. It is the nerve of sight.

Observe the tough outer coat (sclerotic coat) of the eye,
transparent over its anterior portion, where it is called
cornea. Looking at the eyeball from the front, observe
a dark hole (the pupil) through which the light enters the
black-lined eyeball, and around the pupil a motley colored
circular band (the iris) . If the eye be cut open, the clear,
double-convex crystalline lens will be found suspended in
the humors of the eye. It is the part which brings the
rays of light to focus on the terminations of the optic
nerve, and causes sic

Other Cranial Nerves. — Behind the optic nerves, a
pair of large, conspicuous nerves (the trigeminal nerves)
will be seen extending forward, and sending off large
branches to the upper jaw, barbels, palate, etc. Some of
its branches may be easily traced. A pair of large
nerves arise from the posterior part of the brain, and
extend posteriorly into the body cavity. These are the
vagus nerves, whose branches have already been seen dis-
tributed over the anterior wall of the stomach.

Between the vagus nerves, which extend posteriorly,

THE CATFISH. 173

and the several pairs, which, we have seen, extend ante-
riorly, are one or more pairs which extend laterally, and
send branches to a pair of thin-walled swellings at the
base of the hinder part of the skull. These swellings
are the ear capsules. Each of these, if cut open, will be
found to contain a membranous sac filled with liquid in
which floats an ear bone. Each is an organ of hearing,
capable of being affected by vibrations, which are so
readily transmissible through water.

Make a drawing of the brain and cranial nerves in
place, as seen from above.

The Brain. — Cut off the cranial nerves half an inch
from the brain. Lift out the brain, place it in alcohol,
and study to make out its parts.

1. Looking at the dorsal surface of the brain, observe
*a large, squarish, anterior division of softer, more satiny
appearance than the rest, divided by a shallow median
groove into two lateral halves. This is the cerebrum, and
its halves are the cerebral hemispheres.

2. Looking at the ventral surface of the cerebrum,
observe two conical swellings at the base of the olfactory
nerves. These are the olfactory lobes, the foremost portion
of the brain.

3. Close behind the cerebrum are the two smooth,
roundish optic lobes, which are continued downward into
two inferior lobes, that are easily seen from one side or from
below. Observe the optic nerves taking origin from this
part, and crossing ere they leave the cranium. Which side
of the brain receives impressions through the right eye ?

4. On the median dorsal line, close behind and above
the optic lobes, observe a conspicuous, roundish single
portion, the cerebellum. This part extends backward and
downward in two posterior lobes, which surround a deep
median depression, the fourth ventricle.

174 VERTEBRATES.

5. That portion of the brain below and behind the
cerebellum is the medulla. It tapers posteriorly into the
spinal cord.

Preserve this brain for comparison with that of other
animals yet to be studied.

Muscles of Body Wall. — Make a longitudinal cut close
beside the dorsal fins, and down to the spinal column.
Extend this incision backward to the caudal fin, and for-
ward to the pectoral arch. Remove the great flap of flesh
thus partly freed from one side, dissecting it away from
the ribs and from the inferior projections of the vertebrae
posterior to the ribs. Observe the arrangement of the
white bands of muscles, of which it is principally com-
posed.

Separate two of the vertebrse, and find the spinal cord
extending longitudinally through them.

Plan of Structure. — Consider well the arrangement of
parts as you have found them in the fish. Here i" a new
plan of structure. The hard parts (bones) are inside,
and the muscles are attached to prominences on their
exterior. What general arrangement of skeleton and
muscles have you found in the other animals studied?

The central parts of the nervous system are inclosed
within a bony canal which extends along the dorsal side
of the body. The anterior end of this canal is expanded
into the wide cranium; the remainder of this tube is the
neural canal, which extends backward through the verte-
brse. The part of the nerve center occupying the cranium
is called the brain ; the part occupying the neural canal
is called the spinal cord. There are apertures throughout
the length of this bony tube for the passage of nerves
outward through its walls to all parts of the body.

Ventral to this tube of bone, which holds and protects

THE CATFISH. 175

the central nervous system, is another immensely larger
tube, the body cavity, which contains the organs of nutri-
tion and reproduction. The walls of this latter tube are
largely membranous, but they are in part supported by
the ribs and by the lower bones of the skull. A trans-
verse section of the body of the fish, therefore, shows two
tubes, one above the other. How does this arrangement
of nerve center and nutritive organs differ from the
arrangement studied in insects ? In the river mussel ?

The Bony Skeleton. — A few points respecting the
structure and arrangement of the parts of the bony skele-
ton must be studied here. Use a prepared skeleton for
reference, and study the parts in a disjointed skeleton,
which, if not furnished you, you can easily prepare for
yourself.1

I. The Spinal Column. — Study the spinal column.
This is the most important and characteristic part of
the skeleton. Observe that its constituent vertebrae are
not all alike. Their differences are such as to make two
regions distinguishable in the spinal column. The an-
terior portion extending backward as far as the hindmost
pair of ribs is the body region, and the remaining posterior
portion without ribs is the tail region. Isolate one of the
middle vertebrae of the tail region, taking care not to
injure any of the small bony processes that arise from
it, and examine it. Observe a thick, solid, hourglass-
shaped central portion, concave on both anterior and
posterior faces, and perforated for the passage of the
spinal cord. This is the centrum (or body of the ver-
tebra). Observe a pair of processes arising from the
dorsal surface, one on either side of the median line,
and soon uniting to form a long, sharp neural spine. By
their union they form an arch above the centrum, in which

1 For the method, see Appendix, p. 287.

176 VERTEBRATES.

lies a large artery. A similar pair of processes arise, and
unite in a. similar w.ay on the ventral surface, to form a
long hemal spine. Another large artery is lodged in the
arch at the base of this spine. Notice that both spines
are directed backward. Find four small processes on the
anterior margin, and four on the posterior margin, of
the centrum. These are articulating processes (zyga-
pophyses). They join corresponding processes on adja-
cent vertebrae, and serve to hold the several vertebrae
more firmly together. Study the relation between these
processes in vertebrae that have not been disarticulated.

Draw a vertebra as seen from one side, and as seen from
one end.

II. Ribs and Interneurals. — Compare this vertebra
with others both before and behind it in the tail region.
Observe that in several of the foremost vertebrae of this
region the large processes of the ventral side do not unite
to form a single hemal spine, but, diverging, form two
spines. Proceeding forward into the body region, ob-
serve that there they no longer form a hemal arch,
that they become more and more divergent, and that
ribs are added to their outer ends. Observe that the
articulation of each rib is such that it appears to be
spliced to the process which supports it. How many
pairs of ribs are there? Observe that the neural spines
of the rib-bearing vertebrae are reduced in length and
modified in form to accommodate the bones which sup-
port the anterior dorsal fin. The latter bones, because
they usually fit in between the neural spines, are called
interneurals.

III. Spines and their Supports. — The part of the spinal
column anterior to the ribs consists of several vertebrae
solidly welded together, and so greatly modified as
scarcely to be recognized as vertebrae at all. They are
joined to the long dorsal process from the skull to the

THE CATFISH. 177

bony pectoral arch, and to the foremost interneurals, in
such a manner as to give a very firm, bony support to the
three defensive spines.

The joints at the bases of these spines, though not
characteristic of fishes in general, but a peculiarity of a
small group, show an interesting kind of animal mech-
anism, and are well worthy of an examination.

Examine first the attachments of the dorsal spine. It
is fastened by a ring to the top of the third interneural.
The first interneural is small, the second and third inter-
neurals are grown together solidly into one piece (the
buckler), and the notched tip of the backward process
from the skull (the helmet) fits against the anterior
edge of this piece. The dorsal spine arises from the
third interneural, and a rudiment of another spine from
the top of the second interneural. This rudiment is a
small, oval bone, forked below. It is set against the base
of the great spine in front, and acts as a sort of bolt, or
fulcrum of support. The widened neural spines also con-
tribute to the support of the great spine, as can be readily
seen.

Examine one of the pectoral spines. Study the beauti-
ful joint by which it is united to the pectoral arch. In
how many directions is it movable ?

Observe the great strength and solidity of this pectoral
arch, and the comparative weakness and small size of the
pelvic arch.

The catfish is a representative of the class Pisces, or fishes
of the great branch Vertebrata (or back-boned animals).

Other Fishes of very different structure can readily
be obtained for study in any locality.1 A common
sucker, or a buffalo fish, is recommended for study, and

1 Use Jordan's Manual of the Vertebrates for identifying the species of
fishes.

NEED. ZOOL. 12

178

VEETEBRATES.

for comparison with the catfish. Compare especially

.vith regard to the following points : —

1. The shape of its body.

2. The character of its body covering.

3. The shape of its mouth.

4. The number and position of bones bearing teeth.

5. The character of the gills and gill rakers.

6. The character of the dorsaland pectoral fins.

7. The shape and attachments of the air bladder.

8. The foremost vertebrae of the spinal column, etc.

THE FROG.

(Eana.)

Haunts and Habits. — In the springtime the musical
efforts of this animal are a sufficient guide to the locali-

ties to be searched for
specimens. In warm
weather small frogs
will be flushed from
their resting places in
.-A the grass by walk-

---._ ing rapidly alongside
any brook or pon(L

They may be cap-
tured in a stout net.
In cold weather live
specimens may be ob-
tained from dealers,
or dredged up from the bottom of ponds. Specimens
captured in autumn may be kept alive a long time
without food, if kept in a cool, damp place ; for in the
winter season they are normally inactive, and take no
food.

COMMON FROG (Rana virescens).

THE FROG. 179

The interesting habits of the frog should be studied in
the field if opportunity offers.

Study of a Live Specimen. — Study the live frog in the
laboratory. Observe : -

1. The stocky, humpbacked body.

2. The absence of tail and of fins.

3. The presence of well-developed legs.

4. The presence of eyelids. Touch the eye with a
pencil, and watch the lids. Are they of one sort?

5. Its method of locomotion in water.

6. Its method of locomotion on land.

7. Its sitting posture.

8. Its breathing : what external parts participate?

Circulation of Blood. — Wrap the frog in a wet towel,
leaving a hind foot protruding. Chloroform it, and ex-
amine with the microscope the circulation of blood in the
web of its foot, as directed for the fin of a catfish.

Structure. — Give additional chloroform, and, when the
frog is dead, study its structure. Note : —

1. The color and markings of the head and of the body ;
of the dorsal and ventral surfaces.

2. The smooth, moist, scaleless skin.

3. The prominent eyes, and behind them, on the sides
of the head, the round tympanic membranes of the ears.

4. The wide mouth.

5. A pair of nostrils above the mouth.

Open the mouth and look into it. Observe : —

1. The fleshy lips which narrowly border the jaws.

2. The absence of teeth from the lower jaw.

3. The number, position, and arrangement of teeth in
the upper jaw.

4. The long, fleshy tongue. Draw it forward, and find
the point of its attachment.

180 VERTEBRATES.

5. The mucilaginous saliva which covers the tongue.
When a fly, or other insect suitable for food, comes near
enough, the frog darts out this sticky tongue, and draws
the entangled fly into its mouth.

Pass a bristle into the nostrils from the outside, and
discover where they open into the mouth.

Cut a hole in the tympanic membrane, and insert a
bristle into the cavity it covers, and push the bristle into
the mouth. The wide tube by which it enters the mouth
is the Eustachian tube.

The posterior, funnel-shaped part of the cavity seen on
looking into the mouth is the pharynx. Its folded walls
converge toward the esophagus.

On the floor of the pharynx is a narrow slit which
leads into the trachea, and thence to the lungs. Pass a
bristle into this slit.

Find a small, isolated patch of teeth on the roof of the
mouth.

Dissection. — Dissect the frog under water. A pre-
pared skeleton should be at hand for reference in locating
bony parts.

Cut through the skin along the median ventral line,
from the mandible to the posterior end of the body.
Make a second cut at right angles to the first, entirely
across the middle of the ventral surface, and turn back
the four flaps of skin thus formed. This will expose the
thin, muscular abdominal wall. Observe a dark vein
showing through the abdominal muscle on the median
line. Make a longitudinal cut through the body wall,
a little to one side of the median line, so as to avoid
injuring this vein, and continue the cut forward to the
bony pectoral arch, or shoulder girdle. Then consult a
skeleton, to see how, by cutting to one side of the median
line, you may avoid injuring the elongated median bone

THE FROG. 181

of this girdle. Continue the cut forward to the base of the
tongue. Stretch the fore legs out at right angles to the
body, and pin them so. Turn back the edges of the last
incision, and fully expose the organs of the body cavity.

Internal Features. — Perhaps the most conspicuous of
the internal organs is the large, mottled reddish liver,
which consists of a large double lobe on the right side
of the body, and of a smaller single lobe on the left side.
Immediately in front of the liver is the heart, inclosed in
a thin, transparent sac, the pericardium. If the heart is
still beating, the arterial system should be injected.1

Pinch up the pericardium with forceps, and cut it away
with sharp scissors. Cut away also its attachments to
the body wall, taking great care not to cut any blood
vessels or other organs.

Pass a pipette or blowpipe through the mouth, into
the trachea, and inflate the lungs to' see their size and
position.

I. Digestive Organs. — Pass a long probe through the
mouth and pharynx into the esophagus, and thence back-
ward into the long, white stomach, which lies just behind,
or partly concealed by, the liver. From the posterior end
of the stomach trace the intestine. It turns forward,
downward, backward, then forms a spire on the right side
of the body, and then, returning to the median line,
enters an expanded terminal portion, the cloaca. Ducts
from the reproductive and renal organs also enter this
chamber. Observe the mesentery with which the intes-
tine is invested, and through which its blood vessels pass.
The position of the liver has been noticed : find the
greenish gall bladder attached to one of its lobes, and find
a duct leading from the gall bladder to the intestine.
This duct will usually be made more evident by squeezing

1 For the method, see Appendix, p. 285.

182 VEKTEBRATE&

the contents of the gall bladder out into ito The pale
or whitish compact mass lying between the stomach, in-
testine, and liver, is the pancreas. What is the relation
between this organ and the duct of the gall bladder ?

IL Reproductive Organs. — A pair of digitate, yellow
fatty bodies are attached to the dorsal wall of the body
cavity, behind the stomach, and close beside the median
line. The paired reproductive organs lie just poste-
rior to these, — rounded yellow testes in the male ; and
folded or lobed, lighter colored ovaries in the female.
In the breeding season, the ovaries may be found so
distended with eggs as to fill out most of the body cavity.
The oviducts, which convey the eggs to the cloaca, are
very long and much convoluted tubes, having no connec-
tion with the ovary, but opening by a funnel-shaped
orifice into the body cavity near the esophagus.

III. Renal Excretory Organs. — A pair of reddish brown
kidneys lie on the dorsal side of the body cavity, near the
cloaca; and ducts from these pass to the large, white,
bilobed urinary bladder, which occupies the extreme pos-
terior end of the body cavity, and which, when found
empty, presents a crumpled appearance =

The small, roundish red body, dorsal to the cloaca, arid
near the anterior end of the kidneys, is the spleen.

IV. Circulatory Organs. — The central organ of circu-
lation in the frog is the heart. In it find three divisions,—
a firm muscular, conical posterior division, the ventricle;
and two anterior, thin-walled divisions, auricles. A cylin-
drical arterial trunk arises from the anterior end of the
ventricle, and passes obliquely forward across the upper-
most ventricle, and soon divides into two principal
branches.

Now trace the principal arteries and veins. If the
arterial system has been injected, there will be no diffi-
culty in distinguishing between arteries and veins ; if not,

THE FROG, 183

the arteries may usually be distinguished by their firmer
walls and somewhat lighter color. No visible blood vessels
should have been severed up to this point in the dissec-
tion. Begin with the venous system, and find the prin-
cipal avenues by which the blood is returned to the heart,
after being distributed throughout the tissues. Find
again the vein that was seen through the thin abdominal
wall before the body cavity was cut open. Trace this
vein backward far enough to see the large branches com-
ing up from the hind legs. Trace it also forward. Ob-
serve that it soon leaves the body wall, and descends
through the body cavity to the liver, where it branches,
sending one branch to each lobe of that organ. This is
the ventral route to the liver ; there is also a dorsal route
through the kidney. Turn the organs that cover the
kidney over to one side, and find a longitudinal vein com-
ing from the posterior end of the body cavity, and passing
along the external margin of the kidney, and dividing up
into numerous branches, which enter the mass of the
kidney. Then find a corresponding set of venous branch-
lets coming from the inner side of the kidney, meeting
branchlets from the other kidney, and uniting into another
large vein, which proceeds forward to the liver, receiving
important branches from the viscera at several points.
This is the portal vein. Trace it to the liver. Then
draw the liver backward, and turn the ventricle over for-
ward, and see the single large vein, the postcava, which
conveys the blood from the liver into the venous sinus,
and thence into the right auricle. Draw the heart gently
backward, and see the two large veins (prcecavce), which
bring the blood into the same chamber from the anterior
parts of the body. The blood flows from the auricle
into the ventricle, and is forced out again, by the con-
traction of the ventricle, through the arterial trunk.
Trace now its outward course. The arterial trunk

184 VERTEBRATES.

divides into two branches, each of which is made up of
three aortic arches, which, curving dorsally, go a little
way together, bound up in a mass of fatty and connective
tissue- Carefully dissect away this tissue, and disclose
the three arches of one side. The anterior (carotid} arch
first leaves its fellows, and at once divides into two
branches which go to the head. The posterior (pulmo-
cutaneous) arch sends branches to the lung and to the
skin. The larger middle aortic arch curves dorsally and
posteriorly. Lift the stomach and adjacent organs a
little away from the dorsal wall, and see this middle arch
extending backward, and uniting with its fellow of the
opposite side on the median line. Observe that the single
dorsal aorta thus formed gives off at once a very large
branch to the organs of the body cavity, itself extends
posteriorly along the dorsal wall, and finally divides into
the two iliac arteries, which go to the hind legs.

Trace now the three arches of one side back to their
origin. Cut each off at the point of its separation from
its fellows, and pass into it a bristle. Then with fine
scissors lay each one open, cutting backward toward the
ventricle. Compare the aortic arches of the frog with
those of the catfish.

That the hindmost aortic arch conveys blood to the lung
for aeration has already been noticed. From the lung a
pulmonary vein conveys the aerated blood back to the
left auricle of the heart, whence it passes into the
ventricle, to be mixed with the venous current from
the right auricle,

V. Respiratory Organs, — Cut the vein and artery con-
necting each lung with the vascular system, arid trace the
lungs forward to their union in the trachea. Dissect out
the trachea, and trace it forward to the mouth. Observe
that it passes through a notch between two posterior horns
of a broad, flat cartilage in the floor of the mouth, the

THE FROG. 185

hyoid cartilage. Lay open the anterior part of the trachea,
and note the structure of its walls.

Again inflate the lungs through the trachea, and study
their structure. Observe that they are composed of rela-
tively few and large air cells (or, more properly, air
spaces), and that the walls of these do not afford a very
great area over which the blood can be distributed for
aeration. The distribution of the capillaries in the skin
is such as to bring the blood near enough to the surface
for partial aeration there. But the total supply of oxy-
gen obtained from both sources is relatively small, and
would be inadequate to any but a cold-blooded, sluggish
animal.

The Nervous System. — Turn the organs of the body
cavity gently to one side until the spinal column is
visible. Observe the white spinal nerves extending out
from it, along the body wall, just beneath the smooth,
transparent peritoneum. Observe that each spinal nerve,
near its origin, sends a branch ventrally into the
body cavity to meet a very delicate nerve cord that ex-
tends longitudinally, ventral to the spinal column, and
near the median plane of the body. Examine this nerve
cord carefully with a lens to find minute ganglionic swell-
ings on it at its junctions with the branches of the spinal
nerves. Find also minute nerves arising from its gan-
glia, and extending to the internal organs. Trace it for-
ward to the head. Find another similar nerve cord on the
other side of the median plane. Find minute white com-
missural nerves connecting the ganglia of the two chains.

This double series of ganglia, with connecting commis-
sures and radiating fibers, included within the body cavity
and distributed to the nutritive organs, constitutes the
sympathetic system. The cerebro-spinal system consists of
brain and spinal column and radiating nerves.

186 VERTEBRATES.

I- Spinal Nerves. — Cut off the esophagus near its
origin, and remove the viscera. Note the absence of ribs
from the walls of the body cavity.. Make out ten pairs
of spinal nerves, as follows : —

The nerves of the first pair curve ventrally and ante-
riorly, and are distributed to the lower jaw.

The nerves of the second and third pairs unite, and go
to the fore legs. The nerves of the second pair are large
and conspicuous, and extend laterally at right angles to
the spinal column : those of the third pair are smaller,
and bend anteriorly to meet those of the second. The
two again divide and reunite repeatedly, to form a plexus
(the brachial plexus).

The nerves of the fourth, fifth, and sixth pairs extend
laterally and posteriorly, to be distributed to the body
wall.

The nerves of the seventh, eighth, and ninth pairs go
to the hind legs. They unite to form a plexus (the ilio-
sacral plexus), which terminates in the large sciatic nerve
of the thigh.

The nerves of the tenth pair are very small. They
may be seen close beside the posterior end of the spinal
column.

II. The Brain. — Remove the skin from above the
cranium and from one side of the head. Dissect it free
from the tympanic membrane with great care. Cut
away the bony roof of the cranium, and with a gentle
stream of water from a pipette wash out the soft sub-
stance that covers the brain and fills out the cavity.
Make out the following parts : —

1. A pair of conical olfactory lobes, extending forward
from the extreme anterior end, and tapering into the
olfactory nerves.

2. Immediately behind these, the large, white, cerebral
hemispheres, which make up the cerebrum.

THE FROG. 187

3. Behind these are a pair of conspicuous rounded
eminences, well marked off from each other, and from the
other parts. These are the optic lobes. The large optic
nerves arise from these below, and cross each other before
going to the eyes.

4. Behind the optic lobes, and on the median line, is a
deep depression, the fourth ventricle. It is covered over
with a thin plexus of blood vessels, which is easily stripped
off, and is often torn away with the cranial wall. In front
of the ventricle, and behind the optic lobes, is a single
transverse band of nervous tissue. This is the cerebellum.
The nervous mass which surrounds the ventricle on the
sides and below is the medulla. It tapers posteriorly
into the spinal cord.

5. There remains a portion of the brain between the
cerebral hemispheres and the optic lobes which has not
yet been mentioned. It is the midbrain. From its dor-
sal surface, between the posterior ends of the cerebral
hemispheres, and on the median line, arises a single
rounded prominence which is not composed of nervous
tissue. It is the pineal gland.

6. About eight pairs of nerves arise from the ventral
surface of the medulla : these are small, and exceedingly
difficult to trace. The fifth and tenth cranial nerves are
largest, and have each a ganglion not far out from their
origin. These ganglia are each connected with forward
prolongations from the longitudinal commissures of the
sympathetic system.

7. The fact that the single cavity that has been seen in
the brain thus far is called the fourth ventricle, will sug-
gest that there are others. Two others will be exposed
by cutting a horizontal slice from the top of the cere-
brum : these are the two lateral ventricles of the fore-
brain. They occupy the cerebral hemispheres, and unite
posteriorly around a median septum. The cavity formed

188 VERTEBRATES.

by their union is continued posteriorly into the midbrain,
and expands there into a narrow cavity, extending ob-
liquely upward and downward, the third ventricle. A
narrow, median canal, the iter, connects the third and
fourth ventricles. A pair of round cavities, the optic
ventricles, occupy the optic lobes, and are connected with
the iter. If the brain be turned to one side, and drawn
upward out of the cranium a little, there may be seen a
downward prolongation from the midbrain toward the
roof of the mouth. It is the pituitary body.

If the foregoing points in the study of the brain have
not been made out satisfactorily in a fresh specimen, place
a frog's head a few days in alcohol to harden, and with it
try again.

The Ear. — In the ear observe the tympanum, from
which the skin has been removed. Observe the opaque
spot in it, and the surrounding transparent area. The
opaque spot is the point of attachment of an elastic rod
which extends across the cavity inside, and communicates
with the inner ear. When sound waves fall on the tym-
panum, and cause it to vibrate, its vibrations are carried
through the elastic rod to the inner ear, which is the true
organ of hearing, and which is securely lodged within the
bone of the skull. Dissect out this elastic rod. It is
called the columella. It is sometimes partly ossified in
the middle.

Appendages. — That there are two pairs of legs will
have been noticed already. Which pair is most service-
able in locomotion? What peculiarity in its structure
would indicate that a frog could jump well, were its
habits entirely unknown? What other animals have you
seen having the same peculiarity of structure, and corre-
sponding ability to jump ?

In fore and in hind leg find three principal divisions, —

THE FROG. 189

in the fore leg, named from the body outward, arm, fore-
arm, and hand (for this limb is homologous with the
upper limb or arm of man) ; and in the hind leg, thigh
(QY femur), shank, and foo t.

Make drawings of both hand and foot as seen from
above. Compare the two as to the number of digits or
phalanges in each, and the number of joints in each digit.
In the males the base of the inner digit of each hand is
greatly swollen in appearance. Such a peculiarity of sex,
occurring entirely apart from the sexual organs, is called
a secondary sexual character.

Study of Superficial Leg Muscles. — Cut the skin around
the base of one of the hind legs, dissect it free from the
underlying muscles half the length of the thigh, and then
strip it off over the foot like a stocking, wrong side out.
Now study the arrangement of parts in this extremity.
The whitish muscles now cover all other parts. Dissect
apart, without freeing at their ends, several of the large
muscles on the back of the femur, and find nerves and
blood vessels and bone. Free at its edges the large muscle
(gastrocnemius) of the back of the shank, and observe : —

1. The connective tissue enveloping all the muscles,
and binding them together.

2. The connective tissue sheath enveloping each indi-
vidual muscle.

3. The white, strong tendon, in which this muscle
terminates at its outer end. Follow this tendon (tendo
AcMllis) outward, along the sole of the foot, and see it
dividing, and its divisions coalescing with the tendons of
other shorter muscles of the foot, and extending to the
toes. Pull this tendon toward the body, and observe the
effect on the foot.

4. The close attachment of the inner end of this muscle
at the back of the knee joint.

190 VERTEBRATES.

Three terms which apply to muscles need to be learned :
(1) the thick, swollen central part is called the belly of
the muscle; (2) that end of the muscle which is most
fixed in position, and toward Avhich, when it contracts,
the muscle pulls, is called its origin; (3) the attachment
of its other, freer end is called its insertion.

Relations of Muscles, Blood Vessels, and Nerves. —
Dissect away the large muscles of the thigh and shank
by cutting transversely through the belly of each, and dis-
secting each way, so as to find the origin and insertion of
each, and having care not to cut blood vessels or nerves.
Trace the great sciatic nerve of the thigh. Follow its two
principal branches down into the foot. Find and dis-
tinguish two large, branching blood vessels in the thigh,
the femoral artery and vein. This dissection, if thought-
fully performed, will enable you to answer the following
questions : —

1. Where, with reference to the joints, are the thickest
portions of the leg ?

2. What give these points their thickness ?

3. What advantage is there in the tendonous termina-
tions of the muscles at the joints ?

4. Where are the bones thickest ?

5. What are the ridges on the bones for ?

6. Which lie deeper in the muscles, arteries of veins ?

7. Why are the principal nerves so remote from the
surface ?

8. Why are the insertions of these muscles all at their
outer ends ?

Separate the thigh and the shank at the knee joint, and
observe the firm, white, elastic cartilage forming the
articulating surface.

Dermis and Epidermis. — After the skin has been lying
in water for half a day, observe that there is an outer

THE FROG. 191

layer (epidermis) in it, which tends to peel off from the
thicker and vascular lower layer (dermis).

Study of the Skeleton. — With a prepared skeleton at
hand for reference, study the separate parts of a disarticu-
lated skeleton.

First, note the arrangement of parts in the skeleton :
the central, vertebral axis, terminated in front by the
skull, and supported by two bony arches and two pairs
of jointed appendages.

I. The Spinal Column. — In the spinal column find ten
separate vertebrae, and a long, unsegmented terminal por-
tion (the urostyle).

Note the presence of a double row of stout lateral pro-
cesses, and the absence of ribs. How many of the vertebrae
bear lateral processes ? Why are the lateral processes of
the third and ninth vertebrae stronger than the others ?

Above the bases of the lateral processes note the articu-
lating processes (zygapophyses), and their method of
uniting adjacent vertebrae.

On either side of the spinal column observe the row of
large openings through which the spinal nerves emerge.
What is the position of one of these openings in relation
to the vertebrae nearest it ?

Isolate one of the midvertebrae, and in it see : —

The large, central neural canal.

Ventral to this, the relatively small centrum (or body
of the vertebra), with its anterior face concave, and its
posterior face convex.

Two stout pedicels of bone, arising dorsolaterally to
support the arch of the neural canal, and bearing (1)
the single pair of stout lateral processes, and (2) the two
pairs of articulating processes already noticed, and (3) on
the median dorsal line a short neural spine. Draw.

Compare this vertebra with a typical vertebra of a fish.

192 VERTEBRATES.

II. Bones of the Fore Limb. — In the fore limb find the
following parts : —

The single long bone of the arm, the humerus. Its shape
is characteristic of long bones; therefore note that it is
somewhat cylindrical, that it is hollow, and that it has an
expanded articular surface at each end, with a shaft between.

