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CO
IP-
THE
AMERICAN SCIENCE SERIES
FOR SCHOOLS AND COLLEGES.
The principal objects of the series are to supply the lack — in some subjects
very great — of authoritative books whose principles are, so far as practicable,
illustrated by familiar American facts, and also to supply the other lack that
the advance of Science perennially creates, of text-books which at least do not
contradict the latest generalizations. The books of this series systematically
outline the field of Science, as the term is usually employed with reference to
general education. The scheme includes an Advanced Course, a Briefer Course,
and an Elementary Course.
In ordering be careful to state which course is desired — Advanced,
Zoology.
By A. S. PACKARD, Professor
of Zoology and Geology in Brown
University.
Advanced Course, 722 pp.
Briefer Course, 338 pp.
Elementary Course, 290 pp.
The Human Body.
By H. NEWELL MAKTIN, Professor
in the Johns Hopkins University.
Advanced Course, 631 — 34 pp.
Copies without the Appendix on
Reproduction will be sent when
specially ordered.
Uriefer Course, 377 pp.
Elementary Course, 261 pp.
Psychology.
By WM. JAMES, Professor of Psy-
chology in Harvard University.
Advanced Course, in 2 vols. Vol. I,
<>S<» pp. ; Vol. II, 704 pp.
Briefer Course, 478 pp.
Political Economy.
By FRANCIS A. WALKER, Presi-
dent Massachusetts Institute of
Technology.
Advanced Course, 537 pp.
Briefer Course, 415 pp.
Elementary Course, 323 pp.
Briefer, or Elementary.
Physics.
By GEORGE F. BARKER, Professor
in the University of Pennsylvania.
Advanced Course, 902 pp.
Chemistry.
By IRA REMSEN, Professor in the
Johns Hopkins University.
Advanced Course, 850pp.
Briefer Course, 387 pp.
Memmtary Course, 273 pp.
Astronomy.
By SIMON NEWCOMB, Professor in
the Johns Hopkins University, and
EDWARD S. HOLDEN, Director of the
Lick Observatory.
Advanced Course, 512 pp.
Briefer Course, 352 pp.
Biology.
By WILLIAM T. SEDGWICK, Pro-
fessor in the Massachusetts Insti-
tute of Technology, and EDMUND
B. WILSON, Professor in Bryn Mawr
College.
Part I. — Introductory, 193 pp.
Botany.
By C. E. BESSEY, Professor in the
University of Nebraska ; formerly
In the Iowa Agricultural College.
Advanced Course, 611 pp.
Briefer Course, 292 pp.
HENRY HOLT & CO., PUBLISHERS, NEW YORK.
AMERICAN SCIENCE SERIES— ADVANCED COURSE
ZOOLOGY
FOR
HIGH SCHOOLS AND COLLEGES
BY
A. S. PACKARD, M.D., PH.D.
MEMBER OF THE NATIONAL ACADEMY OF SCIENCES; PROFESSOR OF ZOOLOGY
AND GEOLOGY IN BROWN UNIVERSITY
EIGHTH EDITION, REVISED
NEW YORK
HENRY HOLT AND COMPANY
1893
Copyright, 1879, 1886, 1892.
by
HENRY HOLT & Co.
PREFACE,
THIS book is designed to be used quite as much in the la-
boratory or with specimens in hand, as in the class-room. If
Zoology is to be studied as a mental discipline, or even if the
student desires simply to get at a genuine knowledge, at first
hand, of the structure of the leading types of animal life,
he must examine living animals, watch their movements and
habits, and finally dissect them, as well as study their mode
of growth before and after leaving the egg or the parent, as
the case may be. But the young student in a few wee~ks'
study in the laboratory cannot learn all the principles of the
science. Hence, he needs a teacher, a guide, or at least a
manual of instruction. This work is an expansion of a
course of lectures for college students, but has been pre-
pared to suit the wants of the general reader who would ob-
tain some idea of the principles of the science as generally
accepted by advanced zoologists, in order that he may under-
stand the philosophical discussions and writings relating to
modern doctrines of biology, especially the law of evolution
and the relations between animals and their surroundings.
The book has been prepared, so far as possible, on the in-
ductive method. The student is presented first with the
facts ; is led to a thorough study of a few typical forms,
taught to compare these with others, and finally led to the
principles or inductions growing out of the facts. He has
not been assailed with a number of definitions or diagnoses
applicable to the entire group to which the type may belong
before he has learned something about the animals typical
iv PREFACE,
of the order or class ; but these are placed after a description
of one or a few examples of the group to which they may
belong. The simplest, most elementary forms are first no-
ticed, beginning with the Protozoa and ending with the Ver-
tebrates. In working up from the simplest forms to those
more complex, it is believed that this is the more logical and
philosophical method, and that in this way the beginner in the
science can better appreciate the gradual unfolding of the lines
of animal forms which converge toward his own species, the
flower and synthesis of organic life. Still the learner is ad-
vised to begin his work by a study of the first part of Chap-
ter VIII. , on Vertebrates, and to master, with a specimen in
hand, the description of the frog, in order that he may have
a standard of comparison, a point of departure, from which
to survey the lower forms.
Particular attention has been given to the development of
animals, as this subject has been usually neglected in such
manuals. Some original matter is introduced into the book -f
a new classification of the Crustacea is proposed, the orders
being grouped into the subclasses Neocarida and Palceocar-
ida. Most of the anatomical descriptions and drawings
have been made expressly for this book, and here the author
wishes to acknowledge the essential aid rendered by Dr. C. S.
Minot, who has prepared the drawings and descriptions of
the fish, frog, snake, turtle, pigeon, and cat.
In compiling the book, the author has freely used the
larger works of Gegenbaur, Huxley, Peters and Carus, Glaus,
Rolleston, and others, whose works are enumerated at the
end of the volume, and in many cases he has paraphrased
or even adopted the author's language verbatim when it has
suited his purpose. Besides these general works many mon-
ographs and articles have been drawn upon.
In order to secure a greater accuracy of statement, and to-
render the work more authoritative as a manual of Zoology,
PREFACE. v
the author has submitted the manuscript of certain chapters
to naturalists distinguished by their special knowledge of
certain groups. The manuscript of the sponges has been
read by Professor A. Hyatt ; of the worms and Mollusca, by
Dr. Charles S. Minot ; of the Echinoderms, by Mr. Walter
Faxon; of the Crustacea, by Mr. J. S. Kingsley. Proofs of the
part relating to the fishes have been revised by Professor T.
Gill, whose classification as given in his "Arrangement of
the Families of Fishes," has been closely followed, his defin-
itions having been adopted often word for word. The man-
uscript of the Batrachians and Reptiles has been read by
Professor E. D. Cope, whose classification, given in his
" Check-List of North American Batrachia and Reptilia,"
has been adopted. Proofs of the part on birds have been
read by Dr. Elliott Coues, U.S.A., whose admirable "Key
to the Birds of North America" has been freelv used, the
*/
author's words having been of ton adopted without quotation-
marks. Dr. Coues has also revised the proofs of the pages re-
ferring to the Mammals. To the friendly aid of all these
gentlemen the author is deeply indebted.
As to the illustrations, which have been liberally provided
by the publishers, a fair proportion are original. The full-
page engravings of the anatomy of the typical Vertebrates
have been drawn expressly for this work by Dr. C. S. Minot ;
a number have been prepared by Mr. J. S. Kingsley ; Prof.
\V. K. Brooks has kindly contributed the drawing of the
nervous system and otocyst of the clam, and a few of the
sketches are by the author.
The publishers are indebted to Prof. F. V. Haydeu
for illustrations kindly loaned from the Reports of the U.S.
Geological Survey of the Territories ; a few have been
loaned by Prof. S. F. Baird, U.S. Commissioner of Fish and
Fisheries, and the members of the U.S. Entomological Com-
mission ; a number have been loaned by the Peabody Acad-
VI PREFACE.
emy of Science, Salem, Mass.; by the publishers of the
American Xuturalist, and by the Boston Society of Natural
History, while forty of the cuts of birds have been electro-
typed from the originals of Coues' Key, and Tenney's Zoology.
Measurements are usually given in the metric system ; in
such cases the approximate equivalent in inches and fractions
of an inch are added in parentheses.
Should this manual aid in the work of education, stimu-
late students to test the statements presented in it by person-
al observations, and thus elicit some degree of the inde-
pendence and self-reliance characteristic of the original in-
vestigator, and also lead them to entertain broad views in
biology, and to sympathize with the more advanced and
more natural ideas now taught by the leading biologists
of our time, the author will feel more than repaid.
BROWN UNIVERSITY,
Providence, R, I., October 25, 1879.
PREFACE TO THE FIFTH EDITION.
MORE radical changes have been made in this than any
former edition. The Tunicata have been transferred to a
position next below the Vertebrates in the group Chordata.
The Merostomata, together with the Trilobites, have been
placed in a class called Podostomata (in allusion to the fact
that the head and mouth appendages are foot-like). Their po-
sition is between the Crustacea and Arachnida. The branch
Arthropoda is divided into six classes, viz.: 1, Crustacea;
2, Podostomata; 3, Malacopoda ; 4, Myriopoda; 5, Arach-
nida; 6, Insecta. The orders of insects have been increased
from eight to sixteen, according to the arrangement on pp.
365, 366. For the order of Mayflies we propose the name
Plectoptera (Gr. plecfos, a fine net, in allusion to the finely
net -veined wings), and for the PanorpidcB, the ordinal
name Mecoptera (Gr. mecos, length, in allusion to the long,
narrow wings). Numerous minor changes and corrections
have also been made.
PROVIDENCE, June, 1886.
CONTENTS.
PAGE
INTRODUCTION 1
Definition of Zoology 1
Morphology 5
Organs and t .eir Functions 8
Correlation of Organs • 9
Adaptation of Organs 10
Analogy and Homology 12
Physiology 12
Psychology 12
Reproduction 13
Embryology 13
Classification 13
Zoogeography 16
CHAPTER I. Branch 1. PROTOZOA 17
II. " 2. PORIFERA (Sponges) 42
III. " 3. CCELENTERATA (Hydroids, Jelly-fishes,
and Polyps) 51
IV. " 4. VERMES (Worms) 96
V. "5. ECHINODEHMATA (CHnoids, Starfish,
Sea Urchins, etc 138
VI. " 6. MOLLUSCA (Bivalves, Snails, Cuttles)... 220
VII. " 7. ARTIIROPODA (Crustaceans and Insects) 265
VIII. " 8. VERTEBRATA 369
IX. COMPARATIVE ANATOMY OF ORGANS 631
Organs of Digestion, the Mouth and Teeth. . . 631
Organs of Circulation 635
Organs of Respiration 637
The Nervous System 638
Organs of Sense 640
viii CONTENTS.
FAQS.
CHAPTER X. DEVELOPMENT G44
Metamorphosis 651
Parthenogenesis and Alternation of Genera-
tions 652
Dimorphism and Polymorphi?m 654
Individuality 656
Hybridity 657
XI. THE GEOGRAPHICAL DISTRIBUTION OP ANIMALS 658
Means of Dispersal 660
Division of the Earth into Faunae 661
Distribution of Marine Animals 664
Chief Zoological Faunae of the Earth 66ft
XII. THE GEOLOGICAL SUCCESSION OP ANIMALS 668
XIII. THE ORIGIN OF SPECIES 671
XIV. PROTECTIVE RESEMBLANCE 675
XV. INSTINCT AND REASON IN ANIMALS 680
XVI. GLOSSARY 689
XVIL INDEX., . 697
ZOOLOGY.
INTRODUCTION.
Definition of Zoology. — That science which treats of liv-
ing beings is called Biology (/3/os, life ; Xdyos, discourse).
It is divided into Botany, which relates to plants, and Zo~
ology (£c5oK, animal ; XoyoS, discourse), the science treating
of animals.
It is difficult to define what an animal is as distinguished
from a plant, when we consider the simplest forms of either
kingdom, for it is impossible to draw hard and fast lines in
nature. In defining the limits between the animal and
vegetable kingdoms, our ordinary conception of what a
plant or an animal is will be of little use in dealing with
the lowest forms of either kingdom. A horse, fish, or
worm differs from an elm tree, a lily, or a fern in having
organs of sight, of hearing, of smell, of locomotion, and
special organs of digestion, circulation, and respiration, but
these plants also take in and absorb food, have a circulation
of sap, respire through their leaves, and some plants are me-
chanically sensitive, while others are endowed with motion
• — certain low plants such as diatoms, etc., having this
power. In plants, the assimilation of food goes on all over
the organism, the transfer of the sap is not confined to any
one portion or set of organs as such. It is always easy to
distinguish one of the higher plants from one of the higher
animals. But when we descend to animals like the sea-ane-
mones and coral-polyps which were called Zoophytes from
their general resemblance to flowers, so striking is the exter-
nal similarity between the two kinds of organisms that the
2 zooLOor.
early observers regarded them as " animal flowers ;" and in
consequence of the confused notions originally held in regard
to them the term Zoophytes has been perpetuated in works
on systematic zoology. Even at the present day the com-
pound Hydroids, such as the ^-rtnlnria, are gathered and
pressed as sea- mosses by many persons who are unobservant
of their peculiarities, and unaware of the complicated anat-
omy of the little animals filling the different leaf-like cells.
Sponges until a very late day were regarded by our leading
zoologists as plants. The most accomplished naturalists,
however, find it impossible to separate by any definite lines
the lowest animals and plants. So-called plants, as Bacte-
rium, and so-called animals, as Prof-amoeba, or certain mo-
nads, which are simple specks of protoplasm, without gen-
uine organs, may be referred to either kingdom ; and, in-
deed, a number of naturalists, notably Haeckel, relegate
to a neutral kingdom (the Protista) certain low-
est plants and animals. Even the germs (zo-
ospores) of monads likeUvella (Fig. 1), and those
of other flagellate infusoria, may be mistaken
for the spores of plants ; indeed, the active fla-
1 _pvel gellated spores of plants were described as in-
ia, a flagellate fusoria by Ehrcnbcrg ; and there are certain so-
infusorian, or * ° '
monad, with called flagellate infusoria so much like low
two large ci- , , , . , .
Ha called plants (such as the red snow, or Profococcus),
Greatly mag- in the form, deportment, mode of reproduc-
tion, and appearance of the spores, that even
now it is possible that certain organisms placed among them
are plants. It is only by a study of the connecting links
between these lowest organisms leading up to what are un-
doubted animals or plants that we are enabled to refer these
beings to their proper kingdom.
As a rule, plants have no special organs of digestion or
circulation, and nothing approaching to a nervous system.
Most plants absorb inorganic food, such as carbonic acid
gas, water, nitrate of ammonia, and some phosphates, silica,
etc. ; all of these substances being taken up in minute quan-
tities. Low fungi live on dead animal matter, and promote
the process of putrefaction and decay, but the food of these
DISTINCTIONS BETWEEN ANIMALS AND PLANTS. 3
organisms is inorganic particles. The slime-moulds called
M//xo>n//cefc$, however, envelop the plant or low animals,
much as an Amceba throws itself around some living plant
and absorbs its protoplasm ; but Myj-iimyccti1*, in their man-
ner of taking food, are an exception to other moulds. The
lowest animals swallow other living animals whole or in
pieces ; certain forms like Amoeba (Fig. 2) bore into minute
algse and absorb their pro-
toplasm ; others engulf sili-
cious-shelled plants (diatoms)
absorbing their protoplasm.
No animal swallows silica,
lime, ammonia, or any of
the phosphates as food. On
nthpr Vii-nrl nlants manu- Fte. 8.— Amoeba, a Protozoan. The right-
ndliu, picuiifc J hand figure shows three pseudopodia on
fnotnrp or iiroduee from in- the r'£nt side: inthe Uvo othe-r fiKUI^st,he
pseudopodia are withdrawn in the body-
organic matter starch,* sugar mass.
and nitrogenous substances which constitute the food of
animals. During assimilation, plants absorb carbonic acid,
and in sunlight exhale oxygen ; during growth and work
they, like animals, consume oxygen and exhale carbonic acid.
Animals move and have special organs of locomotion ;
few plants move, though some climb, and minute forms
have thread-like processes or vibratile lashes (cilia) resem-
bling the flagella of monads, and flowers open and shut, but
these motions of the higher plants are purely mechanical,
and not performed by special organs controlled by nerves.
The mode of reproduction of plants and animals, however,
is fundamentally identical, and in this respect the two king-
doms unite more closely than in any other. Plants also,
like animals, are formed of cells, the latter in the higher
forms combined into tissues.
As the lowest plants and animals are scarcely distinguish-
able, it is probable that plants and animals first appeared
contemporaneously ; and while plants are generally said
to form the basis of animal life, this is only partially true ;
a large number of fungi are dependent on decaying animal
matter; and most of the Protozoa live on animal food, as
* Starch has been found by Bergh in Cilio-ttagellate Infusoria.
4 ZOOLOGY.
do a large proportion of the higher animals. The two
kingdoms supplement each other, are mutually dependent,
and probably appeared simultaneously in the beginning of
things. It should be observed, however, that the animal
kingdom overtops the vegetable kingdom, culminating in
man.
In speaking as we have of low animals and high animals,
we are comparing very unequal quantities; the distance be-
tween monad and man is well-nigh infinite. But there is a
series or chain, sometimes broken and often with lost links,
connecting the extremes ; and as there are wide differences
in form, so there are great extremes in the organs and de-
gree of complication of function of the simple as compared
with the more complex forms. The improvised stomach of
an Amce.ba is not comparable with the stomach of an hydra,
nor is the stomach of the latter creature with that of a
horse ; there is a gradual perfection and elaboration or spe-
cialization of the stomach as we ascend in the animal series.
So it is Avith organs of locomotion ; the pseudopods and cilia
of the Protozoans are replaced in the star-fishes and worms
by hollow tentacles or various fleshy soft appendages ; in
crabs and insects by stiff, jointed limbs, with different lev-
erage systems ; and these are replaced in vertebrates bv
genuine limbs supported by bones. A comparative view of
the origin and structure of organs succeeds in this book the
systematic account of the animals themselves.
We thus see that the organs of the higher animals are
merely modifications of organs often having the same
general functions as in the lower animals ; the lower or
simpler have preceded in geological history the higher or
more specialized forms, and thus we are, in ascending the
animal series, going from the simple to the complex. For
this reason the plan of this work has been to lead the stu-
dent from the simpler forms of animal life to the more
complex ; and though the vertebrate animals, such as fishes
and dogs, are more familiar and interesting to us, the seri-
ous student of zoology will feel that it is more logical and
better in the eiid to study the animal Avorld in the order in
which the different forms have appeared — as we believe,
MORPUOLOO T. 5
through the orderly operations of physical and biological
laws, under the guidance of an Infinite Intelligence — a
Creator whose modes of working are revealed to us in what
vwe call the laws or processes of nature.
Zoology is subdivided thus :
Morphology or gross Anatomy, and minute
Anatomy (Histology).
Physiology and Psychology.
Zoology.
Eeproduction and Embryology.
Systematic Zoology or Classification.
Palaeontology.
Zoogeography.
Morphology. — In order to properly understand Zoology,
one should first study Morphology — i.e., the general struc-
ture of animals. The student should first thoroughly ac-
quaint himself with the anatomy of a vertebrate animal,
.such as a frog, as compared with that of a toad or salaman-
der. The examination and comparison of the organs of
.animals belonging to distinct groups, is called Comparative
Anatomy. The study of Morphology also includes the rela-
-tion of the different organs to one another, and of all to the
walls of the body. Finally, we need also to study the com-
position of the tissues of the different organs ; each kind of
tissue being formed of different kinds of elements or cells.
This department of Comparative Anatomy is called Histol-
ogy (Greek, iffrd;, web or tissue ; Ao;/o?, discourse). It
treats of the cell, and the combination of cells into germ-
layers, tissues, and organs.
The Cell. — The primary elements of the bodies of animals
are called cells. They are microscopic portions of proto-
plasm either with or without a wall. Protoplasm largely
consists of protein, which is a compound of carbon, hydro-
gen, oxygen, nitrogen, and sulphur, associated with a large
proportion of water. Cells are originally more or less
spherical sacs, and the protoplasm forming the cell-mass is
the dynamic part of the cell. The protoplasm of animal as
well as vegetable cells, the protoplasm of eggs and of the
cells forming the different tissues of the animal body, as
6 ZOOLOGY.
Avell as the entire Amoeba or monad, is complex. It consists
of carbon, hydrogen, oxygen, nitrogen, and sulphur, combined
in nearly the same proportions. The protoplasm of different
cells exerts widely different forces and capabilities. An egg-
cell becomes a man, whose brain-cells are the medium of the
intellectual power which enables him to write the history of
his own species, and to be the historian of the forms of life
which stand below him. The cell is the morphological
unit of the organic world. With cells the biologist can
in the imagination reconstruct the vegetable and animal
worlds.
The primitive form of a cell, when without a nucleus or
nucleolus, is called a cytode ; genuine cells have a nucleus,
the latter containing a nucleolus. Animals composed of but a
single cell, such as the Amoeba or an Infusorian, arc said to be
unicellular. Cells grow by absorbing cell-food — i.e., by the
assimilation of matter from without, and this matter maybe
in masses of considerable size when seen under the microscope.
Cells multiply by self-division. The egg-cell undergoes
division of the yolk into two, four,
eight, and afterward many cells ; the
cells thus formed become arranged into
two layers or sets called germ-layers.
The outer is called the ectoderm and
the inner the cndodcrm. A third germ-
layer arises between them, called the
Fig. 3.-Gcrm of s.-iiritta. mexmlerm or middle germ-layer. From
ec, ectoderm ; <»«. endorterm; f]1Ocp <rprm 1'lVPrs or Ppll-1-ivPiN tliP
both layers formed of mi- tb' IS'
cieated ceils. fix* lies of the body are formed, such as
muscle, bone, nerve, and glandular tissue. These tissues
form organs, hence animals (as well as plants) are called or-
ganisms, because they have certain parts formed of a partic-
ular kind of tissue set apart for the performance of a special
sort of Avork or physiological labor. This separation of
parts for particular or special functions is called differentia-
tion ; and the highest animals are those whose bodies are
most differentiated, Avhile the lowest are those whose bodies
are least differentiated ; hence high animals are specialized,
and, on the other hand, low animals are xiinple. Thus dif-
CELLS AND TISSUKS. 7
ferentiation of organs involves the division of physiological
labor.
Tissues. — Of the different kinds of tissues there is, first,
epithelial tissne (Fig. 4) consisting of cells with a nucleus and
nucleolus, and placed side by side, forming a layer. All the
organs develop originally from epithelium, which is the prim-
itive cell-structiire and forms the tissues of the germ-layers.
Epithelial cells form the skin of animals, and also the lining
of the digestive canal. The cells of the latter may, as in
sponges, bear a general resemblance to a flagellate infuso-
Fig. 4. — Vertical section through the skin of an embryonic (-hark, showing at # the
epithelial cells, forming the epidermis; c, corium; K, columnar epithelium. — Afte^
Gegenbaur.
rian, as Codosiga, or they may each bear many hairs, called
cilia, which by their constant motion maintain currents of
the fluids passing over the surface of the epithelium. The
tissue forming glands is simply modified epithelium.
Connective tissue is formed by isolated rounded or elon-
gated cells with wide spaces between them filled with a ge-
latinous fluid or protoplasm, and occurs between muscles,
etc. An analogous (but hypoblastic) tissue forms the '•* no-
tocord," a rod supporting the bodies of vertebrate embryos.
Gelatinous tissue is a variety of connective tissue found in
the umbrella of jelly-fishes (Aurelia, etc.). Fibrous and
elastic tissue are also varieties of connective tissue.
Cartilaginous tissue is characterized by cells situated in a
8
ZOOLOGY.
still firmer intercellular substance ; and when the intercel-
lular substance becomes combined with salts of lime form-
ing bone, we have bony tissue.
The blood-corpuscles originate from the mesoderm as
independent cells floating in the circulating fluid, the blood-
cells being formed contemporaneously with the walls of the
vessels enclosing the blood. In the invertebrates the blood-
cells are either strikingly like the Amoeba in appearance, or
-i.ii.iL .•mau ^"uea.. jaJJUi t " UB ai6 OVa^ ^llt S^'^ Capable of
corpuscles arise like other tissues,
Fig. 5.— Striated muscular fibrilla PYr>Anf tli-ir HIPV fin-illv lippnmp
of a water bwtle.-After Minol. 6XC6pC
free.
Muscular tixxue is also composed of cells, which are at
first nucleated and afterward lose their nuclei. From being
at first oval, the cells finally become elongated and more or
less spindle-shaped, forming fibres ; these nnite into bundles
forming muscles. Each fibre is ensbeathed in a membrane
called xarcolemma. Muscular fibres may be simple or striated
(Fig. 5). The contractility of muscles is due to the con-
tractility of the protoplasm
originating in the cells forming
the fibres.
Nervous tissue is made up
of nerve-cells and fibres pro-
ceeding from them ; the for-
mer constituting the centres
of nervous force, and usually
massed together, forming a
ganglion or nerve-centre from
Which nerve-fibres paSS to the Fis. 6.-A gnnglion in the clam, with
periphery and extremities of
the body, and serve as conductors of nerve-force (Fig. G).
Organs and their Functions. — Having considered the
different kinds of cells and the tissues they form, we may
now consider the origin of organs and their functions. The-
Protamceba may be considered as an organless being. In
Amoeba (Fig. 11) we first meet with a specialized portion of
the body, set apart for the performance of a special function.
ORGANS AND THEIR FUNCTIONS.
Such is the nucleus ; so that Amoeba is a genuine organism.
Ascending to the flagellate Infusoria (Fig. 1), we have the
flagella developed as external, permanent organs of locomo-
tion. In the Hydra (Fig. 36) the tentacles are organs
whose functions are generalized. In the worms we have or-
gans arranged in pairs on each side of the body, and in gen-
eral among the higher invertebrates, especially the crusta-
ceans and insects, and markedly in the vertebrates, we have
the bilateral symmetry of the body still farther emphasized
in the nature and distribution of the appendages.
Of the internal organs of the body, the most important is
the digestive cavity, which is at first simple and primitive in
the gastrula or embryo of all many-celled animals, and as we
ascend in the animal series we witness its gradual special-
ization, the digestive tract being differentiated into dis-
tinct portions (i.e. , the oesophagus, stomach, and intestine),
•each with separate functions while the organs of respiration,
digestion, secretion, and excretion originate as oifshoots or
outgrowths from the main alimentary tract. In like man-
ner the skeleton is at first simple and afterward is extended
into the different organs, the various parts of the ap-
pendicular skeleton corresponding to the increased flexi-
bility and diversified leverage power ; so that limbs become
.subdivided into joints, and these joints still further subdi-
vided as we go from the points of attachment to the peri-
phery or extremities, as seen in the tendency to an irrelative
repetition of joints in the limbs and feelers of crustaceans
.and insects, and the digits of the lower vertebrates.
Correlation of Organs — Cuvier established this princi-
ple, showing that there is a close relation between the forms
of the hard and soft parts of the body, together with the
functions they perform, and the habits of the animal. For
example, in a cat, sharp teeth for eating flesh, sharp curved
claws for seizing smaller animals, and great muscular activ-
ity coexist with a stomach fitted for the digestion of animal
rather than vegetable food. So in the ox, broad grinding
teeth for triturating grass, cloven hoofs that give a broad
support in soft ground, and a several-chambered stomach
coexist with the habits and instincts of a ruminant. Thus
10 ZOOLOGY.
the form of the teeth presupposes either a ruminant or carni-
vore. Hence this prime law of comparative anatomy led to
the establishment by Cuvier of the fundamental laws of
palaeontology, by which the comparative anatomist is en-
abled to restore from isolated teeth or bones the probable
form of the original possessor. Of course the more perfect
the series of bones and teeth, or the more complete the re-
mains of insects or mollusks, the more perfect will be our
knowledge, and the less room will there be for error in re-
storing extinct animals.
Adaptation. — An organ with a certain normal use or
function may be adapted, in consequence of a change in the
habits of the animal, to another use than the original one.
To take an extreme case, the Anabas, or climbing fish, may
use its fins to aid it in ascending trees. On the other hand,
by disuse organs become aborted or rudimentary. The
teeth of the whalebone whale are rudimentary in the young,
and are replaced by whalebone, which is more useful to the
animal ; the eyes of the blind-fish are rudimentary, func-
tionless. Those of certain cave-insects are entirely wanting,
being lost through disuse, owing to a change of life from
the light, outer world to totally dark caverns, and the con-
sequent disuse of their eyes. Nature is economical. Every
thing that is not of use as a rule disappears. It would be a
waste of material to nourish and care for an organ in a cave-
animal, or a parasitic insect or crustacean, which would be
of no use to the animal. On the other hand, if the leg or
tail of a newt is snipped off by some rapacious fish, it
grows out again.
Moreover, the animal organism is far more pliable than is
generally supposed. Not only is nature continually repair-
ing wounds and waste, not only is the body being contin-
iially made over again, but certain animals undergo a
change of form, either generally or in particular parts. If
the environment is unchanged, the animal remains true to
its species. The dogma of the invariability or stability of
species is a fallacy. Change the climate, moisture or dryness,
the nature of the soil ; introduce the natural enemies of the
animal or remove them ; destroy the balance of nature, in
LA W OF INHERITANCE AND TRANSMISSION. 11
other words, and the organism changes. The plants and
animals of the mummies and monuments of Egypt are prob-
ably the same as those now living in that country, because
the climate and soil have remained the same.
The assemblages of life that have successively peopled the
surface of the earth, and which are geological time-marks,
have probably become extinct because they could not adapt
themselves to more or less rapid oscillations of continents
and islands, to consequent changes of climate and the in-
coming of destructive types of life. This probably accounts
for the origin, culmination, and extinction of different
types of life. The earth has been, and still is, in a state of
unstable equilibrium. Organic life has been and is even
now, in a degree, being constantly readjusted in harmony
with these changes of the earth's surface and climate. Thus
this adaptation of organs to their uses, of animals to their
environment, the laws controlling the origination of new
forms of life and the extinction of those which have acted
their part and are no longer of service in the economy of
nature, is part of the general course of nature, and evinces
the Infinite Wisdom and Intelligence pervading and contin-
ually operating in the universe.*
Coupled with variability is the law of inheritance and
transmission of variable parts, and the habits thus induced
by the variation of parts. It should he observed that the
portions which vary most are the peripheral parts — i.e.,
fingers and toes, tentacles and antennae, the skin and scales
and hair ; it is by modifications and differences brought
about in those parts most used by animals that the multi-
tudes of specific forms have resulted. There is, as Darwin
states, a general tendency of organisms to vary ; the laws
accounting for this tendency to vary have yet to be formu-
lated ; though the attempts of Lamarck in this direction
laid the way for the discovery and application of the funda-
* That animals and plants are self-evolved, that the world has made
itself, and that all is the result of so-called physical and biological laws
operating from within outward, is as inconceivable as the mediaeval
dogma that animals and plants and the earth they inhabit were made
in the twinkling of an eye. See the concluding chapter on Evolution.
12 ZOOLOGY.
mental laws of evolution. On the other hand, pure Dar-
winism— viz., natural selection — accounts rather for the
preservation than the origination of the forms of life.
Analogy and Homology. — When we study the Inverte-
brates alone we see that it is often easy to trace a general
identity in form between the more important parts. The
parts of the sting of a bee are originally like the feet or jaws
of this insect, though the functions of these parts may be
quite unlike ; these are therefore examples of a general
identity in structure or homology between two organs. A
closer homology implies a more apparent identity of form,
as seen in the resemblance in structure of the fore-limbs of
a whale and a seal, or the pectoral fins of fishes and the
arms of man, or the wing of a bird and the human arm.
Analogy implies a dissimilarity of structure of two organ*
with identity in use, as the wing of an insect and of a bird ;
the leg of an insect and the leg of a frog ; the gill of a.
worm and the gill of a fish.
Homology implies blood-relationship ; analogy repudiates
any common origin of the organs, however physiologically
alike. The most general homologies are those existing in
organs belonging to animals of different branches ; the most
special between those of the same orders and minor groups.
Thus it is fundamentally a question of near or remote con-
sanguinity.
Physiology treats of the mode in which organs do their
work ; or, in other words, of the functions of different or-
gans. Thus the hand grasps, the fins of a fish are its swim-
ming organs ; the function of the nose is to smell, of the
liver to secrete bile, of the ovary to secrete protoplasm,
which forms eggs.^
Psychology is "the study of the instincts and reasoning;
powers of animals ; how they act when certain parts are
irritated ; so that while this term is generally applied to
man alone, Comparative Psychology deals both with the
simplest automatic acts and the whole series of psychic pro-
cesses— from those exercised by the Protozoans, such as
Amoeba, up to the complicated instinctive and rational acts
of man.
REPRODUCTION AND EMBRYOLOGY. 13
Reproduction. — The simplest form of reproduction is
cell-division, one cell budding or separating from another.
This mode of growth is called self-division or fission.
Where one cell separates from another, the separating part
being smaller than the original cell, or where a number of
cells separate or bud out from a many-celled animal, such as
a Hydra, the process is culled, gemmation. A third mode of
reproduction is sexual, the sperm-cell of the male coalescing
with the nucleus of the egg ; the commingling of the pro-
toplasm of the two nuclei resulting in a series of events
leading to the formation of a germ or embryo.
Embryology is, strictly speaking, a study of the develop-
ment of animals from the beginning of life of the egg up to
the time the animal leaves the egg or the body of the parent
—namely, up to the time when it begins to shift for itself ;
but the term embryology may also be applied to the grow-
ing animal from the egg to the adult condition. Many of
the lower animals undergo a metamorphosis, suddenly as-
suming changes in form, accompanied by changes in habits
and surroundings; so that at different times it is, so to
speak, a different animal. For example, the caterpillar
lives on solid food, crawls on the ground, and has a worm-
like form ; it changes to a chrysalis or pupa, lying quies-
cent, taking no food ; then it changes to a butterfly and
flies in the air, either taking no food or sipping the nectar
of flowers : in all these three stages it is virtually different
animals with different surroundings. Many animals besides
insects have a metamorphosis, and their young are called
larvas ; thus there are larval polyps, larval star-fish, larval
worms — these larvae often differing remarkably in form,
habits, and in their environment or surroundings, as com-
pared with the mature or adult forms.
Classification. — After thoroughly studying a single ani-
mal, its external form, how it acts when alive, its external
and internal anatomy after death, and the development; of
other individuals of its own species, the student is then ready
to study the classification of animals.
The best method of studying classification, or Systematic
Zoology, is to make an exhaustive examination of one an-
14 ZOOLOO Y.
imal, and then to study in the same thorough manner an
allied form, and, finally, to compare the two. For example,
take a frog and compare it with a toad, and then with a
newt, or a land salamander ; thus, by a study of the different
types of Batrachians, one may arrive at a knowledge of the
affinities of the different species of the class. The methods
of research are, then, observation and comparison. The
best and most philosophic observers are those who compare
most. Then, passing on to other animals, the student will
place in one group animals that are alike. He will find that
many agree in certain general characters common to all.
He will thus form them into classes, and those that agree in
less general characters into orders, and so on until those
agreeing in still less important characteristics maybe placed
in categories or groups termed families, genera and species,
varieties and races. For example, the cat belongs to the
•following groups :
Kingdom of Animals ;
Sub-kingdom, or branch, Vertebrates ;
Class, Mammalia ;
Order, Carnivora ;
Family, Felidaa ;
Genus, Felis ;
Species, Felis domesticus Linnaeus ;
Variety, Angorensis.
But these different groups are insufficient to represent the
almost endless relationships and series called the System of
Nature, which our classifications attempt to represent.
Hence we have sub-species, sub-genera, sub-families and
super-families, sub-orders and super-orders, and sub-classes
and super-classes, and the different assemblages may be
grouped into series of orders, families, etc.
The relations of the members of these different groups
may be represented in the same manner as the genealogi-
cal tree of the historian, or like a tree, with its trunk
and branches and twigs ; or on a plane by a cross-section
through the tree, the different groups or ends of the
branches resembling a constellation, and embodying one's
EIGHT BRANCHES OF THE ANIMAL KINGDOM. 15
idea of the complicated relations between animals of differ-
ent groups.
The Animal Kingdom may be divided primarily into
two series of branches ; those for the most part composed
of a single cell, represented by a single branch, the Proto-
zoa, and those whose bodies are composed of many cells
(Metazoa), the cells arranged in three fundamental cell-
layers — viz., the ectoderm, mesoderm, and endoderm. The
series of Metazoa comprises the seven higher branches — i.e.,
the Porifera, Ccelenterata, Vermes, Echinodermata, Mol-
lusca, Arthropoda, and Vertelrata. Their approximate
relationships may be provisionally expressed by the follow-
ing
TABULAR VIEW OP THE EIGHT BRANCHES OF THE ANIMAL KINGDOM.
VIII. Vertebrata.
Ascidians to Man.
VII. Arthropoda.
Crustaceans and Insects.
VI. Mollusca.
Clams, Snails, Cuttles.
V. Ec?imodermata.
Crinoids, Starfish, etc
I
IV. Vermes.
Worms.
III. Ccelenterata.
Hydra, Jelly-fishes.
I
II. Porifera.
Sponges.
METAZOA.
Many-celled animals, with 3 cell-layers.
I
I. PROTOZOA.
Single-celled animals.
It should be understood by the student that the classifi-
cation presented in this book is a provisional one, based on
our present knowledge of the structure of the leading types
16 ZOOLOGY.
of the animal kingdom, and may be regarded as rudely in-
dicating the blood-relationship or pedigree of animals. It
differs in some important respects from the classifications
given in the books ordinarily in use by American students.
Some authors retain the four types of Cuvier, but it
should be remembered that since Cuvier's classification was
proposed in 1812 our knowledge has been greatly extended.
The microscope has revealed an immense mass of new mi-
croscopic forms, and many facts regarding the structure and
development of the larger forms. The embranchments of
Cuvier are in all cases, except the Vertebrates, unwieldy, het-
erogeneous, and, in the light of our present knowledge, un-
natural assemblages of animals. New discoveries do away
with old systems, and the classifications adopted by differ-
ent authors represent the standpoint from which they re-
gard the system of nature. It is not of so much consequence
to the student to know what the system may be, as to learn
the leading facts of animal morphology and development.
Palaeontology. — With a thorough knowledge of the anat-
omy of animals and their classification, the student is pre-
pared to study the remains of extinct animals, to restore so
far as possible their forms, and to classify them. With a
knowledge of the hard parts of existing animals, and of the
interaction of the tendons, ligaments, muscles, and bones,
the palaeontologist can, in accordance with the law of cor-
relation of parts, refer fossils to their respective orders,
families, genera, or species.
Zoogeography, or geographical distribution, is the study
of the laws of distribution of animals over the surface of
the earth or over the bottom of the sea. The assemblage
of animals inhabiting any area is called & fauna. Thus we
have an arctic fauna, a tropical fauna, a North American
fauna, or Australian fauna. The fauna of the ocean is sub-
divided into different subordinate faunae.
CHAPTER I.
BRANCH L— PROTOZOA.
General Characters of Protozoans. — We can imagine no
more elementary forms of life than certain members of this
branch, whose bodies in the simplest forms are merely
masses of albumen, without any distinct permanent organs,
or portions set apart for the performance of any special
function. Yet the primary acts of animal life, such as tak-
ing food, its digestion and assimilation, and reproduction,
are carried on as effectively by these lowest as by the high-
est forms. The simplest Protozoans are like minute drops
of protoplasm or albumen, having a gliding motion, and
constantly changing their forms, throwing out temporarily
root-like projections called
pseudopodia, which serve to
gather food-particles. Fig.
7 illustrates a typical Proto-
zoan. It is the common
Amoeba of standing water.
Most Protozoans are provid-
ed with a central organ or
nucleus, which corresponds
to the reproductive organs of the many-celled animals.
The Protozoa are one-celled in distinction from all other
animals, from the sponges to man, which are many-celled,
though it is claimed that a few shelled forms (Rhizopods) are
composed of several indistinct cells. Thus a Protozoan cor-
responds to an egg or to any one of the cells composing the
bodies of higher animals. They may be naked, as in Proia-
mceba or Amceba, or may secrete a silicious or calcareous
shell. The Infusoria, forming the highest class, are quite
complicated, with permanent cilia, a mouth, throat, repro-
Fig. 7. — Amoeba, the nucleus not shown.
18 ZOOLOGY.
ductive nucleus, and several contractile vesicles, rudely an-
ticipating the heart of higher animals. Protozoans repro-
duce by self-division and the formation of motile germs
(zoospores), and in the Infusoria of ciliated young. There
is thus a great range of forms leading from the most primi-
tive type (Protamcebd) to the most specialized forms, such
as the bell animalcule ( Vorticella.}
CLASS I. — MONERA (Moners).
General Characters of Moners. — This group comprises
the simplest forms of Protozoans, whence the name Monera
(novr'i/jes, simple). The lowest forms are almost identical
in appearance with the lowest plants, and they can only
Fig. 8. — Protomortas amyli, greatly magnified. -4. when encysted; x. germs or zo-
ospores ; y, food-mass. B, germ freed from the parent-cyst. C, I), older germs. E,
adult encysted ; y. food ; s, projection inward of the cell-wall ; x, wall of the cyst ; t,
germs. — After Cienkowski.
be claimed to be animals from their resemblance to higher
forms leading to Ammba, which, in turn, is connected by a
series of forms leading to undoubted animals, such as the
shelled Rhizopods (Fig. 14).
The Monera differ from the "Rhizopods (Amoeba, etc.) in
wanting a nucleus and contractile vesicles. Their body-
substance is homogeneous throughout, not divided into a
tenacious outer and softer inner mass, as in Amoeba. They
move by the contraction of the body, and the irregular pro-
trusion of portions of the body forming either simple pro-
cesses (pseudopodid) or a network of gelatinous threads.
The food, as some diatom, desmid, or protozoan, is swallowed
MONERA. 19
whole, being surrounded and engulfed by the body, and the
protoplasmic matter is then absorbed, serving for the nour-
ishment and growth of the Moner.
The simplest form known, and supposed to be really a living
being, is Haeckel's Protamoeba. It may best be described
by stating that it is like an Amoeba, but without a nucleus
and vacuoles (or little cavities). It reproduces by simple
self -division, much as in Amoeba (Fig. 11).
In Protomonas the body is very changeable in form, the
pseudopods often being very slender, thread-like. Fig. 8,
A represents this Moner during the formation of the young
(zoospores) in the cyst-like body, or resting-stage of the
creature ; B, one of these .germs freed from the cyst and
capable of moving about by the two thread-like pseudopo-
dia ; C D, the Amoeba-like form which the young after-
ward assumes, and which at maturity passes into the en-
cysted or resting- stage E.
A still better idea of what a Moner is may be seen by
studying the Protomyxa aurantiaca Haeckel.
This Moner was discovered at the Canary Islands. It is
from half to one millimetre in diameter, and is a perfectly
simple mass of orange-red jelly. When hungry numerous
root-shaped threads (pseudopodia) radiate from the central
mass. Fig. 9, E represents the Protomyxa after having
absorbed into its body-mass a number of shelled Infusoria.
When about to become encysted (A B) it rejects the shell
of its victims, retracts its false feet, and soon becomes fast-
ened as minute red balls to the surface of some dead shell.
The ball becomes enclosed by a thick covering (A], and
then the contents become divided into several hundred small,
round, thoroughly structureless spheres, which become germs
(B}. The germs finally burst through the cyst-wall, as in
C, a, c, d, and assume various monad-like and amoeboid
shapes, and finally attain, by simple additions of the proto-
plasm of its food (diatoms and infusoria), the adult form
(D E}. Other Moners exist in fresh water.
We have been dealing with the simplest living forms, be-
ings showing no trace of organization, much lower and
simpler than the Amceba, with its nucleus. The individual
20 ZOOLOG Y.
Moner — for example, Pro/amoeba — is simply a speck or drop
of transparent, often colorless, viscid fluid, scarcely of more
consistency than, and in all apparent physical characters
identical with, the white of alien's egg. And yet this drop
of protoplasm has the power of absorbing the protoplasm of
other living beings, and thus of increasing in size — i.e.,
growing ; and in taking its food makes various movements,
one or more parts of its body being more movable than
Fig. 9.—Protomyxa aurantiacn. A, encysted. B, cyst filled with serins. C, germs
(T, d. c) issuing from (he cyst. 1), a young Protomyxa swallowing a diatom (a).
E. adult after enc'ooiiig or swallowing several shelled Infusoria. — Aftei Haeckel.
others, the faculty of motion thus being for the moment
specialized ; it has apparently the power of selecting one
kind of food in preference to another, and. finally, of repro-
ducing its kind by a process not only of simple self -division,
but also of germ-production. In short, AVC may say of the
Moner what Foster says of the Amoeba — viz., (1) it is con-
tractile ; (2) it. is irntable and automatic • (3) it is receptir:-
MONERA. 21
and assimilative ; (4) it is metabolic and secretory in the
sense that the Moner digests and separates the portions
necessary for food from those which it rejects as waste ; (5)
it is respiratory, the changes involved in taking food, es-
pecially oxygen, causing the production of and excretion of
carbonic acid ; (6) it is reproductive.
It is difficult to conceive of a simpler form of life than
Protamceba or Protomonas. Are the Moners animals or
plants, or do they represent a neutral division or group of
forms ? It was formerly thought that Amoeba was the sim-
plest possible form of life, but we shall see that that animal
is an undoubted organism, possessing a permanent organ,
the nucleus. Moreover, the Amoeba intergrades with the
other Rhizopods which are undoubted animals, while the
simplest Monera have no characters which absolutely sepa-
rate them on the one hand from the plants or on the other
from the animals. Their relation to the plants is seen in
the fact that, besides the resemblance to the lowest plants,
the cyst of Protomonas is composed of cellulose, while the
granular contents of the body become colored with chlo-
rophyll.*
For these reasons, Haeckel, the discoverer of the Monera,
regards them as neutral beings, neither plants nor animals.
But by comparison with other Protozoa, we shall see that
the Monera only differ from the monads and Amoeba} by the
absence of a nucleus. This may yet be found to occur in
the Monera, and from this fact we separate the group only
provisionally from the Rhizopoda. The Gregarince also pass
through a true Moner-stage. This indicates that the
Monera are allied rather to animals than plants. Another
point of difference from plants is the fact that, like the
Amoeba, they engulf living plants (desmids, etc.) and ani-
mals (Infusoria), the only plants known to do this being the
singular Myxomycetes, whose position is uncertain, some
naturalists (Allman) regarding it as an animal.
It is probable that the Monera were the earliest beings to
* On the other hand, cellulose occurs in the integument of Tunicates,
and various parts of Articulates and Vertebrates, while chlorophyll
occurs in the Infusoria and Hydra.
22 ZOOLOGY
appear, and that from forms resembling them all other organ-
isms have originated. We can conceive at least of no simpler
ancestral form; and if organized beings were originally pro-
duced from the chemical elements which form protoplasm,
one would be naturally led to suppose that the earliest form
was like Protamoeba. It would follow from this fact that the
Monera are as low as any plants, and that animals appeared
contemporaneously with plants.
Having studied a few typical forms of Monera, we are
prepared to briefly define the group and tabulate the sub-
divisions of the class.
CLASS I.— MONERA HAECKEL.
Beings consisting of transparent protoplasm, containing granules, some-
times forming a net-work, but with no nucleus* or contractile vacuole ;
capable of automatically throwing out pseudopodia, and reproducing by
simple self-division of the body-mass into two individuals, or by division
into a number of germ-like or spore-like young, which increase in size by
absorption of tlie protoplasm of other organisms.
Group 1 . Gymnomonera, comprising the genera Protamoeba, Protogenes,
and Myxodictyum, which do not become encysted.
Group 2. Lepomonera, which become encysted and protected by a
case, as in the genera Protonionas, Protomyxa, Vampy-
rellu, and Myxastrum.
CLASS II. — KHIZOPODA (Root Animalcules}.
General Characters of Rhizopods. — An idea of the form
and internal structure of this group can be obtained by a
study of Amoeba, which may be found sliding over the sur-
face of the leaves of plants growing in pools or ponds of
fresh water. Our common Amoeba has been studied by
H. J. Clark. Fig. 10 represents this animal in the three
more usual forms which it assumes. From time to time
the sides of its body project either in the form of simple
bulgings, or suddenly it throws out foot-like projections
* Should a nucleus be found hereafter to occur in the Monera, the
group should be merged into the Rhizopoda, and placed next to
Amoeba.
RH1ZOPODA.
(pseudopodia) from various parts of the body, as if it
were falling apart ; then it retracts these transparent feet
and becomes perfectly smooth and rounded, resembling a
drop of slimy, mucous mat-
ter. The body-mass is di-
vided into a clear cortical and
a medullary, granular mass ;
the outer highly contractile,
the inner granular portion
acting virtually as a stock of
fnnrl Timer, frrnnnloe lil-n Fi~ 10 •" Amffba diffluens Ehr. A, the
IOOC1. InCbC granules, Jlke ]eft,han«l figure, the most usual form ; the
flip trvqins of rhlmvmli vll in "tflu shows rhe broad, flat pseudopodia;
IJie grams OI ClUOlOpnyil 111 ,he arrows indicate the direction of circula-
vegetable cells and in dia- tionof the granules.- After dark,
toms and desmids, circulate in regular, fixed currents, the
arrows in the figure indicating the course of the circulating
food. The act of circulation is probably assisted by a con-
tractile vesicle (or
vacuole) usually
present. There is
besides a distinct
organ always pres-
ent, the nucleus (see
Fig. 11), so that the
Amoeba earns the
right to be called
an organism. Its
food consists of one-
celled algie, diatoms,
desmids, zoospores,
and portions of fila-
mentous algse, and it
possesses the power
of discrimination in
Fig. 11. — Amce,ba spharoroccus. A, before division. .
7?, the same in its resting stage; a, cyst or cell-wall; taking its lOOd. Pile
<l, body-mass; c, nucleus; b, nucleolus. 6', Amreba
nearly divided. D, two young Amoebae, the result of AmO3Ua lias the DOW-
di vision.— After Haeckel. ,. . .
er 01 moving in par-
ticular directions, stretching a millimetre in length ;
it
selects appropriate food, and can engulf or swallow, digest
and distribute the lood thus absorbed to various portions of
24
ZOOLOGY.
its body. The Amoeba reproduces its kind by simple di-
vision, as seen in Amoeba sjrficerococcus Haeckel (Fig. 11).
This species, unlike others, so far as known, becomes encysted
(B}, then breaks the cell- wall and becomes free as at A.
Self-division then begins as at C, the nucleus doubling it-
self, until at D a and D b we have as the result two individ-
uals.
Order 1. Foraminifera. — Besides Amoeba, several other
forms, either naked or shelled, produce, by division of an in-
ner portion of the body, numbers of ciliated young, as in
the naked Pelomyxa, in certain many-chambered Fora-
minifera, and in CoIIospJiop-
ra. An example may be
seen in the European Pelo-
myxa palusfris Greef (Fig.
12). This creature lives in
the mud at the bottom of
fresh-water pools, and when
first seen resembles little
dark balls of mud a milli-
metre in diameter. Instead
of one nucleus, there are
numbers of them, and nu-
merous contractile vacuoles
Fig. la.— Pelomyxa pali/^tris. A, a, clear ,,,, , .., ,, . -. ,,
•cortical portion; />. diatoms enclosed in the filled With a 11111(1, together
body-mass. B, amoeba-like bodies originating -,i • i rn
from the nuclei, which after leaving the body With SplCUlCS. J lie yOUllg
pass into monad-like forms, C ' ; it. nucleus; j. fl j. „,-,,, pi™ IjVp / R\
4, contractile vesicle.— After Greef. 1Kt \n)>
originating as " shining
bodies," which have resulted from the self -division of the
nuclei. These amoeba-like bodies finally assume an active,
monad-like stage C, and move about by means of a cilium
or lash.
We now come to the shelled Amcebse, or genuine Forami-
nifera. A common type is Arcella, which secretes a one-
•chambered silicious shell, found in fresh water, and a
representative of the monothalamous, or one-chambered,
Foraminifera* ; while* the many-chambered forms are
marine, of which Globigerina bulloidex (Fig. la), found
floating on the surface of the ocean, with its psendopodia
* See Leidy's Fresh water Rhizopods of North America, 1879.
FORA H IN IF ERA .
thrown out in all directions, is a type ; Rotalia veneta (Fig.
14) is another example.
The Foraminifera are nucleated. Diplophrys multiplies
by a " process of con-
tinuous binary fis-
sion." Miliola gives
rise to small round,
sharply - defined bod-
les, in calcareous
shells, with one turn,
but no inner Avails,
.and with pseudopo-
dia like those of the
adult. Microgromia so-
cialis multiplies by zo-
ospores, which are oval,
With two fiagella ; Or, Fig. 13.— A Foraminifer. GMir/emna bullmdes,
, -i ,1 magnified 70 diameters.— From Mac.allister.
in other cases, the
young assume an actinophrys-like form, and move about by
the aid of three or four more or less branched pointed pseudo-
, ,, , /// pods (HertAvig).
II 'i j iji, \ Ijl /////. I If
Fig. 14. — Rotalia. A Rhizopod, showing the pseudopodia.
chambers are
numerous and
regular, the
shells being flat
and consisting
of eight coils sit-
uated in the
same plane. A
recent species ot
F'o rami n i fer
found at Borneo
measures more
than two inches
in diameter, while a common form on the Florida reefs, de-
voured in large quantities by the Holothuria, or sea-cucum-
26
ZOOLOGY.
ber, measures about one fifth of an inch in diameter. Most
of our native species are much more minute. The Eozoon,
so-called, is supposed by some to be a Foraminifer, but
others regard it as more probably inorganic, and simply a
Fig. 15. — B, Coltotph&ra spi-
nosa. with projecting conical
points, containing little sphe-
roids, which paps into monad-
like bodies C. D, probably an
early stage of C. A, a young
capsule or C. Hiixleyi Miiller.—
After Cienkowski.
Fig. 1C. — ActinospfKerium. a, amor-
eel or food drawn into the cortical layer
b; c, central parenchymatouB mass of
the body ; d, some balls of food-stuff in
the latter; e, pseudopodia of the cortical
layer. — After Gegenbaur.
Fig. Vt.—Heliophrysvariabilis. A sun
animalcule, showing the pseudopods
nuclei, and vacuoles. — From Macallister,
mineral. Undoubted Foraminifera occur in the Silurian
formation, while large masses of carboniferous and ere'
taceous rocks are formed by their shells.
Order 2. Radiolaria. — These Rhizopods have the general
structure of Amoebae, but secrete beautiful silicious shells,
RHIZOPODA. 27
of varied forms, more or less spherical, perforated for the
protrusion of the pseudopodia, with often spicules or points
radiating from the shell. They reproduce apparently by
self -division of the interior, resulting in a swarm of monad-
like young. The Heliozoa are represented by the fresh-
water Actinopltrys sol, which is round, with numerous stiff
pseudopodia radiating in all directions from the body, and
by Actinospha?rium (Fig. 1C). The true marine Radiolaria
are represented by Collosphcera spinosa Cienkowski (Fig. 15).
It possesses a perforated shell beset with small spines, which
encloses a capsule with a protoplasmic wall. In the capsule-
stage (A) it often divides by fission into two halves. After-
ward the older capsule divides into a number of little round
bodies, Avhich develop two lashes as in C.
CLASS II.— RHIZOPODA.
Unicellular organisms consisting of protoplasm, with an outer clear,
cortical, and an inner granular mass containing one or more nuclei, and
one or more contractile vacuoles ; moving by means of pseudopodia, and
either naked or secreting a one or many -chambered shell ; reproducing by
#elf -division, or by the production of several or many amoeboid or monad-
like young.
Order 1. Foraminifera. — One-celled Rhizopods with one or many nuclei
and contractile vacuoles, usually secreting chambered cal-
careous or horny (chitinous ?), rarely arenaceous, shells.
(Amreba, Globigerina, Nummulina.)
Order 2. Radiolaria. — Rhizopods with pointed, branched, usually anas-
tomosing and granular pseudopodia. The body contains
either numerous small heterogeneous nuclei, or a single
larger, highly differentiated vesicular nucleus. The pro-
toplasm of the body is further separated into a peripheral
non-nucleated and a central nucleated portion by a mem-
branous capsule with porous walls. Reproduction occurs
by the breaking up of the body into monad-like embryos,
with one or sometimes two locomotive lashes (flagella).
There are two divisions : (1) Heliozoa, (Actinophrys, Actino-
spluerium), and (2) Radiolaria (or Cytophora\ having as rep-
resentatives Acanthometra, Collozoiim, Sphaerozoum, and
Collosph^ra.
28
ZOOLOGY.
CIASS III. — GREOARTNIDA (Gregarines).
General Characters of G-regarinida. — The largest and
best known species of this group is tin inmate of the
intestinal canal of the European lobster, and was named
by E. Van Beneden Greganna yiyantea (Fig. 18). It
is worm-like, remarkably slender, and is sixteen mil-
Fig. l$.—Gregarina qigantea. L, two individual* of natural size. K, the same
much enlarged; », nucleic. A. the same encysted. B. subdivision of the cyst. 0, divi-
sion of the contents of cyst into small spheres, observed in another species. JV. the
spheres enlarged. M. ry*t filled with pseudonavicellse, 0.— After Lieberknhn. D— F.
moner-liko young of (f. gigantea. G, H, psuudofilaria stage. /, .7, early nucleated
forms of G'regwina yigantea.-A.fter Van Beneden.
limetres (over half an inch) in length, being the largest
one-celled animal known*. In this organism an external,
structureless, perfectly transparent membrane with a double
contour can be distinguished. It represents the cell-wall
of the cells in the higher animals. Beneath this outer Avail
is a continuous layer of contractile substance, forming a
true system of muscular fibrillse comparable to that of the
Infusoria. The body-cavity of the Gregarina contains a
* Excepting of course the larger Foraminifera.
GREGAR1NIDA. 29
viscid fluid holding in suspension rounded granules, among
which the nucleus rests. This nucleus contains an inner
vesicle or nucleolus, which strangely disappears and then
reappears. Van Beneden distinguishes three kinds of mo-
tions in the Gregarinas : 1. They represent a very slow
movement of translation, in a straight line, and without the
possibility of distinguishing any contraction of the walls of
the body which could be considered as the cause of the
movement. It seems impossible to account for this kind of
motion. 2. The next kind of movement consists in the
lateral displacement of every part, taking place suddenly
and often very violently, from a more or less considerable
part of its body. Then the posterior part of the body may
be often seen to throw itself out laterally by a brusque and
instantaneous movement, forming an angle with the anterior
part. 3. Owing to the contractions of the body, the gran-
ules within the body move about.
The life-history of this Gregarina is as follows : It occurs
in its normal state in lobsters in May, June, and August, but
in September becomes encysted in the walls of the rectum of its
host, the cysts (Fig. 18, A} appearing like little white grains
of the size of the head of a small pin. When thus encysted
the nucleus disappears, and the granular contents of the
cyst divide into two masses (B], like the beginning of the
segmentation of the yolk of the higher animals. Tbe next
step is not figured by Van Beneden, and we therefore intro-
duce some figures from Lieberkuhn which show how the
granular mass breaks up into spindle-shaped bodies (called
by some authors " pseudonavicellae," and by Lieberkuhn
" psorosperms") with hard shells. After the disappearance
of the nucleus and vesicle, and when the encysted portion
has become a homogeneous grarmlar mass, this mass divides
into a number of rounded balls (Fig. 18, C). These balls,
consist of fine granules, which are the spindle-shaped bodies
in their first stage (Fig. 18, JV). They then become
spindle-shaped (0} and fill the cyst (Fig. 18, J/), the balls
having meanwhile disappeared. From these psorosperms
are expelled amoeba-like masses of albumen (D E], which,
as Van Beneden remarks, exactly resemble the Protamceba
30
ZOOLOGY.
already described. This moner-like being, without a
nucleus, is the young Gregarinu.
But soon the Amoeba characters arise. The moner-like
young (Fig. 18, D E F} now undergoes a further change. Its
outer portion becomes a thick layer of a brilliant, perfectly
homogeneous protoplasm, entirely free from granules, which
surrounds the central granular contents of the cytode
(Haeckel) or non-nucleated cell. This is the Amoeba stage
of the young Gregarina, the body, as in the Amoeba, con-
sisting of a clear, cortical, and granula •
medullary or central portion.
The next step is the appearance of two
arm-like projections (Fig. 18, F), com-
parable to the pseudopods of an Amoeba.
One of these arms elongates, and, sepa-
rating, forms a perfect Gregarina. Soon
afterward the other arm elongates, ab-
sorbs the moner-like mass, and also be-
comes a perfect Gregarina. This elon-
gated stage is called a Pseudofilaria (Fig.
18, G) ; no nucleus has yet appeared.
In the next stage (Fig. 18, H n, nucleus)
the body is shorter and broader, and the
i^mnger6'±tt nucleus appears, while a number of gran-
ds (^Ih^d'1"^ ules collect at one end, indicating a
older; a, anterior end; b, head. After this the body shortens a
hinder part of the body; J
c, nucleus.— After Gegen- little more (7, J), and then attains the
f , • j 1 1 r- \ '
elongated, worm-like form of the adult
Gregarina (A'). Van Beneden thus sums up the phases of
growth :
1. The Moner phase.
2. The generating Cytode phase.
3. The Pseudofilaria phase.
4. The Protoplast (adult Gregarina).
5. The encysted Gregarina.
6. The sporogony phase (producing zoospores).
The Gregarinse and Amoebae constitute HaeckeFs group
THE INFUSORIANS. 31
of Protoplasta. Other Gregarinae are very minute, and are
parasitic in insects (Fig. 19), etc., and vary greatly in form,
some being apparently segmented, while in a few forms the
body ends anteriorly in a sort of beak armed with recurved
horny spines. We are now prepared to adopt the following
definition of the class :
CLASS III.— GREGARINIDA.
Amceba-like Protozoa, more or less elongated, with a determinate cell-
wall, with a subcuticular system of muscular fibrilla, with a nucleus, but no
contractile vacuole ; reproducing by encysting and subdivision of the cen-
tral mass of the body, producing shelly psorosperms, from which escape the
moner-like young, which undergo a metamorphosis into the usually worm-
shaped, parasitic adult (Gregarina).
CLASS IV. — INFUSORIA.
These organisms can best be understood by studying rep-
resentatives of the three orders forming the class.*
Order 1. Flngellata (Monads). — A familiar example of
monads, Oikomonas termo Clark, has been studied by H.
J. Clark. His description will suit our purpose of indi-
cating the form and habits of a typical flagellate animalcule.
It somewhat resembles our figure of Uvella in its general
shape, being pear-shaped, faint olive in color, and provided
with a vibratile locomotive lash or flagellum. In swimming,
the monad stretches out the flagellum, which vibrates with
an undulating, whirling motion, and produces a peculiar
graceful rolling motion. When the monad is fixed the fla-
gellum is used to convey food to the mouth, which lies be-
tween the base of the flagellum and beak, or " lip." The
food is thrown by a sudden jerk, and with precision, directly
against the mouth. " If acceptable for food, the flagellum
presses its base down upon the morsel, and at the same time
the lip is thrown back so as to disclose the mouth, and then
bent over the particle as it sinks into the latter. When the
lip has obtained a fair hold upon the food, the flagellum
withdraws from its incumbent position and returns to its
former rigid, watchful condition. The process of degluti-
* Kent's Manual of the Infusoria, London, 1880 ; Stokes' Microscopy
for Beginners, 1887.
32 ZOOLOGY.
tion is then carried on by the help of the lip alone, which
expands latterly until it
completely overlies the
particle. All this is done
quite rapidly, in a few sec-
onds, and then the food
glides quickly into the
depths of the body, and is
enveloped in a digestive
vacuole, whilst the lip as-
sumes its usual conical shape and proportions. " (Clark.)
All the monads have a contractile vesicle. In Motias
termo, Clark observes that it is " so large
and conspicuous that its globular form
may be readily seen, even through the
greatest diameter of the body ; and con-
tracts so vigorously and abruptly, at the
rate of six times a minute, that there
seems to be a quite sensible shock over
that side of the body in which it is em-
bedded." The contractile vesicle is
thought to represent the heart of the
higher animals. The reproductive organ
may possibly be represented in Monas
termo by a "very conspicuous, bright,
highly refracting, colorless oil-like globule
which is enclosed in a clear vesicle" called
the nucleus. This and other monads live
either free or attached by a slender stalk.
As an example of the compound or aggre-
gated monads may be cited Uvella, prob-
ably glaucoma of Ehrenberg. Other
forms, as Codosiga, are fixed by a stalk to
some object (Fig. 21, C. pulcherrimus
m i\ T 4-v,- i iv J * n i i Fig. M.-^. Gotoriga
Clark). In this and allied forms the body pulcherrimus. B. the
, , . same beginning to under-
is surmounted by a collar or calyx out 01 go fission, two new ti.i-
i • i , -I a 11 • mi r, gella appearing. C, two
Which the tiagellum projects. The CO- nearly separate individu-
dosiga has been observed by Clark to un- al8'
dergo fission, two independent monads resulting, within the
space of forty minutes.
THE FLAGELLATE INFUSORIA.
33
The first sign of fission is a bulging out of the collar,
which becomes still more bell-shaped. The flagellum next
disappears. Then marks of self-division appear in a nar-
row, slight furrow (Fig. 21, B, e], extending from the front
half way back along the middle of the body. Meanwhile
the collar, which had become conical, expands, and, most
striking change of all, two new flagella appear. Then the
collar splits into two (Fig. 21, 0), and soon the two new Codo-
sigae become perfected, when they split asunder, and become
like the original Codosiga. Such is the usual mode of mul-
tiplication of the species in the monads.
A few monads have been observed to become encysted, and
to break up into excessively minute bodies, from which new
monads have grown. Two
individuals of the same form
(Heteromita) in certain stages
fasten themselves together,
the larger absorbing the
smaller as if conjugating,
like Desmids, the compound
body resulting becoming en-
cysted ; finally the contents
of the cyst become divided
• ,i -i • , Fig. ll.—N'octiliica miliaris, after Hux-
mto either large or minute iey, and its /.oospores. », style :», nucie-
germs (zoospores) which as- U8' (
sume the parent form. The researches of Messrs. Dallinger
and Drysdale on Dallingeria Drysilali prove that while
the mature forms may be destroyed at a temperature of
142° F. , the motile germs of this and five other species of Infu-
soria perished when heated in fluid to from 212° F. to 208° F.
Noctiluca (Fig. 22) has been proved by Cienkowski to be
an enormous monad. It is a highly phosphorescent organ-
ism, so small as scarcely to be seen with the naked eye, be-
ing from £ to 1 mm. ('01 to -04 inch) in diameter. It occurs
in great numbers on the surface of the sea. It has a nearly
spherical jelly-like body, with a groove on one side from
which issues a curved filament, used in locomotion. Near
the base of this filament is the mouth, having on one side a
tooth-like projection. Connecting with the mouth is an CBS-
34 ZOOLOGY.
ophagus which passes into the digestive cavity, in front of
which lies an oval nucleus. Beneath the outer skin or firm
membrane surrounding the body is a gelatinous layer, con-
taining numerous granules. A network of granular fibres
arises from the granular layer ; these fibres pass into the
middle of the body to the nucleus and digestive cavity. The
young (Fig. 22, n, s) result from a division or segmentation
of the entire mass of the protoplasm of the body, forming
small oval bodies with a long lash. The zoospores are like
those of other Flagellata, and for this reason and the gen-
eral structure of the adult, Noctiluca is by the best author-
ities associated with the Flagellata. Noctiluca also under-
goes conjugation, but the zoospores
appear Avhether conjugation has oc-
curred or not. The Noctiluca on the
coast of the United States has been
observed in abundance on the surface
of the sea in Portland harbor, by Mr.
E. Bicknell. It is phosphorescent,
but whether identical with Noctiluca
miliaris of the European seas is not
known. Leptodiscus medusoides Hert-
wig, is discoidal or medusiform in
~Fig. 2S.—Acinetamys/acina, ' , , . , , , ,,. .,,.
with its stalk attached to a shape, the disk one and a halt milli-
plant ; with fifteen tentacles • -, • ^m\ j • i i, J
enciin^- in knob-like expan- metres in diameter. When disturbed
monger suckers, -From Mac- it ^.^ through fche water by the con.
tractions of its umbrella-shaped body.
It is allied to Noctiluca and was discovered at Messina.
Peridinium is the type of a third and higher division of
monads, the body being protected by a hard shell, with one
or more flagella, and a row of cilia serving as a locomotive
apparatus, and thus, together with Heteromastix and 7)//x-
teria, connecting the Flagellata with the Ciliata or true
Infusoria.
Order 2. Tentaculifera (Acinet-ae, Suctoria). — An Acineta
(Fig. 23) reminds us at first sight of a Radiolarian, since
the body is provided with filiform, tentacle-like processes
resembling the pseudopodia of a Radiolarian, but the ten-
tacles are in reality rather stiff, hollow, and act as suck-
THE CILIATE INFUSORIA.
35
II
III
n
m
cv
H
ers, so that when the organism has by means of its hollow
arms or tentacles caught some
Infuaorian, the arms con-
tract, draw the victim nearer
to the Ac-ineta, and when the
sucking disk at the end of the
arms has penetrated the skin,
the contents of the body of
the Infusorian are sucked into
the food-cavity of the Acine-
ta ; on the other hand, in
some Acinetse a portion of the
arms are simply prehensile.
These animals are in their
adult phase quite unlike the
Flagellata or Ciliata, but the
young are developed within
the parent and are provided
with cilia, being at first free-
swimming, and afterward
fixed by a long stalk. The
Acinetce sometimes self -di-
vide, sending off from the
free end of the body a ciliated
Acinete ; they have also been
seen to conjugate.
Order 3. Ciliata (Infuso-
ria). — A common type of this
group and one easy to obtain
by the student is Parame-
cium (Fig. 24), observed in
infusions, or moving rapidly
ii i i • n i • r it;. ^*. — ruTU'iiteviiuii, vuuuutu/ii. .»
OVer the bodies Of larger am- view from the dorsal side, magnified 340
mals which may be under the SS&,
microscope. Figure 24 rep-
rpcpnt« Pnrnmeriiim rniirlrt vesicles; I, II, III, the radiating canals of
raramecium cauaa- CTl. n'tl;e reproductive orga%. „, the
tum Ehrenberg. This ani- lareevibrating^iliaattheedgeoftlieves.
tibule.— After H. J. Clark.
malcule is a mass of proto-
plasm, representing a single cell. In the body-mass are ex-
Fig. 24. — Paramtcium caudatum. A
« »«* fi&5t
36
ZOOLOGY.
cavated a mouth and a throat leading to a so-called stomach
or digestive cavity. Two hollows in the body form the con-
tractile vesicles, and a
central mass constitutes
the reproductive organ.
Prolongations of the body-
mass form the cilia, which
characterize the Infusoria
and give the name to the
present order, Ciliata.