The bone of the forearm, made up of two bones, radius
and ulna, which are grown together (anchylosed).

In the bones of the hand, three series may be distin-
guished : —

1. A series of very small, irregularly shaped, carpal
bones, immediately succeeding the bones of the forearm.

2. A single transverse row of cylindrical metacarpal
bones.

3. Several transverse and unequal rows of phalangeal
bones, or phalanges, growing successively shorter toward
the tips of the digits.

III. The Shoulder Girdle. — Study the pectoral arch, or
shoulder girdle. Observe that its bones, together with
their attached cartilages, form an incomplete ring around
the body, that the two halves of the girdle meet on the
median ventral line, and that the parts are obviously
arranged for the support of a pair of limbs.

Observe that each half of the shoulder girdle is com-
posed (essentially) of three bones, which meet around the
cavity (glenoid fossa) into which the head of the humerus
fits. One of these bones (the scapula) extends dorsally,
and is supplemented by a broad cartilage on the dorsal
surface. The other two extend ventrally to meet their
fellows of the opposite side on the median ventral line.
The larger posterior one is the coracoid. The slender,
anterior one is the clavicle.

Posterior to the point of union of the two coracoids,
a flat bone (the sternum), which does not belong to the
shoulder girdle, extends posteriorly on the median ventral

THE FROG. 193

line ; and a corresponding bone (the omosternum) extends
anteriorly from the point of union of the two clavicles.

What attachment is there between the shoulder girdle
and the spinal column ?

IV. Bones of the Hind Limb. — The bones of the hind
limb are as follows : —

1. The single bone of the thigh is the femur.

2. The bone of the shank is the os cruris. It is made
up of two bones, tibia and fibula, as indicated by the lon-
gitudinal grooves near its ends.

In the bones of the foot, three series may be distin-
guished, of which the first consists of two long, curved
tarsal bones, united at their cartilaginous tips. The other
two series are called metatarsal and phalanges, and corre-
spond in position and appearance to homologous parts of
the hand.

V. The Pelvic Girdle. — Study the pelvic girdle. Ob-
serve its shape, position, and attachment to the spinal
column. Its halves are very solidly welded together on
the median line. Each half is composed of three bones,
united about the socket (acetabulum), into which the head
of the femur fits ; and the bones, though solidly coherent,
may be distinguished by examining the lateral surface at
their point of union. (1) The long bone extended ante-
riorly to meet the lateral process from the ninth vertebra,
and shaped like an inverted sled runner, is the ilium.
(2) The bone that forms the ventral fifth of the socket
(acetabulum), and, with its fellow, forms the ventral ridge
of the pelvic girdle, is the pubis. (3) The bone that
forms the posterior two fifths of the socket, and, with
its fellow of the opposite side, forms the posterior ridge
of the girdle, is the ischium.

Compare now shoulder and pelvic girdle, and fore and
hind limb, and note the principal points of likeness and
of difference between them.

NEED. ZOOL. 13

194

VERTEBRATES.

VI. The Skull. — The study of the vertebrate skull is
well begun with the skull of the frog, which is wide and
open, and in which all the bones can be seen from the
outside.

Observe its triangular outline as seen from above, and
the large orbital and nasal apertures. Observe the pos-
terior opening into the cranium (foramen magnum), and
the pair of smooth, articular surfaces (occipital condyles)

pmx

SKULL OF BULLFROG (Rana catesbiana), dorsal view: pmx, premaxilla;
v, vomer; mx, maxillary; n, nasal; g, girdle bone or sphenethmoid ;
pf, parietof rontal ; ptg, pterygoid; po, prootic; sq, squamosal; qj, quad-
ratojugal; o, occipital region surrounding the foramen magnum.

close beside. These meet corresponding surfaces on the
anterior end of the first vertebra.

The bones composing the skull are as follows : —

1. The bone which forms the back of the brain case,
and immediately surrounds the foramen magnum, is the
occipital.

2. The stout pillar of bone, which extends laterally at
the base of the skull at right angles to the median line,
is the pro otic, so called because it lies in front of and covers
the capsule of the inner ear.

THE FROG. 195

3. The hammer-shaped bone, which rests on the outer
edge of the prootic, and extends its " handle " down to
the posterior angle of the lower jaw, is the squamosal.

4. On the dorsal surface, three pairs of bones in front
of the occipital meet on the median line. The first pair
consists of two long, narrow bones, which cover almost
the whole cranium. These are the parietofrontals.

5. In front of the last lies a pair of triangular nasals.

6. In front of the nasals is a pair of smaller bones
(premaxillaries) which form the tip of the snout, which
bear teeth, and which send narrow processes backward
toward the nasals.

7. The border of the lower jaw is formed by the
mandible, which consists of two rami (or branches) which
meet on the median line in front.

8. The greater part of the border of the upper jaw is
formed by a maxillary bone on either side, bearing abun-
dant teeth.

9. Between the posterior end of maxillary and the
" handle end " of the squamosal is a small bone (the quad-
ratojugal~) which completes the border of the upper jaw.

10. Looking at the ventral surface of the skull, a con-
spicuous T-shaped bone is seen extending along the floor
of the cranium. It is the parasplienoid.

11. At its anterior end, a girdle bone (the sphenethmoid)
surrounds the anterior third of the brain case.

12. Two slender palatines extend transversely outward
to the maxillaries on either side. These lie ventral to the
posterior border of the nasals.

13. Between the palatines and the premaxillaries are a
pair of irregular vomers, each with a posterior process bear-
ing teeth.

14. Lying just within the posterior angle of each jaw,
as seen from below, is a conspicuous, three-rayed bone
(the pterygoid).

196 VERTEBRATES.

The cranium is of cartilage when first formed, and is
not completely ossified in old specimens, as may be seen
from the large spaces left in its lateral walls in prepared
skeletons.

Make an enlarged, and if necessary diagrammatic, draw-
ing of the frog's skull as seen from below, naming all the
bones visible in the drawing.

Development. — Every student should study the life
history of the frog. In the spring the eggs may be easily
obtained from shallow pools in which frogs are heard
croaking. Being as large as peas, and each with a dark-
colored yolk surrounded by a layer of whitish albumen,
and all suspended in large lumps of transparent, jelly-like
substance, they are conspicuous and peculiar appearing
objects. They may be looked for at the edges of the
pools, amid the trash which collects there, and often partly
hidden by it. These egg masses are popularly known as
frog spawn.

The eggs, if carried home or to the laboratory, and
kept in clean, cool water, will go on developing. If
freshly laid eggs have been obtained, segmentation may
be seen taking place in the yolk. Later, as the embryo
develops, the yolk will appear oval in outline ; and then,
elongating more and more, an unmistakable head and tail
will soon appear. At length the embryo becomes active,
and breaks through the jelly-like mass, and is hatched.
It attaches itself for a short time, by means of a pair of
minute suckers near the mouth, to the jelly-like mass or
to plants, but soon becomes a free-swimming tadpole. It
then breathes by means of three pairs of external gills,
which appear as minute tufts at the sides of the head.
The water passes in at the mouth, and out through three
pairs of gill slits located just in front of the gills.

If one of these small tadpoles be placed in a watch glass

THE FROG. 197

of water, and examined under low power of microscope,
the circulation of the blood may be beautifully seen in
its gills.

As the tadpole grows, a membranous fold (operculuni)
arises in front of the gills, and extends backward until it
covers them. On the right side of the body, this fold
becomes closely adherent by its posterior margin, thus
closing the exit of the water on that side ; but a trans-
verse passage is developed below, so that all the water
from both gill chambers passes out through the aperture
remaining on the left side. As soon as the external gills
are covered, they begin to disappear by absorption (atro-
phy), and internal gills are developed on the inner side
of the gill slits. Compare the structure of the tadpole,
at this stage, with that of the fish.

Later a pair of legs appear on the sides of the base of
the tail, at first beneath the skin, but soon becoming free.
Another pair is developed beneath the operculum, and
lungs begin to be developed within the body cavity.
Then, by a final molting of the skin, the opercular mem-
brane is shed, the fore legs are set free, and the eyes are
fully exposed. Finally the gills are absorbed, and lungs
become fully developed, and aquatic is exchanged for
aerial respiration. The gill slits close, the tail is ab-
sorbed, and the tadpole has become a frog.

This brief account of the frog's life history touches
only a few of the most salient points, all of which, and
more than which, the careful student will see for him-
self.

Each student should dissect a large tadpole, and should
compare the internal organs with those of an adult frog.
Each student should find out what articles constitute the
tadpole's vegetable diet, and should note, that, with the
change to a diet of animal food in the adult, there is a
great decrease in the relative length of the intestine.

198 VERTEBRATES.

Each student should make a series of outline drawings,
illustrating the life history of the frog.

The frog is a representative of the group Batrachia, of
which tree frogs, toads, newts, efts, and salamanders are
also members.

THE TURTLE.

Haunts and Habits. — The pond turtles or mud turtles
(Pseudemys and Chrysemys), so abundant in our small
inland lakes and sluggish streams, are recommended for
study. In some places remote from water, the common

MUD TURTLE (Chrysemys picta).

box turtle (Cistudo) will be more easily obtainable. It
is very often picked up in dry wood or fields.

The pond turtles are very shy, and somewhat difficult
to secure alive by ordinary methods. They clamber out
of the water upon the trunks of fallen trees along the
banks of secluded ponds and streams, and lie in the sun
for hours at a time, often scores of them together, of
all ages and sizes ; but when they are approached, they
tumble precipitately back into the water, and disappear.
They may be bought from fishermen. They may be
dredged or raked up from the bottom with a large rake
used from a boat. They may be caught with hook and
line, but a stout line will be necessary. A small, compact
piece of meat should be used for bait. A supply of speci-

THE TURTLE. 199

mens should be obtained while the weather is yet warm
in autumn, and kept until needed. They may be kept
alive for an indefinite length of time, without food, dur-
ing cold weather. In the winter season they are normally
inactive, and if kept in a moist, cool place, will need no
looking after.

Study of a Live Specimen. — Study the turtle alive.
After treating it to a good washing to remove the mud,
take it into the laboratory, and study its locomotion : —

1. Its walking. Note the position of its legs with ref-
erence to the body, the distance between its lower sur-
face and the surface on which it walks, its rate of speed.

2. Its swimming and diving. Place it in sufficient
water, and observe how its legs are used in these acts.

Is its form well adapted for rapid locomotion of any sort ?

Note how completely its head and appendages may be
retracted within the shell.

Thrust a pencil toward the eye, and observe a thin,
transparent membrane come out from the inner u corner,"
where it lies folded, sweep across the eyeball, and with-
draw again. This is the third eyelid (or nictitating mem-
brane).

Respiration takes place very slowly, but occasionally the
animal may be seen to swallow a mouthful of air.

External Features. — Note among the external features
the following: —

1. The relative size of head and body.

2. The hard shell or case which nearly incloses the
body. It consists of a convex dorsal plate, the carapace,
and a flat ventral plate, the plastron; and the two plates
are united by a bony bridge at either side.

3. The color and markings of the wrinkled skin cover-
ing the neck and legs. Is any part of it scaly ?

200 VERTEBRATES.

Kill the animal with chloroform. The best way to do
this speedily is to draw the head forcibly out with a
tenaculum, open the mouth, find the opening into the
trachea at the base of the tongue, and with a syringe or
a large pipette inject into it, and through it into the
lungs, a teaspoonful more or less of chloroform.

When the muscles are relaxed, draw out the head,
noting the length of the neck and the position it assumes
when retracted. Note the horizontal extension of the
legs, their length, and range of movability. Find three
principal divisions in each, as in the frog. Notice in the
sides of the body the " pockets " into which the retracted
legs fit.

Examine the head. Note its shape. Note the relative
size and position of nostrils, eyes, and ears. Note the
position of the nictitating membrane of the eye ; the color
of the iris.

Open the mouth and examine the beak, which consists
of the horny sheaths which incase the edges of the jaws.
Observe how these sheaths fit together when closed. Find
two nostril openings into the roof of the mouth ; openings
of two Eustachian tubes on the sides, back of the muscles
which close the jaws (not easily seen from the front, better
seen when the head is dissected) ; the opening into the
trachea, on the floor of the mouth, and the esophagal
opening behind it.

Observe that the horny sheaths of the jaws, and also
the scales forming the external layer of the shell, are con-
tinuous with the skin of the body. Both are thickened
outgrowths from its outer (epidermal) layer, similar in kind
to the smaller scales found on certain parts of the skin.

Dissection. — With a saw or chisel cut through the
bony bridges between carapace and plastron. Place the
turtle on its back. Cut the plastron free from the skin

THE TURTLE. 201

all around the border, and carefully dissect the plastron
free from all its attachments, and entirely remove it.
See the points where it was connected by ligaments with
the pectoral and pelvic arches. Muscles already severed
from their origin on the plastron cover the bones of these
arches. Dissect these muscles carefully away, noting
that they are opposed in pairs on each half of each arch.
Find nerves and blood vessels entering them internally.
Avoid cutting any large branches of the blood vessels.

The peritoneum, covering the posterior part of the body
cavity, should still be intact, and on its inner surface a
pair of abdominal veins should be plainly seen.

The heart should be seen still pulsating in its thin
pericardium, in the anterior part of the body.

The abundant transparent liquid which fills the spaces
within pericardium and peritoneum is lymph.

Placing a thumb inside each half of the pectoral arch,
press outward until its ligamentous attachment with the
inside of the carapace is broken. Then draw the fore
legs forward and outward, to separate the halves of the
pectoral arch, and fasten them so.

I. The Heart. — Open the pericardium, and fully dis-
close the heart and its connections. Observe : —

1. A single large posterior ventricle.

2. A pair of smaller auricles.

3. White, elastic arteries arising from the ventricle.

4. Thinner-walled, darker-colored veins entering the
auricles, and expanded, just before they enter, to form a
contractile venous sinus.

Note the order of contraction, — first the venous sinus,
then the auricle, then the ventricle. This wave of con-
traction pushes the blood forward, and indicates the direc-
tion in which it is flowing through these parts. If the
blood vessels be now injected, they will be much more
easily traced later.

202 VERTEBRATES,

Divide the peritoneum along the median line, and dis-
close the internal organs.1

II. Digestive Organs. — Trace the digestive system,
finding in order : —

1. Esophagus.

2. Stomach.

3. Intestine of three distinguishable parts : —

(a) Duodenum, into which ducts from the gall bladder
of the liver and from the pancreas open.

(6) Small intestine.

(<?) Large intestine ; and at the junction of these two
latter parts, a short, lateral, hollow process (the ccecum).
The spleen lies near the caecum.

III. Renal and Reproductive Organs. — The reproduc-
tive organs cover the kidneys and often other parts.
Find a pair of kidneys communicating posteriorly with a
bilobed urinary bladder. Make a diagrammatic drawing
of all these parts. Make a drawing of the liver, showing
its right and left lobes connected with a transverse band.

IV. Veins and Arteries. — Trace the two anterior ab-
dominal veins, seen through the peritoneum, before open-
ing the body cavity, forward to the liver. Do they unite
before entering the liver ? Trace veins from the hindmost
parts of the body to the kidneys, thence to the liver, and
thence to the venous sinus. Find veins which come from
anterior parts of the body, also entering the venous sinus.

Trace now the principal arteries. Observe that the two
aortic arches and the pulmonary artery arise separately
from the ventricle, and not from an arterial trunk, as in
the frog. Trace the pulmonary artery to the lung, and

1 After dissecting two other vertebrates, the fish and the frog, the
student should not now need further specific directions for finding and
studying the nutritive and reproductive organs. He should rather let his
knowledge of the structure of those vertebrates serve as a guide to the
study of this one , and he should not fail diligently to compare this one
with the other two at every point.

THE TURTLE. 203

the pulmonary vein back to the heart. Trace branches
of the aortie anteriorly to the head. Trace the aortae
themselves posteriorly, to see their union and subsequent
division, and distribution to the various parts. Now
make a diagram showing the general arrangement of the
circulatory system.

V. Retractor and Protractor Muscles. — Study the action
of the long retractor muscles which extend from the middle
of the spinal column to the base of the skull, and of the
protractor muscles, which extend from carapace and pec-
toral arch to the neck. Pull first on one and then on the
other, and note the effect on the head and neck.

VI. Trachea and Lungs. — Extend the neck, and fasten
it so. Dissect out the trachea and the lungs. Inflate the
lungs, and keep them inflated by tying the trachea with a
thread. Hang them up, and let them dry, and preserve
them for comparison with the lungs of other vertebrates.

The narrow slit by which the trachea opens on the
floor of the mouth is the glottis. Why does not food
which is being swallowed get into the trachea?

VII. Spinal and Cranial Nerves and Brain. — Remove
the viscera, and find spinal nerves. Compare in number
and arrangement with those of the frog. Remove the roof
of the cranium, and find cranial nerves and brain. In the
brain find in order from the front, (1) olfactory lobes,
(2) cerebral hemispheres, (3) midbrain, (4) optic lobes,
(5) cerebellum, and (6) medulla.

Study of the Skeleton. — Study the shell of the turtle,
especially in its relation to the bony skeleton. In a
prepared skeleton of an adult turtle, note : —

1. That the pectoral and pelvic arches, and the bases
of the legs, are contained within the shell.

2. That both arches are attached more or less closely
at several points to both carapace and plastron.

204 VERTEBRATES.

3. That the spinal column is coossified with the cara-
pace, only the vertebrae of neck and tail remaining free
and movable.

I. The Shell : Exoskeletal Parts. — Examine the plas-
tron. On its ventral surface find six pairs of flat, horny
plates, with two additional smaller pairs, forming the
margins of the bridges meeting the carapace. On its
dorsal or inner surface find four pairs of plates and one
single plate of bone. Note that the boundaries of the
horny plates on the ventral surface do not correspond
to the boundaries of the bony plates on the dorsal sur-
face. The horny plates, like the scales of other parts,
are developed from the outer, epidermal layer of the skin,
and are therefore called epidermal plates. The bony
plates are developed from the deeper layer of the skin
(dermis), and are called dermal plates.

Examine the carapace. Its convex surface is com-
pletely covered over with epidermal plates, as follows : —

On the median line, at the anterior edge, is a small,
single nuchal plate (sometimes a pair of nuchal plates).

Posterior to this, on the median line, are five large
central plates.

A pair of pygal plates meet on the median line, at the
posterior edge.

The central plates are bordered laterally by four pairs
of large centrolateral plates.

The margins of the shell between the nuchal and pygal
plates are formed by eleven pairs of marginal plates.

Dermal plates are developed beneath the marginal
nuchal and pygal epidermal plates, and correspond with
them in position, in names, and in number, save that the
nuchal and pygal plates are single.

The dermal and epidermal plates together constitute
the outside skeleton or exoskeleton, as distinguished from
the true internal skeleton (or endoskeleton).

THE TURTLE. 205

The relation between the plates which make up the
shell can be better understood by separating them. If
the specimen which was used for dissection, after being
freed from most of its soft parts, be dipped into boiling
water for a few minutes, the horny epidermal (tortoise-
shell) plates may be readily stripped off. If then it be
boiled thoroughly, the marginal nuchal and pygal dermal
plates may be removed. There will then remain only the
endoskeleton, forming still a considerable part of the con-
cave surface of the carapace.

II. Endoskeletal Parts. — On the convex surface, as it
is now exposed, there will be seen markings correspond-
ing to the edges of the epidermal plates which have been
stripped off. Observe that these markings do not at all
correspond to the outlines of the plates of bone they
overlie. These plates of bone are arranged in longitudi-
nal series as follows : —

There is a central row of eight plates formed by the
lateral expansion of the neural spines of eight of the ver-
tebrae, and hence called neural plates.

There are two lateral rows, each of eight plates, formed
by the expansion of eight pairs of ribs, and hence called
costal plates.

III. The Spinal Column. — Study now the arrangement
of bones, as seen on the concave side of the carapace.
The spinal column marks the median line. In it are four
distinguishable regions : —

1. A cervical region, extending from the head to the
shoulder girdle. The cervical vertebrae bear no ribs, and
are not attached directly to the carapace.

2. A dorsal region, of rib-bearing vertebrae, cob'ssified
with the carapace.

3. A sacral region, of two vertebrae, not attached directly
to the carapace, bearing ribs which unite distally to form
a facet for articulation with a bone of the pelvic arch.

206 VERTEBRATES.

4. A terminal caudal region, of many small vertebrae,
without developed ribs, tapering posteriorly to the tip.

The dorsal vertebrae are the ones concerned in the
formation of the carapace. Observe that, of the ten dorsal
vertebrae, each one, except the first and the last, bears a
neural plate and a pair of costal plates. Observe that
the ribs from the first dorsal attach to the costal plates of
the second, and that the ribs from the tenth attach to the
costal plates of the ninth. Notice that several of the
anterior pairs of ribs appear to have moved forward until
they articulate with the centra of two vertebrae. Notice
the finely toothed sutures by which the costal plates meet
each other.

How many of the points noted in the structure of the
shell are directly conducive to its strength?

How many caudal vertebrae are there? How many
cervical? Observe that the first cervical meets the skull
by a single occipital condyle. Separate the cervical ver-
tebrae, and note the great variety of articulating surfaces
between the ends of adjacent centra.

IV. Girdles and Leg Bones. — In each half of the
shoulder girdle there are three bones : —

1. The bone which extends from the shoulder dorsally,
to meet the first costal plate, is the scapula.

2. The posterior of the two bones which extend from
the shoulder toward the median line is the coracoid. It
is horizontally flattened toward its inner end, there be-
coming somewhat triangular.

3. The anterior of the horizontal bones is the pre-
coracoid.

In each half of the pelvic girdle there are three
bones : —

1. The bone which extends from the acetabulum dor-
sally, to meet the sacral ribs, is the ilium.

2. The posterior of the two bones which extend from

THE TURTLE. 207

the acetabulum horizontally, toward the median line, is
the ischium.

8. The anterior of the two horizontal bones is the pubis.

Between ischium and pubis is a large hole, the obturator
foramen. Ischia and pubes of opposite sides meet in a
median ventral symphysis.

In both fore and hind legs find the parts already found
in the legs of the frog, observing the separation of the
two bones of the forearm and the two of the shank, and
the shortness of the tar sal bones.

Development. — The eggs of certain species of turtles
(the eggs which are perhaps most easily found) are laid
in early summer in sunny sandbars in rivers, lakes, and
creeks. At night the mother ' turtle digs down into the
sand, and hides away her eggs a foot or more beneath the
surface, smooths the sand above them, and leaves them
to be hatched by the warmth of the sand, absorbed from
the sun's rays. Although the mother turtle has been
careful to remove visible traces of their whereabouts, they
may yet be found by very simple means. The disturbed
sand in which they lie is much more readily penetrated by
a stick than are other places on the bar. Hence, if a stick
be pushed into the sand at short intervals along the line
of the turtle's tracks, and a place be found where it enters
very much more readily than elsewhere, that is the place
to look for the "nest." The unmistakable tracks of the
turtle across sunny bars of pure sand will seldom be fol-
lowed in vain in May or June ; for the turtles do not
ordinarily frequent such places.

The young turtle which hatches from the egg is essen-
tially like the adult, except in size. It differs somewhat
in having its legs and pectoral and pelvic arches free from
the shell. During later development the sHell encroaches
upon, and partially incloses, these parts. Young in all

208 VERTEBRATES.

stages may be captured in the same situations with the
adults.

No good conception of the life this animal leads can be
obtained in the laboratory. After studying it there, the
student should spend a day or two early in his summer
vacation studying the animal in its native haunts, learning
of its curious habits, and of the peculiar place it fills in
the economy and society of nature.

The turtle is a representative of the class Reptilia (or
reptiles).

Other Reptilia. — Lizards, snakes, and alligators also
belong to the Reptilia.

THE SNAKE.

Lizards and Snakes present types of reptilian structure
so markedly different from that seen in the turtle that
the following outline is subjoined to enable the student to
know how to proceed in case a study of either of these
forms is to be undertaken. For guidance in studying
the details of their structure, he is referred to the refer-
ence works mentioned elsewhere. This meager outline is
written for the snake, but may be applied without much
change to the study of any common lizard.

Study of the Live Specimen. — Get a garter snake
(Eutania), or a black snake (Bascaniori), or any other
common harmless species, and study it alive. Notice the
exceeding gracefulness of its movements, the slenderness
of its flexuous form, the ease of its gliding motion, and
the beauty and harmony of its coloration. Observe : —

1. The entire absence of limbs. How is its rapid pro-
gression effected ?

2. The position it assumes when molested and brought
to bay, and its method of defense.

THE SNAKE. 209

3. Protective resemblance; i.e., likeness in form and
coloration to the natural objects by which it is surrounded
when in its native haunts. Considering that the snake is
a predacious animal, what are the advantages, both pro-
tective and offensive, of being inconspicuous ?

External Features. — Place the snake and a small pieco
of sponge or bunch of cotton saturated with chloroform
in a tight box or under a bell jar, and as soon as the snake
is dead extend it lengthwise on the table and note its
external features. Observe : —

1. The general form of the body.

2. The more or less distinct head.

3. The long tapering tail.

4. The complete covering of scales.

5. The relation of the scales to each other and to the
underlying skin. .

6. The form of the scales —

(a) On the head.

(b) On the back and sides.

(c) On the ventral surface of both body and tail. The
wide ventral plate-like scales on which the body rests are
the gastrosteges. The hindmost of the gastrosteges is the
anal plate. Observe whether it is entire or bifid. The
paired plates beneath the tail are the urosteges.

Search the eye for eyelids ; the sides of the head for
ears ; the front of the head for nostrils.

Dissection. — Stretch the snake back downward upon a
board, and fasten it so with a tack through the tail and
two others through the edges of the upper jaw. Leave
the lower jaw free. With forceps pull this upward and
sidewise, and note how loosely its halves (rami) are
united at their tips. Note : —

1. The looseness of the hinge by which the lower jaw
is attached to the cranium.

NEED. ZOOL. — 14

210 VERTEBRATES.

2. The dilatability of the mouth and throat.

3. The position, shape, and direction of the teeth. Are
they adapted for chewing food ? In what condition does
the snake swallow its prey ?

With forceps draw the forked tongue from its sheath,
and note its character and length.

Find behind the tongue a small opening into the trachea,
the glottis, and behind the glottis the opening into the
esophagus.

With sharp scissors split the abdominal wall down the
median ventral line to the tail. Fasten the cut edges
wide apart with tacks.

Internal Features. — Without further dissection make
out the following parts: —

1. The heart lies in the central anterior portion of the
body, inclosed within its thin transparent pericardial sac.
The large conic posterior portion is the ventricle. The
two lobes beside its anterior end are the auricles.

2. The brownish elongated organ lying along the left
side of the body is the liver.

3. Beneath the liver is the stomach. Leading from the
mouth to the stomach is the esophagus, and posterior to
the stomach is the intestine.

4. Posterior to the liver, and lying close to the begin-
ning of the intestine, is the dark gall bladder. Close be-
side it is the spherical spleen.

F. Posterior to these are the elongated, light-colored
kidneys, one on either side, communicating with the
exterior by a very long and much crimped duct.

6. Posterior to all these are the paired reproductive
organs, each with a separate straight duct lying alongside
that of the kidney.

Lungs and Blood Vessels. — From the glottis the ringed
trachea may be traced back to the pink lung, which lies on

THE ENGLISH SPARROW. 211

the right side of the body. Insert a blowpipe into the
glottis and inflate the lung. Observe a prominent branch-
ing pulmonary artery running along the inner side of the
lung. Cut away the upper part of the pericardium and
trace this artery back to the heart. Through it blood is
conveyed from the heart into the lung for aeration.

Observe on the inner side of the liver a prominent vein
coming from the posterior part of the body cavity, bring-
ing the blood back to the heart. Trace outward from
the heart the aorta (the principal artery), which arises
from the ventricle between the auricles, bends upward and
backward about the esophagus, and passes straight through
the body cavity posteriorly, giving off branches which
supply blood to all the parts.

The lung is single, but the rudiment of its undeveloped
mate may be found by dissecting out the trachea. Dis-
sect out the lung. Inflate it through the glottis, and tie
the trachea with a thread to keep it inflated. Dry it, and
compare it in structure with the lungs of the frog and the
turtle.

Compare the snake with the turtle in respect to —

1. Means of locomotion.

2. Character of mouth parts.

3. Character of scales.

4. Shape of body cavity.

5. Relative development of internal organs.

THE ENGLISH SPARROW.

(Passer domesticus.)

An Interloper. — This bird and its haunts are too well
known to need description. It was introduced into the
United States about 1850, and has since overspread the
whole country. It is the only bird to be found in many of

212 VERTEBRATES.

our cities and towns. Because it is surely supplanting
our more desirable native birds, the student is recom-
mended to find a scientific use for as many specimens as
possible.

Collecting, — There are many ways of obtaining live
specimens. A few are suggested : the ingenious student
will devise other, and perhaps better, means. A trap,
consisting of a common wooden box, set with a figure-4
trigger, and baited with any kind of grain or with a
crust of bread, will usually obtain specimens, but not

Female. Male.

ENGLISH SPARROW (Passer domesticus).

oftener -than once in one place. Sparrows often roost
in sheds and outbuildings, which may be closed after
dark, and all the inmates secured. When found roost-
ing in a vine or shrubbery, they may often be sur-
rounded with a large sheet, and captured within it.

Field Study. — Study the bird in its relation to nature.
On the street and on the lawn observe, as opportunity
daily offers, the habits of the bird, until you are able to
answer the following and related questions : —

1. Is the sparrow solitary, or sociable, in its habits ?

2. What kind of a voice has it ? Can it properly be
said to sing ? Has it different notes for different occa-
sions, and can you discover what any of its notes mean ?

THE ENGLISH SPARROW. 213

3. Can it hear well ?

4. Is its sight as keen as your own ?

5. What does it eat ? It was imported in the hope
that it would rid the country of certain insect pests.
Do you find it eating insects at all?

6. If other species of birds are found in the same
locality, how do the sparrows behave toward the other
birds ?

7. What kind of a nest does the sparrow build ? At
what season ? Out of what materials ? How put together ?
Where is it located ?

8. How many eggs are laid in the nest ? How long are
these in hatching ? How long before the little birds leave
the nest ? What do the fledgelings eat ? How do they
get their food ? Is more than one brood reared each sum-
mer by a single pair ?

9. What physical casualties of weather, temperature,
etc., have you observed to destroy the eggs or young?

10. What are the natural enemies of the species ?

11. Are the fatalities to the young more, or less, fre-
quent than with other animals you have studied?

Study of a Live Specimen. — With a live bird in hand,
note : —

1. The shape of its body. How is ifc adapted for pro-
gression through the air ? How does the plumage of the
body improve this adaptation ?

2. The shape and attachment of its wings. What is
their shape above ? Below ? What is their anterior out-
line when extended ? Their posterior ? Find three prin-
cipal joints in one wing. Note the zigzag position these
joints take, even in the extended wing. Note the mem-
brane stretched between the first and second joints. Of
what advantage is it for flying? Why are the wings
attached at the dorsal side of the body ?

214 VERTEBRATES.

3. The action of the wings. How, in relation to the
air, are they moved forward ? Backward ? How are they
folded up ?

4. The use of the tail. Permit the sparrow to fly about
a closed room, and observe the rudder-like action of the
tail. When the tail is inclined upward, downward, to
right or to left, what is the corresponding direction taken
in flight ? How is the tail used in effecting a quick
stop?

5. The shape and position of the legs. Note the zigzag
position of the three principal joints. Note the position
in standing, in perching, and in flight. Placing the feet
in the perching position on one finger, note how the toes
automatically close and open when the body is lowered
toward the finger, or raised away from it.

6. The action of the legs. Does the sparrow walk ?
Slip a wide rubber band over the wings to hold them
close, or, what will answer the same purpose, tie their tips
together, and note how the bird gets about when using its
legs alone.

7. Respiration. Note what parts of the body visibly
expand and contract in breathing.

8. The eyes. What position do the eyelids assume
when wide open; i.e., are there any "corners" to the
sparrow's eye ? Thrust a pencil toward the eye, and see
the nictitating membrane dart out across the eyeball, and
as quickly retreat again. Observe the round, black pupil
in the center of the front of the eyeball, and the circular
brown iris surrounding it. Take the bird into a dark
place, and watch the pupil enlarge. Then bring it quickly
out into the strong light again, and see it grow smaller.

Wet a small piece of cotton with chloroform, and hold
it on the nostrils of the bird a moment, until it begins to
doze. Then tie the cotton in place, add a few more drops
of chloroform, and lay the bird down. In a few moments

THE ENGLISH SPARROW. 215

it will be quite dead, and, killed in this way, it will be
in excellent condition for a detailed examination of its
structure*

Naming of External Parts. — For purposes of descrip-
tion, the external parts of the bird are named as follows : —

I. The Head and Neck. — At the front of the head is
the beak, "composed of upper and lower mandibles. The
line of meeting of the two mandibles is the commissure.
Observe that in the sparrow the commissure is not
straight, but angulated; i.e., bent downward posteriorly,
as if the corners of the mouth were drawn downward.
The corner of the mouth is called the rictus, and the
bristles overhanging the rictus are called rictal bristles.
The ridge of the upper mandible is called the culmen; and
the keel of the lower' mandible, the gonys. At the base
of the upper mandible are the nostrils. The front part
of the top of the head is the forehead, the top part is
the crown, the back part is the occiput, and the back of the
neck is the nape. The space between the eye and the
rictus is the lore. Below and behind the eye, hidden by
a tuft of loose feathers, is the ear. Lift up these feathers
and find the auditory opening. Examine one of these
feathers with a lens. What advantage is there in having
these feathers less compact than the others? The front
part of the under surface of the head is the chin. The
front of the neck is the throat.

Make an enlarged outline drawing of the head and
neck, naming all the parts upon the drawing.

II. The Body and Tail. — The dorsal surface of the body
is the back. The tufts of feathers covering the bases of the
wings dorsally are the scapulars. The prominent nar-
rowed portion of the back immediately preceding the
tail is called the rump. The long, soft feathers that over-
lap the tail above are the upper tail coverts. The long,

216

VERTEBRATES.

stiff feathers of the tail are the rectrices (or tail feathers),
oftenest called simply the tail in descriptions, though
they are only a part of the exoskeleton of the tail. Be-
neath the rectrices are the long, soft under tail coverts.
The small area of loose feathers just in front of the lower
tail coverts is the crissum. The posterior part of the
remaining lower surface is called the abdomen (or belly) ;
and the anterior, more convex part, the breast.

pr cov

DIAGRAM OF SPARROW: cul, culmen; I, lore; /, forehead; ee, eye; c, crown;
ea, ear; oc, occiput; n, nape; bk, back; r, rump; utc, upper tail coverts;
t, tail; Itc, lower tail coverts; crsm, crissum; 6, belly; gon, gonys;
ch, chin; th, throat; br, breast; bnd, bend of the wing; sc, scapulars;
pr, primaries ; sec, secondaries ; pr cov, primary coverts ; sec cov, secondary
coverts; sp, spurious quills; tb, tibia; trs, tarsus; ft, foot; 1, 2, 3, and 4,

III. The Wings. - — In a wing find parts corresponding
to arm, forearm, and hand. The long feathers which
grow on the most distal division, or hand, are the
primaries. Those which grow on the middle division are
secondaries. In some birds, but not in the sparrow, there
are similar feathers growing on the proximal division,
called tertiaries. The short, soft feathers which overlap
the bases of the primaries and secondaries above and be-
low are called upper or lower, primary or secondary coverts.
At the bend of the wing, and overlapping the upper pri-
mary coverts, is a tuft of short quills (the spurious

THE ENGLISH SPARROW.

217

quills) growing upon the part of the hand which corre-
sponds to the thumb. In the hollow beneath the wing,
at its junction with the body, is a tuft of long, loose, soft
feathers (the axillars).

Expand the wing, and arrange all the feathers naturally.
Note the shape and curvature of the primaries and sec-
ondaries. Note their direction of overlapping. Find on
the wing a series of feathers which shingle in the oppo-
site direction. Observe the position of the coverts. See
how beautifully each feather falls into its proper place
when the wing is closed, how compactly the whole wing is
nestled against the sides of the body, and how it is over-
lapped by the other plumage, and made to contribute to
the symmetry of the bird.

IV. The Legs. —In. a
leg, find thigh, shank, and
foot. The foot consists of
a long, slender tarsus, and
four toes terminated by
horny claws. The tarsus
is made up of several tar-
sal bones solidly grown to-
gether (anchylosecT). Note
the directions the toes take,
and the number of joints
in each. What parts of the
leg are feathered ? What
parts covered by scales ?
What kind of a covering
has the lower surface of
the foot ?

LEFT LEG OF SPARROW (from inner
side, slightly reduced) : fe, femur ;
fi, fibula; t, tibia; trs, tarsus or
tarsometatarsus ; ra, an incomplete
extra metatarsal at base of hind toe ;
1, 2, 3, 4, toes.

Exoskeletal Modifications. — In this external examina-
tion of the bird, three modifications of exoskeleton will
have been noticed.

218 VERTEBRATES.

1. Horny sheaths covering the mandibles and claws.

2. Epidermal scales (^scutellce) covering the tarsus and
toes.

3. Feathers covering the remaining exposed portions
of the skin, and constituting the plumage.

But there are hidden areas of the skin which are bare.
By separating the feathers, find one of these on the median
line of the breast, and another on either side of the base
of the neck.

Examine the stout, thick beak. Such a beak "is well
adapted to eating grain, — to breaking the husks and
hulling out seeds. Examine the claws. Are they sharp
enough to be of much service as defensive weapons ? Are
the feet strong enough to indicate that the claws are used
for defense ?

Examine the scales of the tarsus and toes. Note that
they overlap regularly down the front and sides, and that
a posterior series forms a sharp ridge down the back of the
tarsus. A tarsus with regularly overlapping scales such
as these is said to be scutellate.

Plumage. — Examine the plumage. Pluck one of the
longest primaries from a wing, and examine it. Observe
a median shaft bordered on either side by a web (or vane).
Observe that the shaft is made up of two parts, — a lower
transparent part, the quill (or calamus) ; and the opaque
part, the rhachis, which bears the vanes. Make a cross
section through the calamus, and another through the
rhachis. What is the shape in cross section of the
calamus ? Of the rhachis ? What is the condition of
the interior of the calamus ? Of the rhachis ? Hold-
ing the rhachis horizontally, look at the cut end. Com-
pare the position of the vanes in relation to the rhachis
with that of the wings of the bird in relation to the body.
Why should the vanes be attached to its upper side ?

THE ENGLISH SPARROW. 219

Observe a longitudinal groove on the under side of the
rhachis. Place a needle point in this groove, and push
it along toward the calamus until it enters a small hole
(umbilicus). Trace the vanes downward to their origin.
Where is there another hole leading to the interior of the
calamus ?

Examine the vane with a lens. The thin, narrow linear
plates of which it is made up are called barbs. Observe
that each barb is fringed with similar smaller plates, called
barbules, which, by their interlacing, form a true web, ana
give capacity for much resistance to very weak filaments.
If a piece of the vane be soaked for a time in strong alco-
hol, to remove air, a microscopic examination of its bar-
bules will discover little hooks (hamuli) along a portion of
their margins.

Pluck one of the small rictal bristles from just above
the corner of the mouth. Examine it with lowest power
of microscope, to make out calamus, rhachis, and partial
vanes.

There is one other part present in many feathers. It
may be found in one of the surface feathers of the breast
or back. Examine one of these with a lens. Make out
calamus, rhachis, and vanes, and find in addition an after-
shaft arising from the summit of the calamus, behind the
rhachis. Compare the aftershaft with the parts already
studied.

The three feathers examined, together with nearly all
others that are exposed on the surface, and that make up
the contour of the bird, are contour feathers. The great
variation seen in these is but an intimation of what may be
expected in feathers of this class.

Down feathers lie beneath and between the contour
feathers. Pluck the contour feathers one by one from
a small space on the body, and the down feathers will
remain. Examine one of them with a lens. Compare its

220 VERTEBRATES.

barbs with the barbs of a contour feather. What is the
probable use of these down feathers ?

There are certain hairlike feathers (filoplumes) on the
skin of birds. These are easily seen on a plucked fowl
before singeing. They are not hairs, as a microscopic
examination of one will prove. Birds do not have true
hairs.

Other Structures. — Separate the feathers above the
base of the tail, and find the oil can, a double, cone-
shaped gland, which secretes an oily fluid for "feather
dressing." The bird, with its beak, presses a drop of oil
from this gland, and distributes it over the tips of the
feathers, in the familiar act of preening.

Examine the ear again, and note that the tympanic
membrane is at the bottom of a short external auditory
meatus, and that the skin of the head dips down into and
lines this opening.

Holding the back of the head firmly with one hand,
alternately raise and depress the upper mandible, and
observe that it is movable upon the head.

Within the mouth find the single guarded opening of
the nostrils. Find also the openings into the esophagus
and into the glottis. Note the shape and character of the
tongue.

Insert a tube into the glottis, and inflate the lungs.
Note what portions of the body are expanded.

Dissection. — Prepare a freshly killed specimen for dis-
section. Fasten the specimen with tacks, back down-
ward, on a shingle, with legs and wings fully extended.
Part the feathers, and divide the skin along the median
ventral line, from the neck to the tail, taking care not to
cut through the thin abdominal muscles. Now loosen
the skin from the sides of the body by holding the
severed edge of the skin between a thumb and finger,

THE ENGLISH SPARROW. 221

and with, a knife blade pushing the flesh away from the
skin. At the anterior end of the first cut make a circu-
lar cut through the skin, about the base of the neck.
Then carefully draw the skin of the neck forward over
the head, wrong side out, and fasten it with a tack in
front of the beak. While doing this, observe the position
assumed by the retracted neck, and note again how much
the feathers contribute to the beauty of the bird's outline,
and improve its form for rapid passage through the air.
Draw the skin out laterally on each side of the first
median cut, and fasten it away from the sides of the
body.

Pass a tube into the esophagus, and inflate the crop,
a capacious expansion of the esophagus at the base of
the neck. Tie a string about the esophagus to keep the
crop inflated, for convenience in dissecting off the fat and
integument which cover it.

Observe on each side of the neck a vein (the jugular
vein), usually filled with blood, and dark-colored, and
close beside it a white nerve (the vagus nerve).

I. Removal of the Body Wall. — On the median line of
the breast observe the ventral edge of the sharp ridge
(or keel) of the sternum, and on either side of it the
thick muscles which cover the sternum. Posterior to the
sternum, the internal organs are covered only by the thin
wall of the abdomen. Sever the muscles from the keel
by a single longitudinal cut on each side of it, keeping
the knife close to the bone. Continue the cuts laterally
around the posterior edge of the sternum, severing the
attachment (origin) of a great flap of muscle. Lift up
the loosened posterior end of this great muscle, and
observe it separating from a smaller muscle, which has
its origin in the angle between the horizontal part of
the sternum and the keel. The larger muscle is the
pectoralis major; the smaller one, the pectoralis minor.

222 VERTEBRATES.

Dissect these breast muscles free from all attachments
except their insertions, and, while doing so, look for
veins, arteries, and nerves, entering the muscles near the
shoulder.

The removal of the pectoral muscles discloses the enor-
mously developed sternum, with its sharp keel and its
lateral ribs. The V-shaped bone in front of the sternum
is the wiskbone or merrythought, and is made up of the
two clavicles grown solidly together at their inner ends.
The paired stout bones extending from the shoulders
to articulate with the anterior end of the sternum are
the coracoids. Disarticulate and entirely remove the
clavicles. Free the coracoids from the sternum, and turn
them outward. With small scissors cut away the exposed
abdominal wall, and cut forward through the ribs at the
sides of the sternum. Then remove the sternum, avoiding
blood vessels as much as possible. This will expose the
internal organs. Again inflate the lungs through the glot-
tis, and observe the large air sacs in the abdomen, commu-
nicating with them. Remove blood, which may collect
about the organs, with a small damp sponge. Moisten the
neck, if it dries and hardens too rapidly.

II. The Trachea. — Find at the base of the tongue a
small U-shaped hyoid lone surrounding the front of the
glottis, the long arms of the U extending posteriorly
behind the skull. Dissect it and the tongue free from
their attachments to the lower jaw. The glottis opens
into a slightly swollen cartilaginous antechamber of the
trachea, called the larynx. At the posterior end of the
trachea, where it divides into two small bronchi, is another
slightly swollen portion (the syrinx). This latter is the
principal voice organ in birds. Cut across the trachea
half an inch in front of the bronchi into which it divides.
Make a lateral cut with fine scissors along the sides of
the trachea and bronchi, and turn down the ventral wall.

THE ENGLISH SPARROW. 223

Observe the thinner walls of the posterior portions of the
syrinx. Observe the delicate vertical semilunar mem-
brane projecting forward into the syrinx from the angle
between the bronchi. By the vibration of this membrane,
voice is produced.

Note the relative position of trachea and esophagus.
How is the food, in passing through the mouth, kept from
getting into the trachea through the glottis ?

III. Organs of Digestion. — Dissect out and remove the
trachea and anterior ends of the bronchi. Then proceed
to a dissection of the digestive system, disregarding the
cutting of blood vessels ; for the circulatory system will
be studied later in an injected specimen.

Trace the alimentary canal, beginning at the mouth.
The large crop, in the midst of the esophagus, is a sort of
food reservoir in which the comminution of ingested food
is begun. In its transparent walls may be seen bands of
muscle fibers, which, contracting, give to the crop a sort of
slow, churning motion ; and this, together with the grind-
ing action of the gravel usually found in the crop, and the
softening action of secretions poured from glands in its
walls, begins the reduction of the food.

A short distance posterior to the crop, the backward con-
tinuation of the esophagus enters the mottled glandular,
slightly dilated stomach.

Close behind the stomach is the large gizzard, some-
imes called the muscular stomach. Note the shape of
this organ, the satiny luster of its exterior, the thickness
of its powerful muscular walls, the toughness of its fibrous
inner coat, and the fine gravel mixed with its contents.
This gravel takes the place of teeth, and assists in the
final reduction of the food.

The intestine immediately succeeds the gizzard. The
first long loop in it is called the duodenum. Into this
part the duct from the inclosed whitish or pinkish pan-

224 VERTEBRATES.

creas opens, and also the duct from the gall bladder, which
is attached beneath the edge of one lobe of the liver.

Posteriorly the intestine opens into a widened terminal
portion of the canal (the cloaca). Near the end of the
intestine are two little lateral side branches, which end
blindly, and are called cceca (or diverticulce).

Cut off the esophagus near its anterior end, and the
intestine near its posterior end. Dissect out the inter-
vening part of the alimentary canal, liver, and pancreas,
noting the dark-red spleen lying near the stomach, the
mesentery looping up the intestine, and the blood vessels
distributed to all the parts.

IV. The Heart. — Slit open the pericardium. Expose
and examine the heart. Note its conical shape, and the
firmer texture of its more muscular posterior end. The
auricles (right and left) at the anterior end are distin-
guishable from the ventricles by their darker color, and
by being marked off from the ventricles and from each
other by delicate yellowish lines of fat. Prick a hole in
each auricle, insert a pipette, and inflate to see their extent.

That there are two ventricles also (right and left), is
not evident from the exterior. Snip off the posterior end
of the heart with sharp scissors, and look at the cut sur-
face. The cavities of the two ventricles will be at once
apparent, — that of the left ventricle circular, and sur-
rounded by very thick, muscular walls ; that of the right
ventricle, crescent-shaped, and with thinner walls. Dis-
sect out the heart and its connecting blood vessels,
and fully expose the lungs.

V. The Lungs. — Pass a bristle into one of the lungs
through its bronchus, and probe to find the openings
by which the lungs communicate with the air sacs.
Lay open the bronchus with fine scissors, and see how
it is branched, and how its branches are distributed
through the lung. Dissect out the lungs, and note how

THE ENGLISH SPARROW. 225

closely they are fitted into the dorsal part of the body
cavity, and how deeply they are indented by the ribs.

VI. Renal and Reproductive Organs. — There yet re-
main in the posterior dorsal part of the body cavity the
brownish, trilobed kidneys, partly hidden by the repro-
ductive organs, — a pair of roundish or oval, light-colored
testes, in the male ; a single, larger ovary, often showing
developing eggs, in the female. All these organs com-
municate by separate ducts with the cloaca. Remove
the kidneys, noting their relations to the pelvic bones
and to the sacral spinal nerves.

Concluding Work. — Find two regions in the spinal
column in which the vertebrae are wider than in other
parts. Observe that the spinal nerves issuing in these
regions are larger than the others. To what parts are
these spinal nerves distributed?

Cut the skin around the base of one of the legs, and
pull it off like a stocking wrong side out. Dissect apart
the muscles to find the mechanism by means of which the
toes are clasped automatically when the bird sits perch-
ing. Of what advantage is this to the bird ?

Loosen the bird, turn it over, and pull the skin entirely
off from the head. The pockets in the skin, which are
fitted down into external auditory openings, may readily
be pulled out, but the attachment at the eyes will have to
be cut. Then carefully cut away the top of the cranium,
and the membranes that lie beneath it, closely covering
the brain. Having fully exposed the brain, carefully
lift it out, beginning at the anterior end, and severing
the cranial nerves as soon as they are exposed. Place the
brain at once in alcohol to harden for future study.

Study of the Circulatory System. — In an injected
specimen1 study the circulatory organs. The heart has

1 For method of injection see Appendix, p. 286.

NEED. ZOOL. — 15

226 VERTEBRATES.

already been studied, and its auricles and ventricles have
been located.

I. The Venous System. — Trace first the veins. The
right auricle receives all the venous blood from all parts
of the body through three principal veins, — two prce-
cavce (right and left) and one postcava. Find these three
veins, and note the points at which they enter the auricle.
Trace each of the praecavse forward, and find each to be
formed by the confluence of three veins, one coming from
the head (the jugular), one from the wing (the brachial),
and one from the great pectoral muscles (the pectoral).
Observe that the postcava comes to the heart through the
right lobe of the liver, receiving small branches in that
organ. Posterior to the liver it is formed by the union
of two (iliac) veins coming from the kidneys. Three
other veins on each side bring the blood from the posterior
parts of the body to the kidneys.

II. The Pulmonary System. — The blood collected in the
right auricle descends through a valvular opening into the
right ventricle. The right ventricle then contracts, and
sends the blood out to the lungs through a pair of short
pulmonary arteries (right and left). Find these arising
together from the right auricle, but at once dividing, and
going directly one to each lung.

From the lungs the blood, after aeration, flows back to
the heart through a pair of pulmonary veins (right and
left), which enter the left auricle separately. These will
probably be more easily traced from the auricle out to the
lungs.

III. The Arterial System. — The blood thus collected
into the left auricle descends through a valvular opening
into the left ventricle, whence it is expelled through a
single large artery (the aorta) to all parts of the body by
the contraction of the ventricle. Herein lies the explana-
tion of the very thick muscular walls of this ventricle.

THE ENGLISH SPARROW. 227

Near its origin the aorta gives off a pair of large (in-
nominate) branches, which go to right and left sides of
the anterior part of the body. Each of these branches
divides into three smaller arteries (carotid, brachial, and
pectoral), corresponding to the three branches of each
prsecava. The aorta curves dorsally, and toward the right
side, and is continued posteriorly through the body cavity
as the dorsal aorta, giving off principal branches to all the
important visceral organs, and to the legs.

The Skeleton. — Study the sparrow's skeleton from dis-
articulated bones. Have a mounted skeleton at hand for
reference. Note the lightness of the bones. Hold some
of them up to the light, and observe the air spaces in
them. Note that the most striking peculiarities of the
skeleton are in the bones of the pectoral and of the pelvic
regions, modifications in the one region adapting the fore
limbs for flight, and in the latter adapting the hind limbs
for supporting the entire weight of the body in walking.

The axial part of the skeleton, as in all vertebrates, is
the spinal column, with the skull at its anterior end.

I. The Skull. — Study the skull. Observe the large
orbits dividing it into a posterior cranial region and an
anterior facial region. Observe that the orbits are sepa-
rated from each other by an incomplete interorlital septum.
Observe that the cranial cavity opens widely into the
posterior dorsal part of both orbits. This large opening
was closed in life by a membrane, but the smaller ones
beneath it are foramina for the exit of cranial nerves.
At the back of the cranium find the foramen magnum, and
just beneath this the single occipital condyle, a minute
knob of bone for articulation with the first vertebra.
On either side of the condyle are very minute foramina
for the exit of other cranial nerves.

Note how the lines of the skull converge toward the

228

VERTEBRATES.

point of the beak, giving the skull a slightly oblique,
pyramidal form, the cranium forming the base of the
pyramid.

The skull is composed of many bones, a large proportion
of which will be found to be solidly coossified in all except

immature specimens. Their out-

lines will not be distinguishable,
5

but their location may be learned
by reading the following descrip-
tion with skull in hand.

The region immediately sur-
rounding the foramen magnum
is formed of the occipital bones.

Four pairs of bones complete
the dorsal surface of the skull.
The bones of each pair meet on

the median line.

^ The parieM bmes form the

greater part of the roof of the
cranium, and present convex dor-

sal SUrf aCCS.

2- In front of these'

SKULL OF SPARROW, slightly
enlarged (ventral view, man-
dible removed) : m, foramen
magnum; c, occipital con-
dyle; bs, basisphenoid ; r,

bar ; q, quadrate ; ptg, ptery-

lary portion of quadratojugai tal bones cover the foremost part

ptpaSeTroc^'o/^ of the cranial cavity, and form

maxillary; pr m, maxillary the upper boundary, and most of

SStSTSSSfLS the posterior boundary, of the

cranial cavity (closed in life orbits.

3. The nasal bones lie next in

front of the frontals, and extend forward between, and
partly surround posteriorly, the nasal openings.

4. The premaxillary bones complete the dorsal surface,
and form the bony part of the upper mandible.

Looking at the side of the skull, note : —

1. The lachrymal bone, of irregular rhomboidal outline,
set transversely to form the anterior wall of the orbit.

THE ENGLISH SPARROW. 229

2. The postorbital process of the frontal bone, projecting
downward to form the postero-lateral rim of the orbit.

3. The squamosal bone, applied obliquely to the side of
the cranium, just behind the postorbital process of the
frontal.

4. The quadrate bone, a conspicuous bone connecting
the lower jaw with the cranium, and freely articulated
with both.

On the ventral surface of the skull, anterior to the occip-
ital, are three distinguishable unpaired bones.

1. The basisphenoid forms the convex, most ventral
portion of the cranium.

2. The rostrum is the narrow forward continuation of
the basisphenoid, and appears as a thickening of the ven-
tral edge of the interorbital septum.

3. The ethmoid is a small bone inclosed between the
nasals and the lachrymals, and lying on the median line,
at the anterior end of the rostrum.

The remaining bones of the ventral side of the skull are
paired. They form two bony bars on each side, extending
from the premaxillary in front to the quadrate behind.
The premaxillary of each side on its ventral surface will
be seen to send back two short horizontal processes of bone,
one to meet each of these bars.

1. The outer or quadratojugal bar is a slender rod of
bone forming the ventral border of the orbit. It extends
from the outer or maxillary process of the premaxillary
bone to the quadrate. It is composed of three bones
wholly indistinguishable in the adult skull. These are
(named from the front) maxilla, jugal, and quadrato-
jugal.

2. The inner or palato-pterygoid bar is composed of the
palatine and pterygoid bones, and extends from the inner
or palatine process of the premaxillary back to the quad-
rate. It is not a straight and simple bar of bone, like the

230 VERTEBRATES.

quadratojugal bar, but irregular, widely and irregularly
expanded in its anterior part, and bent inward to fit
against the rostrum.

The two bones composing this bar are readily distin-
guishable. The palatine is the broad, flat, anterior one
which meets the rostrum by its inner edge. The pterygoid
is the slender, posterior one, which has its inner end ex-
panded to fit against the side of the rostrum, its outer end
rounded for articulation with the quadrate.

Thus it will be seen that both upper and lower mandibles
are articulated to the cranium by the quadrate. The other
attachment of the upper mandible to the cranium is in the
region of the nasal bones. Holding the cranium between
the fingers, gently move the mandible up and down, and
observe that the flexibility of the bones in this region,
and not a distinct articulation, permits this motion. While
moving the mandible, observe that the palatine and ptery-
goid slide forward and backward upon the rostrum, and
the lower exterior corner of the lachrymal slides upon the
maxillary.

A pair of minute bones (the vomers) meet on the median
line between the palatine processes of the two premaxil-
laries, and in front of the two palatine bores. These are
liable to be removed in the preparation of the skull, and
so may not be found.

II. The Spinal Column. — Study the spinal column.
Note the length and flexibility of the neck, the shortness
of the tail, and the large number of anchylosed vertebra
which meet the bones of the pelvic arch.

Four regions are distinguishable in the spinal column,
but the boundaries between them are ill defined. Named
from the front, these are the cervical, thoracic, sacral, and
caudal regions.

The cervical vertebrae are those between the head and
the foremost vertetra bearing a rib articulating with the

THE ENGLISH SPARROW. 231

sternum. Study a typical vertebra from near the middle
of the cervical region. Note : —

1. Its relatively light centrum.

2. Its wide, neural arch, notched before and behind,
with the neural spine small or absent.

3. Its articular processes (zygapophyses). How do
these meet in adjacent vertebrae?

4. The saddle-shaped, articular faces of the centrum.

5. The wide, transverse processes at the sides of the
anterior end, each perforated at its base by a wide fora-
men, and produced posteriorly into a long, slender point.
This process is homologous with the ribs which arise in
the same position on the vertebrae farther back.

The thoracic vertebrce are those which bear ribs articu-
lating with the sternum. Note the Y-shaped processes
uniting the tops of the neural spines of these vertebrae.
Observe on all the vertebrae the lateral notches opposite
the neural canal, for the exit of the spinal nerves.

These thoracic ribs consist of two portions : —

1. A vertebral portion, flattened and curved, having two
articulating surfaces at its proximal end, — a head which
articulates with the centrum of the vertebra, and a tuber-
cle which articulates with the transverse process, — and
having a flattened uncinate process which projects back-
ward, overlapping the next succeeding rib.

2. A sternal portion, slender and nearly straight, ex-
tending obliquely forward to articulate with the sternum.

Of what advantage is the joint in the middle of the
rib ? The series of overlapping uncinate processes ?

The sacral vertebrce succeed the thoracic, and are solidly
anchylosed, and support the bones of the pelvis. Observe
that the first three and the last four of these have their
lateral processes directed laterally, but in the intervening
three or four these processes are directed dorsally.