Paramecium has an elon-
gated, oval body "with
one end (H) flattened out
broader than the other,
and twisted about one
third way round, so that
the flattened part resem-
bles a very long figure 8."
In this form, as well as in
Stentor (Fig. 25), as Clark
remarks, "we have the
mouth at the bottom of a
broad notch or incurva-
tion, and the contractile
vesicle on the opposite
^^^ side, next the convex
F1-. i&.-stentor poiymoiyhu^^^ ia> back, whilst the general
diameters, expanded and bent slightly over to- y;j-v of 4-]ie body lies IjC-
wunl the observer; the mouth wi, next the eye, CdVlty < »uy
and the dorsal edge in the distance, d poste- fweell tllCSC two. ' The
rior end; sh, the tube enclosing d ; c, the cili-
ated border of the disk (s); v, the larger rigid arro\vs m the figure repre-
ciliu- CD, the contractile vesicle in the extreme . , i
dietance,seen through the whole thickness of the sent the COUl'SC OI the par-
body; CT1, CTZ, the posterior prolongation of co, , . ,
in the distance; >•, rl, the circular and radiating tlCieS Ot lllCUgO AVltll WlllC'll
branches of what, by Clark, waa supposed to be , .
a rudimentary nervous system; it, •//'. the re- Clark led. hlS Specimens,
productive system, extending from the right l( , Avhirlnd
side, at n, posteriorly, but toward the eye at /t1. Ub tliey dl
-After Clark. along, by the large vibrat-
ing cilia (v) of the edge of the disk, against the vestibule of
the mouth." During the circuit the food is digested, a
mass of rejectamenta is formed near the protuberance, a,
which has appeared a short time before. This finally
THE CILIATE INFUSORIA.
3?
a-
opens, allows the rejected matter to pass out, and then
closes over, leaving no trace of an outlet. This and other
Infusoria seem, then, to have a definite digestive tract, hol-
lowed out of the parenchyma of the body.
" The system," says Clark, " which is analogous to the
blood-circulation of the higher animals, is represented in
Parumecium by two contractile vesicles (cv, cvl, I, n, in),
both of which have a degree of complication which, per-
haps, exceeds that of any other similar organ" in these ani-
mals. When fully expanded they appear round, as at c v ;
but when contracted they appear, observes Clark, as " fine
radiating streaks, and as the main portion lessens they grad-
ually broaden and swell until the former is emptied and
nearly invisible, and
they are extended
over half the length
of the body. In this
condition they might
be compared to the
arterial vessels of the
more elevated classes
of animals, but they
would at the same
time represent the
veins, since they
serve at the next moment to return the fluid to the main
reservoir again, which is effected in this very remarkable
way." The contents of these vesicles is a clear fluid.
The reproductive organ in Paramecium is a small tube
(n), only seen at the reproductive period when the eggs (n]
are fully grown. Clark says that the eggs are arranged in
it " in a single line, one after the other, at varying dis-
tances." It usually lies in the midst of the body, and ex-
tends from one half to two thirds of the length of the ani-
mal. The eggs pass out from the so-called ovary through
an aperture near the mouth. Lasso-cells like those in the
jelly-fishes are said by Biitschli to exist in an infusorian
named by him Potykrikos.
In the trumpet animalcule (Fig. 25, Stentor polymor-
Fig. 26. — Process of fission in Stentor jtolymorp/u/s.
b, a new Stentor budding out; e, ready to separate from
the original one;,/, the two in a contracted state.—
After Cox.
38
ZOOLOGY.
pJms Ehrenberg) we have a rather more complicated form,
the infusorian attaching itself at one end by a stalk, and
building up a slight tube, into which it contracts when dis-
turbed. The Stentor may be sometimes observed multiply-
ing by self-division. Clark observed Stentor polymorphus
undergoing the process. The first change observed was the
division of the contractile vesicle into two. The mouth of
the new Stentor was formed in the middle of the under side,
Fig. 27.— Epislylis flamcons Ehr.. a single, many-forked colony of bell animalcules,
slightly magnified. Fig. 28, one of the animalcules magnified 250 diameters, p, the
stem; rf, the flat spiral of vibrating cilia at. the edge of the disk; ww, the muscle; m to
«, the depth of the digestive cavity ; in, the mouth ; y. </', the ihro.it. or rudimentary
digestive canal ; cv, the contractile vesicle ; //. the reproductive organ or nucleus. —
After Clark.
first appearing as a shallow pit, around which arises a semi-
circle of vibratile cilia. The mouth and throat form in the
new Stentor before any signs of division appear, but in the
course of two hours the body splits asunder, and two new in-
dividuals appear. Fig. 26 illustrates the mode of self-
division seen in Stentor polymorphus Ehrenberg, by Hon.
J. D. Cox. The process in this occupied two hours ; at the
final stage (Fig. 26, /) the connection between the two ani-
malcules parted, " and the two Stentors swam separately
THE CILIATE INFUSORIA. 39
away, both assuming the common form of the animalcule
when free-swimming, and differing from the original indi-
vidual only in being of smaller size."
The most complicated as well as most interesting form of
all the Infusoria is the bell-animalcule, Vorticella. It is
very common in pools, forming patches like white mould on
the leaves and stems of submerged plants. It may, like
Stentor, be observed under low powers of the microscope.
Their motions, as they suddenly contract and then shoot
out their bell, mounted on a long stalk, are very interesting.
The throat (oesophagus) is quite distinct, while the nucleus
is the most conspicuous organ of the body. The digestive
cavity is a large hollow in the protoplasm forming the body-
mass, in which the whole mass of food revolves in a deter-
minate channel. Closely allied to Vorticella is Epistylis
(Figs. 27 and 28).
While most ciliate Infusoria, so far as known, multiply
by self-division, in Vaginicola the process is more like true
gemmation or budding, and is accompanied by a process of
encysting, resulting in the production of a free-swimming
ciliated embryo, the adult Vaginicola being attached. The
Vorticella also becomes encysted, and the nucleus subdivides
until the body becomes filled with monad-like germs, the
result of the simultaneous breaking up of the nucleus. The
Vorticellce, then, pass through a flagellate or monad stage,
from which they pass into the Vorticella condition, when
they multiply by self-division and by budding, the last
generation becoming encysted.
Conjugation is a common occurrence in ciliate Infusoria,
and results in the breaking up of the nucleus of each indi-
vidual into a number of fragments, and the appearance in
each of the individuals of the nucleus and nucleolus (either
single or multiple) which characterize the species.*
* Balbiani believes that the ciliate Infusoria have eggs which are
fertilized by spermatic particles. More recently, however, Eugelmaun,
Biitschli, and Hertwig have denied that conjugation is of a truly sexual
character, and that the striated nucleoli of certain individual Infusoria
are spermatozoa. " Nevertheless," remarks Huxley (Anatomy of In-
40
ZOOLOGY.
CLASS IV. — INFUSORIA.
Flagellate or ciliate (sometime* only ciliate in the early stages) Protozoa,
the body not cha.nging inform, having a definite skin, and often wholly or
partly provided icith cilia; usually free, sometimes stalked or attached ; irith
a mouth-opening and esophagus, and rudiments of digestive, circula-
tory (two or more contractile vesicles), and reproductive organs (nucleus and
nucleolus), but with no distinctively sexual organs.
Order 1. FlageUata. — Rounded, oval, or pear-shaped organisms, usually
exceedingly minute, provided with one or two flagella, with
an oral region, into which particles of food are thrown by
the flagellum ; with a nucleus and contractile vesicles, rarely
stalked, and with a calyx; sometimes aggregated; with a row
of cilia in the highest forms serving as a locomotive appara-
tus ; reproducing by self-division or by segmentation of the
protoplasmic contents of the body, the young being minute
oval bodies, provided with a flagellum (Monas, Heteromita,
Noctiluca, Peridinium).
Order 2. Tentaculifera (Suctoria). — Naked, not ciliated, protozoans,
with long, stiff, retractile arms or tentacles, provided witli
a sucker at the end, Ihe arms hollow, conveying the food
to the digestive cavity ; originating from ciliated young ;
also by self-division throwing off ciliated forms, and under-
going conjugation (Aciueta).
Order 3. Ciliata (True Infusoria). — Body free and covered with cilia
(Paramecinm, Stentor, etc.), or stalked, with the cilia con-
fined to the head end (Vaginioola and Vorticella, etc.); a
well-defined mouth and oesophagus ; a digestive c?vity and
vent ; a large nucleus, and two or more contractile vesicles.
Reproducing by self -division, budding or conjugating, and
producing monad-like young by self-division of the nu-
cleus ; sexuality doubtfully indicated.
The following diagram represents the relative position
of the orders and classes of Protozoa, and in a rude way
their possible genetic relations :
vertebrated Animals, p. 662), " it is still possible that the conjugation
of the Infusoria may be a true sexual process, and that a portion of the
divided endoplastules [striated nucleoli] of each may play the part of
the spermatic corpuscle, the conjugation of which with the nucleus of
the ovum appears, from recent researches, to constitute the essence
of the act of impregnation."
CLASSIFICATION OF PROTOZOA.
41
VIEW OP THE CLASSIFICATION OF THE PROTOZOA.
Ciliata.
(Paramecium.)
Tentaculata.
(Acincta.)
FlageUata.
(Monas.)
INFUSORIA.
GREGARINIDA.
Radiolaria.
(Actinophrys.)
Fomminifera
(Rotalia.)
RHIZOPODA.
MONERA.
Laboratory Work. — None of the Protozoa, except the shells of the
Fomminifera and Radiolaria, can be well preserved after death, and it
is always better to study any animal alive or freshly killed than when
preserved in any sort of fluid. Fresh-water Ama'bce and Monera
should be looked for on the surface of leaves and the stems of sub-
merged plants in ponds, pools, and ditches. Many fresh-water Rhizo-
pods dwell in sphagnum swamps and in damp moss or in shaded pools.
The marine forms may be gathered with a fine towing net, wlipn the
surface of the ocean is calm. The commoner Fomminifera, will be found
on shells and stones at low-water mark or in shallow water, but most
abundantly at greater depths — -I. e., from ten to one hundred fathoms.
On being placed in water they will, after a period of rest, send out
their pseudopodia.
To study their form and development they should be placed in a
drop of water in an animalcule or aquatic box, and kept in this way
for several days and even weeks, the box being examined daily, and
water added if necessary. The shells may be studied by grinding and
slicing into transverse and longitudinal sections. The animals of
Miliola and other forms (Rrttalia, TixtiUaria), on being treated with
diluted chromic acid and stained with carmine, disclosed to Hertwig a
well-marked nucleus. The nucleus may also be deeply stained by
haematoxylin or carmine, and may be clearly demonstrated by acetic
acid, which tends to destroy the surrounding protoplasm. Much in-
genuity, mechanical skill, and patience is required in the study of the
Protozoa, and much yet is to be learned regarding their mode of de-
velopment and their structure.
CHAPTER II.
BRANCH II.— PORIFERA (SPONGES).
General Characters of Sponges. — Although the sponges
were formerly supposed to be compound or social Amoeba?,
and more recently monads, from the striking resemblance
of their epithelial cells to certain monads, and have been
generally regarded as Protozoans, later researches have
shown that they are in reality many-celled animals, and that
for a short period of their life they follow the same develop-
mental path as the higher animals. It was also discovered
that they reproduce by eggs, the latter undergoing segmen-
tation and assuming the condition of a three-layered sac,
the three layers being identical with those of the higher
branches of the animal kingdom, so that the gap between
the Protozoans and sponges is a wide one, and the latter are
more nearly allied to the Hydra, for example, than to any
one-celled animal.
One of the simplest sponges, such as A^etta primordialis
Haeckel, is a spindle or vase-shaped cylinder, attached by its
base, with the cellular soft portion supported by a basket-
work of interlaced needles orspicules of silex or lime. The
cells are arranged in three layers, the innermost (endoderm)
being provided each with a cilium. The spicules, and also
the eggs, are developed in the middle layer (mesoderm).
Moreover, the walls of the body are perforated by multitudes
of small pores (whence the name of the branch, Porifera),
through which the water percolates into the body-cavity,
carrying minute forms of life or food-particles, which are
individually thrown into each cell by the action of the single
cilium thrust out of the collar of the cell, much as in an in-
dividual monad such as Codosiga (Fig. 21). Each cell re-
STRUCTURE OF SPONGES. 43
jects its own waste particle of food, the protoplasm having
been previously absorbed, and the waste from all the epi-
thelial cells is collectively expelled from the single excurrent
orifice (osculum], there being many pores or mouths, and
but a single outlet for the rejectamenta.
Such is the structure of one of the simplest sponges ; the
larger common sponges differ mainly in having a less defi-
nite form, with numerous sacs or digestive cavities or cham-
bers, and numerous excurrent orifices or oscula. It will be
seen, then, that we have in the sponge a three-layered sac,
its cavity rudely foreshadowing the gastrovascular cavity of
the Hydra, but with no genuine mouth, the pores or so-
called mouths simply allowing the sea-water laden with
sponge-food to flow in, inflowing currents being formed by
the ciliary action of the digestive cells, and the excurrent
orifice permitting its exit (Figs. 29, 29«).
In the other sponges such as are figured in this chapter,
the structure is a little more complicated than in the
Ascetta. There is no general body-cavity, with a contin-
uous lining of epithelial cells, but the entire sponge- mass is
permeated by large canals ending in oscula, and there are
innumerable pores (so-called mouths) leading by branching
canals to little pockets or cavities, which are lined with the
flagellate, collared cells developed specially from the inner
cell-layer (endoderm) ; so that the animal is myriad-stom-
ached, so to speak. Moreover, the middle layer of cells is in
many sponges greatly thickened, and nearly the whole
mass, as seen in the common sponge, consists of spicnles or
horny fibres, and protoplasm, through which the excurrent
and incurrent channels meander. Thread cells or lasso-
cells like those hereafter to be described in Hydra have
been detected in the sponge named Reniera.
Let us now follow out the life-history of a sponge. The
sponges are further distinguished from the Protozoa in pro-
ducing eggs and spermatic particles, the eggs being fertilized
before leaving the sponge. The egg after fertilization di-
vides in two, four, eight, sixteen, and more spheres, attain-
ing the mulberry or morula * state (Fig. 30). The result is
* The ter:n«i mo-ruld and gastrula are used in this (TOOK, simply Tor
44
ZOOLOGY.
the formation of a M<i*//i/<r, and then a three-layered sac, cor-
responding to the ri<i*tntld of the higher animals. In this
state (Fig. 30ci) the germ breaks out of the parent sponge into
the sea. Fig. 31 represents the development of the common
little calcareous sporge (Si/con ciliatum}, found between
tide-marks. A indicates the morula with the segmentation-
cavity (c), which afterward
disappears as at B. The
blastula is represented at
C, and consists of ciliat-
ed and non-ciliated large
round cells ; the first series
Fig. 30.— Segmentation of egg of sponge forming a SOl't of arch, With
(Ualisarca).— After Carter.
a hollow in the middle,
around which a large number of very fine brown pigment
corpuscles are collected. The next change of importance is
the disappearance of the cavity, the upper or ciliated half
of the body being much reduced in size. Then the large
round cells of the hinder part are united into a compact
mass, leaving only a single row. The ciliated cells are
gradually withdrawn into the
body-cavity. Fig. 31, D, shows
the gastrula condition. At this
period also the larva becomes ses-
sile, and now begins the formation
of the sponge-spicules, which de-
velop from the non-ciliated round
cells. MetschnikofE calls atten-
tion to the fact that at this early
stage the Sycon passes through a
phase which is persistent in the Fig.30o._BlMtulaofa8pollge((Sl,.
genus Sycyssa. The layer of cil- <»w<?m rapAan«*).-Af ter schuize.
iated cells are gradually withdrawn into the body-cavity,
until a small opening is left surrounded with a circle of
cilia. These cilia finally disappear, a few more spicules
grow out, and meanwhile the opening disappears. In the
gastrula (represented at D] a considerable body-cavity ap-
ronvenience to avoid circumlocution. It may be that these conditions
wi.l be found to be essentially modified in different groups of animals.
OS
FU -Jit.— Diagram of sponge. />, Fig-. 29a.— A longitudinal section through a
one of the numerous pores or mouths; simple calcareous sponge, showing the simple
c. a ci Mated chamber or pocket; os, central cavity; b, showing a single osculuru at
osculum. the top, and the many mouths over the surface.
g'c
Fig. 306.— Development of a sponge (Sycon raphanus). A, ripe egg; B, stage with
foursegmentatiou-cells; C, morula stage, with sixteen cells; D, blastosphere(blastula),
with large dark granular cells (</c) at the open pole; E. free-swimming blastula, one
half of the body (endodermal) being formed of long ciliated cells, the other (ectoder-
mal) of large granular cells. All highly magnified.— After Schultze.
[To face page 44. J
DEVELOPMENT OF SPONGES.
45
pears which may be seen through the body-walls. At this
time the germ consists of two layers, the inner layer of cili-
ated cells (endoderm) forming a closed sac, enveloped in the
spiculiferous layer. Such are the observations of Metschni-
koff on the development of Sycon. According to the ob-
servations of Barrois, the larva or gastrula fixes itself by what
are destined to be the ectodermal cells, and which are the
round non-ciliated cells forming the posterior end (Fig. 31,
C) of the free-swimming bhistula. About this time the
mesoderm separates from the endoderm, either before or
just after the gastrula becomes stationary, according to the
group to which it belongs.
When the young sponge becomes stationary it does not
differ from the gastrula, except that it becomes more or less
Fig. 31.— Development of a sponge (Sycon clliatum).— After Metschnikoff.
irregular in form. Then appear the food or digestive cavi-
ties in the endoderm, in Sycandra becoming radiating tubes
lined with ciliated, collared, monad-like cells ; or in Lencon
and Halichondria, and their allies, forming scattered pock-
ets, called " funpullaceous sacs. " Inmost sponges (except
some calcareous species) there is no general body-cavity in
the gastrula, nor in the young after the larva becomes sta-
tionary, according to Barrois. After the formation of the
ampullaceous sacs the pores open through the mesoderm
and connect the sacs and ciliated channels, as the case may
46 ZOOLOGY.
be, with the outer world. These pores may open and then
be permanently closed, new ones opening elsewhere. The
osculum bursts open by the accumulation of water between
the two layers in the same manner as the pores. Finally,
in certain sponges the horny fibres grow out from the outer
cell-layer and extend inward, surrounding the spicules, the
latter developing from the middle cell-layer.
It appears, also, that all sponge embryos form a two and
afterward three-layered sac (gastrula), in which in the sim-
plest sponges there is a primitive body-cavity and a prim-
itive mouth, while in the higher calcareous sponges and in
the silicious forms the body - cavity is only temporarily
open, being afterward filled up by the interior ciliated
cells, and thus forming a compact mass.
In the sponges, also, the larva or free-swimming young
is a three-layered sac, which is either hollow or, more com-
monly, solid, and may attach itself at the end of its free-
swimming life by one end to some fixed object. The body-
cavity may persist in the simpler forms through life, though
in most sponges there is no genuine digestive cavity, but a
large series of minute digestive sacs communicating by canals
with the large ones leading to the oscula. The more or less
regular spherical form of the young of most sponges becomes
lost as they grow ; they become irregular in form, encrust-
ing rocks, and their development retrogrades rather than
advances.
In the fresh-water Sponyilla there is a special provision for
the maintenance of the species. In autumn are formed the
so-called " seed," being capsules in which are enclosed eggs
which in the spring develop young sponges. This cyst or
capsule may be compared to the biids or winter eggs of the
Polyzoa or of the water-flea (DapTinid).
From the members of the next branch, the sponges differ
in the great irregularity of their form, the lack of a definite
digestive cavity and of tentacles.
Order 1. Calcispongia. — The sponges may conveniently
be divided into two orders. Those belonging to the first
secrete spicules of lime, and there are no digestive or ampul-
laceous sacs, but the minute canals are lined with ciliated cells.
SPONGES.
The calcareous sponges are few in number and are repre-
sented by a delicate little white sponge called Si/con ci/in-
tum Johnston, very common on sea-weeds between tide-
marks.
Order 2. Carneospongice. — In this group the spicules
may either be fibrous and horny or silicious. The middle
Fig. 32.— Axinella polypoldei.
Fig. W.—Siylocordylaboreale,
natural size.— After Loven.
cell-layer is very thick, the endoderm being restricted to the
numerous digestive cavities or so-called ampullaceous sacs.
The fresh-water sponge (Spongilla) occurs everywhere
on submerged sticks and stones in running or nearly stag-
nant water, usually branching. With the exception of
Spongilla and another form, Siphydora echinoides Clark,
which grows as large as one's fist in northern ponds and
streams, all sponges are marine. One of the commonest
48
ZOOLOGY.
sponges north of New York is Clialinula oculata (Bower-
bank), which grows in long slender branches on the piles of
wharves and bridges. Allied to it is Axinella (Fig. 32, A.
polypoides).
Allied to Tethea, which is sessile, is a deep-sea form grow-
ing on a long stalk, i.e., Stylocordyla boreale (Fig. 33). At
the depth of 100 fathoms in the Gull' of Maine occurs a
Fig. m.—Pheroiifma Anna', half natural size, with stellate and anchor-like spicules,
much enlarged. — After Leidy.
similar species (S. longissiinum Sars). Fig. 34 represents
a fine silicious sponge (Pheronema Annce Leidy) from the
West Indies. The most beautiful of all silicious sponges is
the Venus' flower-basket (Euplectellum aspergillum), which
lives anchored in the mud at the depth of about 10 fathoms,
near the Philippine Islands.
COMMERCIAL SPONGES. 49
The Cliona bores into shells, causing them to disinte-
grate. For example, Cliona sulphured of Verrill has been
found by him boring into various shells, such as the oyster,
mussel, and scallop ; it also spreads out on all sides, envelop-
ing and dissolving the entire shell. It has even been found
to penetrate one or two inches into hard statuary marble.
Of the marketable sponges there are six species, with nu-
merous varieties. They are available for our use from being
simply fibrous, having no silicious spicules. The Mediter-
ranean sponges are the best, being the softest; those of the
Red Sea are next in quality, while our West Indian species
are coarser and less durable. Our glove-sponge (Spongia
tubulifera Duch. and Mich.) corresponds to Spongia Adriat-
ica Schmidt, which is the Turkey cup-sponge and Levant
toilet sponge of the Mediterranean. Spongia gossypina
Duch. and Mich, the wool sponge of Florida and the Baha-
mas, corresponds to S. equina Schmidt, the horse or bath
sponge of the Mediterranean.
BRANCH II.— PORIFERA.
The sponges are many-celled animals, witli three cell-layers, without a
true digestive cavity, supported usually by calcareous or silicious spicules,
the body-mass permeated by ciliated passages, or containing minute cham-
bers lined by ciliated, collared, monad-like cells. No true month-opening,
but usually an irregular system of inhalent pores opening into the cell-lined
chambers or passages through which the food is introduced in currents of
sea-water, the waste particles passing out of the body by a single, but more
usually, many cloacal openings (oscula). Sponges are hermaphroditic, mul-
tiplying by fertilized eggs, the germ passing through a morula and a gastrula
stage. (The characters of the Class the same as those of the Branch.)
Order 1. Calcispongia. Animal supported by a framework of calcare-
ous spicules, disposed in lines or columns at right angles to
the walls ; with cell-lined radiating canals. (Sycon.)
Order 2. Carneospongi®. Mesoderm exceedingly thick ; the ciliated
cells restricted to cell -lined chambers. Either no solid
framework, as in Halisarca, or usually a well-developed
fibrous or silicious framework. (Spongilla, Spongia, Hya-
lonema, Euplectella.)
50 ZUOLVUY.
VIEW OF THE CLASSIFICATION OF THE PORIFERA.
CameospongicB.
(SpongmJ
CalcisponguB.
(Sycou.)
PoUIFERA.
Laboratory Work. — Sponges are difficult to preserve aliye in aquaria
for stud)'. Fine microscopic sections of the living sponge may be made
with the razor or the microtome, and the tissues and eggs as well as the
young be studied, though, from their minuteness, the study of the
young is very difficult. The ciliated young of Sycon. ciliattnn may be
obtained in the spring and summer by picking a portion of the sponge
to pieces and tearing out small fragments with fine needles, until por-
tions are small enough to be examined under high powers of the micro-
scope. Researches on the finer structure and mode of growth of the
sponge are difficult, and require much skill and long training in his-
tological methods. The gross structure of sponges may be studied 'by
cross and longitudinal sections made with a razor or knife.
LITERATURE.
Haeckel. Die Kalkschwamme 3 vols. 1872.
Schmidt. Die Spongieufaunit des Atlanlisclien Gebietes. 1870.
Sclmltee. Uutersuchungeu ueber den Ban und dei Eutwicklunir
der Spongieu. (Zeitsclirift fur wissens. Zoologie, Bd. 25-3."). 1816-
1881.
Hyatt. Revision of the North American Poriferae. (Memoirs Bos-
ton Soc. Nat. Hist., ii. 1875-1877.)
Vosmaer. Porif'era, in Broun's Klassen und Orduungen des Thier-
reichs. 1882. Also the treatises of Bowerbauk, Clark, Lendenfeld,
etc.
CHAPTER III.
BRANCH III.— CCELENTERATA (HYDROIDS, JELLY-
FISHES AND POLYPS).
General Characters of Coelenterates.— In this branch,
which is represented by animals like the Hydra (Fig. 36) and
Tubularia (Fig. 35), the body consists
of two cell-layers, surrounding a
definite, single, digestive cavity, the
mouth of the cavity being surrounded ct
by a circle of tentacles, which are in
polyps hollow and connect with the
stomach. The latter, however, is only
partly differentiated or set apart from
the body, hence the name Ccelenterata
(Greek, KozAo?, hollow, and fVr^poF,
digestive tract). From the stomach
often radiate water-vascular canals, no
blood-system yet appearing thus far in
the animal kingdom, the products of
digestion reaching the tissues from
the smaller branches of the primary
water-vascular canals. The nervous
system is either absent, or in different
grades of development, from the iso-
lated nervo-muscular cells of Hydra
and the scattered nerve-cells of an
Actinia, to the continuous ganglion-
ated nervous ring of the minute
jelly-fish such as Sarsia. These animals display a striking
amount of radial symmetry, the organs and body being dis-
posed in a radiate manner around a central vertical axis, in
Fig. 35.— A Hydroid, Tubu-
laria. m, medusa buds ; ct,
tentacles ; p, proboHcis. —
From Tenney'e Zoology.
52 ZOOLOG Y.
part formed by the digestive tract. The Coelenterata pre-
sent striking examples of self-division, gemmation, and
alternate generations, and very great extremes in degree of
complexity of structure.
The different groups have a high geological antiquity;
the species of Hydroid and coral-polyps serving as time-
marks to measure off geological periods.
CLASS I. — HYDROZOA (Hydroids and Acalephs.)
General Characters of Hydrozoa.— An excellent idea of
the general structure of the Hydrozoa may be obtained from
a study of Hydra, the type or example of the whole class, all
the other forms being but a modification and elaboration of
this simple type. The characters of the class as a whole are
based on what is found to constitute the structure of
Hydra.
Order 1. Hydroidea. — The animal next higher in struc-
ture than the sponge is the curious Protoliydra discovered
by Greef among diatoms and sea- weeds at Ostend. It is re-
garded by Greef as the marine ancestral form of the Ccelen-
terates. It is the simplest Ccelenterate yet discovered. As
the form of the fresh-water Hydra is familiar, Proluhydra
mav be best described as being similar to that, except that
it is entirely wanting in tentacles. It is made up of two
layers (an ectoderm and endoderm, no mesoderm having yet
been discovered), with a mouth and stomach (gastro-vascular
cavity).
A more complicated form is the fresh-water Hydra, which
is commonly found on the under side of the leaves of aquatic
plants. There are two varieties of Hydra vulgar is appar-
ently common to the fresh waters of the old and new world ;
they are Hydra viridis and fusca. The somewhat club-
shaped body consists of two layers, the inner (endoderm)
lining the general cavity of the body, which serves both as
mouth and stomach, as well as for the circulation of the
nutritive fluid, and is called the gastro-vascular cavity.
The mouth is surrounded with from fi\v to eight tentacles,
STRUCTURE OF HYDRA, 53
which arc prolongations of the body-wall, and are hollow,
communicating with the body-cavity.
Such is the general structure of the Hydra. In the
ectoderm are situated the lasso-cells or nettling organs, be-
ing minute barbed filaments coiled up in a cell-wall, which
may be thrown out so as to paralyze the animals serving as
food. While the endoderm forms a simple cell-layer, the
outer layer (ectoderm) is more complex, as just within an
external simple layer of large cells is a multitude of smaller
cells, some of them being thread or lasso-cells, while still
within are fine muscular librillai which form a continuous
layer. The largo cells first named end in fil>re-like pro-
cesses, which alone possess contractility, and are thought by
Kleinenberg to be motor-nerve endings. But these cells,
once termed "nerve-muscle cells/' do not combine the func-
tions of muscle and nerve, The little cavities between
the large endodermal cells and the muscular layer (meso-
derm?) which lies next to the endoderm are filled with
small cells and lasso-cells, forming what Kleinenberg calls
the interstitial tissue. From this tissue are developed the
eggs and sperm-cells.
The body being but slightly differentiated or set apart
into special organs, the Hydra, like other low creatures, is
capable to a wonderful degree of reproducing itself when
artificially dissected. Trembley, in 1744, described in his
famous work how he not only cut Hydras in two, but on
slicing them across into thin rings, found that from each
ring grew out a crown of tentacles; he split them into lon-
gitudinal strips, each portion becoming eventually a well-
shaped Hydra, and finally he turned them inside out, and
in a few days the evaginated Hydra swallowed piece's of
.meat, though its old stomach-lining had now become its
skin. We shall see that not only many Hydroids, Aca-
lephs, some Echinoderms, and many worms, may reproduce
lost parts and suffer artificial dissection, but that self-
division is a normal though unusual mode of reproduction
among these animals, as well as in the Protozoa, which
may also be made ifc<jfcreproduce by artificial division, as
Ehrenberg cut an in.u'sorian into several pieces, each frag-
ment becoming a perfect individual.
ZOOLOGY.
The process of budding is but a modification of that in-
volved in natural self-division, and it is carried on to a great
extent in Hydra, a much larger number of individuals being
produced in this way than from eggs. Our figure (3C)
shows two individuals budding out from the parent Hydra ;
the smaller bud («) is
a simple bulging out
of the body-walls, the
bud enveloping a por-
tion of the stomach,
until it becomes con-
stricted and drops off,
the tentacles mean-
while budding out
from the distal end,
and a mouth -opening
arising between them,
as at c. Budding in
the Hydra, the Acti-
nia, and, in fact, all
the lower animals, is
simply due to an in-
crease in the growth
and multiplication of
cells at a special point
on the outside of the
body, while the asex-
ual mode of reproduc-
tion in the Ajrfiis and
a few other insects
results from the mul-
tiplication of cells at
Fig. 36 .— Hi/flra fnsca, with two yomig (a c) bud- ,. , . , ,,-,
ding from it; 'b, the- base; «, the tligi^nvu cavity; t, a particular point (tile
ovary) in the inside of
the body. Thus Parflipnorjenesis or Ayamocjencsis is analo-
gous to the ordinary mode of budding. Eh ren berg first showed
that the Hydra reproduces by fertilized eggs. Kleinenberg
describes the testis, which is lodged in the ectoderm, and
which develops tailed spermatozoa Ijke those of the higher
DEVELOPMENT OF HYDRA. 55
animals. They arise, as in other higher animals, from a
self-division of the nuclei of the testis-cells. There is a true
ovary formed in the same interstitial tissue of the ectoderm,
consisting of a group of cells, which, Kleinenberg states,
differ entirely in their mode of formation from the ovaries
(gonophores) of the marine hydroids, which are genuine
buds.
It thus seems that Hydra is monoecious or hermaphro-
dite— i.e., the sexes are not distinct. The egg of Hydra
originates from the central cell of the ovary.
There is a true segmentation of the egg. The young
Hydra thus passes through a true morula stage-. There
is an outer layer of prismatic cells, forming the surface of
the germ, and surrounding the inner mass of polygonal
cells. At first none of these cells are nucleated, but after-
ward nuclei appear, and it is an important fact that these
nuclei do not arise from any pre-existent egg-nucleus.
The next step is the formation of a true chitinous shell,
enveloping the germ or embryo. After this, Kleinenberg
asserts that the cells of the germ become fused together,
and that the germ is like an unsegmented egg, being a
single continuous mass of protoplasm.
The remaining history of Hydra is soon told. In this
protoplasmic germ-mass there is formed a small excentric
cavity ; this is the beginning of the body-cavity, which
finally forms a closed sac. After several weeks the germ
bursts the hard shell and escapes into the surrounding wa-
ter, but is still surrounded by a thin inner shell. After this
a clear superficial zone appears, and a darker one beneath,
which is the first indication of the splitting of the germ into
the two, afterward three, definitive germ-lamellse, common
to all animals except the one -celled Protozoa.
The embryo soon stretches itself out, a star-shaped cleft
appearing, which forms the mouth. The tentacles next ap-
pear. The animal now bursts open the thin inner shell,
and the young Hydra appears much like its parent form.
There is, then, no metamorphosis in the Hydra ; no cili-
ated planula. as in many other Hydroids. The adult form
is thus reached by continuous growth.
56
ZOOLOGY.
It will be seen, to anticipate somewhat, that the Hydra,
exactly as in the vertebrates, including man, arises from an
egg developed from a true ovary, which, after fertilization,
passes through a morula stage ; that the germ consists at
first of two germinal layers, while from the outer layer, as
probably in the vertebrates, an intermediate or nervo-mus-
cular layer is formed, which Allman thinks is the homologue
of the middle germ-lamella of the vertebrates (mesoderm)
supposed to have originally split off from the ectoderm.
In all the other Hydroids the sexes are separate, and we
for the first time in the animal kingdom meet with two
sorts of individuals — i.e., males and females.
- ^/
Fig. 37.— Colony of Hydracfinia tchinata on a shell tenanted oy a hermit crab,
natural size.— From Brehm's Thierleben.
The simplest form next to Hydra is Hydractima, in
which the individual is differentiated into three sets of
zooids — i.e.. a, hydra-like, sterile or nutritive zooids ; b and
c, the reproductive zooids, one male and the other female,
both being much alike externally, having below the short
rudimentary tentacles several spherical sacs, which pro-
duce either male or female medusae. These medusa-buds
(gonophores) are in structure like the free medusae of Co-
ryne. The marine Hydroids, then, are usually sexually dis-
tinct, growing by colonies, which are either male or female.
HYDROID CORALS.
57
Hydractinia echinafa (Fig. 37) forms masses (each called a
hydrophyton) encrusting shells.
In Claim the reproductive buds remain permanently at-
tached. It grows in pink masses on Fucoids, about half an
inch high, and is very common on our shores. It is repre-
sented in fresh water by CordylopTiora lacustris Allman,
which lives attached to rocks and plants in Europe and this
country.
Here comes in the group of Hydroids represented by
Millepora and Stylaster, which were formerly considered to
be Anthozoan corals. By the researches of L. Agussiz in
1859, and H. M. Moseley
in 1876, Millepora, which
had been confounded
with the coral polyps,
has been proved to be a
Hydroid allied, as Agas-
siz stated, to Hydracti-
nia. Like that Hydroid,
a calcareous
mass, but of
much greater extent, a
considerable proportion
of the coral in the Flori-
da reefs being formed
by the Millepora. Our
American species is Mil-
lepora alcicornis Linn.,
while our description is taken from Moseley's account of
Millepora -nodosa Esper. (Fig. 38). Its generic name is de-
rived from the numerous pores or calicles dotting its surface
and arranged in irregular circular groups, consisting of a
central calicle, or cup-like hollow, with from five to eight
smaller calicles arranged around it. The mass of the coral,
or hydrophyton, consists of fibres (canals or tubes) of lime,
forming a spongy mass, traversed in all directions by tor-
tuous spaces which " form regular branching systems with
main trunks, giving off numerous branches, from which
arise secondary branches, and from these again smaller
it forms
encrusting
Fig. ^.—Millepora nodo»a. a, nutritive
zooid ; b. tentaculated zooid : c. lasso-cell ; d,
the name roiled up in its cell ; e, a third form.
58 ZOOLOGY.
ramifications. The whole ctinal system is connected to-
gether by a freely anastomosing mesh-work of smaller ves-
sels, and communicates freely by numerous offsets with the
cavities of the calicles. " As the animals increase in num-
bers and die, the coral stock increases in size, the layer con-
taining the living animals forming a thin film only, the
bottom of the little cups or pores forming a table or plat-
form, whence the term Tdbulata, originally applied to this
group, the old calicles being divided by a series of trans-
verse plates or laminae, separating them into series of cham-
bers. Moseley shows that the corallum of Millepora is dis-
tinguished from all other coralla by its systems of canals
branching in an arborescent manner, while the tabulate
structure occurs in certain Alcyonaria, Zocuitharia, and in
other Hydroida ; hence the group Tabulata, as previously
stated by Verrill, is an artificial one.
The animals of the Millepora are of two kinds ; those in-
habiting the central cup or pore are short, thick zooids,
with a mouth and four tentacles, and only half a milli-
metre in height ; those in the smaller pores are longer and
slenderer, about one and a half millimetres in height, with
from usually five to twenty tentacles, situated at irregular in-
tervals from the base to the summit of the body. The body
cavities of the zooids end in blind saes at the bottom of the
cup, but are continuous beyond with the canals of the hy-
drophyton, the latter being defined by Allman as forming
in the Hydroids " the common basis by which the several
zooids of the colony are kept in union with one another."
As we know nothing of the mode of reproduction of Mille-
pora, we must leave it for the present near Htjdr actinia, to
which the adult animals are nearest related. Moseley also-
discovered t\\&iStylaster, a beautiful pink coral which grows
at Tahiti, with the Millepora, is in reality a Ilydroid, and
not a true coral polyp, as has always been supposed. Thar,
finally, Millepora is a true Hydroid is proved, Moseley thinks,
by the peculiar structure of the hydrophyton, the forms of
the zooids, the absence of all trace of mesenteries, the ap-
parent septa present in the tentacles, and by the presence
of thread-cells of the form peculiar to the Hydrozoa. The
DEVELOPMENT OF HYDKOIDS.
59
communicating
gas-
living Millepora, unless handled with great care, severely
stings the hand of the collector.
We now come to Hydroids which throw off a free naked-
eyed medusa from the hydrarium (Fig.
39). From the centre of these free
bell-shaped, minute jelly-fishes depends
a hollow, open sac called the manu-
hr'nnn, the cavity of which (stomach)
opens into usually four canals, which
radiate from the hollow or stomach in
the centre of the disk and communi-
cate with a canal following the margin
of the disk. This is
the water-vascular sys-
tem,
directly with the
tro-vascular cavity, or
stomach. Four tenta-
cles hang from the
disk, and simple eye-
spots and otolitlnc sacs (simple ears) are iisu-
ally present and situated at regular inter-
vals around the edge of the disk. Such is
the typical form of all the free-swimming
Hydroids. They are said, in a few cases,
to possess a well-developed continuous ner-
vous system, consisting of a nervous ring
around the disk (Romanes). They are bi-
sexual, the ovaries or spermanes being de-
veloped on the radiating canals, the embryo
escaping into the surrounding water by rup-
turing the walls of the ovary.
The young is at first oval, ciliated all
over the surface of the body, and is called a
planula. The planula, as in Melicertutn, a Fig. 40.— Fren Meda-
genus allied to Campanularia, and a type
of most marine Hydroids, at first spherical, becomes pear-
shaped, and after SAvimming about for a time attaches itseli
to some object. It then elongates, a horny sheath (peri-
Fig. 39. — Polypite of
Corynemircbilis, with a bud
below «. and medusa-bud
(gouophore) at a. Much eu-
larged. — After Agat^iz.
ZOOLOGY.
sarc] forms around it, tentacles arise around the mouth,
finally the stem branches, new Hydroids arise, until a hy-
droid community (consisting of trophosomes and yonosomes)
is formed, and in the following spring medusa-buds (gono-
phores) arise, which become free (medusoids), and thus the
reproductive cycle is completed. The developmental his-
tory of this llydroid is a good example of what is called
; alternation of generations."
Budding occurs in the medusa of tiaraia prolifvra, in
Hybocodon prultfer and Dysnwrphosa fulatiram;. Mul-
tiplication by fission has been observed in the medusa of
Stomobrachium mirabile. The pendent stomach was seen
by Kolliker to divide in two, becoming doubled, which act
was followed by a vertical division of the umbrella, separat-
ing the animal into two independent halves. These again
subdivided, and Kolliker thinks this process went on still
further. Haeckel has found in cutting off a portion of the
edges of the umbrella of certain Thaumantice, that the frag-
ment in a few days became a complete medusa.
In the Tubularian Hydroids ( Tubularia, Hybocodon, Co-
rymorplia, Monocaulus, etc., Fig. 41),
the mode of reproduction is peculiar.
From the medusa-buds (sporosac) is set
free au embryo (actinula), which swims
about or creeps on its tentacles, mouth
downward. It then attaches itself by a
disk-like expansion of the posterior end,
which forms a stem until the original
Tubularia form is attained.
A gigantic Monocaulus having sessile
ovisacs, measuring seven feet four inches
in height, and provided with a crown of
tentacles nine inches across from tip to
tip of the expanded, non-retractile ten-
tacles, was dredged by the Challenger
Expedition at the depth of four miles.
Allman suggests that such a deep-sea Hydroid could not, on
account of the darkness and pressure of the water at such a
great depth, produce free-swimming medusae. In Tiaropsis
'12. 41. — Monocaulus p?n-
dulun.— After Agassi z.
GRAPTOLITES.
Gl
there is no trace of a nervous system such as exists in
Sarsia, where nerve-fibres extend around the margin and
along the radial tubes (Romanes).
In the groups of Campanularice, represented by Plumu-
laria, Sertularia, Zygodactyla, Dynamena, and Campanu-
laria, the ectoderm is protected by a horny or chitinous
sheath (perisarc) enveloping the zooids. The Hydroids re-
tract, when disturbed, into small cells (hydrotheose), arranged
in opposite rows on
the stalk as in Sertu-
laria (Fig. 42), or
singly at the ends of
the stalks, as in Cam-
panularia, while the
sheaths (gonotlieccB)
protecting the medu-
sa-buds are distin-
guished by their
much larger size and
cup-shaped form.
The Sertularians
abound on sea-weeds,
and may be recogniz-
ed from their resem-
blance to mosses.
They are among the
most common objects
of the seaside. The
medusae of these and ^ ^_Sertularia abietina of Europe. a,
many Other II vdroids ralsize; 6, magnified, showing the hydrarium, with
•' the cells. — From Macallister.
can be collected by a
to wing-net, and emptied into a jar, where they can be de-
tected by the naked eye after a little practice.
Graptolites.— More nearly allied perhaps to the Sertularian
Hydroids than any other known animals are the Graptolites
(Fig. 43), which were most abundant in the Lower Silurian
period, and lingered as late as the Clinton epoch of the Upper
Silurian. In Graptolithus Loyani the hydroid colony (hy-
drosome) is a long narrow blade, with a row of cells on one
ZOOLOG Y.
B
side ; in G. pristis the hydrosome is broader, more lanceo-
late, and the sharp, tooth-like cells are arranged on both
sides of a median stem. In Phyllograptus typus the hy-
drosome is broad and oval, leaf-like, the serrations of the
leaf marking off the cells, which are apparently supported
on a central axis. The group also has some affinities to the
Polyzoa, and is probably a generalized or synthetic type of
animals.
Order 2. Discophora. — We now come to medusae which
differ from the Hydromedusae in
developing directly from eggs ;
in having usually no velum ; with
branching gastro- vascular canals,
and covered sense-organs. They
intergrade, however, with the
Hydroidea by the members of the
group or sub-order Tracliymedu-
sce, represented by the genera
^Egineta, Geryonia, etc. These
are small jelly-fishes, with often
a remarkably long proboscis
(manubrium), as in Geryonia,
and with either four single radi-
ating canals, or, in addition, as
in Geryonia, a number of smaller
canals on the edge of the disk ;
or, as in a still more complicated
form, Cltarybdcea, the radiating
canals are branched, thus con-
necting this group with the true
covered-eyed Acalephs, such as Aurelia.
0. and R. Hertwig have fully confirmed Haeckel's discov-
ery of the nature of the nervous system in the Geryonidce.
They find that the nervous system is developed in the ecto-
derm and consists of two " ring-nerves" around the edge
of the disk, formed of two filaments, one lying on the upper,
the other on the under side of the velum, immediately at its
insertion. From this double nervous ring filaments are sent
off to the ganglia near the sense-organs. This sort of a
A
D
Fig. 4S.—Monoffraptutt priodon.
C, front view. — After Nicholson.
DEVELOPMENT OF JELLY-FISHES. 63
nervous system is present in the JEquoridcB and
but is most distinct and best developed in the Geryonidce
(Glossorodon and Carmarina).
The Hertwigs have also observed in these Trachynemidaa
organs of taste, consisting of groups of long stiff hairs at
the base of the tentacles. They have been observed in
RJiopalonema velatum, Aylaura nemistoma, and in Cunina,
where the hairs are shorter.
The eggs, in developing, after total segmentation (morula
stair) pass into a ciliated plannla state as in Aurelia, there
being at first apparently no primitive gastric cavity ; the
body of the embryo or plannla remains spherical, as in Gery-
onia, there being a slight metamorphosis ; or, as in Poly-
xenia and jffiginopsis, where there is a decided metamor-
phosis, the spherical ciliated plannla greatly lengthens out
on each side, the body becoming boomerang-shaped, each
end of the boomerang becoming an arm or tentacle. Then
it becomes a gastrula, a central cavity and mouth appear-
ing. At right angles to the two primitive arms bud out
two others, and finally others appear on the lower edge of
the umbrella, and after slight changes the adult form is as-
sumed. Cunina is at first spherical, then, a single arm
developing, it becomes club-shaped ; finally, the full num-
ber of arms grow out, and the mature form results. It ap-
pears, then, that in the mode of development from eggs,
without passing through a hydra-like condition, and in the
structure of the body, the Trachymedusce connect the cov-
ered-eyed medusas with the naked-eyed or Hydroidea. The
American forms are found from Newport southward. A
probably exotic fresh-water form (Limnocodiuni) lives in a
tank (90° F.) at London. Cunina has been found by
Haeckel growing on the columella of Geryonia, and
McCrady has found that our native Cunina is parasitic on
Turritopsia, a hydroid medusa.
The Lucernarim, or Calycozoa, which, according to Clark,
form an order of Acalephs, are, with Huxley, regarded as
a suborder of Discopliora. With essentially the structure
of the Aurelia and allies. Luoernaria differs in having the
power of attaching itself by a sucker on the smaller end of
its body to sea-weeds, but can detach itself at will and sv/im
64 ZOOLOGY.
about like the Aurelia by alternate contractions and expan-
sions of the umbrella. We will now enter into a more com-
plete account, of this group based on Clark's characteriza-
tion. The disk is more or less octagonal or circular, um-
brella, funnel or urn-shaped, the end opposite the mouth
ending in a pedicel, by which it is attached temporarily to
sea- weeds. The mouth is square, and between the ectoderm
and endoderm is a jelly-like layer constituting the musculo-
gelatiniform layer (mesoderm) much as in Aurelia. This
layer extends into the tentacles and marginal anchors, as
well as into the pedicel. The cavity of the disk is divided into
four quadrant chambers, separated by as many partitions,
which extend from the mouth into the lobes nearly to the
margin between the tentacles. The latter are arranged in
eight groups or tufts just within the margin of the disk, at
eight points, which alternate with the four partitions and
the four corners of the mouth. The tentacles are hollow,
opening into the radial canals of the general cavity of the
body, and end in a globular or spheroidal expansion, serv-
ing as an organ of touch or prehension. In some forms, as
Halidijstus auricula Clark, marginal anchors are situated
at eight points, exactly opposite the four partitions and the
four corners of the mouth ; they are originally tentaculiform,
but in adult life form organs by which they adhere to or
pull themselves from place to place. The sexes are distinct,
the reproductive glands having the same position in each
sex. Nothing is absolutely known of the mode of growth
of these animals, but development is supposed to be direct.
Our common Lucernarian is Haliclystus auricula Clark.
Its umbrella-shaped disk is an inch in diameter ; including
the tentacles, an inch and a half ; the pedicel half an inch
long. It ranges from Cape Cod to Greenland and south-
ward to the coast of England, and may be found on eel-
grass between tide-marks.
According to A. Meyer, the end of the stalk when cut off
produced a new disk, and even pieces cut off between them
became complete LucernaricB, evincing the extraordinary
powers of reproduction in these interesting jelly-fish.
Coming now to the true Discophora, jelly-fish, sea-
NERVOUS SYSTEM OF JELLY-FISHES. 05
nettles, sun-fish or Acalephs, of which there fire about
nme known species on the Eastern coast of the United
States, we may study as the type of the suborder the
common Aurelia flitcidula Peron and Lesueur of our
coast, which is closely allied to the Aurelia aurita of the
European shores. It grows to the diameter of from eight
to ten inches, becoming fully mature in August, the young
appearing late in April in Massachusetts Bay, being then
not quite an inch in diameter. The mature ones may be
easily captured from a boat or from wharves. On a super-
ficial examination, as well as by cutting the animal in halves
and making several transverse sections with a knife, the lead-
ing points in its structure may be ascertained. Its tough,
jelly-like disk is moderately convex and evenly curved, while
four thick oral lobes depend from between the four large geni-
tal pouches; the oral lobes unite below, forming a square
mouth-opening, the edge of which is minutely fringed to the
end of tbe tentacles. On the fringed margin are eight eyes,
each covered by a lobule and situated in a peduncle, and
occupying as many slight indentations, dividing the disk
into eight slightly marked lobes. The subdivisions of the
water-vascular canals or tubes are very numerous and anas-
tomose at the margin of the disk, one of them being in
direct communication with each eye-peduncle. When in
motion the disk contracts and expands rhythmically, on the
average twelve or fifteen times a minute ; on the approach
of danger they sink below the surface.
While a distinct nervous system has not been discovered
in Aurelia, Romanes suggests that there are primitive ncrvo-
muscular cells, such as those shown by Kleinenberg to exist
in Hydra, and he concludes, after a series of experiments
on Aurelia aurita, that the whole contractile sheet of the
bell presents not merely the protoplasmic qualities of ex-
citability and contractility, but also the essentially nervous
quality of conducting stimuli to a distance irrespective of
the passage of a contractile wave. The later researches of
0. and R. Hertwig show that the nervous system of
Acalephae (Acraspedota or covered-eyed Medusae) is much
more primitive than in the naked-eyed or craspedote forms.
66
/.OOLOGY.
sucli as the medusae of the Hydroids and the Tracliy-
nemidce. In tlie European Nansithoe albida and Pelugia
noctiluca no nerve-ring is present, for this is impossible
owing to their deeply indented disks. There are instead eight
Fig. 44.— Gastrulaof an Anre-
lia-like Medusa, a. primitive
mouth: b, gastro-vascular cavity;
c. ectoderm ; <l. cmloderm.—
After Metf-chuikoff.
Fig. 45.— Scyj)histoma of Aurelia
flavidula, at different ages; magui-
lied. — After Agassis.
separate nerve-tracts which unite with the sense-organs in a
special elevation of the edge of the disk, forming so-called
sense-bearers, which alternate with the eight tentacles.
Aurelia aurila has a similar disconnected nerve system.*
Eimer confirms these discoveries, and states that the ner
vous system in these Hydrozoa arises from the ectoderm.
Fig. 46.— StroMla of Au-
rflia fiaviduki. — After
Agasaiz.
Fig. 47. — Kphyra or
carliol t'i'i'f condition of
Aurelia. — After Agas-
Biz.
The Aurelia flavidula spawns in late summer, the females
being distinguishable by their yellowish ovaries, the male
glands being roseate, while the tentacles of the females are
* Ji-naische Zeitschrift, 1877, p. 355.
DEVELOPMENT OF JELLY- FISHES.
67
shorter and thicker than in the males. The eggs pass out
of the mouth into the water along the channeled arms, and
in October the ciliated gastrula becomes pear-shaped and
attaches itself to rocks, dead shells, or sea- weeds, and then
assumes a Hydra form with often twenty-four very long
tentacles. This stage was originally described as a distinct
animal under the name of Scypliistoma. In this Scyphis-
toma stage (Fig. 45) it remains about eighteen months.
Toward the end of this period the body increases in size
and divides into a series of cup-shaped disks. These saucer-
like disks are scalloped on the upturned edge, tentacles bud
Fig. 48. — 4.urelia flavidula. — After Agassi/.
out, and the animal assumes the Strobila stage (Fig. 46).
Finally, the disks separate, the upper one becomes detached
and with the other disks swims away in the Epliyra form
(Fig. 47), when about a fifth of an inch in diameter, and
toward the middle or end of summer becomes an adult
Aurelia (Fig. 48).
Though the Aurelia has lasso-cells it is not poisonous to
bathers. Not so, however, witli the gigantic Cyanea arctica,
whose long tentacles are poisonous ; fishermen as well as
bathers being often annoyed by them. This giant jelly-fish
sometimes attains a diameter of from three to five feet across
68- ZOOLOGY.
the disk, though it is produced from a Scyphistoma net
more than half an inch in height. Pelagla campanella and
a few other forms do not undergo this metamorphosis, but
grow directly from the eggs, not having a Strobila stage.
Various boarders or commensals — viz., temporary non-
attached parasites — live in or under the mouth-cavity or be-
t ween the four tentacles of the larger Acalephs. Such is the
little Amphipod Crustacean, Hyperia, which lives within
the mouth, while small lishes, such as the butter-fish, swim
under the umbrella of the larger jelly-fishes, Cyanea, etc., for
shelter and protection. Besides small animals of various
classes, the larger jelly-fishes kill by means of their nettling
organs small cuttle-fishes and true fishes, the animals being
paralyzed by the pricks of the minute barbed darts.
Order 3. Siphonophora. — These are so-called compound
Hydroids, living in free-swimming colonies, consisting of
polymorphic individuals, or, more properly speaking, zooids
— that is, organs with a strongly marked individuality, but
all more or less dependent on each other. A Siphonophore,
such as Pliymlia, for example, may be compared to a so-
called colony of Hydr actinia, in which there are nutritive
and reproductive zooids and medusa-buds. In Physalia
there are four kinds of zooids — I.e. (1) locomotive, and (2)
reproductive, with (3) barren medusa-buds (in which the
proboscis is wanting), which, by their contractions and
dilatations, impel the free-swimming animal through the
water ; in addition, there are (4) the feeders, a set of di-
gestive tubes which nourish the entire colony. Tbere are
numerous genera and species (one hundred -and twenty are
known), whose structure is more or less complicated and
difficult to understand without many -figures and labored
descriptions. We will select as a type of the order our
Physalia Aretliusa of Tilesius, or Portuguese man-of-war
(Fig. 49), which is sometimes borne by the Gulf Stream as
far north as Sable Island, Nova Scotia. It is excessively
poisonous to the touch, and in gathering specimens on the
shores of the Florida reefs we have unwittingly been stung
by nearly dead, stranded individuals, whose sting burns like
condensed fire and leaves a severe and lasting smart.
POR T UG UESE MAN- OF- WA R.
The colony or hydrosome of the Portuguese man-of-war
consists of long locomotive tentacles, which, when the ani-
mal is driven by its broad sail or float before the wind,
stretch out in large individuals from thirty to fifty feet.
These large Hydra-like zooids are arranged in small groups,,
arising from a hollow stem com-
municating with the chymiferous
cavity extending between the in-
ner and outer wall of the float.
The " feeders " are of two kinds,
large and small, and are clustered
in branches growing from a com-
mon hollow stem, also communi-
cating with the chymiferous or
body-cavity. L. Agassiz, whose
description of this animal we are
condensing, states that he has
seen these feeders "gorged with
food almost to bursting," but has
never seen undigested food in
any of the other organs. The
medusa-buds (gonophores) arise
from a third set of very small
Hydras, but form very large clus-
ters suspended between the clus-
ters of feeders. These reproduc-
tive zooids resemble the locomo-
tive zooids, but, like the feeders,
have no tentacles. The medusa-
buds, which are male or female,
arise singly, either from the base
of the reproductive zooids or
from the stems which unite the
latter. These buds, as in Tula-
laria, wither without dropping from their parent stock. It
appears, then, that the floating hydrosome of a Siphon-
ophore is like that of the fixed Hydractima or Coryne, with
the addition of locomotive zooids and a float, as seen in-
, Vcldla, or the swimming-bells of Halistemma.
Fig. 49. — Phyxa/ia, or Portuguese
man-of-war. — After Agassiz.
70 ZOOLOGY.
The Siphonophores, as observed in Aga.lma,
Agalmopsis, and other forms, arise front eggs which pass
through a morula, planula, and gastrula stage. The further
development of Aytdnujjtxi* clrt/tntx, a Siphonophore native
to the shores of New England, has been described by A.
Agassiz as follows : In the earliest stage noticed the young
looked like an oblong oil-bubble, with a simple digestive
cavity. Soon between the oil-bubble and the cavity arise a
number of medusa-buds, though without any proboscis
(manubrium), since the medusa-buds are destined to form
the " swimming-bells," which take in and reject the water,
thus forcing the entire animal onward. After these swim-
ming-bells begin to form, these kinds of Hydra-like zooids
arise. In one set the Hydra is open-mouthed, and is, in
fact, a digestive tube ; its gastro-vascular cavity connecting
with that of the stem, and thus the food taken in is circu-
lated throughout the community. These are the so-called
" feeders." The second set of Hydras differ only from the
feeders in having shorter tentacles twisted like a corkscrew.
In the third and last set of Hydras the mouth is closed, and
they differ from the others in having a single tentacle in-
stead of a cluster. Their function has not yet been clearly
explained. New zooids grow out until a long chain of
them is formed, which moves gracefully through the water,
with the float uppermost.
All the Hydroids in their f i-ee state as medusae are more or
less phosphorescent, and as much or more so after death,
when their bodies become broken up, and the scattered frag-
ments light up the waves whenever the surface of the ocean
is agitated. From this cause the sea is especially phosphor-
escent in August and September, when the jelly-fishes arc;
dying and disintegrating. These creatures serve as food for
the whalebone whales, which swallow them by shoals.
The smaller species are abundant in the circumpolar seas,
while in the tropics the Siphonophores are especially nu-
merous, none occurring in the Arctic regions. The Hy-
droids are widely distributed, a species of Campanularia be-
ing common to the Arctic and Antarctic seas. The species
-occurring on the New England coast are in many cases
DISTRIBUTION OF HYDROZOA. 71
found in Northern Europe, being circumpolar in their range.
A distinct assemblage of Sertularians, characterized by the
large number of species of Plumularia, inhabits the Florida
seas down to a depth of five hundred fathoms. Among
the Discophora the Lucernariae are arctic as well as temper-
ate forms, while Cyanea is peculiar to the Northern Hemi-
sphere. Aurelia and Pelagia are cosmopolites, while Rhaco-
}>ilns, Placois, and Lobocrocis are peculiar to the Southern
Hemisphere. The larger number of species are tropical and
sub-tropical. As regards their bathymetrical distribution,
while several species extend to the depth of five hundred
fathoms, Monocaulus flourishes in gigantic proportions at
the enormous depth of four miles.
The range in geological time of the Discophora extends
to the Jurassic period (middle Oolitic), large species of jelly-
fishes occurring in the Solenhofen slates. The genus Hij-
dractima first appeared in the Cretaceous period. Grapto-
lites were common in the shales of the Potsdam period, so
that if Graptolites are Acalephs, the latter are probably as
old a type as any, being contemporaneous with trilobites,
brachiopods, mollusks, worms and sponges.
CLASS I.— THE HYDROZOA.
Body in its simplest form a sac attached by the aboral end, composed of
two cell-layers, with a mouth and gastro-vascular cavity, and in all cases,
•except Protohydra, provided with tentacles, which are hollow , forming con-
tinuations of the body -cavity. The body (hydrosome) usually differentiated
into two sorts of zooids, nutritive (polynitrx) and reproductive (gonosomes),
toimectcil by a common stem or nutritive canal (ecenosarcj, the gonosomes
producing medusa-buds (go nophores}, which on being set free are catted me-
d'isfe (or medusoids) and are bisexual.* In these medusa the body is dixk
or bell-shaped, the jelly-like parenchymatous substance composing the disk
constituting the mesoderm. From the gastro-vascular cavity four primary
gasfro-rascular canals radiate and anastomose with a marginal circular
cfinal. Xo distinct organs of circulation, the blood being sea-water con-
taining the chyme and a few colorless blood-corpuscles. A true nervous
system rarely present, but when developed in certain medusoids, forming a
* Agassiz saw in Rh'zogeton, a form allied to Hydractinia, a gonophore which had
discharged its contents, degenerating into apolypite or hydra, and its body elongating
arid developing tentacles. Allmau observed the same thing in Cordylophora.
72 ZOOLOGY.
thread-ring around the disk, and with ganglia near the sense-organs. Tn
Hydra the nervous system is represented by nervo-muscle cells ; sense-
organs usually present, represented by simple eyes and auditory vesicles
(lithocysts), the two not usually coexisting. Nettling organs (nematocystx)
usually present, and especially characteristic of the class, being most abun-
dant in tlie tentacles.
Tlie sexes rarely united, usually distinct. Often a high degree of poly-
morphism in the individual hydrosome, tlie animal being differentiated not
only into polypites and gonosomes, but, in the free-swimming forms, into
locomotive zooids. Reproduction takes place by budding, and by fertilized
eggs developed in glands attaclml to or dependent from the primary ra-
diating canals. Tlie species undergo eitlier a slight or marked metamor-
phosis, the free gonophores being medusae (or medusoids), which produce
eggs, from which in some Discophora (such as Aurelia) arise successively
a morula, gastrula, planula, scyphistoma, strobila, and adult medusa,
representing distinct stages of growth.
Order 1. Hydroidea. — The individual either not differentiated into
zooids, as in Protohydra and Hydra, or consisting of nutri-
tive and reproductive zooids forming a compound, station-
ary, branching, moss-like body (hydrosome), the medusa-
buds remaining on the gonosomes or becoming free medusae,
with usually four simple radiating canals, a velum, manu-
brium, and naked eyes. Hydrosome either naked or as in
Sertularia, etc., protected by a horny sheath, or forming, as
in Millepora and Ileliolites, a massive corallum. Suborder 1.
TubularioR (Hydra, Clava, Hydractinia, Millepora, Tubularia).
Suborder 2. Campanularm (Plumularia, Dynamena, Cam-
panularia, ^Equorea, Zygodactyla).
Order 2. Discophora. — Medusa? like those of the Hydroids, but with
the four primary radiating canals usually subdividing into
numerous branches, the eyes more or less covered by a flap ;
the velum often absent ; often four genital pouches, dis-
charging eggs into the gastro-vascular cavity ; usually of
large size, and developing either directly from eggs, or, as
in Aurelia, passing through a gastrula, scyphistoma, and
strobila stage, not being developed from a hydra-like poly
pite. Suborder 1. TrncJiymedusce (^Egina, Cunina, Gery-
onia, Charybda?a). Suborder 2. Lucernarice (Lucernaria).
Suborder 3. AcalephcR (Pelagia, Cyanea, Aurelia, Rhizos
toma).
OrderS. Siphonophora. — Free-swimming, polymorphic hydrosotnes,
with nutritive, feeding, reproductive and locomotive zooids.
Suborder 1. Physophorm (Agalma). 2. Physalifp (Physalia).
3. Calycophorce (Diphyes) 4. Dixcnidew (Velolla, PrrpitaV
STUDY OF HYDROZOA. 73
NOTE. — Stephanofyplius mirabilis Allman is the type of a new order
of Hydrozoa called by Allman Tfiecomedusce. The animal permeates
and is parasitic in sponges. Although a Hydrozoan, it is not a
Hydroid, and cannot be referred to any of the existing orders of the
Hydrozoa. The ehitinous tubes which permeate the sponge-tissue are
united toward the base of the sponge, and constitute a colony of zooids.
In many respects it is said to resemble the Campanulariw.
VIEW OF THE CLASSIFICATION OF THE HYDROZOA.
Siphonophora.
(Physalia.)
Discos
(Aur
ohora.
elia.)
Hydr<
(Hyc
HYDROZOA.
Laboratory Work. — The common Hydroids, such as Coryne, Sertu-
laria, etc., may be collected from seaweeds or the piles of wharves
between tide-marks, while the medusae may be obtained by the
hand-net, or tow-net from a boat. The medusae especially abound
in eddies off points of land where different currents of the sea meet.
Towing is most effectively pursued after sunset and early in the even-
ing, Avhen the seals calm, and the jelly-fish swim near the surface.
They should be placed iu the jars by inverting the net in the water of
the jar, and examined at once, as many will have perished by the next
morning. Jelly-fish can also be reared in roomy aquaria, in which
plenty of air is introduced by running water.
The larger medusae, such as Aurelia and Cy<tmu,, should be sliced
in sections in order to study their gross anatomj', and portions snipped
off with scissors to be examined with the microscope. The animals of
Sertularians, Coryne, etc., can be studied alive in animalcule-boxes
and growing-cells. The coral stock of Millepora was examined by
Moseley in ground sections. " Portions of the living coral were placed
in absolute alcohol, chromic acid, and glycerine ; portions were further
treated with osmic acid and transferred lo glycerine or absolute alcohol.
Fragments of the hardened coral were afterward decalcified with
hydrochloric acid, and the residual soft structures were either mounted
entire for examination, or cut in the usual manner into fine vertical
and horizontal sections, which were then stained with carmine or
magenta. The specimens hardened in osmic acid, and decalcified after
subsequent immersion in absolute alcohol, yielded the best histological
results."
IV
4 ZOOLOG Y.
While the jelly-fishes should he studied alive, the larger ones can he
preserved in alcohol, after being killed by the gradual addition of
alcohol to the sea-water in which they are living. The small. medusae,
as well as Nocliluca and the Ctenophores, have been preserved with suc-
cess hy E. ^7'an Beueden, by the use of a solution of osmic acid or o{
picric acid. Osmic acid hardens the tissues so that fine sections can
be made, and it colors black the greasy matters, and especially myeline,
a chemical substance usually found in the nervous system, and enables
us to trace well the limits of the cells. The small jelly-fishes may be
placed in a very weak solution of osmic acid (5 to -^ percent, of
water) varying with the size of the animal, for from fifteen to twenty-
five, minutes, when the animal turns brown. This brings out clearly
the gastro- vascular canals. The specimen can then be placed in strong
alcohol, without losing its form and transparence. These animals and
all other transparent animals can be well kept in a concentrated, watery
solution of picric acid. Professor Semper tells us that all soft animals,
•worms as well as hydroids and polyps and mollusks, may be killed ex-
panded in chromic acid (l£ per cent), or in acetic acid of variable
strength, and then preserved in alcohol.
CLASS II. — THE ACTINOZOA (Sea-Anemones and Coral
Polyps).
General Characters of Actinozoans.— So persistent is the
form and structure of the body in these animals, that a
study of the common sea-anemone will enable the student
to readily comprehend the leading and most fundamental
characteristics of the class.
The common Actinia of our coast (Metridium marginal um)
is to be found between tide-marks on rocks under sea- weeds,
or in tidal pools, but grows most luxuriantly on the piles of
bridges. It readily lives in aquaria, where its habits may
be studied. An aquarium may be improvised by using a
preserve-jar or glass globe, covering the bottom with sand,
with a large flat stone for the attachment of the sea-ane-
mone. By placing a green sea- weed (ulva) attached to u
stone in the jar, and filling it with sea-water, the animal
may be kept alive a long time. After observing the move-
ments of the crown of tentacles as they are thrust out or
STRUCTURE OF THE SEA- ANEMONE. 75
withdrawn, specimens may be killed expounded by the grad-
ual introduction of fresh water, or by plunging them into
picric acid. They should then be transferred to the strong-
est alcohol, and allowed to soak in it for two or three days
until the tissues become hard enough to cut well. Then,
vertical and transverse sections may be made with a sharp
knife. The first fact to observe is, that an alimentary canal
is much more clearly indicated than in the Hydrozoa, there
being a distinct digestive sac, separate from the body-walls,,
hanging suspended from the mouth-opening, and held in
place by six partitions or septa (mesenteries), which divide
the body-cavity into a number of chambers. The digestive
sac is not closed, but is open at the bottom of the body,
connecting directly with the chambers, so that the chyme,
or product of digestion, passes down to the floor of the
body, and then into each of the chambers ; thus, by the
movements of the cilia lining the body-cavity, the chyme,
mixed with the blood, is distributed throughout the body ;
this rude mode of circulation being the only means of dis-
tribution of the nourishment contained in the circulating
fluid, there being no distinct canals, as in the Hydrozon.
These mesenteries may be best studied in a cross-section of
the animal after being hardened. It will be found that
there are six pairs of complete or primary septa or partitions
(mesenteries) which hold the stomach in place, and a num-
ber of pairs of shorter ones of unequal length between the
complete ones. There are never less than twelve of the
secondary partitions, even in the young, and when more
numerous they occur in multiples of six (Clark). On the
free edges of these shorter mesenteries, which do not extend
out to the stomach, there is a mass of long coiled filaments,,
the mesenterial filaments (cmspeda, Fig. 50, cr), which con-
tain lasso-cells, situated in a peripheral layer, while the fila-
ment is hollow and contains guanin. In dissecting the
sea-anemone these mesenterial filaments are always more
or less in the way, a## have to be carefully removed so as to
expose the ovaries and adjoining parts. ' They press out of
the mouth and the oinclides (small openings through the
76
ZOOLOGY.
body-walls), not always present, and end of the tentacles,
aud thus come in contact with animals forming their food.
The ovaries aud spermaries can be distinguished by their
forming masses of closely convoluted tubes much thicker
than the mesenterial filaments, and situated on the outside
next to the free edge of each mesentery ; they are also of a
pale lilac tint in Mi'tridiiun muryuititiini (Fig. 50, o). They
are not easily distinguishable from each other by the naked
•/
eye. The figure shows at the base of the body the free
edges of the mesenteries (nt) of different heights, with the
spaces between them through which the chyme passes into
the body-cavity. For the com-
plete passage of the circulating
fluid tbe six primary mesenteries
are perforated by a large orifice
(op) more or less oval or kidney-
shaped in outline (Fig. 50). The
digestive sac is divided into two
divisions, the mouth and stomach
proper, the latter when the ani-
mal is contracted being much
shortened, and with the walls
vertically folded, as seen in the
cut.