The caudal vertebrce are the remaining free ones, with

232 VERTEBRATES.

conspicuous neural and lateral processes, and the large,
terminal, triangular pygostyle which supports the tail
feathers (rectrices).

How many cervical vertebrae are there ? How many of
them bear evident ribs ? How many thoracic vertebrae are
there? How many thoracic ribs bear uncinate processes?
How many sacral vertebrae are there ? How many caudal ?

III. The Sternum. — Study the sternum. Note the fol-
lowing parts : —

1. A large, squarish, shovel-shaped
body, which closely covers the tho-
racic cavity, and extends backward
some distance over the abdomen.

2. A large, triangular keel, borne

on the median ventral line of the
STERNUM OF SPARROW

FROM RIGHT SIDE body of the sternum. Note that both

(natural size) : b, ^ body and ^Q keel are composed

body ; k, keel ; m, ma- •* . f

nubrium or rostrum ; oi very thin plates ot bone, with sur-
cg, coracoid groove; faceg minutely roughened for the

cp, costal process; x,

lateral xiphoid pro- attachment of muscles, and strength-

cess ; sp, space filled d b thickened marcnns.

in life by membranes. *

3. A stout, median rostrum (or

manubrium), forked at its tip, which projects forward,
and obliquely upward from the base of the keel, at the
front of the body of the sternum.

4. A pair of sharp, triangular costal processes project-
ing forward from the anterior angles of the body. The
lateral borders of these processes are thickened to form
the costal surfaces bearing facets for articulation with the
sternal ends of the ribs.

5. Between the costal processes and the rostrum, a
pair of coracoid grooves, in the anterior edge of the body
of the sternum, meeting on the median line. These grooves
are for articulation with corresponding ridges on the ends
of the coracoid bones.

THE ENGLISH SPARROW.

6. Just behind the costal processes, a pair of conspicu-
ous, slender lateral xiphoid processes, arising from the
lateral margins of the body, and extending obliquely
backward, to partially inclose a pair of triangular spaces
which were in life closed by membrane.

IV. The Shoulder Girdle. — Study the shoulder girdle.
Each half of it consists of the three usual bones, meeting
to form the shoulder.

1. The scapula is a long, thin, and narrow bone, shaped
somewhat like a sled runner, extended backward from the
shoulder above the ribs. It is enlarged to form articular
facets at the shoulder, and sharply pointed at the posterior
end.

2. The coracoid is a stout, straight bone set in between
the shoulder and the front of the sternum. How does
its direction correspond with the direction in which the
pectoral muscles pull ?

3. The clavicle is a slender bone, shaped like a fishhook,
with the hook turned toward the sternum. It is anchy-
losed at its hook end with its fellow of the opposite side,
and the two together are commonly known as the fur-
culum (merrythought, or wishbone).

V. Wing Bones. — Study the bones of the wing.

1. The humerus is the single stout bone of the arm.

2. The radius and ulna are the two bones of the fore-
arm. They are entirely separate. The ulna is much the
stouter. It has a blunt proximal (olecranori) process pro-
jecting back of the elbow joint, and its posterior edge is
roughened for the attachment of the bases of the second-
ary quills.

3. The carpal, metacarpal, and pJialangeal bones are
peculiarly anchylosed in the adult. Two carpal bones
remain free at the distal end of radius and ulna. Three
distal carpal bones have fused with three metacarpals to
form a conspicuous single bone, the carpo-metacarpus.

234

VERTEBRATES.

The two component parts of this bone most easily recog-
nizable are the elongated second and third metacarpals ;
the second is stout and straight, the third is slender and
curved, and the two are fused only at their ends. The
short and stumpy phalanges of three rudimentary digits
are articulated with the carpo-metacarpus, — one (the
thumb) at its anterior edge near its proximal end, the
other two toward its distal end.

WING BONES OF SPARROW, slightly enlarged (ventral aspect of left wing) :
h, humerus ; r, radius ; u, ulna ; ol, olecranon process of the ulna ; c and c,
free carpal hones ; cmc, carpo-metacarpus ; 1, 2, and 3, phalanges.

VI. The Pelvic Girdle. — Study the pelvic girdle. Each
half of it is made up of the three usual bones, — ilium,
ischium, and pubis, — meeting around the acetabulum,
and solidly anchylosed together. The acetabulum is
but a rim of bone, its bottom being membranous.

1. The ilium forms the front and upper walls, and a
great part of the hinder wall of the acetabulum. The two
ilia, together with the sacral vertebrae included between
them, form the entire roof of the pelvis. Each ilium is
attached along almost its entire length to the lateral pro-
cesses of the sacral vertebra. An obliquely transverse
line divides its dorsal surface into two parts, the anterior
one concave, the posterior one convex. A lateral process
from it overhangs the acetabulum, and articulates with a
process on the femur.

2. The ischium forms a part of the hinder wall of the
acetabulum, and extends thence directly backward. It is

THE ENGLISH SPARROW. 235

In part separated from the ilium by a large oval or oblong
{ilio-*ciatic) foramen.

8. The pubis forms part of the lower wall of the ace-
tabulum, and extends thence obliquely downward and
backward. It is in part separated from the ischium by a
small, round (obturator) foramen.

VII. Leg Bones. — Study the bones of the leg.

1. The femur is the single bone of the thigh.

2. The tibia is the large bone of the shank ; the fibula
is the slender bone extending halfway down the outer side
of the tibia. The proximal tarsal bones are fused with
the distal end of the tibia, leaving the ankle joint, not
between tibia and tarsal bones, but between the first and
second series of tarsal bones.

3. The tarsal bones of the second series are fused with
the metatarsal bones, to form the single bone which we
have already designated as the tarsus (more strictly, the
tarso-metatarsus) .

At the distal end of the tarsus are the four toes. The
hind toe is the first digit ; the others are numbered second,
third, and fourth, away from the median plane of the body.
How many phalanges are there in each digit?

The Brain. — Study the external features of the brain.
On the dorsal surface, note the parts seen, proceeding
from the front, as follows : —

1. A pair of small, conical, olfactory lobes, at the ante-
rior end.

2. A pair of large, smooth, pear-shaped cerebral hemi-
spheres, meeting on the median plane.

3. A small, median, pineal body, immediately behind the
hemispheres, and in the angle between them.

4. A pair of smooth, ovoid, optic lobes, behind and below
the hemispheres.

5. A median, oval cerebellum, transversely furrowed,

236 VERTEBRATES.

i

meeting the hemispheres in front, and overlapping the
optic lobes at each side.

6. A large medulla, covered in front by the cerebellum,
and narrowed posteriorly into the spinal cord.

On the ventral surface note the crossing of the optic
nerves (optic cJiiasma), and just behind this, on the median
line, a small process (the infundibulum), which was con-
nected with the pituitary body before the removal of the
brain.

The sparrow is a representative of the vertebrate class
Aves (or birds).

Other Birds. — If material is at hand, and if time will
permit, the further study of this interesting and important
group is recommended. A hawk, a duck, a woodpecker,
and a snipe are in most places obtainable ; and these four
are mentioned for further study, because they illustrate
common types of bird structure. It will be interesting to
compare a number of birds as to the following points of
structure, noting in each case the exact adaptation of each
structural peculiarity to the life and habits of the bird in
which it is found. Note : —

1. The relative size and proportions of body, wings, and
tail.

2. The character of the plumage.

3. The shape, size, and strength of leak and claws.

4. The number, insertion, and direction of the toes, and
the amount of webbing between them.

5. The length and position of the neck and of the legs.

6. The size and position of the eyes.
In the field, note : —

1. Their haunts.

2. Their food, and manner of obtaining it.

3. Their flight . Learn to know a bird by this alone.
The rapid, whistling flight of some ducks ; the cycloid

THE RABBIT. 237

soaring of some hawks ; the airy, skimming flight of swal-
lows ; the shambling, silent flight of owls ; the graceful
sweeps made by the large woodpeckers between distant
trees; the flitting of warblers, etc., — are very character-
istic.

4. Their notes. Learn to recognize a bird by its voice
alone. Learn to recognize the meaning in the different
notes of some familiar birds.

5. Their attitudes. By the position in perching alone
most birds may be known.

6. Their nests. Observe the time of nesting ; the num-
ber, size, color, and markings of the eggs ; and the loca-
tion, material, and construction of the nests.

7. The times of departure and return of the migratory
species.

If a small collection of bird skins is at hand, the work
of identifying the species in it is commended as an excel-
lent means of getting a practical acquaintance with the
leading systematic peculiarities of a number of birds.1

THE RABBIT.

(Lepus syluaticus.)

Haunts. — This animal lives in hedges, brush heaps,
and brier patches on the borders of fields, orchards, and
gardens. It is much hunted for food, and throughout the
winter may usually be found in the market. But market
specimens are usually so mutilated as to be unfit for study.
Specimens for study may be easily captured alive by

1 Should any student wish to prepare a few bird skins for study, he will
find full directions, well illustrated by plates, in Davie's Methods in the
Art of Taxidermy. For further study, Coues's Key to North American
Birds, and Davie's Nests and Eggs of North American Birds, are
recommended.

238 VERTEBRATES.

trapping. Light steel traps are usually efficient; but a
heavily weighted box trap set with a figure-4 trigger,
and baited with a cabbage stalk or a sweet potato, will
answer equally well. As the rabbit is nocturnal, the
traps should, of course, be set in the evening, and in places
much frequented by rabbits, in the " runs " or paths they
make through the grass or through the snow.

Habits. — A little time will be well spent in studying
the rabbit in its relation to nature. A moonlight evening
in winter, when the ground is frozen and covered with
snow, and when food has become scarce, or hard to get,
will afford a good opportunity. At such a time the
rabbits become more venturesome in their search for food.
They invade gardens, and search them over for stray tops
of cabbage or celery left from the preceding autumn ;
they enter orchards, and gnaw the bark from unprotected
young apple trees; they girdle wild crab apples and
other small woodland trees in the same way; and they
sometimes assemble and play together, dancing and scam-
pering about in the snow, with no other apparent object
than a good social time.

On a warm evening in spring they may be seen sitting
by the roadside, nibbling the tender leaves of clover. At
such a time they may be approached quietly. If alarmed,
they will at once leap into cover, and disappear. In locali-
ties where they are much hunted on foot, they may be
approached nearer on horseback.

At a distance, one may often be seen to rise up on its
hind feet to its full length, and look about, as if for
danger, with ears aloft. Near at hand, one, wishing to
hide, will crouch low on the ground, with its ears ex-
tended flat along its back. In such a position it is very
inconspicuous, especially if seen among dried grass and
leaves, which its colors so closely imitate.

THE BABBIT.

239

In a rabbit hunt with dogs, a rabbit will certainly be
seen to run in circles, repeatedly crossing its former tracks,
throwing the dogs off the scent.

The simple " form " the rabbit makes for itself for a
resting place in the grass ; the retreats it finds in hol-
low logs and stumps, and in the deep burrows of other
animals ; and the shallow, fur-lined burrow which it makes
for itself in dry, loose soil, for a home in which to rear
its interesting brood, —
should all be studied in
the field.

The live rabbit should be
studied in the laboratory.
Its postures should be
noted. It should be deter-
mined whether the rabbit
ever walks, how fore feet
and hind feet are used in
locomotion, in what direc-
tion it cannot see without
turning its head, whether
it shifts its ears to suit
the direction from which

a sound is coming, etc. GRAY EABBIT (Lepus sylvaticus).

External Features. — Note its covering of hair. Ob-
serve that the hairs are of three principal sorts : —

1. Short, soft, kinky hairs, which make up the greater
part of its coat, and which collectively constitute fur.

2. Fewer, longer, straight, black-tipped hairs, which
protrude through the fur.

3. Long, stiff, tactile hairs (or whiskers) at the sides of
the upper lip, and above and below the eyes, deep seated
in the skin, and intimately connected with nerve endings.

Note the color of the fur at the surface, and next the

240 VERTEBRATES.

skin. On what parts of the body is the hair longest ?
What exposed parts are bare, and why ? Compare the
color of upper and lower surfaces. What is the character
of the hair on the soles of the feet ?

Examine the claws. Are they well adapted for weapons
of offense ?

Note the length and position of the tail. Take the fol-
lowing measurements : the distance from the tip of the
nose to the base of the tail ; the length of the tail ; the
height of the ears ; the length of fore and hind legs and
of fore and hind feet.

Note the close approximation of the ears, and the wide
space between the eyes. What is the advantage to the
rabbit, of this arrangement?

Why does a rabbit run more easily up hill than down ?

Note that the upper lip is cleft below the nostrils, ex-
posing the front teeth when the lips are retracted. The
advantage of this in gnawing is very obvious.

Structure. — Dissect the rabbit on a broad piece of
board, into which tacks may be driven. Use an injected
specimen.1 Make a circular cut through the skin, around
the base of its neck, and pull the skin forward over its
head, wrong side out, carefully dissecting it free from the
parts which lie beneath. At the base of the ears note
the tubular, basal cartilage supporting each ear, and see
also the attached muscles, which change the position of
the ears. Cut off the ears : this will expose the external
auditory canals. At the eyes, in removing the upper and
lower lids with the skin, an imperfect third eyelid (or
nictitating membrane) should be left behind. Remove the
skin of the head entirely, breaking or cutting its attach-
ments at the lips. Note the hairiness of the inside of the
cheeks.

1 For a method of injection see Appendix, p. 286.

THE RABBIT. 241

I. The Teeth. — Placing the rabbit on its side, lay open
the cavity of the mouth by a lateral cut midway between
upper and lower jaws. This will expose the teeth. Ob-
serve that the teeth are of two sorts : —

1. Incisors (or gnawing teeth). These are the front
teeth. They are long, and strong, curved teeth, with
chisel-shaped, cutting edges. Observe that there is a
large pair of incisors above, and another pair below, and
a pair of very small supplementary incisors situated just
behind the large pair in the upper jaw.

2. Molars (or grinding teeth). These are situated far-
ther back, in the sides of both jaws, deeply imbedded in
the bone. The upper ones and lower ones meet by flat,
corrugated, grinding surfaces, between which the food is
comminuted. There are six pairs above, five pairs below.
Observe that the molars are set obliquely in the jaws.
Is there any relation between their direction and the
direction in which the jaws are moved in chewing? Note
the absence of teeth, from a large space between incisors
and molars, in both jaws.

II. The Tongue. — Continue the lateral cut backward
across the angle of the mandible, cutting through the
bone with bone snips or with stout scissors. Forcibly
turn the severed ramus of the mandible outward, break-
ing its connection with its fellow, at the symphysis, in
front. This will expose the buccal cavity and the tongue.

Study the tongue. Observe that it is thick and mus-
cular, attached posteriorly to the floor of the mouth, and
produced anteriorly to a flattened, tapering tip. Ob-
serve that the surface of the free, anterior part is soft and
delicate, while that of the posterior part, which rubs
against the i-uof of the mouth, is rough and firm. The
soft part is dotted over with minute taste papillse. On
either side of the tongue, on its sloping edge, just oppo-
site the last molar tooth, there is a small, oval area (^papilla

242 VERTEBRATES.

foliata), which is crossed by minute, oblique, parallel lines.
There are some relatively large taste buds imbedded in
this part. Between the two oval areas of opposite sides,
and a little farther back, there are four large papillae
(circumv allate papillae) arranged in a posteriorly convex
curve, two on either side of the median line. Each of
these papillae is surrounded by a circular groove.

III. The Palate and Adjacent Parts. — Study the palate.
It is the narrow, median strip or area along the roof of the
mouth. Its anterior portion, which is raised into trans-
verse ridges against which the tongue rubs, is called the
hard palate. Its smooth, soft, posterior half is called the
soft palate. It ends behind in a free border.

Just behind the small upper incisors are a pair of
minute pores opening into small canals which extend up-
ward, connecting the cavities of the nose and the mouth.

A pair of small pits at the sides of the soft palate, near
its hinder border, are the tonsils.

The pharynx is the backward continuation of the mouth
beyond the soft palate. The nasal chamber opens into it
above the soft palate.

The JEustachian tubes, coming from the ear, open on the
sides of the posterior nasal chamber within, about the
middle of the soft palate. Split the soft palate longi-
tudinally, turn apart the severed edges, and find the two
openings.

IV. The Salivary Glands. — Find the salivary glands.
They are four pairs of large, pinkish, reddish, or whitish,
lobulate bodies which secrete saliva, and pour it into the
mouth through small salivary ducts : —

1. The parotid gland is the largest. It lies in front of,
and just below, the external auditory canal. Its duct
runs forward at first, just beneath the skin, and opens on
the inside of the cheek, opposite the second upper molar
tooth.

THE RABBIT. 248

2. The infraorbital gland lies just below, and in front
of, the eye, partly within the lower border of the orbital
space. Its duct descends to open near the duct from the
parotid.

3. The submaxillary gland lies close to its fellow of the
opposite side, between the angles of the lower jaw. Its
duct extends forward, and opens on the floor of the mouth,
about halfway between the base of the tongue and the
lower incisors, and quite near the median line.

4. The sublingual gland is a small, elongated, flat gland,
lying close to the inner side of the mandible, anterior to
the base of the tongue. Its very minute duct opens also
on the floor of the mouth.

V. Hyoid Bone and Glottis. — The hyoid lone lies
deeply imbedded in the flesh between the angles of the
lower jaw. It furnishes important attachments for
muscles of the neck. Its position may be determined
by feeling with the fingers.

The pharynx is narrowed posteriorly into the esophagus.
On its floor, near the commencement of the esophagus, is
the opening of the glottis (or larynx). The glottis stands
widely open, and its entrance is guarded by an erect flap
of cartilage, the epiglottis. When food is swallowed, the
epiglottis is depressed, and forms a bridge over the glottis,
across which the food slides safely into the esophagus.
Depress the epiglottis, and study its action.

VI. Thorax and Abdomen. — Extend the hind legs
backward, and the fore legs forward, and fasten them
so with a tack through each foot. Observe two fairly
well defined regions in the body of the rabbit : (1) a
thorax with its walls supported by ribs, and (2) an
abdomen with soft, thin, muscular walls. Divide the
skin along the median ventral line for the entire length
of the body, and strip it back, away from the sides.
Cut away the ventral muscular wall of the abdomen.

VERTEBRATES,

Make a longitudinal lateral cut through the middle of the
ribs, and remove the ventral wall of the thorax, dissecting
it carefully away from its attachments to the internal
organs.

The diaphragm is the transverse muscular partition
found attached to the posterior borders of the ribs. It is
the boundary between thorax and abdomen. Lift up its
severed ventral margin, and note its shape, convex toward
the thorax, and concave toward the abdomen. Observe a
thin tendon at its center. The muscular libers composing
it arise from the walls of the body cavity, and converge
toward their insertion into this central tendon. When
these contract, they draw the tendon posteriorly, increas-
ing the capacity of the thorax.

Internal Features. — The large, dark-colored liver lies
close against the posterior side of the diaphragm. The
capacious stomach lies partly concealed by the liver, and
posteriorly nearly the entire cavity of the abdomen is
filled with intestine, slung from the dorsal side of the
cavity in folds of the mesentery.

The pink lungs, lying free in the thoracic cavity, rest
against the anterior surface of the diaphragm. The heart,
within its pericardium, lies between the lungs, its apex
normally resting upon the diaphragm.

Note the following parallelisms in the linings of thoracic
and abdominal cavities. The abdomen is lined with a
thin, transparent, and closely adherent membrane (the
peritoneum), which, on the dorsal side, is reflected ventrally
in a double fold (the mesentery) enveloping the viscera.
The thoracic cavity is lined with a similar membrane (the
pleura), which is also reflected ventrally from the dorsal
side to form a double fold (the mediastinum), which, at the
base of each lung, is reflected completely over it, so as to
inclose it as within a bag. Between the two lungs there

THE RABBIT. 245

is thus left a mediastinal cavity, within which the heart
and its pericardium lie. The pleura lining the thorax
and covering the lung may be readily seen when lifted
with a needle point.

The Digestive System. — The organs of digestion have
been noted as far as the esophagus. The esophagus de-
scends straight through the thorax, perforating the dia-
phragm, and entering the stomach on its concave anterior
border. Note the shape and size of the stomach, the point
at which the esophagus meets it, and the point at which the
intestine springs from it. At the origin of the intestine
is the pylorus, an internal valvular fold which guards the
passage, and prevents the premature exit of the food. The
first part of the intestine is the duodenum, a narrow por-
tion extended along the right side of the abdominal cavity,
and folded upon itself, to form a long, narrow loop. Into
this part the ducts from the gall bladder and the pancreas
open. The gall bladder is situated under one of the five
lobes of the liver, and is of a dark-bluish color. Its duct
(usually appearing brownish in color) extends posteriorly
to open into the duodenum, not far from the pylorus.
The duct is about an inch and a half long. It may be
made very plain by squeezing the contents of the gall
bladder out into it.

The pancreas is whitish in color, and diffuse in form.
It is a loosely aggregated mass, completely surrounded by
the duodenal loop. Its short white duct opens near the
middle of the distal half of the duodenum.

The small intestine is the long posterior continuation of
the duodenum. It is of about uniform diameter, and is
looped up in numerous folds of the mesentery.

The ccecum is the long lateral pouch into the end of
which the intestine opens. It is the most conspicuous
part of the digestive tract, on account of its ventral posi-

246 VERTEBRATES.

tion and its great size. It is a sort of food reservoir,
It ends blindly in a narrow, thick-walled, finger-shaped
process (the vermiform appendage).

The large intestine completes the alimentary canal. It
is distinctly sacculated at its anterior end, becoming
smooth posteriorly.

These organs can be freely examined in place. Their
attachments should not be severed until after the blood
vessels have been studied.

The spleen is a dark-red body lying behind the stomach,
and attached to its left end.

Renal Excretory System. — A pair of compact, brown-
ish, bean-shaped kidneys lie closely attached to the dorsal
wall of the abdominal cavity. Notice that the right one
is anterior to its fellow. Observe a large artery entering,
and a large vein leaving, each kidney. Observe also a
long white duct (a ureter) extending posteriorly from
each kidney, to open into the urinary bladder, a whitish
membranous sac lying ventral to the posterior end of the
large intestine. Associated with the afferent duct of the
bladder are the passages from the reproductive organs;
and the external aperture for these is separate from the
anal aperture.

The Circulatory System is very similar to that of a bird.
The heart is four-chambered, consisting of right and left
auricles and ventricles. The boundaries of these cham-
bers are evident from the outside ; but the heart should be
dissected later, to show the relative thickness of the walls
of these chambers, and the valves, which prevent the
return of blood at the entrance to the ventricles and to
the aorta.

I. The Venous System. — The blood is brought to the
heart through right and left prcecavce and the single
large postcava. These three vessels enter the right

THE RABBIT. 247

auricle. The principal branches of each prgecava are
three : (1) a jugular vein coming from the head ; (2)
a subclavian vein coming from the shoulder and fore
limb ; and (3) a mammary vein coming from the ventral
wall of the thorax. The principal branches of the
postcava are the short, wide hepatic veins entering it in
the liver, the renal veins coming from the kidneys, the
spermatic (or ovarian) veins (according to sex) coming
from the reproductive organs, and the large external iliac
veins coming from the hind limbs. The last-named are
called femoral veins posterior to the abdominal cavity.

Another set of veins, constituting the portal system, col-
lects the blood from the digestive organs of the abdominal
cavity, and carries it through the portal vein to the liver.
This blood percolates through the substance of the liver
before being collected again into the hepatic veins.

II. The Pulmonary System. — The blood collected into
the right auricle descends, through an opening guarded
by a valve, into the right ventricle, whence it is expelled
to the lungs through the pulmonary arteries. These arise
together from the anterior border of the ventral surface
of the auricle, and, arching about the left auricle, separate,
and go direct to the lungs. After distribution through
the capillaries in the walls of the air cells of the lungs,
the blood is collected into the pulmonary veins, and
returned directly to the left auricle. The pulmonary
artery and vein and connecting capillaries constitute the
pulmonary system. The obvious purpose of this part of
the circulatory system is the aeration of the blood.

III. The Arterial System. — From the left auricle the
blood descends, through an orifice guarded by a valve,
into the left ventricle, whence it is expelled through the
aorta. The aorta curves dorsally and toward the left side
of the body, and then extends posteriorly beneath the
dorsal wall and above the viscera. It gives off ante-

248 VERTEBRATES.

riorly near its origin a large innominate artery, and a
little farther out from the heart a smaller left subdavian
artery, which goes to the left shoulder, and thence to the
fore limb. A branch of the subclavian, which runs along
the inner side of the ventral wall of the thorax, is the
mammary artery. The innominate artery soon divides
off a left carotid artery, and then bifurcates into right
carotid and right subclavian arteries.

That part of the aorta which extends posteriorly beyond
the arch is called the dorsal aorta. It gives off in the
thorax a series of small intercostal arteries, which extend
laterally along the inner walls of the thorax, one behind
each rib. Its principal branches in the abdomen are three
single arteries, which pass ventrally through the mesentery
to the digestive organs, and three paired arteries.

The foremost of the single arteries (the cceliac artery)
arises close behind the diaphragm, and its branches are
distributed to the liver, stomach, and spleen ; the second
(the anterior mesenteric artery) arises a short distance be-
hind the first. Its branches supply the greater part of
the intestine. The third (the posterior mesenteric artery)
is small. It arises toward the posterior end of the abdomi-
nal cavity. Its branches are distributed to the hinder
end of the intestine.

Of the paired arteries, the foremost are the large renal
arteries, which go to the kidneys. The second are the
very small spermatic (or ovarian) arteries, which go to
the reproductive organs. % The hindmost are the very
large common iliac arteries, into which the dorsal aorta
seems to divide. Posterior to the body cavity, these are
called femoral arteries. Between the spermatic and com-
mon iliac arteries, several small lumbar arteries arise on
the dorsal side of the aorta, to be distributed right and
left to the dorsal abdominal wall, and to the thick muscles
of the back.

THE RABBIT. 249

It should be noted that the venous and arterial systems
roughly correspond to each other in the distribution of
their parts.

The Respiratory System. — That the lungs are envel-
oped in the pleura, that they are attached at their ante-
rior end, and float freely behind, within the thoracic
cavity, have already been noted. That they communicate
anteriorly with a pair of bronchi, which unite into the
trachea, will have been noticed in the dissection of the
blood vessels. How many lobes are there in the right
lung ? In the left ?

Observe that bronchi and trachea are made up of a
series of cartilaginous rings. On which side of the trachea
are these rings thickest, and why ? Note the absence of
any distinguishable syrinx at the division of the trachea
into bronchi. The voice organ in the rabbit is the
larynx, developed at the anterior end of the trachea.
The epiglottis stands at its anterior ventral border. It
is slightly wider and firmer than other parts of the
trachea. Dissect the larynx free from all its lateral
attachments, and observe that it is composed chiefly of
two rings of cartilage. The anterior one is wide in front,
but incomplete dorsally. It is called the thyroid cartilage.
The posterior one is a complete ring, wider on its dorsal
side. It is called the cricoid cartilage.

Make a median ventral slit down the larynx, and draw
apart the severed edges. Observe the thin sheets of
muscle and connective tissue which bind the cartilages
together. Two little nodules of cartilage within the
larynx, and on the dorsal side, are the arytenoids.

The two shallow, lateral depressions on the inner side
of the walls of the larynx are the ventricles. The pair of
delicate folds which form the posterior boundaries of the
ventricles are the vocal cords. These are folds of the

250 VERTEBRATES.

mucous membrane, or inside skin (which lines all the cavi-
ties of the body that have open communication with the
exterior), strengthened by slender elastic ligaments. They
are attached posteriorly to the arytenoids, by rotation of
which they are stretched across the tube of the larynx.
When fully stretched, the opening between them is but
a narrow vertical cleft. In this position they vibrate
readily in a passing current of air expelled from the lungs,
and they thus produce voice. A pair of folds of similar
appearance, at the anterior boundaries of the ventricles,
are the false vocal cords.

The Lacteal System. — The thoracic duct is a slender,
thin- walled tube which extends through the thorax length-
wise, close to, but a little above, the dorsal aorta. It is
formed by the union of numerous small vessels, called
lacteals, in the anterior part of the mesentery, in the
abdominal cavity. It perforates the diaphragm, and
passes directly forward to the anterior end of the thoracic
cavity, where it widens somewhat, and turns inward, to
open into the left preecava, near to its subclavian branch.
It receives in its course other lymphatic vessels from
nearly all parts of the body. These vessels form a sort
of drainage system for the tissues. The lymph they
bring, and the liquid products of digestion brought by
the lacteals from the intestine, are carried by the thoracic
duct, and emptied into the venous system, to mix and
commingle with the blood.

The pale, soft, glandular-appearing body, through which
the curved anterior end of the thoracic duct passes before
entering the prsecava, is the thymus.

Spinal and Sympathetic Nerves. — The spinal nerves
may be seen through pleura and peritoneum, in the dorsal
wall of the body cavity.

A double chain of sympathetic ganglia extends along

THE RABBIT. 251

close beside, and ventral to, the spinal column. The
ganglia are connected with one another, and with the roots
of the spinal nerves, by commissural nerves. These are
very difficult of dissection.

Removal of the Brain. — Cut away the top of the cra-
nium, and expose the brain fully. The elongate oval
olfactory lobes at its anterior end will be conspicuous.
Cut these off as far forward as possible, and gently lift the
brain out of the cranial cavity, on a thin, narrow blade of
metal, watching closely, and severing the roots of the
cranial nerves as fast as they appear, leaving as great a
portion of each as possible attached to the brain. Twelve
pairs of cranial nerves should be found during this oper-
ation. Proceeding from the front, these are : —

1. The olfactory nerves, the roots of which were cut
off at the anterior end of the olfactory lobes of the
brain.

2. The optic nerves, large and conspicuous, at first
diverging but little, as they extend forward from their
point of crossing on the median ventral line.

3. Two pairs of slender nerves, Appearing behind the
crossing of the optic nerves.

4. The trigeminal nerves, very large and conspicuous,
arising a little farther back, and a little more remote from
the median ventral line.

5. Two pairs of slender nerves, close behind the tri-
geminal, the anterior pair somewhat nearer the median
line.

6. The auditory nerves, which are large, and which
arise a short distance behind the trigeminal, but farther
from the median line.

7. Two pairs of rather small nerves, which arise close
behind, and a little above, the auditory nerves. The
larger pair of these are the vagus nerves.

252 VERTEBRATES.

8. Two pairs, which arise, by many slender rootlets,
from the ventral surface of the hindmost part of the
brain, rootlets of one pair in part from the anterior end
of the spinal cord.

Parts of the Brain. — Cut off the spinal cord, and place
the brain in a little alcohol, for a superficial examination
of its parts. On the dorsal side, note the large, smooth,
cerebral hemispheres immediately behind the olfactory lobes,
and in the posterior angle between them, 011 the median
line, the pineal body. Posterior to the hemispheres, the
cerebellum covers the greater part of the dorsal surface.
It is made up of a large, transversely ridged, central lobe;
a pair of oblique, lateral lobes; and, on its outer edges, a
pair of small, rounded, floccular lobes. The dorsal sur-
face of the medulla appears behind the central lobe of the
cerebellum.

On the ventral surface observe the olfactory lobes,
extending backward, beneath the anterior end of the
hemispheres. Observe that a large, oval, temporal lobe is
marked off on the ventral surface by a shallow groove
from the remainder „ of each hemisphere. Observe the
crossing of the optic nerves. They may be traced out-
ward and backward to the concealed optic lobes by turn-
ing the temporal lobes of the hemispheres aside. Close
behind the crossing of the optic nerves find a narrow
median slit, the aperture of the infundibulum, leading
down into the pituitary body, which was probably left be-
hind in the base of the cranium when the brain was
removed. The floccular and lateral lobes of the cerebel-
lum are visible on either side, and these are connected
across the ventral surface by a stout band of nerve fibers.
The medulla, tapering posteriorly, and studded with nu-
merous nerve roots, forms the remaining posterior part of
the ventral surface.

THE RABBIT. 253

The Skeleton. — The axial part consists of the spinal
column (composed of vertebrce) and of the skull. The
bones of the whole axial series are perforated, and so
placed together, end to end, as to form a canal, which
lodges and protects the central parts of the nervous sys-
tem, — brain and spinal cord. The vertebral series also
forms a very strong yet flexible support for all other
parts of the body.

I. Vertebrae and Ribs. — The vertebra may be con-
sidered as forming five groups : (1) cervical (or neck)
vertebrce; (2) thoracic (or chest) vertebrce, which bear
movably articulated ribs ; (3) lumbar (or back) vertebrce,
without ribs, the largest of the series ; (4) sacral verte-
brce, which are fused together, and support the bones of
the pelvis ; and (5) caudal (or tail) vertebrce. How many
vertebrae are there in each of these five groups ?

Examine one of the middle lumbar vertebrae as a type,
and in it find the usual parts, — centrum, neural arch, neural
spine, transverse processes, and articular processes. Find
also a median ventral process (hypapophysis) projecting
downward directly from the centrum. A pair of flat
plates of bone (epiphyses) may be found applied to the
ends of the centrum, if the vertebra be that of a young
animal. These become anchylosed with the centrum
with age.

The transverse processes of the cervical vertebrae are
broad and flat and perforated, and the series of perfora-
tions forms an imperfect canal for the passage of a nerve
and an artery. The parts of the transverse processes out-
side the perforations are homologous with the ribs of the
vertebrae farther back.

Note that each distinguishable rib has two articulations
with its vertebra, — a head, which meets the centrum ; and
a tubercle, which meets the transverse process. The space
inclosed between these two articulations corresponds

254 VERTEBRATES.

roughly to the perforation in the transverse process of
the cervical vertebra. Examine one of the ribs near the
middle of the series, and note its shape, position, and
range of movability. Note that it has a sternal as well
as a vertebral portion, and note that the sternal portion
is more or less cartilaginous. Note that the central part
of the sternum, to which the ribs attach at their distal
end, is transversely segmented. Observe that the fore-
most segment (the manubrium) is large, and is produced
anteriorly in a prominent keel. Observe that the hind-
most segment (the xiphisternum) is a slender rod of
bone, supporting a broad, flat cartilage. Which ribs are
shortest ? Which longest ? Which have no sternal por-
tion ? Which have but one articulation with their corre-
sponding vertebrae ? Which articulate partially with other
than their own vertebras ?

Note the decrease in size of the vertebrae posterior to
the first sacral, and the gradual disappearance of all the
processes.

II. Atlas and Axis. — The first and second cervical
vertebrae show special adaptive modifications, and have
received special names. The first is the atlas. It bears
the skull upon two concave, articular surfaces, which
meet the occipital condyles of the skull. It has no
centrum ; or, rather, its centrum is probably the odontoid
process of the second vertebra. A transverse ligament
divides the very large perforation ; and the division of
it anterior to the ligament is occupied by this odontoid
process, around which the atlas rotates. The spinal cord
occupies the space posterior to the ligament.

The second vertebra is the axis. It has a broad, flat
centrum, produced anteriorly into the conical odontoid
process. A suture between this process and the centrum
is readily seen in young rabbits, and indicates that the
process has become attached to the second vertebra, while

THE RABBIT.

255

its position indicates that it may have belonged originally
to the first.

Study the action of atlas and axis, and note that the
head can be nodded backward and forward on -the atlas,
but that, in its rotation, the atlas turns round the odon-
toid process of the axis.

III. The Skull. — In the skull, note again the direction
of the teeth and their position in the jaws. Note the
articulation of the lower
jaw or mandible with
the remainder of the
skull. Observe the two
rounded occipital con-
dyles beside the foramen
magnum. Observe that
the orbits communicate
through the interorbital
foramen. Note that the
bones of the top of the

cranium meet each other SKULL OF RABBIT (gide

by jagged sutures.

The following bones should be readily distinguishable
in an adult skull. The occipital forms a complete bony
ring around the foramen magnum. It is formed origi-
nally of a number of separate occipital bones. Proceed-
ing forward on the dorsal surface, a small median inter-
parietal bone will be found fitted in between the front of
the occipital and the posterior angle between the two
parietals, which meet by a median suture directly in front.
The parietals form the greater part of the roof of the
cranial cavity. Anterior to the parietals, a pair of large
frontals complete the roof of the cranium in front, and
send out a large crescentic process above each orbit, and
form the dorsal third of the orbital wall. The frontals
meet by a median dorsal suture. Anterior to the fron-

256

VERTEBRATES.

tals, two long, narrow nasals complete the median dorsal
surface, and form the bony support of the snout. The
two stout bones which carry the upper incisors, and
which are situated beneath the nasals, and meet on the
median line in front, are the premaxillaries. Behind
them are the maxillaries, large and irregular, forming
the greater part of the skeleton of the upper jaw. Ven-
trally they bear the upper molars ; and each sends out a
stout lateral process, which forms part of the anterior

boundary of the orbit.
The nasal cavity
lies beneath the na-
sals and above the
maxillaries and pre-
maxillaries. Looking
into it from the front,
a number of thin,
irregular plates of
bone (the turbinals)
will be seen. The
anterior of these, the
more delicate and

SKULL OF RABBIT (dorsal and ventral views of complex jn structure,
cranium).

are developed from

the maxillaries, and are called the maxillo-turbinals. The
posterior are developed from the (concealed) ethmoid,
and are called ethmoturbinals. The ethmoid terminates
posteriorly in a transverse cribriform plate, set in the an-
terior end of the cranial cavity. This plate may be seen
in a skull from which the roof of the cranial cavity has
been removed. It is perforated for the passage of the
branches of the olfactory nerves to the nose. Within
the nasal cavity, the terminations of these nerves are dis-
tributed through the mucous membrane, which covers the
turbinal bones. The great extent of surface over which

THE RABBIT. 257

nerve endings can come into contact with the air corre-
sponds with the keen sense of smell possessed by the
rabbit.

The lachrymal bone of each side forms a large part of
the anterior wall of the orbit, and joins the frontal by a
suture above.

The squamosal bones form the greater part of the con-
vex lateral walls of the cranial cavity, and send out a
stout lateral process to form part of the posterior border
of the orbit. The flattened bars of bone which connect
this process of the squamosal with the corresponding
backward process from the maxillary, and complete the
outer border of the orbits, are the molars (or cheek bones).

Two (composite) bones remain to be found on the
median ventral surface of the cranium. These are the
basisphenoid, which has a triangular body (seen from
below) and two flattened, wing-shaped, lateral processes,
and which is situated immediately in front of the occip-
ital ; and the presphenoid, a narrow bone in front of the
basisphenoid, extended upward into a thin median plate
between the orbits, and perforated by the interorbital
foramen.

The pterygoids are two narrow, vertical plates of bone,
attached to the base of the skull at the lateral junction
of the two sphenoids. Each has a free posterior border,
which ends below in a curved process.

The palatines are two nearly vertical plates of bone,
which extend forward from the pterygoids, form the
lateral walls of the posterior nasal opening, and meet each
other on the median line of the roof of the mouth by
horizontal platelike processes.

IV. Shoulder Girdle and Arm Bones. — In the shoulder
girdle the three usual bones of each side may not be at
first recognizable. The scapula is a large, flat, triangular
bone, expanded at the end which forms the apex of the

NEED. ZOOL. — 17

258 VERTEBRATES.

triangle, and hollowed there to form a. cavity, into which
the head of the humerus fits. The coracoid is not a sepa-
rate bone in the adult rabbit, but only a curved process
attached to the scapula, and overhanging the head of the
humerus. The clavicle is a slender, incomplete bone,
developed within a ligament which extends from the
sternum to the scapula.

The bones of the fore limb are humerus, radius, ulna,
carpal and metacarpal bones, and phalanges. All these
are easily recognizable. The humerus is the single bone
of the upper arm. The ulna is the larger of the two
bones of the forearm. Its enlarged proximal end bears
the olecranon process, which forms the angle at the elbow.
Both radius and ulna have a thick cap or transverse plate
of bone (epiphysis) more or less completely coossified
with the shaft of the bone. The small carpal bones are
arranged in two transverse TOAVS, — three bones in the
proximal row, and four in the distal row, — with a single
minute, roundish bone between the rows, on the median
line. The metacarpals are a transverse series of elongated
bones (the inner one short) ; and the phalanges (or finger
bones) are two in the inner digit or thumb, and three in
each of the other digits.

V. Pelvic Girdle and Leg Bones. — In the pelvic girdle
the usual three bones of each side are, as usual, fused with
each other, and firmly attached to the sacral vertebra.
The two sides of the girdle are united also in a ventral
symphysis. Each of the three takes part in the formation
of the deep cup-shaped acetabulum, in the sides of which
the boundaries between them may readily be seen in
young specimens. The ilium forms the anterior part of
the girdle on each side. It is broadly flattened in front,
narrowed behind, and it forms about half of the acetab-
ulum. The ischium is posterior and dorsal, and forms
about one third of the acetabulum. Its posterior portion

THE RABBIT. 259

is flattened and thickened at the margin, to form the
tuber osity of the ischium. The pubis is ventral. It is
separated in part from the ischium by the large, oval
obturator foramen ; but the ventral symphysis, uniting the
two halves of the pelvic girdle, is formed of both ischium
and pubis on each side, and the boundary line between
them is not discoverable except in very young speci-
mens.

The bones of the hind limb are femur, tibia, fibula, tar-
sal, metatarsal, and phalanges, and a few small sesamoid
bones, developed in the tendons at some of the joints,
and not forming a part of the skeleton proper. The
largest of these sesamoid bones is the patella (or knee-
pan), developed in front of the knee joint in the tendon
of the extensor muscles of the leg.

The femur is the single bone of the thigh. The large
bone of the shank is the tibia ; the small one, distinct at
its proximal end, but fused with the tibia distally, is the
fibula. The tarsus, like the carpus, consists of two trans-
ver^se rows of small bones, with a single bone between the
two rowso- The proximal row consists of two relatively
large bones, the distal row of three smaller ones, while
the single bone between the rows is at the inner side of
the foot. The metacarpals are a transverse series of four
elongated bones, and the phalanges are three in each digit.
The first digit of the foot, corresponding to the great toe,
is wanting.

The rabbit is a representative of the vertebrate class
Mammalia (the mammals, or milk-givers).

A cat or dog may well be studied, as showing the car-
nivorous type of mammalian structure ; and a bat, as
showing the adaptation of mammalian structure to aerial
locomotion.

260 VERTEBRATES.

THE LIFE PROCESS IN VERTEBRATES.

The life process is essentially the same in all animals,
differing in different animals only in the means by which
it is carried out. The perfection of the means — the
adaptation of the means to new and higher conditions
of life — has made the vertebrates the dominant group
among animals.

I. Nutrition. — The organs subservient to nutrition have
been grouped as organs (1) of digestion, (2) of circulation,
(3) of respiration, and (4) of excretion; and to these
might be added (5) organs of prehension, for grasping food,
and (6) organs of mastication, for chewing it, although the
organs of the last two groups are not exclusively sub-
servient to the nutritive function, and are not present in
all vertebrates.

1. Digestion takes place in the alimentary canal, parts
of which are specialized for the reduction of the food, and
other parts for the absorption of it when digested. Four
digestive secretions are poured upon the food normally
in its course, — saliva, from the salivary glands ; gastric
juice, from glands in the walls of the stomach ; bile, from
the gall bladder of the liver ; and pancreatic juice, from
the pancreas. The greater part of the digested food is
absorbed through the walls of the intestine, to be passed
into the circulation. In the highest vertebrates it is col-
lected by the lacteals of the mesentery into the thoracic
duct, and poured thence directly into the venous system.

2. Circulation is effected through a closed system of
blood vessels, consisting of the heart, arteries, veins, and
capillaries. Through this system the food dissolved in the
blood is carried to every vascular part of all the tissues.
The three types of circulation found in the vertebrates
studied are roughly outlined in the accompanying dia-

THE LIFE PROCESS IN VERTEBRATES.

261

gram. Their relation to the digestive, respiratory, and
renal organs is shown very diagrammatically.

3. Respiration is effected by means of gills or of lungs.
In those vertebrates which have naked, moist skins, it is
probable that considerable air is absorbed directly through
the skin.

When the blood has been replenished and aerated, ma-
terials have been supplied for all the chemical changes

Fish or Tadpole.

Adult Frog.

Eabbit.

COMPARATIVE DIAGRAM OF CIRCULATION, SHOWING IN A GENERAL

THE COURSE AND DISTRIBUTION OF THE BLOOD : V, ventricle ; G, gills ;
P, lungs and pulmonary vessels ; L, liver ; S, stomach ; /, intestine ;
K, kidney. Black vessels carry venous blood ; light ones, arterial blood.
Arrows indicate the course of circulation.

(metabolism) which take place in the tissues. The con-
structive processes (anabolism), by which the food be-
comes tissue ; .and the destructive processes (katabolism),
by which the tissue becomes waste water, carbonic acid,
etc., — are, so far as we know, the same in all animals;
and the end of this building-up and tumbling-down of
organic molecules, in "continual round of change," is the
production of heat, motion, nerve force, etc., necessary to
the animal's life and activities.

262 VERTEBRATES.

4. Excretion is performed by the skin, the lungs, and
the kidneys.

II. Reproduction. — As in all other animals except pro-
tozoans, reproduction in vertebrates is by means of eggs.
The sexes are distinct in all, and the eggs are fertilized
either within or without the body of the parent. In the
mammals the eggs are retained and developed within a
specialized part of the oviduct, the uterus (or womb). The
young are born after their embryonic life is past, and are
nourished with milk secreted in the mammary glands of
the female. Throughout the group, and throughout the
animal kingdom, the decrease in the number of progeny
is proportionate with their increased security from ene-
mies during the period of development.

III. Voluntary Motion. — An internal skeleton, usually
of bone, furnishes support and points of attachment for
the muscles of the vertebrates. The muscles overlie, and
more or less completely envelop, the bones. This is a
radically different arrangement of skeleton and muscle
from that found in crustaceans and insects. The muscle
fibers of vertebrates are insheathed together in connective
tissue, and often inserted into tendons, affording them
greater unity and efficacy of action.

The limbs of vertebrates are never more than two
pairs, and may be entirely wanting. They are usually
developed for locomotion : as fins for swimming ; wings for
flying ; legs for walking, running, leaping, etc. Locomo-
tion is aided in fishes by unpaired fins, and by the stout,
muscular tail ; and in some reptiles (snakes), by the move-
ment of the spinal column and ribs. Movable tactile
organs, such as the barbels of fishes and the "whiskers"
of mammals, are often present. Some of the most clumsy,
ungainly, armor-encumbered animals, as well as some of
the fleetest and most graceful on land, in air, or in water,
are found among the vertebrates.

THE LIFE PROCESS IN VERTEBRATES. 263

IV. Sensation. — The position of the central nervous
system (i.e., of the brain and spinal cord) in vertebrates,
dorsal to the center of the bony axis of the skeleton, and
inclosed within a dorsal, neural canal, is very charac-
teristic of the group. In the lowest, the brain is but
little developed at the anterior end of the spinal cord;
but, as we ascend the vertebrate scale, it becomes more
and more highly specialized. The cerebral hemispheres,
which are the seat of intelligence, reach their relative
maximum development in man. The spinal and cranial
nerves are distributed to all the muscles of the body, to
the skin, and certain of them to the blood vessels and
to the internal organs ; and all these parts are thus placed
in communication with the nerve centers. A double
series of sympathetic ganglia extends along the dorsal
wall of the body cavity, and sends nerves to the digestive
and reproductive organs.

The five senses of man are probably possessed in vary-
ing degrees by all other vertebrates, and each of the
five is probably keener in some other animal than in
man.

Of the higher possibilities of the vertebrate brain it is
impossible to speak here. Volumes would be required to
adequately summarize the wonderful and infinitely varied
instincts of fishes, batrachians, reptiles, birds, and mam-
mals. A few of these have been pointed out in the cases
of the types studied : others invite study in every locality,
on every hand. Such study will not be amiss if it lead
to the study of the instincts that move men.1 It will be
especially valuable if the student see, that in proportion
as man learns to govern his instinctive impulses, and be-
comes a creature of ideals, he ascends above the level of
the brute.

1 For a good discussion of this subject, the student is referred to the
closing chapters of Chadbourne's Instinct in Animals and in Man.

264 VERTEBRATES.

Evolution. — In animal structure the student cannot
fail to discover increasing complexity. That there is
not one single complete and uniform series from the low-
est to the highest, is true ; but that there is more or less
regular gradation, is unmistakable. In the embryonic
life of one of the higher animals there is corresponding
gradation. In the development of the original single cell
(the oosperm) there is increasing complexity of structure,
and the main types of structure found in other animals
lower in the series are one by one roughly repeated.
Geology presents a corresponding gradation in the forms
of life which have appeared at different periods of the
earth's history, and plainly shows that the present fauna
of the earth is not like that of any preceding geologic
period. The fossil remains of animals preserved in the
rocks show in a general way that the simpler forms ap-
peared first, and that the most complex are of most recent
introduction. These facts, and others, seem to indicate
that there has been a continual progressive development
of animals from simple, primitive forms ; and such devel^
opment is denoted by the term evolution. A partial ex-
planation of the manner in which evolution may have
come about is found in the law of natural selection,
which assumes that indefinite variations in animals are
continually occurring, and shows that such variations in
structure as fit an animal better for maintaining its place
in nature will be preserved through successive genera-
tions, and may become permanent.1

Animals and Plants. — In the foregoing pages plant
life has been but incidentally referred to, yet enough has
been said to suggest the close interdependence of plants

1 For a concise and able exposition of this law, the student is recom-
mended to read the chapter on "Natural Selection" in Morgan's Animal
Life and Intelligence.

THE LIFE PROCESS IN VERTEBRATES. 265

and animals. If a like study of typical plants were made,
it would reveal a corresponding gradation in form and
function from the lowest to the highest. It would lead
us to the conclusion that the plant life of the present ia
related to that of the past by direct descent. We should
find protoplasm the physical basis of plant life, and the
cell the unit of plant structure ; and at the bottom of
the series we should discover that there are free plant
cells which move about by pseudopodia and by cilia,
arid so combine in themselves the characters by which we
commonly distinguish animals from plants, that we are
almost unable to determine what characters predominate.
We thus come to the conclusion that life is a unit, and
that the higher and familiar forms are at extremes of the
divergent paths along which it has progressed.

The study of animals should lead to a better under-
standing of man in his physical relationships. Not the
remotest object of the foregoing course is, that it shall
serve as an introduction to the elementary study of human
anatomy and physiology. The lowest animals have some
points of structure or of function in common with man ;
and these points become more numerous and more ap-
parent as we ascend the animal scale, until the greater
part of all that is written in the chapter concerning the
rabbit will apply almost equally well to the study of the
human body. The human body is governed by the same
laws, subject to many of the same necessities, and influ-
enced by many of the same instincts, as affect other
animal bodies ; and the student should know that it is on
the normal healthful activity of this animal body that all
the possibilities of happiness and usefulness in human life
depend.

ECHINODERMS.

THE STARFISH.

(Asterias.')

Haunts and Habits. — Dwellers by the sea are familiar
with the curious red "sea stars," "starfishes," or "five
fingers," as they are popularly known, which settle in
troops upon the beaches at times, with the wash of cur-
rents and tides. Along the northern coast of New Eng-
land they are very common. They should be studied
alive if possible, and in their native haunts ; for, from the
dried or alcoholic specimens common in collections, one
will obtain but a poor notion of the life these creatures
lead. Upon the beach one may see them sprawling flat
upon the sand, or slowly crawling over and among the
rocks with their arms, which are so rigid in preserved
specimens, bent in a great variety of positions. One may
sometimes be found with its arms folded about an oyster
or other mollusk on which it is feeding.

Study of the Live Specimen.1 — 1. Observe a fringe of
active cylindrical worm-like process about the tip of each
arm of a moving starfish. These are its tube feet. In an

1 Live starfishes may be brought into the laboratory and kept alive for
several days if kept in a sufficient quantity of sea water, or if the supply
of oxygen in the water be once in a while renewed (as by dipping and
pouring it back into the vessel from some little height above the surface).
They may be had alive at some distance in the interior if shipped in kegs
of sea water, and studied very soon after their arrival.

260

THE STARFISH.

267

upturned arm note that these spring from a groove which
extends along the lower side of the arm its entire length.
Observe that these tube feet are pushed out and drawn in

STARFISH. — 1. Starfish (Asterias vulgaris), a large dried specimen one half
natural size. 2. Diagram of cross section of oral part of an arm : br,
branchial tentacle ; sk, calcareous plate of skeleton (in heavy black) ; sp,
spines (those designated are on an adambulacral plate); amp, ampullae;
c, radial canal; n, radial nerve; amb, ambulacra, or tube feet. 3. Dia-
gram of water-vascular system: ra, madreporite; sc, stone canal; coc, cir-
cumoral canal; re, radial canal; amp, ampullae ; amb, ambulacra.
4. Starfish infolding an oyster preparatory to eating it. 5. Diagram of
parts of digestive and reproductive organs, etc.: st, stomach; h, hepatic
caeca ; o, ovaries ; amp, ampullae ; ambp, ambulacral plates as seen when
ampullae are removed.

and turned about freely, and that in locomotion they are
advanced in the direction in which the animal is moving,
attached by means of terminal disks, and then contracted,

268 ECHINODERMS.

drawing the body of the animal forward with a slow,
gliding motion.

2. Turn an active starfish upside down, and observe
how the arms are bent, and the tube feet used in righting
itself.

3. Place a live specimen in a shallow dish of sea water,
and with a lens examine it very near the surface of the
water, to find about the bases of the rigid, blunt, conspic-
uous spines numerous smaller ones, some of which are two-
parted at the tip (pedicellarice), and which are continually
snapping. These are believed to keep the surface clean
by preventing a deposition of sediment.

4. Observe also between the blunt spines numerous
conic or cylindric soft membranous processes, protruding
sacs filled with fluid (branchial tentacles). Test the sen-
sitiveness of these and of the tube feet to touch.

External Features. — Use either alcoholic l or freshly
chloroformed specimens, the latter when readily obtain-
able. Observe : —

1. That the flattened body consists of a disk and a
number of radiating arms. Are the number and size of
these the same in all specimens ?

2. That it presents two well-marked surfaces : —

(a) A flat surface on which it crawls, in the center of
which is the mouth, and from this fact called the oral surface.
(6) A concave upper aboral surface.
On the oral surface note : —

1. The round mouth, with the thin crumpled walls of
the stomach often seen protruding from it.

2. The deep and wide grooves extending from the
mouth to the tip of each arm. As these lodge the tube
feet, or ambulacra, they are called ambulacral grooves.

1 If alcoholic specimens have acquired a disagreeable smell, this may
be overcome by adding a few drops of oil cassia to the alcohol.

THE STARFISH. 269

3. The slender and somewhat movable spines which
border the grooves, and which may be approximated to
cover the retracted tube feet.

On the aboral surface note : -

1. A low convex tubercle located between the center of
the disk and the junction of two of the arms. This is
the madreporite (named from its superficial likeness to
madrepore coral). Examine with a lens.

2. At the tip of each arm a minute reddish spot,
the eye.

3. Note again the arrangement of spines and branchial
tentacles.

Internal Anatomy. — Divide the crust along the lateral
margins and across the tip of the two arms which border
the madreporite between oral and aboral surfaces, being
very careful to cut no deeper than the crust. Continue
the cut entirely around the disk and across the bases of the
other arms. Then make a shallow, circular cut around
the madreporite, so that, when the loosened aboral crust is
lifted, this will remain in place. Then carefully lift the
crust, beginning at the end of an arm, looking beneath it
as it is lifted, and freeing it from all its attachments.
Observe that a pair of glandular organs (hepatic cceca) in
each arm lifts with the crust, being suspended from it
by membrane (mesentery). Along with these, and lying
above them, may be found also a pair of paler and more
granular reproductive organs. As the crust is lifted,
the hepatic caeca may be traced to their union in the base
of the arms before entering the stomach. The repro-
ductive organs may be traced to their (ovi- or sperm-)
ducts, which diverge on reaching the disk, each passing to
meet at its external aperture the duct of a similar organ
in the adjacent arm. As the crust of the disk is lifted,
there may be found the narrow terminal portion of the

270 ECHINODERMS.

alimentary canal attached at its minute anal opening on
the aboral surface.

The Digestive System. — With the aboral crust properly
removed, the digestive organs will be fully disclosed.
Oral and aboral openings of the alimentary canal have
been noted. By probing with a stiff wax-tipped bristle
through the mouth, learn how restricted are esophageal
and intestinal areas of the alimentary canal, and how very
capacious and wide is the stomach. In the latter find : —

1. A loose, baggy oral portion which may be protruded
through the mouth, and which has muscles for its re-
traction. In feeding, the starfish commonly protrudes
this portion out of its mouth and in between the valves
of the shell, and digests the oyster there.

2. An aboral portion of more definite shape, with which
the hepatic caeca communicate. Probe the ca3ca.

The Water- Vascular System. — Study this in an injected
specimen.1 Observe : —

1. A vessel extending downward from the madreporite
beside the stomach toward the mouth. This is the stone
canal, so called because calcareous matter is found in its
walls.

2. Circumoral canal, into which the stone canal opens.

3. A series of radial canals extending outward from
the circumoral canal, lodged deep in the ambulacra] groove
on the underside of each arm.

4. A double row of round water sacs called ampullae
within each arm on its floor on either side of a median ridge.

5. Two double rows of ambulacra, or tube feet, in cor-
responding position on the oral surface of each ray. Snip

1 The water-vascular system may be injected by inserting a cannula
into each radial canal near the tip of the arm, and injecting toward the
disk, forcing the water out at the madreporite.

THE STAKFISH. 271

off the tip of a tube foot, and, by probing through it with
a slender bristle, determine its relation to the ampullae
above. Determine the relation of the ampullae to the
radial canal. Pull off a tube foot entire, and dissect it in
a drop of clove oil or glycerine, under a lens, to see the
delicate muscle fibers in its walls, and the oblique fibers
near its tip, which are inserted into the middle of the ter-
minal disk. How does the starfish maintain its foothold ?

Circulatory System. — Beside the stone canal, there may
be seen in a starfish that has been opened alive a delicate
pulsating tube, sometimes called the heart. The blood
vessels which run out from this are so minute as to be
traceable only by sectioning.