In the tentacles are lodged the
lasso-cells or nematocysts, and
the tentacles are hollow, com-
municating directly with a cham-
ber or space between the mesen-
teries, and are open at the end. When a passing shrimp,
small fish, or worm comes in contact with these tentacles,
the lasso-cells are thrown out, the victim is paralyzed, other
tentacles assist in dragging it into the distensible mouth,
where it is partly digested, and the process is completed in
the second or lower division of the digestive canal. The
bones, shells, or hard tegument of the animals which may
be swallowed by the Actinia are rejected from the mouth
after the soft parts are digested. Pigment-cells, which are
Fig. 50. —Partly diagrammatic
sketch of the anatomy of an Actinia
(Metridium) with the tentacles dis-
proportionately enlarged, s, stom-
ach ; m, mesenteries, or septa ; o.
ovary ; ci, cinclis ; cr, meseuterial
filaments; e, eyes; op, orifice through
the septa.— Drawn oy J. S. Kingsley,
under the author's direction.
STRUCTURE OF THE SEA-ANEMONE. 7?
supposed to be liver-cells, are said to be situated in the walls
of the stomach, and the mesenterial filaments have been sup-
posed to act as kidneys in taking up and excreting the waste
products of digestion, but this has not been proved and seems
improbable. The blood, or sea-water, mixed with particles
of food (" chylaqueous fluid ?'), the result of digestion, was
supposed by Williams to represent the chyle of higher ani-
mals and to contain white blood-corpuscles, but this has
been denied by Lewes (" Sea-side Studies'') on apparent good
grounds. Bilateral or right and left symmetry is faintly in-
dicated in the young and old Actinia, as well as in some
corals, as pointed out by Clark.
While no true nervous system is known to exist in the
Actinozoa, Duncan has discovered in the base of the body a
plexus of fusiform ganglionic cells connected by nerve-fibres.
Isolated nerve-cells have been discovered by Schneider and
Rotteken near the pigment-cells or supposed eyes at the
base of the tentacles of the Actinia. In connection with
these nerve-cells are certain round refractive cells (Haimean
bodies) and other long cells, called the Rottekon bodies.
The former are thought by Professor Duncan to carry light
more deeply into the tissues than the ordinary epithelial
cells. This is also the case with the elongated Rotteken
cells and others similar to them, called bacilli. All these,
when brought together in this primitive form of eye,
"concentrate and convey light with greater power, so
as to enable it to act more generally on the nervous sys-
tem probably not to enable the distinction of objects, but
to cause the light to stimulate a rudimentary nervous sys-
tem to act in a reflex manner on the muscular system, which
is highly developed." (Duncan.)
Nearly all the Actinozoa increase by budding, new indi-
viduals arising at the base or edge of the pedal disk of the
old ones. Clark has seen in Metridium marginatum as
many a» twenty buds separate from the parent sea-anemone.
" As in Hydra they arise as simple rounded protuberances,
but in a short time six short tentacles make their appear-
ance at the free end, and a minute oblong aperture, the
78 ZOOLOGY.
mouth, is found in their midst in such a way that its two
ends have a tentacle opposite each, and the other four dis-
posed two on one side and two on the other. Within, the
organs arise at points corresponding to the position of those
outside. The semi-partitions, twelve in number, begin as
mere ridges, which extend in pairs from the anterior end of
the stomach along the oral Avail toward its border." Adult
Actinias sometimes, though rarely, subdivide longitudinally,
but it is not uncommonly observed in the corals, in which
cases only the heads and stomachs divide, the general cav-
ity remaining common to the two.
The development of Actinia meserribryanthemum has been
traced by Lacaze-Duthiers. The young Actinia attains
maturity without any metamorphosis. The egg is supposed
to undergo segmentation within the ovary. In the state in
which the embryo was observed by Lacaze-Duthiers it was
oval and surrounded by a dense coat of transparent conical
spinules. Soon the two primitive germi-
nal layers (ectoderm and endoderm)
were observed. Two lobes next appear
within the body ; these subdivide into
four, eight, and finally twelve primitive
lobes. This stage is represented by the
corresponding stage of the coral (Fig. 55,
B\ Not until after the twelve primitive
lobes are fully formed do the tentacles
Pis. 5i.- -ciliated larva begin to make their appearance. When
(gastrnla) of a Polyp, ft, , , „ , , ,
primitive opening or Mas- the first twelve tentacles have grown out,
ec?odennf' dS,t0endoderm! twenty-four more arise, and so on, until
-After Metechnikoff. wit]v itg jncreasjng sjze the Actinia is
provided with the full number peculiar to each species.
Lacaze-Duthiers observed the same changes in two species
of Sagartia, and in Bunodes gemmacea. Fig. 51 represents
the ciliated gastrula of an unknown polyp allied ioKalliphobe.
While Metridium and Bunodes are types of the ordinary
form of Actinoids, certain forms, like Halcampa producta
Stimpson (Fig. 52), are quite long and live fixed in the
mud or sand. Allied to Halcampa is Edwards ia, which
VORAL POLYPS.
79
lives in deeper water. Its young, however, is at an early
stage of its existence a free-swimming polyp, which was
originally described as an adult animal under the name of
Arar/iiHtctitt. In Zoanfh-iix the tegument is tough and.
leathery, and the different polyps are con-
nected by stolons. Epizoanthus americanus
Verrill lives in deep water, off the coast of
New Jersey and Southern New England, in
about twenty fathoms. Cerianthus, a gigantic
form, a native species of which (C. borealis
Verrill) lives at the depth of one hundred
fathoms in the Gulf of Maine deeply sunken
in the mud, where it secretes a shiny leathery
tube, is perforated at the end of the body ;
the young of a corresponding European
species is also free-swimming, like the young
Edwardsia.
The coral polyps differ from the Actinoids
in secreting in the mesoderm a limestone
base, from which arise in the Zoantharian
corals stony septa serving as a support to the
animal ; these septa are deposited or secreted
in the chambers, so that in the coral polyp
there are soft partitions alternating with the
limestone ones, the latter formed at the base
, . , „,.,. ., . Fig. 52. — Hal-
of the polyp, not completely filling the inter- campa producta.
-•V , , -After Verrill.
meson terial chambers.
Order 1. Zoanflmna. — We will now enumerate some of
the leading forms of the first order of Anthozoa, the Zoan-
tliaria, to which the sea-anemones and most of the stony
corals belong. The group is called by some recent authors
Hexacoralla, the number of primary chambers and tenta-
cles being six, the latter rounded, conical, or filiform. In
the simple cup-shaped corals, as Dcltocyatlius and (Jaryo-
pliyllia, the coral forms a cup or t/teca, the lamellae which
arise from the base terminate in as many septa, the spaces
between which are termed lovuli. A central pillar or col-
umn formed by the union of the septa, or arising indepen-
80 ZOOLOGY.
dently, is called the columella, while the small separate pillars
between the columella and the septa are termed pahili. In
the compound or tree-like corals, each young coral polyp
forms a calicle, theca, or limestone support of its own, which
unites with the other by calcification of the connecting sub-
stance of the common body. This intermediate layer is
termed ccenenchyma (Huxley).
The simpler corals consist of but a single calide contain-
ing one polyp, as in Flabellum, Deltocyathus, and Caryo-
pliylUa. They live free, fixed in the mud in deep water,
and occur in water with a temperature of about 32° Fahr.
Flabellum angular e Moseley has been dredged off Nova
Scotia in 1250 fathoms.
Deltocyathus Ayassizii, which is not uncommon in the
Florida channel, at depths varying from sixty to three hun-
dred and twenty-seven fathoms, has been dredged by us at the
mouth of Massachusetts Bay, in one hundred and forty fath-
oms (temperature 39° to 42° Fahr.). An allied form is
Ulocyathus arcticus Sars, said by Duncan to be the same as
Flabelliini laciniatuiii Edwards and Haime, a fossil of the
late tertiary, dredged by us in one hundred and fifty fath-
oms, near St. George's Banks, Gulf of Maine.
In the family of which Ocullna, the eye-coral, is a type,
the polyp stock is compound, branched, increasing by lat-
eral buds. Lophohelia prnlifera Pallas (Fig. 53) occurs
in the seas of Norway, and has likewise been found to occur
on the banks off Nova Scotia and Newfoundland, while it
lives in the Florida Straits, in from 195 to 315 fathoms.
In Mceandrina, or the brain-coral, Favia, Astraaund Ax-
tranyia, we have representatives of the important group
Astrceacca, in which the corallum is massive, more or less
Hemispherical, and the polyp-cells or calicles are distinctly
lamello-radiate within, and generally so without. Budding
is usually carried on by division of the disks, or by spon-
taneous fission. In Mussa the polyps are sometimes two
inches in breadth, as large as ordinary Actinine. Dlploria
cerebriformis Edwards and Ilaime is a brain-coral which is
common in the West Indies and at the Bermudas, some-
CORAL POLYP X.
81
times growing to a diameter of three feet. The common
large West Indian brain-coral is Mieandrina labyrinthica.
In Astrcea pallida Dana, of the Feejee Islands, the polyps
are pale, the disks bluish gray, and the tentacles whitish.
The polyps of many corals are beautifully colored. Those
Fig. 53. — Lophohelia prolifera. — After Wyville-Thompsou.
of Astranyin Dance, Agassiz are white. In this coral, as
observed by Dana, the polyps stand prominently above the
calicles, as only their bases secrete coral. The tentacles
have minute warty prominences, each full of lasso-cells.
82 ZOO LOOT.
This coral ranges as far north as Nantucket and Buzzard's
Bay. In the mushroom corals, Ftnujia, the large corallum
is the secretion of a single polyp which may be a foot in
length. Large branching corals abound on the reefs of
Florida, the most abundant of which grows nearly two feet
high and branches out like the horns of a deer. Such is
Mmlrepora cervicornis Lamarck.
AVhile agamogenesis or alternation of generations is rare
among the Actinozoa, Semper has observed two species of
Fungia which he considers to reproduce in this way. The
corals " bud out from a branched stem, and then become
detached and free, as is the habit of the genus." Moseley
Pig. 54. — Coral polyp (As/rouies culycutat'in) expanded. — From Tenuey's Zoology.
also describes a similar case of production of three or tVur
generations in a Tuhitan species of Fungia.
As a good example of the mode of development of one of
the suborder Madreporaria, we will, with Lacaze-.Duthiers,
study the development of Axtroidex caliicn.larim Pallas.
The period of reproduction takes place between the end of
May and July, the young developing most actively at the
end of June. Unlike Actinia, which is always hermaphro-
ditic, this coral is rarely so, but the polyps of different
branches belong to different sexes.
As in the other polyps, including Actinia, the eggs and
DEVELOPMENT OF CORAL POLYPS.
83
spermatic bodies rupture the walls of their respective glands
situated on the fleshy partitions. As in Actinia, Lacaze-
Duthiers thinks the fecundation of the egg occurs before it
leaves the ovary, when also the segmentation of the yolk
must take place. Unlike the embryo Actinia, the ciliated
voung of the coral, after remaining in the digestive cavity
for three or four weeks, make their way out into the world
through the tentacles. The appearance of the young, when
first observed, was like that in Fig. 55, A, being an oval,
ciliated gastrula with a small mouth and a digestive cavity.
The gastrula changes into an actinoid polyp in from
thirty to forty days in confinement, after exclusion from the
parent, but in nature in a
less time, and it probably
does not usually leave the
mother until ready to fix
itself to the bottom.
Before the embryo be-
comes fixed and the tentacles
arise, the lime destined to
form the partitions begins
to be deposited in the enclo-
derm. Fig. 55, C, shows the
twelve rudimentary septa.
These after the young polyp
or " actinula" has become
stationary, finally enlarge
and become joined to the
external walls of the coral
now in course of formation
(Fig. 55, C, c), forming a groundwork or pedestal on which
the actinula rests. D represents the young polyp resting
on the limestone pedestal.
Lacaze-Duthiers found that the embryo polyp which had
been swimming about in his jars for nearly a month, sud-
denly, within the space of three or four hours after a hot
sirocco had been blowing for three days, assumed the form
of small disks (Fig. 55, B), divided, as in the Actinia, into
twelve small folds forming the bases of the partitions within.
Fig. 55. — Development of a coral polyp.
Astroidi-s ccdycularis. A. ciliated gastrola:
B, young polyp with 12peptii: (7, D. young
polyp farther advanced, with 12 tentacles:
c, the corallmn and limestone pepta begin-
ning to form. — After Lacaze-Duthiers.
84 ZOOLOG Y.
The tentacles next arise, being the elongation of the
chambers between the partitions, six larger and elevated,
six smaller and depressed (Fig. 55, I)). The definitive form
of the coral polyp is now assumed, and in the Astroides it
becomes a compound polypary.
There are but few facts regarding the rate of growth of
corals. Pourtales states that a specimen of Mceandri/m
labyrinthica, measuring a foot in diameter and four inches
thick in the most convex part, was taken from a block of
concrete at Fort Jefferson, Tortugas, which had been in the
water only twenty years. Major E. B. Hunt calculated
that the average growth of a Ma?andrina observed by him
at Key AVest was half an inch a year. From the observa-
tions and specimens collected by Mr. J. A. Whipple, as
stated by Verrill, a Madrepora found growing on the wreck
of the Severn grew
fl to a height of sixteen
feet in sixty-four
years, or at the rate
of three inches a
year.
jf \3RJHf The
^"^ of Milne-Edwards
Fig. 56.— a. Haplophyllia paratlora ; b vertical sec- an(J Haime Contains
tion; c, caliclefrom above.— After Pourtales.
a large number of
palaeozoic corals, which are mainly characterized by having
four primary septa, the number in most living corals being
six ; and also by intracalicinal gemmation, which also occurs
in a few Caryophyllids and Oculmids.
Pourtales has doubtfully referred to this group his Hapln-
pliyttia paradoxa (Fig. 56) which inhabits the Florida
Straits at a depth of over three hundred fathoms. The
nearest known fossil ally of this interesting coral is Calo-
pliyllum profundum Germ., which is fossil in the Dyas for-
mation. Duncan describes Guynia annulata, another deep-
sea coral, as a recent Rugose tetrameral coral. Moseley
suggests from a study of Heliopora, together with Crypto-
lielia and other Stylasteridcs, that " the marked tetrameral
arrangement of the septa in Ruyosa, and the presence in
ALCTONARIAN POLYPS. 85
many forms of tabulae, are certainly characters not opposed
to the alliance of these corals with the Alcyonarians," and
gives other reasons of importance in favor of this view.
The group of Antipathea, represented by Antipallies ar-
borea Dana, of the Feejee Islands, produce compound
groups by budding, growing in the form of delicate shrubs.
The polyps have usually six tentacles, though in Gerardia
they have twenty-four.
Order 2. Alcyonaria. — To this group of polyps, which
have eight serrated or feathered tentacles, belong the red
coral of commerce, the sea-fans and sea-pens, in which there
are no calcareous septa, and in which the corallum has, as in
the sea-fans and sea-pens, a bony axis, while the fleshy por-
tion (coenosarc) represents the mesoderm and is filled with
calcareous spicules.
In the genera Haimea, Alcyonium, Tubipora, etc., the
polyps are encrusting, budding out in different ways, and
adhere to foreign bodies by the ccenenchyma. Haimea is
simple, consisting of but a single polyp. In Alcyonium
the coenenchym is much developed, soft, lobulated, and
branching. Our common species is A. carneum Agassiz.
In Tubipora the polyps are compound and secrete solid
calcareous, bright red tubes, arranged side by side, like the
pipes of an organ, and supported by horizontal plates.
In the common red coral (Corallium rub rum) of the
Mediterranean Sea, the solid, unjointed coral-stock has a
thin cortical layer of spicules into which the polyps are re-
tractile. The bright-red coral is worked into various orna-
ments. The coral fishery is pursued on the coasts of Algiers
and Tunis, where assemble in the winter and spring from
two hundred to three hundred vessels. The coral-fisherman,
with large rude nets, break off the coral from the submerged
rocks. About half a million dollars' worth of coral is annu-
ally gathered.
Heliopora, now proved by Mr. II. N. Moseley to be an
Alcyonarian instead of an Actinoid polyp, differs from
Corallium and Tubipora " in that the hard tissue of its
corallum shows no signs of being composed of fused spic-
ules." This genus, together with Polytremacis and the
36 ZOOLOGT.
Silurian Heliolites, form, according to Moseley, a new
family of Alcyonarians in which the corallum consists of an
abundant tubular coenenchym, with calicles having an
irregular number of pseudo-septa, which do not, however,
correspond with the membranous mesenteries. The polyps
are completely retractile, with the tentacles when retracted
introverted. The mouths of the sacs lining the coenenchy-
mal tubes are closed with a layer of soft tissue, but com-
municate with one another and with the calicular cavities
by a system of transverse canals (Moseley). Ileliopora cceru-
lea grows on coral reefs at the Philippine Islands and at
Singapore.
In the family of sea-fans (Goryonidce) the coral-stock is
horny or calcareous, branching tree-like, or forming a flat
network. The short calicles of the single retractile polyps
stand perpendicularly to the axis, communicating by longi-
tudinal vessels and branching canals. Gonjmiui (Rliipir/or-
gia) flabellum- Linn, is red or yellow and abundant on the
Florida reefs. In the Arctic seas and the deeper, colder
waters of the Newfoundland Banks and St. G-eorge's Banks,
Primnoa reseda (Pallas) and Paragorgia arborca (Linn.)
grow ; the latter being of great size, the stem as thick
through as one's wrist, and the whole corallum over five feet
in height.
In the family of sea-pens (PennatulidcB) the polyp-stock
is free, growing in the sand or mud, usually with a bony
axis supporting the polyps, and capable of moving at the
base. In Peimatula, or the sea-pen, there are secondary
branches in which the polyps are situated ; this polyp is
phosphorescent ; one species (P. aculeaia Danielssen) lives
in deep water. An Arctic form, Umbellularia yroenlandica,
is a gigantic form, growing about four feet high, in from
three hundred to two thousand fathoms. The species of
Renilla are kidney-shaped, with the polyps placed on one
side. Renilla reniformis Cuvier is a rich purple species,
occurring in the sand at Charleston, S. C. According to
Agassiz, this animal is remarkably phosphorescent, emitting
*" a golden green light of a most wonderful softness."
While coral reefs are in part composed of Alcyonarians,
FORMATION OP CORAL RKEFS.
Polyzoa, and certain plants called Null i pores, the Madrepo-
raria in the main are the true reef-builders. They are con-
fined to waters in which through the coldest winter month
the temperature of the water
does not fall below 68° F.,
though usually the waters are
much warmer than this, the
mean annual temperature be-
ing about 73£° F. in the North
Pacific and 70° F. in the 5
South. Coral reefs are abun- 3
dant in the West Indies, but ^
still more so in the Central "g.
Pacific, where there are a c
much greater number of spe- §
oies of corals (Dana). Along |
the Brazilian coast, as far g
south as Cape Frio, are coral ^
reefs (Hartt). In depth living £•
coral-reef-builders do not ex- ^
tend more than fifteen or 3
twenty fathoms below the sur- £
iace. &
Coral reefs are divided by ?
Dana into outer or barrier 5-
reefs (Fig. 57) and inner reefs. ^
The barrier reefs are formed ^
from the growth of corals ex- 5
posed to the open seas, while 1
the inner or fringing reefs $
(Fig. 57) are formed in quiet p
water between a barrier reef
and the island. As coral
reefs are usually built upon
islands which are slowly sink-
ing, barrier reefs are simply
ancient fringing reefs formed when the island stood higher
above the sea, hence they are built up as rapidly as the land
.sinks, and thus the top of the reef keeps at the level of
88
ZOOLOGY.
the sea. The reefs are often of great thickness, for, as
Dana says, " could we raise one of these coral-bound islands
from the waves, we should find that the reefs stand upon
I
s
o
£
o
ts
b
O
13
1
o
Q
s
O
0
O
1
03
S
the submarine slopes, like massy structures of artificial
masonry ; some forming a broad flat platform or shelf
ranging around the land, and others encircling it like vast
FORMATION OF CORAL REEFS. 89
ramparts, perhaps a hundred miles or more in circuit."
Darwin has estimated that some reefs in the Pacific Ocean
are at least 2000 feet in thickness.
Thus far we have spoken of reefs surrounding mountainous
Islands ; coral islands or atolls (Fig. 58) resemble such reefs,
except that they surround a lake or lagoon instead of a high
island, the coral island itself being seldom more than ten or
twelve feet above the sea. and usually supporting a growth of
cocoanut trees, while the sea may be of great depth very near
the outer edge of the atoll, which " usually seems to stand as
if stilted up in a fathomless sea " (Dana). These reefs and
atolls are formed and raised above the sea by the action of
the winds and waves, in breaking up the living corals,
comminuting it and forming with the dtbris of shells and
other limestone-secreting animals and plants, banks or de-
posits of coral mixed with a chalky limestone, as the base of
the reef. When it rises above the waves, cocoanuts and other
seeds are caught and washed up on the top, and gradually
the island becomes large enough to support a few human
beings. The Bermudas are the remnants of a single atoll,
and are situated farther from the equator than any other
reefs. Most barrier reefs and coral islands or atolls are
formed in an area of subsidence, where the bottom of the
ocean is gradually sinking ; this accounts for the peculiar
form and great thickness of many reefs. On the other
hand, the coral reefs of the West Indies are, generally
speaking, in an area of elevation.
A section of a coral reef is shown by Fig. 59: n is the point
where the shore slopes rapidly down within the lagoon
(which lies to the right), and m is where the reef suddenly
descends toward the open ocean. Between b c and d e lies
the higher part of the reef. The shore toward the lagoon
slopes away regularly from d to n ; while toward the open
ocean there is a broad horizontal terrace (a to I c) which
becomes uncovered at low water.
The theory of the formation of barrier reefs is shown by
the diagram, Fig. 60. The island, for example, the volcanic
island Coro, which is slowly sinking, at the ancient sea-level
I is surrounded by a fringing reef ff, a small rock-terrace
90 ZOOLOff T
at the former level of the sea. Where the island has sunk to
the level of the water-line II, the reef appears at the sur-
face as at b' f, b f. There is now a fringing and a barrier
reef, with a narrow canal between them ; V is a section of
the barrier reef, e' of the canal or lagoon, and /' of the
fringing reef. After a farther submergence to the sea-level
III, the canal e" becomes much wider. On one side (//)
the reef is present, on the other side it has disappeared, ow-
ing to the agency of ocean-currents. Finally, at the water-
level IV, there are two small islands surrounded by a wide
lagoon, with two reef-islets i'", i'", resting upon two sub-
marine peaks. The coral reef has now grown to great di-
mensions, and covered almost the entire original island,
and though the reef-building coral polyps cannot live below
7»" III ••
*> * ^\ ~ '
t, e I
•T17
IS-
..-•
•~i" ^-.,--y v
^^_>'-'. ..-p" '-],'-
•n
mi-
3
»' f>^-
\v^-^-' "l L ~ -.
- B
ll •
/-"'f^.
--•s'
^^^-^^ "">
- T
i -
^<^X
u.
Fig. 60. — Schematic section of ari island with reefs.
a point fifteen or twenty fathoms below the surface, yet ow-
ing to the slow sinking of the island, they build up the-
reef as rapidly as the former subsides, and in this way after
many centuries a coral reef sometimes two thousand feet
thick may be built up in mid-ocean.
Semper has called attention to the influence of ocean
currents, and their varying strength and direction, in shap-
ing the forms of coral islands and reefs ; and Moseley holds
nearly the same view ; neither of these authors accepts the
theory of subsidence.*
Coral reefs are mainly confined to the Western and Cen-
tral Pacific and the Indian Oceans, and to the Caribbean
Sea. None occur on the west coast of North America or of
Africa, and only limited patches on the eastern coast of
South America. There were palaeozoic reefs, such as the
fossil coral reef extending across the Ohio River at Louis-
ville.
* See Semper's Animal Life; Agassiz' Three Cruises of the Blake.
ACTINOZOA.
91
CLASS II.— THE ACTINOZOA.
Ccelenterates with a digestive sac partially free from the body-cavity open-
ing into it below and held in place by six or eight mesenteries radiating from
the digest ice rarity and dividing the perieisceral space into chambers. Mouth
surrounded icith a circle of tentacles, which are hollow, communicating di'
redly with the pt.ririsccral chambers. A slicihtly marked bilateral symmetry.
To the edges of the mesenteries (usually the free ones) are attached the repro-
ductive glands, both male and female, or of one sex alone ; also the craspeda,
or mesenterial JUaments, ichich contain a large number of lasso-cells. Body
either entirely fleshy, or secreting a calcareous or horny coral-stock, and
wJien the species is social connected by a cu'nencJtyme. In some forms (sea~
pens) the entire colony capable of limited locomotion. No well-marked
nervous system, but a plexus of fusiform ganglionic cells connected by nerve-
fibres in the base of Actinia ns. Reproduction by self division, gemmation,
or by ova, the s< .res being separate or united in the same individual; Oie
young undergoing a morula and gastrula condition, and then becoming
fixed.
Order 1. Zoantharia. — Mesenteries and tejitacles usually six or in mul-
tiples of six, cnrallum with calcareous septa. Mesenterial fila-
ments abundantly developed (Astraea, Madrepora, Actinia).
Order 2. Alcyonaria. — Mesenteries and tentacles always eight in num-
ber. Coral-stock without true septa. Mesenterial fila-
ments not usually numerous. Corallum usually horny, and
the whole colony in the Pennatulacea capable of locomo-
tion (Alcyonium, Gorgonia, Pennatula, Renilla).
VIEW OP THE CLASSIFICATION OF THE ACTINOZOA.
ZoanlJiaria.
(AothiKi.)
I
Alcyonaria.
(Alcyonium.)
ACTINOZOA.
Laboratory Work. — Verrill has preserved Actiniae completely ex-
panded by slowly adding a saturated solution of picric acid to a small
quantity of sea-water in which they had expanded. When dead they
should be transferred to a pure saturated solution of the acid, and
allowed to remain for from one to three hours, according to size, etc.
They should then be placed in alcohol, which should after a day or two
be renewed. Thus hardened they can be cut into sections. Corals-
can be studied by grinding or sawing sections, and, if desirable, treated
as in the case of the corallum of the Millepores.
ZOOLOGY.
CLASS III. — CTENOPHORA (Comb-bearers).
General Characters of Ctenophores. — These beautiful an-
imals derive their name Ctenophora, or "comb-bearers,"
from the vertical rows of comb-like paddles (ctenophores)
situated on meridional bands of muscles which serve as lo-
comotive organs, the body not contracting and dilating as
in the true jelly-fishes. In their organization they are
more complicated than the Actinozoa, as they have a true
digestive cavity passing through the body-cavity, with two
posterior outlets (it will be remembered
that Cerianthus has one at the end of
the body). From this alimentary canal
are sent off chymiferous or water-vascu-
lar canals (Fig. 61) which correspond in
their mode of origin with the water-
tuhjp of the Echinoderms. As regards
the rows of paddles, each vertical row
consists of a great number of isolated,
transverse, comb-like fringes placed one
above the other, and movable, either
isolately or in regular succession or
simultaneously (Agassiz). As these rows
of paddles are connected for their whole
Fig. ei. -view of the ^"Sih with » chymiferous tube, they
eaetro-vascuiar canals of a
Pleurobrachia, from which
s of a probably aid in respiration. These ani-
x ., i i • i • ji
mals also stand mu.en higher in the scale
the two retractile arms
have been removed. A, , ,.„ ,-. ,, ,-, ~, , ,
from one side, the month- oi lite than the other Goelenterates by
opening above; B, seen ••• I-L.-IJ IJ.T j-i
from the mouth-end.- being more truly bilateral, the radial
symmetry so marked in the Actinia or
in the jelly-fish being in these animals less apparent, as the
parts are developed on opposite sides of a median plane.
The nervous system, as originally described by Grant, con-
sists of a ganglion situated at the aboral end (end opposite
to the mouth) of the Plenrobrachia, from which, among
other nerves, eight principal ones are distributed to the
eighf rows of paddles. A nerve also proceeds to the so-
called otolitic sac (lithocyst) seated upon the ganglion.
Eimer has lately shown that the nervous system of the
AFFINITIES OF GTMNOl'-HOttKS. 93
Ctenopliora, as, for example, that of Beroe, agrees in general
with that of the jelly-fishes, with the difference that in the
Ctenophores the nerve-centres are not situated on the edge,
but at the pole of the body opposite the mouth. On the
other hand, the nervous system is not radiated as in the
jelly-fishes or as in the Echinoderms.
Our commonest example of this class is the Pleurobrachia
rhododactyla Agassiz. It is a beautiful animated ball of
transparent jelly moving through the water by means of
eight rows of minute paddles, throwing out from a sac on
each side of the body two long ciliated tentacles. It is
abundant in autumn ; sometimes thousands may be seen
stranded on the shore at low water.
That the Ctenophores have affinities to the sea-anemones
(Actinozoa} is seen in the form and relations of the diges-
tive tract, though it differs in hanging free, not being held
in place by radiating mesenteries, and in this respect they
approach the Echinoderms. From their possessing a dis-
tinct digestive tract, the Ctenophores need not be confounded
with the jelly-fishes (Hydrozoa}. On the other hand, they
present some advance over the Actinozoa, and in some
respects connect the Hydrozoa and Actinozoa with the
Echinoderms. For example, the water-vascular system
arises in the Ctenophores as outgrowths from the digestive
sac, as they do in the young star-fish and sea-urchins. This
indicates that in the mode of development of both the di-
gestive tract and the water-vascular system the Ctenophores
are allied to the Echinoderms rather than to the Hydrozoa,
in which the water- vascular tubes arise as simple hollows in
the body-mass. Moreover, they are less radiated than in
the Hydrozoa or Echinoderms.
In Bolina alata Agassiz the body is plainly bilateral and
the water- vascular tubes are very distinct. In Idyia roseola
Agassiz the month is large, the stomach wide, and the
body is of an intense roseate hue. This beautiful species after
death, late in summer, is very phosphorescent ; all Cteno-
phores, however, even their eggs and embryos, are phospho-
rescent. In the Ctenophores the ovaries and spermaries occur
in the same individual and form blind sacs attached to the
94 ZOOLOGY.
water- vascular tubes, and are developed locally, as in Cesium,
or along the whole length of the tubes, the sexually-differ-
ent glands being placed in Beroe and allies on opposite
sides of the tube.
AVhen ripe the eggs pass into the perivisceral space, and
finally pass out through the openings of the body. The
eggs of Pleurobrachia escape singly ; in Bolinti they are
laid in strings, while those of Idyia are deposited in a thick
slimy mass. They spawn late in the summer and in the
autumn. The young develop in the autumn, becoming
nearly mature in the following spring. Development is di-
rect, the young hatching nearly with the form of the adult,
there being no metamorphosis.
The species are widely distributed, a number being com-
mon to both sides of the Atlantic, and the same species, ap-
parently, of Pleurolrachia and Idyia occur on the east and
west coast of North America. The most widely distributed
forms are the Beroids. While the genus Mertensia is en-
tirely arctic, the larger number of species are either tropi-
cal or subtropical. The classification of the group is shown
in the following summary.
CLASS III.— CTENOPHORA.
Spherical or oval, somewhat bilateral, scarcely radiated animals, with
jelly-like, transparent bodies. The digestive tract opens at the posterior
end into the perivisceral cavity ; from the canal pass off eight water-vas-
cular tubes, which are in close relation with eight vertical meridional series
of comb-like locomotive organs. Usually a pair of tentacles, which may
become withdrawn into sacs, and are provided with thickset lasso-cells on
the tentacular fringes. Nervous system consisting of an aboral ganglion,
sending off eight nervous filaments to each of the eight rows of paddles.
The sexual glands seated in the same iiuUridnal. No metamorphosis,
the young ichen hatched resembling the adult.
Order 1. Eurystomea. — Body oval, with a large mouth and capacious
stomach. The water-vascular tubes connected with the
ctenophores, and forming numerous ramifications, commu-
nicating by means of a circular canal near the mouth
(BeroB, Idyia).
CLASSIFICATION OF CTENOPHORES. 95
Order 2. Saccatce. — Body more or less spherical, with two long tenta-
cles capable of being wholly retracted in a sac (Pleuro-
brachia).
Order 3. Tceniata. — Body ribbon-like, being very much compressed in
the direction of the lateral diameter (Cestum).
Order 4. Lobattz. — Body lateral, compressed, bilobed (Bolina).
VIEW OF THE CLASSIFICATION OF THE CTENOPHORA.
Lobata.
(Bolina.)
Tcem'ata.
(Cestum.)
Saccata.
(Pleurobrachia.)
Eurystomea.
ffdyia.)
CTENOPHOKA.
Laboratory Work. — The Ctenophorse should be studied while alive.
They may be collected with a drag or tow-net from a boat when the
surface of the ocean is calm. For studying the fine anatomy and
tissues they should be treated by the same methods as the smaller jelly-
fishes.
LITERATURE.
L. Agassis. Contributions to the Natural History of the United
States. IIL-IV. 1860-1862.
Dana. Report of U. S. Exploring Expedition. Zoophytes. 1846.
Huxley. The Oceanic Hydrozoa. Ray Society, London, 1859.
M. Edwards and Haime. Histoire naturelle du Corail. i.-iii. Paris,
1857-1860.
Lacaze-Duthiers. Histoire naturelle du Corail. Paris, 1864.
Haeckel. System der Medusen. Jena, 1880-1881.
A. Agassiz. North American Acalephae. Mem. Mus. Cornp.
Zool. Cambridge, v. 1865.
A. Agassiz. Embryology of the Ctenophorae. 1874.
Kleineriberg. Hydra. Leipzig, 1872.
"With the works of A. Agassiz, Allman, Andres, H. J. Clark,
Claus, Ehrenberg, Gegeubaur, Gosse, O. and R. Hertwig, Hiucks,
Huxley, G. von Koch, Koelliker, Leuckart, Metschnikoff, Moseley,
Sars, Semper, Vogt, Weismanu, Wilson, etc.
CHAPTER IV.
BRANCH IV.— VERMES (WORMS).
General Characters of Worms. — Having studied the
one-celled animals, or Protozoans, and the radiated hydroids
and polyps without a body-cavity, we pass to an assemblage
of forms which even in the simplest types are seen to have a
dorsal and ventral, a right and left side, and a head and tail
end. It is rare that the form of a worm is so modified by its
habits or surroundings but that we are able to call it a worm,
though when we attempt to draw up a definition of the
branch or sub-kingdom Verities, one which shall exclude the
worm-like Holothurians or the Mollusks, or certain low mites
and Crustacea, or even the Amphioxus, we find it impossible
to lay down a set of characters which shall accurately and
concisely define them. This is due to the fact that the worms
are par excellence a generalized, synthetic type, from which
the other branches of the animal kingdom above the Protozoa
and sponges have probably originated. It will be well for
the student not to trouble himself at first about a definition
of the branch, but to study with care the leading types, and
then, in a review of the group, he will have a more or less
definite idea of the sub-kingdom, and perceive where its bor-
ders, here and there, merge into other branches, and he will
be then able to understand the grounds for the speculations
regarding the phylogeny or ancestry of the other branches,
which have all an apparent starting-point from low or simple
forms resembling such worms as we are next to describe.
As a provisional definition of a typical worm, we may say
that it is a many-celled, three-germ-layered, bilateral animal,
with a well-marked dorsal and ventral side and a head and
tail end, with the body in the higher forms divided at reg-
DIG Y EM A. 97
nlar intervals into segments (somites or arthromeres), with
usually a definite relation of the more important viscera to
the body-walls — i.e., a digestive tract extending from the
head to the end of the body, the nervous system consisting
of a brain, or supracesophageal ganglion, and a single or,
more commonly, double chain of ganglia, resting on the
floor of the body ; a dorsal vessel or heart is usually present
being situated above the digestive tract. True jointed
appendages are never present, and in the embryo the
blastoderm is usually without any " primitive streak " (the
Annulata excepted). This definition will exclude the worm-
like Actinozoa and Holothurians.
Before describing the lowest class of worms, we may call
attention to a small aberrant group called Mesozoa by E.
Van Beneden, the position "of which is doubtful, though the
animals composing it are probably aberrant worms.
In 1830 Krohn observed in the liquid bathing the " spongy
bodies," or venous appendages, of different species of
Cephalopods certain filiform bodies, covered with vibratile
cilia, and resembling Infusoria. They were afterward named
Dicyema by Kolliker, who with others considered them as
intestinal worms. In 1876 Professor E. Van Beneden gave
a full account of their structure and mode of development.
He states that these organisms have no general body-cavity,
but that the body consists (1) of a large cylindrical or fusi-
form axial cell, which extends from the anterior extremity
of the body, which is slightly enlarged into a head, to the
posterior end ; (2) of a single layer of flat cells forming
around the axial cell a sort of simple pavement epithe-
lium. All these cells are placed in juxtaposition like
the constituent elements of a vegetable tissue. There is
no trace of a homogeneous layer, of connective tissue, of
muscular fibre, of nervous elements, nor of intercellular
substance. There is only between the cells a homoge-
neous substance, such as is found between epithelial
cells. The axial cell is regarded as homologous with the
endoderm of the higher animals (Metazoci). Van Beneden
designates as the ectodermic layer the cells surrounding the
large, single axial cell. There exists no trace of a middle
98
ZOOLOGY.
layer of cells, nor of any organs, all the animal and vegeta-
tive functions being accomplished by the activity of the
ectodermic cells and of the single axial cell. There is no
mesodermic cell or cells. On account of these characteris-
tics. Van Beneden
regards these or-
ganisms as forming
the type of a new
branch of the ani-
m a 1 kingdom,
which he distin-
guishes as Mesozoa.
He places the
I
r~\
'Q\
branch or sub-
kingdom, between
the Protozoa and
all the many-celled
animals (Metazoa),
and includes the
hypothetical Gas-
trceades of Haeckel
in the branch.
While this position
may prove to be
the correct one, we
should prefer, while
not overlooking the
resemblance of the
Dicycmiclce- to the
Infusoria, and even
Fig. 62. — a, DicyernellaWagneri ; g, g. germigenes ; n,
nucleus of the axial cell ; b, the spherical germ of Dicye- the GrTeffarinSB to
inella, with its striated nucleus ; c, the same beginning
to undergo self-division ; d, final stages of self-division
imorula) ; e and f, infusoriform embryo; h, germs of
the vermiform embryos of Dicyema typus ; i, gastrula
of the same ; k, I, m, o, different stages of vermiform
larvae of Dicyema typus, all highly magnified. — After E.
Van Benedeu.
wait for more light
on the development
of the parasitic
P 1 a t y h e 1 m i n t h
worms. It is not improbable, on the one hand, that the
DicyemidcB, retaining their parasitic life, are retrograde
forms, which have originated from some low Cestoid or
Trematode worm, and bear the same relation to them, the
FLAT- WORMS. 1)9
Cestoids especially, which have no body-cavity, as the Tar-
digrades or Linguatulce do to the higher Arachnida.
Each species of Dicyema and Dicyemella (Fig. 62) com-
prises two sorts of individuals, differing externally, one (the
Nematogene) producing vermiform embryos, the other
(Rliombogene) infusoriform (but many-celled) young. The
Nematogenes produce germs which undergo total segmen-
tation, and assume a gastrula condition. After the closure
of the primitive opening, the body elongates, and the worm-
like form of the adult is finally attained, when it passes
through the body- walls of the parent.
The germs of the Rhombogenes arise endogenously in
special cells lodged in the axial cell, and called " germi-
genes." The germ-like cells undergo segmentation, and
then form small spheres, which become infusoriform em-
bryos. The worm-like young is destined to be developed
and live in the Cephalopod where it has been born, while
the infusorian-like young probably performs the office of
disseminating the species. It is possible that in those ani-
mals, such as the Cetacea, which feed on cuttlefishes, these
worms (the Nematogenes at least) may pass into a genuine
vermian form.
CLASS I. — PLATYHELMINTHES (Flat-worms, Tape-worms,
Fluke-worms, etc.]
Order 1. Turbellaria. — In any pond of standing water
-one can find on the under side of sticks or stones, small
dark flat worms. These are Planar i an
worms. The common dark-brown,
almost black Planar ia torva Miiller
(Fig. 63) is about six or eight milli-
metres long, oblong, flat, with two
black eye-spots, with an oblong oval Fig. 63. Fig. ei.
space in front of each eye. A form t&rv£.a p/mv'///''''
.allied to this is a perfectly white Plana-
rian called Dendroccelum lacteum Oersted, which lives under
100 ZOOLOGY.
submerged stones, sticks, and leaves in ponds. The body
is partly transparent, with a dark area representing the
stomach, from which branch out at right angles a multi-
tude of coecal canals (gastric cceca). It has two small
black eye-specks. Closely allied to this flat worm is an eye-
less form inhabiting the streams of the Mammoth and ad-
joining caves, which may be called Dendrocmlum percwcum
(Fig. 64).
The foregoing forms are easily obtained by the student,
who can study their habits in confinement. They all be-
long to the order Turbellaria, which is characterized by the
flat, oval body, covered with cilia. The ciliary motion can
be detected, as Moseley has clone, by placing a little arrow-
root meal or fine bits of paper on the back of the animal ;
these were seen to move in a forward direction on the an-
terior part of the body of Geoplana flava Moseley, a Bra-
zilian land -planar ian, and posteriorly they moved backward.
" In all regions of the dorsal surface it moved outward,
as was observed by Fritz Miiller, at the same time as back-
ward or forward, and was thus rapidly thrown off at the
side of the body, the dorsal cilia apparently subserving
especially this function of the speedy removal of foreign
substances from the surface of the body " (Moseley). The
structure of the flat worms may be understood by referring
to Fig. 65, which illustrates the anatomy of a common
European marine flat-worm. The digestive canal opens by
a mouth situated usually behind the middle of the body,
which leads into a chamber containing a cylindrical or
funnel-shaped proboscis, capable of being suddenly thrust
out. The digestive canal is either a short blind sac, or is
long, forked, and either simple or much branched (Fig.
65, e).
These worms have a so-called water-vascular system, con-
sisting of two lateral canals and numerous branching lat-
eral stems, with a common opening or pore in the skin be-
tween the two main stems, or there may be many pores.
The vessels are ciliated within, and are supposed to have a
respiratory or excretory function. The nervous system con-
sists of a double ganglion situated on the front end of the
PLANARIAN WORMS.
10 L
body (Fig. Go, /), from which nerves pass in different
directions, but a true nerve-cord is not known with cer-
tainty to exist.* The eyes are very simple, indicated by
two or more, sometimes
thirty, dark pigment spots.
In certain forms, such as
Macrostomum, there is a ru-
dimentary ear (otocyst).
Most of the Planarians,
land and aquatic, have organs
of defence in the form of
minute, stiff rods, either
coiled up in an irregularly
spiral manner, or short and
straight, contained in oval
cells. These bodies are shot
out in great numbers when
the animals are irritated, but
are not retractile, being pro-
jected clear from the skin.
In being neither retractile
nor barbed, they differ from
the lasso-cells of the jelly-
fishes. That, however, they
are true urticating organs
has been proved by Mr.
/'of flin en rrrmci ''rv e'lg- 00-~ foii
(at tllC suggestion ft, buccal cavity
of Mr. Moseley), who, on
touching certain
laevirjatn. a, mouth ;
oesophageal orilice ; d,
stomach ; e, branches of ihe stomach ; /,
ganglia ; (/, testes ; //,, vesiculse seminales ;
i, male genital-canal ; A-, oviducts ; I,
sperm-sac; m, opening into the oviduct.
land - planarians with his -AfterQuatrefages.
tongue, felt an unpleasant tingling or scalding sensation,
accompanied by a slight swelling.
* Schmarda describes the nervous system of Bipalmm deiidrojiliihix
as formed of two pairs of ganglia, from the hinder of which arise two par-
allel nerve-threads, which dilate into at least nine swellings. Moseley
discovered no more than one pair of ganglia in the species of Bipalium
he examined. Blanchard has demonstrated "successive ganglionic
repetitions along the nervous-threads at the right and left sides of the
mid-line of the body of a large Planarian (Polydadus Oayi Blanch.)." —
Clark's " Mind in Nature," p. 253.
102 ZOOLOGY.
The Turbellaria are hermaphroditic, the ovaries and testes
with the accessory apparatus (Fig. G5) being present in the
same individual ; but in many forms the sexes are distinct.
Little is known of UK- development of the flat-worms.
In a common marine Planarian, Stylochus elliptica (Girard),
which is about two centimetres long, and lives under stones
between tide-marks, north of Cape Cod, the eggs are depos-
ited in May and June, in a thin, viscid band, on stones and
sea-weeds. The eggs undergo total segmentation in four or
five days after they are laid. The larva is round, ciliated,
with a caudal flagellum. In eight or ten days after the
larva has hatched, it stops swimming about, and becomes a
"mummy-like body,'' which Girard calls a "chrysalis."
In this state it floats about in the water. Its further his-
tory is unknown.
In Lcptoplana (Polycelis), according to Keferstein, the
yolk undergoes total segmentation as in Stylochus ; the
outer layer of cells forms a blastoderm which surrounds the
more slowly growing cells within. Keferstein describes
and figures the various stages by which the spherical cili-
ated embryo attains the form of the adult, whose devel-
opment seems to be less in the nature of a metamorphosis
than that of Stylochus.
The Planarians also in some species mul-
tiply by fission, and when cut into pieces,
according to H. J. Clark, each piece may
eventually become a Avell-formed Planarian.
Clark figures in his " Mind in Nature" two
Planarians derived from two sections of
Dendroccelum lacteum, which became fully
developed within eleven days after the opera-
tion. Several Turbellarians are known to
undergo spontaneous fission.
Catemila lemncB Duges, by transverse di-
- visi°n> forms chain-like aggregations, and
. .
la _q,,,,ter»a iimier- a South African species, C. quaterna, of
going self -division. * . •*
—After schmarda. Schmarda, has been found by him to have the
same habit. Fig. CO represents two individuals (much
enlarged) in partial division, a'nd a chain of five individ-
LAND PLANARIANS.
103
tials, natural size. The same process of strobilation has
been carefully observed by Graff in Microstomum lineare
Oersted. In the chain of four individuals (Fig. 67) I indi-
cates the division of the first order, and II those of the
second order ; at the points in the zooids marked III there
are indications of a future third subdivision, and at IV of
a fourth ; so that potentially the chain con-
sists of sixteen zooids,- and the division is
first indicated in the digestive tract which
forms subdivisions with septa reaching to
the body-walls, while secondary and tertiary
mouth-germs appear in the division-sections
« m", Fig. 67).
Huxley in his Manual of the Anatomy of
Invertebrated Animals states that in some
genera of Turbellariaii worms "a difference
is observed between the eggs produced in
.summer, which have a soft vitelline mem-
brane, and those produced later. These so-
called winter ova have hard shells.
The genuine flat-worms are divided into
two suborders : Pliabdoccela and Dendroccela.
In the former group there is an extensible
pharynx, and the digestive tract is not
branched. The Rhabdocoela are represented
by Catenula, Prostomum, Microstomum, etc.
The Dendroccela sometimes have two tenta-
cle-like continuations of the front end of the
body. The digestive canal has one anterior, two
posterior large, and many secondary branches, Fig. 67.— strobi-
and a proboscis. Here belong the Planarians gton"^ M«W)O-
m'
n
of fresh and salt water, and the Geoj)lanid(B
or land-planarians, represented in the United
States by Rhyncodesmus sylvaticus Leidy. The only para-
sitic species of the order known are Stimpson's Cryptocce-
luin opacum, which infests the sand-cake (Echinaracltnins
parma), and Typhlocolax acuminata, which lives on a Holo-
thurian (Chirodota) ; while Semper has described Anoplo-
•dium Schneideri. which lives in the intestines of Stichopus
104 ZOOLOGY.
variegatum and Mnlleria lecanora, two East Indian Holo-
thurians.
The Planarian worms merit careful consideration, as it is
possible that the Mollusca have originated from primitive
forms resembling them.
Order 2. Trematodes,. — Having studied the Planarians,
we shall be able to appreciate the characteristics of the Tre-
matode worms, which are all parasitic, and are constructed
on the dendrocoelous planarian type, more or less modified
by their parasitic life, some being external, but most of
them internal parasites. They closely agree with the Tur-
liellaria in form, never being segmented. The mouth-open-
ing is usually situated near the fore-end of the body (some-
times in the centre), leading by a muscular pharynx to the
digestive canal, which is forked and ends in two coeca. Uni-
cellular glands open into the pharynx. In one genus (Ani-
philina) there is no digestive canal.
The Trematodes usually possess what the Turbellarians
do not have, a sucking-disk (Fig. 68, B, ,s), situated a little
behind the middle of the body, by which they adhere to the
walls of the organ of the host they inhabit. The so-called
water-vascular* or excretory system forms a network of
vessels branching from two main lateral tubes, which unite
to form a contractile vesicle ending in a terminal pore, or
the main branches may end in two or more lateral pores.
The fact that there is no anal opening seems to confirm
the idea that the water-vascular system is excretory, thus
affording the only outlet for the waste products of diges-
tion. There are no blood-vessels or respiratory organs, and
the surface of the body is not ciliated except in the embryo.
The nervous system is usually represented by a single gan-
glion, like that of the Turbellarians. Eye- spots are some-
times present in the young, which, with other points in their
organization, tends to show that the Trematodes have origi-
nated from Turbellaria, having been modified by their para-
* That the so-called water-vascular system is mainly at least excretory
In its function seems proved by the fact that the fluid is watery and
contains granular concretions, thus resembling the urinary excretions
of the higher animals.
STRUCTURE OF FLUKE-WORMS. 105
Bitic life, and with somewhat the same relations to Turbella-
rians as Lernaean parasites have to the normal Copepoda, or
water-fleas.
There is always one sucker which usually encircles the
mouth, the other (ventral) sucker varies in position, and
sometimes there is, as in the externally parasitic Polysto-
initlcB (Aspidogaster, Polystomum, etc.), a sucker on each
side of the mouth-opening. In some forms there are two
large chitinous hooks in the median line between the hinder
suckers, of which there may be several.
The reproductive glands are more or less complicated, and
are much as in the Turbellarians. The eggs are formed (as
in Cestodes, Turbellarians, and Eotifers) by two distinct
glands, a gcrmigcnc and a vitellogene, the latter forming the
nutritive mass which envelops the protoplasmic germ or egg
proper, the entire mass being afterward enveloped by the
egg-shell. Frequently two or more eggs are enclosed in
one shell. The species are mostly mono3cious, the external
opening of the oviduct and the large intromittenfc organ
being contiguous.
The development of the egg begins by subdivision of the
nucleus ; the nucleolus then divides, and subsequently the
protoplasmic mass. The yolk, however, remains entirely
independent of this division, and serves as nourishment for
the other cells forming the body of the embryo. From E.
Van Beneden's observations it appears that the eggs of the
lower flakes, as a rule, undergo total segmentation, and the
young of the Dixtoinew are hatched in an oval ciliated
" trochosphere ' form, without eye-specks, as in Distoma
and Amphistoma ; or, as in the Polystomece, there is no meta-
morphosis, but development is direct, the embryo passing
directly into the adult condition.
It was not known before the publication of Steenstrup'a
work in 1842 that certain worms called Cercarice were the
free larval forms of the Distomes. The Cercaria ecliinata,
first described by Siebold, is like a Distomum, except that
the body is prolonged into a long extensible tail. This tail,
says Steenstrup, is formed of several membranes or tubes
placed one within the other, of which the outermost is a
106
ZOO LOG Y.
very transparent epidermis, under which is a tolerably thick
membrane furnished with transverse muscular fibres, while
between each pair of these transverse fibres is placed a globu-
lar vesicle which appears to be a mucous follicle or gland ;
the innermost tube is opaque and of firmer consistence ; it
contains the longitudinal muscular fibres, and is usually re-
ticulated on the surface. Through the centre of these tubes
there passes a slightly narrower canal, which becomes very
small toward the extremity of the tail. The existence of
the same layers in the body itself of the Cercaria can easily
be demonstrated ; but the transversely striated layer is here
not so much developed.
Steenstrup states that these Echinate Cercaria? (Fig. 68}
Fig. 08. — Metamorphosis of a Cercaria into a Distomum. A, parent nurse ; <•, germs ;
a, nurse. B, larva. C", encysted, pupal Cercaria. D, adult Distomum.— After
Steenstrup.
are found by thousands, and frequently by millions, in the
water in which two of the largest European fresh-water
snails, Planorbis cornea and Limncvus stagnalis, have been
kept. After swimming about in the water some time, they
fix themselves by means of their suckers (B, s) to the slimy
skin of the snails, in such numbers that the latter look as if
covered with bits of wool.
The Cercaria, by contractions of its body and violent lash-
ing of the tail, forces its way into the body of its host, loses
its tail, and then resembles a mature Distoma. By turning
LIFE HISTORY OF FLUKE -WORMS.
107
about in its place and secreting a slime, a cyst is gradually
formed, with a spherical shell. This constitutes the " pupa ';
state of the Cercaria. Steenstrup thinks that the Cercaria
casts a thin skin. In this state the body can be seen through
the shell of the cyst, as in Fig. OS, C, where the circle of
spines embedded around the mouth is seen. The encysted
Cercarias remain in this state from July and August until
the following spring ; and during the winter months, in
snails kept in warm rooms, they change into Distomas (Fig.
68, D), the niatura fluke differing, however, in some im-
portant respects from the tailless larva. In nature they
remain from two to nine months in the encysted state.
" Now," asks Steenstrup, " whence come the Cercariae ?"
Bojanus states that he saw this species swarming out from the
" king's vellow Avorms " which are about two lines long and
O *i
occur in great numbers in the interior of snails. From these
are developed the larval Distomes, and Steeustrup calls them
the " nurses " of the Cercarire and Distomes. They exactly
resemble the "parent-nurses" (Fig. 68, A, and 70), and,
like them, the cavity of the body is filled with young, which
develop from egg-like balls of cells. Steenstrup was forced
to conclude that these nurses originated from the first nurses
(Fig. 68), which he therefore calls " parent-nurses." Here
the direct observations of Steenstrup
on the Cercaria echinata came to an
end, but he believed that the parent-
nurses came from oggs. The link in
the cycle of generations he supplied
from the observations of Siebold,
who saw a Cercaria-like young (Fig.
69, B) expelled from the body of the
ciliated larva of Monostomum muta-
bile. Steenstrup remarks that " the
first form of this embryo is not un-
1.1 ,1 » ,1 -i- _,n „ onostomum. . cate arvf;;
like that of the common ciliated pro- m mouth . b_ eyeg ; a, nurse,
geny of the Trematoda, as they have B>™™
been known to us in many species for a long time, and it
might at first sight be taken for one of the polygastric in-
fusoria of Ehrenberg, which also move by cilia ; whilst in
- a.
Fig. 69.— Development of
Monostomum. A. ciliated larva;
108
ZOOLOGY.
the next form which it assumes the young Monostomum
bears an undeniable resemblance to those animals which
I have termed ' nurses ' and ' parent-nurses ' in that species
of the Trematoda which is developed from the Cercaria eclii-
nata."
Thus the cycle is completed, and the following summary
of changes undergone by the Distomes present as clear a
case of an alternation of generations as seen
in the jelly-fishes :
1. Egg.
2. Morula.
3. Ciliated larva.
•i. Redia (parent-nurse, Proscolex) produc-
I
ing
5. Cercaria (nurse, Scolex).
6. Encysted Cercaria (Proglottis).
7. Distomum (Proglottis).
The Distomum echiuatuni (Fig. 70). living
in snails which are eaten by ducks, have been
shown by St. George to develop into the adult
Distoma in the body of that bird. It is gen-
erally the case that those Distomes which pass
through an alternation of generations live in
the larval state in animals which serve as food
for higher orders. Thus the Bucephalus of
the European oyster passes in the encysted
state into a fish which serves as food for a
larger fish, Belone vulgar is, in whose intes-
same worm, a species
The American
ri»ed-EWCGer" oyster is infested by Bucephalus c/rrttlits Ma-
vaisandBeneden. crady. It infests the ovary of the oyster.
Whether it is permanently injurious to the latter is un-
known.
Fasciola hepatica (Fig. 71). the liver-fluke, sometimes
occurring in man, causes the "liver-rot" in sheep, etc. In
the winter of 1879-80, it was so prevalent in Great Britain
that 3,000,000 sheep were destroyed by it.
It is most abundant in sheep in the spring, several hundred
Kig. 70 —Pro- , • ' ,-, j i, , ,,
iex or parent- tine the adult oi the
mum echi>w™!m °f Gastcrostomum, occurs.
HABITS OF FLUKE -WORMS.
109
occurring in the liver of a single sheep. At this time it passes
into the intestine, and thence is carried out with the excre-
ment. The eggs or flukes in many cases drop
into pools, ditches, or ponds ; here the cili-
ated young (like Fig. 69) is liberated. Its
body is spindle-shaped, with a double eye-
spot. It is very active, and soon after birth
enters the body of a snail (LimncBus),
where it transforms into a large sac, and
develops new larvas in its interior. This
sac-like larva is called a ''nurse," "sporo-
cyst," or, when more highly developed, a
" redia. ," The progeny of the redia is
termed a " cercaria. " The cercarise are
restless, migrating from the bodies of their
snail-host, and have been known in a few
instances to penetrate the skin of human
beings. They are probably more usually
swallowed by sheep and cattle while drink- kepatica.ei
ing or grazing, when snail-shells may be Fromb<ferva
accidentally swallowed. From the diges- Benedeu-
tive canal of sheep, etc., the cercaria penetrates into the
liver, where it probably loses its tail and becomes encysted,
after many weeks or even months becoming a sexually ma-
ture distome. From the liver it passes out through the
liver-ducts into the intestine, and is finally expelled, thus
completing its cycle of life.
Distomum lanceolatum Mehlis differs from Fasciola he-
patica in the intestine being simple and forked, while that
of the latter is much branched. It has occurred but three
times in man, but is not rare in the sheep and ox. It has
been detected in Europe in the pig, deer, rabbit, and hare.
Two immature Distomes have been found in the human
eye, and Cobbold thinks they may both be the young of
D. lanceolatum. It is described by Biesing under the name
of Distomum oplithalmolium, is half a line in length, and
occurred between the lens and its capsule, appearing as dark
spots on the surface of the lens. Distomum crassum Busk
and D. heterophi/es Siebold have each been only once
110 ZOOLOGY.
found in man, the former in a Lascar, the latter in an
Egyptian boy.
Bilharzia hcematobia Cobbold is common in the portal
system of blood-vessels and in the veins of the mesentery,
bladder, etc., of Egyptians, and has caused an endemic dis-
ease at the Cape of Good Hope. In Egypt, out of three
hundred and sixty-three post-mortem examinations, this
worm occurred one hundred and seventeen times. It is
bisexual, the female greatly smaller than the male, living in
a canal or passage in the male formed by the infolding of
the edges of the concave side of the body, called a gynceco-
pliore. There are three other rare human flukes known :
Tetrastoma renale Delle Chiaje, Hexathyridium pinguicola.
Treutler, and //. venarum Treutler, the latter occurring in
the veins (Cobbold).
The nurse of Distomum macrostomum Rudolphi (Fig.
72), described under the name of Leucoeliloridiiim, is
cylindrical, and strongly resembles a maggot ; its strange
habitat is the tentacles of a snail (Succinea).
Of the second suborder, Polystomece, the species have two
small anterior and one or several posterior suckers, and a
pair of eyes. They are
mostly external parasites,
like the leeches, and un-
dergo no metamorphosis.
In some forms the body
is segmented.
A type of this suborder
is Aspidogaster conclii-
Fip. 72 — 1. Lntcochlnridi'im paradoxum, 7 T> i • i • i i -.L
living In the tentacles of Succinea; 2 A full- COM i>aer, WhlCll inhabits
grown nurse-Leucochloridiinn with the nurse- ,1 • j- ^ £.
stock from which it has sroun. Natural size. the pei'lCai'dUll Cavity OI
— After Zeller. » T , ,
fresh-water mussels, and
also is an ectoparasite of fresh-water fishes. Diplczoon
consists of two Trematodes very intimately united into an
X -formed double animal. In the young stages the two ani-
mals are separate, and in this state were described under the
name ofDiporpa. Diplozoon paradoxum Nordmann lives on
the gills of numerous fresh-water fishes. Polystomum has
a flat body, without suckers on the fore end, with six suck-
STRUCTURE OF TAPE -WORMS. Ill
ers and two large median ventral hooks on the hinder end.
The ripe eggs are deposited in the water in winter, when
the ciliated young, with four eyes and without suckers, find
their way into the gill-cavities of tadpoles, whence, during
or after metamorphosis, they pass into the urinary bladder
of young frogs ; P. integerrinuun Rudolphi lives in that
of Rana temporaria (Glaus' Zoologie).
A case of budding or parthenogenesis is said to occur in
the genus Gyrodactylus. This is a very small Trematode
with a large terminal disk, bearing a peripheral set of pow-
erful hooks, with two long curved median spines. The
body of the hermaphrodite worm shelters a daughter, a
granddaughter, and great-granddaughter generation. G. ele-
gans Nordmann lives on the gills of Cyprinoid and other
fresh-water fishes. Dactylogyrus lays eggs, not being par-
thenogenetic ; it has four head-flaps. D. amphiboihrium
Wagener lives on the gills of the stone-perch ; D. fallax
Wagener on Cyprinus rutilus.
Order 3. Cestodes. — The common tape-worm is the type
of this order. Specimens may be procured from physicians,
and a careful examination of cross-sections and ordinary
dissections will convince the student that the tape-worm has
no mouth, although a head armed with suckers or hooks.
The body is divided into an enormous number of segments
or proglottids, but there is no digestive canal, the worm
living immersed in the contents of the intestines of its host ;
its food being absorbed from the juices of its host through
the walls of the body.
The tape-worms and their allies have recently been found
by Dr. Lang to possess a nervous system. The water-
vascular system is well developed in the Cestodes, where it
seems to be excretory in its functions, as in the Trematodes.
There are usually four, sometimes only two, longitudinal
canals, which are connected in the head and in each segment
with transverse anastomosing branches, while from these main
canals a network of fine vessels branch out. Granules and
whitish chalky deposits occur in the canals, and these con-
cretions, like similar bodies in the excretory canals of Tre-
matodes, seem to have, Leuckart claims, a relation like that
112 ZOOLOGY.
of the crystals of oxalate of lime in the urinary tubes of
many insects and the concretions of phosphate of lime in
the organ of Bojanus of Lamellibranch mollusks.* The
canals terminate in a small pulsating vesicle and pore, as in
the Trematodes.
The Cestodes are hermaphroditic, and each of the body-
segments except those nearest the head contains male and
female reproductive organs. The male parts consist, as in
the Trematodes, of testes, vasa defer entia, and a muscular
sac with a cirrus or intromittent organ, which may penetrate
the vagina of the same segment. The female organs consist
of an ovary (germigene), yolk-stock (vitellogene), uterus or
matrix, receptaculum serninis, and vagina, the latter opening
by a pore situated in Tcenia (Fig. 77) on the side, or in
Bothriocephalus on the ventral surface of the segment.
There is a great deal of variation in the reproductive organs
of the tape-worms; a general idea of the relations of parts
may be obtained by reference to Figs. 77 and 79. The
ovary forms the most important part. It is much devel-
oped and very complicated in structure. As Gegenbaur
states : " The preservation of the species is here subject to
innumerable difficulties, owing to the animal living in dif-
ferent hosts at different stages of development, and to the
wanderings which this mode of life entails ; consequently a
large number of ova have to be produced, and the cer-
tainty of fecundation insured." (Elements of Comparative
Anatomy, second edition, English translation.) The
male organs and products are first developed, and the
receptaculum seminis stored with spermatic cells before the
eggs fully develop in the ovary, and all these parts develop
earliest in the terminal segments of the body destined to
form the proglottides.
Development begins very probably, as in the Trematodes,
»
* This is Leuckart's opinion. Sommer and Landois claim that these
bodies are scattered through the substance of the body, and do not
occur in water-vessels. Huxley endorses this view. But if these bodiea
are concretions and the water-vessels are mainly excretory, as they ccr.
tainly appear to be, we should judge that Leuckart's view was the bet-
ter grounded.
DEVELOPMENT OF TAPE-WORMS.
113
through multiplication by division of the nucleus (germi-
aative cell). In the eggs of Tcvnia lacillaris E. Van Beneden
Fig. 73. — Tcenia solium. Nat. size,
with the head magnified. Strobila stage.
— After Beneden.
Fig. 74.— Head and proglottisof
T. xolium. — After Beneden.
saw the nucleus subdivide ; after passing through a morula
condition the cells are arranged in two layers, and the outer
1U ZOOLOGY.
layer is thrown off (this probably corresponding to the serous
membrane of insects and Crustacea) ; the central mass
(which is not hollow as in the gastrula of other worms, a
digestive cavity not being present in after life) forms the
embryo, and soon three pairs of hooks arise. Three struc-
tureless membranes are secreted around the embryo, which
then hatches. The embryo of Bothriocephalus is provided
with a ciliated membrane, which corresponds to the first
blastodermic moult of the embryo Taenia, which, on the
other hand, is not ciliated.
The history of the human tape-worm, Tcenia solium (Fig.
73) is as follows : the eggs eaten by the hog are developed
in its body into the larval tapeworm (scolex), called in this
species Cysticercus cellulosce (Fig. 75 ; Fig. 70, head en-
larged). The head with its suckers is formed, and the
body becomes flask-shaped; the Cysticerci then bury them-
selves in the liver or the flesh of pork, and are transferred
living in uncooked pork to the alimentary canal of man.
The body now elongates and new joints arise behind the head
until the form of the tapeworm is attained, as in Fig. 73.
The hinder joints then become filled with eggs and break
off, becoming independent zooids comparable with the
" parent-nurses " of the Cercarias, except that they are not
contained in the body of the Ta?nia (as in the Cercaria), but
are set free. The independent joint (Figs. 74, 75) is
called a " proglottis. " It escapes from the alimentary tract
of its human host, and the eggs set free, in and about
privies, are swallowed by that unclean animal, the pig, and
the cycle of generations begins anew. We thus have the
following series of changes, which may be compared with
the homologous series in the flukes :
1- Egg.
2. Morula.
3. Double- walled sac (gastrula ?).
4. Proscolex, free embryo with hooks, surrounded by a
blastodermic skin.
5. Scolex (Cysticercus, larva). Body few-jointed.
6. Strobila (Taenia). Body many-jointed.
7. Proglottis (adult). .
INJURIES CAUSED BY TAPE -WORMS. 115
The common human tape-worm, Tcenia solium Linn.,
varies from ten to thirty feet in length ; there are upward
of eight hundred joints in a worm ten feet long. The head
ends in a rostellum or proboscis armed with a double crown
of hooks ; the first proglottis or sexually mature segment
begins at the 450th. While in some persons the presence
of a tape-Avorm is simply an annoyance, in nervous and irri-
table persons it causes restlessness, undue anxiety, and vari-
ous dyspeptic symptoms. In rare cases (over a hundred are
known) death has resulted from the presence of the Cysticer-
Fig. 75.—
cercus, or larva)
Tape-worm.
Fig. 76.— Head of Taenia acanthotrias (Cysticercus)
enlarged, showing the suckers (S) and circle of hooks.
cus in the brain. " Cysticerci may develop themselves in
almost any situation in the human body, but they occur
most frequently in the subcutaneous, areolar, and intermus-
cular connective tissue ; next, most commonly in the brain
and eye ; and, lastly, in the substance of the heart and other
viscera of the trunk " (Cobbold). Among the preventive rem-
edies against tape-worms is the disuse of raw or underdone
pork, and " measly" pork — i.e., the flesh of swine contain-
ing the little bladder-like vesicles. Cysticerci, or lar\al tape-
worms, can be readily distinguished, but when thoroughly
cooked are harmless, as the temperature of boiling water is
116
ZOOLOG T.
sufficient to kill the Cysticerci. Butchers especially suffer
from tape-worms, from their habit of eating bits of raw
meat, beef and veal harboring Cysticerci, which transform
into species of Teenia nearly as injurious as Tcenin xolittii/.
*/ V
As a matter of course, in the use of drugs to expel a tape-
worm, they should be pushed so as to carry off the entire
animal, as new segments grow out from near the head as
rapidly as the proglottides are detached.
The Cysticercus of another injurious tape-worm lives in
the muscles and internal organs of cattle. This is the To.' nix
mediocanellata of Kiichen-
meister, which is larger,
with a larger darker head,
<i larger suckers, and with-
out a rostrellum or hooks.
By far the most injurious
species is Tccnia efJiinonn--
cus SioboUl (Fig. 7S),
a more frequently causing
death than any other en-
tozoon. In its adult or
stroMla state this worm
only infests the dog and
wolf, but its larva, the
hydatid of physicians, fre-
quently occurs in the hu-
man body. It is very
d small, seldom exceeding
six millimetres in length,
there being but four
segments, including the
FiK. 77. -Proslottis of T. soiium. a, tcstis : head, which has a pointed
b. sperm duct: c. orifice of cirrus; d, matrix v.-.cfpllnm with i rlnnhlf
tilled \vith e^s ; e, vagina ;/, sexual cloaca.— 10ST im, W1U1 a (
After Beueden. crown of large-rooted
hooks ; there are four suckers present, and the last segment,
when sexually mature, is as long as the anterior ones taken
together. The hydatid (proscolex] forms large proliferous
vesicles, in which the scolices (Echinococcus heads) are de-
veloped by budding internally. About five thousand eggs
HYDATIDS.
117
are developed in a single segment (proglottis). The six-
hooked embr}ros develop, are expelled from the dog, and
find their way in drinking-water or in food into the human
intestines, whence they bore into the liver, their favorite
habitat, or are carried along the blood-vessels into some
other organ, where they develop into bladder-like bodies
called acephalocysts or hydatids. In its
earliest stages the hydatid is spherical and
surrounded by a capsule of condensed con-
nective tissue of its host. By the fourth
week the young T. cchitiococctis is one half
a millimetre (one-fiftieth inch) in length,
and it is probably many months before the
Echinococci heads are entirely developed.
When this stage is reached the tape-worms
become sexually mature in from seven to
nine weeks after, when the milk-white
worms may usually be found embedded in
the mucus of the duodenum and upper
part of the small intestines, with their
heads attached to the villous surface of
the intestine. The hydatids or cysts in
which the Echinococci develop are of
three kinds — viz., exogenous, endogenous,
and multilocular, and lie embedded in the
parenchym of the liver, etc., and are tilled
with a clear amber-colored fluid. The
Echinococcus heads, first on the inner sur-
face of the cyst and in the interior of the
Echinococcus-head (brood-capsule), devel-
ops a second brood of scolices, contained
. T TV 11 FiS- 78. — Tcenia
in a secondary cyst. finally, a tertiary ecMnococcm . -- After
cyst, containing tertiary or granddaughter
scolices, arises. Sometimes the secondary hydatids will de-
velop scolices and granddaughter vesicles before the original
maternal hydatid has acquired Echinococcus heads (Cob-
bold).
The largest human tape-worm is Bothrwcephalus latu&
Bremser (Fig. 79).
118
ZOOLOGY.
This worm is extremely rare in America, but is common in
Western Switzerland and Central Europe, and in the north-
western and northern provinces of Russia, Sweden, and
Poland. It is sometimes twenty-five feet long, and nearly
an inch broad, with 4000 joints. The club-shaped head is
unarmed, and the first sexually mature segment is about
'Pig. .9. — Male reproductive organs, with parts of the female of BothriocepJinJns
Intus. t, testicular follicles, only ;i part are represented : ve. their excretory ducts;
vd, vas deferens : c, cirrus ; cb, sac containing the cirrus ; //. ntrru< ciuitiiiuiuir eui;s ;
»(j. ovary ; gl, shell-gland ; e. water-vascular trunks ; v, vaginal canal.— After Lanooia
and Sommer ; from Gtegenbaur.
the 600th from the head. Leuckart has suggested that
the young of this tape-worm originate in salmon and
trout.
The sheep-hydatid is the larva of Twniti ccenitnis (Figs.
SO and SI), the adult infesting the dog. The presence of
one or several of the hydatids in the brain of the sheep pro-
duces the " staggers " or vertigo. The vesicle varies in size
from a pea to a pigeon's egg. It is bladder-like, filled with
.a clear pale yellow albuminous secretion, with a great num-
ber of retractile papillae (D, //), which arc the tape-worm heads
^connected by narrow stalks to the common vesicles support-
HTDATIDS OF THE SHEEP.
I 1!>
ing the colony. This hydatid also infests cattle, the horse,
goat, various species of antelope and deer, the dromedary,
and, it is said, the rabbit. " In the sheep the disease is rec-
ognized at first by a heavy, stupid, wandering gait, which
Fig. 80. —.4, brain of a sheep which three- weeks previous had wallowed some egge
of T . ccp.niirus. and which was killed after having shown all the symptom* of " stag-
gers." B b, isolated gallery formed by the worm at the surface of the brain, (be sco-
lex being found at the end of the gallery. Be. vesicle (proscolexl before the birth of
the scolex. B d. vesicle in which the* scolices will appear, d, vesicles whirh have
produced some scolices. D. the hydatid vesicle containing gcj. the secondary vesicles.
E. scolex of T, c<»nnrus. corresponding to a secondary vesicle D f?, and very much
magnified and invaginated. </. point at which the head of the worm will issue out ;
!>. pi lint of junction with the hydatid vesicle ; c, hooks ; d, the suckers ; e, the neck ;
/, the wall of the hydatid cyst.'— After Beneden.
is frequently succeeded by irregular, tortuous, whirling
movements of the body, accompanied with convulsions (Cob-
bold).
The simplest form in the order is CaryopliyllcBUS, in
which the body is not jointed in the adult, though it is so
120
ZOOLOO Y.
,
Fig 81 —Head of T. ccenunis seen from
in the young, and there are no suckers or hooks ; while
there is but a single set of male and female reproductive
organs situated in the posterior end of the body, which can
be detached from the ante-
rior part of the body, form-
ing a proglottis. In fact,
this form is a connecting
link between the Trematoda
and Cestodes. CaniopltiiUceus
— . , . ..*'
above, with circle of hooks ; a—e, hooks ; mutaMUs Rlldolphl llVCS in
all much enlarged.— After Siebold. . .,
the intestines of Cyprmoid
fishes ; the young in a worm, Tubifex rivulorum.
Tetraryhnchus is provided with four very long slender
extensile spiny cephalic processes or beaks. The young live
encysted in bony fishes, the adults occurring in the intestines
of sharks and rays.
In Ligula the body is ribbon -shaped, not jointed, with a
series of sexual organs, and there are no suckers, and some-
times no hooks. L. simplicissima Eud. lives in fishes and
amphibians, and attain maturity in the intestines of water-
birds, which feed on the former animals. This genus con
nects the simpler tape-worms with Botliriocephalus and
Tcenia.
CLASS I.— PLATYHELMINTHES.
More or less fattened rearms, with the body usually unsegmented ; the
Tiead in the Cestodes often armed with hooks or suckers. Simple <>r branched
(Turbettaria) or forked (Trematoda) digestive tract, but no general body -
cavity. (The digestive cavity is entirely wanting in the Cestodes.) Nervous
system repn-xented by a double cephalic ganglion, with two or more nervous
cords. A system of vessels corresponding to the water-vascular system of
Echinoderms, but supposed to be mainly excretory in function. Monce-
cious, rarely bi-sexual. Ovaries differentiated info a germigene and vitel-
logene ; often, parthenogenetic, accompanied by strobilation in the tape-
worms. When alternation of generations occurs by budding, the sexual ani-
mals are united with their nurse or a sexual form into a polymorphic colony.
Order 1. Turbettaria.— Flattened ovate worms, with a nervous gan-
glion in the head ; usually eye-specks ; body externally cili-
ated, with a much-branched digestive canal. Nettling
organs often present. Bisexual, rarely unisexual; strobi
THREAD- WORMS. 1 '.' L
lation very rare ; a metamorphosis in the Dendroccela, the
larva being a trochosphere. Suborder 1. Rhabdocculu (Mo-
nocelis, Cateuula, Mesostomum). Suborder 2. Dcndrocala
(Plauaria, Dendrocoelum, Geoplaaa, and Bipalium).
Order 2. Trematwla. — Usually flat, oval, rarely cylindrical, not seg-
mented, parasitic worms, with a mouth, forked intestine,
no anus ; a large sucker near the middle of the body, or
several smaller ones ; either with a metamorphosis (Dis-
tomese), the larva living in mollusks, etc., the adult in ver-
tebrates ; or with direct development (Polyxtomew). Sub-
order 1. Distomem (Monostomum, Amphilina, Distornum,
Amphistomum). Suborder 2. Polystomete (Aspidogaster,
Diplozoon, Polystomum, Gyrodactylus).
Order 3. Cestodes. — Parasitic, usually ribbon-like worms, without any
mouth or digestive canal ; with a nervous system, and an
(excretory) water-vascular system ; hermaphrodite, the
joints (proglottis) numerous and containing male and fe-
male reproductive organs ; the eggs minute and very nu-
merous. The mature worm is many-jointed, the joints
budding out from near the head ; in this form it is called
a strobila ; the terminal joints fall off, becoming indepen
dent (proglottu). The eggs after fertilization pass through
a morula and gastrula stage, a circle of hooks and suckers
developing on the head (Caryophyllaeus, Tetrarhynchus,
Ligula, Bothriocephalus, Taenia).
Laboratory Work. — The flat worms have been most successfully
studied by fine injections, especially by slicing hardened sections,
which should be stained with carmine, and mounted for the micro-
scope.
CLASS II. — NEMATELMINTHES (Round, Thread-worms).
General Characters of Thread-worms.— These worms are
either free or parasitic ; examples of the former exist in
abundance under stones, etc., between tide-marks, lying
in coils ; small, almost minute species occurring in fresh
water and in damp earth, while the parasitic species, which
are the rno^t numerous, live free in the alimentary canal or
imbedded in the flesh of their hosts, especially fishes and
mammals. The species are remarkably persistent in form,
ZOOLOGY.
the specific and generic differences being very slight. They
have a mouth and digestive canal (except in Echinorhynchus),
the integument being hard, chitinous, and not segmented
(except in Desmoscolex, which approaches in this respect the
annelids), and usually smooth, except in Echinoderes, which
is variously armed with hair-like spines. Each end of the
body is much alike, the mouth situated at the anterior end,
and the anal opening at or near the conical tip of the body.
There are two long vessels which extend from a single com-
mon pore situated on the median line of the under side of the
body, a short distance from the head ; these are supposed ta
be excretory vessels. In Ascaris and Oxynris a nervous ring
surrounds the oesophagus, from which two nervous threads,
one dorsal the other ventral, pass to the end of the body, and
there are six other smaller longitudinal nerves. The gangli-
onic cells lie near the nervous ring, forming a subcesopha-
geal, supracesophageal and lateral ganglion, and there is also
a caudal ganglion. In some free-living Nematodes there are
eye-specks.
The Nematodes are usually bisexual ; Pelodytes is her-
maphroditic, while the same individual of Ascaris nigrovtnosa
at first produces sperm-cells and afterwards eggs. The males
differ from the females in their smaller size and the usually
curved end of the body. While most of thes: worms lay
eggs, some, as in Trichina spiralis, bring forth their young
alive.
The mode of development of these true Nematode worms
(Echinorhynchns excepted) so far as known is quite uniform,
growth being direct, without any metamorphosis. The
germ is formed in three ways : (1) usually the egg under-
goes total segmentation ; (2) others, as in Ascaris dcntata
and Oxyuris ambigua, do not show any apparent trace of seg-
mentation, while (3) in Cucullanus elegans there is no yolk,
the nucleus absorbing all the vitelline matter, which is lim-
pid and transparent. The germ consists of a single series or
circle of cells bent on itself, somewhat as in Fig. 120, which
represents a little more advanced stage in Sagitta, and there
are a few cells representing the endoderm. The embryo
rapidly assumes the adult form before hatching.
THE ECHINOliYNCIIUS. 123
Order 1. Acanfhocephali. — These are aberrant Nematode
worms (sometimes referred to a separate class), without any
mouth or digestive tract, but with an extensible spiny beak,
living by imbibition of the fluids of the alimentary canal of
their host.
The thick subcuticula is penetrated by a network of ves-
sels, whose trunks form two oval bodies of unknown use
called lemnisci, which hang down free in the body-cavity.
The sexes of Echinorbynclius are distinct. The eggs are
usually spindle-shaped. The embryo develops in the body
of the parent worm, and is surrounded by several membranes,
with a circle of hooks arranged bilaterally around the mouth.
The embrvo contains an oval mass of nuclei, being the ru-
Fi" ^ —Ecfiinorynchus, head retracted and in the second figure extruded ; mag-
nified. «, oval pore ; b b, protnictile muscles ; c c, lemnisci.— After Owen.
diments of an intestinal canal. Finally it passes into
some crustacean or insect, in whose body it becomes so far
developed, that when its host is swallowed by some vertebrate,
such as a fish, the embryo is liberated in the intestines of the
second (vertebrate) host and soon attains sexual maturity.
Nearly a hundred species are known.
Eckinorhynchus gigas, the female of which is 50f centime-
tres (20 inches) in length, lives in the small intestine of the
pig. Its eggs pass out, becoming scattered on the ground,
where they are eaten by the white grub or larva of the Euro-
pean cockchafer. The egg-membranes burst in the stomach
of the grub, and the embryos thus liberated penetrate, by
124 ZOOLOGY.
means of their spines, through the intestine into the body-
cavity of the larva* where they become encysted, and the latter
being in the beetle state devoured by the pig, finish their de-
Telopment in the intestines of the latter animal. (Schneider.)
The embryos of this species also occur in the land-snails, and
those of E. claviceps have been found in fresh-water snails
(Limncect). Young Echinorhynclti occurring in thecopepod
crustacean, Cyclops, become mature in a fish (Gadus lota).
Leuckart lias also found that a sexless form living in a fresh-
water crustacean, Gammarus pulex, becomes developed to
sexual maturity in the perch, which feeds on the crustacean.
They attain the mature form, though the eggs are not ripe,
in eight or ten weeks after the eggs from which they hatch are
laid, and look like round or oval yellowish balls from one to
one and a half millimetres in length. The males mature in
about a week after the females.
The primary host of Echinorliynclins anynstatus is the
fresh-water sow-bug (Asellus). After the eggs find their
way into the intestines of the Asellus, the embryos, on hatch-
ing, pass through the Avails of the hinder part of the chyle-
stomach of the Asellus into the body-cavity, by means of
the embryonal, deciduous neck apparatus ; and, as in E.
proteus, the embryos lie between the chitinous walls of the
intestine and the muscular layer. The embryos are round-
ed, more or less spindle-shaped, with a so-called rudimentary
digestive cavity indicated by a central circle of cells, the
cells of the body- walls being situated in a parenchymatous or
protoplasmic mass (plasmodium), being thus comparable to
the blastoderm of some insects. The embryo is 0.09-0.1
millimetres long. The form of the body now becomes irreg-
ularly oval or cylindrical, being quite protean in shape, with
often a projection on one side of the end of the body. The
Echinorhynchns form then begins to appear, the metamor-
phosis being very marked. The first step is the moulting of
the embryo or larva, which loses its spines. After a few
weeks the Echinorhynchus form is attained, the body being
elongated, and with the reproductive organs developed, but
with no hook-apparatus. It is now 7 to 8 millimetres in
length, and almost as long as its host, the Asellus ; the males
THREAD. WORMS.
125
being smaller and shorter than the females. With the ex-
ception of the skin and lemnisci, all the parts of the adult
worm, the nervous and reproductive systems as well as the
beak, originate in the primitive
rudimentary digestive cavity,
appearing as rounded masses of
cells of like size, but differing in
structure histologically. With
the growth of the beak begins
the development of the repro-
ductive apparatus, and the hooks
are simply modified cells, with
the outer surface chitinized.
Order 2. Nematodes. — The first
suborder of this group, compos-
ing the true round worms, is re-
presented by Ascaris, Oxyuris,
Trichina, etc. The human
round worm, Ascaris Inmbri-
coides Linn. (Fig. S3), is re-
markable for its large size, and
may be recognized by its milk-
white color, as well as by the
three papillae around the mouth.
It inhabits the intestines, some-
times the stomach and oesopha-
gus, and has been known to per-
forate the walls of the intestine.
The species of Ascaris are very
numerous, infesting mammals,
and especially fish, often occur-
ring encysted in the flesh of the
cod and other edible salt and
fresh water fish, but are as a
rule harmless. Ascaris mtjxtn.r
livps thp intestines! of* the uat"™1 size ; e, the end of the body.
greatly enlarged.— After Beneden.
cat.
The common pin-worm lives in the rectum of children.
It is the Oxijuris vermicularis Linn. (Figs. 84, 85). The
Fig. 83. — Ascaris lumlricoides. it
female, natural #ize. />, heart-end en-
larged ; c, the same, front view show-
1M6
ZOOLOGY.
female is white and from eight to ten millimetres in length;
the male is only two or three millimetres long.
The largest known round worm is the palisade worm, or
Eustrongylus giyas Rudolphi, the female of which is a
Fig. 84. — Ox-
yvris vermlcitla-
ris. a, male, nat-
ural size ; b. the
same enlarged. —
After Benedeu.
Fig;. 85. —
wfrrmcHlari* . a, fe-
male, natural size ; b,
the same enlarged. —
After Beneden.
Fig. 86. - Trichocephalnit din-
par, a, malt-, natural sixe , /;,
enlarged ; c, female, natural
size.— After Beneden.
metre (about 39 inches) in length, and the size of a quill ;
the male is one third as long. It is rare in man, and occurs
especially in the intestines, and sometimes the kidneys cf
such mammals as live on fish. The mouth is surrounded
THE TRICHINA.
by six tubercles. Eustrongylus papillosns Diesing, accord-
ing to Wymuii, lives coiled up in the bruin of the unhiuga,
or snake-bird of Florida. E. buteonis Packard was found
living under the eyes of Buteo Sivainsoni, and E. chordeilis
Packard in the brain of the night-hawk. Dochmius duoden-
alix Dubini lives in the small intestine of man.
Trichocephalus dispar Rudolphi (Fig. 8G) lives in the
coeeum of man, with the smaller anterior part of the body
buried in the mucous membrane.
The most formidable round worm is the Trichina spiralis
Owen (Fig. 87). The body is regularly
cylindrical, tapering gradually from the
posterior end to the head. The end of the
body of the male is without a spiculum, but
with two conical terminal tubercles. It is
1.5 millimetres long. The female is 3 mil-
limetres in length.
Viviparous females begin about eight days
after entering the intestine of their host to
give birth to the larvae, which bore through
the walls of the intestines of their host,
passing into the body-cavity, and partly in-
to the connective tissue, and also, by means
ol the circulation, into the muscles. In
about fourteen days the worm coils up
spirall v in a cvst (Fig. 87), which eventu-
• " . . ,„, Fig. t>'t.-Tricl>it<a
ally becomes calcareous and whitish. VV lien encysted m human
, i M i .a .1 • £ i i ,1 i muscle. Greatly «»"!£•
the flesh of the pig, infested by the encysted mfied.-AiuT Leuck-
larva?, is eaten by man, the young worms !
are set free in the stomach of their new host, and in three
or four days become sexually mature. The female Trichina
is capable of producing a thousand young. The original
host of the Trichina is the rat ; dead rats are often de-
voured by pigs, and the use of raw or partially cooked pork
as food is the means of infection in man.
Another worm, occasionally parasitic in sailors and resi-
dents of the East Indies, is the Filaria medinensis Gmelin,
or Guinea-worm. It is remarkably long and slender, some-
times over two feet in length. The female is viviparous,
128
ZOOLOGY.
while the male is unknown. The worm lives in the con-
nective tissue under the skin, especially of the extremities.
As the body of the female is full of young, the worm has to
be carefully and slowly extricated, so as not to be broken and
cause the embryos to be scattered under the skin of the host.
Carter regards a small worm ( Urolubes palustris) frequent in
brackish water, as the immature form of the Guinea-worm.
It is also believed that the embryos enter the bodies of water-
fleas (Cyclops, etc.), and there moult, and that consequently
they may be introduced into the body by drinking standing
water ; but this has not been proved. Other species live in the
peritoneum of the horse and apes, and an immature species
(Filar la lentix) has been found in the lens of the human
eye. Filaria sanguinis-hominis is a worm of microscopic
size found living in the blood of the mosquito in India and
China. It is said that the eggs are swallowed in the water
drunk by man, are hatched in his intestines, and obstruct
the smaller blood-vessels, causing, it is claimed, various
forms of elephantoid disease, perhaps even leprosy. The
mosquito sucks up the parasite in the blood of leprous pa-
tients, voiding the eggs in the pools it frequents. Filaria
hemalica has occurred in the blood of the foetus of a dog
whose heart was filled with them. Ears of wheat are
often infested by a minute Nematode (Tylenchus scandens
Schneider, Aiujuil-
lula frit-id of Need-
fa am, Fig. 88).
Other species live iu
flowers, moist earth,
and sour decaying
substances. Anyuil-
lula aceti Ehren-
berg is from one to
two millimetres in
length, and lives in
vinegar.
The genus Chceto-
\<'\K. 88.— Young Wheat-Worm, greatly magnified.
a, section of " cheat" exhibiting some worms and multi-
tudes of eggs, magnified ; b, an egg containing a worm
ready to hatch.— Prom Curtis, after Bauer.
soma lives free in
the sea, and has a broad swollen head beset with fine hairs.
It apparently connects the true ISTematodes with Sagitta.
THE HAIR-WORMS.
129
The second suborder, Gordiacea or hair- worms, differ in
their mode of development from the true Nematode worms,
the embryo of Gordius being armed with oval spines, thus
Fig. 89. — Gordius uquatiais. A, egg;; B, egg undergoing segmentation of the
yolk ; C, embryo (gastrula) with the primitive stomach, an infold of the outer ger-
minal layer of cells (ectoderm); D. embryo farther advanced ; E, larva, with the
three circles of spines retracted within the (Esophagus; F, the same stage greatly
enlarged to show the internal organs ; c, middle circle of spines, the head being
retracted; in, muscular layei (?) ; t, beak or proboscis; i, intestine ; z,z, embryonal
cells; /, excretory tube leading from g, the secretory glands; an, oesophagus; >.', rcc-
tutn ; /(, anus. G. the second larva, encysted in a fish— (after Villot). H, Got'*/ in*
varim, end of body of male, much mlarged. I, Gordius aqualicus, end of body
of male, much enlarged. K, Gordvui aquations, natural size.— (H, 1, K, druwu from
nature by J. S. Kiugsley.)
reminding us in this respect of Echiriorhynchi, but the em-
bryos, Iarva3 and adult have a well-developed alimentary
canal.
130 ZOOLOGY.
The hair-worms belong to the genera Mermis and Gordius.
In the former genus the head is beset with papillae, and the
end of the body of the male is undivided, while the oviduct
of the female opens in the middle of the body. The larva
is unarmed and has no metamorphosis. Mermis acuminata
Leidy is pale brown and parasitic in the body of the cater-
pillar of the coddling moth ; another species lives in the
bodies of grasshoppers.
The true hair-worm, Gordius, has no papillre on the head,
and the tail of the male is forked, while the oviduct of the
female opens at the end of the body. The following account
of the development of the common Gordius aquaticus Linn,
which is a parasite of the locust and other insects, and is
common to Europe and this country, is taken from Villot's
" Monographic des Dragouneaux."
The eggs (Kig. 89, A) are laid in long chains ; they are
white, and excessively numerous. The yolk undergoes total
segmentation (Fig. 89, 11). At the close of this period,
when the yolk is surrounded by a layer of cells, the germ
elongates at what is destined to be the head-end ; this layer
pushes in, forming a cavity, and in this stage it is called a
"gastrula" (C). B_\ this time the embryo becomes pear-
shaped (D) ; then it elongates. Subsequently the internal
organs of digestion are formed, together with three sets of
stiff, spine-like appendages to the head, while the body is
divided by cross-lines into segments. The head lies retracted
within the body (E}.
In hatching, it pierces the egg membrane by the aid of its
cephalic armature, and escapes into the water, where it passes
the early part of its life. Fig. 89, F, represents the embryo of
Gordius aquaticus greatly magnified. It will be seen how
greatly it differs from the adult hair-worm, having in this
stage some resemblance to the Acantlwcephalus\)y its cephalic
armature, to the Ncmatoidea or thread -worms by its alimen-
tary canal, and in the nature of its secretory glands to the
larvaj (ccrcaria) of the Trematodes or fluke-worms. But the
hair-worm differs from all these worms and even Mermis, a
hair-worm much like and easily confounded with Gordius,
in having a complete metamorphosis after leaving the egg.
DEVELOPMENT OF HAIR-WORMS. 131
TVhcn in this stage it incessantly protrudes and retracts
its armed head, the spines being directed backward when the
head is out.
In the first period of larval life the worm lives encysted
in the bodies of aquatic fly larvae. The vessel in which
M. Villot put his Gordius eggs also contained the larvae of
Tanapus, Corethra, and Chironomus, small gnat-like flies.
He found that each of these larvae contained numerous cysts
with larvae of Gordius. He then removed the larvae
from the cysts, placed them on the gnat-larva, and saw the
larval hair-worm work its way into the head of the gnat-
larva through the softer part of the integument ; during the
process the spines on the head, reversing their usual position,
enabled the worm to retain its position and penetrate farther
in. Then, finding a suitable place, it came to rest, and re-
mained immovable. Then the fluids bathing the parts co-
agulated and formed a hard, granulated sac. This sac at
first closely envelopes the body, then it becomes looser and
longer, the worm living in the anterior part, the front end
of the sac being probably never closed. In this first larval
state the worm is active.
In the second larval period the young hair-worm lives mo-
tionless and encysted in the mucous layer of the intestines
of such small fish as prey on the gnat-larvae. A minnow, for
example, swallowing one of the aquatic gnat-larvaa, the en-
cysted larva becomes set free by the process of digestion in the
stomach of the fish ; the cyst dissolving, the young hair-
worm itself becomes free in the intestine of its new host.
Immediately it begins to bore, aided by the spines around
the head, into the mucous membrane lining the inner wall
of the intestine of the fish, and there becomes encysted, the
worm itself lying motionless in its new home, with its head
retracted and the tail rolled in a spiral. The cyst is either
spherical or oval. (Fig. 89, G).
The return to a free state and an aquatic life occurs in the
spring, five or six months after the second encystment. It
then bores through its cyst, and passes into the intestinal
cavity of the fish, and from thence is carried out with the
faeces into the water. On contact with the water great
ZOO LOOT.
changes take place. The numerous transverse folds in the
body disappear, and it becomes twice as long as before, its
head-armature disappears, the body becomes swollen, milky,
and pulpy. It remains immovable in the water for a vari-
able period, and then increases in size ; the integument grows
harder, and when about two inches long it turns brown and
begins to move. Most hair-worms live in ground beetles
and locusts, twining round the intestines of their host,
finally passing out of the anus. They are often seen in
fresh water pools, twisted into knots, whence their name
Gordiux. They sometimes occur in horse-troughs, whence
they are supposed by the ignorant to be transformed horse-
hairs.
Order 3. Cliatognatlii. — This group is represented by a
single genus, Sayitta, which, from the singularities in its form
and structure, has by different authors been referred to the
Crustacea, the Mollusca and even the Vertebrates. Its de-
velopment and structure show that it is closely allied to the
Nematode worms. It is about two centimetres (nearly one
\ \j
half inch) in length, and is found swimming at the surface
of the ocean in different parts of the world. The lateral and
caudal fin-like expansions of the skin of the end of the
body gives it a fish-like appearance. There is a well-defined
head, with several curved spines on each side of the mouth,
which serve as jaws ; besides these, at the sides of the head
are four sets of short, strong spines. In the young Sagitta
there are also a few pairs of lateral spines behind the head,
but these afterwards disappear. The alimentary canal forms
a straight tube terminating in a ventral opening near the
posterior fourth of the body. The nervous system consists
of a brain from which two nerves are distributed to the eyes,
and two lateral nerves pass backward to a large ventral gan-
glion lying near the middle of the body, from which two
threads pass backwards. The sexes are united in the same
individual, the two long tubular ovaries communicating by
two long ciliated oviducts, each with a separate outlet at the
base of the tail. Behind the ovaries and anus are two cham-
bers in which the spermatic particles are developed from mass-
es of cells floating freely in the perivisceral fluid, and escap
THE SAG ITT A'. \:\:\
ing by a lateral duct, on each side of the tail. The egg passes
through a mornla and gastrula stage (Fig. 90). The prim-
itive opening (a) afterwards closes
and a new opening is made at the op-
posite pole, which is the permanent
mouth. The embryo is oval at first,
but soon elongates, and the form of the eil-
adult is attained before the Sagitta
leaves the egg. Sayilta elegans Ver-
rill is about. 10 millimetres in length,
and is common in the waters of New Fig. so.-Gastmhi or S
gitta. — After Kowalevsky.
.England.
CLASS II.— NEMATELMINTHES.
Round-bodied worms, with a dense integument, not jointed ; /r/'f/t, <ru ali-
mentary canal (except in Echinorhyncfvttf!),; no water- vascular or respira-
tory system ; the nervous system 'usually reduced to a, brain <nnl tiro /,(/'•
vous threads passing along the body ; with excretory organs. The head
sometimes hooked or spinulated ; and except in Ecliinorhynchii* it ml Gor-
diacea no metamorphosis, the young hatching in the form of the adult.
Mostly parasitic, and usually bisexual.
Order \. Acanthocephali. — Cylindrical, with a beak armed witli hooks,
without mouth or digestive tract. (Echiuorhynchus.)
Order 2. Nematodes. — Long, slender, cylindrical, with a mouth and
intestine ; but no metamorphosis. Suborder 1. True Ne-
matodes (Ascaris, Oxyuris, Eustrongylus, Trichocephalus,
Trichina, Filaria, Anguillula, Echinoderes). Suborder 2.
Gordiacert (Mermis, Gordius).
Order 3. Chaetognathi. — Having a well-marked head, with lateral and
caudal fin-like expansions of the skin ; hermaphrodite.
(Sagitta.)
Laboratory Work. — These worms are to be mainly sought for in
the alimentary tract of fishes and mammals, while Sagitta may be
caught with the tow-net. They may be studied with good success be-
sides the ordinary mode of dissection, by cross-sections for the micro-
scope.
134
ZOO LOO T.
CLASS III. — ROTATORIA (Rotifers').
General Characters of Rotifers.— The Rotifers, or wheel-
animalcules, are abundant in standing water, in damp moss,
etc., and in the ocean, and are so transparent that their in-
ternal anatomy can be studied without dissection, while they
are so minute, being from one fortieth to three hundred ths
of an inch in length (f to f mm.), that high powers of the
microscope are needed in
studying them. They are
of special interest from
the fact that after being
j\ dried for months to such
g a degree that little if any
eg moisture is left in the
^,3 body, they may be revived
and become active. Pro-
fessor Owen has observed
c& the revivification of a
Rotifer after having been
eg kept for four years in dry
sand.
As an example of the
ordinary type of Rotifer
we may cite Squamella
Fig. 91. -Sqimmella oMcmc,a, magnified 200 oUonga (Fig. 91), which
diameters. A view from below; shell or cara-
pace (s, .«'. -«2) ; s, 'he anterior transverse edge
of the carapace ; *', the anterior, and .s2. the
posterior corners of the carapace; x:f, the border
of the oval, Hat area winch occupies the lower
face of the carapace: Ib, the cilia-bearing velum
of the
mouth
stoinac
the
£^3
two largely developed young. —After "Clark. ^-1,;,,]. Pm -n-il
\* 111^11 1O \j\JLLl L/ttl Cb*J\.\j \J\J
the velum of the larval mollusk. By means of the rotatory
movements of this velum the creature is whirled swiftly
around. The body is broad and flattened, with the walls
often dense, chitinous, sometimes shell-like, and variously
sculptured, or the animal may be long and worm-like, as in
Rotifer vulgar is (Fig. 9'3). The body is composed of several,
is allied to Brachionus.
The characteristic organ
of the wheel-animalcules
STRUCTURE OF ROTIFERS.
not over six, segments. A Kotifer may, in fact, be regarded
as an advanced frochosphere or more properly cephalula, and
comparable with the larvae or cephalula? of mollusks, Poly-
zoa, Brachiopoda and the Annelids. The alimentary canal
consists of a funnel-like cavity, the mouth, which may
be central, or situated on one side of the head ; it leads
to the maxtax or pharynx-like muscular sac, supporting
a complicated set of chitinous teeth within (malleus
and incus) which seize and masticate the food, which,
through the rotary action of the velum, passes
down the buccal channel or mouth-opening, and
lodges within the mastax. The so-called sali-
vary glands are two large, clear, vesicular
glands, which are attached to the funnel and
rest on the summit of the mastax. The latter
opens into the oesophagus, "a membranous
tube, capable of great expansion and contraction,
but varying much in length and diameter in
different genera." Gosse also states that a cur-
rent of water appears to be almost constantly
setting through the funnel and mastax, and
thence through the oesophagus into the stomach ;
the latter is quite large, and provided with so-
called ''pancreatic1' glands, emptying into the
anterior end. There are also hepatic follicles
and caeca, while the intestine ends in a rectum
and cloaca, the latter opening at the base of
the tail. In Notommata, the digestive canal
ends in a blind sac, and in such male Rotifers
as are known, there is no digestive cavity, the
canal being represented by a solid thread.
There are no vascular or respiratory organs, but
a system of long, convoluted excretory tubes,
one on each side of the body, which, as in the Trematodes
and Cestodes, unite in a common, large contractile vesicle
Avhieh opens into the end of the intestine. These tubes,
Avhich are in places ciliated, correspond to the segmental or-
gans of Annelids ; they are open at the end, the cavity of
the tubes thus communicating with the body-cavity.
92. -/?<>-
136 ZOOLOGY.
The nervous system is very simple, consisting of a rather
large ganglion situated behind one wing of the velum, and
lying just under an eye-spot. A supposed organ of hearing,
consisting of a sac filled with calcareous matter, is attached
to the ganglion.
The sexes are distinct, and the male and female reproduc-
tive glands open into the cloaca. The sexes are, moreover,
remarkably unlike, the males being much smaller than rhe
females, rudimentary, sac-like in form, without any digestive
sac, and are very short-lived. Some Eotifers produce what
are called winter as well as summer eggs ; the former being,
as in some Turbellarian worms and Polyzoa, covered with a
hard shell to resist the extremes of the winter temperature.
The summer eggs develop without being fertilized, while the
winter eggs are fertilized, those of Lacinularla, however,
according to Huxley, not being impregnated.
The eggs of Brachionus are attached by a stalk to the
hinder part of the body of the female. The following
remarks apply to the mode of development of the fe-
male eggs, which are quite distinguishable from the mas-
culine ones. The eggs undergo total segmentation, and
the outer layer of cells resulting from subdivision forms
the blastoderm, and when this is developed the forma-
tion of the organs begins. The first occurrence is an in-
folding of the blastoderm (ectoderm) forming the primitive
mouth, Avhich remains permanently open, the mouth not
opening at the opposite end as in Sagitta, but the entire de-
velopment of the germ is much as in the mollusk Calyptrcea,
as Salensky often compares the earliest phases of devel-
opment of this Rotifer with those of that mollusk. The
"trochal disk," or velum, arises in certain mollusks,
as a swelling on each side of the primitive infolding.
There is soon formed at the bottom of the primitive in-
folding a new hole or infolding of the ectoderm, which is
the true mouth and pharynx, while a swelling just behind
the mouth becomes the under lip. The stomach and intes-
tine arise originally from the endoderm.
Soon after, the two wings of the velum become Avell
marked (Fig. 93, v), and their relation to the head is as
DEVELOP MKNT OF ROTIFERS. 137
constant as in Calyptraea. The tail (t) becomes conical,
larger, and the termination of the intestine and anal open-
ing is formed at the base.
The internal organs are then elaborated ; first the nervous
system, consisting of but a single pair of ganglia arising
from the outer germ-layer (ectoderm). Soon after the sen-
sitive hairs arise on the wings of the velum.
Fig. 93 represents the advanced embryo, with the body di-
vided into segments, the pair of ciliated wings of the velum
(i1), and the long tail (/). At this time the shell begins to
form, and afterwards covers the whole trunk, but not the head.
The inner organs are developed from the inner germ-layer
(endoderm), which divides into three layers, one forming the
middle part of the intestine, and the two others the glands
and ovaries. The pharyngeal jaws arise as
tAvo small projections on the sides of the
primitive cavity. The male develops in
the same mode as the female.
Though the development of the Eotifers,
so fur as known, is more like that of the
mollusks than true worms, the Eotifers
may be regarded as a generalized cephalula
form, representing the larval forms of An-
nelids and molllisks, with decided affinities, nearly read/to hatch.
when we consider their chitinous covering ~Aft<
or carapace, the fold of the intestine, and the single nervous
ganglion, to the Polyzoa, and with more remote resemblances
to the Brachiopods. They are on the whole generalized forms.
A few species are parasitic : Albertia living internally, and
Balatro on the surface of the Nais-like worms. With the
lower Rotifers are associated a group of worm-like forms
represented by Chcetonotux, Iclithydium, etc., and forming
the group Gastrotricha. They have no mastax, and the body
is only ciliated near the end. Through Dinophilus, a Tur-
bellanan worm, they are connected with the flat worms.
The genus Ecltiiwderex is also regarded by Clans as a low
Rotifer. It seems quite apparent from this that the Eotifers
are a type which has originated from worms resembling the
generalized Tur^ellarian form, and AV'nnh. connects the latter
138 ZOOLOGY.
with the Polyzoa, Bracltiopods, and possibly the Mollusca,
the latter branch being probably a modified vermian type,
and with 1111 ancestry not unlike that of the Rotifers and
aberrant, generalized Polyzoa and Brachiopoda. The classi-
fication of the Rotatoria is in an unsettled state, the group
probably consisting of three orders, viz. : the true Rotatoria,
the Echinoderidce, and Gustrutricha.
CLASS III.— ROTATORIA.
Worms with usually more or less solid segments, very unequally developed,
bearing a ciliated velum, the mouth opening into a mastax ; sexes separate,
the males much ^nailer, more rudimentary than the females. A small
nervous ganglion. No circulatory apparatus, but with a voluminous excre-
tory (water-vascular) organ..
(Albcrtia, Asplaiichnu, Hydatiua, Brachiouus, Rotifer, aud the
highest form, Floscularia.)
Laboratory Work.— The Rotifers can only be studied while alive and.
as transparent objects. Little is known about the American species.
CLASS IV. — POLYZOA (Moss Animals).
The Polyzoa, though not commonly met with in fresh
water, are among the commonest objects of the seashore.
They are minute, almost microscopic creatures, social, grow-
ing in communities of cells (called poly-
zoaria or corms), forming patches on sea-
weeds and stones (Fig. 94, Memlranipora
soli-da Pack.). Certain deep-water species
grow in coral-like forms (Fig. 95, Mijrio-
zoum subyracile D'Orbigny), while the
chitiuous or horny Polyzoa (Fig. 90,
_ HalopMla borealis Pack.), are often mis-
Fig 94-ceii8ofSea- taken for sea- weeds on the one hand, and
Sertnlarian Hydroids on the other. From
their likeness to mosses the name Bryozoa was given to the
group by Ehrenberg, a year after Thompson (1830) had
called them Polyzoa, so that the latter name has priority.
THE POLYZOA.
139
The simpler form of Polyzoon is a worm-like creature
enclosed in a minute, deep, horny cell, with the alimentary
canal bent on itself and terminating in a vent situated near
the mouth, the latter surrounded, in the fresh-water forms,
Fig. 95.— Branching marine Polyzoon. Corru of Myriozouni ti/bgracile,
natural size.
with a horseshoe-shaped crown, or in the marine species a
circle of slender ciliated tentacles. The animal when dis-
turbed withdraws into its tube or shell, which is often trans-
parent, allowing it to be examined
when alive. The cells are rarely
single, but a cormus, polyzoarium or
polyzoon-stock is formed by the bud-
ding of numerous cells from the one
first formed. The single polyzoon is
called a polyp ide, and its cell a cyst id.
In Pedicellina, the simplest polyzoon,
the polypide has no cystid or cell.
The cells are, in the marine forms,
usually closed, and independent of
each other. The wall forming the
cell is called the endocyxt ; it com-
prises the ectoderm proper, with a portion (parietal layer) oif
the mesoderm forming the soft lining of the cell.
Fig. 96 .— Halopfrila borealis,
enlarged.
140
ZOOLOGY.
The mouth is situated on a disk (tophophore, Fig. 97, B),
bearing the tentacles, which are hollow processes of the
body-walls, communicating with the body-cavity, the blood
flowing into them, there being aerated, while they are exter-
nally ciliated. They serve both to catch food and for respir-
ation as makeshift gills. Hyatt states that the tentacles are
used not only to catch the prey, but for a multitude of other
offices. They are each capable of in-
dependent motion, and may be twisted
or turned in any direction ; bending
inwards, they take up and discard
objectionable matter, or push down
into the stomach and clear the
oesophagus of food too small to be
acted upon by the parietal muscles.
They are also employed offensively in
striking an intrusive neighbor, and
their tactile power, sensitive to the
slightest unusual vibration in the
water, warns the polypide of the ap-
proach of danger.
The digestive canal hangs free in
the body-cavity, only attached by the
mouth and anus to the walls of the
body. It consists of a pharynx, a
large stomach, and an intestine which
Ijpc }lv HIP qj,]p nf HIP nli-irvnv <smpo
J-> ' plKliyilX, S1UC6
B piunwMia the canal has a simple deep dorsal
fruticosa. b?-, tentacular bran-
chiae of luphophore; ce, ceso- flexure, the vent being situated on
phagus; c, stomach: r, intes- °
tine; «, anus; i, ceil; x, pos- the dorsal or cardiac side, near the
tenor, xl, anterior, cord, at 1T ...
the insertion of which into mouth. Usually the stomach IS tied
the body the generative prod- i » •>• / ,. . ^ \
ucts are developed; t, testes; by a Sort ot ligament (funiCUluS) to
a point on the body-walls, near the
Fig. 97.— Organization of a
Polyzoon. A, Paludicella
mouth- The nervous system is rep-
resented by a double ganglion form-
ing a single mass situated between the mouth and vent; it
is highly contractile and changeable in form. There is no
heart and no circulatory apparatus. The sexes are united
in a single polypide, the glands forming masses growing on
STRUCTURE OF THE POLYZOA. 141
the funiculus or in the walls of the body. The body,
especially the lophophore, is retracted and pushed out
by muscles arranged in pairs on either side. As seen in
Fredericclla, a fresh- water form, the alimentary canal
"hangs from the lophophore, occupying the centre of
the polypide, and floating- freely in the rapidly moving
blood" (Hjatt). The yellowish oesophagus, the stomach
barred with brown, and the brownish intestine are balanced
upon a fold of the intestine (the invaginated fold), which
is retained in the cell by the retentor muscles, and is sur-
rounded by a large sphincter muscle. There are two sets
of large retractor muscles, one on each side of the digestive
canal, and arising from two common bases ; each large trunk
subdivides into three branches, the retractor of the stomach,
of the lophophore, and of the anus. The crown of tenta-
cles is swayed by these muscles in every direction, or when
alarmed the polypide may withdraw by their aid into the
cell, as the finger of a glove may be inverted within the
empty palm. This may be done with great rapidity or
slowly. The process has thus been graphically described by
Hyatt: "The polypidal endocyst is first turned inwards,
folding upon itself, and prolonging the permanently invagi-
nated fold below. The tentacles, arriving at the edge of
the coanoecial orifice, are pressed into a compact bundle by
the action of their own muscles, and, together with the
lophophore, are dragged into the cell by the continued invag-
ination of the endocyst until they are wholly enclosed and
at rest within the sheath formed for them by the inverted
walls of the tube. The sphincter muscle then closes the
coenoecial orifice above, and the process of invagination is
completed.
" The polypide in its exserted state is buoyed up and sus-
tained by the pressure of the fluids within. Consequently,
when invaginated, it displaces an equal bulk of these in the
closed coanoecium, and their reaction, aided by the contrac-
tion of the muscular endocyst, is sufficient to evaginate the
whole.
" The evagination begins with the relaxation of the sphinc-
ter, which permits the ends of the tentacles to protrude.
142 ZOOLOGY.
These daintily feel about for the cause of the alarm, and, if
they fail to detect the proximity of an enemy, the whole
fascicle is cautiously pushed out, and the sentient threads
suddenly and confidently unfolded.
"The polyzoon reasons from the sense of touch inherent
in its tentacles, and cannot be induced to expose itself above
the ccenoecium until thoroughly satisfied by these sensitive
feelers that no danger is to be apprehended. In fact, these
plant-like creatures, singly mere pouches with a stomach
hanging in the midst, exhibit greater nervous activity and
'animality,' than we find among the more highly organized
Ascidia, or shell -covered Brachiopoda."
The epistome is a fold of the lophophore, used to close the
mouth and thus prevent the food from escaping from the
mouth. It is tongue-like and very pliable. " The border is
capable of a tactile motion similar to that of the human
tongue, and it takes cognizance of what passes into the
mouth by frequent and repeated jerks toward the aperture""
(Hyatt). It is situated immediately over the ganglionic mass,
and between the anus and mouth.
The Polyzoa, as regarded by Hyatt and others, are struc-
turally nearly related to the Brachiopods, the higher forms
of which, such as Terebratula and Rhynchonella, have the res-
piratory tentacles similarly placed around the disk or lopho-
phore, which is perforated at the centre by the mouth, and
from which the alimentary canal hangs, "7ith a dorsal flexure
and anus near the mouth. " The extension of the lophophore
into two or three spiriform arms, the complex structure of
the tentacles and of the muscular and nervous systems, are
all more or less foreshadowed by the condition of these sys-
tems among the higher Polyzoa" On the other hand, the
Polyzoa are closely related to the worms, the Gephyrean
worm, Phoronis, being the connecting link. The mode of
development of the Polyzoa and Brachiopoda are quite simi-
lar, as will be seen farther on, and owing to these decided sim-
larities in development and anatomy, the Polyzoa and Brachi-
opods form a natural group or series, distinct on the one
hand from the Rotatoria, and on the other from the molluska
and worms.
DEVELOPMENT OF THE POLYZOA. 143
Certain branching marine forms are provided with organs
like birds' heads, situated on a stalk and called avicularia, with
a movable jaw-like appendage, which keeps up an incessant
snapping. Beside the avicularia, there are, as in Scrupo-
cellaria, long bristle-like appendages to the cells, called
vibracula,
There are no organs cf special sense in the Polyzoa, unless
the epistome maybe legarded as an organ of sense, and the
nervous system consists of a single rounded ganglion (Frede-
ricella], or, as in Plumatella, a double ganglion, situated be-
tween the mouth and vent, from which one set of nerves are
distributed to the epistome, lophophore, tentacles, and evagi-
nable endocyst, and another set to the various parts of the ali-
mentary canal. A so-called colonial nervous system is sup-
posed to exist in the Polyzoa, as when the ccencecium in some
forms is touched all the polypides become alarmed, which
indicates that a set of nerves connect the different polypides,
though no such nerves have yet been discovered. The
fresh-water Polyzoa are not sensitive to light, nor to noises,
only to agitation of the water in which they dwell.
All the Polyzoa are hermaphrodite, the ovary and male
glands residing in the same cystid, the testis being situated
near the bottom and attached to the funiculus, while the
ovary is attached to the walls of the upper part of the cell.
Allman regards the polypide and cystid as separate indi-
viduals. The singular genus Loxosoma is like the polypide
of an ordinary Polyzoan, but does not live in a cell (cystid).
On the other hand, we know of no cystids which are with-
out a polypide. Remembering that the cystids stand in the
same relation to the polypides as the hydroids to the medusae,
as Nitsche insists, we may regard the polypides as secondary
individuals, produced by budding from the cystids. The
large masses of cells forming the moss-animal, which is thus
a compound animal, like a coral stock, arises by budding out
from a primary cell. The budding process begins in the
endocyst, or inner of the double walls of the body of the
cystid, according to Nitsche, but according to an earlier
Swedish observer, F. A. Smitt, from certain fat bodies float-
ing in the cystid.
144 ZOOLOGY.
The Polyzoa are divided primarily into the Entoprocta>
(Loxosoma and PedicelUna) in which the vent is situated
within the circle of tentacles, and the Ectoprocta, in which
the vent lies outside of the lophophore — a group comprising
all the higher Polyzoa (Gymnokemata and PJiylactolcBmata).
The development of the Polyzoa is not very complicated.
In the marine forms, as studied by Barrois, the germ passes
through a morula stage ; after which the cells are arranged
into two halves, separated by a crown of cilia ; at this stage
it is called a blastnla. At the time of birth the ciliated germ
is a disk-shaped gastrula, with two opposite faces or ends,
separated by the crown, one (aboral) bearing in its centre
the mouth-opening. This ciliated free-swimming top-like
gastrula stage is called a trochosphere.
After swimming about as ciliated larvae (trochospheres),
the shell or ectocyst develops, and the larva becoming station-
ary, the cystid forms, its calcareous shell develops, and finally
the polypide is indicated, and the primitive cell is gradually
formed.
As seen in. Phalangella flabellans, the larva, after becoming
fixed to some object, consists of a white pyriform mass,
closely enveloped by an ectocyst, with numerous fat globules
between the latter and the white mass. The ectocyst swells
into a discoidal sac, with endocvst, ectocvst, and an external
V «/
zone, while the internal whitish mass transforms into the
polypide. The discoidal sac formed by the endocyst consti-
tutes simply the basal disk of the primitive cell. The future
opening of the cell appears on the upper surface of the cell.
The budding out of the secondary cells of the polyzoarium
or corm then takes place. It begins by the appearance of a
cell placed in front and below the primitive cell, and which
borders it on each side ; its secondary cell then divides into
two, each of which successively gives origin to three cells,
and we thus arrive at an Idmonea stage ; and finally the
Phalangella stage is reached, the process being a dichoto-
mous mode of budding quite analogous to that which pro-
duces the broad, flattened corm of Escharina.
The development of Membranipora pilosa, which is very
abundant on our shores, growing on sea-weeds, is of singu-
DEVELOPMENT OF THE POLYZOA. 345
lar interest. The free-swimming ciliated larva is provided
with a bivalve shell, and was originally described as a La-
mellibranch larva under the name of Cyphonautes.
Schneider discovered that it was a young Membranipora.
Barrels, who has traced its complete history, states that its
metamorphosis is fundamentally like that of the other ma-
rine Polyzoa. Flustrella hispida passes through a similar
Cyphonautes stage.
In Loxosoma young resembling the adult bud out like
polyps. Nitsche does not regard this budding process as an
alternation of generations, but states that in Polyzoa of the
family of Vesiculariidce, this may occur, as in the latter
some cystids form the stem, and others (the zocecia) produce
the eggs. Most fresh-water Polyzoa reproduce by the devel-
opment of winter buds or eggs surrounded by a horny case,
and developing from the funiculus.
To recapitulate : the Polyzoa increase (a) by budding ; (b)
by normal (summer) eggs, and by producing statoblasts, or
winter eggs. In reproducing from summer eggs, the young
pass successively through a morula, blastula, gaxtrula and
trochoxphere stage before attaining maturity.
The most aberrant Polyzoan is Rhabdopleura mirabilis Sars,
•which occurs in from 100 to 300 fathoms on the coast of
Norway. It differs from other forms by the want of an en-
docyst or mantle, whence it moves up and down in its cell,
without being attached to the opening, the muscles usually
present being wanting, the cord by which it is attached to
the bottom of its long, slender tubular cell being contractile.
The lophophore is much like that of the fresh-water Poly-
zoans, consisting of two long arms, bearing two rows of
slender tentacles. The epistome is represented by a large
round disk.
The marine Polyzoa occur at great depths, and a few species
are cosmopolitan ; the type is very persistent, and occurs
in the oldest Silurian strata, the earliest forms being very
similar to their living descendants.
140 ZOOLOGT.
CLASS IV.— POLYZOA.
Animals usually forming moss-like or coral-like calcareous or chitinous
masses called conns, each cell containing a worm-like animal, with the di-
gestive tract flexed, the anus situated near the mouth. The body usually
drawn in and out of the cell by the action of retractor and adductor muscles
The mouth surroundedby a crown of long tentacles. No heart or vascular
system. Nervous system consisting of a single or double ganglion situated
between the mouth and vent, with nerves proceeding from it. Hermaphro-
ditic ; multiplying by budding or eggs. Tlie embryo passing through a
morula, gastrula and trochosphere stage, the conn being formed by the
budding of numerous cells from a primitive one.
Order 1. Entoprocta. — Vent within the lophophore. (Loxosorna.)
Order 2. Ectoprocta. — Vent without the lophophore. (Lepralia, Es-
chara, Idmonea, Myriozouin.)
Laboratory Work. — The Polyzoa are too small to dissect, and
must be studied while alive as transparent objects, and may be kept
in aquaria. The corms in part or whole can be mounted for the mi-
croscope as opaque objects.
CLASS V. — BRACHIOPODA (Lamp Shells).
General Characters of Brachiopods.— This group is named
Bracliiopoda from the feet-like arms, fringed with tentacles,
coiled up within the shell, and which correspond to the
lophophore of the Polyzoa and the crown of tentacles of the
Sabella-like worms. From the fact that the animal secretes
a true, bivalved, solid shell, though it is usually inequivalve,
i. e., the valves of different sizes, the Brachiopoda were gener-
ally, and still are by some authors, considered to be mol-
lusks, though aberrant in type. They may be regarded as a
synthetic type of worms, with some superficial molluscan
features. The shell of our common northern species, Tc/'r-
Irahdlna septentrionalis, which lives attached to rocks in
from ten to fifty or more fathoms north of Cape Cod, is in
shape somewhat like an ancient Roman lamp, the upper and
larger valve being perforated at the base for the passage
through it of a peduncle by which the animal is attached
to rocks. The shell is secreted by the skin (ectoderm), and i?
STRUCTURE OF BRACHIOPODS. 147
composed of carbonate (Terebratulina) or largely (Lingula,
Fig. 103) of phosphate of lime. It is really the thickened
integument of the animal, the so-called mantle being the
inner portion of the skin, containing minute tubular canals
which do not open externally.
The body of Brachiopods is divided into two parts, the
anterior or thoracic, comprising the main body-cavity in
which the arms and viscera are contained, and the caudal
portion, i. c. the peduncle. The part of the body in which
the viscera lodge is rather small in proportion to the entire
animal, the interior of the shell being lined with two broad
lobes, the free edges of which are thickened and bear setae,
as seen distinctly in Lingula. The body-cavity is closed
anteriorly by a membrane which separates it from the space
in which the arms are coiled up The "pallial cham-
ber" is situated between the two lobes of the mantle (pal-
lium} and in front of the membrane forming the anterior
wall of the body-cavity. In the middle of this pallial
chamber the mouth opens, bounded on each side by the
base of the arms. The latter arise from a cartilaginous
base, and bear ciliated tentacles, much as in the worm Sa-
l)dla. In Lingula, Discina, and Rliynchonella, they are de-
veloped, as stated by Morse, in a 'closely-wound spiral, as in
the genuine worms (Ampliitrite). In Lingula the arms can
be partially unwound, while in lUiuni'ltonello they can not
only be unwound but protruded from the pallial chamber.
In many recent and fossil forms the arms are supported by
loop-like solid processes of the dorsal valve of the shell, but
when these processes are present the arms cannot be pro-
truded beyond the shell. The tentacles or cirri on the arms
are used to convey to the mouth particles of food, and they
also are respiratory in function, there being a rapid circula-
tion of blood in each tentacle, Avhich is hollow, communi-
cating with the blood-sinus or hollow in each arm, the sinus
ending in a sac on each side of the mouth.
The digestive system consists of a mouth, oesophagus,
stomach, with a liver-mass on each side, and an intestine.
Fig. 98 shows the relation of the mouth and digestive canal
to the head and arms, as seen in a longitudinal section of
ZOOLOGY.
the anterior part of the body of Lingula. The mouth is
bordered by two membranous, highly sensitive and movable
lips. The stomach is a simple dilatation of the alimentary
canal, into which empty the short ducts of the liver, which
is composed of
masses of cceca.
The liver origi-
nally arises as
twodiverticula
or offshoots of
the stomach.
The short in-
testine ends in
a blind sac or
in a vent, and
is, with the
i? ig. w. — i i M i •_ n 1 1 1 1 1 11 a i BC^LUJII \j\ LIU/ anttriiui jjui LIIMI ui "1 J* 1
Linqula. m, mouth ; &>, oesophagus ; $/, stomach ; «, arm ; ci, StOIliacn,ireeiy
_ • ; _ !._/• t _!_•_! i«_ i J . _r *..!..„; i_, _* . . **
suspended in
the peri visceral
cavity by delicate membranes springing from the walls of the
body. (Fig. 99.) In those Brachiopods allied to Terebra-
iula, Terebratulina, Thecidium, Waldheimia, Rhynclionella,
etc., the stomach ends in a blind sac, and there is no vent,,
the rejectamenta escaping from the mouth. In Linyula and
Discina there is a vent which terminates anteriorly on the
right side. In Linyula
the intestine makes a
few turns, while in Dis-
cina it makes a single
st ce cf) m
Fig. 98. — Longitudinal section of the anterior portion of
la. m, mouth ; a>, ffisopha»u* ; sf, stomach ; o. arm
cirri ; bf. brachial told ; cf>, cartilaginous base of arm
sinus leading to the arm ; cc, cephalic collar or pallial mem-
brane.—After Morse.
turn to the right.
The nervous system
consists of two small
ganglia above, and an
infracesophageal pair of
larger ganglia, and there
are two elongated ganglia behind the arms, from which nerves
are given off to the dorsal or anterior lobe of the mantle.
From the infraoesophageal ganglia two lateral ventral cords
pass backwards, in their tract sending off delicate threads,
Fig. 99. —Transverse section of TAngitJa. f>,
bands suspending the intestine in the perivisce-
ral cavity ; i, intestine ; .«, segment al organ ; o,
ovaries ; I, liver ; g, gills ; ,«<?, setae.— After
Morse.
STRUCTURE OF BRACHIOPODS.
149
Fig. 100.— Ampullae of blood
einu-es. showing course taken
by the blood.— After Morse.
but with no ganglionic enlargements, except in Discina,
where they terminate each by a ganglion in the last two
posterior muscles. Morse has discovered the presence of
auditory capsules in Lingula.
Respiration is mainly carried on in the mantle (pallia!
membrane). In Limjnla the pallial membrane is divided
into oblique transverse sinuses, which
run parallel to each other. From
these arise, says Morse, numerous
flattened ampullae, which are highly
contractile. The blood courses in
regular order up and down these
sinuses, entering each of the ampullae
in turn. Fig. 100 represents a row of five ampullae with in-
dications of the course taken by the blood-disks. These
ampulla have not been found in Distinct, though the pallial
sinuses are very prominent. The breathing process is also
carried on in the tentacles or cirri.
Intimately connected with the vascular system is a gland-
ular portion of the tubular part of the segmental organs of
the Bracliiopoda, which is
supposed to represent simi-
lar parts in worms as well
as the glandular, excretory
portion of the organ of
Bojanus in mollusks, and is
supposed to be depuratory
or renal in function.
The reproductive system
of Bracliiopoda consists of //
ovaries, oviducts or seg- G^
i -TT -| «! Fi'1' 101 — Segmental organs of Brachio-
mental organs, tig. 101, nods, a, Discina ; 6, Tertwatulina.-After
and spermaries. The sexes Morse'
are probably separate in all Brai-ltinjtoda (Morse).
The ovaries are attached in Disc inn and Lingula to the
delicate vascular membranes of the large sinuses in the pal-
lial membranes, the vascular membranes being thrown into
conspicuous ruffs when the eggs are ripe. In Terebratulina
and Rhynchonella they are not only similarly situated, but
150
ZOOLOGY.
hang in clusters from the genital bands in the periviscenil
cavity. The mature eggs detach themselves from the ovary
to float freely in the perivisceral cavity, whence they pass into
the flaring, ciliated mouths of the segmental organs, and are
discharged by them into the water. These segmental organs
or oviducts are tubular, trumpet-shaped, as in the true
worms (Fig. 101). In Lingula, Discina, and Terebratulina,
there is but a single pair, in Rhynconella two pairs. The
external orifices of the oviducts form simple slits, while in
Terebratulina they project from the anterior Avails like
tubercles, as in the true worms (Morse) The spermaries
occur in the same situation in the perivisceral cavity as the
ovaries. As observed in Terebratulina, by Morse, in a few
hours after the eggs are discharged the embryos hatch and
become clothed with cilia. Kowalevsky observed in the egg
of Thecidium the total segmentation of the yolk (also ob-
served in Terebratulina by Morse), until a blastoderm is
formed around the central segmentation cavity, which con-
tains a few cells. The similar formation of the blastoderm
was seen in Argiope, but not the morula stage. After this
the ectoderm invaginates and a cavity is formed, opening
^externally by a primitive mouth. The walls of this cavity
-now consist of an inner and outer layer (the endoderm and
ectoderm). This cavity eventually becomes the digestive
(Cavity of the mature animal.
In Terebratulina Morse observed that the oval ciliated
germ became segmented, dividing into two and then three
rings, with a tuft of
long cilia on the an-
terior end (Fig. 102,
A). In this stage the
larva is quite active,
s w i m m i n g rapidly
about in every direc-
tion.
Soon after, the germ
looses its cilia and becomes attached at one end as in Fig.
102, B (c, cephalic segment ; th, thoracic segment; p, pe-
duncular or caudal segment). The thoracic ring now in-
Fig. 105.— Larval stages of Terebratulina.—
After Morse.
DEVELOPMENT OF BRACH10PODS. 151
creases much in size so as to partially enclose the cephalic
segment, as at C. The form of the Brachiopod is then soon
attained, as seen in D, in which the head (c) is seen project-
ing from the two valves of the shell (tli), the larger being
the ventral plate.
The hinge margin is broad and slightly rounded when
looked at from above ; a side view, however, presents a wide
and flattened area, as is shown in some species of Spirifer,
and the embryo for a long time takes the position that the
Spirifer must have assumed (Morse). Before the folds have
closed over the head, four bundles of bristles appear ; these
bristles are delicately barbed like those of larval worms.
The arms, or cirri, now bud out as two prominences, one on
each side of the mouth. Then as the embryo advances m
growth the outlines remind one of a Leptcena, an ancient
genus of Brachiopods, and in a later stage the form becomes
quite unlike any adulb Brachiopod known.
The deciduous bristles are then discarded, and the perma-
nent ones make their appearance, two pairs of arms arise,
and now the shell in " its general contour recalls JSiphono-
treta, placed in the family DiscinidcB by Davidson, a genus
not occurring above the Silurian." No eye-spots could be
seen in Terebratulina, though in the young Thecidium they
were observed by Lacaze-Duthiers. The young Terebratu-
lina differs from Discinaof the same age in being sedentary,
while, as observed by Fritz Miiller, the latter "swims freely
in the water some time after the dorsal and ventral plates,
cirri, mouth, oesophagus and stomach have made their ap«
pearance." Discina also differs from Terebratulma in hav-
ing a long and extensible oesophagus and head bearing a
crown of eight cirri or tentacles. Regarding the relations
of the Brachiopods with the Poh/zoa, Morse suggests that
there is some likeness between the young Brachiopod and
the free larva of Pedicellina. Fig. 103, B, represents the
Terebratulina when in its form it recalls Megerlia or Argi-
ope. C represents a later Lingula-like stage. " It also
suggests," says Morse, "in its movements, the nervously
acting Pedicellina. In this and the several succeeding
stages, the mouth points directly backward (forward of
152
ZOOLOGY.
authors), or away from the perpendicular end (D), and is
surrounded by a few ciliated cirri, which forcibly recall cer-
tain Polyzoa. The stomach and intestine form a simple
chamber, alternating in their contractions and forcing the
particles of food from one portion to the other." Figure
103, E, shows a more advanced stage, in which a fold is
seen on each side of the stomach ; from the fold is developed
the complicated liver of the adult, as seen in E, which
represents the animal about an eighth of an inch long. The
arms (lophophore) begin to assume the horseshoe-shaped
form of Pecti-mttella and other fresh-water Polyzoa. At this
stage the mouth begins to turn towards the dorsal valve, and
as the central lobes of the lophophore begin to develop, the
lateral arms are deflected as in F. In the stage G an epis-
tome is marked, and Morse noticed that the end of the
Fig. 103.— Later larval stages of Terebratulina.— After Morse.
intestine was held to the mantle by an attachment, as in the
adult, reminding one of the funiculus in the fresh-water
Polyzoa. In tracing the development of Argiope, Kowal-
evsky has shown that the larva is strikingly like those of the
Annelids, as Avell as the Tornaria stage of Balanoglossiis.
While in their development the Bracliiopoda recall the
larvae of the true worms, they resemble the adult worms in
the general arrangement of the arms and viscera, though
they lack the highly developed nervous system of the Anne-
lids, as well as a vascular system, while the body is not
jointed. On the other hand they are closely related to the
Polyzoa, and it seems probable that the Brachiopods and
Polyzoa were derived from common low vermian ancestors,
while the true Annelids probably sprang independently
from a higher ancestry. They are also a generalized type,
DISTRIBUTION OF BRACH10POD&
153
having some molluscan features, such as a solid shell, though
having nothing homologous with the foot, the shell-gland
or odontophore of mollusks.
In accordance with the fact that the Brachiopods are a
generalized type of worms, the species have a high antiquity,
and the type is remarkably persistent. The Lingula of our
shores (L. pyramidata Stimpson, Fig. 104) lives buried in
the sand, where it forms tubes of sand around the peduncle,
just below low-
water mark from
Chesapeake Bay,
to Florida. It has
remarkable vital-
ity, not only with-
standing the
changes of tem-
perature and ex-
posure to death
from various oth-
er causes, but will
bear transportation to other countries in sea-water that has
been unchanged. Living Lingulae have been carried by Prof.
Morse from Japan to Boston, Mass., the water in the small
gluss jar containing the specimens having been changed but
twice in four months. The living species of this cosmopol-
itan genus differ but slightly from those occurring in the
lowest fossiliferous strata. Between eighty and ninety liv-
ing species are known, most of them living, except Lingula,
which is tropical, in the temperate or arctic seas, while nearly
2000 fossil species are known. The type attained its maxi-
mum in the Silurian age, and in palaeozoic times a few spe-
cies, as A trypa reticularis, extended through an entire system
of rocks and inhabited the seas of both hemispheres.
Fig. 104.—Linffula pyramidata making sand-tubeax
natural size.— After Morse.
CLASS V.— BRACIIIOPODA.
Shelled worms, with a limestone or partly chitinous, inequivalve, hinged
or unhinged shell, enclosing the worm-like animal ; with tiro npirally coiled
arms provided with ciliated cirri or tentacles, between which is the mouth.
154 ZOOLOGY.
CLASS VI. — NEMERTINA (Nemertean Worms}.
General Characters of Nemerteans. The Nemertean
worms occur abundantly under stones, etc., between tide-
marks and below low-water mark; they are of various col-
ors, dull red, dull green and yellowish, and are distinguished
by the soft, very extensile, more or less flattened, long and
slender body, which is soft and ciliated over the surface,
the skin being thick and glandular. A few forms, such as
Prorhynchus (Fig. 105), live in fresh water.
The mouth forms a small slit on the ventral surface im-
mediately behind the aperture for the exit of the proboscis.
The proboscis is, when protruded, a long tubular organ,
sometimes armed with stylet-shaped rods; it is thrust out of
a special opening in front of the mouth, and when retracted
within the body lies in a special muscular sheath. The
oesophagus leads to a large digestive tract, ending posteriorly
with an anus, and often with short lateral cceca. In Pela-
gotiemertes and Avenardia the numerous cceca are much
branched.
The nervous system is quite simple, consisting of two
ganglia in the head united by a double commissure; from
each ganglion a thread composed of nerve-fibres and ganglion
cells passes back to the end of the body.
The brain is well developed: the two halves are connected
by a double commissure surrounding the throat, and each
half is composed at least of a dorsal and ventral lobe.
While the Nemerteans are much like the ilat worms,
most of them approach the Annnlata, such as the earth-
worm, in their highly complicated circulatory system, which
is composed of a series of closed contractile vessels. There
are three great longitudinal trunks, one median and two
lateral, and connecting with each other. The blood is pale,
rarely red, with corpuscles. Another feature characteristic of
many Nemerteans is the "proboscis," nothing like it being
found in other worms. Along the back of the head-end is
a special muscular sheath containing the complicated probos-
cis, which is extended through a pore situated above the
mouth. The sheath contains a corpusculated fluid, and
DEVELOPMENT OF NEMERTEANS.
155
both the sheath and proboscis lie between the commissures
of the ganglia in the front part of the head.
The ovaries and testes are situated in sacs
on each side of the digestive canal. The
sexes are distinct, with the exception of cer-
tain species of Borlasia. The breeding sea-
son is from March to April, while others
spawn all summer. The eggs are ejected
from lateral, pale, minute openings, and the
species may be either oviparous or ovovivipa-
rous. These worms when molested often
break into fragments ; in such cases each
piece is capable of reproducing the entire ani-
mal and all its internal organs.
The Xemerteans present a great range of
variation in their mode of development. In
the simplest mode of growth the young is a
ciliated oval form, without any body-cavity.
In others there is a body-cavity, but the larva
is minute and ciliated, and attains the adult
form by direct growth. In still another spe-
cies (Xemertes communis) the embryo is a
ciliated gastrula, but leaves the egg in the
itdnlt form. In others there is a complete
and most interesting metamorphosis. In
several Nemertean worms the egg undergoes
total segmentation, leaving a segmentation-
cavity. The next occurrence is the separa-
tion of a one-layered ciliated blastoderm, the ^
ectoderm, which invaginates, forming the pWus-.Mhtestine;
.... . e <7<i glands opening
primitive digestive cavity, from which the luto the int.es-
«' tine; c, ciliated pits;
stomach and oesophagus are formed. Hie .T, style in the pro-
i / • • n i -11 i .1 ,» boscis situated
larva (originally described under the name of above the a?sop_im-
Pilidium) is now helmet - shaped, ciliated, Sind'aac a?y ; <w*
with a long lash (flagellum) attached to the SSg^ig? ^
posterior end of the body. (Fig. 106.)
After swimming about on the surface of ciliated.— After
genbaur.
the sea a while, the Nemertes begins to grow
out from near the oesophagus of the Pilidium. On each
Fig- 105. — pro-
15G
ZOOLOGY.
side of the base of the velum (r) of the Pilidium ap-
pear two thickenings of the skin, one pair in front,
the other behind ; these thickenings push inwards, and
are the germs of the anterior and posterior end of the
future worm. The anterior pair become larger than
the posterior ; the part of
the disk next to the oeso-
phagus thickens ; at the
same time the alimentary
canal of the Pilidium
grows smaller, and only a
narrow slit remains. The
disks now divide into two
layers, the outer much
thicker than the inner.
Soon the anterior pair of
disks unite, and the head
of the worm is soon formed,
when the elliptical outline
. t or "Pilidium" of Nemer- f t] e flftt worm is in(]i_
tea, with the worm growing in it. v, velum ;
«, eyes ; i, intestine of the Nemertean worm.— cuted, and appears SOme-
After Leuckart.
what as in Fig. 106. The
yolk mass, with the alimentary canal of the Pilidium,
is taken bodily into the interior of the Nemertes, the
Pilidium-skin falls off, and the worm finally seeks the
bottom.
The free-swimming larvae of other Nemerteans are very
closely similar to those of the Annelids, so
that from this fact and the nature of the
highly developed circulatory system, the
Nemerteans have been removed from the
neighborhood of the flat worms, and placed
near the Balanoylossus and Geplnjrea, as
well as the leeches.
Order 1. Anopla.—l\\ this group the pro-
boscis is without a style. The species of
Linens and Meckelia are, in some cases,
very long. Meckelia ingens Leidy is 2i centimetres (an
inch) wide, and attains a length of 4 metres (15£ feet). It
BALANOGLOSSU& 157
lives under stones at or below low-water mark on the coast
of New England southwards to South Carolina.
Order 2. Enopla. — In the members of this group the
proboscis is furnished with a style. Eepresentatives of the
order are the species of Tetrastemma ( T. serpentinum
Girard, Fig. 107) and of Nenierti's. The former is a little
yellowish worm, common tinder stones on the coast of New
England between high and low- water mark ; it has a slightly
marked head with four dark eye-specks.
CLASS VI.— NEMERTINA.
Body ribbon-like or cylindrical, soft, extensible, ciliated externally, with
a, proboscis in a sheath opening by a pore situated above the mouth. Cir-
culatory system approaching that of the Annulata. Sexual organs, duct-
leas sacs ; either with or without a metamorphosis.
Order 1. Annpla. — Proboscis without a style. (Linens, Meckelia.)
Order 2. Enopla. — Proboscis with a style. (Nemertes, Malacobdella.)
CLASS VII. — ENTEKOPNEUSTA (Acorn-tongue worms}.
General Characters of the Enteropneusta. — The re-
markable worm, Balanoglossus (Fig. 108), the type of this
class, combines characters peculiar to itself, with features
reminding us of the Nemerteans, Annelids, Tunicata, and
even the vertebrate Amphioxus, while its free-swimming
larva was originally supposed to be a young Echinoderm.
From the fact that the central nervous system lies above a
notocord, Bateson places it next to the Vertebrates.
Balanoglossus auraniiacus (Girard, Fig. 108) is a long,
cylindrical, soft, fleshy worm, footless, without bristles, but
with a large, soft, whitish tongue-shaped proboscis in front,
arising dorsally within the edge of the collar surrounding
the mouth. At the beginning of the digestive canal is a
series of sac-like folds, of which the upper or dorsal portion
is respiratory, and separated by a constriction from the lower,
158
ZOOLOG Y.
which is digestive, and leads directly to the intestine behind.