Nervous System. — A portion of the nervous system
may be seen on the oral surface without dissection, as it
is covered only by transparent epithelium. Find : —

1. A circumoral nerve wing.

2. Radial nerves extending out from the latter along
the oral side of the radial canals to the tip of the arms.

3. Masses of nerve tissue, called ganglia, at the junction
of the radial nerves with the circumoral ring.

4. A pigmented spot, called the eye, at the distal end
of each radial nerve.

The Body Wall. — If almost any portion of the body
wall be examined in cross section, about three layers will
be distinguished in it.

1. A tough outer membranous layer of epithelium
covering the whole animal except the spines.

2. A middle layer of connective tissue, in which are
imbedded the calcareous plates which make up the hard
parts of the skeleton.

3. A thin lining layer of peritoneal epithelium. This

272 ECHINODERMS.

is pushed out through holes in the middle layer to line
the branchial tentacles, and is infolded to form the mesen-
teries. Pass a slender probe into a branchial tentacle.

Boil a portion of an arm in potash solution, to remove
the connective tissue which holds together the calcareous
plates. When these seem about ready to fall apart, wash
and separate them, to see how they are put together.
Find : —

1. A double row of ambulacral plates, meeting by their
ends at an obtuse angle to form the gable roof of the
ambulacral furrow.

2. On either side a bordering row of adambulacral
plates.

3. Other plates irregularly disposed in other portions of
the body wall.

What is the shape of the plates of all these sorts, and
how are they put together?

Between the walls of the alimentary canal and the body
walls is a distinct body cavity which the blood (hemo-
lympTi) occupies. The hepatic cseca and the reproductive
organs are extended laterally into it, as already noted.

Life Process. — Only in the details for carrying out
the vital processes do we find anything new or unusual in
the starfish.

I. Nutrition. — The digesting of a mollusk in its own
shell without having been swallowed is unusual ; but, when
we remember that digesting is mainly dissolving prepara-
tory to absorbing, we see that the difference is merely one
of position. Digested food passes directly into the blood
by osmosis, and is carried with currents set up by the feebly
pulsating circulatory apparatus. In the branchial tentacles
it is properly exposed for aeration ; and in all the tissues,
as ever, its constituents are selected by the individual
cells for use.

THE STARFISH. 273

II. Reproduction. — Ova and sperms in immense num-
bers escape into the water, where fertilization takes place.
The resulting oosperm in its development passes through
the segmentation and gastrulation stages described for
the snail (pp. 158, 159), the irregularities there noted
being absent from the more typical development of the
starfish. The gastrula develops into curious larval forms
{Bipinnaria and Brachiolaria),for description of which the
student is referred to the larger text-books of zoology.
The larval forms are strictly bilateral. Were it not for
the persistent bilaterality of the water-vascular system,
the symmetry of the adult would be radial. The change
from larval to adult form is so great as to simulate meta-
morphosis.

Lost parts, especially arms, are readily reproduced.

Voluntary Motion and Sensation present no important
phases not already noted in preceding pages.

The starfish is a representative of the large group
Echinodermata, a group which has no fresh-water rep-
resentative. Other echinoderms are crinoids, sea urchins,
and sea cucumbers.

NEED. ZOOL. 18

APPENDIX.

PREREQUISITES.

In order to use this book advantageously, there will be needed : —

1. In Charge of the Course. — A teacher with some time and
opportunities at his disposal for acquainting himself and his classes
with the fauna of his locality.

2. In the Laboratory. — Plenty of light; plain desks or tables at
which students may work ; a few good microscopes, with the usual
accessories, — slips, covers, watch glasses, pipettes,1 etc.; the simple
reagents described on pp. 276 and 277 ; a water supply; receptacles for
organic refuse.1

3. In the Hands of every Student. — A good lens ; a scalpel; a small
pair of sharp-pointed dissecting scissors ; several dissecting needles ; l
a small forceps ; l bristles for probing ; a notebooks and pencils, for
descriptions and drawings.

4. In the Library. — A few good books of reference. All of the
following are recommended : —

Lang's Text-book of Comparative Anatomy. Recent and standard,

but expensive. (Macmillan & Co., New York.)
Marshall and Hurst's Practical Zoology. $3.50. (G. P. Putnam's

Sons, New York ; Smith, Elder, & Co., London.)
McMurrich's Invertebrate Morphology. $4. (H. Holt & Co.,. New

York.)
Thomson's Study of Animal Life. $1.50. (Charles Scribner's Sons,

New York.)
Jordan's Manual of the Vertebrates. $2.50. (A. C. McClurg & Co.,

Chicago.)

Edward Potts's Monograph of the Fresh Water Sponges. $1. (Obtain-
able from the author, at 228 South Third Street, Philadelphia.)
jCornstock's Manual for the Study of Insects. $3.75 net. This book

is especially commended to the general student of entomology.

(Comstock Publishing Co., Ithaca, N.Y.)

1 See note on cheap apparatus, p. 287.
275

276 APPENDIX.

French's Butterflies of the Eastern United States. $2. (J. B.

Lippincott Co., Philadelphia.)

Stoke's Microscopical Praxis. $1.50. (E. Bigelow, Portland, Conn.)
Darwin's Vegetable Mould and Earthworms. $1.50. (D. Appletoii

& Co., New York.)
Tryoii's Structural and Systematic Conchology. (Obtainable through

the Academy of Sciences, Philadelphia.)
Coues's Key to North American Birds. $7.50. (Estes & Lauriat,

Boston.)
Mivart's American Types of Animal Life. $2. (Little, Brown, &

Co., Boston.)
Wilder and Gage's Anatomical Technology. $4.50. (A. S. Barnes

& Co., New York.)

Chadbourne's Instinct. $2.50. (G. P. Putnam's Sons, New York.)
Morgan's Animal Life and Intelligence. $4. (Ginn & Co., Bos-
ton.)
Davie's Nests and Eggs of North American Birds. (Oliver Davie &

Co., Columbus, O.)
Davie's Methods in the Art of Taxidermy. The best book of its

kind that has yet appeared. (Oliver Davie & Co., Columbus, O.)
Bates's Naturalist on the Amazons. $1.50. A zoological classic.

(Roberts Bros., Boston.)

REAGENTS.

The following reagents and mounting media should be kept in
well-stoppered bottles, always available for use. They should be used
sparingly; but a quantity of any reagent, once used, should never be
poured back into the stock bottle.

Normal Salt Solution. — This is a f-per-cent solution of common
salt in water. It is useful as a mounting medium in which to exam-
ine, microscopically, fresh tissues, which wTould, like blood corpuscles,
be destroyed by the osmotic action of pure water.

Magenta. — A strong aqueous solution. This is useful for staining
fresh tissues for microscopic examination.

Methyl Green. — A strong aqueous solution, improved by the addi-
tion of 1 per cent acetic acid. This is a good and permanent stain
for either fresh or preserved tissues. It stains nuclei deeply, and is
therefore very useful for examining amoeba, pararnecium, etc.

Hydrochloric Acid. — Diluted with water, this is very useful for

REAGENTS. 277

decalcifying the armor of crustaceans, the shells of mollusks, and the
bones of vertebrates.

Nitric Acid. — This acid may be used for decalcifying, but it is
more expensive than hydrochloric. A 10-per-cent solution is useful
for macerating other tissues preparatory to a dissection of the ner-
vous system. If the bodies of small animals are kept in it for two
or three days, its destructive action on other tissues will leave the
nerves more easily accessible. Strong nitric acid is used for isolating
the spicules of fresh-water sponges.

Glycerine. — This is a very useful fluid in which to examine small
objects microscopically. A 25-per-cent solution greatly increases the
transparency of small objects soaked in it, making the structure more
evident.

Canada Balsam. — A sirupy solution, made by dissolving the dried
resin in turpentine or xylol, is an invaluable medium for making
permanent mounts of microscopic objects. Both air and water must
first be removed from the objects to be mounted in it. Hard, diy
objects, such as the claws of insects and the isolated spicules of
sponges, may be placed in a drop of balsam on a slip, heated gently
over an alcohol lamp or Bunsen burner to expel all air, and covered
with a thin cover slip ; but a less direct method must be employed
in mounting soft tissues. These must be covered first with weak,
and afterward with strong, alcohol, to remove the water they contain.
They must then be removed from alcohol into turpentine or xylol
for clearing. They may then be placed in a drop of balsam on a
slide, and at once covered.

Chloroform is very useful for removing excess of balsam from slips.

Alcohol. — The use of alcohol in dehydrating tissues for mounting
in balsam has already been stated. But one other of its many uses
in the laboratory will be mentioned here, — its use in preserving
specimens. In this use its action is the same as in the preparation
of specimens for mounting. It preserves objects by removing the
water from them. It removes the water by osmosis, and it is there-
fore weakened every time it is used by just so much water as it takes
from the tissues. Two grades of alcohol should ordinarily be used
for preserving specimens, — a weaker grade, in which the dehydration
is begun, and a stronger grade, into which they may be transferred
from the weaker, for permanent preservation. Alcohol of 70 to 80 per
cent strength, after osmotic action has ceased, is strong enough for
permanent preservation.

Turpentine, Xylol, Chloroform, Ether, etc., are used in their com-
mercial form, as directed in the text.

278 APPENDIX.

DIRECTIONS FOR THE PREPARATION OF MATERIAL FOR

STUDY.

The following directions are placed in the Appendix, because it
has not been found practical to have them carried out by beginners
in zoology. They are therefore intended for the teacher or for his
assistants. Anticipating that this book will fall into the hands of
some teachers who are not at all familiar with zoological laboratory
methods, a few of the simplest are given in the following notes, with
much detail which would be unnecessary were all who are called
upon to teach zoology fitted for the task by a laboratory training.
If the methods given below are not in all cases the best methods
known to science, they are believed to be the best that can be well
applied with such equipment as is usually provided for elementary
work in zoology.

I. On finding Amoeba. — The amoeba lives in the superficial ooze of
ponds and ditches everywhere, but it is not often very abundant. It
may be most easily obtained from shallow pools. To get it, scrape up
the superficial ooze from the bottom of the pool, avoiding the mud that
underlies the ooze, and place in a shallow dish with water. Allow the
ooze to stand undisturbed for a day or two. The amoebas will then
have come to the top of the ooze, whence they may be taken up with
a dropping tube. Place small drops — water, ooze, sediment and all
— on separate glass slips, and cover each with a thin glass cover slip.
The sediment in the drops will prevent the cover slips from crushing
the amoebas. The slips may then be searched quite rapidly, and
amcebas recognized, with a power of 250 diameters. A practiced eye
will recognize them with much lower power ; but the eye that does
not know just what to look for may pass them over even with this
amount of magnification. Higher powers cannot be used in searching
the field over without too great expenditure of time. The beginner's
trouble comes from the unlikeness of the clear jelly-like mass spread-
ing over the glass slip to anything commonly denoted by the term
"animal."

Amcebas are found also in the slime that covers the stems and
leaves of some submerged plants, and in the thin scum on the surface
of the water. The slime or the scum may be collected, and treated
in the same way as the ooze mentioned in the foregoing paragraph.

It is well to make separate collections from several places, to insure
finding amoebas.

THE PREPARATION OF MATERIAL. 279

II. Paramecium Culture. — Put a small bunch of hay into a
tumbler of pond water, and allow it to stand in a warm, well-lighted
place (not in the direct sunlight) for a few days or a week. This
will usually be an unfailing source of slipper animalcules. Drops of
water taken from the surface will be seen teeming with active minute
white specks visible to the unaided eye. The water of a vase in
which flowers have been kept too long will often furnish an abundant
supply.

These creatures swim so freely, that it is often difficult to keep one
in the field of the microscope. If a small tuft of fine cotton fibers
be lowered into the drop upon the slip before it is covered, some of
the animals are likely to be entangled in the meshes of the cotton,
where they may be studied alive. The cotton also supports the cover
glass, so that the animals are not crushed.

If their feeding is to be watched, finely powdered carmine or indigo
should also be put into the drop before it is covered.

A method of retaining paramecium within the field for examina-
tion, which usually proves more satisfactory, is to mount the animal-
cule in a drop of gum solution made by boiling cherry, peach, or
plum gum in water, and diluting to the desired fluidity, and covering.
The gum retains the animal, restricts somewhat the action of the cilia,
and its refractive properties render some structures more evident.

III. On finding Fresh-water Sponges.1 — The collector will need,
first of all, to know that an animal may be fixed in position, and green
in color.

The sponge recommended for study in this course (Myenia fiuvia-
tilis) may be looked for in the clear water of ponds and lakes and
quietly flowing bayous. It will hardly be found in muddy water or
in shallow water over a mud bottom. It grows in compact or lobed
cushion-like masses (often several inches in diameter) upon the stones
of the bottom, upon " water-logged " timbers, upon boughs drooping
in the water, etc. It is of a yellowish or brownish or green color. It
may be distinguished (under a lens) from vegetable growths of
similar appearance by the absence in it of leaves and of long, thread-
like fibers, and by the presence of osteoles, of bristling spicule points,
and (in autumn) of gemmules. Although it is cosmopolitan in its
range, there do not appear to be many localities of great abundance of
it. It should therefore be definitely located in advance of need, so that
fresh specimens may be at once obtainable when needed for class use.

1 The author has drawn largely upon the excellent monograph by Edward
Potts for the directions found in this and the next following sections.

280 APPENDIX.

In collecting, it is not enough to tear away the top of the sponge :
gemmules are most abundant in its deepest parts. A sharp hatchet,
with which a chip bearing the entire sponge may be detached from
submerged timbers, will therefore be found very serviceable. A broad,
dull knife blade may be used for detaching such as grow on large
stones. Specimens will be gathered most quickly by wading with
high boots in shallow water, and cutting them free from chunks and
stones which lie on the bottom. They will be collected most easily
when found growing upon partly submerged boughs of trees, which
may be drawn out of the water.

Specimens may be preserved in alcohol. The skeletal framework
will be readily preserved by drying the specimens in situations
sheltered from the direct rays of the sun.

IV. On preparing Gemmules and Spicules for Examination. — Dissect
out with needles half a dozen gemmules from the sarcode or from
the dried sponge mass. Place them together on the center of a clean
glass slip, and cover them with a drop of boiling nitric acid. After
five minutes (more or less, as may prove necessary time for rendering
their outer coat transparent without destroying it) wash off the acid
by running successive drops of water across the slide while holding it
in an inclined position. Then cut two or three of the gemmules in
halves or in quarters, so as to expose the edges of their outer coat.
Then remove the water, as much as possible with blotting paper,
and the remainder by adding strong alcohol. Renew the alcohol
once or twice ; then remove it with blotting paper, and cover the
gemmules with a drop of turpentine or benzole. After allowing
a few moments for the gemmules to become penetrated with the oil,
remove excess of it with blotting paper, and add a drop of balsam and
a cover glass, and the preparation will be properly and permanently
made.

Place bits of the sponge containing skeletal spicules, and several
gemmules, together in a small test tube, and boil them for several
minutes in a few drops of nitric acid : the spicules will alone remain
undissolved. Fill up the test tube with water, heat gently, and set
aside. The spicules will settle to the bottom. After they have set-
tled, hold the test tube slightly inclined, and roll it slowly between the
fingers to collect the spicules to one spot on the bottom. Holding one
end of a small glass tube closed with the finger, push the open end
down inside the test tube to this spot, and then lift the finger at the
top sufficiently to admit a drop of water at the bottom. This drop
will carry into the tube a load of spicules, which may be transferred
to the center of a clean slip. After the water has evaporated, and left

THE PREPARATION OF MATERIAL. 281

the spicules deposited upon the slip, heat the slip gently to make
sure of the drying, cover the spicules with a drop of balsam, add the
cover glass, and the preparation is complete.

V. On "Germinating" the Gemmules. — "To obtain the young
spongillae, it is only necessary to get a portion of an old living speci-
men bearing statoblasts (gemmules), and, having taken out a few of
the latter, to roll them gently between the folds of a towel, to free
them from all extra material as much as possible. Place them in a
watch glass, so as not to touch each other, with a little water, in a
saucer or small dish filled with small shot to keep the saucer upright,
and, covering them with a glass shade, transfer the whole to a window
bench opposite to the light. In a few days the young spongilla may
be observed (from its white color) issuing from the statoblast (gern-
mule), and gluing the latter as well as itself to the watch glass, when
it is ready for transfer to the field of the microscope for examination,
care being taken that it is never uncovered by water, which may be
replenished as often as necessary." — H. J. CARTER, ESQ., of Devon-
shire, England, in Annals and Magazine of Natural History for 1882,
p. 365.

" If a few of them (gemmules) are removed from a fresh sponge,
placed in an open stage tank (or watch glass) covered with water
(preferably rain water), and protected from dust and too rapid evapo-
ration by a cover of common glass, and placed upon a window ledge
but not in direct sunlight, the following phenomena may be confi-
dently expected.

" We are supposed to be working with gemmules heavier than water,
beneath which they are allowed to rest quietly. If in a few days or
hours some of the gemmules are found fixed where they lie, it is
probable that germination has begun. On removing the preparation
to the stage of the microscope, the instrument being fixed in vertical
position, the initial stages of the development of a sponge can be
daily or hourly watched under low powers of magnification.

" A creamy white granular film first appears, and gradually surrounds
the gemmule, then widens, spreading irregularly in various direc-
tions, reminding one of the appearance of a giant amoeba. At first
nearly uniform in texture and density, it will soon be seen that the
interior portion is more compact than the superficies, a very delicate
film being set off around and over it, puffed up at one subcentral
point into a greatly elongated rounded cone, open at the extremity.
Here at this early stage is a complete sponge. The water with its
contained nutriment is already being drawn in through almost in-
visible pores, and, after feeding the young cells, is thrown out at the

282 APPENDIX.

summit of the cone, technically the 'chimney,' just described. This
motion in the transparent fluid would be quite unperceived but for an
occasional larger particle, which may be seen to come wandering
along beneath the covering film until, reaching the ' chimney,' it is
suddenly puffed out as from a volcano. If the young sponge is very
carefully fed with finely powdered carmine, or other suitable (in-
soluble) coloring matter, the course of circulation may more readily
be followed." — EDWARD POTTS, in The Microscope, vol. x. p. 163.

VI. On Hydra Culture. — The hydra lives in shallow ponds and per-
manent pools in still water. In warm weather it is often found near
the surface, attached to the stems of reeds, or pendent from the lo\ver
surface of floating leaves. In winter it will more often be found
attached to leaves, that have fallen on the bottom. Its narrow, cylin-
drical body is about half an inch long, its tentacles are of equal length,
and its color is pale brown, or, in another species, clear green. The
leaves, etc., should be drawn out of the water, and their surfaces
examined with a lens. The hydras, if present, will be much con-
tracted after being disturbed ; but the tentacles do not entirely dis-
appear when contracted, but remain as a circle of fleshy knobs about
the free end of the hydra, and these will serve for recognition. If
the leaves be placed in a jar of water, the hydras will extend them-
selves again in a few minutes.

Perhaps the surest way to find them is to place the leaves, etc., in a
shallow white dish or plate in water for a few minutes. If present,
they will extend themselves when quiet, and may easily be seen upon
a white background. Though not abundant anywhere, there is hardly
a locality that will not furnish a good supply after a proper search.
They are very apt to be found year after year in the same places.

Hydras for class use should be collected a week or more before they
are to be used. They may be kept in a jar of water, or aquarium, in
which some small aquatic plants are placed. They will need to be
supplied with food. They eat readily small crustaceans not larger
than cyclops, daphnia, etc. ; also protozoans and microscopic plants.
If the jar in which they are to be kept be taken to the field and filled
with the water in which they are found, and a few of the plants to
which they adhere, sufficient food to keep them for a long time will prob-
ably be taken up with the water and the plants. None of the larger
animals (e.g., snails) which feed on hydras should be left in the jar.

Many of the hydras will attach themselves to the sides of the jar,
on the side toward the light. When wanted for study, they may be
dislodged by pushing a knife blade between their bases and the glass,
and taken up with a dropping tube.

THE PREPARATION OF MATERIAL. 283

VII. On Mounting Insects.1 — A few simple directions will be suffi-
cient guide to the preparation of the few life-history boxes men-
tioned in this book. The steps in the process are (1) the fixing of
the specimens on pins ; (2) the thorough drying of them ; and (3)
the mounting of them, under glass, in a box of some sort, tightly
sealed to keep out pests.

Most specimens may be fixed on pins run vertically through the thorax
two thirds of their length. Beetles (with wings closed) should have
the pins run through the center of the left wing cover, and obliquely
downward through the body. Minute specimens may be fixed with
mucilage on a narrow strip of white paper, through which the pin
may be stuck. Pins of uniform length (preferably insect pins) should
be used, and the mounted specimens should stand at the same height
on all the pins. When the wings of an insect are to be spread and
dried so, a setting board is necessary. The pin is run through the
insect in the usual way. The body is placed in a groove in the set-
ting board, and the wings are spread horizontally upon the board, and
held in position by strips of paper pinned across their tips.

The best boxes for preserving insect specimens are lined on the
bottom with sheet cork, into which the pins can easily be pushed.
Thin disks, 'of uniform size, cut from common bottle corks, and
glued to the bottom of the box, will generally answer the student's
purpose. A bit of gum camphor should be placed in the box, and
the top and all cracks tightly sealed, if the preparation is to be per-
manent.

VIII. On Dissecting under Water. — Small animals not covered with
hair or feathers are best dissected under water. Delicate parts are
floated into view, and more easily separated and more easily recog-
nized under water.

Excellent dissecting pans are made by pouring melted wax or
paraffin e into a shallow vessel to harden on the bottom and form a
thin layer, to which the specimens may be pinned down. A piece of
thin board wedged fast in the bottom of a pan with vertical sides
will answer every purpose.

The structure of small parts may often be better made out by " teas-
ing"; i.e., by tearing apart with needles on a slip in a drop of water,
or, better, of dilute glycerine.

1 Part F of Bulletin No. 39, United States National Museum, entitled
Directions for Collecting and Preserving Insects, contains full and explicit
directions, as well as a fund of suggestions, as to methods of rearing insects,
references to entomological literature, etc. It may be had for the asking, and
a copy should be in every school library.

284 APPENDIX.

IX. On Injections. — Blood vessels and other tubular organs and
ducts are much more easily studied if first filled with some colored
substance which renders them more conspicuous. The following
Starch Injection Mass is recommended for filling such vessels : —

Tarta.

Dry (laundry) starch 40

Water or (better, if to be kept) 2i% solution chloral hydrate . 40

95% alcohol 10

Color mixture 10

These should be thoroughly mixed and the mixture strained
through cheese-cloth.

It is easily prepared, easily used, and, on the whole, gives very satis-
factory results. A syringe of some sort may be necessary for forcing the
mass into the vessels to be injected. A cannula should be attached by a
short bit of rubber tubing to the end of the syringe. The cannula is
for insertion into the end of the vessel to be injected. It may readily
be made of a piece of glass tubing drawn to a point, with a constriction
made near the point to hold a ligature from slipping off when tied
around it. It is well to have several cannulae with nozzles of different
sizes. A rubber bulb on a cannula made from a glass tube will answer
ordinarily for any animal not larger than a cat.

The formula for the color mixture mentioned in the above is as
follows : —

Dry color (vermilion, red lead, Berlin blue, ultramarine blue, Parts.

chrome yellow, orange, or green) 3

Glycerine 3

95% alcohol 3

These should first be thoroughly mixed by grinding together in a
mortar.

This starch mass will keep indefinitely in a well-stoppered bottle,
and only needs to be shaken to be ready for use. In using it, the
syringe is first filled with it. The cannula is attached to the syringe,
filled by pushing on the piston slightly, inserted into the end of the
vessel to be injected, and ligatured fast by a soft cotton string tied
around the outside of the vessel. The vessel is then filled by a steady,
gentle pressure upon the piston of the syringe.

A verv convenient instrument for passing the ligature around the
vessel to be tied, may be made by pushing the point of a darning
needle into a wooden handle, heating the eye end of the needle red-hot
and bending it into a shallow hook. The needle can be threaded with

THE PREPARATION OF MATERIAL. 285

the ligature, which may then be easily passed around the vessel in
proper position for tying.

X. How to inject the Catfish. — Anaesthetize the fish by placing it
in a small quantity of water to which a little chloroform or ether has
been added. As soon as it is quiet, cut off the dorsal spine. Place the
fish on its back, and open the body cavity by a median ventral slit.
Continue the cut forward through the bones of the pectoral arch,
taking care not to injure the internal organs. Separate the cut edges
by pressing down on both pectoral spines at once, thus disclosing the
heart lying in its pericardial sac.

In a specimen intended for complete dissection, it will be conven-
ient to inject only that part of the circulatory system which carries
venous blood. Before the blood vessels can be filled with the injection
mass, they must be emptied of their contents. To get the blood out,
make a slit with fine scissors in the ventricle, another in the venous
sinus, another in each of the veins entering the liver from behind, and
another in the vein entering each kidney from behind. Sop up all the
blood that can be induced to flow from these incisions, with a soft
sponge moistened with water, or, better, with normal salt solution,
Then inject. Fill the syringe with the injection mass well shaken.
Insert its cannula into the arterial bulb through the slit in the ven-
tricle, ligature the nozzle of the cannula, and inject forward to fill the
branchial aorta and its branches. Withdraw the cannula, and tighten
the ligature to prevent the escape of the injection. Insert the cannula
in turn in each of the other incisions, ligature, and inject backward.
A very small cannula may be needed for injecting the veins which
return the blood to the kidneys. If the operation be properly per-
formed, the arteries (except the branchial) may be recognized in dis-
secting by their not being injected.

XI. How to inject the Frog or the Turtle. — Anaesthetize the frog
with chloroform or ether. Open the abdominal cavity by a median
ventral incision. Continue the cut forward through the shoulder girdle
a little to one side of the median line. Fasten the edges of the cut
apart, and disclose the heart. With sharp scissors snip off the. point
of the ventricle, and remove the blood with a moist sponge.

The arterial system of the frog is very easily injected. Insert the
cannula through the ventricle into the base of the arterial trunk, liga-
ture, and inject forward. Nothing more will be necessary for filling
the arterial half of the circulatory system, and this will answer our
present purpose.

After opening the body of the turtle as directed in the text (p. 200),
the method of procedure is practically the same as for the frog.

286 APPENDIX.

XII. How to inject a Sparrow. — After anaesthetizing the sparrow
with chloroform, the heart stops very quickly, and rapid work will be
necessary to find it still beating when the body cavity is opened. It
should be beating when the tip of the ventricles is cut off, in order
that as much blood as possible may be removed preparatory to a good
injection of the arterial system. The topography of the skeleton
should be first studied as a guide to removal of the ventral wall of the
thorax.

As soon as the sparrow is quiet, make a transverse cut through the
abdominal wall behind the sternum, and a longitudinal cut along each
side of the thorax through the sternal ribs and coracoid. Raise the
sternum, open the pericardium, and snip off the apex of the ventricles
with sharp scissors. Sop up and remove the blood with a moist sponge.
Insert a small cannula through the right ventricle into the base of
the pulmonary artery, ligature, and inject. Insert a larger cannula
through the left ventricle into the base of the aorta, ligature around
the ventricle, and inject.

XIII. How to inject the Rabbit. — Both arteries and veins should be
injected in the rabbit, but with different colors. Red for arteries, and
blue for veins, are most commonly used.

The more quickly the blood vessels are opened after administering
chloroform, the better in general will be the results. As soon as the
animal is quiet, plunge one blade of a pair of stout, sharp-pointed
scissors through the abdominal wall in the wide ventral notch between
the ribs. Push the blade forward for two inches, keeping the point of
it close under the ribs, and then bring the blades together, making a
median ventral cut through the sternum. Draw apart the edges of the
cut, slit open the pericardium, and snip off the apex of the ventricles,
and make a slit in each of the auricles. Continue the ventral cut
posteriorly for two inches along the abdomen. Turn the liver for-
ward, and slit open the portal vein where it enters the posterior border
of the liver.

Cut away the posterior part of the ventral wall of the thorax,
and by liberal use of a moistened sponge assist the escape of the
blood.

1. The Arteries. Inject the pulmonary arteries by passing a small
cannula through the right ventricle into their base. Inject the remain-
ing arteries through a larger cannula passed through the left ventricle
into the base of the aorta.

2. The Veins. Using another color, inject the pulmonary veins by
a small cannula passed through the left auricle into their base. In-
ject the three cavse with a larger cannula passed through the right

THE PREPARATION OF MATERIAL. 287

auricle into their bases. Inject the portal vein and its branches
through a small cannula posteriorly directed into the slit previously
made to let out the blood.

XIV. On Preparing Skeletons. — The cleaning of bones is not
attractive work, but it is made comparatively an easy matter by the
process described below (taken from Wilder and Gage's "Anatomical
Technology"), and the intrinsic value for study of the disarticulated
skeletons thus secured makes it well worth while. There is much
that can be learned, too, as easily in the preparation of a skeleton
as in any other way, of the relations of the bones to each other and
to the muscles and tendons.

The " liquid soap " used in this process is made by mixing and
liquefying : —

Rain water 2000 cubic centimeters.

Strong ammonia ..... 150 cubic centimeters.

Saltpeter 12 grams.

White soap (hard) 75 grams.

The process consists in (1) removing the skin, viscera, and the
greater part of the muscles from the skeleton ; (2) boiling the skele-
ton for forty minutes in a mixture of liquid soap one part, and water
four parts; (3) boiling the skeleton again for thirty minutes in a
mixture of equal parts of liquid soap and water; and (4) cooling the
skeleton by immersing in cold water, and cleaning, rinsing, and dry-
ing the bones. The time of boiling here given is about the time
required in the preparation of a rabbit skeleton. Less time will be
required to complete the boiling of smaller skeletons.