This pharyngeal respiratory portion of the digestive canal has
on each side, in each segment, a dorsal sac, the two commu-
nicating along the median line of the body. The dorsal re-
spiratory sacs bear in their walls a delicate chitinous gill-
support or arch. Between the gill-arches, forming numerous
lamellae, are a series of slits, leading on each side to open-
ings (spiracula) situated dorsally. The water passes through
the mouth into each gill-sac, and out by the spiracles. The
nervous system lies above a notocord. There is a dorsal
vessel, which sends branches to the respiratory sacs, and a
Fio. 108.
-pro. 109.
Fijr. 108. — BalanOfflosmts, not fully mature; magnified.
Fig. 1'Jit — Larva ( Tornaria} of Batanoglossus. a, anus; b, branch of water-vascu-
lar system leading to the dorsal pore , of ,• e, eye-speck ; g, g 11s ; A, heart ; t, in-
testine; m, moutn; m', muscular hand from the eye to the water-vascular tube ; o.
oesophagus ; ,«, stomach or alimentary canal ; ;/, lappet of stomach ; u\ auul band of
cilia ; w, water-system.— After A. Agassiz.
ventral vessel. The worm lives in sand at low-water mark
from Cape Ann to Charleston. S. C.
The life-history of this worm is most interesting. The
young, originally described under the name of Tornaria,
was supposed to be an Echinoderm larva, though it closely
resembles the larval Gephyrea and Annelides. It is a trans-
parent, minute, ciliated, slender, somewhat bell-shaped form
(Fig. 109), with black eye-specks. When transforming to
the worm condition, a pair of gills arise on sac-like out-
growths of the oesophagus, and afterwards three additional
ANATOMY OF PHASCOLOSOMA. 159
pairs with their external slits arise, somewhat as in Ascidians.
The entire Tornaria directly transforms into the worm, the
transitional period being very short. The body lengthens,
the collar and proboscis develop, and the worm eventually is
as seen in Fig. 108; afterwards the body lengthens, the end
tapering and becoming much coiled.
CLASS VII.— ENTEROPNEUSTA
Footless, smooth-bodied worms ; with no bristles, a large exserted soft
fleshy proboscis ; brent/ting by a series of dorsal respiratory sacs opening
into the digestive canal, and communicating externally by spiracles ; the
nervous system situated above a notocord. (Balanoglossus.)
CLASS VIII. — GEPHYEEA (Star-worms).
General Characters of the Gephyreans.— The most acces-
sible type or representative of this small but interesting group
of worms is a large, smooth, cylindrical worm from six to
ten inches long, which is common in sand or sandy mud at
low-water mark. It is the Sipunculus or Pliascolosoma
Gouhlii Diesing, and from its abundance and large size, as
well as the ease with which it can be preserved in spirits, is an
excellent subject for the laboratory, serving as an example of a
very aberrant type of worm as compared with the earth-
worm, or with a Nereis. The body is as smooth as a pipe-
stem, and about that size, unarmed, with a circle of numer-
ous small, flat, foliaceous tentacles around the month. On
laying open the body from the head to the extremity (Fig.
110), the body-walls are seen to be lined with fine longi-
tudinal flat muscles, with two unequal pairs of large white
retractor muscles, the anterior third of the body being
highly retractile. The intestinal part is found to float free-
ly, though anteriorly attached to the walls by a few muscu-
lar threads, in the capacious body-cavity, and is usually full
of fine mud. The oesophagus is long and slender, situated
between the shorter pair of retractor muscles ; behind the
160
ZOOLOO Y.
insertion of the muscles it enlarges, but there is no true
stomach ; it is about twice the length of the body, and is bent
and twisted on itself, ending
dorsally in a vent marked by an
external wart, on the anterior
third of the body. Near this
point is situated a pair of large,
long, slightly twisted segmcntal
organs(s)thefree ends of which
flare slightly. The nervous
system (n) forms an oesophageal
ring, and from it passes a well-
marked ventral single cord,
from which at short intervals
pass off small short lateral
nerves. The vascular system
is represented by a circular
vessel lying next to the ner-
vous oesophageal ring, sending
branches into, or at least in
communication with, the cavi-
ties of the tentacles, and from
the ring passing along and in-
timately connected with the di-
gestive tract, forming a ruffle-
like organ (v), ending at a point
nearly opposite the vent (a).
Prof. Greef finds that the vas-
cular system of Echiurus con-
sists of two main vessels, i. e.,
a dorsal and a ventral vessel ;
the former extending along the
°
°
Fig. 110.— Anatomy of Phascolosoma
Gouii/u, cut open, with the flaps pinned alimentary canal, and sending
down, ce, oesophagus ; ai\ two short
muscles ; pr, two long r.-tractor mus- a branch to the proboscis, where
cles ; », next to a dark line the right .,..•_. ,
side of the long oesophagus indicating it divides into two branches,
the water-vascular tube; n, nervous , ... .,, ,,
cord; s, segmental organs; the long, each Uniting With the VClltral
twisted intestine returns, ending at a •• rm 11 i • i 1
Natural size.-Drawn by J. S.Kings- VCSSel. lllC blood IS pale yel-
lowish, with corpuscles. The
blood-system of the Gephyrea, then, is homologous with
DEVELOPMENT OF GEPHYREANS. 161
that of the Annulata. There is in Phascolosoina no true
ovary, but the eggs flout in masses in the capacious body-
cavity, the animal being a hermaphrodite.
Phoronis is from the highly developed crown of long,
slender tentacles, and its complicated blood-system, remark-
ably like the tferpitlce, with which Annelids it is by some
authors associated. The alimentary tube, however, is like
that of Phascolosoina, the intestine folded and ending next
to the mouth. No nervous system has been detected. A
pulsating artery is attached to the upper side of the long
oesophagus, and its branches go into the tentacles from an
cesophageal ring. " Two venous trunks open from the sin-
uses above and behind the arterial branches, and then pro-
ceed downwards, half encircling the oesophagus, till they
unite in a large vessel on its neural surface." (Dyster. )
This worm is minute, about four millimetres in length, and
lives in a tube buried in holes in rocks. It has a strong re-
semblance to a Polyzoon, but connects the Gephyrea with
the true Annelids.
In the Sipunculus-like worm Phascolosoma, and in Pho-
ronis, there is a well-marked metamorphosis, and the larvae
are somewhat like those of Annelids. The larva of Phas-
colosoma is cylindrical, the head small, with a circle of cilia,
but there are no arms as in the larva of the Phoronis.
The earliest observed stage of Phoronis * is a free-swim-
ming larva, the body transparent, ciliated, with an umbrella-
like expansion on the head, covering the region of the mouth,
while the end of the body is truncated. At this stage it is a
true Cephalula, like that of Echinoderms and worms. Af-
terwards four projections arise at the end of the body, and
twelve long, arm-like projections grow out, the larval form
now being fully attained. In this condition it was de-
scribed as a mature animal under the name AcMnotrocha.
When the Actinotrocha is about to transform into a Pho-
ronis the end of the intestine bends up, opening outward
* In our Outlines of Comparative Embryology this account of the
metamorphosis of Phoronis is by mistake regarded as descriptive of
Sipunculus on pp. 157, 158, under Development. The word Phoronis
on those pages should be substituted for Sipunculus.
162
ZOOLOGY.
near the mouth. The umbrella is gradually withdrawn into
the mouth, so that eventually only a crown of short tooth-
like projections surrounds the mouth. Finally the whole
umbrella is swallowed, the arms at the end of the body dis-
appearing, while the end of the intestine projects far out
from the body behind the mouth. By this time the Phoro-
11 i* form is clearly indicated, the body being long and slen-
der and the mouth surrounded by a crown of short tentacles,
the end of the intestine being entirely withdrawn Avithin the
body. These changes are rapidly effected. The larva or
Ecliiurus is formed on the Annelid type.
In Phascolosoma ccementarium (Quatrefages), the body is
much shorter than in P. Goul-
dii ; the worm lives in compara-
tively deep Avater (10 to 50 fath-
oms), in dead, deserted shells,
building out the aperture by u
conical tube of sand. In Sipun-
culus (Syrinx) the tentacles are
fringed or lobed. It does not
occur in American waters.
In £cJni(rnsi\w intestine ends
at the end of the body, and there
is a circle of bristles at the pos-
terior end, Avhile BoaeUut differs
in having an enormous proboscis,
and only a feAV bristles near the
head. In Bonellia rfn't/ix Rol.
of the Mediterranean (Fig. Ill),
the proboscis is deeply forked ;
the intestine is very long, convo-
luted, and into the cloaca empty
two excretory organs. The ovary
is a cord-like organ, Avhich in the
posterior part of the body is fast-
ened to the intestine.
Clicrlodcnna 'iiitidnluin Loven
occurs in 20-40 fathoms off the coast of Europe and
Northern New Enffluiul. The body is long, cylindrical, and
.9
Fig. Ml.—Bonellia rirMis ; the
proboscis coiled several times, p,
lore end of the proboscis ; s, sf, fur-
row in the proboscis ; i,i, digestive
canal ; m, mesenterial threads (only
shown on the anterior end of the di-
gestive canal) ; g, organs of excre-
tion ; c, cloaca ;' w, ovidvu/ — After
Lacaze-Duthiers ; from Gegenbaur.
CHARACTERISTICS OF GEPHYREANS. Ili3
covered with slender, firm, calcareous spines. It has no
tentacles, a straight digestive canal, the vent being terminal,
and two internal gill-sacs, with external lamellate gills.
Instead of a single nervous cord, as usual in the Gephyrea,
in ChcBtoderma there are two separate nerve-cords, one on
each side of the body. The Gephyrea were formerly asso-
ciated with the Echinoderms, but the resemblance is only a
superficial one.
CLASS VIII.— GEPHYREA.
Body long, cylindrical, smooth, or spiny, or provided with bristles, not
segmented; uxaally a large proboscis, but none in Phaficolosoma ; vent
either terminal or situated dorsaliy on the anterior end of the body. A
true blood-system homologous with that of the Annulata. Bisexual or
hermaphroditic ; young of the Annelid type, undergoing a metamorpho-
sis. (Chsetoderma, Pkascolosoina, Sipunculus, Bonellia, Echiurus, and
Phoronis.)
Laboratory Work. — The common star-worm, Phascolosoma, is one
of the easiest worms to dissect, aa it can be readily laid open with
the scissors, and the skin pinned down on the bottom of the dissecting1
trough, when the parts can be readily distinguished, its structure being
unusually simple.
CLASS IX. — ANNULATA (Leeches., Earth-worms, and
Sea-worms).
General Characters of the Annulata. — This group, rep-
resented by the leeches, earth-worms, and nereids or bristled
sea-worms, tops the series of the classes of worms, and in
the highly specialized, regularly segmented bodies, with their
sense-organs and highly differentiated appendages, stand
nearer the Crustacea and Insecta than any other class of in-
vertebrate animals, their internal organization on the whole
being nearly as complicated.
Reference to the accompanying diagram (Fig. 112) will
show the general relation of the organs of an Annelid to the
body-walls, as compared with corresponding parts, when seen
in sections of Amphioxus and a fish.
164
ZOOLOGY.
The student, in familiarizing himself with the structure
and mode of growth of the leech, the common earth-worm
Fig. 112.— Transverse section of a worm, of Amphioxus, and a higher vertebrate
contrasted, a, skin ; b, dermal connective layer; c, muscles; d, segmented organ ; h,
arterial, and i, venous blood-vessel ; g, intestine ; I, notochord.— After Haeckel.
and the Nereis, will obtain a good idea of the essential char-
acteristics of the entire class.
Order 1. Hirudinea. — In the leech (Fig. 113), Hirudo
medicinalis Linn., the type of the first and lower order, the
body is somewhat flattened and divided into numerous short,
indistinctly marked segments, not bearing any bristles or
appendages. The head is small, with no appendages, bear-
ing five pairs of simple eyes, while each end of the body ter-
minates in a sucker. The mouth is armed internally with
three pharyngeal teeth arranged in a triradial manner, so
that the wound made in the flesh of persons to whom the
leech is applied consists of three short, deep gashes radiating
from a common centre. The stomach (Fig. 114) is large,
with large lateral diverticula or lobes, while the intestine is
small. The nervous system consists of a "brain" and ven-
tral ganglionated cord.
The vascular system is complicated, consisting of a median
dorsal and a ventral vessel, and two lateral vessels ; all these
anastomose or interbranch, and the blood which courses
through them is red, but is said to contain no corpuscles.
The segmental organs, so characteristic of the Annulata,
are well developed in the leech, consisting of about seventeen
pairs of tubes opening at one end at regular intervals on the
under side of the body, and ending in a non-ciliated coil
(Fig. 1 1:;, r) in the leech, or in the smaller fish-leech, Clep-
sine, open into the venous sinus by ciliated, open mouths.
ANATOMY OF THE LEECH.
165
•to
FIG. 114.
Fig. 113.— Anatomy of the medicinal leech;
opened from below, a, h, buccal sucker ; b, infra-
cesophageal ganglion; e,e,e, ventral ganglia; d, last
ganglion ;/,/,/. commissures joining the ganglia;
g, g, g, nerves of sense and locomotion ; i, oesopha-
gus ; k, k, k, k, the dilatations or coeca of the stom-
ach ; in, the last of these lobes or coeca ; p,p, intes-
tine lying, as well as the stomach, above the ner-
vous chain ; q, rectum ; r, r, r. segmental organs ;
s, pouch ; x, sheath of 2, coupling organ • t, ri^ht
epididymis; A, A, A, spermatic cords; 'B, £, £,
testes ; />, matrix ; E, E, ovaries ; w, end of ovi-
duct; v, sucker.
Fig. 114. —Digestive canal of the same ; a, b, b,
b, b, the stomach and its lateral lobes or cceca; </, c,
the two large coeca which extend ahum i-.-ich side
of the intestine e, e ; f, rectum.— Alter Gervais aud
Van Benedeii.
FIG. 113.
166 ZOOLOGY.
The leech is hermaphroditic, while in certain allied forms
{Histriobdella, etc.) the sexes are distinct.
The eggs of leeches are laid in sacs, or, as in Cle/>*i//r. the
fish-leech, are covered with a transparent fluid substance,
which hardens and envelops the eggs. The Clepsine re-
mains over the eggs to protect them until they hatch ; and
the young, after exclusion, fix themselves to the under side
of the parent, and are thus borne about until they are fully
developed and able to provide for themselves (Whitman*).
The changes in the egg of Clepsine, after fertilization, are
very complicated, and have been described by Whitman.
The egg subdivides into a bilateral mass of cells called a
blastula;\ a gastrula, and finally a "neurula*' stage, charac-
terized by the formation of a "primitive band'' like that of
insect embryos. Soon after attaining the latter stage the
embryo hatches and attaches itself to its parent. The mouth
is then formed, the nervous systemj arises from the ecto-
derm, the segments are indicated, the original number being
thirty-three, the segmental organs develop from the meso-
derm at about the time of hatching, and about six days after
the neurula leaves the ess the eves become visible. The
OO i
innermost germ-layer (endoderm) does not arise until eight
days after hatching, and by this time the digestive tract is
perfected ; the muscular walls of the alimentary canal being
derived from the mesoderm.
* The Embryology of Clepsine. By C. O. Whitman. Quarterly
-Journal of Microscopical Science. July, 1878.
f Whitman states that a nioruld, as delim-d by Ilaeckel, does not
occur in the developmental history of Clrpxine, and he states that when
the cleavage process of the egg has been carefully studied it has been
found to result in the production of a bilateral germ or lilnxtnlrt, and
not a morula. "'A solid sphere of indifferent cells' is, to say the
least, a very improbable form, si improbable that its existence may be
held questionable until established by positive evidence. The doubt
is all the more justifiable, as more careful investigation has in many
•cases already shown that the so-called mulberry stage is not a morula,
but a blastula or even a gastrula." (Whitman.)
\ There is originally a pair of ganglia in each of the thirty-three
segments ; four of these are consolidated into the subcesophageal gan-
glia, eight in the ganglia of the disk, and four in the terminal ganglia
of the body. (Whitman.)
EMBRYOLOGY OF LEECHES. 1G7
The early phases in the embryo-logical development of the
leech (Clepsine] strongly resemble those of corresponding
stages in the vertebrates, according to a number of observers.
The origin of the germ-bands, the presence of the primitive
streak as well as the mode of cleavage, and the formation of
the gastrula* and neurnla, show that, up to a comparatively
late period of embryonic life, some worms (Annulata) and
the Vertebrates travel along the same developmental path.
As observed by Whitman, the neurula of the chick, or of
the fish, belongs to the same type as that of Clepsine.
Whether the Vertebrates ever descended from the worms or
any other type of Invertebrates or not, it is a matter of fact
that there is an essential unity in organization and mode of
•/
early development in all the Metazoa, or three-germ-layered
animals, and that the vertebrates are probably only a very
highly specialized group of animals, a branch of the same
genealogical tree from which have sprung the only less
generalized groups or branches of Molhtsca, A nun Jut a, and
Artliropoda. Certainly the division of the animal kingdom
into Vertebrates and Invertebrates, however useful, is essen-
tially artificial and misleading. Hence it follows that a
study of the Annulata, as well as other types of worms, must
prove to be fruitful in valuable results, and lead to what
may seem startling conclusions.
«/
Order 2. Annelides. — To this order belong the earth-
worm and sea-worms. The structure of the common earth-
worm (Lunibricu* tcrrcxtrix Linn., Fig. 115) is essentially
like that of the leech. Externally the body is cylindrical,
many-jointed, the joints or segments much more distinct
than in the leech, and internally there are septa, or thin
muscular partitions, between them. The mouth is small,
forming an opening on the under side of the first segment.
On, or next to, the twenty-ninth to the thirty-sixth seg-
ments in Lumbrirus terrestris is a flesh-colored swollen
portion called the cinrjulum or clitellum.
The earth-worm is able to climb perpendicularly up boards,
* Professor His achnits that the bird passes through a stage compar-
able with the gastrula of other animals. (Whitman, p. 94.)
168
ZOOLOGY.
etc., as well as over the ground, by minute, short, curved
setae or bristles, which are deeply inserted in the muscular
walls of the body, and arranged in four rows along each side
of the body. The alimentary canal is straight, the stomach
lias three pairs of small lateral blind sacs (coeca), and the
intestine, which is externally tubular, contains a thick inter-
nal sac-like fold called a typhlosole.
The segmental organs are highly convoluted tubes, a pair
to each segment of the body, except a few near the head,
and opening internally with ciliated funnels and externally
in minute pores situated along the under side of the body.
The earth-worm is monoecious (hermaphroditic).
The oviducts open in the fourteenth segment, and the
seminal ducts (yasa deferential) in the fifteenth. Between
the ninth and tenth, and the tenth and eleventh segments
are the four openings of the seminal receptacles (receptacula
seminis). Pairing is reciprocal (see Fig. 115), each worm
fertilizing the eggs of the other; they pair from April to July
in the night-time. The eggs of the European Lnmlricus
rubellus Grube are laid
in dung, a single egg in
a capsule ; L. ayricola
lays numerous egg-cap-
sules, each containing
sometimes as many as
\j
fifty eggs, though only
three or four live to de-
velop. The development
of the earth-worm is like
that of the leech, the
germ passing through a
morula, blastula, gas-
rig 115 —Earth-worms pairing. After Curtis. ,
a, embryo (blastula) soon after segmentation of tlTlla aiKI neui'Ula Stage,
the yolk ; b, embryo further advanced ; o, mouth; , -, -, •,
c, embryo still older ; k, primitive streak ; d, the WOrm, When liatdl-
neurula;o,it8mouth.-AfterKowalevsky. ^ resembling the pa-
rent, except that the body is shorter and with a much less
number of segments.
While the earth-worms are in the main beneficial, from
their habit of boring in the soil of gardens and ploughed
ANATOMY OF NEREIS V1RENS.
1G9
lands, bringing the subsoil to the surface and allowing the
air to get to the roots of plants, they occasionally injure
young seedling cabbage, lettuce, beets, etc., drawing them
during the night into their holes, or uprooting them.
The next and highest type of Annulata is the common
sea-worm of our coast, Nereis virens Sars. It lives between
tide-marks in holes in the mud, and can be readily obtained.
The body, after the head, eyes, tentacles and bristle-bearing
feet have been carefully studied, can be opened along the
back by a pair of fine scissors and the dorsal and ventral red
blood-vessels with their connecting branches observed, as
well as the alimentary canal and the nervous system.
The anatomy of this worm has been described by Mr. F.
M. Turnbull. It is very voracious, thrusting out its pharynx
and seizing its prey with its two large pharyngeal teeth. It
secretes a viscid fluid lining its hole, up which it moves,
pushing itself along
by its bristles and </ « ^V \ f
ligulse. At night,
probably during the
b r e e d i n g season,
they leave their
holes, swimming on
the surface of the
water.
The body consists
of from one hundred
to two hundred seg-
ments. The head
consists of two seg-
ments, the anterior
and buccal, the for-
mer with four eyrs
and two pairs of
antenna?. The sec-
ond segment bears
four antennae (tentacular cirri). Each of the other segments
bears a pair of paddle-like appendages (rami), which may be
best studied by examining one of the middle segments which
Fig. 116. — Vertical section through the integument
of an Annelid (Sph&rodorum), c, thick cuticular
1 lyer with the pore-canals ; m, muscular layer ; m',
muscles of the bristles, s, which retract the central
foot-lobe, while others pass to its dorsal glandular
projection, d.— After Gegenbaur.
1TO ZOOLOGY.
has been separated from the others. For the finer structure
of the body-walls see Fig. 11G.
The alimentary canal consists of a mouth, a pharynx
armed with two large teeth and much smaller ones. The
pharynx is entirely everted during the act of taking its food.
Into the oesophagus empty two large salivary glands ; the
remainder of the alimentary canal is straight and tubular.
The circulatory system is very complicated ; it is closed and
the blood is red. Both the dorsal and ventral vessels are
contractile, the blood flowing forward in the dorsal vessel.
and backward in the ventral vessel. The two small vessels,
one on each side, in each segment of the body, branch off
from the ventral vessel and subdivide, each sending a branch
to the ventral ram us of the foot of the segment behind, and
another larger branch around the intestine to the dorsal ves-
sel, receiving also, on its way, a vessel from the upper ramus
of the foot of its own segment. "Besides these principal
lateral vessels, there are five other vessels on each side
in each segment, coming from the ventral vessel. These
form a loose but regular net-work that surrounds the in-
testine and is connected with five other convoluted vessels,
which join the dorsal vessel. This net-work on the intestine
probably supplies the hepatic organ with material for its
secretion, and very likely may receive nutritive material from
the digested food." (Turnbull, Trans. Conn. Acad., iii. lS7f>.)
The blood is aerated in the finer vessels of the oar-like feet
and in those situated about the alimentary canal. The
nervous system consists of the " brain" and ventral double
ganglionated cord.
The sexes of Nereis virens are separate ; the eggs during
the breeding season fill the body-cavity, and pass out through
certain of the segmental organs, which act as oviducts, while
others, probably the more anterior ones, are excretory, like
the kidneys of vertebrates, as urea has been detected in them.
These organs are situated at the base of the lower ramus of
each foot. In some species of the CapitellidcB Eisig has found
that it is normal for several segmental organs to be present
in a single segment.
While the mode of development of our Nereis has not
LAR V^E OF ANNELIDS.
171
been studied, the eggs are probably laid in masses between
tide-marks, and the young, when hatched, swim freely on
the surface of the sea. The eggs of other worms are carried
about in lateral pouches. The germ undergoes a cleavage
phase and a gastrula stage. We have observed, in Salem
harbor, the development of Poly dor a (probably P. ciliatum
Clap.) which maybe found in August, in all stages, on the
Pi;*. 117.— A, earliest observed stage of Polydora; B, Ccphalula stage ; C"andZ>,
later stages.— Author del.
surface of the water. When first observed (Fig. 117, A] the
body was spherical, with a short, broad intestine, and two-
sets of large locomotive bristles. It then passed into the
cephalula state, the head clearly indicated and forming a
large hood. This stage is seen at B, which represents the
under side of the cephalula, the mouth being -situated be-
tween the two large ciliated flaps (like the velum of larval
mollusks) of the hood ; the body is now segmented, with a
third set of bristles and a band of cilia on the penultimate
segment ; afterwards as at C, dorsal view, additional rings
are present ; the eyes are distinguishable, and there are two
more sets of bristles. The new segments are, as usual in all
172
ZOOLOGY.
articulates, interpolated between the penultimate and ter-
minal segments of the body. At D, the body is many-
jointed, the tentacles well developed, the large temporary
bristles have been discarded, and the worm can be identified
as a young Polydora.
It is probable that Polydora is hatched as a trochosphere
like that of Polyzoa, BracMopoda and certain mollusks.
The young Terebrellides fitroemii, and of Lumbriconereis,
are at first trochospheres, i. e., the free-swimming
germ is spherical, with a zone of cilia, two eye-
spots, and no bristles. Thus the earliest stages of
Polyzoa, Brachiopoda, Lamellibranchiata, Gastro-
poda, and even of a Cephalopod (Fig. 215), Nemer-
.— tina, and Annelides are almost identical. Farther
doce0- al°ng ^n their developmental history, the cepha-
After A. Ag- hila of the Annelides (Figs. 117, A, B, and 119),
is like that of certain Echiuoderms (Fig. 119),
Gepliyrea, Polyzoa, Brachiopoda, and Mollusca. It may
here be observed that the free-swimming larva? of these types
of invertebrate animals are the young of more or less seden-
Fig. 119.— Cephalula stage of Echinoderms and Worms, lateral view. A. Holo-
thunan, B, Star-fish, O, D, of Anuelides.
o, mouth ; i, stomach ; a, vent ; v, prseoral ciliated band, in B, C, D, independent ;
in A surrounding an oral region. — From Gegenbaur.
tary parents. In this way the species becomes widely dis-
tributed through the action of the marine currents, and too
close in-and-in breeding is prevented.
Certain Annelides sometimes multiply by self-division, the
process being called strobilation. This is commonly observed
BUDDING Of ANNELIDS.
173
in the fresh-water worm Nais, also in Syllis and Mynanida,
as well as in Filoyrana, Protula, etc. Autolytits, a com-
mon worm on the coast of New England, produces one gen-
eration by budding (parthenogenesis). There is, in fact, an
alternation of generations, an asexual Autolytus, giving
FIG. 120.
PIG. 121.
Fig. WO.—Clymenflla tprquata.— After Verrill.
Fig. \2\.—Amphitrite cirrata, enlarged twice, ft, branchia ; c, uncini, enlarged 50C
diameters. — After Malmgreii.
rise to a brood of males and females, the sexual and asexual
forms being so unlike each other as to have been mistaken
for different species and even genera.
In Syllis and allies certain long, slender processes of the
174
ZOOLOG Y.
feet are jointed, thus anticipating the jointed appendages of
the Crustacea and Insects.
The Annelides are divided into two suborders. The first
suborder, Oligoclmta, comprises Lumbricus, Nais, etc., while
the second suborder, Chcetopoda, embraces Syllis, Autulytus,
Nereis, Polydora, Aphrodite, and Polynoe, which are free-
swimming, while the tubicolous worms which respire by spe-
FIG. 123. FIG. 123.
Fig. ISi.—Cistenides Gmtldii, and its tube.— After Verrill.
Fig. IHS.—Euchone elegans, enlarged.— After Verrill.
cial branchiae, or gills, on the head, live in tubes of sand or
in limestone shells. Those which live in sand or mud-tubes'
are Cirratulus (Fig. 124), Clywene and Clymenella (Fig. 120),
which has no branchiae, Amphitrite (Fig. 121), Terebrelht,
Cistenides (Fig. 122), Habella, and Enchone (Fig. 123),
while Frotula, Filof]rana, Serpula, and Sjiirorbis secrete
more or less coiled limestone tubes. The large solid shells
of the Serpulae assist materially in building up coral reefs,
SILURIAN WORM TRACKS.
175
especially on the coast of Brazil. The minute nautilus-like
shells of Spirorbis live attached to the fronds of sea-weeds,
especially the different kinds of Fucus.
Fig. 124.—Cirratitlus grandis.— After Verrill.
Many sea-worms are highly phosphorescent, the light emit-
ted being intensely green. The tracks of worms like the
Nereis of to-day occur in the lower Silurian slates ; their
bristles, however, were spinulose, as in the larval worms.
Thus the type, though highly specialized, has, unlike most
specialized groups, a high antiquity, the specialized Anne-
lides existing side by side with the generalized Polyzoa and
Bracliiopoda. At the present time the Annelides are Avidely
distributed in the seas of the globe, the tropical forms being
exceedingly abundant among coral stocks and in sponges,
while the arctic seas abound with Annelid life. They also
sparingly exist at great depths, one species of a worm allied
176
ZOOLOGY.
to Clymene, having been dredged by the Challenger Expedi-
tion at the enormous depth of over three miles (about 5000
metres).
CLASS IX.— ANNUL AT A.
Body long, bilaterally symmetrical, cylindrical, consisting of numerous
•segments, either unarmed, or more usually provided with setce alone or with
setae, and paddle like appendages (rami). Head simple, with a few simple
eyes, or provided with tentacles (antennae) alone, or with tentacles and bran-
chiae. An eversiblepJiary i) x, armed with teeth, usually present. Alimentary
system straight, the tubular stomach sometimes sacculattd ; vent always
situated in the last segment of the body. Nervous system icell developed,
consisting of a brain and ventral ganglionated cord. Circulatory system
closed, with a dorsal and ventral and lateral vessels connected by anasto-
mosing branches in nearly each segment. A system of numerous paired
segmental organs. Sexes united or separate. Embryo passing through
a cleavage-stage (morula or blastula), gastrula, sometimes a neurula stage,
and after hatching, development is either direct or there is a marked met-
amorphosis, the larva passing through a trocJiosphere and cephalula
stage.
Order \. Hirudinea. — Body unarmed, finely segmented ; with a pos-
terior sucker. (Hirudo, Nephelis.)
OrderS. Annelides. — Suborder 1. OliffocJicetaCLumbricus, Nais). Sub-
order 2. — Ghcstopoda (Arenicola, Syllis, Autolytus, Aphro-
dite, Polynoe, Amphitrite, Terebrella, Sabella, Serpula,
Spirorbis).
TABULAR VIEW OF THE CLASSES OP WORMS (VERMES).
Annulata.
Brachiopoda.
Enteropneusta.
Gephyrea.
Polyzoa.
Nemert
1
xiota
'na.
Ne'>
natelm
Plat
VERMES.
ANNUL ATA. 177
Laboratory Work. — Worms should be dissected at once after be-
ing killed by ether or in alcohol, before the circulation has ceased ;
and transverse sections made to observe the relation of the appendages
to the body-walls, and of the different systems within the body-walls.
The worms should also be hardened in alcohol, and. thin sections
stained with carmine be made for histological study. A portion of the
worm can be put in paraffine and sliced by hand with the razor or by
the microtome.
LITERATURE.
Platylielminthes and Parasitic Warms.— Van Benedeu's Animal Para-
sites and Messmates, 1876. Leuckart's Human Parasites. Works of
Rudolphi, Diesing, Van Benedeu, Kuchenmeister, Siebold, Graff,
Lang, Kennel, Thomas, Sommer, Liu ton, etc.
Nematoda. — Works of Schneider, Meissner, Bastian, Biltschli,
Fedschenko, etc. For Trichina, the treatises of Leidy, Leuckart, Zen-
ker, Virchow, Pageustecher, etc.
Gordiacea. Works of Villot (Ann. Sc. Nat.), Vejdovsky (Zeits.
f. w. Zool., 1866 and 1888).
Acanthocephala. — Works of Greef, Schneider, Andres, Baltzer,
Safftigen.
Rotatoria. — Works of Ehrenberg, Leydig, Cohn, Hudson, Gosse,
Salensky, etc.
Polyzoa. Works of Allman, Hinks, Smitt, Nitsche, Saleusky, Sars,
Hyatt, Barrois, etc.
Brachiopoda. — A. Hancock: On the Organization of the Brachi-
opoda (Phil. Trans., 1858). E. 8. Morse: On the Systematic Position
of the Brachiopoda (Proc. Boston Soc. Nat. Hist., xv. 1873). With
the essays of Brooks, Lacaze-Duthiers, Kowalevsky, Beyer, Dall,
Davidson, etc.
Nemertina. — Essays of De Quatrefages, Mclntosh, Hubrecht, etc.
Gepliyrea. — Writings of Grube, Lacaze-Duthiers, Keferstein, Hat-
schek, Selenka, etc.
Annulata. — Darwin: Formation of Vegetable Mould through the
Action of Worms. Anatomy of the Earth-worm in Sedgwick and
Wilson's Biology, chapters 7-10. Wilson's Embryology of the Earth-
worm, 1889. Anatomy of Polygordius in Parker's Biology, Lessons
25-26, based on Fraipont's monograph in Fauna und Flora des Golfes
von Neapel, xiv. 1887. Eisig : Die Capitellideu des Golfes von Neapel
(ibid., xvi. 1887). Ehlers : Report on the Annelids of Florida (Mem.
Mus. Comp. Zoology, xv. 1887). With the works of Claparede,
Ehlers, Semper, Meyer, A. Agassiz, Hatschek, Metschuikoff, Verrill,
Wilson, Whitman, etc.
CHAPTER V.
BRANCH V.— ECHINODERMATA (STAK-FISH, SEA-
UKCHINS, SEA-CUCUMBEKS, ETC.).
General Characters of Echinoderms. — We next come to
animals which are now thought to have originated from some
bilateral, worm-like form, but in which the radiated arrange-
ment of the parts of the body is in most cases as marked
as the jointed or ringed structure of worms or insects ; for
not only are the body-walls of the star-fish or sea-urchin, or
even many of the Holothurians (though less plainly), di-
vided into five wedge-shaped portions (spheromeres), or pro-
duced into five arms as in the common star-fish or five-
finger, but the nervous system, the reproductive organs,
the blood and water-vascular systems, and the locomotive
appendages of the latter, are usually arranged in accordance
with the externally radiated form of the body. Still these
animals are in many cases, as in the higher sea-urchins,
plainly bilateral, while in the larval forms of all Echino-
derms whose development is known the young are not
radiated, but more or less bilateral, as in the larvae of worms
and mollusks. The most trenchant character, however,
separating the Echinoderms from the Coelenterates, and ally-
ing them to the worms, is the genuine tube-like digestive
canal which lies free in the body-cavity (perivisceral cavity),
and may be several or many times the length of the body.
The student can gain a correct idea of the general struc-
ture of the Echinoderms from a careful examination of the
common star-fish (Aster-las vulgaris Stimpson), which is the
most common and accessible Echinoderm to be found on the
New England shores. After placing a star-fish in some sea-
water and noticing its motions, the thrusting out of the am-
bulacral feet or suckers by which it pulls or warps its clumsy
STRUCTURE OF COMMON STAR-FISH. 179
body over the mussel-beds, or rocks, or weeds, the arms
being capable of slightly bending ; after observing the red
eye-spot at the end of each arm or ray, and the movements
of the numerous spines which are attached to the separate
plates forming the calcareous framework of the body-
walls, and examining the movements of certain modified
spines called pedicellarice, which are pincer-like bodies situ-
ated among the spines, the student will be ready to study
the external and internal anatomy.
First, as to the calcareous framework of the star-fish.
In order to study this, a transverse section should be made
through an arm, and a vertical one through the body and
along the middle of a single arm, and finally the animal
should be divided into two halves, an upper and lower. It
will then be seen that the calcareous framework or so-called
skeleton consists of a great number of limestone plates or
pieces attached by a tough membrane and covered by the
skin. Between the plates are spaces by which the water enters
the body-cavity through the skin. These plates are arranged
so as to give the greatest strength and lightness to the body.
There is also to be seen an oral (actinal) side on which the
mouth is situated, and an aboral (abactinal) side, the re-
spective limits of which areas vary greatly in the different
groups of Echinoderms. Each arm or ray is deeply chan-
nelled by the ambulacral furrow containing four rows of
suckers or " ambulacral feet," which are tentacle-like
protrusions of the skin growing out through orifices in
the ambulacral plates, and are a continuation of the water-
sacs or " ampullae '" within. The madreporic plate is a
flattened hemispherical body situated on the disk between
two of the arms. It is perforated by canals.
The nervous system of Echinoderms consists of a plexus of
cells and fibres overlying the surface of the shell. The oral
ring and radial nerves may be seen without dissection. By
closely examining the mouth, a pentagonal ring is seen sur-
rounding it, each angle slightly enlarging* o.ud sending off
* Owfsiannikoff states that the nervous ring is a flat band, con-
taining no swellings or ganglia, and not differing in structure from the
ambulacral nerves, which latter possess nerve-cells as well as fibres.
180
ZOOLOGY.
a nervous cord to the eye at the end of the ray. It may be
discovered by pressing apart the ambulacral feet along the
median line of each arm. Fine nerves are sent off to each
sucker, passing through the opening between the calcareous
plates and extending to eacli ampulla, thus controlling the
movements of the ambulacral feet.
am, ampullae, the ambulacral feet projecting below; b, coeca or liver.— Drawn by
A. F. Gray, under author's direction.
The mouth (Fig. 125, m) is capacious, opening by a short
oesophagus into a capacious stomach (Fig. 125, .<?) with thin
distensible walls, and sending a long lobe or sac (Fig. 125, /)
into the base of each arm; each sac is bound down by two
retractor muscles attached to the median ridge lying be-
tween the two rows of water-sacs (ampullae, see also Fig. 126).
a C~^
Fig. 126.— Diagram of the water-system of a star-fish, a. madreporic body: 6,
stone-canal; c. circumoral water-tube; d. water-tubes to the arms; e, ampullae;
/, feet or suckers.— After Brooks.
The stomach ends in an intestine. The intestine suddenly
contracts and ends in a minute rectum situated in an angle
between two of five fleshy ridges radiating from the centre
STRUCTURE OF COMMON STAR-FISH. 181
of the aboral disk. The anus (Fig. 125, a) is minute and
difficult to detect, being situated between the short spines,,
and is evidently not used in the expulsion of fecal matter
unless the urinary secretions, if there be such, pass out of
it. Tt would seem as if the opening were rudimentary and
that the star-fish had descended from Echinoderms like the
Crinoids, in which there is a well-marked external terminal
opening of the digestive tract. Appended to the intestine
are the " cceca " or " liver " (Fig. 125, b), consisting of two
long, tree-like masses formed of dense branches of from
four to six pear-shaped follicles, connecting by a short duct
with the main stem. The two main ducts unite to form a
short common opening into the intestine. The cceca are
usually dark, livid green, and secrete a bitter digestive
fluid, representing probably the bile of the higher animals.
The star-fish is bisexual, but the reproductive glands are
much alike, the sexes only being distinguishable by a micro-
scopic examination of the glands. The ovaries (Fig. 125, 0)
are long racemose bodies lying along each side of the in-
terior of the arms, and the eggs are said to pass out by a
short narrow oviduct (or) through an opening between two
plates on each side of the base of the arms, the opening be-
ing small and difficult to detect.
The water-vascular system consists of the madreporic
body, the " stone-canal " (Fig. 125, t), the ringorcircumoral
canal (vr), and the radial vessels (v) ending in the water-
sacs (am) and ambulacra! feet. The stone-canal begins
at the outer and under side of the sieve-like madreporic
body, passing directly forward and downward in a simious
course to the under side of the circumoral plates. The
madreporic body (nib) is externally seen to be perforated by
linear apertures radiating and subdividing toward the pe-
riphery. The sea-water in part enters the body-cavity
through the fissures in the madreporic body, while most of
it enters the stone-canal, 'which is a slender tube scarcely
one fourth the diameter of the entire madreporic body.
The water entering the stone-canal (Fig. 125, t) passes di-
rectly into the water-vascular ring (Fig. 125) and then into
the ten Polian vesicles and the five radial canals, whence
182 ZOOLOG T.
it is conveyed to each water-sac or ampulla (Fig. 1 •.'.">. inn).
These pear-shaped water-sacs, when contracted, are supposed
to press the water into the long slender suckers or ambulacra!
feet, which are distended, elongated, and by a sucker-like ar-
rangement at the end of the prehensile foot act in conjunc-
tion with the others to warp or pull the star-fish along.
Besides locomotion the ambulacra! feet serve for respiration
and perception (Simroth). Hoffman shows that the feet
of the sea-urchins can be projected or thrust out without
the aid of the ampullae.
It will thus be seen that the water-vascular system in the
tf
star-fish is in its functions partly respiratory and partly
locomotive, while it is in connection with the vascular sys-
tem, and thus partly aids in circulating the blood and
chyle.
Of the true vascular or blood system the student can ordi-
narily only discover one portion, the so-called " heart " or
" pulsating vessel," which we may call the haemal canal (Fig.
125, A), and which runs parallel to the stone-canal from the
madreporic body to near the ring-canal.* It is nearly as
large as the stone-canal, slightly sinuous, muscular, and with
the latter is surrounded by a loose investing membrane like
a pericardium. Some observers deny the existence of a vas-
cular (sometimes called " pseudohaemal ") system, but it has
"been recently studied by Hoffman and subsequently by Teu-
scher, who maintains that in all Echinoderms there are two
.systems of blood-vessels, which belong, one to the viscera and
the other to the nervous system, forming an oral or nervous
ring and an anal ring. The two rings are in direct com-
munication in the star-fishes, Ophiurans and sea-urchins,
but not in the Holothurians. The radial nerves are ac-
companied by a vessel which subdivides and distributes
branches to the ambulacral feet in star-fishes, Echini, and
Holothurians. Teuscher considers that the " heart " found
in the star-fishes and Echini connecting the cesophageal (or
nerve-ring) and anal ring, is neither a gland nor a pulsating
vessel, as different authors have supposed, but perhaps only
* Simroth states that in Ophiurans (Ophiactis) the stone-canal opena
in common with the" heart" into the madreporic plate.
CRIN01DS. 183
a relict of an earlier period of development. In the Ophi-
urans the oral canal opens directly into the body-cavity ;
in EcMnotlirix directly connects with the outer world by
means of the interradial canals. Finally, he regards the
nervous vessel as homologous with the ventral vessel of the
'6
worms.
Having made ourselves acquainted with the general struc-
ture of the Echinoderms as exemplified in the star-fish, we
are prepared to study the modifications of the Echinoderm
.plan in the different classes.
CLASS I. — CRINOIDEA (Stone-lilies, Encrinites, etc.)
Order I. Bracliiata. — The living representatives of those
Crinoids which lived in palreozoic and early mesozoic
times are few in number, and for the most part live in deep
water, or, as in the case of Rliizocrinus and its living allies,
at great depths. They are like Limulus and Nebalia, rem-
nants of an ancient fauna. There are but eight genera
known — viz., Holopus, Rhizocrinus, Batliycrinus, Hi/or ri-
nus, Pentacrinus, Comaster, Actinometra, and' Ante f fun
(Comatula). Of the first five genera the species are attached
by a stalk to the sea-bottom, while the last three genera are
in their young state stalked, but finally become detached.
The body or calyx divides into arms bearing pinnulce or sub-
branches.
The Pentacrinus lives attached to rocks from twenty to
thirty fathoms below low-water mark in the West Indies.
The stem is about a foot long, the joints pentagonal, send-
ing off at intervals whorls of un branched cirri. " No dis-
tinct basal piece is known, but the calyx appears to begin
with the first five radialia ' ' (Huxley). Pentacrinus ca-
put-medum Miiller (Fig. 127) and P. Mulleri Oersted are
West Indian species. P. Wyville- Thompsons Jeffreys was
dredged in deep water on the coast of Portugal. In the
fossil P. subangularis the stalk was more than fifty feet long.
Bathyerinus gracilis Wyville-Thompson is closely allied
184 ZOOLOGY.
to Rhizocrinus, and was dredged in the Bay of Biscay at
the depth of 2435 fathoms. B. Aldrichianus occurred in
1850 fathoms, latitude 1° 47' K, longitude 24° 26' W., off
the coast of Brazil. With it and also near the Crozet
Islands occurred the interesting Hyocrinus Betliellianus
Wvville-Thompson, which bears in some points resemblance
to the palaeozoic genus, Platycrinus.
Fig. 127. -a, Pmtaerintis capuf-mednsce, half natural size; 6, calyx-disk seen from
above, natural size. — Prom Brehm's Thierleben.
The most widely distributed species is the Rhizocrinus
lofotensis of Sars (Fig. 128), which is closely related to the
Bourguetticrinus of the chalk formation, and forms the
transitional type connecting the ApiocrinidcB with the
free-moving, unstalked Antedon. It occurs at the depth of
STRUCTURE OF CRINOIDS.
185
from one hundred to
one thousand fathoms
in the North Atlantic
and Floridan seas,
and is a characteristic
member of the abyssal
fauna. This crinoid'
consists of a jointed
stalk, a cup -shaped
body (calyx), from
the edge of which
from five to seven
(the number varies)
arms (brachia) radi-
ate, which subdivide
into a double alter-
nate series of pin-
nules. The mouth is
situated in the centre,
while the anus is situ-
ated on a conical pro-
jection on one side of
the oral disk, between
the bases of two of
the arms. R. Raw-
soni Pourtales occurs
in from eighty to one
hundred and twenty
fathoms at Barba-
does.
In Holopus, a short,
stout form with no
true stalk, but at-
tached by abroad en-
crusting base, there
-are ten arms originat-
ing from five axial
joints. " When con-
-i ,1
tracted the arms are
Fig. 128. —Rhizocrtnits lofoffnsis Sars. twice natural
lzefJ- After Wyville Thompson.
136 ZOOLOGY.
rolled in a spiral and press laterally against one another so
as to enclose a hermetically closed cavity." The pinnules
are formed of broad flat joints, and are " rolled spirally to-
ward the ambulacral channel of the arms when contracted '
(Pourtales). The only species yet known is H. Ranyii
D'Orbignv, from Barbacloes.
O \i y
In Antedon (Comatula) the body is at first stalked, but
afterward drops off, when it represents the calyx and arms
of the ordinary Crinoids. It thus passes through a Rhizo-
crinus condition, showing that it is a higher, more recent
form. The mouth opens into a short, broad oesophagus,,
and a wide stomach which makes a turn and a half, ending
in the anal cone placed between the base of two of the arms.
Within the five triangular plates is a circle of tentacles.
From the space between each pair of oral plates the ambu-
lacral grooves radiate to the arms and their branches. H.
Ludwig maintains that Antedon possesses a true water- vas-
cular system formed on the typical Echinoderm plan ;
there being a ring-canal, with radial vessels arising from it.
The tentacles of the perisome are connected with the ring-
canal, and the tentacles of the arms and pinnulae are con-
nected with the radial vessel. Ludwig has also discovered
in Antedon a system of blood-vessels (''pseudo-haemal'
system) consisting of an oral ring-canal and five vessels
radiating from it, which send branches to the tentacles, as
in Asterias. He also detected a " dorsal organ, " which
he, contrary to Perrier and P. H. Carpenter, considers to
be the central organ of the whole system of blood-vessels.
Both Ludwig and Carpenter, however, regard it as homolo-
gous with the so-called " heart " or haemal canal of Echini
and Asterias.
The nervous system consists of an oral ring with branches
extending into the arms.
The body-cavity extends into the arms, and the ovaries
for the most part lie in the cavity of the arms, as in Asterias.
The internal anatomy of Rhizocrinus has been investi-
gated by Ludwig, who finds that it agrees very closely with
that of Antedon. The water-vascular system, nervous sys-
tem, alimentary canal and its appendages, have the same
DEVELOPMENT OF CRINOIDS.
187
relations as in the unstalked Crinoids (Antedon and Actin-
ometra), only they are on a simpler plan, there being a
close similarity between Rhizocrinus and the pentacrinoid
stage of Antedon.
The ovaries of Antedon open externally on the pinnules
of the arms, while there is no special opening for the prod-
nets of the male glands, and Thompson thinks that the
spermatic particles are " discharged by the thinning away
and dehiscence of the integument." The ripe eggs hang
for three or four days from the opening like a bunch of
grapes, and it is during this time that they are fertilized.
The following account is taken (sometimes word for word)
Fijsr. 129.— Development of a Crinoid (Antedon'). A, morula; B, free larva, with
bands of cilia; C, young crinoid.— After Wy ville-Tliompson. .
from Wyville-Thompson's researches on Antedon rosaceus
(Fig. 130) of the European seas. In the first stage the egg
undergoes total segmentation (Fig. 129). A represents the
egg with four nucleated cells, an early phase of the mul-
berry or morula stage. After the process of segmentation
of the yolk is finished, the cells become fused together into
a mass of indifferent protoplasm, with no trace of organiza-
tion, but with a few fat cells in the centre. This pro-
toplasmic layer becomes converted into an oval embryo,
whose surface is uniformly ciliated. The mouth is formed
with the large cilia around it before the embryo leaves the
188
ZOOLOGY.
egg. When hatched, the larva is long, oval, and girded
with four zones of cilia, with a tuft of cilia at the end. a
mouth and anal-opening, and is about eight millimetres
long. The body-cavity is formed by an inversion of the
primitive layer which seems to correspond to the ectoderm.
Within a few hours or sometimes days, there are indica-
tions of the calcareous areolated plates forming the cup of
the future crinoid. Soon others appear forming a sort of
trellis-work of plates, and gradually build up the stalk, and
lastly appears the cribriform basal plate. Fig. 6G, B, c, rep-
resents the young crinoid in the middle of the larva, whose
body is somewhat compressed under the covering-glass.
Fig. 130.—Antedon, stalked and free.— From Macnlhster.
Next appears a hollow sheath of parallel calcareous rods,
bound, as it were, in the centre by the calcareous plates.
This stalk (B, c) arises on one side of the digestive cavity
of the larva, and there is no connection between the body-
cavity of the larva and that of the embryo crinoid.
Two or three days after the appearance of the plates of
the crinoid, the larva begins to change its form. The
mouth and digestive cavity disappear, not being converted
into those of the crinoid. The larva sinks to the bottom,
there resting on a sea-weed or stone, to which it finally ad-
heres. The Pentacrinus form is embedded in the larval body
FOSSIL CRINOIDS.
189
(the cilia having disappeared), now constituting a layer of
protoplasm conforming to the outline of the Antedon.
Meanwhile the cup of the crinoid has been forming. It
then assumes the shape of an open bell ; the mouth is
formed, and live lobes arise from the edges of the calyx.
Afterward live or more, usually fifteen tentacles, grow out,
and the young Antedon appears, as in Fig. 129, C. The
walls of the stomach then separate from the body-walls.
The animal now begins to represent the primary stalked
stage of the Crinoids, that which is the permanent stage in
Rhizocrinus, Pentacrinus, and their fossil allies. After liv-
ing attached for a while (Fig. 130), it becomes free (see right-
hand figure) and moves about over the sea-bottom.
Fig. 131. -A Blastokl, Pe/Ure/nites, seen from the side arid from above.— After Liitken.
There are two species of Antedon on the New England
coast, one (A. Sarsii) inhabiting deep water in about one
hundred fathoms, and the other (A. Eschrichtii Muller)
shallower water (twenty-five fathoms) in the Gulf of Maine.
Order 2. Blastoidea, — No forms have been discovered
later than the Carboniferous period. The group began
its existence as species of Pentremites (Fig. 131) in the
Upper Silurian, and culminated in the Carboniferous age.
It connects the Crinoids with the Cystideans : the species
have no arms, are supported on a short, jointed stalk, and
the oral plates, when closed, as they are in a fossil state,
make the calyx look like a flower-bud. There is a mouth
and eccentric anal outlet and five radiating grooves, along
190
ZOOLOGY.
each side of which are attached a row of pinnules. Be-
sides Pentremites are the typical genera Elceacrinus and
Eleatherocrinus.
Order 3. Cystidecs. — This group is likewise extinct. In
the fossil Pseitdr>rri)iux there is a short-jointed stalk, while
in Caryocystites (Fig. 132) there is no stalk and no arms, the
Fig. 132. -Caryocys-
tites, a Cyetidean. —
After Liitken.
Fig. 134. — Agelacrintts, a Cystidean, on.
the shell of a Brachiopod. — After Lutkeu-
Fig. 133. —Pseudocri-
nus, a Cystidean. —
After Liitken.
body being angulo-spherical, composed of solid plates. The
Cystideans (Figs. 132 to 134) originated in the Cambrian for-
mation, attained their maximum development in a number
of species in the Silurian, and became mostly extinct in the
Carboniferous period. They are the primitive Echinoderms.
CLASS I.— CRINOIDEA.
Spherical or cup-shaped Echinoderms, without a madreporic plate,
ally attached by a jointed stem, a few free in adult life, with five arms sub-
dividing into pinnules; the ambulacral feet in the form of tentacles
arising around the mouth in, the furrows of the calyx or situated on the
jointed arms. In the Blastoidea and certain Cystideans the arms are ab-
sent, but the pi nnulce are usually present, though absent in Caryocystites.
Circulatory, water-vascular, and sexual organs much as in other Echino-
derms ; the digestive canal ending in a distinct eccentric aperture.
GENERAL STRUCTURE OF STAR-FISHES. 191
Order 1. Brncliuita (True Crinoids). — Calyx with large pinnulated
arms, without dorsal calical pores, mostly stalked (Encri-
nus, Pentacrinus, Apiocrinus, Rhizocrinus, Holopus, Ante-
dou, Actinometra, Phanogenia).
Order 2. Blastoidea. — Armless, but with five series of pinnulfe, and
with a stalk (Pentremites. No living representatives).
OrderS. Cystidea. — Usually armed, with jointed pinnuke, and a short
stalk, the latter sometimes absent, as in Caryocystites. (All
fossil forms, as Edriaster, Caryocystites, Sphaeronites, etc.)
Laboratory Work. — The living Crinoids are great rarities, and few
students have access even to alcoholic specimens. The recent re-
searches on their internal anatomy have been made in large part by
cutting thin sections for the microscope, and staining them with car-
mine, etc., after the methods of the histologist.
CLASS II. — ASTEROIDEA (Star-fishes).
General Characters of Star-fishes. — Having already
studied the structure of the common star-fish, we are pre-
pared to understand the classification of the class. The
star-fishes have star-shaped, flattened bodies, with round or
flattened arms, a madreporic plate, and two or four rows of
ambulacra! feet.
Order 1. Ophiuridea (Sand-Stars). — This division is
characterized by the body forming a flattened disk, with
cylindrical arms, the stomach not extending into the arms,
and there is no intestine or anal opening. The ambulacral
furrow is covered by the ventral shields of the tegument, so
that the ambulacral feet project from the sides of the arm.
They have no interambulacral spaces or plates. The am-
bulacral feet or tentacles do not have a sucker at the end,
but are provided with minute tubercles. They move faster
than the true star-fishes, the arms being more slender and
flexible. The madreporic body is one of the large circular
plates in the interambulacral spaces around the mouth.
The external openings for the exit of the eggs form distinct
fissures or slits, one on each side of each arm. The ovaries
are situated in the body, not extending into the arms, the
102 ZOOLOGY,
eggs being expelled into the perivisceral cavity, and thence
finding their way out into the water through the interradial
slits.* The Ophiurans are bisexual, but one species being
known to be unisexual, viz., Oplnolepis squamata, accord-
ing to Metschnikoff. While most Ophiurans pass through
a metamorphosis, the young of Ophiolepis ciliata is developed
within the body of the parent, adhering by a sort of stalk
(Krohn). In Ophiopliolis bellis development is direct, there
being no metamorphosis.
An Ophiuran which has accidentally lost its arms can re-
produce them by budding. Liitken has discovered that in
species of Ophiothela and OpMactis the body divides in two
spontaneously, having three arms on one side and three on
the other, while the disk looks as if it had been cut in two
by a knife and three new arms had then grown out from
the cut side. Simroth has made farther extended researches
on self-fission in Ophiactis.
The Ophiurans in most cases undergo a decided meta-
morphosis like that of the star-fish, which will be described
at length farther on. The larva, called a pluteus, is free-
swimming, though in some species the young, in a modified
larval condition, reside in a pouch situated above the mouth
of the parent, finally escaping and swimming freely about
(A. Agassiz).
In Ophiocoma vivipara Ljungman, which occurs in the
South Atlantic, the young at first live in the body of the
parent and afterward cluster on the surface of her disk.
The eggs are hatched successively, the young being found
in a regularly gradated series of stages of growth (Wyville-
Thompson). It appears probable, as in the case of the sea-
urchins, that the Ophiurans of the cooler portions of the
South Atlantic, in most cases at least, have no metamor-
phosis. Several native forms are also viviparous.
Our most common sand-star is Opliioplwlis bellis Lyman
(Fig. 135), which may be found at low-water mark, and espe-
cially among the roots of Laminaria thrown up on the
* On the other hand, Ludwig denies that the eggs pass into the peri-
visceral cavity, but insists that they collect ill pouches formed by an in.
troversion of the integument.
SAND-STARS AND STAR-FISHES.
193
beach. It is variable in color, but beautifully spotted with
pale and brown, its general hue being a brick-red. Am-
pMura squamata Sars has long slender arms and is
white ; it lives below tide-marks. The basket-fish, me-
dusa's head, or Astrophyton
Agassizii Stni., is of large
size, the disk being two in-
ches across, and the arms
subdividing into a great
number of tendril-like
branches. It lives from ten
to one hundred fathoms in
the Gulf of Maine.
Ophiurans are widely dis-
tributed, and live at depths
between low- water mark and
two thousand fathoms. Fos-
sil Ophiurans do not occur
in formations older than the Upper Silurian, where they are
represented by the genera Protaster, Palceodiscus, Acroura,
and Eucladia ; genuine forms closely like those now living
appear in the mnschelkalk beds of Europe (Middle Trias).
Order 2. Asteridea. — In the true star-fishes the arms are
direct prolongations of the disk, and the stomach and
~F\^.\?^.— OphwpholisbeUls, common Sand-
star.— After Morse.
Fig. 136. -Three forms of Star-fish, A, B, C, «*n from above, bhowma the different
development of the ambulacra! and iulerambulacra] areas. The ambulacra are iudi
;ated by rows of dots ; o, mouth; r, arms; ii\ iuterradial or intemmbuiacral aivu.-
V Pterasttr; B, Goniodiscus; A, Ast&iscus.—Attei Gegenbaur.
ovaries or spermaries pi-oject into them, and there is a deep
ambulacral furrow, while the interambulacral spaces vary
much in development (Fig. 136); the feet are provided with
194
ZOOLOGY.
suckers, excepting those at the end of the arms, which are
tentacle-like. We have already described the common star-
fish of our north-eastern coast, Asterias Forbesii of Desor
(Fig. 137). This and the allied varieties are abundant on
mussel and oyster beds, being very injurious to the latter,
which serve them as food. The star-fish projects its capa-
cious stomach, turning it inside out. between the open
valves of the oyster, meanwhile pouring out a poisonous fluid
from the unicellular glands of the midgut so as to surround
the oyster with a sticky envelope, before the animal is drawn
out of its shell.
Fig. 137.— A star-fish, which has been placed ou its back, righting itself.— After
Romanes.
The bodies of star-fishes as well as sea-urchins (Echini)
are covered with pedicellarice, which in the former are situ-
ated around the base of the spines on the upper side of the
body. They are pincer-like, consisting of but two prongs.
Ju the sea-urchins they are three-pronged, and scattered ir-
regularly over the surface of the body. Their use is net
really known. Star-fish have the sense of smell.*
The development of this species (and its ally or variety,
A. benjlinus) has been studied by A. Agassiz. After pass-
* It is localized iu the suckers at the back of the eye-plate (Prulmi.
DEVELOPMENT OF STAR-FISHES.
Ing through the morula and gastrula stages, the cephalula
or larval stage is reached, the mouth, digestive sac and its
posterior opening being formed, a cephalic end being dis-
tinguished from a posterior end. Tho larva is no\v bilater-
ally symmetrical. At this time two lobes arise from each
side of the mouth. These separate from their attachment
and form two distinct hollow cavities, and by the time the
larva attains the Brachiolaria stage the development of the
Fig.l38.—Bipinnaria with the star-
fish budding from it. e. e', d', g, g\
protuberances of the body comparable
with the "arms" of the" Brachiolaria
figured in the adjoining engraving.
6, mouth; 0, vent of the larva; A, germ
of the star-fish; h, ciliated digestive
tract; i, ambulacra! rosette (germ of
the water-vessels).— After M tiller, from
Gegenbaur.
Fig. 139. — Brarhinlaria
of Axtcri/in n/tgat'is, en-
larged, with the star-fish
(/•) developing at the
aboral end. e. median
anal arm; ef, odd termi-
nal oral arm; f, brachio-
lar arm; /'. branch of
water-tube (ivm') leading
into /" odd brachiolar
arm; /'", surface-warts
at base of odd brachiolar
arm/".— After A. Agas-
siz.
body of the star-fish begins, for these two cavities subse-
quently develop into two water-tubes. On one of these cav-
ities the back of the star-fish is afterward developed, while
on the other the under side with the feet or tentacles arise.
The fully-grown larva is called a brachiolar ia, as it was
originally described with this name under the impression
that it was an adult animal, as was the case with the pin-
196 ZOOLOGY.
tens of the sand-stars, the bipinnaria (Fig. 138) of certain
star-fishes, and the auricularia of the Holothurians.
Fig. 139 shows the star-fish developing on the aboral end
of the brachiolaria, whose body it is now beginning to ab-
sorb. The brachiolaria soon shrinks, falls to the bottom,
and attaches itself by its short arras. The star-fish com-
pletely absorbs the soft body of the larva, and is conical,
disk-shaped, with a crenulated edge. In this stage it re-
mains probably two or three years before the arms lengthen
and the adult form is assumed.
In Lepty chaster Icerguelenensis Smith, of the South Paci-
fic, a form allied to Luidia or A r chaster, the young develop
directly in a sort of marsupium, according to "Wyville-
Thompson. Pteraster militaris was found by Sars to be
viviparous.
In Brisinga the arms number from nine to twenty, are
long, cylindrical, and, like the body, bear long spines. The
species are abyssal. B, endecacnemos Asbjornsen lives on
the Norwegian coast, at a depth of about 200 fathoms, and
was dredged in abundance by the Challenger Expedition in
1350 fathoms, at a station due south of St. George's Banks,
associated with other species of star-fish (Zoroaster and As-
tropecten), and again in eighty fathoms on La Have Bank,
off Nova Scotia. A common form living in mud in usually
from ten to thirty fathoms is Ctenodiscus crispatus Eetzius,
in which the body is almost pentagonal, the arms being very
short and broad. Arcliaster is a genus of star-fishes occurring
at great depths, A. vexillifer Wyville-Thompson (Fig. 140),
occurring off the Shetland Islands, in from 300 to 500 fath-
oms. Luidia is called the brittle star-fish, as when brought
up from the bottom and taken out of the water it breaks up
into fragments. It has five long arms. L. clathrata is com-
mon on the sandy shores of the Carolinas, and ranges from
New Jersey to the West Indies. Astropeden art tr Hiatus
(Say) has the same range. Astrogonium plirygianum Parel
is a large pentagonal, bright-red star-fish, living in twenty
to fifty fathoms on rocky bottoms in the Gulf of Maine
and northward ; while Pteraster militaris Miiller is an
arctic species which ranges south to Cape Cod. It is sub-
DIFFERENT FORMS OF STAR-FISHES. 19?
pentagonal, with five short arms. The fine large Solaster
endeca Retains has eleven smooth arms ; it lives in deep
water. Crossaster papposus (Miiller and Troschel) is com-
mon on a rocky bottom, in from twenty to eighty fathoms,
from the Gulf of Maine northward ; it is bright red, and has
thirteen to fourteen spinulated arms. Cribella sanguln-
olenta Liitkeii is a common species on the coast of New
Fig. 140. — Archaster vexUlift.r, under side ; natural size. — After Wyville-Thompson.
England below low- water mark, and is in some respects like
Crossaster.
More closely allied to Asterias is the Pacific Coast Pycno-
podia lielianthoides Stimpson, which ranges from Sitka to
Mendocino, Cal. It is very common in Puget Sound, under
wharves. Asterias vulgaris Stimpson represents, on the
northeastern coast, the A. rubens of Europe. Asterias
volaris (M. and T.) has six arms, and is over twelve inches.
198 ZOOLOGY.
in diameter ; it is very common from Labrador north-
ward.
Fossil star-fishes allied in most respects to Aster ias occur
in the Lower Silurian rocks, showing the remarkable persist.
ence of this type of the order. Characteristic Lower Silu-
rian forms are Palceaster and Archasterias. In the Upper
Silurian appeared Palasterina, a genus allied to the living
Astrogonium, etc.
CLASS II.— ASTEROIDEA.
Echinoderms with a star -like or pentagonal body, with two or jour row*
of ambulacral feet or tentacles on tJie oral side. Body covered with smalt,
short spines, often arranged in groups. The nervous system pentagonal,
with nerves extending into the arms ; the water-vascular and hcemal systems
also radiating info the arms. Most of the species bisexual; the young usually
passing thromjh a nu '/nnorphosis, the star-fish budding out from the water-
vascular system of the pluteus, bipinnaria or brachiolaria form, which pre-
viously passes through a morula, gastrula, and cephalula stage.
Order 1. Ophiuridea. — Arms round, starting suddenly from a round,
disk-like body. Ambulacral furrow covered by a series of
ventral plates, so that the tentacles or ambulacral feet are
thrust out laterally. The ovaries and stomach not extend-
ing into the arms ; no anal-opening, no pedicellariae.
(Ophiura, Ophioglypha, Ophiolepis, Amphiura, Ophio-
coma, Astrophytou).
Order 2. Asteridea. — Body star-like, the arms being gradual extension?
of the disk, and containing the reproductive glands, di-
gestive coeca, as well as the radial nerves and radial hremal
and water-vascular canals. A deep ambulacral furrow;
containing two or four rows of ambulacral feet or tenta-
cles, those at the extremity of the arms without suckers
(Brisinga, Ctenodiscus, Luidia, Astropecten, Oreaster, As
trogonium, Pteraster, Solaster, Crossaster, Cribrella, Pyc-
nopodia, Asterias).
Laboratory Work. — The larger star-fishes are easily dissected ; the
general relations of the integument may be perceived by making
transverse and longitudinal sections, while the viscera may be studied
by splitting the body and arms in two vertically. The smaller Ophiu-
rans can be hardened in alcohol, and stained sections made for
studying the intricate relations of the water-vascular, haemal, and
nervous systems.
HABITS OF SEA URCHINS.
199
CLASS III.— ECHINOIDEA (Sea-urchins}.
General Characters of Sea-Urchins. — A good idea of
the general structure of the members of this class may
be obtained by an examination of the common sea-ur-
chin, Echinus (Fig. 141), of the eastern coast of the United
Fig:. 141. —The common Sea-urchin, Echinus (Strongylocentrotus) ilrobachiemis.
d, frame-work of month and teeth seen in front; c. the same seen sideways; a, b, sido
and external view of a single tooth (pyramid); all natural size.— After Morse.
States, Northern Europe, and the Arctic Seas. It is com-
mon among rocks, ranging from low-water mark to fifty or
more fathoms. It eats sea-weeds, and is also a scavenger,
feeding on dead fish, etc. We have observed great num-
bers of them assembled in large groups, feeding on fish offal,
a few fathoms below the sur-
face, in a harbor on the coast
of Labrador, where fishing-
vessels were anchored.
On placing an Echinus in
sea- water the movements of
the animal, especially its
mode of drawing itself along
by its numerous long tenta-
cles or ambulacral feet, and
how it covers itself by draw-
ing together bits of sea-
weed and gravel, may be
observed.
A habit less easily detected is that of some sea-urchins
burrowing in limestone rocks and coral reefs until the ani-
mal sinks quite far down. How the rock becomes thus
worn away, unless simply by the rotary movements of the
body, is not clearly understood.
Fig. 142. — Tooth-apparatus of the Sea-
urchin, showing the complicated arrange-
ment of the muscles.— From Macallister.
200
ZOOLOG Y.
In order to examine the external anatomy, the shell
should be deprived of its spines in part, meanwhile observ-
ing the mode of attachment of the spines, of which micro-
scopic sections
should be made.
The solid mouth-
parts, the oral
membrane sur-
rounding the five
sharp conical teeth
or "pyramids,"
and their mode of
attachment to the
" auricles " in the
Fig. 143. —Schematic figures of a Sea-urchin. A, from
the oral end ; B, from one side. Ambulacra indicated
by rows of dots, r, ambulacral; ir, interarubulacral
areas; o, mouth; a, veut. — After Gegenbaur.
shell, should be thoroughly investigated, as well as their re-
lations to the mouth-opening and the digestive canal. The
shell consists of five double rows of ambulacral plates,
perforated for the exit of the
feet, and a series of five dou-
ble rows of interambulacral
plates to which the spines
are attached, and of such
form and arrangement as to
give the greatest possible
strength and lightness to the
shell (Figs. 143-144). The
outlet of the alimentary canal
is situated on the aboral
(abactinal) or upper end of
the shell, while the madre-
poric plate is situated upon
Fig.144.— Aboral end of the ehell of an
Echinus, with the upper end of the rows of
plates, a, ambulacra! area; i, interambu-
the top Or end of the Shell forming a maurepoiicplate; x, anal opening
. in the aboral area surrounded by the genit nl
(as the animal moves mouth plates. The tubercles to which the spines
, . . , . ~ are attached are only drawn on one ambula-
. , . ~ -
being a modlhca- cral and one interambiUacral area ; ou the
, . /> £ j_i "i i former are also drawn the pores through
tlOn OI One OI the genital which the suckers protrude. -After Gegeu-
plates(Fig.l44,w). There are baur'
five large plates, one at each end of the interambulacral
zones meeting on the aboral end of the body ; in them are
the ovarian openings through which the eggs escape ; these-
Fig. 141a. — Echinus on its back.
lllllllllllMHIHMIII
Fig. 1416.— Echinus extending its sucker on beginning to right itself.
Fig. 141c. — Echinus half way over.— After Romanes.
[To face page 200.]
ANATOMY OF SEA-URCHINS.
201
five plates are called the genital plates, while in each of the
five smaller plates at the end of each ambulacral series is an
eye-speck. The pedicel-
larise are three-pronged,
knob-like spines, scat-
tered over the body, es-
pecially near the mouth.
They partly serve to re-
move the faecal matter,
but their main function
is that of touch.
Besides the pedicel-
laria?, Loven has discov-
ered on most living
Echini, with the excep-
tion of Cidaris, small
button-like bodies called
spftceridia, situated on a
short stalk, moving on a
slightly marked tubercle.
They are supposed to be
Fig. 145. — View of the calcareous net-work
from a plate of the integument of a Sea-urchin
(Cidaris). b, section perpendicular to i he hori-
zontal net-work of straight rods,.— After Gegeii-
baur.
t/
sensorial, probably organs of taste and smell.
The internal anatomy of the sea-urchin may be best studied
Fig. 146 —Shell of a Sea-nrchin (Stronqylocentrohiit Hindus), a, anus; oe. oesophagus;-
t, intestine; *, one of the rods of the Loath-apparatus; in, muscles of the jaws; p, ves-
sels of the sucking feet; ])o, extremity of the water- vessel; ca, ocular plate; r, ovary.
by cutting the shell into two halves, oral and aboral. Remov-
ing the aboral end, the digestive canal may be seen in place.
* In the interambulacral spaces are blue spots, viz., compound eyes.
202 ZOOLOGY.
It consists of a narrow oesophagus (Fig. 1-tG, ce], more or
less pentagonal near the mouth, dilating into the stomach ;
-and of a terminal intestine. The long stomach passes from
left to right around the interior of the body, then turns up
toward the aboral end, and curves back in the opposite
course, again passing around the body from right to left,
forming two series of loops partly enclosing the ovaries ; it
is held in place by a broad, thin membrane or " mesentery."
The reproductive and other organs are much as described
in the star-fish, there being five ovaries or spermaries, the
sexes being distinct. The nervous ring around the mouth
sends off five nerves along the ambulacra, which are accom-
panied by a water-vascular canal sending branches to the
tentacles, and a pseudo-haemal canal, there being an oral and
aboral (anal) hffimal ring (their presence is denied by Hoff-
mann), as well as an oral water-vascular ring, with five Polian
vesicles (present only in the true Echini and Clypeastroids),
a stone-canal and a fusiform tube or " heart "* next to it,
while the alimentary canal is accompanied by two haemal
vessels, one on the " dorsal " and the other on the free or
ventral side, communicating with a lacunar network in its
walls.
In Echinus it is difficult to perceive any bilateral sym-
metry, the parts radiating, as in the star-fish, from the cen-
tre ; but in the Spatangus and allied forms it is easy ^o di-
vide the animal into a right and left side, and the body is
more or less elongated, as in Pourtalesia (Fig. ir>o), the mouth
being situated at one end and the anus at the other.
The mode of development of the common sea-urchin
(Fig. 141) has been discovered by Mr. A. Agassiz. The earli-
est stages are much as described in the star-fish. The form
of the pluteus larva is quite remarkable, there being eight
very long slender arms supported by slender calcareous rods
projecting from the body, and. during the movements of
the animal, opening and shutting like the rods of an um-
brella. The body is provided with a sinuous row of vibra-
* It should be observed that the latest and best observers are at vari-
ance regarding the structure and function of the so-called Echinoderm.
heart."
DEVELOPMENT OF THE 8EA-URGUIN. 203
tile cilia. When the larva is twenty-three days old the ru-
diments of the five tentacles of the sea-urchin appear. By
this time the pluteus-form is acquired, and also at this pe-
riod the sea-urchin growing upon the deciduous pluteus
scaffolding has concealed the shape of the digestive cavity
of the larva, and the spines are so large as to conceal the
tentacles. The body of the pluteus is gradually absorbed
by the growing sea-urchin ; the spines and suckers of the
latter increasing in size and number with age, until by the
time the larval body has disappeared the young Echinus is
more like the adult than the star-fish at the same period in
Fig. 147.— Hemiaster Philtppii, with the young in two of the marsupia. — From
Wyville-Thompson'e Voyage of the Challenger.
life. Grube has found that Anochanus sinensis, supposed
to have come from the Chinese or East Indian seas, has
no metamorphosis ; while Hemiaster cctvernosus of Chili
was found by Philippi to carry its young in marsupia and to
develop directly.
Several species of sea-urchins in the cooler portions of
the South Atlantic, especially at the Falkland Islands and
Kerguelen Island, also develop directly in marsupia or brood-
hollows, without passing through a metamorphosis. In Hemi-
204
ZOOLOGY.
aster PJnlippii Gray (Figs. 147, 148), from the latter island,
certain of the ambulacra! plates are greatly expanded and
depressed " so as to form four deep, thin-walled oral cups,
sinking into and encroaching upon the cavity of the test,
and forming very efficient protective marsupia. " The
spines are so arranged that a kind of covered passage leads
from the ovarial opening into the marsupium, and along
this passage the eggs, which are very large (a millimetre in
diameter) are passed and arranged in rows, each egg being
kept in place by two or three spines bending over it. Here
the eggs develop, and the embryos, after the calcareous
Fig. 148. -Marsupium of Hemiaster Philippii, con raining eggs. Much magnified. -
From Wyville-Thompsou's Voyage of the Challenger.
plates once begin to develop, rapidly assume the parent form ;.
Avhen they leave the marsupium they are about two and a
half millimetres long. In Cidaris nutrix Wyville-Thompson
the eggs are protected in a sort of tent by certain spines
near the mouth. Here the young develop without a meta-
morphosis. The allies of these forms in the Northern At-
lantic are either known or supposed to be metabolous ; and
Sir Wyville-Thompson states that no free-swimming Echi-
noderm larvae (plutens, etc.) were seen by the Challenger
Expedition in the Southern Ocean.
PRINCIPAL FORMS OF SEA-URCHINS.
Taking a rapid survey of the principal forms of sea-
nrchins, we may divide the class of Echinoidea into two or-
ders : the Palechinida, or older sea-urchins, in which the
shell is composed of more than twenty rows of plates ; and
the Autechinida with twenty rows of plates.*
Order 1. Palechinida. — Comprises first the suborder Me-
lonitida, in which there are more than ten rows of ambula-
cra! plates, represented by Melonites of the coal formation,
and Protechinus, Pakechinus, Archceocidaris, etc. In the
second suborder Eucidaria, there are ten rows of ambulacral
plates. A type of the group, Eocidaris Kaiserlingii, appears
in the Permian formation.
Order 2. Autechinida. —
To this division belong sea-
urchins with twenty rows of
plates. The first suborder is
the Dcsmosticlia, comprising
those sea-urchins with band-
like ambulacra extending
from the mouth to the oppo-
site extremity, and of more
or less regular, flattened,
spherical form. Such are
Cidaris, Echinus, Echinom- Y{K U9 __Echlnarachnius parma^ com.
etra Clliveaster, and Edli- monSaud-cake. Natural size. -After A.
«•* . Agassiz.
nareihnius. The Echinus
esculentus Linn., of the Mediterranean Sea, is as large as
an infant's head, and is used as an article of food.
In Cli/peaster the body is large and the shell very solid.
C. suldepressus Agassiz is common on the Floridan coast.
An orbicular flattened type are the sand-cakes, of which the
Ecliinaraclmius parma Gray (Fig. 149) is abundant in the
shallower portions of the North Atlantic, from low-water
mark to forty fathoms. It is replaced southward from
Nantucket to Brazil by Mellita testudinata Klein.
The last suborder, Petalosticha, is characterized by the
* These are terms proposed by Haeckel, who regards these divisions
as subclasses, but we think they should more properly be called orders.
206
ZOOLOGY.
leaf -like ambulacra, and the irregularly heart-shaped, often
elongated, form of the shell, an anterior and posterior end
being well defined. They for the most part live buried in
the sand or sandy mud, not moving about so actively as the
Desmosticha.
Of the family Spatangidm the singular genus Pourta-
lesia (Fig. 150, P. Jeffreysii Wyville-Thompson) deserves
notice, the species of which are bottled-shaped, with a thin,
transparent shell. The transition from such a form as this
to the Holothurians is not a very extreme one. This
genus, A. Agassiz states, is the living representative of In-
fulaster of the Cretaceous period. P. miranda A. Agassiz
was dredged in the Florida btraits, in about three hundred
Fig. 150.— Pourtalesia Jeffreysii, slightly enlarged. — After Wyville-Thompson.
and fifty fathoms, and by British naturalists in the -Shet-
land Channel. P. Jeffreysii was dredged in six hundred
and forty fathoms, near the Shetland Islands.
Spatangns is distinctly heart-shaped, as is Hemiaster.
An interesting deep-sea or abyssal form not uncommon in
deep soft mud, at the depth of one hundred fathoms, off the
coast of Maine and Massachusetts, and extending from Flor-
ida around to Norway, is Scliizaster frngilis Agassiz.
Echinoderms range to a great depth in the ocean, and are
largely characteristic of the abyssal fauna of the globe. In
space they are widely distributed, there being but two
Echinid faunse on the eastern coast of the United States,
one arctic, the other tropical. While a large number of
species characterize the arctic or circumpolar regions, the
FOSSIL ECHINODERMS. 207
larger proportion of species are tropical and subtropical.
Mr. A. Agassiz divides the Echinid fauna of the world into
four realms : the American, Atlantic, Indo-Pacific, and
Australian.
Though Crinoids were the predominant type of Echino-
derms in the palaeozoic rocks, a few star-fish and Ophiurans
appeared in the Upper Silurian period, and with them were
associated one species of sea-urchin, Palcechinus, though
the genus was more numerously represented in the Coal
period. Some Palaeozoic forms resembled the living gen-
era Calveria and Phormpsoma, and belong to the extinct
Carboniferous genera Lepidechinus and Lepidesthes ; in all
these forms, fossil and recent, the interambulacral plates
overlapped one another so as to give a certain amount of
flexibility to the shell. This feature existed in a less de-
gree in Arcliceocidaris. The characteristic American car-
boniferous genera are Melonites, Oligoporus, and Lepidechi-
nus. The Permian Eocidaris is nearly allied to Arcliceoci-
daris, so that it is a true palaeozoic type (Nicholson).
In the Mesozoic epoch (Trias, Lias, and Jura) appeared a
more modern assemblage of Spatangidce, and genera such as
Hemicidaris and Hypodiadema, closely allied to the Cida-
ridce proper, appeared in the Trias. The Jurassic beds are
characterized by genera allied to Diadema, Echinus, Ci-
daris, and a number of species of the families Cassidulidto
and QaleritidcB. A large number of genera survived in the
Cretaceous period, which, however, is characterized by the
marked development of the Spatangidce. In the Upper
Cretaceous the earliest Clypeastridce appeared, while the
Tertiary Echinid fauna is quite similar to the present one.
The striking fact in the geological history of the class is
the persistence of many of the cretaceous genera in the
abyssal or deep-sea fauna of the present time (A, Agassiz).
208 ZOO LOOT.
CLASS III.— ECHINOIDEA.
Spherical, heart-shaped, or disk-like Echinoderms, with a solid shell of im-
movable plates, bearing interambulucral spines; with a. mouth and anal
opening, the mouth in most of the species armed with five, teeth ; am-
bulacralfeet well developed. The sexes distinct. Development either direct,
or, as in most cases, by a marked metamorphosis from a pluteus larva.
Order 1. PalecJiinida.— Shell composed of more than twenty rows of
plates. Suborder 1. Melomtida (Melonites, Protechinus,
Paleechinus, Arcliaeocidaris). Suborder 2. Eoddaria (Eoci-
daris).
Order 2. Autechinida.— Shell composed of twenty rows of plates.
Suborder 1. Desmosticl.a (Cidaris, Echinus, Strongylocen-
trotus, Echinometra, Clypeaster, and Echinarachnius).
Suborder 2. Petalostichu (Echinobrissus, Auochanus, Pour-
talesia, Spatangus, and Schizaster).
Laboratory Work. — We have already given some hints as to the
mode of dissecting sea-urchins, which should be done under water in
deep pans. Great care must be taken in removing the digestive canal,
which is very delicate in itself, and usually filled with sand. In study-
ing the water- vascular and blood-vessels, careful, skilful injections with
carmine are indispensable. The spines may be studied by making thin
longitudinal and transverse sections The test, or shell, should be de-
nuded of the spines in order to study the relations of the ambulacral,
interambulacral, and genital plates.
CLASS IV. — HOLOTHUROIDEA (Sea-cucumbers).
General Characters of Holothurians.— We now come to
Echinoderms in which the body is usually long, cylin-
drical, with a tendency to become worm-like, and in cer-
tain genera, as Synapta, Chirodota, and Eiipyrgus, it is
difficult both in their larval stages (Synapta} and in the
external and internal anatomy of the adults to separate
them from worms like Sipunculus ; authors have therefore
been led to the adoption of one of two views : first, cither
that the worms and Echinoderms have had a common origin,
and the latter, though truly radiate, have no near affinities
(though strong analogies) with the Crelenterates, or the re-
HABITS OF HOLOTHURIAN8.
209
semblance between the two branches (Echinoderms and
worms) is one simply of analogy, and involves no blood-rela-
tionship. On the other hand the radiated arrangement of
parts and the development and relations of the water-vas-
cular system ally them, through the Ctenophores, with the
Actinozoa and Hydroida, but it seems more natural to re-
gard the Echinoderms as forming a branch of animals stand-
ing near such worms, possibly the Nemerteans, as have a body-
cavity, as well as a complicated excretory (nephridial) system.
But the student will be better
able to appreciate these general
questions after a more or less
thorough acquaintance with the
forms and structure of the pres-
ent group. For this purpose he
should first examine living sea-
cucumbers, and then carefully
dissect them. A detailed study
of the anatomy of a Pentacta or a
Holothuria, one a northern the
other a subtropical and tropical
form, and of a Synapta, found
everywhere along our coast in sand
below tide-m&rks, will give the
groundwork ; and this knowledge,
autoptically acquired, can then be
corrected and extended by reading
monographs or compiled state-
ments to be found in the more
authoritative general works on
comparative anatomy. Fig.i5i.-p«»terfa
Living Holothurians can be pro-
cured with the dredge or dug out of the sand between tide-
marks. They should be kept in aquaria, and their move-
ments watched as well as their mode of locomotion, and the
action of their branchiae or external gills (tentacles).
The common sea-cucumber, north of Cape Cod, and ex-
tending through the Arctic regions around to Great Britain,
is Pentacta frondosa Jaeger (Fig. 151). It lives from ex-
210 ZOOLOGY.
treme low-water mark to a depth of fifty fathoms. It is of
a tan-brown color, from six inches to nearly a foot in
length, and in its form and the corrugations of its tough,
leathery skin resembles a cucumber in nearly all respects-
except color. There are five series of ambulacral feet, each
series consisting of two irregular rows. Around the mouth
is a circle of ten much-branched tentacles or gills (homolo-
gous with the ambulacral feet).
On laying the body open by making a cut extending from
the mouth to the vent, the thick muscular walls of the body
may be observed, and the general relations of the viscera to-
the body-walls, which have nothing of the radiate arrange-
ment of parts, so clearly marked in the other Echinoderms,
the ambulacra, tentacles, and longitudinal muscles alone be-
ing arranged in a radiate manner.* Unlike other Echino-
derms, the madreporic body is internal, and there is a ca~
pacious cloaca or rectum, and a large vent.
On the inside of the body-walls are numerous small cir-
cular (transverse) muscles forming slight ridges, which serve
to contract the body, and five double large longitudinal
muscles (Fig. 152, /) lying in the ambulacral zones. The
mouth is surrounded by a muscular ring, from which arise-
ten large, much-branched tentacles. The pharynx, or the
portion corresponding to " Aristotle's lantern," of the sea-
urchin is broad and short, with five large retractor muscles.
(r) originating from the ambulacral or longitudinal muscles
on the anterior third of the body. The stomach is short,
not much wider than the intestines, with well-marked trans-
verse folds within. The intestine (i) is several times longer
than the body, with longitudinal small folds, and held in
place by a large, broad mesentery which accompanies the in-
testine through the greater part of its length. The intes-
tine terminates suddenly, in a large cloaca (c), from which
* In Eupyrgus and Echinocucumis it is difficult to perceive any radio-
tion in the body except in the unbroken circle of tentacles, while in
Bipunculus and allied worms (Qephyrea) the tentacles form a complete
circle, and these worms have a ring-canal and an imperfect or rudi-
mentary system of vessels thought by some authors to correspond to
the water- vascular system of Echinoderms.
ANATOMY OF HOLOTHURIANS.
211
on one side arises the " respiratory tree," which has but one
main stem, and is only occasionally held in place by mus-
cular threads. The branches are numerous, and are smaller
Y\gA52.—Pen(acta frondosa. t, tentacles; I, longitudinal muscles; r, retractor mus-
cles of the tentacular system; i. intestine; c. cloaca-, 6, respiratory tree; vr, water-
vascular ring or nng-canal, v, radial water-vascular canal; TO. madreporic body; pp,
polian vesicles; am, ampullae: a, a', pseudo-haemal contractile vessels (from Cams);
0, ovary; ov, mduct.— Drawn by J. S. Kiugsley from a dissection made by the author.
and paler than the ovarian tubes. The water enters the
cloaca (c), passes into the respiratory tree (b), oozes out of
212 ZOOLOGY.
the ends of the branches, filling the body, whence it is taken
up by the niadreporic body and carried into the water-
vascular system by the narrow duct on the left side of the
pharynx. Besides being respiratory, this organ is supposed
to be depuratory in its function. In some Holothurians
certain organs (the Cuvierian organs), supposed by Semper
to be organs of defence, as they are readily thrown out when
the animal is disturbed, are attached either to the stem of
the respiratory tree or to the cloaca. The niadreporic body
(m) forms a rosette, partly surrounding the membrane at-
tached to one side of the pyloric end of the stomach, and
leads by the niadreporic canal, which is closely bound down
to the pharynx, to the ring-canal (vr). Also connected
with the ring-canal are two enormous Pol i an vesicles (p, p),
which are nearly two thirds as long as the body ; by slitting
up their base with scissors they can be followed to the ring-
canal. The latter (vr) is a capacious canal surrounding the
mouth, and can be detected by laying open the oral-opening,
.and then by cutting across the longitudinal muscles (as atr)
the radial vessels may be followed along the body under the
muscles. Just above the ring-canal is situated the nervous
ring (nr), and its radial nerves (n) can be traced along and
outside of the radial water-vascular canals. The ampulla?
•(am) are red, conical, flask-shaped, conspicuous organs, lying
irregularly, a row on each side of each longitudinal muscle.
They are filled with Avater from the small lateral vessels of
the radial water-vascular canals. The single ovary is com-
posed of a large mass of long tubes, which are larger than
and tangled up with the branches of the respiratory tree.
The oviduct is attached by a membrane to the stomach, and
opens between two of the tentacles on the edge of the
mouth.
The blood or pseudo-haemal vessels * are difficult, without
very fine dissections, to be made out. The system consists
of a plexus of vessels lying next to the ring-canal, from
which two vessels (a, a') pass along opposite sides of the in-
* These vessels iu Fig. 152 have been copied from Cams' Icones Zo-
otomicse ; in other respects the drawing represents the anatomy of
P, frondosa.
ANATOMY OF HOLOTHURIANS.
testine. A fluid containing nucleated cells fills both the
pseudo-haemal and water- vascular canals.
Holothuria floridana Pourtales is a large, dark-brown
sea-cucumber, with the feet scattered irregularly over the
body, and with smaller tentacles than iu Pentacta, which is
abundant just below low-water mark on the Florida reefs,
and grows to about fifteen inches in length. The aliment-
ary canal is filled with foraminifera and pieces of shells,
corals, etc. ; it is about three times the length of the body,
and ends in a much larger ccecum than that of Pentacta.
There are two widely separated branches of the " respira-
tory tree," one being free, and the other, tied to the body-
walls by thread-like muscular attachments, extends to the
pharynx. The pharynx is calcareoiis, while in Pentacta it
is muscular. On the madreporic body is a group of about
thirty pyriform stalked bodies, the longest, including the
stalk, about a quarter of an inch in length. Succeeding
these bodies, and situated on the madreporic canal, leading
to the ring-canal, are a large number of Polian vesicles, the
largest one an inch in length. The duct passes spirally
nearly round the oesophagus, and empties into the ring-
canal by the ducts nearly a quarter of an inch apart. In
connection with the tentacles or branchiae are twenty long,
slender tentacular ampullae, not present in Pentacta and
Tliyone. Tbe ovarian tubes are very small, some enlarging
and bilobate at the end.
Closely allied in external form to Holothuria floridana,
though belonging to a different family (including Pentacta1*,
is Thyone briareus (Lesueur), which lives just below tidal
marks, from Long Island Sound to Florida. In this genus
the ambulacral feet are not arranged in rows, but scattered
over the surface of the body. This species is very common,
and as it is more accessible to the student than any other of
the sea-cucumbers, we give some points in its anatomy as
compared with Pentacta, with which it is more closely allied
than to Holothuria. In a specimen about eight centi-
metres (three inches) long the intestine is over two metres
(about seven feet) long, the oesophagus opening into an
oval stomach less than an inch in length. The tentacles
214 ZOOLOGY.
are capable of being very deeply retracted, and as in
Pentacta there are no tentacular ampullae. The small
madreporic body is much as in Pentacta, and connects with
a duct (madreporic canal) leading to the ring-canal. There
are three Polian vesicles, one fusiform and an inch in
length, the two others slenderer. The cloaca is of mod-
erate size, as in Pentacta, and the respiratory trees divide
at once into two very bushy branches. The ovarian tubes
form a brush or round broom-like mass or tuft, about an
inch long, the tubes small, yellow, and of nearly uniform
length, the oviduct straight and bound down to the walls
of the body.
We might here mention the most aberrant type of Holo-
thurians, the Rhopalodina described by Semper, who states
that the body is flask-shaped, with the mouth and vent situ-
ated near each other on the smaller end of the body. Tbx
mouth is surrounded by ten tentacles, and there are ten
papillae around the anus. There is a spacious cloaca or
respiratory tree. " Ten ambulacra diverge from the centre
of the enlarged aboral end of the body, and extend like so
many meridians to near the commencement of the neck of
the flask. In correspondence with each ambulacrum is a
longitudinal muscular band ; and it is an especial peculiarity
of Rhopalodma that five of these are attached to the anal
circlet, and five to the circam-o?sophageal circlet" (Huxley).
The earlier stages of development of Holotlmrians, so far
as known, is like that of star-fishes. The larva when fully
grown is called an auricular ta. It is transparent, cylindri-
cal, annulated, with four or five bands of cilia, and usually
with certain ear-like projections, from which it derives the
name originally given to this larval form. Before the auri-
cularia is fully formed the young Holothurian begins to bud
out from near the side of the larval stomach, the calcareous,
cross-like spicules appear., and the tentacles arise. The ear-
like projections disappear, the auricularia thus becoming
cylindrical. It is soon absorbed by the growing Holothurian,
which in some genera is strikingly worm-like, and it seems
that the Holothurian is more directly developed from the
larva than in the case of the star-fish and sea-nrchins, the
METAMORPHOSIS OF HOLOTHURIANS. 215
metamorphosis being less marked — i.e., growth is more
continuous, as in the Crinoids.
In Holothuria tremula and Synaptula vivipara there has
been observed a very slight metamorphosis, the young de-
veloping directly in a marsupium, as in the star-fishes and
sea-urchins. Cladodaetyla crocea Lesson, of the Falkland
Islands, according to Sir Wyville-Thompson, carries its
young in a sort of nursery, being " closely packed in two con-
tinuous fringes adhering to the water-feet of the dorsal am-
bulacra." He also found that in Psolus ephippifer Wyville-
Thompson, which is covered with calcareous plates, there is
a dorsal group of larger tessellated plates, each supported
by a broad pedicel embedded in the skin. Under these
mushroom-like plates brood-cavities or cloister-like spaces
are left between the supporting columns, and in this archi-
tectural marsnpium the embryos directly develop into sea-
cucumbers. It follows that in all free-swimming Echino-
derm larvae, there is a true metamorphosis as distinct as in
the butterfly, while in other forms in which development u
direct the embryo is sedentary and lacks the cilia and vari-
ous appendages so characteristic of the ordinary larval
Echinoderms ; thus there are different stages in the differ-
ent classes of Echinoderms between direct development 01
continuous growth, and a complete metamorphosis like that
of the star-fish or sea-urchin, in which the pluteus or larva
is but a temporary scaffolding, as it were, for the building
up of the body of the adult.
Turning now to the classification of the Holothurians,
and beginning with the lowest, simplest, most generalized
forms (which are also remarkably worm-like), and ascend-
ing to higher or more complicated forms, we find that there
are two orders, those without feet (Apotla) and those with
ambulacral feet (Pedota).*
* It is possible that the Holothurians should he divided into two sub-
classes, one Diplostomidea Semper, in which the body is spherical and
the mouth and anus are close together, with ten ambulacral rows, etc.,
and the normal, cylindrical, bipolar Holothurians. Semper's Diplostomi-
dea is based on RJiopalodina lageniformis Gray, from the Congo Coast,
and regarded by Semper as the type? of a fifth class of EcliMiodcnns.
216
ZOOLOGY.
Order 1. Apoda. — The simplest apodous form is the
Eupyrgus scaber Lutken, in which the body shows no
external signs of longitudinal muscles, though there are
five small ones, and is covered with spine-like, soft papilla
bearing calcareous plates. We have dredged it
frequently on the coast of Labrador in shoal-
water. It has a circle of fifteen unbranched
tentacles, and is about one centimetre long.
It also occurs in Greenland and Norwegian
waters. Myriotrochus has a transparent skin
dotted with minute white spots, which, when
magnified, appear to be wheel-like, calcareous
plates. It has a single Polian vesicle, and there
is no respiratory tree nor Cuvierian appendages
(Huxley). We have dredged this beautiful
form (M. Rinkii Steenstrup) in sand, in shoal-
water, on the coast of Labrador. A very com-
mon Labrador Holothurian is Chirodota Iceve
Grube (Fig. 153). It lives in shallow, sandy,
retired bays, and is whitish-gray, with five dis-
tinct muscular bands and scattered white spots,
which are calcareous, wheel-like bodies situated
in the skin.
\\ Near Synapta, is Leptosynapta Girardii
(Verrill), our common east coast species, which
lives in sand at low tide. The body is very
long, and the animal when disturbed constricts
its body and breaks up into several pieces. The
skin contains perforated plates and anchor-like
bodies (Fig. 154). In this genus and those pre-
viously mentioned, constituting the suborder
Apneumona and family Synaptidw, the sexes
Fig.i53.-c%i- are united in the same individual, and there
rodota Icuve. Half . . . ., , .
natural «ze. a, is no respiratory tree, while the tentacles are
mouth, closed. . , -,-•, T IIIJT
simply digitated or lobulated.
The next suborder, Pneumophora, forming the familv
Molpadidw, is characterized by having a respiratory tree.
In Caudina the skin is rough with calcareous pieces, the
DISTRIBUTION OF HOLOTHDRIANS.
217
Fig. 154. — Hooks and plates of
Synapta Girardii. — After Verrill.
body ends in a long, tail-like prolongation ; C. arenata
Stimpson has fifteen four-pronged tentacles ; it is com-
monly thrown up on the beaches
of Massachusetts Bay. A deep-
water form, a member of the
abyssal fauna, is Molpadia tur-
gida Verrill, which we have
dredged in over one hundred
fathoms in the Gulf of Maine,
and which ranges southward to
Florida. It has a head-end like
the neck of a bottle, and the end of the body suddenly con-
tracts into a tail, with a very small anus. There are fifteen
tentacles.
Order 2. Pedata, or Holothurians with feet. The mem-
bers of the first family (Dendrochirotce) have tree-like,
branching tentacles, retractor muscles, without Cuvierian
organs. It is represented by Thy one and Pentacta, while
here belong also Lopliotlmria Fabricii Dviben and Koren,
Psolus phantapus and P. squamatus, in which the body is
armed with heavy calcareous plates, and the feet are confined
to a ventral creeping disk.
In the highest family, Aspidocliirotm, there are tentacular
ampullae ; the left respiratory tree is bound to the body-
walls, and there is a single ovary, while Cuvierian organs
are present. Holothuria is the type of the group. H. edulis
Lesson, of the Moluccas and Australia, and H. tremula
forms, when dried, the trepang sold in Chinese markets.
Our H, floridana has been dried and exported to China as
an article of food.
In their geographical distribution the Apoda are mostly
boreal and arctic. Of the Pedata, the Dendrochirotce are
mostly northern or arctic, while the highest group, Aspi-
dochirotce, are mainly tropical. Certain genera (Holothivria^
TTiyone, Psolus,Pentacta, Chirodota, and Synapta) are almost
cosmopolitan.
A few forms attain a great depth, and certain abyssal
forms are often highly colored. . One species, Synapta
218
ZOOLOGY.
similis, lives in brackish water, according to Glaus. Sup-
posed plates of Holothurians have been found in the
Jurassic rocks.
CLASS IV.— HOLOTHUROIDEA.
Worm-like, cylindrical Echinoderms, with a muscular body-ioaU usually
containing calcareous bodies ; with a circle of branched tentacles, a terminal
opening of the intestine, madreporic plate internal, and usually a res-
piratory coecal appendage. Unisexual or bisexual, developing by a metamor-
phosis from cylindrical, auricvlated, free-swimming larvce; or tvmetabolous.
Order I. Apoda. — No ambulacral feet. Family 1. Synaptidce (Eupyrgus,
Chirodota, Synapta). Family 2. Nolpadidce, (Caudina, Mol-
padia).
Order 2. Pedata. — Respiratory tree present, and the ambulacral feet.
Bisexual. Family 1. Dendrochirotce (Thyone, Psolus, Echi-
nocucumis, Pentacta). Family 2. A spidochirotce (Holothu-
ria). Tbe Elasipoda are a group of deep-sea forms.
TABULAR VIEW OP THE CLASSES AND ORDERS OF ECHINODER.MATA,
Pedata.
(Holothuria.)
Apoda.
(Chirodota.)
HOLOTHUROIDEA.
Autechinida.
(Echinus.)
Palechinidfl.
(Melonites.)
ECHINOIDEA.
Asteridea.
(Asterias.)
Op/i tin-idea.
(Ophiura.)
Brachiata.
(Encrinns.)
ASTEROIDEA.
Cystidea.
(Sphaeronites.)
Blaxtoidea,
(Pentreioites.J
CRINOIDEA.
I
ECHINODERMATA.
DISSECTION OF UOLOTUURIANS.
219
Laboratory Work. — The Holothurians are easily dissected by cutting
the body opening longitudinally, and pinning the specimen down iu a
dissecting-pau, with wax on the bottom for holding the pins. The
calcareous plates can be extracted from the body-walls by being placed
iu a solution of potash and mounted in balsam as microscopic objects.
NOTE. — In opposition to the classification on pp. 215-318 it is pos-
sible that the Apoda are a later, much modified group, and derived
from the Pedata, which may have included the primitive Holothuriaus.
of
LlTERATUKE.
O. J. Romanes. Jelly-fish, Star-fish, and Sea-urchins. 1885.
J. Mutter. Seven Memoirs on the Larvae and Development
Echiuoderms. Berlin, 1846-1854.
A. Agassiz. Embryology of the Star-fish. 1864.
E. Metschnikoff. Studien liber die Entwickelungsgeschichte der
Echiuodermen uud Nemertinen. St. Petersburg, 1869.
H. Ludwig. Morphologische Studien an Echiuodermeu. Leipzig,
1877-1878.
Sea-cucumber (Synapta). A, larva; B, young farther advanced, with the Syn-
apta (fd) growing within; C, young become free (after Muller); D, adult Synapta
(Kingsley del.).
CHAPTER VI.
BRANCH VI.— MOLLUSC A.
General Characters of Mollusks. — The characters which
separate this branch from the others, especially the Vermes
arc much less trenchant than those peculiar to other groups
of the same rank, and indeed the author only retains the
Mollusks as a special branch in deference to the general
usage of zoologists, believing that the Mollusca are probably
only a highly specialized group of Vermes, where they were
originally placed by Linnaeus, and bearing much the same
relation to the true worms as do the Rotatoria, the Tuni-
cata, the BracMopoda, etc. It will be seen from the fol-
lowing account of the mollusks, that they travel along, appar-
ently, the same developmental road as the genuine worms,
and then suddenly diverge, and the divergence is not an ad-
vance in a parallel direction, but if anything the road turns
back, or, to change the simile, the branch of the genea-
logical tree bends downwards. It is, and always has been,
extremely difficult to define the Mollusca, their original
bilateral symmetry being partially effaced in most of the
Gastropoda and in some Lamellibranchs, L e., in those
Gastropods with a spirally-twisted shell like the snail, or in
fixed bivalve forms like the oyster, etc. The Mollusca are
usually defined as animals with laterally symmetrical, un-
jointed bodies protected by a shell, with a foot or creeping
disk, and usually Avith lamellate gills, which are folds of the
mantle or body-walls. The special organs characterizing
the Mollusks are the foot and, in nearly all except Lamel-
libranchs, the odontophore ; but the foot of a snail is simply
a modified part of the mantle, and in reality in many forms
but a specialized ventral surface, as is that of certain non-
segmented Avorms, like the Planarians and Nemerteans ; while
MORPHOLOGY OF MOLL USES. 221
the odontophore or lingual ribbon, often absent, is appar-
ently a modification of the pharyngeal teeth of Annelides.
Mollusks in general have a heart consisting of a ventricle
and one or two auricles, and in this respect they are more
like the Vertebrates than other invertebrated animals , the
highly developed eye of the squids and their imperfect car-
tilaginous brain-box are also special characters analogous to
the eye and brain -box of Vertebrates. Still these features
are not homologous with the corresponding parts in the
Vertebrates, and we have already seen that the Tunicata.
and even the Annelides, are much more closely allied to the
Vertebrata than are the Mollusks, which should, perhaps,
be interpolated between the Brachiopods and Tunicates.
The affinities of the Mollusks are, then, decidedly with the
worms, rather than with the Vertebrates.
That the Mollusca are a highly specialized and compara-
tively modern group is shown by the fact that they began
to abound after the Brachiopods had bad their day in the
Silurian seas, and had begun to decay and die out as a type ;
the shelled Mollusca supplanted the shelled Vermes or Brachi-
opods. For the upper Silurian period, and those later, the •
Mollusks prove useful as geological time-marks, especially in
the Cainozoic period, and so much so that Lycll based his
divisions of Tertiary time mainly on the shells which abound
in Tertiary strata.
Although morphologically the shell of a Mollusk is not
the most important feature of the animal, it is very charac-
teristic of them and of great use in distinguishing the species
of existing, but more especially of fossil, forms ; still it is
liable to great variation, and mollusks of quite different
families, and even orders, sometimes have shells much alike,
so that the characters of shells, like many of those drawn
from the peripheral parts of the body, are liable oftentimes
to mislead the student. That the Mollusca are a highly
specialized group is also seen by the enormous number of
existing species, and their wide geographical and bathymet-
rical range. There are about 20,000 living and 19,000
fossil species known, and the group ranks next to the
winged insects, also a comparatively recent and highly
ZOOLOGY.
specialized group, in the number of species and indi-
viduals.
CLASS I. — LAMELLIBRANCHIATA (Acepliala, Bivalves).
General Characters of Lamellibranchs — This group is
represented by the oyster, clam, mussel, quohog, scallop,
etc. By a study of the common clam (Mya arenaria Linn.)
one can obtain a fair idea of the anatomy of the entire class,
as it is a homogeneous and Avell-circumscribed group. The
clam is entirely protected by a pair of solid limestone shells,
connected by a hinge, consisting of a large tooth (in most
bivalves there are three teeth) and ligament (Fig. 155 C L).
The shells are equivalve, or with both valves alike, but not
equilateral, one end (the anterior) being distinguishable from
the other or posterior, the clam burrowing into the mud by
the anterior end, that containing the mouth of the mollusk.
The hinge is situated directly over the heart, and is there-
fore dorsal or haemal. On the interior of the shells are the
two round muscular impressions made by the two adductor
muscles and the pallial impression, parallel to the edge of
the shell, made by the thickened edge of the mantle. On
carefully opening the shell, by dividing the two adductor
muscles, and laying the animal on one side in a dissecting
trough filled with water, and removing the upper valve, the
mantle or body-walls will be disclosed ; the edge is much
thickened, while within, the mantle where it covers the el-
liptical rounded body is very thin. The so-called black
head, or siphon, is divided by a partition into two tubes, the
upper, or that on the hinge or dorsal side, being excurrent,
the lower and larger being incurrent — a current of sea-water
laden with minute forms of life passing into it. Each orifice
is surrounded with a circle of short tentacles. This siphon
is a tubular prolongation of the mantle-edge, and is very ex-
tensible, as seen in Fig. 155, A ; it is extended, when the
clam is undisturbed, from near the bottom of its hole to the
level of the sea-bottom. In the fresh-water mussel ( Unio,
Fig. 156) the two siphonal openings are above the level of
ANATOMY OF THE CLAM.
223
the sandy bottom of the water, when the mussel is plough-
ing its way through the
sand with its tongue-
shaped foot, which is a
muscular organ attach-
ed to the visceral mass,
and is a modification
of the under lip of the
larval mollusk In the
foot is an orifice for
the passage m and out
of water, but the spurt-
ing of water from the
clam's hole, observed
in walking over the
flats, is the stream eject-
ed from the siphon.
The inflowing currents
of water pass from the
inner end of the mus-
cular siphon below the
lenticular visceral mass
to the mouth, which is
situated at the anterior
end of the shell, oppo-
site the siphon. The
opening is simple, un-
armed, without lips,
and often difficult to
detect. On each side
of the mouth is a pair
of flat, narrow-pointed
appendages called pal-
pi. The digestive ca-
nal passes through a
dark rounded mass,
mostly consisting of
the liver, covered ex-
ternally by the ovarian
Fig. 155.— A. Mya arenaria with its siphons extended ;
in its natural position in the mud head-end downwards.
B, transverse section of Unio, showing the position of the
spring opening the shell. M, adductor muscle ; the liga-
ment represented by dark mass. C, section of Mya.show ng
the position of the spring to open the shell ; L, ligiuiient.
D, transverse section of Unio (after Brooks) ; ab, visceral
mass ; o, auricles ; v, ventricle , ;', intrstinr ; t, glandular
part of kidney ; z, non-glandular part of kidney ; y, sinus
venosus ; iy, inner, eg, outer, gills ; m, mantle.
224
ZOOLOGY.
masses. There is no pharynx armed with teeth as in the
Cephalophora and Cephalopoda, but the oesophagus leads to
a tubular stomach and intestine, the latter loosely coiled sev-
eral times and then passing straight backwards along the dor-
sal side under the hinge and directly through the ventricle of
the heart, ending posteriorly opposite the excurreut division
Fig. 156.— Tnio complanatus, partly buried in the sand, the siphonal openings
above the level of the river-bottom.— After Morse.
of the siphon. Through the visceral mass passes a curious
slender cartilaginous rod, Avhose use is unknown, unless it be
to support the voluminous viscera. The gills or branchiae are
four large, broad, leaf -like folds of the mantle, two on a side,
hanging down and covering each side of the visceral mass
(Fig. 155, D, G). The heart (Fig. 15?) is contained in a deli-
\ cate sac, called the pericardium, and is situ-
ated immediately under the hinge ; it consists
of a ventricle and two auricles ; the former is
easily recognized by the passage through it of
the intestine (Fig. 155, D, v), usually colored
i57.-Heart dark, and by its pulsations. The two wing-
J- like auricles are broad, somewhat trapezoidal
iT-AYt"" in form. Just behind the ventricle is the so-
Morel.' canea « aortic bulb." The arterial system is
finite complicated, as is the system of venous sinuses, which
can be best studied in carefully injected specimens. At the
base of the gills, however, is the pair of large collective
branchial veins. The kidney, or "organ of Bojanus," is a
large dusky glandular mass (Fig. 158, 4) lying below but next
ANATOMY OF THE CLAM. 225
to the heart ; one end is secretory, lamellar and glandular,
communicating with the pericardial cavity, while the other
is excretory and opens into the cavity of the gill. The
nervous system can be, with care and patience, worked out
in the clam or fresh-water mussel. In the clam (My a arena-
Fig. 168.- Circulatory system of Anodonta, a fresh-water mussel, after Bojanns.
1, ventricle ; 2, arterial system ; 14 and 15, veins which follow the border of the
mantle. The veins lead the blood in part directly towards the organ 4, which is the
kidney or "organ of Bojanus," and in part to the venous sinus of the upper surface
of this organ ; 5, veins which carry back the blood from the gills, the rest going to
the sinus, 6, where arise the branchial arteries ; 7, 8, the branchial veins, and 9, the
gill. — From Gervais et Van Beueden.
ria, Fig. 159) it consists of three pairs of small ganglia,
one above (the "brain") and one below the o?sophagus (the
pedal ganglia) connected by a commissure, thus forming an
cesophageal ring ; and at the middle of the mantle, near the
base of the gills, is a third pair of ganglia (parieto-splanch-
nic), from which nerves are sent to the gills and to each
division of the siphon. This last pair of ganglia can be
usually found with ease, without dissection, especially after
the clam has been hardened in alcohol. The car of the clam
is situated in the so-called foot ; it bears the name of otocyst
(Fig. 160, i], and is connected with a nerve sent off from the
pedal ganglion. It is a little white body found by laying
open the fleshy foot through the middle. Microscopic ex-
amination shows that it is a sac lined by an epithelium, rest-
ing on a thin nervous layer supported by an external coat of
connective tissue. From the epithelium spring long hairs ;
the sac contains fluid and a large otolith. The structure of
this octocyst may be considered typical for Invertebrates.
226
ZOO LOOT.
The ovaries or testes, as the sex of the clam may be, are
bilaterally symmetrical, blended with the wall of the visce-
ral or liver-mass, and are yellowish. The genital openings
Fig. 159.— Netvons system of the clam, natural size. «, cesophageal ganglion : b,
commissure anterior to the mouth ; c, pedal commissure ; d, pedal ganglia , e, parieto-
splanchnic commissures ; /, parieto-splanchnic ganglia ; g, branchial nerves ; h, I, pal-
lial nerves ; i, siphonal nerves ; A, aiial nerves ; t/t, nerves to the anterior adductor.—
Drawn by W. K. Brooks.
are paired and lie near the base of the foot. Both eggs and
semen arise from the epithelium of the sexual glands. The
eggs pass out into the body-cavity, or accumulate between the
ANATOMY OF THE CLAM.
227
gills, where the embryos in some species partially develop.
Impregnation probably takes place within the branchial
chamber, the spermatozoa being
swept in with the respiratory
current, and coming in contact
with the eggs as they are dis-
charged.
An excellent general view of
the relation of parts to the
body -walls and shell may be
seen by hardening a clam, or
better a fresh -water mussel,
Unio (see Fig. 155, D) in alco-
Fig. 160. -Pedal ganglia and oto- hoi, and then making trans-
cyste (ears) of the clam, magnified 10 VPVQp confirms \ eppfinn ran
diameters, d, pedal ganglia ; e, pedal VCrSC S6C IIS. A. SC
commissures;/, line of union of gan- K , flo'lfod off ill water aild 6X-
glia; <7, nerve from commissure to
muscles of loot ; A, auditory nerve ; i, amilied With a leilS. The per-
otocyst ; k, nerves from ganglia to r
the pedal muscles.— Drawn b> vv K. feet bilateral symmetry of parts
Brooks. J J
will thus be seen.
The above description will Answer for the majority oi la-
ft
. 161.— Lima Mans, flying through the water, its long numerous filaments ex-
tended.—From Brehm's •' Thierlehen."
mellibranchiate mollusks ; in the oyster (Ostrea) or in Ano-
228
ZOOLOGY.
mia the shell is inequilateral, one, usually the lower, being
fixed to some object, and the intestine does not pass through
the ventricle ; in Area the ventricle is double. In Lucina
and Corbis there is but one gill on each side, and in Pecten,
Spondylus and Tngonia the gills are reduced to comb-like
Fig. 162.— Mytilis edulis, common mussel, a, mantle ; k. foot; c, byssns ; rt and t,
muscles retracting the toot ; /. mouth ; a, palpi ; A. visceral mass • z, inner giii ; j,
outer gil].— From Brehm's '• Thierleben.
processes. There are usually no eyes present ; in the scallop
(Pecten), however, there is a row of bright shining eyes
with tentacles along the edge of the mantle, and contrary
to the habits of most bivalves, the scallop can skip over the
surface of the water by violently opening and shutting its
shell. Triqonia is also capable of leaping a short distance ;
while Lima (Fig. 161) is an active flyer or leaper. The Ameri-
can oyster* is dioecious, while most mollusks are monoecious
or hermaphroditic. The foot varies much in form; in the
mussel (Mytilus, Figs. 162, 163), Pinna, Cyclocardia (Car-
dita) (Fig. 164), and the pearl-oyster it is finger-shaped and
* The European oyster is clearly hermaphroditic (Ryder).
TYFICA L Bl VAL VES.
229
grooved, with a gland for secreting a bundle of threads, the
byssus, by means of which it is anchored to the bottom.
Fig. 164.
Fig. 163.—Mytilus edulis, common mussel, with its fringe expanded, and an-
chored by its byssus.— After Morse.
Fig. 164.— Cyclocardia novanglive, natural size.— After Morse.
The foot in the quohog (Fig. 165 A, Venus mercenaria},
Mulinia (166 B) and Clidiophora (Fig. 167) is large, these
Fig. 165 A.— Venus mercenaria. quohog. natural size, with the foot and siphons.
Fig 166 B.— Mactra (Mulinia) lateralis, natural size.— After Verrill.
mollusks being very active in their movements. In Glyci-
meris (Fig. 168) the fringe is toothless, much as in the
•oyster. In Mactra (Fig. 169) the middle tooth is large, the
230
ZOOLOGY.
corresponding cavity large and triangular. In Saxicava and
Panopcea (Fig. 170), the pallial line is represented by a
row of dots. In Macoma (Fig.
171) the siphons are very long.
Lithodomus, the date shell,
one of the mussels, bores into
corals, oyster shells, etc. ; the
common Saxicava
excavates
Fig. 167.-
tural size. — After
errill.
trilineata, na-
Pltolas and Petricola.
said to be luminous.
stone, as does GastrochcBna,
Many boring Lamellibranchs are
Fig. 168.—Cflycimeris siliqua, natural size.— After Morse.
A very aberrant form of bivalve mollusk is Cla-iciyella, in
which the shell is oblong, with flat valves, the left cemented
to the sides of a deep burrow. The tube is cylindrical,
fringed above and ending below in a disk, with a minute
central fissure, and bordered with branching tubules. In
Asperyillum, the watering-pot shell, the small bivalve shell
is cemented to the lower end of a long shelly tube, closed
below by a perforated disk like the " rose" of a watering-
pot.
The most aberrant Lamellibranch is the ship-worm, Teredo
navalis Linn. (Fig. 174). This species is now cosmopolitan.
and everywhere attacks the hulls of ships and the piles of
wharves. It is one of the most destructive to human inter-
ests of all animals. The body is from one to two feet long,
slender, fleshy; it lives in a burrow lined with limestone,
while the shell itself is globular, and lodged at the farther
FORMATION OF PEARLS.
231
end of the tube or burrow. The mantle lobes of the ani-
mal are united, with a minute opening for the -foot, whifh is
small, suoker-like. The heart is not pierced by the mte,s-
Fig. 169.— Mactra avails, natural size.— After Morse.
tine, while the siphons are very long and furnished with
two shelly styles.
Pearls are sometimes produced in bivalve shells by particles
of sand getting in between the mantle and the shell, which
Fig. 170.—Panop<ea arctica, natural size. — After Morse.
cause an irritation to the tissues of the mantle and the for-
mation of a nacreous shelly matter around the nucleus.
Excellent pearls are sometimes found in fresh-water mussels,
ZOOLOGY.
but the purest occur in the pearl oyster, Meleagrina marga-
ritifera (Linn.), which occurs at Madagascar, Ceylon, the
Persian Gulf, and at Panama. The largest pearl known
measures two inches long, four round, and weighs 1800
grains. All bivalves pass through a metamorphosis after
birth. The development of the
oyster is a type of that of most La-
mellibranchs.
A single oyster may lay about
2,000,000 eggs ; they are yellow, and
after leaving the ovary are for the
.a '.proximo,, mOst part retained among the gills.
natural size.— After Morse. -1
In America the oyster spawns from
June till September ; during their growth the eggs are en-
closed in a creamy slime, growing darker as the "spat" or
young oyster develops.
The course of development is thus : after the segmenta-
tion of the yolk (morula stage), the embryo divides into a
clear peripheral layer (ectoderm), and an opaque inner layer
containing the yolk and representing the inner germinal
layer (endoderm). A few filaments or large cilia arise on
•what is to form the velum of the future head. The shell
then begins to appear at what is destined to be the posterior
end of the germ, and before the digestive cavity arises. The
digestive cavity is next formed (gastrula stage), and the anus
appears just behind the mouth, the alimentary canal being
bent at right angles. Meanwhile the shell has grown enough
to cover half the embryo, which is now in the " Veliger"'
stage, the "velum" being composed of two ciliated lobes in
front of the mouth-opening, and comparable witli that of
the gastropod larvse. The young oyster, as figured by Salen-
sky, is directly comparable with the Veliger of the Cardium
(Fig. 172). Soon the shell covers the entire larva, only the
ciliated velum projecting out of an anterior end from be-
tween the shells. In this stage the larval oyster leaves the
mother and swims around in the water. According to
Brooks the American oyster becomes a free-swiming larva
in six hours after the egg is fertilized. When about .03 mm.
in diameter it becomes fixed. The oyster is said to be
Fig. 171.'). —Section through the
oyster along- the line o of Fig 171C
(enlarged twice), a', a", dorsal and
ventral branches of the anterior
aorta in section; br, artery to gills-
c, connective tissue; ff, giils in sec-
tion; g , internal cavities of I lie gills-
ffe, egg-gland ; j, i, cross-sections of
tHe intestinal tube; /, liver- mt
mantle; sb, suprabrancliial or water
spaces above the gills; st, stomach-
vc, vena cora.— After Ryder
Fig. 1 71 c.— The oyster-drill.
(Natural size.)
mantle; P,pa]p; « ills!lAfter Ryder'.
the, ,efrf?S are formed:
> adductor
<
heart; mt
[To face page 833.]
Fig. 171e. — Anatomy of the oyster, cm, auricle; ve, ventricle; bm, body-mass;
cl, cloaca; g, gills; i and i', intestine; I, liver, with its ducts opening into the
stomach; M, adductor muscle; »i, mouth; rnt, mantle; o, the line of section of
figure passing through the stomach; p, outer wrinkled surface of inner or lower
palpi; v, vent.— After Ryder.
Fig. 171eZ — 1. Young oyster seen from the side immediately after fixation by
the mantle-border (wi>; v, ciliated velum, or paddle; 2, four young European oys-
ters taken from the beard of the parent, enlarged 06 times; 0, very young spat,
showing the peculiar form of the true larval shell and that of the spat > •'!">
times; 7, twenty-days-old spat (natural size); 10, young oyster, 2J to 3 months
old.— After Ryder.
[To face page 2,33]
EMBRYOLOGY OF CARDIUM.
233
three years in attaining its full growth, but is able to propa-
gate at the end of the first year.
The development of the cockle (Cardium pygmmim), is
much the same. After passing through a blastula and gastrula
stage, the embryo becomes ciliated on its upper surface and
already rotates in the shell. On one side of the oval em-
bryo is an opening or fissure, on the edges of which arise two
tubercles which eventually become the two *' sails" of the
velum. The next step is the differentiation of the body
into head and hind body, i.e., an oral (cephalic) and postoral
region. Out of the middle of the head grows a single very
large ciliuin, the so-called flagellum (l^ig. 172 A, Ji ; v,
Pis. 172. —The development of the cockle shell (Cardium). A, the trochosphere ;
V, ciliated crown ; Jt, flagellum. B. Veliger stage, with the thell developing ; v,
velum ; m, mouth ; li, liver lobes ; t, stomach ; t, intestine ; mt, mantle ; /", loot ;
ml, muscle ; n, nervous ganglion.— After Lovcm.
velum). The shell (B, sh) and mantle (mt; ml, muscle)
now begin to form. From the inner yolk-mass are developed
the stomach, the two liver lobes (li) on each side of the
stomach (/), and the intestine (i). The mouth (m), which
is richly ciliated, lies behind the velum, the alimentary canal
is bent nearly at right angles, and the anus opens behind and
near the mouth. The velum (Fig. 172 B, v) really consti-
tutes the upper lip, while a tongue-like projection (B, f) be-
hind the mouth is the under lip, and is destined to form the
large unpaired "foot," so characteristic of the mollusks.
The shell arises as a cup-shaped organ in both bivalves and
univalves, but the hinge and separate valves are indicated
very early in the Lamellibninchs. At the stage represented
234 ZOOLOGY
by Fig. 172 B, the stomach is divided into an anterior and
posterior (^yloric) portion. The liver forms on each side of
the stomach an oval fold, and Communicates by a large open-
ing with its cavity ; while the intestine elongates and makes
more of a bend. The organ of hearing then arises, and be-
hind it the provisional eyes, each appearing as a vesicle with
dark pigment corpuscles arranged around a refractive body.
The nerve-ganglion (n) appears above the stomach. The
two ciliated gill-lobes now appear, and the number of lobes
increases gradually to three or four. The foot grows larger,
and the organ of Bojanus, or kidney, becomes visible. The
shell now hardens ; the mouth idvances, the velum is with-
drawn from the under side to the anterior end of the shell.
In this condition the Yeliger remains for a long time, its long
flagellum still attached, and used in swimming even after the
foot has become a creeping organ. Latest of all appears the
heart, with the blood-vessels.
Upon throwing off the Veliger condition, the velum con-
tracts, splits up and Loven thinks it becomes reduced to the
two pairs of palpi, which are situated on each side of the
mouth of the mature Lamellibranch. The provisional eyes
disappear, and the eyes of the adult arise on the edge of the
mantle.
In the fresh-water mussels (Unio) the developmental his-
tory is more condensed. The velum of the embryo is want-
ing or exists in a very rudimentary state. The mantle and
shell are developed very early. The
young live within the parent fastened to
each other by their byssus. The shell
(Fig. 173) differs remarkably from that of
the adult, being broader than long, trian-
^ gular, the apex or outer edge of the shell
Fig iTS^Youn Unio hooked, while from different points within
—After Morse. project a few large, long spines. So dif-
ferent are these young from the parent that they were sup-
posed to be parasites, and were described under the name of
GlocMdium parasiticum. They are found in the parent
mussel during July and August.
The ship-worm (Teredo navalis Linn. Fig. 174) after the
DEVELOPMENT OF THE SHIP-WORM.
235
segmentation of the yolk (Fig. 175 J) passes through a
veliger stage, the shell begins to grow, and when five days
V
pjjr 174.— The Ship-worm, t, siphons ; p, pallets ; c, collar ; s, shell ; /, foot. —
After Verrill.
and a half old the germ appears as in Fig. 173, B, the shell
almost covering the larva. Soon after this the velum
becomes larger, and then decreases, the gills arise, the audi-
tory sacs develop, the foot grows, though not reaching to the
edge of the shell, and the larva can still swim about free in
the water. When of the
size of a grain of millet,
it becomes spherical, as
in Fig. 175, C, brown
and opaque. The long
and slender foot projects
far out of the shell, and
the velum assumes the
form of a swollen ring on
which is a double crown
of cilia. The ears and Fig. 175.— Development of the Ship-worm.
-i 1 -I A, egg, with the yolk once divided; B, the
eyes develop more, and veligw enclosed by the bivalve shells ; C, ad-
tliP <i7-iimil qlrprmfplv vanced veliger with the large foot (/) and velum
nateiy W-_After Quatrefages.
swims with its velum, or
walks by means of the foot. At this stage Quatre- (
fages thinks it seeks the piles of wharves and floating
wood, into which it bores and completes its metamor-
phosis. On the coast of New England the ship-worm
lays eggs in May and probably through the summer.
23$ ZOOLOGY.
Indeed most mollusks spawn in the summer. Species of
Kellia, Galeomma, and Montacuta are viviparous.
Some bivalves get their growth in a single year. The fresh-
water muscles live from ten to twelve years and perhaps
longer ; while Tridacna gigantea probably lives from sixty
years to a century. Of about 14,000 known species of
Lamellibranchs, from 8000 to 9000 are fossil.
CLASS I.— LAMELLIBRANCHIATA.
Bilaterally symmetrical mollusks, with two valves lined by the mantle, con-
nected by a dorsal hinge and ligament; no head ; mouth unarmed, with
two pairs of labial palpi ; intestine coiled in the visceral mass, usually
passing through the ventricle', and always ending fit the posterior, usually
siphon-bearing end, of the body. Foot small, sometimes nearly wanting;
containing two ears (otocysts}. Usually two pairs of large leaf-like gills on
each side of the visceral mass. Sexes usually in separate individuals.
Embryo passing through a so-called morula, gastrula, and free-swimming
condition.
Order 1. Asiphonia. — Body-wall or mantle without siphons. Shell
sometimes inequivalve. (Ostrea, Anomia, Pecten, Melea-
grina, Mytilus, Area, Trigouia, Uuio, and Anodonta.)
Order 2. Siphoniata. — Siphons present. Shell equivalve. (Chama
Tridacna, Cardium, Venus, Mactra, Tellina, Solen, Clava-
gella, Aspergillum.)
Laboratory Work. — In dissecting the clam, etc., the work should be
performed under water, in a dissecting trough. One shell should be
removed by cutting the adductor by a pointed scalpel, the mantle dis-
sected off and thrown aside, so as to expose the gills, heart, and kid-
neys. In dissecting the. nervous system it is well to introduce a probe
into the mouth, and then cut down towards it from above, when the
white suprao3sophageal ganglia or "brain" will be found, and the
other ganglia can thence be traced by the commissures leading from the
" brain." To find the pedal ganglia and otocyst, cut the foot vertically
in two. The heart can be readily found, and the large vein at the base
of the gills, but the arterial and venous systems can only well l>«
studied after making careful injections. For ordinary or even quite
fine injections, Sabatier used a mixture of lard and turpentine, some-
times adding a little suet or wax to thicken the paste, which was
colored chrome yellow, vermilion, or blue. For histological exami-
nation he used essence of turpentine, colored as before, or gelatine
SCAPHOPODA.
colored by carminate or ammonia, or Prussian blue dissolved in oxalic
acid, or the precipitate of chromate of lead, or he even injected air
into the vascular cavities. The mollusk should, before injection, be
allowed to slowly die for several days, and the fluids to leave the body.
The injection should be made before decomposition has set in, otherwise
the vessels will burst. Some anatomists plunge rnollusks into water
to which has been added alcohol ;md chlorhydric acid. After remaining
in this fluid for a day or two they can be injected. The arterial system
can best be injected by the aortic bulb, or aorta ; the venous system
may be filled from the foot through the aquiferous orifice, by the
adductor muscle, or by any of the large veins. After injection the
animal should be plunged into cold water to hasten solidification and
then placed permanently in alcohol.
CLASS II. — CEPHALOPHORA (Whelks, Snails, etc.}.
General Characters of Cephalophores. — We now come to
Mollusca with a head, distinguishable from the rest of the
body, bearing eyes and tentacles ; but the bilateral symmetry
of the body, so well marked in the Acephala, etc., is now
in part lost, the animal living in a spiral shell ; still the foot
and head are alike on both sides of the body ; while the
foot forms a large creeping flat disk by which the snail glides
over the surface. Moreover, these mollusks have, besides
two pharyngeal teeth, a lingual ribbon or odonfophore. In
a shelless land-snail (Onchidium) Semper has discovered the
existence of dorsal eyes, constructed, as he claims, on the
Vertebrate type.* They are in the form of little black dots
scattered over the back of the creature, and their nerves
arise from the visceral ganglion. Familiar examples of the
Ceplialophora are the sea -snails, the sea -slugs, and the
genuine air-breathing snails and slugs.
Order 1. Scaphopoda. — A very aberrant type of the class
is Dentalium, the tooth snail, common in the ocean from
ten to forty fathoms deep, on our coast. It lives in a long
slender tooth-like shell, open at both ends, while the animal
has no head, eyes, or heart, and the foot is trilobed. Owing
to the presence of a lingual ribbon, we would retain it in the
present class, though it is a connecting link between this and
* Over 10,000 "eyes," or sense-organs, occur in the shell of Chiton.
238
ZOOLOGY.
the preceding class, and is, by some authors, regarded as
the type of a separate class (Scaphopoda). The sexes of
Fi&. 176.— Development of Dentalium. A, morula ; B, trochosphere ; C. annu-
lated larva; 1), larva with its rudimentary shell ; z, velum ; a. shell ; E. young much
farther advanced, the shell or body segmented ; d, rudimentary tentacles ; j, sub-
oesophageal nerve-ganglia ; //", digestive canal, and liver (/') ; the foot protrudes
from the shell. All magnified.— After Lacaze-Duthiers.
Dentalium are distinct. The young is a trochosphere and
afterwards becomes segmented, and the univalve
shell then appears. (Fig. 176.)
Order 2. Pteropoda. — In these winged-snails
the head is slightly indicated and the eyes are
rudimentary ; while they are easily recognized by
the large wing-like appendages (epipodium), ne
on each side of the head. The shell is conical
or helix-like. The species are hermaphroditic.
Cavolina tridentata Lamarck and Styliola vitrea
Verrill (Fig. 178) are pelagic forms, occurring on
Fig. vn.-Dm- the high seas, and are occasionally taken with the
talium Indiana- * _T _ . ..
nun. Used as tow-net off the southern coast ot JNew .England.
shell money. — . , • -n i • ^ j.i • e ^
After Stearns. Lwwcina arctica rabr. is 01 the size 01, and
looks like, a sweet pea, moving up and down in the water.
It is common from Labrador to the polar regions.
PTEROPODA.
239
A common form, occurring at the surface in harbors
north of Cape Cod, as well as many miles off shore, is Spiri-
alis Gouldii Stimpson, the shell of which
resembles a conical Helix. The largest
form on the eastern coast of North
America, extending from New York to the
polar seas, is the beautiful Clio ne pap illon-
acea of Pallas, which has a head and lin-
gual ribbon. It is rare on the coast of
New England, but abundant from Labra-
dor northward. We have observed it
rising and falling in the water between
the floe-ice on the coast of Labrador. It
is an inch long, the body fleshy, with no
shell, the wings being rather small.
The larvae of the Pteropods pass through
a trochosphere stage, being, as in Cavolina,
spherical, with a ciliated crown. It after-
wards assumes a veliger form. Fig. ] 79 represents a worm-
like, segmented, Pteropod larva, the adult of which is
unknown. In other genera the larvae are annulated, resem-
bling the larvae of Annelides.
The Pteropods are, in some degree, a generalized type.
They have a wide geographical distribution and
•* a high antiquity; forms like Uiivoliiut, viz. :
Theca, Conularia, TentaculUes, Cornulites,
etc., dating back to the palaeozoic formation ;
Theca-like forms (Piiyiunculus and Hyolithes)
occurring in the primordial rocks.
Order 3. Gastropoda. — This great assemblage
f^™"1^ of mollusks is represented by the sea-slugs,
limpets, whelks (Figs. 180-183), snails, and
Fig. i79.-ptero- slugs. The head is quite distinct, bearing1 one,
pod larva. ,. . 1,1 , , .,
and sometimes, as m the land-snails, two pairs
of tentacles, with eyes either at the bases, or at the ends of
the tentacles, or, as in Trivia calif or nica (Fig. 184), they
are situated on projections near the base of the tentacles.
All the Gastropods move or glide over the surface by the
broad creeping-disk, a modification of the foot of the clam,
240 ZOOLOGY.
etc. The head is alike on each side, but posteriorly the body
FIG. 180.
FIG. 182.
FIG 181.
FIG. 183.
Fig. 180.— A Whelk. Buccinum cretaceum. Labrador.
Fig. 181. — A Whelk. Buccinum ciliatinn. — After Morse.
Fig. 182.— Strniiibiis pugilis. West Indies.— From Tenney's Zoology.
Kig. 18:1— Pelican's Foot. Aporrhais occidentalis. Northern New England.
After Morse.
ANATOMY OF THE SNAIL.
241
is, in those species inhabiting a spiral shell, asymmetrical
and wound in a spiral, the visceral mass extending into the
apex of the shell. In the Nudibranchs (Figs. 190, 192), and
the sing, the body being naked is symmetrical
on each side.
The digestive tract is doubled on itself, the
vent ending on one side of the month. In
some Nndibranchs the intestine has numerous
lateral offshoots, or gastro-hepatic branches,
which resemble similar structures in the Plana-
rian and Trematode worms. A heart is always
present, except in the parasitic Enlwonclia,
and sometimes, as in Chiton, Ncritinti, and
Haliotis, it is perforated by the intestine. In
some genera there are two auricles to the heart,
but as a rule but one is present. The Gastro-
pods breathe by gills either free, or contained
in a cavity in the mantle, while in the land-
snails (Pulmonatd) the air is breathed directly by a lung-like
gill in a mantle-cavity. The kidney is single. The sexes
are either distinct or united in the same individual.
An excellent idea of the structure of a typical Gastropod
may be obtained by a dissection of Nafica (Lunatia) keros.
This is a large mollnsk, common between tide-marks from
Labrador to Georgia. On taking it up the student will
notice the large, round, swollen, porous foot, from which
the water pours as if from the "rose" of a watering-pot.
The shell is large, composed of several whorls, with a small
flattened spire or apex. The aperture is large, lunate in
shape, and can be closed by a large horny door or oper-
cnlnm. (In some mollusks, X/itim, Turlin, etc., the oper-
culum is of solid limestone, and small ones are used as "eye-
stones," being inserted in the eye and moved about by the
action of the lids, thus cleansing the eye of irritant particles
of dust, etc.)
The animal should then lie placed in a dish of salt water,
and its movements observed. There are but two short,
broad, flattened tentacles, situated on a flap or heacl-lobo
(prosoma) of the mantle or body-walls. No eyes are present
ZOOLOGY.
in this species. The month is situated in front of the foot
and at the base of the head-lobe, and is bounded bv large puck-
ered swollen lips. Cutting down from between the tentacles,
a large buccal mass, the pharynx, is exposed. The mouth-
cavity is roofed with two broad quadrant-shaped, flat thin
teeth, with the free-edge serrated. On the floor of the
mouth lies the "tongue," or lingual ribbon (Odontophore),
which is folded once on itself, and is a thin band composed
of seven rows of teeth, those forming the two outer rows
long and much curved, those of the central row being stout
and three-toothed. The long slender oesophagus is tied
down, near its middle, by the brain (supracesophageal gan-
glion); just behind and beneath which are the two large
salivary glands. The oesophagus suddenly dilates into a
large stomach-like pouch, which is much larger in this
species than in other forms allied to it. It is a sort of crop
or proventriculus (the organ of Delle Chiaje), and rarely oc-
•curs in the Gastropods. On laying it open, it may be seen
to be spongy at its anterior end, and posteriorly divided by
numerous transverse partitions into small cavities. The
'oesophagus beyond it is again slender, and leads to the
stomach situated in the apex of the shell, partly embedded
in the liver-mass which lies mainly beyond it. From
the stomach the intestine returns to the head, widely dilat-
ing into a large sacculatcd cloaca, before the free up-
turned vent, which is situated on the right side behind and
to the right of the right tentacle. The nervous system is
represented by a pair of 1'irge ganglia, forming the brain
(supracesophageal ganglia) situated just below and behind
the pharynx. The two other ganglia were not traced, but as
.a rule in all Ceplialopliora there are three pairs of ganglia,
i. e., the brain (supracesophageal ganglia) with commissures
passing around the gullet to the pedal or infraoesophagea]
ganglia, thus forming the oesophageal nervous ring, while the
visceral or parieto-splanchnic ganglia are placed at a varying
distance behind the head.
The heart, contained in its pericardial sac, and consisting of
a ventricle and auricle, is situated near the posterior end of
tiie gills. The latter are disclosed by laying aside the man-
DEVELOPMENT OF GASTROPODS.
243
tie on the left side of the body behind the head. In a large
Linmtia it is an inch long, with a vein at the base, the gill-
lobes arranged like the teeth in a comb. A smaller, much
narrower gill lies within and parallel to it. The ovary is
.situated near the stomach, the ovi-
duct ending near the vent.
The eggs are- laid in capsules (Fig.
185, Pnrpurd lii/iUlii* and two egg-
capsules) of varied form attached
to rocks or, as in Trnrluix and the
Nudibranchs, in masses of jelly at-
tached to sea-weeds or stones.
As a type of the mode of devel- After Morse,
-opmeiit of Gastropods may be cited that of Calyptrcea si~
nensis, represented in our waters by Oali/ptrcca striata Say
(Fig. 18G).
FIG 186.
PIG. 187
FIG. 183.
Fig. 186. — Cfih/pfrien afrintrt, natural f=ize.— After Moree.
Fig. 187. —Veliger of Calyptnea. f, foot ; v, velum ; m, mouth ; ce, ectoderm ; 'cet
inesoderm. —After Salensky.
Fig. 188.— Veliger of C'alyptrfpa farther advanced, m, mantle ; v, velum ; f, font ;
h, larval heart ; n, permanent ; k, primitive kidney ; s, crosses the shell and rests or.
the yolk.— After Salensky.
According to Salensky, after segmentation of the yolk
into eight cells the first four cells or "spheres of segmenta-
tion" subdivide, enclosing the yolk-mass, and constituting
the ectoderm or outer germ-layer, the yolk-mass forming the
endoderm. The cells of the outer germ-layer multiply and
form the blastoderm, from which the skin, mantle, and ex-
ternal organs, as well as the walls of the mouth, arise. The
'•' primitive" mouth of the gastrula is formed by the invagi-
244
ZOOLOGY.
nation of the outer germ-layer ; the sides of the primitive
mouth form the two sails of the velum or swimming organ,
and the embryo now assumes the veliger stage (Fig. 187).
Soon the middle germ-layer (mesoderm) arises, and from
the cells composing it are developed the muscles of the foot
and head, as well as the heart itself. The mantle or body-
wall next develops, and from it the shell, which originates in
a cup-like cavity Avhich is connected only around the edge
witli the mantle, being free in the centre. The eyes and ears,
or otocysts, next appear, both organs arising as an infolding
of the outer germ-layer. Hitherto symmetrical, the alimen-
tary canal now begins to curve to the left, and the visceral
sac, or posterior part of the embryo hangs over on one side.
The nervous system is the last to be developed.
Fig. 188 represents the asymmetrical larva with the shell
enveloping a large part of the body, and the ciliated velum
(v) and foot (/) well developed. A temporary larval heart
(It] assumes quite a different position from the heart of the
adult, and the primitive, deciduous kidney (k) is situated in
quite a different place from the permanent kidney. The
further changes consist in a gradual development of the hel-
met-like shell, the disappearance of the temporary larval
structures, and the perfection of the organs of adult life, the
gills appearing quite late.
The development of Troclius, the top-shell, exhibits more
strikingly the trochosphere and
veli £re r stages of molluscan life,
O ~
and most Gastropods develop
like this form. The velum
at first forms a ciliated ring
(Fig. 180, A, v) on the front end
of the trochosphere. Fig. 189,
B, represents the veliger state.
It thus appears that the tem-
porary larval or veliger form of
the Gastropods are of vermian
origin, the organs last to be de-
veloped, L'e., the foot, shell and lingual ribbon, which are the
distinctively molluscan characters, being the last to appear.
Fig. 189.— Larval Trochm. A, tro-
chosphere ; v, velum ; B, velieer state ;
d, month ; /, foot ; s, shell.— After
Salensky.
NUDIBRANCH MOLL UtiKS.
215
The Xudibranch mollusks, such as the Eolis and Doris and
allied forms, breathe by external gills, arranged in bunches
on the back, as seen in Fig. 190, sEolis (Mon-
tagua) pilata (Gould), a common species on
the coast of New England. In Doris (Fig.