XV. On Cheap Apparatus. — In addition to the pieces of simple appa-
ratus mentioned in the text, the following are given as having proved
serviceable : —

Dissecting needles may be made by pushing with pliers the eye end
of common sewing needles into wooden handles.

A simple forceps, which the author has often preferred to use in the
handling of minute objects, is made by trimming a narrow strip of
sheet brass or tin to a point at each end, and bending the points to-
gether and parallel.

Bristles of the ordinary sort, obtainable from a harness maker, may
be tipped with paraffine or sealing wax.

Ordinary earthenware jars of several gallons' capacity serve well as
receptacles for organic refuse in the laboratory.

A serviceable net for collecting fresh-water sponges by scraping sub-
merged timbers is made by attaching a circular wire frame to the back

288

APPENDIX.

of a common garden hoe, and suspending a bag from it, so as to collect
the material loosened by the blade of the hoe.

The accompanying cut sufficiently
_j?3^§^v\ explains a small collecting forceps which

Ois useful for picking live bees, wasps,
cggggr\ and the like, from flowers. The frame
~^S§sS£a is Of wire. The blades are covered
A COLLECTING FORCEPS. witn netting.

The water net figured herewith is

made of a loop of heavy wire, a wooden handle, a strip of muslin, a
shallow bag of grasscloth or scrim
or other netting, and some small
wire for binding and bracing. The
loop of wire is formed as shown in
the figure : the crossed ends of the
wire are bent at right angles to the
plane of the loop, and are placed in
grooves in the sides of one end of
the handle, and are wrapped there
securely with smaller wire. Two
grooves are filed in the wire of the
loop at different points for the secure
attachment of the braces, as shown
in the figure. The narrow band of
muslin is sewed to the loop, and the
netting bag to the muslin, and the WATER NET : a, handle ; 6, loop

net is complete. It is quickly used, of wire 5 c> completed net, side

... , , , i i view; N, completed net, from

and easily cleaned by a backward above; ^ brace; e> muslin

push through the water. band ; /, netting bottom.

ACCENTUATED LIST OF THE TECHNICAL TERMS USED
IN THIS BOOK, TOGETHER WITH THEIR ETYMOL-
OGY AND SYNONYMY.

ab-do'-men (Lat. abdomen), belly.

ab-o'-ral (Lat. ab, from, and os, oris, mouth).

ac-e-tab'-u-lum (Lat. acetabulum, vinegar vessel?).

ad-am-bu-la'-cral (Lat. ad, to, and ambulacrum}, next to the ambulacra.

ad-duc'-tor (Lat. ad, to or toward, and ducere, to draw).

ad'-i-pose (Lat. adeps, adiposus, fat), fatty.

a-er-a'-tion (Lat. aer, air), exposure to air; oxygenation.

LIST OF TECHNICAL TERMS. 289

ag'-gre-gate (Lat. ad, to or together, and gregare, to collect into a flock),
al-i-men'-ta-ry (Lat. alimentarius, from alere, to nourish),
al'-u-let (Lat. alula, dim. of a/a, a wing).
am-bu-la'-crum, pi. ambulacra (Lat. ambulacrum, an alley),
a-moe'-ba, pi. amcebas (Gr. amoibe, a change), the proteus animalcule,
a-mce'-boid (Gr. amoibe, change, and eidos, form), like the amoeba,
am-pul'-la, pi. ampullce (Lat. ampulla, a flask).

a-nab'-o-lisrn (Gr. anabole, something heaped up), constructive metab-
olism; assimilation.

an-aes'-the-tize (Gr. an, privative, and aisthesis, feeling or sensation),
a'-nal (Lat. anus, the posterior opening of the alimentary canal),
a-nal'-o-gous (Gr. analogos, according to due ratio),
an'-chy-lose (Gr. angkuloun, to stiffen), fuse ; coossify.
an-i-mal'-cule (Lat. animal, and dim. ule), an infusorian ; a microscopic

animal.

an-ten'-na, pi. antennae, (Lat. antenna, a sail yard), the feeler of an insect,
an-ten'-nule, dim. of antenna.

an-te-or'-bit-al (Lat. ante, before, and orbis, a circle), in front of the orbit,
an-te'-ri-or (Lat. anterior, cornp. of ante, before), fore ; front,
a'-nus (Lat. anus), vent.
a-or'-ta, pi. aortce (Gr. aorte).
a'-pex (Lat. apex}, tip or point.

a-quif'-er-ous (Lat. aqua, water, and/erre, to carry), conducting water.
A-rach'-ni-da (Gr. arachne, a spider), spiders,
ar'-te-ry (Lat. arteria).
Ar-throp'-o-da (Gr. arthron, joint, and pous, podos, foot), joint-footed

animals.

a-ryt'-e-noid (Gr. arutaina, a ladle, and eidos, form),
as-sim'-i-late (Lat. ad, to, and simllare, to make like), to convert into

a like substance.
as-sim'-i-la-tion (Lat. assimilatio, from ad, to, and similare, to make

like), anabolism; constructive metabolism,
at'-las (Gr. Atlas, the god who bears up the pillars of heaven), first

vertebra of the neck, sustaining the skull, whence the name,
at'-ro-phy (Gr. an, privative, and trephein, to nourish), a wasting-away.
au'-di-to-ry (Lat. auditorius, from audire, to hear), pertaining to the

sense or organs of hearing,
au'-ri-cle (Lat. aura, ear, and dim. suffix).
A'-ves (Lat. sing. avist a bird), birds,
ax'-i-al (Lat. axis).
ax'-il-lar (Lat. axilla, armpit),
bar'-bel (Fr. barbel, dim. of Lat. barbus, a beard)t

19

290 APPENDIX.

bar'-bule (Lat. barbula, dim. of barbus, a beard).

ba-si-sphe'-noid (compounded of basal and sphenoid, q.v.).

Ba-tra'-chi-a (Gr. batrachos, a frog), amphibia.

bi'-fid (Lat. bis, twice, and Jindere, fidi, to split), cleft or parted.

bi-fur'-ca-ted (Lat. bis, twice, and Eng. furcate, forked).

bi-lat'-er-al (Lat. bis, twice, and latus, side), pertaining to two sides.

Bi-pin-na'-ri-a (Lat. bis, twice, and pinna, feather).

bi-ro'-tu-late (Lat. bis, twice, and rotula, a little wheel).

bi'-valve (Lat. bis, twice, and valva, valve).

blas'-tu-la (Gr. blastos, a sprout).

brach'-i-al (Lat. brachium, arm), pertaining to the fore limb.

Brach-i-o-la'-ri-a (Lat. dim. of brachium, arm, and -arid), larva of a

starfish.

bran'-chi-al (Lat. branchia, a gill), pertaining to the branchiae or gills.
bran-chi-os'-te-gal (Gr. brangchion, gill, and stegein, to cover),
bron'-chus, pi. bronchi (Gr. brongchos, windpipe),
buc'-cal (Lat. bucca, cheek), pertaining to the mouth,
cae'-cum, pi. cceca (Lat. ccecus, blind),
cal'-a-mus (Lat. calamus, a reed).

cal-ca'-re-ous (Lat. calx, lime), containing carbonate of lime,
cap'-il-la-ry (Lat. capillus, a hair),
car'-a-pace (Fr. carapace}, carapax ; shell ; shield,
car'-di-nal (Lat. cardo, a hinge), pertaining to the hinge in the shell

of Unio.

ca-rot'-id (Gr. karos, heavy sleep),
car'-po-met-a-car'-pus (compounded of Gr. karpos, wrist, and meta-

karpion, beyond the wrist), the single large bone of the bird's hand,

formed by the coossification of carpal and metacarpal bones,
car'-pus (Gr. karpos, wrist),
car'-ti-lage (Lat. cartilago).

cau'-dal (Lat. cauda, tail), pertaining to the tail,
cen'-trum, pi. centra (Lat. centrum), the body of a vertebra,
ce-phal'-ic (Gr. kephale, head), pertaining to the head or brain,
ceph-a-lo-tho'-rax (Gr. kephale, head, and thorax, the chest).
cer-e-bel'-lum (Lat. dim. of cerebrum, the brain),
cer'-e-brum (Lat. cerebrum), the hemispheres of the forebrain.
cer'-vi-cal (Lat. cervix, neck).

chi-as'-ma (Gr. chiasma, two lines placed crosswise), optic commissure,
chi'-tin (Gr. chiton, a corselet) .

chlor'-a-gogue (Gr. chloros, light green, and agein, to lead),
chrys'-a-lid, pi. chrysalids > (Gr> cAnj^ gold)>
chrys'-a-lis, pi. chrysalides )

LIST OF TECHNICAL TERMS. 291

cil'-i-a (Lat. sing, cilium, an eyelash).

cir-cum-o'-ral (Lat. circum, around, and os, om, mouth).

cir-cum-val'-late (Lat. circumvallare, to surround with a wall).

clav'-i-cle (Lat. clavicula, a little key), the collar bone.

cli-tel'-lum (Lat. clitellce, a pack saddle).

clo-a'-ca (Lat. cloaca, a sewer).

co-a-lesce' (Lat. con, with, and alescere, to grow up), unite; fuse' join.

Cce-len-te-ra'-ta (Gr. koilos, hollow, and enteron, intestine).

coe'-li-ac (Gr. koilia, belly), pertaining to the abdomen.

Co-le-op'-te-ra (Gr. koleon, a sheath, and pteron, a wing).

col-u-mer-la (Lat. dim. of columen, a column) .

com'-mis-sure (Lat. cominisura, a joining together).

con-cen'-tric (Lat. con, together with, and centrum, center), having a
common center.

con'-dyle (Lat. condylus, from Gr. kondos, a head or knob).

con-ju-ga'-tion (Lat. con, together, and jungere, to join).

con-tour' (Fr. contour, outline).

con-tract'-ile (Lat. con, together, and trahere, to draw).

cor'-a-coid (Gr. korax, a crow, and eidos, form : from a fancied resem-
blance of the human coracoid process to a crow's beak).

cor'-ne-a (Lat. corneus, horny).

cor'-pus-cle (Lat. dim. of corpus, body).

cos'-ta (Lat. costa, a rib).

cov'-erts (Lat. con, with, and operire, to cover).

cox'-a, pi. coxce (Lat. coxa, the hip).

cra'-ni-um (Gr. kranion, skull), the brain case.

cre-mas'-ter (Gr. kremaster, a suspender) .

crib'-ri-form (Lat. cribrum, a sieve, and forma, form).

cri'-coid (Gr. krikos, a ring, and eidos, form).

cris'-sum (Lat. crisso, to move the haunches), the under tail coverts of
a bird ; feathers around the cloaca.

crys'-tal-line (Lat. crystallum; Gr. krustallos, ice, crystal).

cu'-bi-tus (Lat. cubitus, elbow).

cul'-men (Lat. culmen, from celsus, lofty).

der'-mis (Gr. derma, skin), cutis.

dex'-tral (Gr. dexiteros, pertaining to the right hand) .

di'-a-phragm (Gr. dia, through, and phrassein, to fence or inclose).

dif-fer-en-ti-a'-tion (Lat. dis, apart, audferre, to carry).

di-gest' (Lat. digerere, to separate, to dissolve).

dig'-it (Lat. digitus, a finger) .

dig'-i-tate (Lat. digitus, a finger), having an arrangement like that of
the fingers on the hand.

292 APPENDIX.

di-ce'-cious (Gr. dis, twice, and oikos, house), having the two sexual
elements produced by two separate individuals of the same species.

Dip'-te-ra (Gr. dis, two, and pteron, a wing).

dis-ar-tic'-u-late (Lat. dis, apart, and articulus, dim. of artus, a joint),
to sunder; to separate at the joint.

dis-coid'-al (Gr. diskos, a round plate, and eidos, form), disk-shaped.

dis'-tal (Lat. distare, to stand apart), remote from the point of attach-
ment.

di-ver-tic'-u-lum, pi. diverticula (Lat. diverticulum), a blind tube extend-
ing outward from a large tube.

dor'-sal (Lat. dorsum, back), tergal ; opposed to ventral.

du-o-de'-num (Lat. duodeni, of twelve each : the human duodenum is
in length about equal to the breadth of twelve fingers, hence the
name), anterior part of small intestine.

E-chi-no-der'-ma-ta (Gr. echinos, sea urchin, and derma, skin).

ec'-to-derm (Gr. ektos, outside, and derma, skin).

ec'-to-sarc (Gr. ektos, outside, and sarx, flesh).

e-gest' (Lat. e, out, and gerere, to carry), to void.

el'-y-tron, el'-y-trum, pi. elytra (Gr. elutron, a sheath).

em'-bry-o (Lat. embryo, Gr. embruon).

em-bry-ol'-o-gy (Gr. embruon, embryo, and logos, a discourse), the
study of the development of embryos.

en'-do-derm (Gr. entos, within, and derma, skin).

en'-do-sarc (Gr. entos, within, and sarx, flesh) .

en-do-skel'-e-ton (Gr. endon, within, and skeleton, a dry body).

en-dos-mo'-sis (Gr. endon, within, and osmos, a thrusting).

en-to-mol'-o-gy (Gr. entomon, an insect, and logos, a discourse).

ep-i-der'-mis (Gr. epi, upon, and derma, skin), cuticle.

ep-i-glot'-tis (Gr. epi, upon, and glotta, a tongue).

e-piph'-y-sis, pi. epiphyses (Gr. epi, upon, phuein, to grow).

e-soph'-a-gus (Gr. oisophagos), gullet.

eth'-moid (Gr. ethmos, a sieve, and eidos, form).

Eu-sta'-chi-an, discovered by Eustachius, an Italian physician.

ev-o-lu'-tion (Lat. evolvere, to roll out of, to unfold).

ex-cre'-tion (Lat. excernere, to sift out, to discharge).

ex-o-skel'-e-ton (Gr. exo, outside, and skeleton, a dry body), outside
skeleton.

ex-sert'-ed (Lat. exserere, to stretch forth), projecting beyond some
other part.

ex-ten'-si-ble (Lat. ex, out, and tendere, to stretch), capable of being
extended.

ex-u'-vi-*, pi. exuviae (Lat. exuere, to draw out, to pull off).

LIST OF TECHNICAL TERMS. 293

fac'-et (Fr. dim. of face).

fau'-na (Lat. Fauni, rural deities), the animals of any place or period

taken collectively.
fem'-o-ral (Lat./ewwr, thigh),
fe'-mur, pi. femora (Lat. femur), thigh.

fer-ti-li-za'-tion (L&t.ferre, to bear), fecundation; impregnation,
fib'-u-la, pi. fibulce (Lat. fibula, that which binds together; named

from the human splint-like fibula),
fil'-a-ment (L&t.filum, a thread),
fil'-i-form (L&t.jilum, a thread, and/orwa, form),
fi'-lo-plume (L&i.filum, a thread, andpZwma, a soft feather),
floc'-cu-lar (Lat. flocculus, dim. oifloccus, a lock of wool),
fo-li-a'-ta (Lat. from, folium, a leaf),
fo-ra'-men, pi. foram'ina (Lat. foramen, a perforation).
fos'-sa, pl.fossce (Lat. fossa, a pit, from fodere, to dig),
fron'-tal (Lat. frontale, an ornament for the forehead),
fur'-cu-lum (Lat. furculum, dim. offurca, a fork), wishbone,
ga'-le-a, pi. galece (Lat. galea, a helmet).

gan'-gli-on, pi. ganglia (Lat. ganglion, Gr. ganglion, a swelling),
gas'-tric (Gr. gaster, stomach).

gas-troc-ne'-mi-us (Gr. gastroknemia, calf of the leg),
gas-tros'-tege (Gr. gaster, stomach, and siege, roof),
gem'-mule (Lat. dim. of gemma, a gem).
gle'-noid (Gr. glene, a cavity, and eidos, form),
glo-chid'-i-um (Gr. glochis, the point of an arrow),
glot'-tis (Gr. from glotta, gldssa, a tongue),
go'-nys (Gr. gonia, an angle),
hal-te'-res (Gr. halter es, dumb-bells), balancers,
ham'-u-li, pi. (Lat. dim. of hamus, a hook),
he'-mal (Gr. haima, blood)

He-mip'-te-ra (Gr. Jiemi, half> and pteron, a wing), bugs,
hem'-i-sphere (Gr. hemi, half, and sphaira, a sphere),
hem'-o-lymph (Gr. haima, blood, and lymph).
he-pat'-ic (Lat. hepar, the liver),
her-maph'-ro-dite (Gr. Hermaphroditos, son of Hermes and Aphrodite

[myth]), being of both sexes.

Hex-ap'-o-da (Gr. hex, six, and pous, podos, foot), six-footed insects,
ho-mol'-o-gous (Gr. homologos, agreeing).
ho-mol'-o-gy (Gr. homologia, agreement), correspondence, in structure

and origin.

hu'-me-rus (Lat. humerus*).
hy'-dra, Eng. pi. hydras (Lat. hydra, water).

294 APPENDIX.

Hy-me-nop'-te-ra (Gr. Tinmen, membrane, and pteron, a wing), the mem-
brane-winged insects.

hy'-oid (Gr., the letter v, and eidos, form).

hy-pa-poph'-y-sis (Gr. hupo, under, and apophusis, a process of a bone).

hy'-po-stome (Gr. hupo, under, and stoma, mouth).

il'-i-o-sci-at'-ic (compounded of ilium and sciatic, q.v.).

il'-i-um (Lat. ilia, groin, flank, small intestine).

i-ma'-go (Lat. imago, an image), the perfect insect ; adult.

in-ci'-sor (Lat. in, in, and ccedere, to cut), a gnawing tooth.

in-fra-or'-bit-al (Lat. infra, beneath, and orbis, a circle).

in-fun-dib'-u-lum (Lat. infundibulum, a funnel).

in-gest' (Lat. in, in, and gerere, to bear or carry).

in-glu'-vi-€s (Lat. ingluvies), crop.

in-nom'-i-nate (Lat. in, not, and nominatus, named).

in'-sect (Lat. insectus, from insecare, to cut in).

in'-te-grate (Lat. integrare, to make whole).

in-ter-cos'-tal (Lat. inter, between, and costa, a rib).

in-ter-neu'-ral (Lat. inter, between, and Gr. neuron, a nerve), between
the neurals.

in-ter-or'-bit-al (Lat. inter, between, and orbis, a circle), between the
orbits.

in-ter-pa-ri'-e-tal (Lat. inter, between, and parietal, q.v.).

in-tes'-tine (Lat. intestinus, from intus, the inside).

i'-ris (Lat. iris, the rainbow).

is'-chi-um, pi. ischia (Gr. ischion, the hip joint).

isth'-mus (Lat. isthmus, a narrow neck of land).

i'-ter (Lat. iter), a passage.

ju'-gal (Lat. jugum, a yoke).

ju'-gu-lar (Lat. jugulum, the throat).

ka-tab'-o-lism (Gr. kata, down, and ballein, to throw), destructive
metabolism.

la'-bi-al, pertaining to the lips.

la'-bi-um > (Lat laU u }

la'-brum )

lach'-ry-mal (Lat. lachryma, a tear).

la-cin'-i-a (Lat. lacinia, a lappet or flap).

lac'-te-al (Lat. lac, lac t is, milk).

lar'-va (Lat. larva, ghost, specter).

lar'-ynx (Gr. larungx, the larynx).

lat'-er-al (Lat. latus, side), pertaining to the side.

Lep-i-dop'-te-ra (Gr. lepis, a scale, and pteron, a wing), scaly-winged
insects.

LIST OF TECHNICAL TERMS. 295

lig'-a-ment (Lat. ligare, to bind).

lig'-u-la (dim. of Lat. lingua, a tongue).

lob'-u-late (Gr. lobos, a rounded projection).

lore (Lat. lorurn, a strap), space between beak and eye in birds.

lum'-bar (Lat. lumbus, loin).

mad'-re-po-rite (Lat. mater, mother, and Gr. poros, a soft stone).

mag'-num (Lat. magnus), great.

ma'-lar (Lat. mala, the cheek).

Mal-pi'-ghi-an, discovered by Malpighi.

mam'-mal (Lat. mamma, a breast).

Mam-ma'-li-a, the animals which nourish their young with milk.

mam'-ma-ry (Lat. mamma, a breast, a glandular organ for secreting

milk), pertaining to the mammary glands,
man'-di-ble (Lat. mandere, to chew),
man' -tie (Lat. mantellum, a cloth or cloak),
ma-nu'-bri-um (Lat. from manus, hand),
ma'-trix, pi. matrices (Lat. matrix, mother),
max-il'-la, pi. maxillce (dim. of Lat. mala, a jaw),
max'-il-la-ry (Lat. maxilla, a little jaw),
max-il'-li-ped (Lat. maxilla, jaw, and pes, pedis, foot),
me-a'-tus (Lat. meare, to go), a passage.
me'-di-an (Lat. medius, middle),
me-di-as-ti'-num (Lat. mediastinus = medius).
me-dul'-la (Lat. medulla, marrow), the hindbrain : written also

medulla oblongata.

mes'-en-ter-y (Gr. mesos, middle, and enteron, intestine).
mes-o-ster'-num (Gr. mesos, middle, and sternon, breast),
mes-o-tho'-rax (Gr. mesos, middle, arid thorax, chest).
me-tab'-o-lism (Gr. metabole, change), the constructive and destruc-
tive changes which take place within the cell, a process known

only through its results.

met-a-car'-pus (Gr. meta, beyond, and Jcarpos, wrist).
met-a-mor'-pho-sis, pi. metamorphoses (Gr. meta, beyond, over, and

morphe, form, shape), the structural changes which take place

in an animal after it emerges from the egg.
met-a-no'-tum (Gr. meta, beyond, hind, and notos, back),
met-a-ster'-num (Gr. meta, beyond, and sternon, breast),
me-tas'-to-ma (Gr. meta, behind, and stoma, mouth),
met-a-tar'-sus (Gr. meta, beyond, and tarsos, tarsus),
met-a-tho'-rax (Gr. meta, beyond, and thorax, chest).
met-a-zo'-an (Gr. meta, beyond, and zoon, animal), one of the "higher"

animals ; any animal, not a protozoan ; a many-celled animal.

296 APPENDIX.

mo'-lar (Lat. molere, to grind), a grinding tooth.

Mol-lus'-ca (Lat. mollis, soft), mollusks.

mo'-tile (Lat. movere), having power of motion.

mu'-cous (Lat. mucus, mucus).

Myr-i-ap'-o-da (Gr. murios, numberless, and pous, podos, foot).

na'-sal (Lat. nasus, the nose), pertaining to the nose.

ne-phrid'-i-a (Gr. nephros, kidney).

neu'-ral (Gr. neuron, a nerve), pertaining to the nervous system or some
part of it.

nic'-ti-tat-ing (Lat. nictare, to wink).

no'-dus (Lat. nodus, a knot).

no'-tum (Gr. notos, back).

nu'-chal (Lat. nucha, the nape).

nu'-cle-us (Lat. dim. of nux, nucis, a nut).

nymph (Lat. Nympha [myth.] , goddess of meadows, waters, forests, etc.).

ob'-tu-ra-tor (Lat. obturare, to stop up).

oc'-ci-put (Lat. ob, against or back of, and caput, head).

o-cel'-lus, pi. ocelli (Lat. dim. of oculus, eye).

oc-u-lo-mo'-tor (Lat. oculus, the eye, and movere, to move).

O-don'-a-ta (Gr. odous, odontos, a tooth).

o-don'-toid (Gr. odous, a tooth, and eidos, form).

o-lec'-ra-non (Gr. olene, elbow, and kranion, head).

ol-fac'-to-ry (Lat. olere, to smell, and facere, to make), pertaining to
the sense of smell.

o-mo-s'ter'-num (Gr. omos, shoulder, and sternon, breast).

o'-b'-sperm (Gr. don, egg, and sperma, seed), the fertilized ovum.

o-per'-cu-lum (Lat. from operire, to cover).

op'-tic (Gr. optikos, belonging to sight), pertaining to the eye.

o'-ral (Lat. os, oris, mouth), pertaining to the mouth.

or'-bit (Lat. orbis, a circle).

or'-i-fice (Lat. os, mouth, and facere, to make).

Or-thop'-te-ra (Gr. orthos, straight, and pteron, a wing), the straight-
winged insects.

os cru'-ris (Lat. os, bone, and cruris, leg).

os-mo'-sis (Gr. osmos, impulse).

os'-si-fy (Lat. os, ossis, a bone), to become bone.

os'-si-cle (Lat. dim. of os, a bone), a little bone.

os'-te-ole (Lat. dim. of ostium, mouth).

os-te-ol'-o-gy (Gr. osteon, bone, and logos, discourse).

o'-va-ry (Lat. ovarium, from ovum, egg).

o'-vate (Lat. ovum, egg), egg-shaped.

o'-vi-duct (Lat. ovum, egg, and ductus, duct, tube).

LIST OF TECHNICAL TERMS. 297

o-vi-pos'-i-tor (Lat. ovum, egg, audponere, to place).

o'-vum (Lat. ovum), egg.

pal'-ate (Lat. palatum), the roof of the mouth.

pal'-a-tine (Lat. palatum, the roof of the mouth), the bones supporting

the palate.

pal'-li-al (Lat. pallium, a mantle),
pal'-pus, pi. palpi (Lat. palpus), feeler.

pan'-cre-as (Gr. pangkreas, pancreas, from pas, all, and kreas, flesh),
pa-pil'-la, pi. papillce (Lat. papilla), a pimple-like projection,
par-a-me'-ci-um (Gr. para, beside, and mekos, strength).
par-a-sphe'-noid (Gr. para, beside, and sphenoid, q.v.).
pa-ri'-e-tal (Lat. paries, a wall),
pa-rot'-id (Gr. para, beside, and ous, otos, the ear),
pa-tel'-la (Lat. dim. of patena, a pan), the kneepan.
pec'-ti-na-ted (Lat. pecten, a comb), toothed, like a comb,
pec'-to-ral (Lat. pectus, breast), pertaining to the breast.
ped'-i-cel (Lat. pediculus, dim. of pes, pedis, foot),
ped-i-cel-la'-ri-a, pi. pedicellarice (Lat. pedicellus, pedicel, and -aria).
pel'-vis (Lat. pelvis, a basin).

per-i-car'-di-um (Gr. peri, around, and kardia, the heart),
per'-i-stome (Gr. peri, around, and stoma, mouth),
per-i-to-ne'-um (Gr. peri, around, and teinein, to stretch),
pha-lan'-ges, pi. of phalanx (Gr. phalangx, phalanx),
phar'-ynx (Gr. pharungx).
pi'-ne-al (Lat. pinea, the cone of a pine).
Pis'-ces (Lat. pi. of piscis, a fish), fishes,
pi-tu'-i-ta-ry (Lat. pituita, phlegm, mucus). This body was once

erroneously supposed to secrete the mucus of the nostrils,
plas'-ma (Gr. plasma).
plas'-tron (Fr. plastron, a breastplate).
pleu'-rum, pi. pleura (Gr. pleura, the side),
plex'-us (Lat. plexus), a twining or twisting; a network,
por'-tal (Lat. porta, a gate), the gateway of the liver, the portal vein,
post'-ca-va, pi. postcavce (Lat. post, after, and cavus, hollow), posterior

vena cava or ascending vena cava.
pos-te'-ri-or (Lat. comp. of posterns, coming after), hinder ; opposed to

anterior.

post-or'-bit-al (Lat. post, after or behind, and orbis, a circle),
prae'-ca-va, pi. prcecavce (Lat. prce, before, and cavus, hollow), anterior

vena cava or descending vena cava.
pre-cor'-a-coid (Lat. pro?, before, and coracoid, q.v.).
pre-max'-il-la-rv ( Lat. vrce, before, and maxilla, jaw).

298 APPENDIX.

pre-o-per'-cu-lum (Lat. prce, before, and operculum, a covering).

pre-sphe'-noid (Lat. prce, before, and sphenoid, q.v.).

pri'-ma-ries (Lat. primus, the first).

pro-bos'-cis, pi. probos'cides (Gr. pro, before, and boskein, to feed).

pro-neph'-ros (Gr. pro, before, and nephros, kidney).

pro-no'-tum (Gr. pro, before, and notos, back).

pro-6'-tic (Gr. pro, before, and ous, otos, ear).

pro-ster'-num (Gr. pro, before, and sternon, breast).

pro-sto'-mi-um (Gr. pro, before, and stoma, mouth).

pro-tho'-rax (Gr. pro, before, and thorax, thorax).

pro'-to-plasm (Gr. protos, first, and plasma, form).