192), they are confined to a circle of pinnate
gills on the hinder part of the back. They are
Com-
FIG. 190. FIG. 191. FIG. 192.
Fig. 190.— <£Ww,a Nudihranch.
Fig. 191. — Veliger of Tergipes, v, velum ; s, shell ; d, foot ; b, otocysts. — After
Schultze. .
Fig. 192.— Doris bilameUuta. New England coast.
shelless, and not uncommon just below low-water mark,
laying their eggs in jelly-like masses coiled up on stones and
the surface of sea-weeds. Though the adults are shelless,
the embryos at first have a shell
(Fig. 191, s), indicating that
the Nudibranchs have descend-
ed from shelled Gastropods.
Fig. 191 represents the veli- Fi?_ m.-phygai
ger of Tergipes ladnulata mon pond-enail.— After Morse.
Schultze, allied to Doris, with its large ciliated velum, and
protected by a deciduous shell, which finally disappears with
the velum.
The air-breathing mollusks, Pulmonata, are represented by
the pond-snails, Physa (Fig. 193) and Linumus (common in
ponds), and the land-snails and slugs. Fig. 200 represents a
slug suspended by a mucous thread from a twig.
The common snail, Helix albolabris Say, is a type of the
air-breathing mollusks. Fig. 196 represents this snail of
natural size, in its shell. The opening to the lung is seen
ut a, and at B are represented the heart and. lung of the gar-
den slug (Limax flavus). Fig. 197 represents Helix albo-
labris with the shell removed, and the mantle thrown back,
246
ZOOLOGY.
showing the lung and heart (h) and the mouth (m) as well
as the four tentacles, with an eye at the end of the two
upper tentacles. Fig. 198 shows the brain
and pedal ganglia of Helix albolabris. The
tentacles when carefully examined may be
found to contain both the eyes (e) with the
optic nerve (op) and the olfactory nerve
(Fig. 201, 0). Fig. 199 represents the jaw
and lingual ribbon of Helix.
The eggs of the pond-snails are laid in
Fig. 194.— Underside
of head of pond-snail, transparent capsules attached to su bmerged
be, mouth open show- , „:, „ _ . 7 , ,
ins; the buccal cavity; leaves, 6tC. TllOSC OI P/li/SCl lieterOStrOplia
j, jaw; Ij, lateral teeth; , . , . -, . -, ,1
r, lingual ribbon; t, are laid in the early spring, ana three or
four weeks later from fifty to sixty embryos
with well-formed shells may be found in the capsule.
The eggs of Limnams are laid late in the spring in
capsules containing one or two eggs, and surrounded by a
mass of jelly. After passing through the morula, gastrula,
Fig:. 195. — Mouth-parts of the Fig. 195a.— Sea-snail (Si/cott/pus)\3or-
ppnd-snail protruded, t, tongue; ing into a shell. A, mouth (»i) at rest,
ij, lateral teeth; j, jaw; ?•, rasp, or the rasp (?•) retracted ; B, mouth pressed
lingual ribbon. against a shell, ?•, the rasp gliding over
a tendon like a pulley, and filing a hole
into the shell; the arrow points into the
throat.
and trochosphere stages a definite veliger stage is finally
attained. The foot is large and bilobed, the mantle and
shell then arise, and the definite molluscan characters are
assumed, the shell, creeping foot, mantle-flap, eyes, and
tentacles appearing, and the snail hatching in about twenty
days after development begins.
Land-snails and slugs lay their eggs loose under damp
leaves and stones, and development is direct, the young
snail hatching in the form of the adult.
HELIX ALBOLABRI8.
247'
FIG. 196.
FIG. 198.
FIG. 199.
Fig. 196.— Helix albolabria, natural size. «, orifice of lung. Also the heart and
ling of Limn.r Janix, magnified.
Fig. 197.— Helix albolabrif:,vt\\\\ the phell removed to show the heart (A) and the
ling ; m, mouth.— This mid Figs. 201-204 after Leidy.
Fig. 198. — Nerve-centres of Helix albolabrvt.
Fis. 199. — Jaw (lower figure) aud side and ton view of teeth of lingual ribbon of
Selix albolabrii.
248
ZOOLOGY
The group of mollusks represented by Chiton (Fig. 202,
Chiton niber) have been referred to the worms by Jherhig.
on account of the segmented appearance
of the plated shell, and the nervous sys-
tem, which consists of two parallel
cords, connected by several commis-
sures ; * as well as from the fact that the
intestine ends at the hinder end of the
body. The young
is oval when hatch-
ed, and is a trocho-
sphere, having a
ciliated ring in the
Fig. 200.— sing. Nat- middle of the body
ural size. • , i n /», a
with a long tuit or
large cilia on the head. Afterwards
it becomes segmented, as in Fig. 203,
and is remarkably worm -like, the
limestone plates of the adult corre-
sponding to the primitive larval rings.
Certain Gastropods are useful either
as food or in the arts. In Europe
T -11 • TII n v L i r> i -n Fig. 201.— End of tentacle
Lit ton na (iftorea, the limpet (Fatella of a snail t eye ; op optic
vulgata), the whelk (Buccinum un- llurve; °> olfactory nerves'
datum), and the Koman snail (IL'li.r
]><>ini(ti(() are eaten. The sea - ear
(Haliotis) is roasted in the shell.
The animal of Cymla, Strombits gi-
<jax. Turbo, Trorltiix, and Con tot are
eaten in the tropics, while many of
the larger forms are used for 1ish-
bait. Pearls are sometimes found in
the species of Holiuti* and Ttirbo.
The beautiful shell of Cassis is made
into cameo pins, and the shell of
giyas is in the West Indies made into ornaments.
* In Fissurelln and Haliotis the two nerve-cords from the pedal gan-
glia are also iinited by nine transverse commissures, so that here also
we have an approach to the double ganglionated cord of worms.
FIG. 20i.
FIG. 203.
Fig. 202.- Chiton ruber.
Fig. 203. — Segmented larva
of Chiton.
FOSSIL GASTROPODS.
249
Various shells, such as Marginella, Tnrbinella, etc., are
strung in bracelets and armlets by savages. Cyprcea moneta,
the cowry, is used for African money, and other shells are
worked into various shapes for wampum or aboriginal money.
On the other hand, an Olivella is used by the California!!
Indians as money. Murex and Purpura afford th-e Tyriau
dye. Allied to the latter is the whelk (Buccinum undatum).
While a few Gastropods are pelagic, living upon the high
seas, such as lanthina and the Nudibranch Glaum s, most
of the species are submarine and live in all seas; the hardier,
most widely diffused species living between tide-marks, the
more delicate forms in deep water, ranging from low-water
a
Figs. 20-1-205. — The whelk; its tentacles ana proboscis exttiiUecl; «, egg-cap-
sules; 6, embryo shell. (Natural size.)
mark to fifty or one hundred fathoms. The abyssal fauna at
the depth of from 500 to about 2000 fathoms has a few char-
acteristic mollusks. Many live on land and in fresh water.
The largest, most highly colored shells live in the tropics,
while those found in the temperate zones are less beautiful,
and the arctic species are the smallest and dullest in color.
The shells of the eastern coast of North America are
divided into several assemblages, or faunae, the West Indian
or tropical shells, in some cases, reaching as far north as
Cape Hatteras ; between this point and Cape Cod a north
temperate assemblage occurs, and north of Cape Cod the
molluscan fauna is essentially Arctic ; many species being
common to the arctic and subarctic seas of the circumpolar
regions.
250 ZOOLOGY.
Marine shells in time date back to the lowest Silurian
period; such arc Maclurea, Holopea, Mni-<:hi*<juia, Pleuro-
toinvria, etc., which occur fossil in rocks of the Potsdam
period. The Palaeozoic Gastropods are few in number com-
pared with those occurring in Cretaceous and especially Ter-
tiary formations.
The earliest land-snails occurred in the Coal Period ; the
living species are exceedingly numerous, and often much re-
stricted in range, especially in the tropics ; the arctic forms
are very scarce, but four or five species occurring in Green-
land. There are over 22,000 species of Cephalophara known,
of which 7000 are fossil. There are 0500 species of Pulmo-
nata.
Subclass 4. Heteropoda. — The Heteropods form a distinct
subclass, the systematic position of which was for a long
time unsettled ; but they are now classed among the Gas-
tropods, being in fact related to the Opisthobranchiata.
Their most striking peculiarity is the form of their foot,
the anterior and middle portions of which are expanded to
form a leaf-like fin, Avhich often bears a sucker ; the pos-
terior part of the foot is much elongated, and, reaching far
backwards, appears to form a tail-like continuation of the
body. The Heteropods are more or less transparent, and
are found swimming upon the surface of the ocean, upon
their backs with their foot upwards. The shell may or may
not be developed ; when present it may be either simple or
coiled. The nervous system resembles closely that of the
true Gastropods, but is more highly developed; the brain
consists of several supraoesophageal ganglia forming part of
an cesophageal ring. From the brain arise the optic and
auditory nerves. The two large eyes lie in special capsules
near the feelers, and are movable by several muscles. The
otocysts are also large, and contain a large snhencal otolith.
The otocysts are lined by an epithelium with bundles of
long vibratile hairs, and with a cluster of sensory cells, form-
ing a macula acustica. Organs of touch have also been
described. The sensory apparatus of the Heteropods are
highly specialized, and have been studied bv Glaus, Boll,
Flemming, and others. The odontophore is well developed ;
THE IIETEROPOD JIOLLU8KX. 251
the tongue or raclnla has highly characteristic teeth, which
serve these rapacious animals to seize their prey. The in-
testine runs straight back from the month, and after mak-
ing one or two coils ends in the vent. The excretory organs
open near the anus ; the contractile tube opens internally
into the pericardia! cavity, and resembles in form and posi-
tion the excretory organ of the Pteropodn. The circula-
tion is imperfect, the blood passing from the wide sinuses
of the body to the ventricle of the heart. From the auricle
springs the aorta, Avhich subdivides into several branches
that open freely into the body-cavity. The circulation can be
easily watched, owing to the transparency of the body. The
aeration of the blood is effected partly through the skin,
partly through gills, except in a few species. The branchiae
are either thread- or leaf-like ciliated appendages, which
may either be free or enclosed in the mantle-cavity. The
sexes are distinct. The males can be readily recognized by
the large copulatory organ, which hangs free on the right
side of the body. The sexual glands fill the posterior por-
tion of the visceral cavity, and are partly imbedded in the
liver. The oviduct is complicated by the presence of an
albumen gland and a receptaculum semim*. It opens on
the right side of the body.
The Heteropods are exclusively marine, but are found in
all quarters of the world. The number of species is small,
and there are two orders only — the Plerotraclieidce with a
small or no shell and free gills, and the Atlantidce with a
large coiled shell and gills placed in the mantle. Ptero-
trachea (Firola) coronata Forsk. is found in the Mediter-
ranean, and on account of its transparency has often been
investigated. The Heieropoda live together in large num-
bers, and feed on small animals.
The eggs are laid in cylindrical strings, which soon break
up into numerous pieces. The segmentation of the yolk is
complete but irregular. The embryo rotates within the egg
during the veliger stage, when it has two distinct sails, or
lobes of the velum, and a ciliated foot with an operculum.
In this form it leaves the egg. The velum enlarges and
forms several divisions. The otocysts, eyes, and tentacles are
252 ZOOLOGY.
then developed. The foot gradually lengthens and forms the
characteristic fin or keel. The velum is meanwhile ab-
soi bed, the operculum (Carinaria), or the operculum and
shell, are thrown off, and the larva gradually assumes the
form and organization of the adult. The close relationship
of the Heteropods and Gastropods is shown by the great
similarity of their larvae. Gegenbaur even goes so far as to
include them under the Opisthobranchiata, while von Jher-
ing unites them with Chitons and some other forms under
the name of Arthrocochlidce ; for the present it seems best
to retain them as a subclass.
The fossil genus Bclleroplion is closely related to the
4-tlantidce.
CLASS II.— CEPHALOPHORA.
Mollusks with a distinct head, with tentacles, eyes and earn in the head ;
the foot, forming a creeping dink; thebody either naked uudbila.terally sym-
metrical, or enclosed in a spiral shell, and consequently behind tin1 land
asymmetrical. Mouth with pharyngeal teeth and a lingual ribbon (odon-
tophore). Nervous system consisting of three pairs of ganglia, the brain
well developed. The intestine usucdly ending near the mouth. The heart
with usually a single auricle. Breathing by a single gill, or a lung like
gill ; a double kidney, but forming a single mass. Sexes united or sepa-
rate. Young passing through a blastula, gastrula, sometimes atrocho-
sphere and usually a veliger stage ; in the land-snails development
direct.
Subclass 1. Scaphopoda. — Xo bead, several long thread-like tentacles ;
foot long, trilobed. Shell long, conical, open at each end.
A single order SolenoconchcB. (Dentalium, Siphonodenta-
15 um.)
Subclass 2. Pteropoda — Body with two wing-like expansions (velum)
on the front part of the foot, for swimming ; body naked or
shelled. Hermaphroditic. Larva with a velum and shell.
Order 1. Thecostomata (Ilyalea, Cleodora, Cavolina). Order
2. Gymnosomata. (Clione).
Subclass 3. Gastropoda. — Order 1. P rosobranchiata (Haliotis, Patella,
Trochus, Littorina, Lunatia, Paludina, Turritella, Janthina,
Cyprsea, Strombus, Cassis, Buccinum, Nassa, Purpura.)
OrderS. Opisthobranchiata. (Bulla, Aplysia, Eolis, Doris.)
Order 3. Pulmonata. (Limnaeus, Plauorbis, Auricula, Helix.
Bulimus, Limax).
GENERAL CHARACTERS OF CEPHALOPODS. 253
Subclass 4. Heteropoda. — Naked or shell-bearing mollusks, with a large
prominent head, large movable eyes, and foot with a keel-
like fin. The sexes are distinct. Respiration by gills. Or-
der 1. Pterotrncheida. — Pterotrachea, Carinaria, Firoloides.
Order 2. Atlantida. — Atlanta (living) ; Bellerophon (fossil).
Laboratory Work. — The Gastropods are very difficult to diesect, and
it is quite essential that the
specimen be freshly killed, and
that it has died as fully ex-
panded as possible. For this
purpose they should be al-
lowed, as Verrill suggests, to
die in stale sea-water, with
the parts expanded ; when the
animal is nearly dead, the soft
parts can be forcibly held out
by the hand while the animal
is killed by immersion in alco-
hol. Shells and other marine
animals may be obtained by
means of the dredge (Fi<r.
211), an iron frame with a
net, to which is attached a Fig. 206.— Dredge,
rope and weight.
CLASS TIL— CEPHALOPODA (Squids and Cuttle-fishes).
General Characters of Cephalopods. — The essential
features of this class may be observed by a study of the com-
mon squid, represented by Fig. 207. The following account
is hased on dissections of Loliyo Pealii Lesueur (Fig.
208). A general view of the body of the entire squid,
with its arms and suckers, is given in the accompanying
illustration (Fig. 207) of Lolirjo pitlldla Verrill. The body
is fish-like, pointed behind, and with two broad fleshy fin-
like expansions at the end of the body. The head is dis-
tinct from the mantle or body, and the mouth is surrounded
by a crown of ten long stout pointed arms, provided on the
inner side with two rows of alternately arranged cup-shaped
suckers, each sucker being spherical, hollow, with a horny
-254
ZOOLOGY.
rim inside. Two of the ten arms arise from the under side
of the head ; they are twice the length of the eight others,
and oval at the end. On each side of the head behind the
tentacles are the remarkably large eyes, which, though usual-
ly said to be more like the vertebrate eye than those of any
other invertebrate, are really
constructed fundamentally on
the same plan as the eye of
the snail ; differing in several
important respects from that
of a Vertebrate, the resem-
blances between the two being
superficial, while the struc-
ture of the eyes of mollnsks is
quite unlike that of Crusta-
ceans, insects or Vertebrates.
The mantle loosely invests
the front of the body next to
the head, so that the water
passes in around the neck in
order to bathe the gills, which
are quite free from the visce-
ral mass. The mantle is beau-
Dtifully colored and spotted,
the change of color being due
to the change in form of the
pigment masses or cliromato-
j>Jio7'es, which are under the
influence of the peripheral
nerves.
The mantle is supported by
Fig ydl.-LoUriopallida; male. About a homy " pell" (Fig. 209), or
pen-shaped thin support, ex-
tending from the upper side of the anterior edge of the
mantle to the end of the body. In the fr/tiit of the Medi-
terranean Sea this is thick, formed of limestone, and is
called the "cuttle-fish bone."
The organs of digestion consist of a mouth, pharynx,
oesophagus, stomach and intestine. The mouth is situated
po
FIG. 208. -Anatomy of common squid.— Drawn by J. S. Kingsley, from the author's
dissections. The brain (d ) in nature is situated above the oesophagus.
256
ZOOLOGY.
between the tentacles, and is surrounded by a double fleshy
lip, the outer fold of the lip bearing short fleshy pointed lobes
opposite the spaces between the tentacles. The
pharynx is large, muscular and bulbous, contain-
ing two powerful horny teeth, shaped like a par-
rot's beak ; the two jaws are unequal, the lower
one the smaller, moving vertically. On opening
the base of the smaller jaw, the lingual ribbon or
odontophore (Fig. 208, po) may be discovered ; it
consists of seven rows of teeth, somewhat as in
those of Architent.kift Hurtim/ii (Fig. 210).
The oesophagus (os) is long and slender, with two
long oval salivary glands (xy) on each side of it, just
behind the pharynx; the salivary duct leading
into the mouth-cavity. The oesophagus has
several internal longitudinal folds, and passes
on one side of the large liver (/) which lies in
front of the stomach, and which is about one
third as long as the whole body, extending back-
wards.
On laying open the stomach, a series of large
semicircular transverse curved valves may be
Fig. 209..- seen, occupying the anterior third of the stom-
. dofla? aca (x)> while beyond are scattered glandular
s'idz e .-" Anur masses- The pyloric end opens into an oval
Yen-in. cox-urn (ca) with about fourteen longitudinal,
thin high ridges. There is no spiral portio.n attached. The
intestine (in) is straight, thick, and passes forward, ending
in a large vent (a), the edges of
which are lobulated. The "ink- v
bag" (Fig. 208, /) can be recog- k M?
nized as a purse-like silvery sac,
filled with a dense pigment, the
sepia, which, like the Chinese. Fig. 210.— Part of lingual ribbon of
. , _ , Arcliileuthis Hartingli ; enlarged.
sepia, can be used tor drawing.
The duct is straight, and is intimately attached to the in-
testine, ending close to the vent, both the vent and open-
ing of the duct of the ink-bag being situated at the bot-
of the funnel or siphon (Fig. 208, /), which is a large
ANATOMY OF LOLIGO. 257
ehort muscular canal with a large orifice extending on
the ventral side to the base of the tentacles. Through
this siphon passes excrementitious matter as well as the ink,
and the stream of water which is forcibly ejected from the
siphon, thus propelling the squid through and sometimes
out of the water.
The two gills (Fig. 208, y), are large, long slender bodies, at-
tached by a thin membrane to the inner wall of the mantle,,
and are quite free from the visceral mass. From the bran-
chial vein arise two rows of lamellge like the teeth of a comb.
At the base of each gill is a flatted oval body, the " bran-
chial heart," or auricle (Fig 208, bh). The auricles are quite
separate from the large four-cornered flat ventricle (Fig.
208, It ), lying in front of the stomach, and which throws off an
artery from each corner, the aorta being the largest, and
passing parallel to the oesophagus, while a large vein (MHU
cava) is sent off to the gills from a circular sinus in the
head.
The nervous system is more complicated than usual in
Mollusca, and is very difficult to dissect. In Loligo Pealii the
highly concentrated nervous system is mainly contained in an
imperfect cartilaginous brain-box (eg), a slight anticipation of
the skull of the Vertebrates. The brain (supracesophageal
ganglion, Fig. 208, d) rests upon the very large optic nerves,
which dilate at the base of the eye, the latter being partially
imbedded in sockets in the brain-box. The visceral (parie-
tosplanchnic) ganglion lies beneath and a little behind the
brain, supplying the nerves for the cars (otocysts), which
are enclosed in the cartilaginous brain-box, and there is a fine
canal leading from the ears to the surface of the body, so
that, as Gegenbaur states, it is possible to distinguish a mem-
branous and a cartilaginous labyrinth, analogous to the
similar parts found in the Vertebrates. The pedal ganglion
(Fig. 208, p) is paired with the visceral ganglion (Fig. 208, ?'),
but lies in front of it, behind and under the bulbous pha-
rynx, and from it arise ten nerves (/), which are distributed one
to each arm, passing between the two rows of suckers. Two
smaller ganglia, the superior buccal and inferior bnccal, lie
one above and one below the beginning of the oesophagus.
258
ZOOLOGY.
Besides this set of five cephalic ganglia, there are three pairs
of ganglia belonging to the visceral or sympathetic nerve,
which arise from the visceral ganglion situated among the
viscera ; a single one (the ventricular or splanchnic ganglion)
is situated over the stomach near the origin of the aorta,
which sends a nerve to the coecum, and another accompanies
the aorta ; the mate to this ganglion is situated near the
vena cava. A pair of ganglia is situated on the mantle Avails
(ganglia stellata), and there are two branchial
ganglia. The kidneys (&) are irregular
branching spongy bodies, in intimate con-
nection with the auricles or branchial hearts.
The sexes are distinct. The ovary (o) is
large, especially when the eggs are ripe, and
is situated in the end of the body-cayity.
The single oviduct is as in some worms,
separate from the ovary, and in this respect
the Cephalopods approach or anticipate the
Vertebrates, in which the oviduct is also
separate from the ovary. The oviduct
(o?') is a thick straight tube, with a flaring,
deeply-lobed mouth. The eggs, when ex-
truded, are enveloped in a large gelatinous
capsule (Fig. 211), which is secreted by the
large flattened nidamental gland (c) on the
floor of the body-cavity, tied down at each
end by cord-like membranes. Usually there
f are two nidamental glands.
The earliest phase of development of the egg
of most Cephalopods (Septa, Loligo) is like that of birds and
reptiles, the yolk undergoing partial segmentation, the blasto-
derm being restricted to a small disk, as in Vertebrates. Even-
tually the blastoderm encloses the Avhole yolk, the mantle
begins to form, the eyes are at first in-pushings of the outer
germ-layer, and the mouth appears. The digestive tract
originates from a primitive imagination of the outer germ-
layer (ectoderm), as in AmpMoxus, Ascidians, worms, and
some Coslenterates. About the tenth day, as observed by
USSOAV, at Naples, the gills, siphon or funnel, and arms arise,
—After Yen-ill.
DEVELOPMENT OF CUTTLE-FISHES.
259
and a day later the rudiments of the ears, of the pharynx
and salivary glands ; while a day or two after, the ventri-
cle, auricles, the kidneys, the ink-sac, and liver develop.
Contrary to the usual rule the ganglia arise from the middle
instead of the outer germ-layer. After this the germ grad-
ually develops until it rises above the surface of the egg,
and soon the yolk is partly absorbed and is contained in a
FIG. 212.
FIG. 213.
Fig. 212.— Embryo of Loligo Pealii. a, a", a'", a"", the right arms belonging to
four pairs; c, the side of the head; e, the eye; /, the caudal fins; h, the heart; m,
the mantle in which the color-vesicles are already developed and capable of chang-
ing their colors; o, the internal cavity of the ears; s. siphon.— After Verrill.
Fig. 21.3.— The same as Fig. 212. but more advanced. The lettering in Figs. 212
and 213 the same. — Both after Verrill.
large yoke sac, as in Figs. 212, 213. Finally the young cut-
tle-fish hatches in the form indicated by Fig. 214, and then
swims free upon the surface of the sea.
The development of Cephalopocls in general is, then, di-
rect, i.e., there is no metamorphosis, the phases of meta-
morphosis seen in most other mollusks not appearing; but
in an unknown species of cuttle-fish whose eggs were found
floating on the Atlantic, the germ, after the partial segmen-
tation of the yoke, assumed a free-swimming condition (Fig.
115) before the definitive features (Fig. 116) of the cuttle-fish
2GO
ZOOLOGY.
appeared. The squids or cuttle-fish are very active, some-
times leaping out of the water and falling on the decks of
large vessels. They dart rapidly back-
^""X .(.saw** ward by ejecting the water from their
Cr~<h*\£.£~^ siphon or funnel.
The Cephalopoda are divided into
two orders, according to the number of
their gills.
Order 1. Tetrabranchiata. — This
group, in which the gills are four in
number, is represented by the Nautilus,
the sole living representative of a num-
ber of fossil forms, such as Orthoceras,
Goniatifes and Ammonites.
Nautilus pompilius Linn. (Fig. 217),
and Nautilus umbilicatulus are the
only survivors of about 1500 extinct
species of the order.
Order 2. DibrancJiiata. — The Di-
brancliiates are so called from possessing but two gills, while
the Tetrabranchiates had, as in Nautilus, numerous unarmed
tentacles ; these are now represented by ten (Decapoda). o*
Fig. 214.— Same as Fig.
213, but farther advanced.
a"
e...
FIG. 216.
Fig. 215.— Development of an unknown cuttle-fish. i\ cilia ; y, yolk ; mL, man-
tle beginning to develop.
Fi«- 216 —The same, much farther advanced, a, a', a", arms ; m, mouth ; or, fir,
gills ; f, funnel ; A, ear ; g, optic ganglion ; mt, mantle, the dotted line ending in a
chromatophore.— After Grenadier.
eight (Octopoda) arms, provided with numerous suckers. To
the ten-armed forms belong Spirula, a diminutive cuttle, with
jSELENNITES.
261
an internal coiled shell. The shells of Spirula Peronti La-
marck are rarely thrown ashore on Nan tucket ; it lives upon
Fig. 217. — Pearly Nautilus, N. potn.pll.iiiK. Seen in section showing
the chambers and siphuncle. H;iif natural size.— Prom Tenney's Zo-
ology.
the high seas. The extinct Belemnites had, like the recent
Moruteuthis Verrill, a straight conical shell, the " thunder-
Fig. 218.— Poulpe or Common Octopus of Brazilian Coast.
bolt" fossil. Allied to Loligo and Omma&trephes, are gigan-
tic cuttle-fishes which live in mid-ocean, but whose remains
ZOOLOGY.
have been found at sea, or cast ashore at Newfoundland and
the Danish coast ; or their jaws occur in the stomach of
sperm whales, as squid of all sizes form a large proportion of
the food of sperm whales, dolphins, porpoises, and other
Cetaceans provided with teeth. The largest cuttle-fish
known is Architeuthis princeps Verrill, the body of which
must be about six and a half metres (nineteen feet) in length,
and nearly two metres
(five feet, nine inches)
in circumference. The
two longer arms are 9
metres long. Architeu-
this inonacltus Steen-
strup has a body about
two metres (seven feet)
long, and the two long-
er arms seven metres
( twen ty - four feet)
long. A still larger
individual was esti-
mated by Yerrill to be
in total length about
fourteen metres (forty-
-Pr,,,,. •PQQf\ Tf ic crvma
3TV«
times thrown ashore
on the coast of Newfoundland and Labrador, and in one in-
stance attacked two men in a boat.
The Octopus (Fig. 218) and Aryonauta represent the
eight-armed forms.
Fin;. 'M9.—Ocfofrug Bairdil, natural size, rloreaiand
lateral view. Gulf of Maine.— After Verrill.
PAPER NAUTILUS. 263
Those weird, horrifying creatures, the Octopi, are very soft-
bodied, and live on shore just below or at low-water mark, or
in deeper water. They have no shell or pen. Octopus punc*
tatus Gabb expands 4£ metres (14 feet) from tip to tip of the
outstretched arms. They are brought of this size into the
markets of San Francisco, where they are eaten by Italians
and Chinese. An Indian woman at Victoria, Vancouver
Island, in 1877, was seized and drowned by an Octopus, prob-
ably of this species, while bathing on the shore. Smaller spe-
cies on cor.il reefs sometimes seize collectors or natives, and
fastening t> them with their relentless suckered arms tire
and frighten to death the hapless victim. Octopus Bairdii
Verrill (Fig. 219) inhabits the Gulf of Maine at from fifty
to one hundred fathoms.
The Argonauta, or paper nautilus, has a beautiful, delicate
shell. A. argo lives in the Mediterranean, and in deep water
70 to 100 miles off the coast of Southern New England. The
animal lives in the shell, but is not permanently attached to
it, the shell not being chambered, and holds on to the
sides by the greatly expanded terminations of two of its
arms, which secrete the shell. The males are very small, not
more than five centimetres (one inch) in length. During
the reproductive season the third left arm becomes larger
and different in form from the others, and becoming encysted
is finally detached from the body, and deposited by the male
within the mantle-cavity of the female, where the eggs in a
way unknown are fertilized by the spermatic bodies. The
free arm was supposed originally to be a parasitic worm, and
was described under the name of Hectocotylus.
The living species of Cephalopods have a wide geographi-
cal range, and a high antiquity, the earliest forms appearing
in the Lower Cambrian Period, while the type culminated in
the Triassic,Jurassic and Cretaceous Periods.
CLASS III.— CEPHALOPODA.
MoUnsks with the head-lobe divided into arms, usually provided
tuckers,- eyes more highly organized than in any other invertebrates ;
264 ZOOLOGY.
nervous ganglia much concentrated and protected by an imperjrct ctirtila-
ginous capsule ; pharynx armed, with two teeth like a parrot's beak, be~
sides an odontophore. Sexes distinct. Usually development is direct,
with no metamorphosis ; segmentation of the yolk partial, and a primi-
tive streak is present as in birds and reptiles.
Order 1. Tetrabranchiata. — With four gills. (Nautilus, living ; Or-
thoceras, Goniatites, Ammonites, extinct.)
Order 2. Dibranchiata. — With two gills. (Spirula, Belemnites, ex-
tinct, Sepia, Architeuthis, Loligo, Otnrnast re plies, Octopua
Argonauta.)
TABULAR VIEW OF THE CLASSES OF MOLLUSCA.
Cephalopoda,
Cephalophora.
Lam ellib ranch iata.
MOLLUSCA.
Laboratory Work. — The cuttles are not easy to dissect. A horizon-
tal section through the head will show the relations of the cartilaginous
capsule to the brain, optic nerves and eyes. The nervous ganglia can
only be traced after tedious dissection. To study the viscera freshly-
killed specimens are quite essential.
LITERATURE.
Mollusca in general. — Woodward : Manual of the Mollusca (Lon-
don, 1868). Lankester: Art. Mollusca in Encyclopaedia Britanuica.
Gould: Invertebrata of Massachusetts (1870). With the works of
Cuvier, Huxley, Leuckart, Kiener, Sowerby, Say, Reeve, Tryon, H.
and A. Adams, D'Orbiguy, Hancock, Biuney, Verrill, Dall, etc.
Lamellibranchiata. — Lacaze-Duthiers : treatises in Anuales des Sc.
Nat. Paris, 1854-61; i.e., Auomia (1854), Mytilus (1856); and Archives
de Zool. Exp. 1883-87; Aspergillum (1883). With essays by Bojauus,
Loveu, Peck, Mitsukuri, Brooks, Ryder, etc.
Anatomy and Development of tlie Oyster. — Brooks: Development of the
American Oyster (Studies from Biol. Lab., Johns Hopkins Univ., i.
1879); The Oyster, Baltimore, 1892. With essays by Ryder, Osborn, etc.
Cephalophora. — Essays by Brooks, Fol, Rabl, Lacaze-Duthiers
(Deutalium, 1856-57), Purpura (1859), Haliotis (1859), Vennetus (I860),
Testacella (1887), Lankester, etc.
Cephalopoda. — Owen : Memoir on the Pearly Nautilus, 1832. With
the essays of Mitller, Steenstrup, Kolliker, Grenacher, Verrill, etc.
CHAPTER VII.
BRANCH VIL— ARTHROPODA (CRUSTACEANS AND
INSECTS).
General Characters of Arthropods.— To this group be-
long those Articulates which have jointed appendages, i. e.,
antennas, jaws, maxillas (or accessory jaws), palpi, and legs
arranged in pairs, the two halves of the body thus being
more markedly symmetrical than in the lower animals. The
skin is usually hardened by the deposition of salts, carbon-
ate and phosphate of lime, and of a peculiar organic sub-
stance, called chitine. The segments (somites or arthro-
meres) composing the body are usually limited in num-
ber— twenty in the Crustaceans and eighteen in the insects —
while each arthromere is primarily divided into an upper
(tergur-a), lower (sternum), and lateral portion (plenrum).
These divisions, however, cannot be traced in the head either
of Crustaceans or insects. Moreover the head is well marked,
Avith one or two pairs of feelers or antennas, and from
two to four pairs of biting mouth-parts or jaws, and two
compound eyes ; besides the compound eyes there are simple
eyes in the insects. The germ is three-layered, and there is
usually a well-marked metamorphosis. The Arthropoda
are nearest related to the worms, certain Annelides, with
their soft-jointed appendages (tentacles as well as lateral
cirri) and well-marked head anticipating or foreshadowing
the Arthropods. On the other hand, certain low parasitic
Arthropods, as Linguatula, have been mistaken for genuine
parasitic worms. So close are the affinities of the Vermes
and Arthropods that they were by Cuvier united as a Branch
Articulata, and while the Annelides and Arthropods may
have had a common parentage, the recent progress in our
knowledge of the worms, has led naturalists to discard the
266 ZOOLOGY.
Articulata of Cuvier as a heterogeneous assemblage of
forms embracing at least three branches of the animal king-
dom, namely, the Vermes,
Tunicata, and Arthropo-
da.
The Arthropoda are di-
vided into six well-de-
fined classes, i. e., the
Crustacea with two body-
regions, the head-thorax
Fig. 220. -Shrimp, Palcemonetts vitlgaris. and abdomen (Fig. 220)
«. cephalo-thorax ; l>, abdomen. . . . , .
and breathing through
the body-walls or by external gills; the Podostomata, which
are marine and breatbe by gills, while the remaining four
classes breathe by internal air-tubes and live on land. These
are the Malacopoda, Myriopoda, Arachnida, and Insecta.
CLASS I. — CRUSTACEA (Water-fleas, Shrimps, Lobsters,
and Crabs).
General Characters of Crustaceans. — The typical forms
of this class are the craw-fish, lobster, and crab, which the
student should carefully examine as standards of comparison,
from which a general knowledge of the class, which varies
greatly in form in the different orders, may be obtained.
The following account of the lobster will serve quite as well
for the craw-fish, which abounds in the rivers and streams
of the Middle and Western States.
The body of the lobster consists of segments (somites,
arthromeres), which in the abdomen are seen to form a com-
plete ring, bearing a pair of jointed appendages, which are
inserted between the sternum and tergum, the pleurum not
being well marked in the abdominal segments. The abdo-
men consists of seven segments. One of these segments
(Fig 221 D') should be separated from the others by the stu-
dent, m order to observe the mode of insertion of the legs.
Each segment bears but a single pair of appendages, and it
Fur. 221.— External anatomy of the lobster.— After Kingsley.
268 ZOOLOGY.
is a general rule that in the Arthropods each segment bears
but a single pair of appendages. The abdominal feet are
called "swimmerets ;"' they are narrow, slender, divided at
the end into two or three lobes or portions, and are used for
swimming, as well as in the female for carrying the eggs.
The first pair are slender in the female (Fig. 221, B $> ) and not
divided, while in the male (Fig. 221, B <* ) they are much
larger, and modified to serve as intromittent organs. The
sixth segment (Fig. 221, G) bears broad paddle-like append-
ages, while the seventh segment, forming the end of the
body and called the "telson," bears no appendages. It rep-
resents mostly the terguni of the segment. Turning now to
the cephalo-thorax, we see that there are two pairs of an-
tennae, the smaller pair the most anterior ; a pair of mandi-
bles with a palpus, situated on each side of the mouth ;
two pairs of maxillae or accessory jaws, which are flat, di-
vided into lobes, and of unequal size ; three pairs of foot-jaws
(maxillipedes), which differ from the maxillae in having gills
like those on the five following pairs of legs. There are thus
thirteen pairs of cephalo-thoracic appendages, indicating that
there are thirteen corresponding segments ; these, with the
seven abdominal segments, indicate that there are twenty
segments in a typical Crustacean. By some authors the eyes
are regarded as homologues of the appendages, but in early
life they are seen to be developed on the second autennal seg-
ment, as they are in the lower Crustacea. They are simply
modified epithelial cells of the body-walls, as in the eyes of
the lower invertebrates. The ears are situated in the smaller
antennae (Fig. 221, a'}. In the second or larger antennae are
situated the openings of the ducts (Fig. 221, h) leading from
the " green glands." while the external openings of the ovi-
ducts are situated, each on one of the third pair of thoracic
feet.
It is impossible, except by counting the appendages them-
selves, to ascertain with certainty the number of segments
in the cephalo-thorax, the dorsal portion of the segments be-
ing more or less obsolete, but the carapace, or shield of the
head-thorax, may be seen, after close examination, to rep-
resent the second antennal and mandibular segments,
Fig. 221a.— Mandible of the lobster.
pal, palpus. (Natural size.)
Fig. 2216.— First maxilla of
the lobster. (Natural size.)
en/
Fig. 221c.— Second maxilla of the lobster. (Natural size.)
rlab
end.
Fig. 221d.— First maxillipede of the lobster. (Natural size.)
D.
flab
oocp
PP
Fig. 221e.— Second maxillipede of the lobster, ex, outer, end, inner, division,
with the gill and grill-paddle (flab, flabellum). B, third maxillipede; txp, coxopo-
dite; bp, basipodite; ip, ischiopodite; mp, meropodite; cp, carpopodite; pp, pro-
podite; dp, dactylopodite. [TO face page 268.1
cxp
Fig. 231/.— Third maxillipede of the lobster, end, inner, and ex, outer, division, with the gill.
Fig. 260a. — Common shore-crab, Cancer irroratus. (Natural size.)
Fig. 221;/.— Freshly-hatched lobster. (Magnified.)
[To face page 269.]
ANATOMY OF THE LOBSTER 269
and is so developed as to cover the other cephalo-thoracic
segments, thus exemplifying, in an interesting way, Audou-
in's law of the development of one segment or part of a
segment at the expense of adjoining parts or segments ; this
law, so universal in the Arthropods, as well as throughout
the animal kingdom, also applies to the appendages.
The same parts are to be found in the crab, but in a modi-
fied form, owing to the development or transfer of the weight
of the organization headwards ; in other words, the crab is
more cephalized than the lobster ; this is seen in the small
abdomen folded under the large, broad cephalo-thorax, and
in the greater concentration headwards of the nervous sys-
tem of the crab.
To study the internal structure of the lobster, the dorsal
surface of the carapace and of each abdominal segment
should be removed ; in so doing the hypodermis or soft inner
layer of the integument is disclosed ; it is usually filled with
red pigment cells. The dorsal vessel, or heart, lies under
the hypodermis of the carapace, this being an irregular
hexagonal mass surrounded by a thin membrane (pericar-
dium) with six valvular openings for the ingress of the
venous blood. The colorless, corpusculated blood is pumped
by the heart backwards and forwards through three anterior
arteries, one median and two lateral, the median artery pass-
ing towards the head over the large stomach, and the two
lateral, or hepatic arteries, passing to the liver and stom-
ach. From the posterior angle of the heart arise two
arteries ; the upper, a large median artery (the superior ab-
dominal), passes along the back to the end of the abdomen,
sending off at intervals pairs of small arteries to the large
masses of muscles filling the abdominal cavity ; the lower is
the second or sternal artery, which connects with one extend-
ing along the floor of the body near the thoracic ganglia
of the nervous cord. The arteries become, at least in the
liver, finely subdivided, forming a mass of capillaries. There
are no veins such as are present in the Vertebrates, but a series
of venous channels or sinuses, through which the blood re-
turns to the heart. There is a large vein in the middle of the
ventral side of the body.
270 ZOOLOGY.
The blood is driven by the heart through the arteries, and
a large part of it, forced into the capillaries, is collected by
the ventral venous sinus, and thence passing through the
gills, where it is oxygenated, returns to the heart.
The gills are appendages of the three pairs of maxilli-
pedes and the five pairs of feet, and are contained in a
chamber formed by the carapace ; the sea-water passing into
the cavity between the body and the free edge of the cara-
pace is afterwards scooped out through a large opening or
passage on each side of the head, by a membranous append-
age of the leg, called the " gill-paddle" (Scaphognathite).
The digestive system consists of a mouth, opening between
the mandibles, an oesophagus, a large, membranous stomach,
with very large teeth for crushing the food within the large
or cardiac portion, while the posterior or pyloric end forms
a strainer through which the food presses into the long,
straight intestine, which ends in the telson. The liver is
very large, dark green, with two ducts emptying on each side
into the junction of the stomach with the intestine.
The nervous system consists of a brain situated directly
under the base of the rostrum (supraoesophageal ganglion),
from which a pair of optic nerves go to the two eyes, and a
pair to each of the four antennae. The mouth -parts are
supplied with nerves from the infraoesophageal ganglion,
which, with the rest of the nervous system, lies in a lower
plane than the brain. There are behind these two ganglia
eleven others ; the cephalo-thoracic portion of the cord is
protected above by a framework of solid processes, which
forms, as it were, a "false-bottom" to the cephalo-thorax ;
this has to be carefully removed before the nervous cord can
be laid bare. A sympathetic nerve passes around each side
of the oesophagus and distributes branches to the stomach.
The nerves of special sense are the optic and auditory
nerves. The eyes are compound, namely, composed of many
simple eyes, each consisting of a cornea and cnjxtaUine
cone, connected behind with a long, slender connective rod,
uniting the cone with a spindle-shaped body resting on or
against an expansion of a fibre of the optic nerve, and is
ensheathed by a retina or black pigment mass (Fig. 221 s\
flab
A.— Maxilla of lobster with its flve lobes (1-5) corresponding to the endites of the Phyllopod
thoracic limb.
B.— Section through the thorax of Apus. en, 1-6, the six endites; ex, exopodal or respira-
tory portion of the limb; c, carapace; ht, heart: m£, intestine; ng, ganglion.
C D
-lit
int
C.— Partly diagrammatic section through the thorax of Nebalia. en, the axial-jointed
endopodite; ex, exital portion or gill (above irregularly dotted) and flabellum below with rows
of dots; c, carapace.
D.— Actual section through the abdomen of Limulus; c, carapace; ht, heart; int, intestine;
ng, ganglia (lettering being the same as in C); en, axial- jointed endopodite; ex, exital or
respiratory portion bearing the gill-lamellae; the outer division (ex) homologous with the
exopodal portion of the phyllopod and phyllocaridan appendage.
HOMOLOG1ES OF THE CRUSTACEAN AND LIMULUS LIMBS.
[To face page 270.]
ANATOMY OF THE LOBSTER. 271
Though as many images may be formed in each eye as there
are distinct crystalline cones, yet, as in man with his two
eyes, the effect upon the lobster's mind is probably that of
a single image.
The lobster's ears, are seated in the base of the smaller or
first antennae ; they may be detected by a clear, oval space
on the upper side ; on laying this open, a large capsule will
be discovered ; inside of this capsule is a projecting ridge
covered with fine hairs, each of which contains a minute
branch of the auditory nerve. The sac is filled with water,
in which are suspended grains of sand which find their way
into the capsule. A wave of sound disturbs the grains of
sand, the vibrations affect the sensitive hairs, and thus the
impression of a sound is telegraphed along the main audi-
tory nerve to the brain.
Organs of touch are the fine hairs fringing the mouth-
parts and legs. The seat of the sense of smell in the Crus-
tacea is not yet known, but it must be well developed, as
nearly all Crustacea are scavengers, living on decaying mat-
ter. Crabs also have the power of finding their way back to
their original habitat when carried off even for several miles.
The two large so-called "green glands" situated on each
side within the head-thorax, and having an outlet at the
base of each of the larger antennae, are probably renal in
their functions, corresponding to the kidneys of the verte-
brate animals. The shell glands are of the same nature.
The ovaries and corresponding male glands, are volumi-
nous organs, the testes being white, and the ovaries, when the
lobster is about to spawn, being highly colored, usually pale
green, and the ovarian eggs are quite distinct. The lobster
spawns from March till November ; the young are hatched
with much of the form of the adult, not passing through a
metamorphosis, as in most shrimps and ci'abs. They swim
near the surface until about one inch long, when they re-
main at or near the bottom.
The lobster probably moults but once annually, during the
warmer part of the year, after having nearly attained its
maturity, and when about to moult, or cast its tegument, the
carapace splits from its hind edge as far as the base of the
27:i ZOOLOGY.
rostrum or beak, where it is too solid to separate. The lobster
then draws its body out of the rent in the anterior part of
the carapace. The claw — at this time soft, fleshy, and very
watery — is drawn out through the basal joint, without any
split in the old crust. In moulting, the stomach, with the
solid teeth in the cardiac portion, is cast off with the old in-
tegument ; why the stomach can thus be rejected is explained
by the fact that the mouth, oesophagus, and stomach are con-
tinuous in early embryonic life with the epithelium forming
the outer germ-layer, the mouth and anterior part of the
alimentary canal being the result of an imagination of the
-ectoderm. The old skin is originally loosened and pushed
away from the hypodermis, or under-layer, by the growth of
temporary stiff hairs, which disappear after the skin is cast ;
the hairs, however, at least in the craw-fish, do not occur on
the line of the facetted cornea, on the eye-stalk, or on the
inner lamellae of the fold of the carapace over the gill-
opening.
The Crustacea first appeared, so far as the geological record
shows, during the Cambrian period, as the remains of a Hy-
menocaris occur in the Lingula flags with those of Trilobites.
This is a Phyllocaridan, an order which characterizes the
Palasozoic age. In the Cambrian period also flourished
Ostracods, while barnacles date from the Upper Silurian
period. The oldest Phyllopod Crustacean is an Estheria of
the Devonian period, at which time also appeared the first
shrimp. In the Carboniferous period appeared the Gam-
psoiii/r/n'dce, a family of Schizopod shrimps, represented in
the United States by Pahpncarix ti/j.u/x; also a family of true
shrimps, the Anthracaridce, represented by AnthrapalcBmon.
During this period also lived the Syncaridu, a group connect-
ing the sessile-eyed and stalk-eyed Crustacea, i.e., the Iso-
pods and Decapods. The Isopods appeared in the Devonian
period, while thegenuine crabs appeared in the Jurassic period.
Order 1. Cirripedia.*—T\\e barnacles would , at a first glance,
liardly be regarded as Crustacea at all, and were regarded
as Mollusca, until, in lN3f>, Thompson found that the
young barnacle was like the larva? of other low Crustacea
(Copepoda). The barnacle is, as in the common sessile form
* The Phyllopoda are perhaps the earliest, most generalized group.
See p. 305.
ANATOMY OF THE BARNACLE.
273
Fig. 222.— A barnacle. Balanus
., porcatus. Natural size.
(Fig. 222), a shell-like animal, the shell composed of several
pieces, with a multivalvc, conical movable lid, having an
opening through which several pairs of long, many-joint-
ed, hairy appendages are thrust,
thus creating a current which sets
in towards the mouth. The com-
mon barnacle (Balanus balanoi-
des Stimpson) abounds on every
rocky shore from extreme high-
water mark to deep water, and
the student can, by putting a
group of them in sea-water, ob-
serve the opening and shutting
of the valves and the movements
of the appendages or "cirri.
The structure of the barnacle may best be observed in
dissecting a goose barnacle (Lepas fascicularis Ellis and
Solander, Fig. 223). This barnacle consists of a body (capit-
ulum) and leathery peduncle. There are six pairs of jointed
feet, representing the feet of the Cycles (Fig. 231). The
mouth, with the upper lip mandibles (B, 1), and two pairs
of maxillae, will be found in the middle of the shell. A
short oesophagus (according to J. S. Kingsley, whose ac-
count we are using) leads to a pouch-like stomach and tubular
intestine. This form, like most barnacles, is hermaphroditic,
the ovary (A, o)lying at the bottom of the shell, or in the
peclunculated forms in the base of the peduncle, while the
male gland (t) is either close to or some distance from the
ovary. There is also at the base of the shell, or in the pe-
duncle when developed, a cement-gland, the secretion of
which is for the purpose of attaching the barnacle to some
rock or weed.
While the sexes are generally united in the same indi-
vidual, ir the genera INa (Fig. 224) and Scalpellum (Figs.
225, 226, besides the normal hermaphroditic form, there
are females, and also males called "complementary males,"
which are attached parasitically both to the females and
the hermaphroditic forms, living just within the valves or
fastened to the membranes of the body. These comple-
274
ZOOLOGY.
mental males are degraded, imperfect forms, with sometimes
no mouth or digestive canal. The apparent design in nature
of their different sexual forms is to effect cross fertilization.
The eggs pass from the ovaries into the body-cavity, where
Fig. 223.— Anatomy of Ltpas fascicularis. A. c, six pairs of legs or cirri ; /. flla,
mentary appendages; m, mouth ; s, siomach ; h, openings of the liver (/) into the
stomach, which is represented as laid open ; i, intestine ; a, vent ; t, testis ; v, vasa
deferentia, one cut off; p, male appendage ; o, ovary ; e, adductor muscle connecting
the two basal valves ; vs, scutal valve ; vc, carinal valve ; vt, tergal valve. Enlarged
twice.
B. 1. palpus ; 2, mandibles ; 3 and 4, first and second maxillae.
C. Nervous system, s, brain, sending the optic nerves to the rudimentary eye («),
each optic nerve Having an enlargement near the eye, i. e., the ophthalmic ganglion (oj;
between o and a are the nerves which go to the peduncle ; a, nerve sent to the ad-
ductor scutorum ; a?, commissure between the supra- and infraresophageal ganglia (n) ;
C, c, c, c, c, C, nerves to each of the six feet. Enlarged four times.— After Kingsley.
they are fertilized, and remain for some time. They pass
through a morula condition, a suppressed gastrula or two-
layered state, and hatch in a form called a Nauplius, from
the fact that the free-swimming larva of the Entomostraca
EMBRYOLOGY OF BARNACLES.
275
was at first thought to be an adult Crustacean, and described
under the name of Nauplius. The Nauplius
of the genuine barnacles (Fig. 227) has three
pairs of legs ending in long bristles, with a
single eye, and a pair of antennas, the body
ending in front in two horns, and posteriorly
in a long caudal spine. After swimming
about for a while, the Nauplius attaches it-
self to some object by its antennae, and now a
strange transformation results. The body is
enclosed by two sets of valves, appearing as if
bivalved, like a Cypris (Fig. 228) ; the peduncle grows out,
Fig. 226. — Comple-
mentary male of Seal'
pellum regium, greatly
enlarged. —After Wy-
vLUe-Thompson.
Fig 235.— Scalvelliun regium. a, complementary
male, lodged within the valves. — After Wyville-
Thompson.
27G
ZOOLOGY.
concealing the rudimentary antennae, and the feet grow
smaller, and eventually the barnacle-shape is attained. The
Fig. -£M.— Pupa of Lepas, much eu-
hirged. — After Durwm.
Fig. 227.—Nauplius of Balanus bat-
anoides, much enlarged.
common barnacle (Balanus balanoides) attains its full size,
after becoming fixed, in one season, i. e., between the first of
April and November.
Still lower than the genu-
ine barnacles are the root-bar-
nacles or Rliizocepliala, repre-
sented by Peltogaster (Fig.
229) and Saccnlina (Fig. 230),
in which the young is a more
simple Nauplius form, like
the young of the Entomostra-
ca, while the adult is a sim-
ple sac, with a ganglion, but
no digestive organs. From
the feet of the young grow
out, after the animal becomes
sessile, long root - like fila-
ments, which ramify in the
body of the crab, to which
these animals are firmly an-
• Fig. 229. — Peltogaster curvatn*, en-
We Can Conceive Ot largedlj times, beneath the larva or N;m-
plius of Parthenopea, enlarged al>out ^op
times.— From Brehm's Thierleben.
, ,
no lower, more degraded
tacean than these root-barna-
cles, the only signs of life being the powerful contractions
of the roots and an alternate expansion and contraction of
ENTOMOSTRACA.
27?
the body, forcing the water into the brood-cavity, and again
expelling it through a wide orifice. These root-barnacles
recall the Trematode worms, though the
latter are much more highly organized.
An allied form (CryptopJiialus minutnz)
undergoes the larval or Nauplius stage
in the egg, hatching in the pupa condi-
tion, while another form (a species of
Peltog aster 9) also leaves the egg in the
"Brehm's pupa form.
Order 2. Entomostraca (Water-fleas).
— The type of this group is Cyclops (Fig. 231, C. serru-
latus F. see also Fig. 232) in which the body is pear-
shaped, with a single bright eye in
the middle of the head ; two pairs
of antennae, used for swimming as
well as sense-organs ; biting mouth-
parts, and with short legs. The
sexes are distinct, the females swim-
ming about with two egg-masses h
attached to the base of the ab-
domen. The young is a Nauplius,
much like that represented in Fig.
229, the mouth-organs, the legs
and abdominal segments arising eg
after successive moults, until the
adult form is attained. Allied to
Cyclops is Canthocamptus caver-
narum Packard (Fig. 233), an eyed
species, living in Willie's Spring, in
Mammoth Cave.
Many Entomostraca are parasitic,
and consequently undergo a retro-
grade development, losing the
jointed structure of the body, the
appendages being more or less
aborted, while the body increases
greatly in size. Such are the fish-lice, represented by the
Lcrncea of the cod.
. ssi.— 6y«<&». «, eye, A
heart : W' e£S8 ; /, feet.-Af tei
278
ZOOLOGY.
oe
Fis. ~'32.— Intesiin<> and testis (t) of a copepod
(Plevroma), ^irle view «, cesophagus ; t>, stomach ;
h, blind sac leadiiiir from the stomach ; i, intes-
tine; c, hean ; mi, coiied vas deferuns.— After Clans,
from Gegenbaur.
In Lerneonema radiata Steenstrup and Lutken (Fig. 234),
we find the lowest term in the series of degradational forms
of this order. The
/• mouth-parts are here
converted into five
roots, radiating from
the head ; the body
is not segmented, and
ends in two long egg-
masses.
In Penella (Fig.
236) the body is cord-
like, buried in the
flesh of the sun-fish or sword-fish, etc., the females having
two long, string-like
egg-sacs. The speci-
men figured was taken
from a sword-fish off
Portland, Maine.
In Lcrncea branchia-
lis Linn, of the gills of
the cod, the body is
thicker, the root-like
appendages grow deep
into the flesh of its
host, like twisted and
gnarled roots, while the
shapeless sac-like body
is filled with eggs.
In Adheres, we as-
cend a step higher in
the perfection of or-
gans ; the creature is
attached by a pair of
, . i ., Fig. 233.— Cantkocamplus caver- Fig. 334.—
jaWS WillCil lllllte tO narum of Mammoth Cave, much Fish -louse of
P i j i enlarged. the Menhaden.
form a sucker, the an- twice enlarged!
tennae are present, though rudimentary, while — AfterVern11-
the abdomen is faintly segmented. A. Carpenter i Packard
(Fig. 235) lives on the trout in Colorado.
CLADOCERA.
279
The highest members of the group of sucking Entomo-
stnica are Cdligus and Argulus, in which the body is seg-
mented, with antenna and free
mouth-parts and legs ; the latter
genus with compound eyes. Cali-
gus curt u * M tiller lives on the cod,
and Argulus alosce Gould on the
alewife.
Order 3. Brancliiopoda. - - This
order includes such Crustacea as I
in the higher forms breathe by I
rather broad feet. There is a con-
siderable range of
form from the
Ostracoda, repre-
sented by Cypri*,
in which the feet Fig 235._Actheres of the trout
are much as in Cy-
clops, through Daplinia and Sida (Fig 237)
which represent the Cladocera, up to the
Phyllopods. The suborder of Ostracoda
(Cypris) arebivalved, the shell often thick.
They have two eyes, two pairs of antennae,
a pair of mandibles with a jointed feeler
(palpus) and a gill, and four pairs of feet,
the second pair often carrying a small gill.
The shells of certain species allied to Cyprlx
abound in the lowest Silurian strata. The
species live in fresh-water pools and in the
ocean at various depths. They undergo no
metamorphosis, the youngest stage being a
shelled Nauplius.
The suborder Cladocera is represented by
fresh and salt-water species. The higher
forms are Sida and Daplinia. They are
called water-fleas from their jerky motions.
The eggs of Daplinia are borne about by
sac.— Peneiia of the females in so-called brood-cavities on
the sword-fish, female. the back under the ghell> There are twQ
sorts of eggs, i. e., the "summer" eggs, which are laid by
ZOOLOGY.
asexual females, the males not appearing until the autumn,
when the females lay the fertilized "winter" eggs, which are
surrounded by a very tough shell. Dohrn observed the de-
velopment of the embryo in the summer eggs. At first the
embryo has but three pairs of appendages, representing the
antennas and one pair of jaws. It is thus comparable with
the Nauplius of the Copepodous Entomostraoa, and thus the
e
Fig. 237.— Sida. e, egg in brood-sac.
Cladocera may be said to pass through a Nauplius stage in
the egg.
Afterwards more limbs grow out, until finally the embryo
(s provided with the full number of adult limbs, and hatches
in the form of the mature animal, undergoing no farther
change of form.
The members of the suborder Phyllopoda are more highly
developed than any of the Crustacea mentioned, though, like
the Ostracodes and Cladocera, the body is usually partly
covered by a large carapace (the mandibular segment greatly
developed), which is sometimes bent down, and opens and
shuts by an adductor muscle, so that they resemble bivalve
PHTLLOPODA.
281
Mollusca But they are especially characterized by the
Ciroad leaf-like feet, subdivided into lobes, and adapted for
breathing as well as
for swimming The
thorax merges insens-
ibly into the abdomen.
The number of body-
segments varies great-
ly, there being six-
teen in Limnetis, the
simplest form, and
sixty -nine in Apus,
or three times the
number present in the
lobster, the segments Fig. %®,.-Limnetis GmiaU, much enlarged.— After
thus being irrelatively
repeated, a sign of inferiority. There is a pair of simple
eyes consolidated into one as in Limnetis and Limnadia, or
as in Apus, there is a
pair of compound eyes,
situated in the cara-
pace, apparently on
one of the antennal
segments. In Bran-
cliipus and Artemia
the compound eyes
are stalked, an antic-
ipation of the stalked
eye of the lobster,
etc., but the eye, it
should be noticed, is not developed from a separate
segment, but from one of the two antennal segments. All
the members of this order hatch in the Nauplius form, the
three pairs of appendages of the larva, representing the two
pairs of antenna? and the mandibles of the adult. The spe-
cies live in pools of fresh water liable to dry up in summer ;
they lay eggs which drop to the bottom, and show great vi-
tality, withstanding the heat and dryness after the water
has evaporated ; the young hatching after the rains refill the
pools or ditches.
Fig. 839.— Limnadia Agassizii, enlarged.
282
ZOOLOGY.
ria
mis. a. hand
end of body.
This suborder presents a beautiful series of increasingly
complex forms, as Ave ascend from Limnetis to BrancJiipus.
In Limnetis the bivalve shell encloses the ani-
mal, and is the size of a small flattened pea.
There are from ten to tAvelve feet -bearing
segments. L. Gouldii Ilaird (Fig. 238) is very
rare in Canada and NCAV England. The shell
of Limnadia is thin, oval, and there are from
eighteen to twenty-six feet-bearing segments.
L. (Enlvmnadia) Agassizii Packard (Fig. 239)
inhabits small pools in Southern NCAV En-
gland. The shell of Estheria (Fig. 241, Es-
^""^""^ theria Belfragei Packard) is sometimes mis-
leg of male Esthe- taken for that of the fresh -water mollusks
Cyclas and Pisidium. The males of the fore-
going genera have the first pair of feet modi-
fied to form large claspers (Fig. 240).
In Apus the abdomen projects beyond the large carapace,
and ends in two long many-jointed appendages. There are
about sixty pairs of feet, each foot
divided into several leaf -like lobes,
wherein respiration is carried on.
These Phyllopods usually swim upon
their backs, as in the species of Bran-
cliipus. The females chiefly differ
from the males in the presence of an
orbicular egg-sac on the eleventh pair
of feet, the sac being a modification of
two of the lobes of the feet, and containing but a fe\v eggs.
Aj)us cequalis Packard (Fig. 242, Fig. 244 A, represents the
larva of a European Apus) inhabits pools in the western
plains. Lepidurux differs from Apus in having the telson
spoon-shaped instead of square. L. Couesii Packard (Fig.
243) occurs on the Rocky Mountain plateau in Utah and
Montana. It is an interesting fact in zoo-geography that
there are no species of Apus and Lepiilnmx cast of the west-
ern plains. Apus has been found by Siebold to reproduce
parthenogeneticall v.
The various species of Branohipus and Art cm in have no
Fig. 241.— Shell oiEsthtna
Belfragei, enlarged three
times.
PHYLLOPOD CRUSTACEANS.
283
carapace, the mandibular segment being small and not over-
lapping the segments behind it. The second antenna* are
Fig. 243.—Lepid//r>is Couesii.
side and dorsal view, natural
size.
Fig. 242.— Apus cequalis, natural size.
large and in the male adapted for
clasping. In Thamnocephalus (Fig.
245, T. Irachyurus Packard, from
Kansas) there is a singular shrub-
like projection of the front of the
head, and the abdomen is spatulate
or spoon-shaped at the end. Bran-
chinectes Coloradensis Pack. (Fig.
246) is a Rocky Mountain form. Fig. 844.-a, Larva of
' J . cnformis. — After Zaddacb. ft,
The brine - shrimp, Artemia, lives Naupliusof Artemia salina oi^a-
i • i • j.i ij. rope-
only in brine-vats or in the salt
lakes of the West and of Southern Europe. Artemia yra-
cilis Verrill (Fig. 247) has thus far only been found in tubs
284
ZOOLOGY.
of concentrated salt water on railroad bridges in New En-
gland. Artemia fertilis Verrill abounds iu Great Salt Lake.
he
Fig. 245.— Thamnocephalus platy urn*, male, natural six.e. side and front view, o,
;ad of the female ; 6, end of the body of the I emale, showing the ovisac.
They may often be seen swimming about in pairs, as in
Fig. 248. This species has a Nauplius young like that of
Fig. 2l§.—Bmnchinectes Colorademis Pack.
the brine-shrimp of Europe (Fig. 244 b). It is a signifi-
cant fact, bearing on the question of the origin of species,
that, according to Schmankiewitsch, Aiii'inia may change its
T-KTltA DECAPODS.
285
form, the change being induced by the greater or less saltnesa
of the water. Art cm in produces young by budding (parthe-
nogenesis) as well as from eggs.
A species observed near Odessa
produced females alone in warm
weather ; and only in water of
medium strengtn were males
produced. The eggs of Arte-
mia fer tills have been sent in
moist mud from Utah to Mu-
nich, Germany, and specimens
raised from the eggs by Siebold,
proving the great vitality of the
eggs of these Phyllopods, a fact
paralleled by the similar vitality
of the eggs of the king-crab.
Fig. 244 b represents the Nau-
plins of the European brine-
shrimp.
Order 4. — Edriophtltalma.—
To this order belong the sow-
bugs (Tsopoda) and the beach-
fleas (Alltplupoda). In these ^raci&) enlarged .«, first antenna; 6,
Pvnaf'ipp'i thorp i<? Tin PPlYh-iln- second antenna or chtsper ; c, stalked
eye : rf, e, jaws ; /, a foot ; g, egg-sac.
thorax, but the head is small, —After Verriii.
bearing two pairs of antennas, and a pair of jaws, and three
pairs of maxilla?. The thorax is continuous with the abdo-
men. Kespiration is performed by lamellate or leaf-like
gills on the middle feet in the Amphipods, or on the hinder
abdominal feet in
the Isopods. The
lowest Isopods are
parasitic, they
Tig.248.—Arfemiaferlilifi from Great Salt Lake, e, rrrnduite into the
egg-sac ; c, male clampers.
Amphipods, and
the higher Amphipods are connected with the shrimps (De-
capoda) through a group (probably a suborder) of synthetic
forms (P'alwocaris, Acanthotehon and Gampsonyx, Fig.
249) such as are found in the coal formation of Illinois
Fig. 247.— Brine- shrimp,
gracuis, enlarged.
ci nia
28G
ZOOLOGY.
and Europe, which we have called Syncarida, and
which have antennae and tails like shrimps, but the body
Fig.
size.
.— Gant2>sonyxfimbna(us of European coal measures, 2l/2 times natural
and limbs like Amphipods. In the Isopods the body is flat-
tened and the head rather broad.
Fig. 251 is a dorsal view of Serolis Gau-
dichaudi Audouin and Edwards, with the
two pairs of antenna? and pointed sides of
each thoracic segment, dissected to show the
nervous system, the two pairs of antennal
nerves ; the optic nerves (op) sent to the
compound eyes. Fig. 252 represents a trans-
verse section of the body, showing the mode
of insertion of the legs, and the equality in
the tergal and sternal sides of the body.
Fig. 254 represents a gill. In the common
pill-bug (Porcellio) aerial respiration is per-
formed by respiratory cavities situated in
the abdomen. In Tylos similar cavities are
filled with a multitude of branching coeca,
serving for aerial respiration, thus antici-
pating the tracheary system of insects.
The nervous system is quite simple. (Fig.
250, Idotcpci. and Fig. 251, that of Scrolls.)
The digestive canal is straight, consisting
Fig. 250.— Nervous of a short oesophagus, a membranous stom-
%m "-Utfb/j: ach, and usually a short tubular intestine ;
i. Kinsley. ^e j|yer consisting of several short coeca.
In Serolis Gaudicliaudi the stomach is somewhat pear-
EMBRYOLOGY OF ONISGUS. 28?
shaped, widest behind, extending a little behind the middle
of the body. The intestine is about one half as wide as
the stomach. Certain Isopods possess segmental organs.
Fig. 251.— Dissection of Serolis to show the nervous system.— Dissected and drawn
by J. S. Kingsley.
There is no ccecal enlargement, and no "urinary" tubes.
The sexes are distinct. The young are hatched in the form
of the adult, there being no metamorphosis.
The development, of the pill-bug, Oniscus murarius, is
probably typical of that of most Tetradecapods and Deca-
Fig. 252.— Transverse section of Serolis. t, t, tergum ; s, $. sternum ; em, epime-
rum ; es, episternum, at insertion of the legs.— Prepared and drawn by J. S. Kings-
ley.
pods (Bobretzky). The first change after fertilization is the
origin of the formative or primitive blastodermic cells at one
288
ZOOLOG Y.
Fig. 253.—
Moutn-parts of
Serolis. m, man-
dible ; nix', first
maxilla ; mx
pole of the egg. This single cell subdivides, its products
forming the " blastodermic disk" or outer germ-layer, the
segmentation of the yolk being partial. The
third (innermost) and middle germ-layers next
arise (the same processes go on in certain
shrimps, viz. : Crangon and Palcemoii). The
intestine is formed by an in -pushing of the
outer germ -layer. The limbs now bud out, the-
result of the pushing out of the outer germ-
layer (ectoderm). The nervous cord arises from
the ectoderm ; the large intestine originates in
the yolk-sac, its epithelium first
appearing in the liver-sac. The
heart is the last to be formed. Ex-
ternally the antennae in Oniscus
and also Asellus are the first to bud
out ; the remaining appendages of
the head and thorax arise contem-
poraneously, and subsequently the
abdominal feet. The abdomen in
the Isopods is curved upwards and
backwards, while in the embryo Amphipods it is bent be-
neath the body.
The development of the Amphipods or beach-fleas is
nearly identical with that of the Isopods. The eggs of cer-
tain species undergo total segmentation, while those of other
species of the same genus (Gammarus) partially segment, as
in the spiders, and in a less degree the insects.
Standing next below Cymothoa, which is of the general
Isopod shape, but which lives parasitically on the tongue
and other parts of fishes, but which from their parasitic
habits become slightly changed in form, the females espe-
cially, sometimes becoming blind, is the family of which
Bopyrus is a representative. The females (Fig. 257) are par-
asitic under the carapace of various shrimps. In />'. pftlcemon-
eticnla Packard, the females are many times larger than
the males ; the ventral side of the body is partly aborted,
having been absorbed by its pressure against the carapace
of its host, which is swollen over it ; it retains its position by
paipus.— Drawn
by J. S. Kings-
ley.
1SOPODA.
289
FIG. 257.
Pig 255.— Section of the embryo pill-hug, d, intestine; ?, epithelium form-
in? the walls of th- two lobes of the liver ; ff, transverse section of the nervous cord ;
h, walls of the body.— After Bobretzky.
FiL'. 256.— Section of more advanced emhryo pill-bus, h, heart ; /i/i, hypoder-
nial layer or body-walls ; m, muscular wall of the intestine : e, epithelial lining of the
intestine; p, dividing cell-wall between the heart and intestine; I, two lobes of the
liver ; c/, ganglion, the clear space being filled with the fine granular substance of the
ganglion.— After Bobretzky.
FIST. 257,—Bopyrus. A, ventral, B, dorsal side of the female: (\ lateral and D,
dorsal view ol the male ; c1, head and first thoracic segment ; c2, autunnie -all en-
.— Packard, del.
290 ZOOLOGY.
the sharp hook-like legs around the margin of the body. The
head has no eyes nor appendages. The male (Fig. 257, 0, D)
is but slightly modified, is very minute, and is lodged partly
out of sight under the ventral plates of the female, whose
body is about five millimetres (a fifth of an inch) in length*
Fig. SS&.—Arcturus £ciffi/d, w.tu its young clinging to its antennje.— After Wyvillfr
Thompson.
Various species of Porcellio (sow-bugs) live under stones
on land ; and allied to Asellus, the water sow-bug, is the
marine Limnoria lignoruni White, which is very injurious
to the piles of bridges, wharves, and any submerged wood.
The highest Isopods are Idotcea, of which /. irroratus Say
(Fig. 250) is our most abundant species, being common in
eel-grass, etc.. between and just below tide-marks ; and Arc-
turns (Fig. 258, A. Baffini Sabine), from the Arctic seas.
PH7LLOCARIDA.
291
The series of Amphipods begins with Cyamus ceti (Linn.),
the whale-louse, passes into Caprella, with its linear body
and spider-like legs, to Hyper ia, which lives as a mess-mate
of the jelly-fish, Cyanea, and culminates in the water-flea
(Gammam* oniatus Edwards) and sand-flea (Orchestia agilis
Smith), abundant and leaping in all directions from under
dried sea-weed at high-water mark.
Fig. 259.— Nebalia bipcs. Enlarged 6 times.