Pro-to-zo'-a (Gr. protos, first, and zoon, animal).

pro-tract'-or (Lat. pro, forward, and trahere, to draw).

pro-ven-tric'-u-lus (Lat. pro, forward, and ventriculus, stomach).

prox'-i-mal (Lat. proximus, nearest), nearest the point of attachment,
or nearest the median point or plane.

pseu-do-po'-di-a (Gr.pseudes, false, and pous, podos, foot), false feet.

pter-o-stig'-ma (Gr. pteron, a wing, and stigma, a spot).

pter'-y-goid (Gr. pterux, a wing, and eidos, form).

pu'-bis, pi. pubes (Lat. pubis).

pul-mo-cu-ta'-ne-ous (Lat. pulmo, a lung, and Eng. cutaneous, pertaining
to the skin).

pul'-mo-na-ry (Lat. pulmo, lung), pertaining to the lungs.

pul-vil'-lus, pi. pulvilli (Lat. pulvillus), a little cushion.

pu'-pa, pi. pupce (Lat. pupa, a doll, a puppet).

pu'-pil (Lat. pupilla, originally dim. of pupa, a girl), the circular open-
ing through the iris.

py'-gal (Gr. puge, the rump).

py'-go-style (Gr. puge, rump, and stulos, a pillar or stylet for writing).

py-lo'-rus (Lat. pylorus, a gatekeeper).

quad'-rate (Lat. quadratum, quadrangular).

ra'-di-us, pi. radii (Lat. radius, a staff or rod).

rad'-u-la, pi. radulce (Lat. radula, a scraper, from radere, to scrape) .

ra'-mus, pi. rami (Lat. ramus, a branch).

rec'-tri-ces (pi. of Lat. rectrix, a governess), tail feathers.

re'-nal (Lat. renes, the kidneys), pertaining to the kidneys.

Rep-til'-i-a (Lat. reptilis, from, repere, to creep), reptiles.

re-tract'-or (Lat. re, back, and trahere, to draw).

re-trorse' (Lat. retro, back, and vertere, to turn).

rha'-chis (Gr. rachis, a dorsal ridge or spine), shaft.

ric'-tus (Lat. ringi, rictus, to open wide the mouth), the gape.

ros'-trum (Lat. rostrum, a beak).

LIST OF TECHNICAL TERMS. 299

sac'-cu-la-ted (^Lat. sacculus, dim. of saccus, a sack), bearing little sacs.
sa'-crum, the Latin name for the anchylosed human sacral vertebrae,
sal'-i-va-ry (Lat. saliva, spittle), pertaining to the saliva,
sar'-code (Gr. sarx, flesh, and eidos, form).

scap'-u-la, pi. scapulce (Lat. scapula}, shoulder blade.

sci-at'-ic (Lat. sciaticus), pertaining to the hip.

scle-rot'-ic (Gr. skleros, hard).

scu-tel'-la, pi. scutellce (Lat. fem. dim. of scutum, a shield).

scu'-tel-late (Lat. scutella, a dish or plate), covered with scutella, over-
lapping plate-like scales.

sec'-ond-a-ries, pi. of secondary (Lat. secundarius, second).

seg-men-ta' -tion (Lat. segmentum, segment, from secare, to cut).

seg'-ment (Lat. segmentum, from secare, to cut off), somite ; ring ; joint.

sep'-tum, pi. septa (Lat. septum, a fence or partition), a partition.

ser'-ra-ted (Lat. serra, a saw), toothed, like a saw.

ses'-a-moid (Gr. sesamon, a kind of seed, and eidos, form), seedlike (?)
bones formed in the tendons.

ses'-sile (Lat. sessum, seated, from sedere, to sit).

se'-ta, pi. setce (Lat. seta), a bristle.

sin'-is-tral (Lat. sinister, the left hand), pertaining to the left-hand
side ; turning toward the left.

si'-nus, Eng. pi. sinuses (Lat. sinus), a curve ; a hollow.

si'-phon (Lat. sipho, Gr. siphon, a bent tube for the transference of
water).

skel'-e-ton (Gr. skeleton, a dried body).

sperm (Lat. sperma, seed), spermatozoa ; the male reproductive element.

sper'-ma-ry (Lat. sperma, seed), testicle.

sper-mat'-ic (Lat. spermaticus, pertaining to spermatic fluid).

sphe'-noid (Gr. sphen, a wedge, and eidos, form).

spic'-ule (Lat. dim. of spica, a dart).

spir'-a-cle (Lat. spirare, to breathe).

spleen (Gr. splen}.

spu'-ri-ous (Lat. spurius), false; whence the spurious quills constitute
what is sometimes called the " false wing."

squa-mo'-sal (Lat. squama, a scale).

ster'-num (Lat. from Gr. sternon, breast).

stri'-a-ted (Lat. stria, a channel), marked with fine grooves or lines.

strid-u-la'-tion (Lat. stridulare, to creak).

sty'-let (Lat. stylus, a style [writing instrument]).

sub-cla'-vi-an (Lat. sub, under, and clavicle, a little key), beneath the
clavicle.

sub-cos' -tal (Lat. sub, under, and costa, a rib).

300 APPENDIX.

sub-gen'-i-tal (Lat. sub, under, and genitalis, the genital organs),
sub-lin'-gual (Lat. sub, under, and lingua, a tongue),
sub-max'-il-la-ry (Lat. sub, under, and maxilla, a jaw),
sub-me'-di-an (Lat. sub, under, and medius, the middle),
sub-quad'-rate (Lat. sub, under, and quadratum, quadrangular), some.

what four-angled.

suc-to'-ri-al (Lat. sugere, suctum, to suck), adapted for sucking,
su'-ture (Lat. sutura, a seam),
swim'-mer-et, abdominal swimming appendage,
sym'-phy-sis (Gr. sumphuein, to grow together), coalescence; fusion-,

coossification.

syr'-inx (Gr. suringx, a pipe),
tac'-tile (Lat. tangere, tactum, to touch),
tar'-so-met-a-tar'-sus (compounded of tarsus and metatarsus; the name

for the single bone formed by the fusion of these),
tar'-sus, pi. tarsi (Gr. tarsos, the flat of the foot),
teg'-mi-na (Lat. pi. of legmen, from tegere, tectum, to cover),
tel'-son (Gr. telson, a limit), the terminal joint of the abdomen of

Crustacea.

ten'-don (Lat. lendere, to stretch),
te-nac'-u-lum (Lat. tenere, to hold),
ten'-ta-cle (Lat. tentare, to feel).
ter'-gum, pi. terga (Lat. tergu?n), back,
ter'-mi-nal (Lat. terminare, to put an end to), on the end.
ter'-ti-a-ries, pi. of tertiary (Lat. tertius, the third),
tes'-tis, pi. testes (Lat. testis), spermary.
tho-rac'-ic, pertaining to the thorax,
tho'-rax (Gr. thorax, the chest),
thy'-mus (Gr. thumos).

thy'-roid (Gr. thureos, a shield, and eidos, form),
tib'-i-a, pi. tibiae (Lat. tibia, the shin bone, also a pipe or flute which

was originally made of bone).
tra'-che-a, pi. tracheae, (Lat. trachea}, the windpipe ; also air tubes of

insects.

trans-verse' (Lat. trans, across, and vertere, to turn), across the long axis.
tri-gem'-i-nal (Lat. tri, three, and geminus, a twin),
tri-un'-gu-lin (Lat. tri, three, and unguis, a claw),
tro-chan'-ter (Gr. trochanter, a runner),
trun'-ca-ted (Lat. truncare, to cut short), appearing as if cut off squarely

at the tip.
tu'-ber-cle (Lat. tuber, from tumere, to swell, and dim. cle, little), a

small knob-like prominence.

LIST OF TECHNICAL TERMS. 301

tur'-bi-nal (Lat. turbo, a top).

tym'-pa-num, pi. tympani (Lat. tympanum, a drum head).

typ'-i-cal (Lat. typicus), expressing the essential characteristics of a

type.

ul'-na (Lat. ulna, the elbow),
um-bi-li'-cus (Lat. umbilicus, the navel), an opening into the calamus

of a feather.

um'-bo, pi. umbo'nes (Lat. umbo), a boss or short beak,
un'-ci-nate (Lat. uncus, a hook).

u-ni-cel'-lu-lar (Lat. unus, one, and cella, a cell), one-celled,
u'-ni-valve (Lat. unus, one, and valva, fold),
u-re'-ter (Gr. ouron, urine).

u'-ri-na-ry (Lat. urina, urine), pertaining to the urine,
u'-ro-stege (Gr. oura, tail, and stege, roof).
u'-ro-style (Gr. oura, tail, arid stulos, pillar, style [for writing]), a

styliform process at the posterior extremity of the vertebral

column.

u'-te-rus (Lat. uterus), the womb,
vac'-u-ole (Lat. vacuus, empty).

va'-gus (Lat. vagus, wandering, called also the pneumo-gastric nerve),
vane (O. Eng.fane, a weathercock).

vas'-cu-lar (Lat. vasculum, dim. of vas, a vessel), containing vessels.
vein (Lat. vena) : veinule and veinlet are its diminutives,
ven'-tral (Lat. venter, the belly).
ven'-tri-cle (Lat. ventriculus, dim. of venter).
ver'-mi-form (Lat. vermis, a worm, and forma, form), shaped like a

worm.

ver'-te-bra, pi. vertebra (Lat. vertere, to turn),
ves'-i-cle (Lat. vesicula, dim. of vesica, a bladder), a cyst,
ves'-ti-bule (Lat. vestibulum, a place of entrance),
vis'-ce-ra (Lat. pi. of viscus), the entrails ; internal organs,
vo'-mer (Lat. vomer).

xiph-i-ster'-num (Gr. xiphos, a sword, and sternum, q.v.).
xiph'-oid (Gr. xiphos, a sword, and eidos, form),
zyg-a-poph'-y-sis, pi. zygapophyses (Gr. zungon, a yoke, and apophysis,

process of a bone), one of the articular processes of a vertebra.

302 APPENDIX.

SUGGESTIONS TO THE TEACHER.

Some knowledge of the difficulties encountered by one who \vould
attempt a well-balanced elementary courso in zoology, in some of our
secondary schools at the present time, prompts this final word to the
teacher.

I would recommend the teacher, first of all, to note the amount of
work outlined in the foregoing pages, and to consider whether it may
all be done in the time at the disposal of his class. Having often
found that a particular animal, when wanted alive for study, is not to
be had, I have mentioned several types to which each outline may be
applied, and have perhaps added more outlines in brief than so ele-
mentary a course requires ; yet I trust the advantage of this will be
apparent when selections are to be made. For a short course it might
be more profitable to study only the part relating to insects or the part
relating to vertebrates, rather than to attempt to " go through " the
book.

I would suggest that the teacher arrange his work so as to have
an hour of freedom from teaching preceding the hour for zoology,
which may be spent in preparing for the recitation. The hour will be
anything but vacant if devoted to the preparation for the hour to
follow it.

I would suggest that the teacher spend the first hour of the session
in familiarizing his pupils with the microscope, — with its parts and
their use. I would give them each a slide with some object of simple
outlines mounted on it, and instruct them in moving the object into
the field, in finding it with low and with high powers, and I would
require an outline drawing of it.

Then I would proceed at once to the study of amoeba, paramecium,
sponge, and hydra, passing over this part as rapidly as proved consis-
tent with the mastering of the fundamental ideas of zoology which
these types are well adapted to introduce. For this part of the study,
I would provide all the material, and present it as demonstrations,
requiring of the pupils only that they study it and make drawings
showing all they are able to make out, naming the parts and explain-
ing their action ; and that they make note of the habits and habitat
of these animals.

Then I would begin, as early as possible in the term (all the mate-
rial of this book is arranged with reference to beginning the course
in early autumn), the study of insects. And for the remainder of the

SUGGESTIONS TO THE TEACHER. 303

course I would require that all the work outlined in the text be done
by the student, and that the greater part of it be done by each student
for every animal studied. Just how much dissecting and how much
field work, etc., should be required, will have to be determined in
accordance with the abilities and needs of individual classes. Some
of the larger dissections may be made as demonstrations by the
teacher or assistants ; but I consider it absolutely necessary that each
student should study the structure of every type, and record his
observations in some permanent form, notes, drawings, or preparations
of illustrative material. While freely acknowledging the great value
of original drawings, however crude, I think it should be borne in
mind that the student who has no aptitude for this art may find
continual drawing as irksome as it is unsatisfactory to him. I have
found students, wholly incapable of making a presentable drawing,
able to make beautiful preparations of material for demonstrations
and for collections. The true ends of scientific instruction will not
be promoted by keeping any student long at work which he cannot
make pleasant or satisfactory.

The field work suggested in this book forms an important feature
of it, yet not so important, I am persuaded, as it should be made.
I would require of the students, that, in so far as is possible, they
collect all their own material for study. The observations made
while doing this will not be among the least valuable things learned
about animals in the course. And I would not discourage the collection
of cabinet specimens. This has its place. There is one benefit to be
had from a thorough study of types, and there is another benefit to
be had from personal contact with nature in a great variety of forms.
I would go out with the students often, and direct their observations
in the field. Making use of the haunts of animals most accessible
for study, I would assign simple tasks of outdoor observation, requir-
ing little time, and I would not limit these to observations on the
types studied in the course. Many a teacher neglects abundant oppor-
tunity for doing this. Material for such study is at the very doors of
a majority of the schools in which elementary zoology is taught. Our
higher institutions of learning, located often in the heart of great
cities, by establishing seaside and lakeside laboratories, get, at a great
expenditure of time and money, that which the secondary schools
may have if they choose, without expense, as a part of their daily life.
And who shall say that the study of animals in their relation to nature
is of more worth in one school or in the other ?

I urge as most important, that the teacher maintain strictest super-
vision of all work, that there may be no idling in the field, no smat-

304 APPENDIX.

tering in the laboratory, and as little as may be of memorized
second-hand information in the classroom. Definite results should
be required of every excursion made by students to the field. Quiet,
careful, and diligent work should be insisted on in the laboratory.
Scrupulous neatness should be maintained. Every student should be
required to keep his table clean and his specimens fresh, and to
entirely remove from the laboratory all materials in his charge that
are liable to become offensive.

Lastly I would urge the teacher to acquaint himself with the entire
fauna of his own locality. Doubtless in many localities other types
than those mentioned in this book are better and more available for
study: such he is recommended to find and use by his friend and
fellow-worker,

THE AUTHOR.

INDEX.

Abdomen, of asellus, 125.

of back-swimmer, 62.

of beetle, 76.

of bumblebee, 65.

of butterfly, 42.

of cicada, 60.

of crawfish, 114.

of cyclops, 127.

of dragon fly, 45.

of fly, 83.

of grasshopper, 51.

of mussel, 145.

of pupa, 92.

of rabbit, 243.

of sparrow, 216, 221.

of spider, 108.

Acridium. See Schistocera.
Air sac of snail, 156.
Alimentary canal. See Digestive

organs.

Amoeba, 12, 278.
Amoeboid blood, 137.
Analogy, 45.
Anasa, 57.
Antenna, of crustacean, 118, 125, 127.

of insect, 39.

Antennule, 118, 125, 127.
Aorta. See Arteries.
Aperture. See Sponge gemmules.
Arachnida, 105-109.
Arm bones, of frog, 192.

of rabbit, 257.

of turtle, 206.
Arteries, of crawfish, 119.

of fish, 163, 168.

of frog, 182, 184.

of mussel, 146.

of rabbit, 247.

of sparrow, 226.

of turtle, 202.
Arthropoda, 128.
Asellus, 125.
Asilus, 85.

Asterias, 266, 267.
Aves, 211.

Backbone. See Spinal column.

Back-swimmer, 61.

Barbels, 162.

Batrachia, 178, 198.

Beak, 215.

Bee killer, 85.

Beetle, 74.

blister, 74.

Harpalus, 78.

larvse, 79.

locust borer, 78.

red milkweed, 78,

soldier, 77.

whirligig, 79.
Birds, 211, 236.
Blastula, 159.
Blood, of fish, 163.

of insects, 52, 94.

of worm, 137.

Blood vessel. See Circulatory or-
gans.

Bluebottle fly, 80.
Body cavity j of starfish, 272.

of worm, 136.
Bone. See Skeleton.
Books of reference, 275.
Brachystola, 52.
Brain. See Nervous system.
Branch, 128.
Branchial chamber, of crawfish, 113

of fish, 170.

of mussel, 144.
Budding, 27.
Bumblebee, 63.
Butterfly, 36.

cabbage, 86, 89, 92.

clover, 36.

egg, 88, 90.

larva, 88, 90.

milkweed, 104.

NEED. ZOOL. 20

305

306

INDEX.

Butterfly, pupa, 89, 92.
skipper, 103.
sulphur, 36.
swallow-tail, 102.

Cambarus, 111.
Cantharidin, 75.
Carapace, of crawfish, 144.

of cyclops, 126.

of turtle, 199.
Carolina locust, 48.
Catfish, 161.
Cell, 18.
Centiped, 109.
Cephalothorax, of crawfish, 114.

of cyclops, 127.

of spider, 108.
Chauliognathus, 77.
Chilopod, 109.
Chrysemys, 198.
Cicada, 59.

Chloragogue cells, 137.
Circulation, demonstration of, 125,

163, 179.

Circulatory organs, of crustaceans,
119.

of fish, 168.

of frog, 182.

of insects, 52.

of mussel, 146.

of rabbit, 246.

of sparrow, 225.

of starfish, 271.

of turtle, 201, 202.

of worm, 134.
Class, 128.

Classification, 101, 127.
Clitellum, 133.
Ccelenterata, 22-33.
Coleoptera, 74, 79.
Colias. See Eurymus.
Collar of snail, 156.
Collecting insects, 34.
Colony, 69.
Columella, 188. See also Shell of

snail.
Comb, 73.

Condyle. See Skull.
Conjugation, 17.
Cranium. See Skull.
Crawfish, 111.
Cremaster, 89.
Crustaceans, 111-128.
Cyanide bottle, 35.
Cyclops, 126.

Development, of blister beetle, 76.

of bumblebee, 68.

of cabbage butterfly, 88.

of crawfish, 123.

of dragon fly, 47.

of fly, 83.

of frog, 196.

of grasshopper, 55.

of mussel, 152.

of snail, 157.

of spider, 109.

of sponge gemniules, 24.

of turtle, 207.

of wasp, 71, 73.

of worm, 138.
Diaphragm, 244.
Differentiation, 25.
Digestive organs, of crawfish, 121.

of fish, 167.

of frog, 181. '

of insect, 53, 94.

of mussel, 147.

of rabbit, 245.

of snake, 210.

of sparrow, 223.

of starfish, 270.

of turtle, 202.

of worm, 134.
Diplax, 42.
Diptera, 80, 86.

Directions for preparation of ma-
terial for study, 278.
Dissosteira, 48.
Division of labor, 32.
Dorsal vessel, 52, 94.
Dragon fly, 42.

Ear sac of mussel, 153.
Earthworm, 130.
Echinodermata, 266-273.
Ectoderm, 28.
Ectosarc, 13, 19.
Egg capsules, of snail, 160.

of worm, 139.
Egg sacs, 127.
Embryology, 158, 160, 196.
Endoderm, 28.
Endosarc, 13, 19.
Endoskeleton, 122, 205.
Epicauta, 74.
Epiglottis, 243.

Esophagus. See Digestive organs.
Eurymus, 36.
Eustachian tube, 180, 242.
Evolution, 264.

INDEX.

307

Excretory organs, of crawfish, 122.

of fish, 169.

of frog, 182.

of grasshopper, 54.

of mussel, 147.

of rabbit, 246.

of sparrow, 225.

of turtle, 202.

of worm, 136.
Exoskeleton, 204, 217.
Eye, of crawfish, 119.

of fish, 172.

of insects, 39.

of snail, 156.

of starfish, 269.

Family, 103.

Feathers, 218.

Feeding, of amoeba, 14, 15.

of bumblebee, 63.

of butterfly, 37.

of crawfish, 112.

of dragon fly, 43.

of earthworm, 130.

of fly, 80.

of frog, 180.

of grasshopper, 49.

of hydra, 26.

of paramecium, 21.

of rabbit, 238.

of sparrow, 213.

of squash bug, 58.

of starfish, 270.
Fertilization, 30.
Fins, 162, 166.
Fish, 161.
Foot, of frog, 192.

of insect, 41.

of mussel, 142.

of rabbit, 240.

of snail, 155.

of sparrow, 214.

of spider, 108.

Foramen magnum. See Skull.
Fresh- water sponge, 22.
Frog, 178.

Gastrula. 159.
Gemmules, 23, 280, 281.
Genus, 102.
Gill, of crawfish, 120.

of fish, 170.

of mussel, 144.
Glochidia, 152.
Glottis. See Larynx.

Grasshopper, 48.
Green gland, 122.

Harvest fly, 59.

Haunts and habits, of amoeba, 278

of asellus, 125.

of back-swimmer, 61.

of bee killer, 85.

of beetles, 77-79.

of blister beetle, 74.

of bumblebee, 63.

of butterfly (cabbage), 86.

of butterfly (sulphur), 36.

of catfish, 161.

of centiped, 109.

of cicada, 59.

of crawfish, 111.

of cyclops, 126.

of dragon fly, 42.

of earthworm, 131.

of fly, 80.

of frog, 178.

of grasshopper, 48.

of hydra, 282.

of mussel (river), 140.

of paramecium, 279.

of rabbit, 237.

of snail (pond), 154.

of sparrow, 212.

of spider, 105.

of sponge (fresh- water), 279.

of squash bug, 57.

of starfish, 266.

of turtle, 198.

of wasp (mud) , 70.

of wasp (paper), 72.
Head, of blister beetle, 75.

of bumblebee, 64.

of butterfly, 39.

of dragon fly, 74.

of fish, 162.

of fly, 81.

of grasshopper, 49.

of larva, 90.

of pupa, 92.

of sparrow, 215.

of turtle, 199.

Heart. See Circulatory organs,
Hemiptera, 57, 62.
Hermaphroditism, 30.
Hinge ligament, 141.
Homology, 45, 123.
Honeybee, 73.
Hydra, 26, 282.
Hymenoptera, 63, 74.

308

INDEX.

Hyoid bone, 185, 222, 243.
Hypostome, 27.

Ictalurus, 161.
Insects, 34-110.
collecting, 34.
Intestine. See Digestive organs.

Kidney. See Excretory organs.

Labial palpi 1

Labru" ' \SeeMouthparts.

Lacinia

Lacteal system, 250.

Larva, 08, 88, 90, 96.

Larynx, 222, 243.

Lasso cells, 28.

Lateral line, 166.

Leg bones, of frog, 193.

of rabbit, 259.

of sparrow, 235.

of turtle, 207.
Legs, of bird, 217.

of crawfish, 116.

of frog, 188.

of insect, 40.

of rabbit, 240.

of turtle, 200.
Lens. See Eye.
Lepidoptera, 36, 42, 86, 93, 102,

104, 128.
Lepus, 237.

Life history. See Development.
Life process, in amoeba, 15.

in hydra, 30.

in insects, 93.

in mussel, 150.

in sponge, 25.

in starfish, 272.

in vertebrates, 260.
Limnea, 154.
Lizard, 208.
Locomotion, in amceba, 14.

in crustaceans, 113, 126.

in earthworm, 132.

in fish, 162.

in hydra, 26.

in insects, 97.

in mussel, 142.

in paramecium, 19.

in snail, 156.

in sparrow, 214.

in starfish, 267.
Locust, 48. See also Cicada.

Lucilia, 80.

Lumbricus, 130.

Lung. See Respiratory organs.

Malpighian tube. See Digestive

organs of insect.
Mammalia, 237-259.
Mantle, 142, 143, 155.
Maxilla. See Mouth parts.
Maxilliped, 117.

Mesentery, 167, 181, 224, 244, 245.
Metabolism, 151, 261.
Metamorphosis, 69, 96.
Metastoma, 118.
Mollusca, 140-160.
Mouth, of fish, 165.

of frog, 179, 180.

of hydra, 28.

of mussel, 147.

of rabbit, 241.

of snail, 156.

of snake, 209.

of starfish, 268.

of turtle, 200.

of worm, 139.
Mouth parts of insects, 39, 44, 49,

65, 82, 91, 108.
Mud dauber, 70.
Mud wasp, 70.
Mucous membrane, 250.
Muscles, of crawfish, 121.

of fish, 174.

of frog, 189.

of insects, 97.

of mussel, 144.

of sparrow, 225.

of starfish, 270, 271.

of turtle, 203.

of worm, 136.
Mussel, 140.
Myenia, 22.
Myriapoda, 109, 110.

Neck, of sparrow, 215, 221.

of turtle, 200.
Nephridium of worm, 136.
Nerve collar, of crawfish, 122.

of insects, 55.

of worm, 136.
Nervous system, of crawfish, 122.

of fish, 170-173.

of frog, 185.

of insect, 55, 98.

of mussel, 147.

of rabbit, 250.

INDEX.

309

Nervous system, of sparrow, 235.

of starfish, 271.

of turtle, 185.

of worm, 136.
Nest, of bumblebee, 67.

of paper wasp, 72.
Nucleus, 15, 18, 20.
Nutrition, in amoeba, 16.

in hydra, 30.

in insects, 93.

in mussel, 150.

in vertebrates, 260.
Nymph, 46, 96.

Odonata, 42-48.
Order, 104.
Organ, 32.
Orthoptera, 48-57.
Ovum, 29.

Palate. See Mouth.

Pallial line, 149.

Pancreas. See Digestive organs.

Paper wasp, 72.

Paramecium, 18.

Passer, 211.

Pectoral arch. See Shoulder girdle.

Pelvic girdle, of fish, 166.

of frog, 193.

of rabbit, 258.

of sparrow, 234.

of turtle, 207.

Pericardium. See Circulatory or-
gans.

Peristome, 20.
Pharynx, 165, 242.
Piscus, 161, 178.
Plastron, 204.
Plumage, 218.

Proboscis. See Mouth parts.
Pronephros, 169.
Protozoa, 12, 21.
Pseudemys, 198.

Rabbit, 237.

Radius. See Arm bones.

Radula, 157.

Rana, 178.

Reagents, 276.

Reproduction, in amoeba, 17.

in hydra, 31.

in insects, 96.

in starfish, 273.

in vertebrates, 262.

vegetative, 27.

Reproductive organs, of crawfish,
121.

of fish, 167.

of frog, 182.

of grasshopper, 53.

of hydra, 27, 29.

of mussel, 148.

of starfish, 269.

of turtle, 202.

of worm, 135.
Reptilia, 198-211.
Respiration, in amoeba, 16.

in cyclops, 127.
Respiratory organs, of crawfish, 116.

of fish, 170.

of grasshopper, 53.

of insects, 94.

of mussel, 151.

of rabbit, 249.

of snail, 156.

of snake, 210.

of sparrow, 222, 224.

of spider, 108.

of turtle, 203.
Rib, 176, 205, 231, 254.
Robber fly, 85.
Rostrum, of bugs, 58.

of crawfish, 114.

Scapula. See Shoulder girdle.

Schistocera, 52.

Segmental organ. See Nephridium

of worm.

Segmentation, of arthropods, 39,
113, 133, 134.

of oosperm, 158, 196.
Sensation, in amoeba, 18.

in hydra, 32.

in insect, 98.

in mussel, 153.

in vertebrates, 263.
Serial homology, 123.
Setae, 132.
Shell, of mussel, 148.

of snail, 155.

of turtle, 203.
Shoulder girdle, of fish, 166.

of frog, 192.

of rabbit, 257.

of sparrow, 233.

of turtle, 206.
Siphon, 144.
Skeleton, of crawfish, 114, 122.

of fish, 175.

of frog, 191.

310

INDEX.

Skeleton, of insect, 38.

of rabbit, 253.

of sparrow, 227.

of turtle, 203.
Skin, of fish, 161.

of frog, 190.

of insect, 38, 92.

of rabbit, 239.

of sparrow, 217.

of turtle, 204.

of worm, 136.
Skull, of fish, 171.

of frog, 194.

of rabbit, 255.

of sparrow, 227.
Snail, 154.
Snake, 208.
Sparrow, 211.
Specialization, 21, 33.
Species, 102.
Sperms, 29, 137.
Spicules, 23, 280.
Spider, 105.
Spinal column, of fish, 169.

of frog, 191.

of rabbit, 253.

of sparrow, 230.

of turtle, 205.

Spinal cord. See Nervous system.
Spiracle of insect, 42, 51.
Spleen, 168, 182, 224, 24(5.
Sponge, 22.

gemmules, 23, 280, 281
Squash bug, 57.
Starfish, 266.
Sternum, of frog, 192.

of rabbit, 254.

of sparrow, 232.

Stomach. See Digestive organs.
Stylets, 125.
Swimmer, 115.
Syrinx, 222.

Tarsus. See Foot.
Teasing, 283.
Teeth. See Mouth.
Telson, 114.

Test of strength of beetle, 79.
Tetraopes, 78.
Thoracic duct, 250.
Thorax, of insects, 40.

of rabbit, 243.
Thousand-legs, 110.
Thymus, 250.
Tissue, 32.

Tongue. See Mouth.
Trachea. See Respiratory organs
Tracheal gills, 47, 94.
Tracheal tube, 53, 94.
Turtle, 198.

Ulna. See Arm bones.
Umbo, 141.
Unio, 140.

Uterus, 262.

Vacuole (vesicle?), 15, 20
Vegetative reproduction, 27.
Veins, of fish, 163, 168.

of frog, 183.

of mussel, 146.

of rabbit, 246.

of sparrow, 226.

of turtle, 202.

Vermiform appendage, 246.
Vertebra. See Spinal column.
Voluntary motion, in amoeba, 17.

in hydra, 31.

in insect, 97.

in mussel, 152.

in vertebrates, 262.

Water- vascular system, 270.
Wing, 213, 216.
Wing bones, 233.
Worm, 130.

36075

M577041

QL42
N4

Educ
Lib.