Order 5. Phyllocanda. — This name is proposed for a
group of Crustacea, the forerunner of the Decapoda and
hitherto regarded as simply a family (Nebaliadce), in which
there is an interesting combination of Copepod, Phyllopod,
and Decapod characters, with others quite peculiar to them-
selves. The type is an instance of a generalized one, and is
very ancient, having been ushered in during the earliest Si-
lurian period, when there were (for Crustacea) gigantic forms
(Dithyrocaris was over one foot in length) compared with
those living at the present day. The order connects the
Decapods with the Phyllopods and lower orders. The mod-
ern Nebalia is small, about a centimetre (.40-. 50 inch) in
length, with the body compressed, four of the abdominal
segments projecting beyond the carapace, the last abdominal
segment bearing two large spines. There is a large rostrum
overhanging the head ; stalked eyes, and two pairs of anten-
nas, the second pair nearly as long as the body and many-
jointed. The mandibles are succeeded by two pairs of max-
ZOO LOOT.
illse. Behind these mouth-parts are eight pairs of short, leaf-
like respiratory feet, which do not project beyond the edge of
the carapace. These are succeeded by four pairs of large,
long swimming feet, and there are two additional pairs of
small abdominal feet. There is no metamorphosis, develop-
ment being direct, the young hatching in the form of the
adult. Of the fossil forms, Hymenocaris was regarded by
Halter as the more generalized type. The genera Peltocaris
and Divchiocaris characterize the Lower Silurian period ;
Ceratiocaris the upper ; Didyocaris the Upper Silurian and
Lowest Devonian strata ; Ditliyrocaris and Argus the Car-
boniferous period. Our northeastern and arctic species is
Nebalia Hpes (Fabricius), which occurs from Maine to Green-
land.
Order 6. Thoracostraca. — In the Stomapods, represented
by Squilla, the gills are attached to the base of the hinder ab-
dominal feet. Squilla lives in holes below low-water mark.
The suborder Decapoda (Shrimps, Lobster). — A general
knowledge of the Crustacea representing this, the high-
est group of the class, may be obtained by a study of
the craw-fish and lobster. All Decapods have twenty seg-
ments in the body, a carapace covering the thorax and con-
cealing the gills, which are highly specialized and attached
to the maxillipedes and to the legs ; usually a pair of stalked
eyes, two unequal pairs of antennae,, the hinder pair the
larger and longer ; a pair of mandibles, often provided with
a palpus, two pairs of lobed max ills?, three pairs of maxilli-
pedes, while the name of the order is derived from the fact
that there are five pairs of well-marked legs, or ten in all.
To the abdomen are appended six pairs of swimming feet,
called "swimmerets." Another distinctive characteristic of
most, in fact all the higher Decapods, is the short, or five
or six-sided heart.
The early phases of embryological development in the De-
cnpods are much as in the Edrioplilhalma. Most Decapods
leave the egg in a larval state called the Zoea. In the
shrimps, Lucifer and Peneus, the young is a Nauplius, like
a young Entomostracan, having but three pairs of feet, and
a single eye. The Zoea has no thoracic feet, and usually at first
DECAPODA.
293
no abdominal feet ; the compound eyes are large and usually
sessile, and the carapace is often armed with a long dorsal
and frontal spine. Fig. 260 represents the Zoea, or larva of
the common shore crab (Cancer irroratus Say). After sev-
Fig. 260. —Zoea of the common Crab. Cancer. Much enlarged.— After Smith.
eral moults, the thoracic legs appear, the mouth -parts
change from swimming -legs to appendages fitted for pre-
paring the food to be swallowed and digested. This stage
in the short-tailed Decapods or crabs, is called the Mega-
lops stage (Fig. 261); certain immature crabs having been
mistaken for and described as mature Crustacea, under the
name Megalops. After swimming about the surface in the
Zoea and Megalops conditions, the body becomes more bulky,
more concentrated headwards, and the crab descends to the
bottom and hides under stones, etc.
The development of the individual crab is, in a general
sense, an epitome of the development of the order. In the
lowest genera, as in Cuma and Mi/sis, the form is some-
what like an advanced Zoea, while the remarkable concentra-
tion of the parts headwards, seen in the crabs, is a great
294
ZOOLOGY.
step upwards. Dana's law of cephalization, or transfer of
parts head-wards, is more strikingly manifested in the Crus-
tacea than in any other animals.
Nearly all Decapods undergo this decided metamorphosis ;
in only a few forms, such as the craw -fish, lobster, and a few
shrimps and crabs, do the young leave the egg in the general
form of the adult, the
Zoe'a stage being rap-
idly assumed and dis-
carded during em-
bryonic life. Most
Crustacea bear their
eggs about with
them ; in only a few
cases, as the Squilla
and the land-crab of
the West Indies, are
the eggs left by the
parent in holes or on
the sea-shore.
Thoracostraca in-
clude Stomapods,
the ScMzopoda, rep-
resented by My sis ;
the Cumacea, repre-
sented by Cwna ; the
long-tailed Decapods,
such as the shrimps
and lobster, called
Macrura, and the genuine short-tailed Decapoda, or Bra-
chyura. Most of the species of the crabs are confined to
tropical seas and live in shallow water.
The Decapods appeared in the Coal Period, and were rep-
resented by somewhat generalized forms, such as An/J/ra-
palamon (Fig. 262) from the coal measures of Illinois.
Eecently a genuine shrimp (PalaopalcBmon] has been de-
scribed by Whitfield from the Upper Devonian formation of
Ohio.
Crustacea, especially shrimps and crabs, are sensitive to
Fig. 261.— Megalops of the Crab.— After Smith.
FOSSIL CRABS.
295
shocks and sounds. When alarmed, lobsters are said to
cast off their large claws, but the latter are again re-
newed. It is more probable, however, that the claws are
torn off during their contests with each other. Hensen
found that crabs and shrimps liv-
ing in water do not notice sounds
made in the air. The hairs about
the mouth are the organs of tac-
tile sense, and have been made by
Hensen to vibrate to certain sounds.
The eyes may be greatly devel-
oped in shrimps living at great
depths ; thus Thalascaris, a shrimp
living near the bottom of the At-
lantic Ocean, is remarkable for the
large size of its eyes. In the spe-
cies of Alphens, which live in holes
in sponges, etc., the eyes are small.
The eves of the blind WillemcBsi
J
dredged at great depths by the
"Challenger" Expedition, are rudimentary, though in the
young the eyes are better developed. This is the case with
the young of the blind craw-fish Cambarus pellucidus (Tell-
kampf, Fig, 263) of Mammoth and other caves. The fact
that the eyes in the young are larger than in the adult indi-
cates that this species has descended from other forms living
in neighboring streams, and well endowed with the sense
of sight. The eye (Fig. 204) of the blind craw-fish differs
from that of the normal species in its smaller size, conical
form, the absence of a cornea (indicated by the dotted lines
in A], the pigment cells being white instead of black, and
by differences in the form of the brain, that of the blind
species being fuller on the sides. Crabs breathe by gills,
but the palm crab breathes by lungs.
Natural size.— Restored.
CLASS II. — PODOSTOMATA.
Podostomata. — This class is proposed for the king-
crab (Limulus), the only survivor of a large number of
fossil Merostomata, which dominated the Silurian seas.
296
ZOOLOGY.
It comprises the order of Merostomata represented at the
present day by the king-crab, and the order Trilobita, which
is wholly extinct. The organization of the king-crab is so
Fig 263.—Cambaruspellucidus, the blind craw-fish of Mammoth Cave. Natural
Size.
wholly unlike that of the Crustacea, when we consider
the want of antennae, the fact that the nervous system la
PODOSTOMA TA.
297
peculiar in form and also ensheathed by arteries, and the
peculiar nature of the gills of the abdominal feet, as well as
the highly developed system of blood-vessels; that we are
obliged to place it with the Trilobites in a division by itself.
B
Fig. 264. — A, Brain and eye of a normal Cambarus from Iowa.
B, The same of the blind craw-fish from Mammoth Cave.
C, Cornea.— Packard, del.
Recent researches also on its development prove that the
Podostomata should form a distinct class of Arthropods,
equivalent on the one hand to the Crustacea and on the
other to the Arachnida, but from the fact that they breathe
like most Crustacea by external gills, we prefer to retain
them in a position between the Crustacea and Arachnida.
Order 1. Merostomata. — The only living representative of
this order is the king-crab, belonging to the genus Li-mulus,
represented in American waters by Limulus Polyphemus
Linn., which ranges from Casco Bay, Maine, to Florida
and the West Indies.
The body of the king-crab is very large, sometimes nearly
two feet in length ; it consists of a cephalo-thorax composed
of six segments and an abdomen with nine segments, the
ninth (telson) forming a long spine. The cephalo-thorax is
broader than long, in shape somewhat like that of Apiix,
with a broad flat triangular fold on the under side. Above
are two large lunate compound eyes, near the middle of the
head, but quite remote from each other, and two small sim-
ple eyes situated close together near the front edge of the
head. There are no antenna?, and the six pairs of append-
298 ZOOLOGY.
ages are of uniform shape like legs, not like mandibles or
maxilla?, and are adapted for walking ; the feet are pro-
vided with sharp teeth on the basal joint for retaining the
food. The mouth is situated between the second pair; the
first pair of legs are smaller than the others. All end in
two simple claws, except the sixth pair, which are armed
with several spatulate appendages serving to prop the crea-
ture as it burrows into the mud. The males differ from the
females in the hand and opposing thumb of the second pair
of feet. These cephalo-thoracic appendages are quite as dif-
ferent from those of most Crustacea as those of the mites
and spiders, which have a pair of mandibles and maxillae,
the latter provided with a palpus. Appended to the ab-
domen are six pairs of broad swimming feet, all except the
first pair of which bear on the under side two sets of about
one hundred respiratory leaves or plates, into which the blood
is sent from the heart, passing around the outer edge and
returning around the inner edge. This mode of respiration
is like that of the Isopods.
The alimentary canal consists of an oesophagus, which
rises directly over the mouth, a stomach lined with rows of
large chitinous teeth, with a large conical, stopper-like valve
projecting into the posterior end of the body ; the intestine
is straight, ending in the base of the abdominal spine. The
liver is very voluminous, ramifying throughout the cephalo-
thorax. The nervous system is quite unlike that of the
Crustacea ; the brain is situated on the floor of the body in
the same plane as the rest of the system, and sends a pair of
nerves to the compound eyes, a single nerve supplying the
ocelli.* The feet are all supplied with nerves from a thick
ring surrounding the oesophagus. The nerves to the six
pairs of abdominal legs are sent off from the ventral cord.
* The nervous system of Limulusisquite unlike that of the Scorpion,
where the brain is situated in the upper part of the head and supplies
the maxillae with nerves, and is situated directly over the infraoeso-
phageal ganglion ; and, besides, there is no oesophageal ring as in
Limulus, only the two commissures connecting the brain with the
infraoosophageal ganglion as usual in the Crustacea and Arachnida in
general.
itf. 265a.— Limulus,
seen from one side.
[To facf page 298.]
ANATOMY OF TUB KING-CRAB. 293
The heart is tubular, with eight pairs of valvular openings'
for the return of the venous blood which Hows into the-
pericardial sac from all parts of the body ; the arterial blood
Fig. 265.— Nervous and part of the circulatory system of Limulus polyphemus, the
King-Crab, a, vent ; ue, oesophagus ; b, brain ; o, nerve to the smaller eyes ; <X, nerve
to the larger eyes ; «. nerve-ring around the oesophagus. All the nerves are surround-
ed by an arterial coat. — After Milne Edwards.
is sent out from the arteries branching from the front end
of the heart flowing around the upper side of the edge of the
cephalo-thorax through numerous minute vessels. Also there
are a pair of branchial arteries, and two arteries in the base of
the spine.
300
ZOOLOGY.
The arrangement of the ventral system of arteries is very
peculiar and quite characteristic of this animal. The o?so-
phageal nervous ring, and in fact the entire nervous cord, is
ensheathed in a vascular coat, so that the nervous system
and its branches are bathed by arterial blood. The veins
are better developed than usual ; there being in the cephalo-
thorax two large collective veins along each side of the in-
testine.
Closely connected with the two large collective veins are
two large brick-red glandular bodies each with four branches
extending up into the dorsal side of the cephalo-thorax.
They are probably renal in their nature.
Both the ovaries and testes are voluminous glands, each
opening by two papillas on the under side of the first ab-
dominal feet. At the time of spawning the ovary is greatly
.distended, the branches filled with green eggs.
Unlike most Crustacea, the female king-crab buries her
-eggs in the sand between tide-marks, and there leaves them
at the mercy of the waves, until the young hatch. The eggs
are laid in the Northern States between the end of May and
rh-
FIG. 266.
FIG. 267
•Fig. 266.— Embryo of King-crab, enlarged ; am, serous membrane ; c/t, chorion.
Fig. 267. — The same, more advanced.
early in July, and the young are from a mouth to six weeks
in hatching.
After fertilization the yolk undergoes total segmentation,
•much as in spiders and the craw-fish. When the primitive
disk is formed the outer layer of blastodermic cells peels off
soon after the limbs begin to appear, and this constitutes
EMBRYOLOGY OF THE KING-CRAB.
301
the serous membrane (Fig. 266, am), which is like that of
insects.
Then the limbs bud out ; the six pairs of cephalic limbs
.appear at once as in Fig. 266. Soon after the two basal
pairs of abdominal leaf-like feet arise, the abdomen be-
comes separated from the front region of the body, and
the segments are indicated as in Fig. 267. A later stage
(Fig. 268) is signalized by the more highly developed dorsal
portion of the embryo, an increase in size of the abdomen,
and the appearance of nine distinct abdominal segments. The
segments of the cephalo-thorax are now very clearly defined,
as also the division between the cephalo-thorax and abdomen,
the latter being now nearly as broad as the cephalo-thorax,
the sides of which are not spread out as in a later stage.
Fig. 268.— King-crab shortly before hatching ; trilobitic stage, enlarged ; side and
dorsal view.
At this stage the egg-shell has split asunder and dropped
off, while the serous membrane, acting as a vicarious egg-
shell, has increased in size to an unusual extent, several
times exceeding its original dimensions and filled with sea-
water, in which the embryo can freely move.
At a little later period the embryo throws off an embry-
onal skin (amnion), the thin pellicle floating about in the
egg. Still later in the life of the embryo the claws are de-
veloped, an additional rudimentary gill appears, and the
abdomen grows broader and larger, with the segments more
302
ZOOLOGY.
distinct ; the heart also appears, being a pale streak along
the middle of the hack extending from the front edge of
the head to the base of the abdomen.
Just before hatching the head-region spreads out, the ab-
domen being a little more than half as wide as the cephalo-
thorax. The two compound eyes and the pair of ocelli on
the front edge of the head are quite distinct ; the append-
ages to the gills appear on the two anterior pairs, and the
legs are longer.
The resemblance to a Trilobite is most remarkable, as
seen in Fig. 268. It now also closely resembles the fossil
king-crabs of the Carboniferous formation (Fig. 269, Prest-
wichia rotundatus, Fig. 270, Belinurus lacoe'i).
Fig. 269.— Prestwichifuflatural size.—
After WqtfSfeii.
Fig. 270.— Belinurus lacoe'i.
In about six weeks from the time the eggs are laid the
embryo hatches. It now differs chiefly from the previous
stage in the abdomen being much larger, scarcely less in
size than the cephalo-thorax ; in the obliteration of the seg-
ments, except where they are faintly indicated on the car-
diac region of the abdomen, while the gills are much larger
than before. The abdominal spine is very rudimentary; it
forms the ninth abdominal segment.
The reader may now compare with our figures of the re-
RELATIONSHIP OF L1MULUS TO TRILOB1TES. 303
cently hatched Limulus (Fig. 271), that of Barrande's larva
of Tri nucleus ornatus (Fig. 272, natural size and enlarged).
He will see at a glance that the young Trilobite, born with-
out any true thoracic segments, and with the head articu-
lated with the abdomen, closely resembles the young Limu-
lus. In Limulus no new segments are added after birth ;
in the Trilobites the numerous thoracic segments are add-
ed during successive moults. The Trilobites thus pass
through a well-marked metamorphosis, though by no means
so remarkable as that of the Decapods and -the Phyllopods.
Fig. 272.— Larva of a Trilo-
bite, Trinucletts ornatus.—
After Barrande.
Fig. 271.— Larva of the King-crab.
The young king-crabs swim briskly up and down, skim-
ming about on their backs like Phyllopods, by napping their
gills, not bending their bodies. In a succeeding moult, which
occurs between three and four weeks after hatching, the
abdomen becomes smaller in proportion to the head, and the
abdominal spine is about three times as long as broad. At
this and also in the second, or succeeding moult, which oc-
curs about four weeks after the first moult, the young king-
crab doubles in size. It is probable that specimens an inch
long are about a year old, and it must require several years
for them to attain a length of one foot.
The Limuli of the Solenhofen slates (Jurassic) scarcely
differed in appearance from those of their living descend-
ants.
Limulus, Prestwiclna, Bellinurus, and Euproojis form
304 ZOOLOGY.
the representatives of the suborder Xiphosura. The second
suborder Eari/jiti-rnlu is represented by extinct genera Ptt-rii-
gotus, Eurypterus and allies which appeared in the upper
Silurian Period and became extinct in the Coal Period. In
these forms the cephalothorax is small, flattened and nearly
square, while the abdomen is long, with twelve or thirteen
segments, the last one forming a spoon-shaped or acute
spine. The appendages of the cephalothorax were adapted
for walking, one pair sometimes large and chelate ; the
hinder pair paddle-like. The gills were arranged like the
teeth in a rake, the flat faces being fore and aft. While the
king-crab burrows in the mud and lives on sea-worms, the
Eurypterida probably swam near the surface, and were more
predatory than the king-crabs. The Merostomata are a gen-
eralized type, with some resemblances to the Ararhnida as-
well as to the genuine Crustacea, resembling the former in
the want of antennae, and their mode of development.
Order 2. Trilobita. — The members of this group are all
extinct. The body has a thick dense integument like that
of Limulus, and is often variously ornamented with tuber-
cles and spines. The body is divided into three longi-
tudinal lobes, the central situated over the regioii of the
heart as in Limulus. The body is more specialized than in
the Merostomata, being divided into a true head consisting
of six segments bearing jointed appendages, somewhat like
those of the Merostomata, with from two to twenty-six dis-
tinct thoracic segments (probably bearing short jointed limbs
not extending beyond the edge of the body, which support-
ed swimming and respiratory lobes). The abdomen consisted
of several (greatest number twenty-eight) coalesced segments,
forming a solid portion (pyyidium}, sometimes ending in a
spine, and probably bearing membranous swimming feet.
The larval trilobite was like that of a king-crab, and after a
number of moults acquired its thoracic segments, there being
a well-marked metamorphosis. The Trilobites (Parado.nilcs,
Agnostus, etc.) appeared in the lowest Cambrian strata, cul-
minated in the upper Silurian, and died out at the close of
the Coal Period.
CLASSIFICATION OF CRUSTACEA.
305
CLASS. I. CRUSTACEA.
Arthropoda breathing by gills xiluatcd on the legs, or respiring through
tJu' body-walls. Body in the higher forms divided into two regions, a
cephalo-thorax and abdomen. Two pairs of antennce ; mandibles usu-
ally with a palpus. Heart nearly square, or in the lower forms tubular.
Often a distinct metamorphosis. Sexes distinct, except in a few cases
(certain barnacles, etc.).
Order 1. Branchiopoda. Thoracic feet leaf-like ; one to three pairs of
maxillee ; number of body-segments varying from a few to
sixty ; ceplialo-thorax often well developed, and forming a
bivalved shell. Young usually a Nauplius. Suborder 1.
Ostracoda (Cypris). Suborder 2. Cladocera (Daphnia). Sub-
order 3. Phyllopoda (Limnadia, Apus, Branchipus, and Ar-
temia.)
Order 2. Entomostraca. — A ceplialo-thorax developed ; mandibles and
three pairs of maxillse ; five pairs of thoracic feet, no ab-
dominal feet ; without any gills. The parasitic forms more
or less modified in shape, with sucking mouth-parts ; all
the young of the nauplius form. Suborder 1. Copepoda
(Cyclops). Suborder 2. Siphonostoma (Lerntea, Caligus, and
Argulus).
Order 2. Cirripedia. — Sessile often retrograded ; antennae not devel-
oped, living parasitically, the appendages of the head some-
times forming root-like organs. Young hatched in the nau-
plius state. Suborder 1. — Rhizocephala (Sacculina, Pelto-
gaster). Suborder 2. — Genuine Cirripedia (Balanus, Lepas.)
Order 4. Edriopthalma. — No cephalolhorax, thoracic segments dis-
tin t ; respiration often carried on by the abdominal feet.
Suborder 1. Isopoda (Idotsea, Asellus). Suborder 2. Am*.
phipoda, (Qammarus).
Order 5. Phyllocarida. — Body compressed; rostrum distinct from the
carapace ; thoracic feet leaf-like ; no metamorphosis. (Ne-
balia.)
Order 6. Thoracostraca. — Cephalothorax well marked, abdomen often
bent beneath the cephalothorax; breathing by gills attached!
to the maxillipedes and legs. Heart often nearly pentagonal.
Usually a well marked metamorphosis ; young called a
Zoea. Suborder 1. Cumacea (Cuma). Suborder 2. Syncarida
(Acanthotelson). Suborder 3. Stomapoda (Squilla). Sub-
order 4. Schizopoda (Mysis). Suborder 5. Decapoda (Cran-
gon, Astacus, Homarus, Cancer).
306
ZOOLOGY.
CLASS II.— PODOSTOMATA.
Appendages of the cephalothorax in the form of legs, spiny at tht base ;
no antennae ; brain supplying nerves to the eyes alone ; nerves to the
.cephalothoracic appendages sent off from an wsophageal ring; nervous
system ensheathed by a ventral system of arteries ; metamorphosis slight,
flexes distinct.
Order 1. Merostomata. — No distinct thoracic segments and appendages.
(Limulus, Eurypterus.)
Order 2. Trilobita. — Numerous free thoracic segments and jointed ap-
pendages. (Agnostus, Paradoxides, Calymene, Trinucleus,
Asaphus; all extinct.)
CLASSIFICATION OF THE ORDERS OF CRUSTACEA AND PODOSTOMATA.
g
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1
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o
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1
CRUSTACEA.
PODOSTOMATA.
Laboratory Work. — In dissecting the lobster, the shell or crust may
be removed by a stout knife ; the whole dorsal portion of the cephalo-
thorax and each segment behind, including the base of the telson,
should be removed, care being taken not to injure the brain, which lies
just under the base of the rostrum. The hypodermis, or reddish, mem-
branous, inner layer of the integument, should then be dissected away,
exposing the heart, the stomach, the liver, and the large muscles of
the abdomen. The arterial system can be injected with carmine
GENERAL CHARACTERS OF INSECTS. 307
through the heart, and the finer arteries traced into the large claws
and legs. In the crab, the entire upper side of the carapace may be
removed by the point of a knife. The smaller Crustacea, especially
the water-fleas, may be examined alive under the microscope as trans-
parent objects. In the larger forms the stomach may be laid open by
the scissors in order to study its complicated structure. The eyes of
the lobster should be hardened in alcohol and fine sections made for
the microscope. This is an operation requiring much care and expe-
rience. Experts in embryology have sliced the eggs of certain Crusta-
cea and studied their embryology with great success.
THE AIR-BREATHING ARTHROPODA (Centipedes, Spiders,
Insects).
General Characters of Insects.— While in the worms
there is no grouping of the segments into regions, we have
seen that in most Crustacea there are two assemblages of
segments — *'• £• * a head-thorax and abdomen. In the insects
o *
there is a step higher in the scale of life, a head is separated
from the rest of the body, which is divided into three
regions, the head, thorax, and hind-body (abdomen). More-
over, the insects differ from the Crustacea in breathing by
internal air-tubes which open through breathing-holes
(spiracles) in the sides of the body. The six-footed insects
also have wings, and their presence is correlated with a
differentiation or subdivision of the two hinder segments
of the thorax into numerous pieces.
The number of body-segments in winged insects is seven-
teen or eighteen — i. e., four in the head, three in the thorax,
and ten or eleven in the hind-body. In spiders and mites
there are usually but two segments in the head, four in the
thorax, and a varying number (not more than twelve) in
the abdomen ; in Myriopods the number of segments varies
greatly — {. e., from ten to two hundred. The appendages
of the body are jointed, and perform four different func-
tions— i. e., the antennae are sensorial organs, the jaws and
maxillae are for seizing and chewing or sucking food ; the
308 ZOOLOGY.
thoracic appendages are for walking, and the spinnerets
of the spider, as well as the sting or ovipositor of many
insects, are subservient in part to the continuance of the
species.
Of the winged insects there are two types : first, those in
which the jaws and maxillas are free, adapted for biting, as
in the locust or grasshopper, and, second, those in which
the jaws and maxillae are more or less modified to suck or
lap up liquid food, as in the butterfly, bee, and bug.
Nearly all insects undergo a metamorphosis, the young
being called a larva (caterpillar, grub, maggot) ; the larva
transforms into a pupa (chrysalis), and the pupa into the
adult (imago).
In order to obtain a knowledge of the structure, external
and internal, of insects, the student should make a careful
study of the anatomy of a locust or grasshopper with the aid
of the following description ; and afterward rear from the
egg a caterpillar and watch the different steps in its metamor-
phosis into a pupa and adult. The knowledge thus acquired
will be worth more to the student than a volume of descrip-
tions.
On making a superficial examination of the locust (Calop-
tenus femur-rubrum, or C. spretus), its body will be seen to
consist of an external crust, or thick, hard integument, pro-
tecting the soft parts or viscera within. This integument
is at intervals segmented or jointed, the segments more or
less like rings, which, in turn, are subdivided into pieces.
These segments are most simple and easily comprehended
in the abdomen or hind-body, which is composed of ten of
them. The body consists of seventeen of these segments,
variously modified and more or less imperfect and difficult
to make out, especially at each extremity of the body —
i.e., in the head and at the end of the abdomen. These
seventeen segments, moreover, are grouped into three re-
gions, four composing the head, three the thorax, and ten
the hind-body, or abdomen. On examining the abdomen,
it will be found that the rings are quite perfect, and that
each segment may be divided into an upper (tergal), a lateral
(pleural), and an under (sternal) portion, or arc (Fig. 273, A).
ANATOMY OF INSECTS.
309
These parts are respectively called tergite, plcurite, and
stenute, while the upper region of the body is called the
Fig. 2T3. — External anatomy of Caloptenus spretus, the head and thorax dis-
jointed, up, uropatagium; /, furcula; c, cercus.— Drawn by J. S. Kingsley.
teryum, the lateral the pleurum, and the ventral or under
portion the sternum.
310 ZOOLOGY.
As these parts are less complicated in the abdomen, we
will first study this region of the body, and then examine the
more complex thorax and head. The abdomen is a little
over half as long as the body, the tergum extending far
down on the side and merging into the pleurum without
any suture or seam. The pleurum is indicated by the row
of spiracles, which will be noticed further on. The sternum
forms the ventral side of the abdomen, and meets the pleu-
rum on the side of the body.
In the female (Fig. 273, B}, the abdomen tapers some-
what toward the end of the body, to which are appended
the two pairs of stout, hooked spines, forming the oviposi-
tor (Fig. 273, B, r, ?•'). The anus is situated above the upper
and larger pair, and the external opening of the oviduct,
which is situated between the smaller and lower pair of
spines, and is bounded on the ventral side by a movable tri-
angular acute flap, the egg-guide (Fig. 273, B, eg, and Fig.
276).
The thorax, as seen in Fig. 273, consists of three seg-
ments, called the prothorax, mesothorax, and metathorax, or
fore, middle, and hind thoracic rings. They each bear a
pair of legs, and the two hinder each a pair of Avings. The
upper portion (tergum) of the middle and hind segments,
owing to the presence of wings and the necessity of freedom
of movement to the muscles of flight, are divided or differ-
entiated into two pieces, the scutum and scutellum* (Fig.
273), the former the larger, extending across the back, and
the scutellum a smaller, central, shield-like piece. The
protergum, or what is usually in the books called the pro-
thorax, represents either the scutum or both scutum and
scutellum, the two not being differentiated.
The fore wings are long and narrow, and thicker than
the hinder, which are broad, thin, and membranous, and
most active in flight, being folded up like a fan when at
rest and tucked away out of sight under the fore wings,
which act as wing-covers.
* There are in many insects, as in many Lepidoptern and Hymenop-
tera and some Neuroptera, four tergal pieces — i. e. , praescutum, scutum,
scutellum, and postscutellum, the first and fourth pieces being usually
very small and often obsolete.
AX ATOMY OF INSECTS.
311
313
ZOOLOGY.
Turning now to the side of the body under the insertion
of the wing (Fig. 274), we see that the side of each of the
middle and hind thoracic rings is composed of two pieces,
the anterior, episternum, resting on the sternum, with the
epimerum behind it ; these pieces are vertically high and
narrow, and to them the leg is inserted by three pieces,
called respectively coxa, trochantine, and trochanter (see Fig.
274), the latter forming a true joint of the leg.
The legs consist of five well-marked joints, the femur
(thigh), tibia (shank), and tarsus (foot), the latter consist-
ing in the locust of three joints, the third bearing two large
claws with a pad between them. The hind legs, especially
the femur and tibia, are very large, adapted for hopping.
The sternum is broad and large in the middle and hind
thorax, but small and obscurely limited in the prothorax,
with a large conical projection between the legs.
The head is mainly in the adult locust composed of a sin-
gle piece called the epicranium (Figs. 274 and 275, E}, which
carries the compound eyes, ocelli, or simple eyes (Fig. 275,
e), and antenna?. While there are in real-
ity four primary segments in the head of
all winged insects, corresponding to the
four pairs of appendages in the head, the
posterior three segments, after early em-
bryonic life in the locust, become obsolete,
and are mainly represented by their ap-
pendages and by small portions to which the
appendages are attached. The epicranium
represents the antennal segment, and
mostly corresponds to the tergum of the seg-
ment. The antenna3, or feelers, are in-
serted in front of the eyes, and between
— Front
le head of C.
E, epicrani-
view ot
gpretus.
um ; C, clypeus ; L,
labrum; o o, ocelli; e,
eye; a. antenna; md,
mandible; ma:,portion them is the anterior ocellus, or simple eye,
of maxilla uncovered . ... .,
by the labrum ; p, while the two posterior ocelli are situated
maxillary palpus; p\ . ... ,> ,n T
labial paipus.-Kings- above the insertion of the antennae. In
front of the epicranium is the clypeus (Fig.
275), a piece nearly twice as broad as long. To the clypeus
is attached a loose flap, which covers the jaws when they
are at rest. This is the upper lip or labrum (Fig. 275).
MOUTH-PARTS OF INSECTS. 313
There are three pairs of mouth-appendages : first, the true
jaws or mandibles (Fig. 273), which are single-jointed, and
are broad, short, solid, with a toothed cutting and grinding
edge, adapted for biting. The mandibles are situated on
each side of the mouth -opening. Behind the mandibles
are the maxilla? (Fig. 273), which are divided into three
lobes, the inner armed with teeth or spines, the middle lobe
unarmed and spatula-shaped, while the outer forms a five-
jointed feeler called the maxillary palpus. The maxillae are
accessory jaws, and probably serve to hold and arrange the
food to be ground by the true jaws. The floor of the mouth
is formed by the labium (Figs. 273 and 274), which in real-
ity is composed of the two second maxilla?, soldered together
in the middle, the two halves being drawn separately in Fig.
273; to each half is appended a three-jointed palpus.
Within the mouth, and situated upon the labium, is the
tongue (lingua], which is a large, membranous, partly hol-
low expansion of the base of -the labium ; it is somewhat
pyriform, slightly keeled above, and covered with fine, stiff
hairs, which, when magnified, are seen to be long, rough,
chitinous spines, with one or two slight points or tubercles
on the side. These stiff hairs probably serve to retain the
food in the mouth, and are, apparently, of the same struc-
ture as the teeth in the crop. The base of the tongue is
narrow, and extends back to near the pharynx (or entrance
to the gullet), there being on the floor of the mouth, behind
the tongue, two oblique slight ridges, covered with stiff,
golden hairs, like those on the tongue.
The internal anatomy may be studied by removing the
dorsal wall of the body and also by hardening the insect
several days in alcohol and cutting it in two longitudinally
by a sharp scalpel.
The oesophagus (Fig. 276, o?) is short and curved, contin-
uous with the roof of the mouth. There are several longi-
tudinal irregular folds on the inner surface. It terminates
in the centre of the head, directly under the supra-oesopha-
geal ganglion, the end being indicated by several small coni-
cal valves closing the passage, thus preventing theregurgita-
tion of the food. The two salivary glands consist each of a
314 ZOOLOGY.
bunch of follicles, emptying by a common duct into the floor
of the mouth.
The oesophagus is succeeded by the crop (inylnries). It
dilates rapidly in the head, and again enlarges before pass-
ing out of the head, and at the point of first expansion or
enlargement there begins a circular or oblique series of folds,
armed with a single or two alternating rows of simple spine-
like teeth. Just after the crop leaves the head, the rugae or
folds become longitudinal, the teeth arranged in rows, each
row formed of groups of from three to six teeth, which
point backward so as to push the food into the stomach.
In alcoholic specimens the folds of the crop and oesophagus
are deep blood-red, while the muscular portion is ilesh-col-
ored. It is in the crop that the " molasses " thrown out by
the locust originates.
The proventriculus is very small in the locust, easily over-
looked in dissection, while in the green grasshoppers it is
large and armed with sharp teeth. A transverse section of
the crop of the cricket shows that there are six large irreg-
ular teeth armed with spines and hairs (Fig. 277). It
forms a neck or constriction between the crop and true
stomach. It may be studied by laying the alimentary canal
open with a pair of tine scissors, and is then seen to be
armed with six flat folds, suddenly terminating posteriorly,
where the true stomach (chyle-stomach, ventriculus) begins.
The chyle-stomach is about one half as thick as the crop,
when the latter is distended with food, and is of nearly tho
same diameter throughout, being much paler than the ivd-
dish crop, and of a flesh-color.
From the anterior end arise six large t/</*frir ccBca, which
are dilatations of the true chyle-stomach, and probably serve
to present a larger surface from which the chyle may escape
into the body-cavity and mix with the blood, there being in
insects no lacteal vessels or lymphatic system.
The stomach ends at the posterior edge of the fourth ab-
dominal segment in a slight constriction, at which point
(pylori c end) the urinary tubes (>'<t*(t uriiuiria. Fig. 276,
ur) arise. These are arranged in ten groups of about fifteen
tubes, so that there arc about one hundred and fifty long,
fine tubes in all.
ANATOMY OF INSECTS.
315
316
ZOOLOGY.
The intestine (ileum) lies in the fifth and sixth abdominal
segments.
Behind the intestine is the colon, which is smaller than
the intestine proper, and makes a partial twist. The colon
suddenly expands into the rectum, with six large rectal
glands on the inside, held in place by six muscular hands
attached anteriorly to the hinder end of the colon. The
rectum turns up toward its end, and the vent is situated
just below the supra-anal plate.
Having described the digestive canal of the locust, we
may state in a summary way the functions of the different
divisions of the tract. The
food after being cut up by the
jaws is acted upon while in
the crop by the salivary lluid,
which is alkaline, and pos-
sesses the property, as in ver-
tebrates, of rapidly transform-
ing the starchy elements of
the food into soluble and as-
similable glucose.
The diges-
tive action carried on in the
crop (ingluvies) then, in a veg-
etable-feed ing insect like the
Fig 277.-Transver.-e section of the loCUSt, ICSllltS ill the COIlVer-
crop of Giyllns cin evens of Europe; muc, • f ,,
muscular walls ; r, horny ridge between S1O11 OI the Starchy matters
into glucose or sugar. This
process goes on very slowly. When digestion in the crop
has ended, the matters submitted to an energetic pressure
by the walls of the crop, which make peristaltic contrac-
tions, filter gradually through the short, small proventricu-
lus, directed by the furrows and chitinous project ons lining
it. The apparatus of teeth does not triturate the food,
which has been sufficiently comminuted by the jaws. This
is proved by the fact, says Plateau, that the parcels of food
are of the same form and size as those in the crop, before
passing through the proventriculus. The six large lateral
pouches (coeca) emptying into the commencement of the
stomach (ventriculus) are true glands, which secrete an al-
DIGESTION IN INSECTS. 317
kalino fluid, probably aiding in digestion. In tne stomach
(ventriculus) the portion of the food which has resisted the
action of the crop is submitted to the action of a neutral or
alkaline liquid, never acid, secreted by special local glands
or by the lining epithelium. In the ileum and colon ac-
tive absorption of the liquid portion of the food takes place,
and the intestine proper (ileurn and colon) is thus the seat
of the secondary digestive phenomena. The reaction of the
secretion is neutral or alkaline. The rectum is the ster-
coral reservoir. It may be empty or full of liquids, but
never contains any gas. The liquid products secreted by
the urinary tubes are here accumulated, and in certain cir-
cumstances here deposit the calculi or crystals of oxalic,
uric, or phosphatic acid. Insects, says Plateau, have no
special vessel to carry off the chyle, such as the lacteals or
lymphatics of vertebrates ; the products of digestion — viz.,
salts in solution, peptones, sugar in solution, and emulsion-
ized greasy matters — pass through the fine coatings of the
digestive canal by osmosis, and mingle outside of this canal
with the currents of blood which pass along the ventral and
lateral parts of the body.
Into the pyloric end of the stomach empty the urinary
tubes, their secretions passing into the intestine. These are
organs exclusively depuratory and urinary, relieving the
body of the waste products. The liquid which they secrete
contains urea (?), uric acid, and urates in abundance, hip-
puric acid (?), chloride of sodium, phosphates, carbonate of
lime, oxalate of lime in quantity, leucine, and coloring mat-
ters.
The nervous system of the locust, as of other insects, con-
sists of a series of nerve-centres, or so-called brains (ganglia),
which are connected by two cords (commissures), the two
cords in certain parts of the body in some insects united into
one. There are in the locust ten ganglia, two in the head,
three in the thorax, and five in the abdomen. The first
ganglion is rather larger than the others, and is called tne
' brain." The brain rests upon the oesophagus, whence its
name, supra-cesophageal ganglion. From the brain arise the
large, short, optic nerves (Fig. 276, not lettered, but repre-
318
ZOOLOGY.
gented by the circle behind the brain, sp ; Fig. 278,
which go to the compound eyes, and from the front arise
It — i
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rv ., >-, 3^ ™* w
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the three slender filaments which are sent to the three ocelli
(Fig. 276, oc). From immediately in front, low down, arise
NERVOUS SYSTEM OF INSECTS.
319
the antennal nerves (Fig. 276, at}. The simple brain of the
locust may be compared with the more complicated brain of
an ant, as seen in Fig. 279.
The infra-<Bsophageal ganglion (Fig. 278, ?"/"), as its name
implies, lies under the oesophagus at the base of the head, un-
ati
l
Fig:. 279.— Right half of an ant's-brain: nG, infra-oesophageal ganglion; Or, brain ;
(?, central connective portion-* ; W, semi-circular bodies of the small-celled portion
of the brain lyin j next to the basal portion of the braiu, from which the nerves to the
simple eyes (aw) arise ; Au, optic lobes ; An. antennal lobes (the bodies appearing
like cells are rounded masses of ihe network of the substance ol the cord ; r, cellu-
lar cortical substance of the brain ; ko. twofold body of the commissure connecting
the brain with the int'ra-cesophageal ganglion. — After Leydig, from Graber.
der a bridge of chitine, and directly behind the tongue. It is
connected with the supra-oesophageal ganglion by two com-
missures passing up each side of the oesophagus. From the
under side of the infra-oesophageal ganglion arise three
pairs of nerves, which are distributed to the mandibles.
320
ZOOLOGY.
maxillge, and labium. The mandibular nerves project for-
ward and arise from the anterior part of the ganglion, near
the origin of the supra-cesophageal commissures, while the
maxillary and labial nerves are directed downward into
those organs.
The sympathetic ganglia are three in number ; one situ-
ated just behind the supra-cesophageal ganglion (Fig. 273,
as), resting on the oesophagus, and two others situated each
side of the crop, low down. Each of
the two posterior ganglia is supplied
by a nerve from the anterior ganglion.
Two nerves pass under the crop con-
necting the posterior ganglia, and
from each posterior ganglion a nerve
is sent backward to the end of the
proventriculus. A pair of nerves pass
under the oesophagus from each side
of the anterior sympathetic ganglion,
and another pair pass downward to a
round white body, whose nature is
unknown (Fig. 273, u}.
Fig. 280 represents an enlarged
view of the brain and sympathetic
nerve of a moth. The heart is a long
tube lying in the abdomen, dilating
at six places along its course, and
ending in a conical point near the
end of the abdomen ; it is held in
place by fine muscular bands.
All insects breathe by means of a
complicated system of air-tubes rami-
fying throughout the body, the air
entering through a row of spiracles, or air-holes, or breath-
ing-holes (stigmata), in the sides of the body. There are in
locusts two pairs of thoracic and eight pairs of abdominal
spiracles. The first thoracic pair (Fig. 281) is situated on
the membrane connecting the prothorax and mesothorax,
and is covered by the hinder edge of the protergum (usually
called prothorax). The second spiracle is situated on the
Fig. 280.— Supra-cesopha-
geal ganglion and visceral (or
sympathetic) nervous system
of the silk-worm moth(Bw/i-
b>/x moii). gs, Supra-oei-so-
phageal ganglion ('' brain ") ;
a, antennary nerve ; 0, optic
nerve ; r, azygos trunk of the
visceral nervous system ; r',
its roots arising from the
Bupra-ecsophageal ganglion ;
«, paired nerve with its gangli-
onic enlargements s' s". —
After Brandt, from Gegen-
baur.
RESPIRATORY ORGANS OF INSECTS. 321
posterior edge of the mesothorax. There are eight abdominal
spiracles, the first one situated just in front of the auditory
sac or tympanum (see Fig. 274), and the remaining seven are
small openings along the side of the abdomen, as indicated
in Fig. 281. From these spiracles air-tubes pass in a short
distance and connect on each side of the body with the ftpi-
racular Intellect (Fig. 281, s, Fig. 282, s), as we may call it,
The air-tubes consist of two coats, in the inner of which is
developed the so-called spiral thread (tsenidium). These
spiracular tracheae begin at the posterior spiracle, and extend
forward into the mesothorax, there subdividing into several
branches. Branches from them pass to the two main ven-
tral trachea? (Fig. 281, r), and to the two main dorsal tra-
cheae (Fig. 281, D, Fig. 282, D). The main tracheal sys-
tem in the abdomen, then, consists of six tubes, three on a
side, extending along the abdomen. The pair of ventral
tracheae extend along the under side of the digestive canal;
the dorsal tracheae rest on the digestive canal. These six
tubes are connected by anastomosing tracheae, and, with
their numerous subdivisions and minute twigs and the sys-
tem of dilated tracheae or air-sacs, an intricate network of
trachea3 is formed.
The system of thoracic air-tubes is quite independent of
the abdominal system, and not so easy to make out. The
tubes arising from the two thoracic stigmata are not very
Avell marked; they, however, send two well-marked tracheae
into the head (Fig. 281, c, Fig. 282, c), which subdivide into
the ocular dilated air-tube (Fig. 281, oc, Fig. 282, oc} and a
number of air-sacs in the front of the head.
The series of large abdominal air-sacs, of which there are
five pairs (Fig. 282, 3-7), arise independently of the main
tracheae directly from branches originating from the spira-
cles, as seen in Fig. 281. They are large and easily found!
by raising the integument of the back. There is a large
pair in the mesothorax (Fig. 282, 2) and two enormous sacs
in the prothorax (Fig. 282, 1), sometimes extending as far-
back as the anterior edge of the mesothorax. All these sacs
are superficial, lying next to the hypodermis or inner layer
of the integument, while the smaller ones are, in many cases^
322
ZOOLOGY.
8-
s
/
-J)
s-
Pie. 281.
Fie. 282
HESPIRATION IN INSECTS.
buried among the muscles. Besides the ordinary air- sacs,
there is in the end of the abdomen, behind the ovaries, a
plexus of six dilated air-sacs (Fig. 282, I, II, III), which
are long, spindle-shaped, and are easily detected in dis-
secting.
There is a system of dilated tracheas and about fifty air-
sacs in the head.
In the legs two tracheae pass down each side of the femora,
sending off at quite regular intervals numerous much-branch-
ing, transverse twigs ; there is one large and a very small
trachea in the tibia, and the main one extends to the ex-
tremity of the last tarsal joint.
By holding the red-legged locust in the hand, one may
observe the mode of breathing. During this act the por-
tion of the side of the body between the spiracle and the
pleurum (Fig. 273, A) contracts and expands ; the contrac-
tion of this region causes the spiracles to open. The gen-
eral movement is caused by the sternal moving much more
decidedly than the tergal portion of the abdomen. When
the pleural portion of the abdomen is forced out, the soft
pleural membranous region under the fore and hind wings
contracts, as does the tympanum and the membranous por-
tions at the base of the hind legs. When the tergum or
dorsal portion of the abdomen falls and the pleurum con-
tracts, the spiracles open ; their opening is nearly but not
always exactly co-ordinated with the contractions of the
pleurum, but as a rule they are. There were sixty-five con-
tractions in a minute in a locust which had been held be-
tween the fingers about ten minutes. It was noticed that
when the abdomen expanded, the air-sacs in the first ab-
Fig. 281.— Showing distribution of air-tubes (tr: che«) and air-sacs — side view of
the oody. ?>, main ventral trachea (only one of tin iwo shown) ; «, left stigmata]
trachea, connecting by vertical branches with D, the left main dorsal trachea; c, left
cephalic trachea ; or, ocular dilated trachea. From the first, second, third, and fourth
spiracles arise the tirst four abdominal air-sacs, which are succeeded by the plexus
of three pairs of dilated tracheae, I, II, III, in Fig. 287. Numerous air-sacs and
trachea; are represented in the head and thorax. The two thoracic spiracles are rep-
resented, but not lettered.
Fig. 282.— A loft dorsal trachea: K. left stigmata! trachea : T, II, III, first, second,
and third pairs of abdominal dilated tracheae, forming a plexus behind the ovaries ;
1, pair of enormous thoracic air-sacs ; 2, pair of smaller air-sacs ; 3-7. abdominal
air-sacs; or. ocular dilated trachea and air-sacs; <*, cephalic trachea. The relations
of the heart to tne dorsal tracheae are indicated.— Drawn by Emerton from dissec-
tions by author.
3-^4 ZOOLOGY.
dorainal ring contracted. The respiratory movements, as
Plateau states, consist of the alternate contraction and re-
covery of the figure of the abdomen in two dimensions, i.e.,
vertical and transverse. During expiration the abdomen
contracts, while during inspiration it returns to its normal
shape. (Miall and Denny's "The Cockroach.")
It is evident that the enormous powers of
flight possessed by the locust, especially its fac-
ulty of sailing for many hours in the air, is due
to the presence of these air-sacs, which float it
up in the atmospheric sea. Other insects with
a powerful flight, as the bees and flies, have well-
developed air-sacs, but they are less numerous.
It will be seen that, once having taken flight,
the locust can buoy itself up in the air, con-
stantly filling and refilling its internal buoys or
balloons without any muscular exertion, and
thus be borne along by favorable winds to its-
Fig 283.— destination. It is evident that the process of
Action1 oUfdi"he respiration can be best carried on i" clear, sunny
trachea of Hy- weather, and that when the sun sets, t>r the
dropfiiluspiceus ,1-11
or water-beetle, weather is cloudy and damp, its powers of flight
ep, epithelium; , ~ l . . 1.
cu, cuticuia;/, are lessened, owing to the diminished power of
—After Minot' respiration. The finer structure of the trachea,
is seen in Fig. 283.
It is difficult to explain many of the actions of insects,.
from the fact that it is hard for us to appreciate their men-
tal powers, instincts, and general intelligence. That they
have sufficient intellectual powers to enable them to main-
tain their existence may be regarded as an axiom. But in-
sects differ much in intelligence and also in the degree of
perfection of the organs of sense. The intelligence of in-
sects depends, of course, largely on the development of the
organs of special sense.
The sense of sight must be well developed in the locust,
there being two large, well-developed compound eyes, and
three simple ones (ocelli], situated between the former, sup-
plied with nerves of special sense.
Fig. 284 represents the eye of a moth greatly enlarged to
show the finer structure.
SENSES OF INSECTS.
3.25
The antennae are, in the locust, organs of smell, The
palpi are probably only organs of touch. It has been shown
by F. Will that wasps have the sense of taste, and that
minute gustatory organs are placed near the mouth. These
organs,, in the shape either of pits or projecting bulbs, in
connection with peculiar nerve-endings, are situated on the
labium, paraglossae, and on the inner side of the maxillae.
Similar organs occur in ants.
f-
Fig. 284.— Longitudinal section of the facetted eye of asphinx: the eye-capsule or
sclera facetted externally (/), and s:eve-like within, shows the rod-like ending of the
optic nerve-fibres ; k, layer of the crystalline lens; i, iris-like-pigment zone; eh,
choroid composed of pigment cells ; *•//, optic nerve ; tr, trachea lost in fine bundles
of fibrilhe. — After Leydig, from Graber.
The ears are well developed in the locust, and we know
that the sense of hearing must be delicate, not only from the
fact that a loud alarum with kettles and pans affects them,
but the movements of persons walking through the grass
invariably disturb them. Besides this, they produce a fid-
dling or stridulating sound by rubbing their hind legs
against their folded wing-covers, and this noise is a sexual
326
ZOOLOGY.
sound, heard and appreciated by individuals of the other
sex. Any insect which produces a sound must be supposed to
have ears to hear the sound pro-
duced by others of its species.
In the antennas, palpi, and
abdominal appendages of dif-
ferent insects are seated mi-
nute olfactory organs consisting
of pits alone (Fig. 285), or of
c, sense-organ on the terminal joint of llq]'rs: nprfm^rprl at T!TP pml on,]
palpus of Perla.— Author del. liailb peilOiaieCl at tlie 611(1, III id
pegs associated with the pits.
The ears (or auditory sacs) of the locust are situated, one
on each side, on the basal joint of the abdomen, just be-
Fig. 286.— Ear of a locust (Calnptfnus italicus) seen from the inner side. T, tym-
panum ; TR, its border ; o, //, two horn-like processes ; hi. pear-shaped vesicle ; n,
auditory nerve ; ga, terminal ganglion; st, stigma ; in, opening and m' closing mus-
cle of the same ; JU, tensor muscle of the tympanum-membrane.— After Graber.
hind the first abdominal spiracle (Fig. 274). The ap-
paratus consists of a tense membrane, the tympanum, sur-
rounded by a horny ring (Fig 286). " On the internal sur-
ORGANS OF HEARING.
327
face of this membrane are two horny processes (oti), to which
is attached an extremely delicate vesicle (bi) filled with a
transparent fluid, and representing a membranous labyrinth.
This vesicle is in connection with an auditory nerve (ri)
P..
Fig. 287.— A Carabus beetle in the act of walking or running. Three legs (Z>, R*.
Z3), are directed forward, while the others (Rl, L-, Ii*), which are directed back-
ward toward the tail, have ended their activity, a b, c </, and <?/are curves described
by the end of the tibias and passing back to the end of the body; b h, d i, and/ cj are
curves described by the same legs during their passive change of position.— After
Graber.
which arises from the third thoracic ganglion, forms a gan-
glion (go) upon the tympanum, and terminates in the im-
mediate neighborhood of the labyrinth by a collection of
328
ZOOLOGY.
109
cuneiform, staff-like bodies, with very finely-pointed ex-
tremities (primitive nerve-fibres?), which are surrounded
by loosely aggregated gangl ionic globules." (Siebold's
Anatomy of the Invertebrates.)
In walking, the locust, beetle, or, in fact, any insect,
raises and puts down its six legs alternately, as may be
seen by observing the movements
of a beetle (Fig. 287). While the
structure of the limb of a ver-
tebrate and insect is not homol-
ogous, yet the mechanism or
functions of the parts are in
the main the same, as indicated
in Figs. 288 and 289.
The footprints of insects are
sometimes left in fine wet sand
on the banks of streams or by
the seaside.
In Fig. 290 the black dots
are made by the fore, the clear
circle by the middle, and the
black dashes by the hind legs
(Graber).
The wings are developed as
folds of the integument, and
strengthened by hollow rods
called "veins ;" their branches
109
Fig. 288. -Section of the fore leg of called
'venures."
There are
, i ,.
the WlllgS OI most insects
a Stag beetle, showing the muscles. S.
extensor, B, flexor of the leg ; *, ex-
tensor ; ft, flexorof the femur; o. femur; • „ ,1 „ i
u, tibi'i;/. tarsus; fc, claw, 109*,* S1X mam V6111S — I.e., the COStal,
extensor, 6, flexor of the femoro-tibial fl1p ciilmnsfnl morli-- eiil-imc
joint, both enlarged.— After Graber. .OSIdJ, median, SUOme-
dian, internal, and anal. They
are hollow and usually contain an air-tube, and a nerve
often accompanies the trachea in the principal veins. The
arterial blood from the heart (as seen in the cockroach by
Moseley) flows directly into the costal, subcostal, median,
and submedian veins ; here it is in part aerated, and returns
to the heart from the hinder edge of the wings through the
hinder smaller branches and the main trunks of the internal
FLIGHT OF INSECTS.
329
and anal veins. So that the wings of insects act as lungs
as well as organs of flight. For the latter purpose, the
principal veins are situated near the front edge of the wing,
,01
Fig. 289. — Diagram of the knee-joint of a vertebrate (A) and an insect's limb (B).
•a upper, b, lower shank, united at A by a capsular joint, at B by a folding joint ;
•d, extensor or lifting muscle ; d1, flexor or lowering muscle of the lower joint.
The dotted line indicates in A the contour of the leg.— After Graber.
called the, costa, and thus the wing is strengthened when the
most strain comes during the beating of the air in flight.
The wing of an insect in making the strokes during flight
describes a figure 8 in the air. A fly's wing
makes 330 revolutions in a second, executing
therefore 060 simple oscillations.
The sexes are always distinct in insects, the
-only known exception being certain very low
aquatic Arthropods called Tardigrada, in
which both sexual glands occur in the same
individual. The testes of the common red-
legged locust form a single mass of tubular
glands, resting in the upper side of the third,
fourth, and fifth segments of the hind body.
Figs. 291 and 292 represent this structure in
other insects. The ovaries consist of two sets
of about twenty long tubes, within which the
eggs may be found in various stages of de-
velopment. The eggs pass into two main -p^ 290.— Foot-
tubes which unite to form the single oviduct
which lies on the floor of the abdomen.
Above the opening of the oviduct is the sebific
gland and its duct. This gland secretes a copious supply of
u sticky fluid, which is, as in many other insects, poured
/
'••o
330
ZOOLOGY.
out as the eggs pass out of the oviduct, thus surrounding
them with a tough coat.
The external parts consist of the ovipositor (Fig. 273, B,
and Fig. 276), which is formed of two pairs of spines (rhab-
dites) adapted for boring into the earth ; and of the egg-
guicle (Figs. 273 and 276, eg), a triangular flap guarding the
under side of the opening of the oviduct.
..-dr
--to
Fi<r 092 — t testis • 1) vas
Fig. 291.— Male sexual apparatus of a bark-beetle. deferens • ' r/ seminal vesicle
#/, vas deterens ; ho, testis ; bl, seminal vesicle ; ag, of ^c/tet(t campestris.—AStet
cluctus ejaculatorius. — After Graber. Gegenbaur.
There is a remarkable uniformity in the mode of develop-
ment of the winged insects. In general, after fertilization
of the egg> a few cells appear at one end of the egg ; these
multiply, forming a single layer around the egg, this layer
constituting the blastoderm. This layer thickens on one
side of the egg, forming a whitish patch called the primitive
streak or land. The blastoderm molts,
sloughing off an outer layer of cells,
a new layer forming beneath ; the skin
thus thrown off is called the serous
membrane ; the second germ-layer
(ectoderm) then arises, and a second
•v. 233,-Section of sphinx membrane (called amnion, but not
if- ^'"IVoHs'm^ii!- homologous with that of vertebrates)
brane;W amnion; h, outer, peels off from the primitive band -just
m, inner germ-layer.
as the appendages are budding out, so
that the body and appendages of the embryo insect are en-
cased in the amnion as the hand and fingers are encased by
a glove. As seen in the accompanying Figs. 293-298, the
DEVELOPMENT OF INSECTS.
331
appendages bud out from the under side of the primitive-
band, and antennae, jaws, legs, ovipositor (or sting), and the
abdominal feet of caterpillars are at
first all alike. Soon the appendages
begin to assume the form seen in
the larva, and just before the insect
hatches the last steps in the elabora-
tion of the larval form are taken.
As to the development of the in-
ternal organs, the ner-
vous system first origi-
nates ; the alimentary
canal is next formed ;
Fig. 201.— Ernbrvo of Sphinx , , , ,-. • ,.
much more advanced. A, heart ; and at abOllt tlllS time
g, ganglion ; i, intestine ; m, ,-\ L- -i
rudimentary muscular bands run- ED 6 Stigmata ailO. ail*-
nins to the heart ; g, stigma and 4-11i-lfi<! nl.ic(i oo invtio-ini
beginning of a trachea (t) ; d.a. U V digmdr
gland. Tliis and Figs. 293,295 fjo^of f]lo oiltor p-prm-
aftei- Kowalevsky. L feej
layer. The development
of the salivary glands precedes that of the uri-
nary tubes, which, with the genital glands, are
originally offshoots of the primitive digestive
tract. Finally the heart is formed.
•/
When the insect hatches, it either cuts its way ,
through the egg-shell by a temporary egg-cut- Qj.0
ter, as in the flea, 'or the expansion of the 1 jwp
head and thorax and the convulsive movements \o£
of the body, as in the grasshopper, burst the Fjg. o93 _
shell asunder. The serous membrane is left in band"
the shell, but in the case of grasshoppers the °nfotg
larva on hatching is still enveloped m the am- segments in-
dicated, and
nion. This is soon cast as a thin pellicle. their rudimen-
The principal change from the larval to the ages, c, upper
adult locust or grasshopper is the acquisition of me • mdf man-
wings. In such insects, then, as the Orthoptera m^^rli and
and Hemiptera, in which the adults differ from f^c.onf n/'axr"
the newly hatched larva mainly in the posses- legs ; o*. ai>d»
„ J . i • • • j i • miual less-
sion of wings, metamorphosis is said to be in-
complete. In the beetle, butterfly, or bee, the metamorphosis
i? complete ; the caterpillar, for example, is d biting insect,.
ZOOLOGY.
is voracious, and leads a different life from the quiescent,
sleeping pupa or chrysalis, which takes no food ; on the
other hand, the imago or butterfly has mandibles, which
are rudimentary, and incapable of biting, while the maxillae,
or "tongue," which were rudimentary in the caterpillar,
become now greatly developed ; and the butterfly takes
— E
-a
Fig. 296. — Embryo of a
Water-beetle (Hydrophilus). E,
ego ; K, head ; ol, upper lip; m,
mouth ; an, antennae ; £,. raan-
•dibles ; £2, £„, maxilla? ; J5,
thorax ; b,, 62, o?, legs ; A,-^i0,
ten pairs of rudimentary abdo-
minal legs, of which all except A,
disappear before the insect
hatches ; a, anus, — After Kowa-
.levsky.
Fig. 297. —Profile view of embryo
Honey-bee, lettering as in Fig.
2U6. BM, nervous cord; oG, brain;
1), digestive canal ; seh, the oeso-
phagus ; St., Btigmatal openings of
the tracheal system ; K, heart. —
After Blutschli.
liquid food and but little of it, while its surroundings and
mode of life are entirely changed with its acquisition of
wings. Thus the butterfly leads three different lives, differ-
ing greatly in structure, externally and internally, at these
.three periods, and with different environments.
METAMORPHOSIS OF INSECTS.
-an
Most caterpillars moult four or five times ; at each
moult the outer layer of the skin is cast off, the new
skin arising from the hypodermis, or inner layer of the in-
tegument. The skin opens on the back behind the head,
the caterpillar drawing itself out of the rent. In the
change from the caterpillar to the chrysalis, there are re-
markable transformations in the muscles, the nervous,
digestive, and circulatory system, inducing a change of
form, external and internal, characterizing the different
stages in the metamorphosis.
While the changes in form are
comparatively sudden in flies and
butterflies, the steps that lead to
them are gradual. How gradual
they are may be seen by a study of
the metamorphosis of a bee. In
the nest of the humble or honey
bee, the young may be found in all
stages, from the egg to the pupa „
gayly colored and ready to emerge
from its cell. It is difficult to
indicate where the chrysalis stage
begins and the larva stage ends,
yet the metamorphosis is more
complete — namely, the adult bee
is more unlike the larva, than in
any other insect.
Besides the normal mode of de-
velopment, certain insects, as the
plant-louse (Alrftis), the bark-louse aw, 'antennae ; vfc forehead.— After
v * Melnikpw.
(Coccus), the honey-bee, the ro-
listes wasp, the currant saw-fly (Nematus], the gall-flies,
and a few others, produce young from unfertilized eggs.
Certain moths, as the silk-worm moth (Bombyx tnori) and
others, have been known to lay unfertilized eggs from which
caterpillars have hatched. This anomalous mode of repro-
duction is called parthenogenesis, and fundamentally is only
a modification of the mode of producing young by budding
which is universal in plants, and is not unusual, as we have
-am
Fig. S98.— Embryo of the Louse.
am, serous membrane; db, amnion;
334 ZOOLOGY.
seen, among the lower branches of the animal kingdom.
The object or design in nature, at least in the case of the
plant-lice and bark-lice, as Avell as the gall-flies, is the pro-
duction of large numbers of individuals, by which the per-
petuity of the species is maintained.
Insects are both useful and injurious to vegetation. "Were
it not for certain bees and moths, orchids and many other
plants would not be fertilized ; insects also assist in the
cross-fertilization of plants. For full crops of many of our
fruits and vegetables, we are largely indebted to bees, flies,
moths, and beetles, which, conveying pollen from flower to
flower, ensure the production of abundant seeds and fruits.
Mankind, on the other hand, suffers enormous losses from
the attacks of injurious insects. Within a period of four
years, the Rocky Mountain locust, migrating eastward, in-
flicted a loss of $200,000,000 on the farmers of the West.
In the year 1864, the losses occasioned by the chinch-bug in
the corn and wheat crop of the valley of the Mississippi
amounted to upward of $100,000,000. It is estimated that
the average annual losses in the United States from insects
are about $100,000,000. On the other hand, hosts of
ichneumon flies and Tachina flies reduce the numbers and
prevent undue increase in the numbers of injurious insects.
The number of species of insects in collections is about
200,000. Of these there are about 25,000 species of Hytne-
noptera (bees, wasps, etc.); about 25,000 species of Lepi-
dopiera (butterflies and moths); about 25,000 Diptera (two-
winged flies), and 90,000 Coleoptera (beetles) ; with about
4000 species of Araclmida (spiders, etc.), and 800 species
of Myriupoda (millepedes, centipedes, etc.)
Insects are distributed all over the surface of the earth.
Most of the species are confined to the warmer portions of
the globe, becoming fewer in the number of species as we
approach the North Polar regions. Many are inhabitants
of fresh water ; a very few inhabit the sea.
Insects, except a Silurian Blattid, first appeared in the
Devonian rocks; these were Neuroptera and Orthoptera, with
representatives of other groups which seem generalized in
their structure. But if highly developed flying insects, be-
longing, at least the May-fly, to existing families, appeared
PERIPATUS. 335
in the Devonian period, it is reasonable to suppose that other
insects, besides forms like cockroaches, must have inhabited
the dry land of the Silurian period.
While true scorpions have been found in the Upper Silu-
rian rocks of Scotland, Sweden, and New York, the oldest
insect-remains are the wing of Palceoblattina douvillei, an
insect probably allied to the cockroach, and found in the
Middle Silurian rocks of France.
In the Devonian of St. Johns, N.B., have been discovered
fragments of the wings either of a May-fly or dragon-fly, and
five other species of doubtful position.
In the Carboniferous formation insect-remains are more
numerous; they belong to the Thysanura, Orthoptera, May-
flies, dragon-flies, Hcmiptera, with composite forms (Euge-
reon) and genuine Neuroptera, allied to tiialis and Corydalus.
No insects with a complete metamorphosis (except the Neu-
r opt era) are yet known to have lived before the Mesozoic age.
CLASS III. — MALACOPODA (Peripatus).
Characters of Malacopoda. — This group is represented by
a single animal, the strange Peripatus of tropical coun-
tries, in which the body is cylindrical, the integument, an-
tennae, and limbs soft, not chitinized, with the head not
separate from the body, and bearing a pair of many-jointed
extensible antennae, with two pairs of rudimentary jaws
(mandibles and maxilla?), and from fourteen to thirty-three
pairs of feet. There is a pair of nephridia to each segment.
It differs from other Arthropods in the two widely separated
minutely ganglionated nervous cords sent backward from the
brain; also in the minute, numerous t radical twigs arising
from numerous minute oval openings (rudimentary spiracles)
situated irregularly along the median line of the ventral
surface of the body. The feet are soft, fleshy, and end in
two claws. Peripatus is viviparous. According to the
description and figures of Mr. Moseley, the young develop
much as in the chilopodous Myriopods (Geophilus), show-
ing that Peripatus is nearer to the Myriopods than any
other group. That it is a tracheate animal was also proved
by Mr. Moseley; but owing to the nature of the nervous
system, the minute trachea? and their numerous irregular
336 ZOOLOGY.
spinicular openings, with no chitinous edge, this form cannot
be placed among the Myriopods. It is certainly not a worm,
but, on the whole, connects the worms with the sucking
Myriopods, and suggests that the insects may have descended
from forms somewhat like Peripatus. Peripatus iuUfonnis
inhabits the West Indies, and either P. Edicardsii Blanch-
ard, or an undescribed species about four centimetres in
length (with twenty-seven pairs of legs), inhabits the Isth-
mus of Panama. The name Malacopoda was proposed by
De Blainville, who suggested that Peripatus connected the
Myriopods with the Annelids.
CLASS IV. — MYRIOPODA (Centipedes, etc.).
Characters of Myriopoda. — The centipedes and millepedes
are distinguished by their cylindrical body, the abdominal seg-
ments being numerous and similar to the thoracic segments,
all provided with a pair of feet. The head bears a pair of
antennae, but the jaws are not homologous with those of in-
sects. The internal organization is simple, like that of the
larvae of insects. Some Scolopendrce are said to be viviparous.
Order 1. Diplopoda. — To this group belong the mille-
pedes, Julus, etc. (Figs. 299-302). The first maxillae are
absent. The segments are round or flattened, and the feet
are inserted near together, the sternum being undeveloped.
In some forms (Fig. 299, Scoterpes Copei Packard, from
Mammoth Cave) the body is hairy. They are all harmless.
The eggs are laid in large numbers an inch or two beneath
the surface of the earth. They undergo total segmentation,
and in a few days the larva (Fig. 300) hatches. At this time
it bears a resemblance to a Podura, having but three pairs
of feet, the third pair attached to the fourth thoracic seg-
ment. After a series of moults, new segments and new feet
appear, and thus these Myriopods undergo a distinct meta-
morphosis. The species feed on dead leaves and fruit.
Order 2. Pauropoda. — The two orders of Myriopods are
connected by Pauropus, which by Lubbock is regarded as
the type of a distinct order (Pauropoda). Our only species,
Pauropus Lubbockii Pack. (Fig. 304), consists of six seg-
ments besides the head, and the young Pauropus has but
MYRWPODS.
337
Tig. 299.— Scoter-
pes copei of Mam-
moth Cave.
Fig. 300.— Larva of
J'/lits. a, third ab-
dominal segment, with
the new limbs just
budding out ; 6, new
segments arising be-
tween the penultimate
and the last segment. —
After Newport.
Fig. 301.
—Polydes-
tntts ery-
thropygug
—common.
Polydes-
mus.
Fig. 302. —Polydesmus cavicola, from Utah
top and side view. a. antenna ; 6, a segment
and leg; c, dorsal view of two segments show-
ing ornamentation ; rf, side view of two terminal
segments of the body— all magnified.
Fig. m.-
Natural size.
338
ZOOLOGY.
three pairs of feet, and in this and other respects resembles
Podura. A second form, Eurypauropus, of Ryder, has six
segments, with nine pairs of feet wholly
concealed from above by the expanded seg-
ments. The antennae end in a terminal
globular hyaline body with a long pedicel,
as in Pauropus, and the mouth-parts are
as in that genus. E. spinosiis Ryder is
reddish brown, and one mm. in length.
Order 3. Chilopoda. — This group is rep-
resented by the centipede and Lithobius,
in which the body is flattened, the sternal
region being well developed. In Geophilus
(Fig. 303, G. bipuncticeps Wood) and allies
there are from thirty to two hundred seg-
ments. Our most common form is Litho-
bius Americanus Newport, found under
logs, etc. The centipede (Scolopendra
heros Girard) is very poisonous, the poison-
sac being lodged in the two large fangs or
{tried vSw! o3f°5heead ni'st pair of legs. In Cermatia the body is
pair o?lf eet* and first snoi'tj with compound eyes and remarkably
long slender legs. C. forceps Rafinesque, of
the Middle and Southern States, is said to be poisonous; it
preys upon spiders. (Wood's Myriopoda of North America,
1865.)
CLASS V. — AKACHNIDA (Spiders, etc.).
Characters of Arachnida. — The bodies of spiders and scor-
pions, etc., are divided into two
regions, a head-thorax and abdomen,
the head being closely united witli
the thorax. There are no antennae,
only a pair of mandibles and a pair
of maxillae, with four pairs of legs.
There are never any compound eyes.
The young are usually like the adult,
except in the mites, in which there
is a slight metamorphosis. In all
Arachnida there is a liver, this organ not being present in
the winged insects.
Fig. 305.— Head of Pauropus
Luhbockii. Much enlarged.
Fig. 305a.— 1, the common garden-spider (Epeira): a, leg; 6, maxillary
palpus; c, poison-jaws; e, spinnerets. 2, Front view of head with the eight sim-
ple eyes and the poison-jaws. 3, end of a jaw: a, outlet of the poison-canal.
7, palpus of female; 8, of a male spider. 6, spines and claws at end of a leg.
4, spinnerets, highly magnified. 5, a single silk-tube.— After Emerton.
Fig. 3056.— Structure of a centipede. A, Lithobius americanus, natural size.
B, under side of head and first two body-segments and legs, enlarged: ant, an-
tenna: 1. jaw; 2, first accessory jaw; c, lingua; 3, second accessory jaw and
palpus; 4, poison-jaw. (King-sley del.) C, side view of head (after Newport):
ep, epicraniuin; I, frontal plate; sc, scute; p, first leg; sp, spiracle.
[To face page 338.]
PYCNOGONIDA.
339
The type of this class is the spider, which is character-
ized by the pos-
H _Rii session of two
or three pairs
of spinnerets,
which are
jointed a p -
pendages ho-
mologous with
the legs. Be-
sides tracheae,
spiders have a
so-called
306,
la.
lung
Fig. 366.— Anatomy of a spider, diagrammatic longitudinal
section through the body. «?/, simple eyes and nerves leading
to them from the brain (supra-eesophageal ganglion, oCf) ;
«»2, mandibles ; ta», palpus of maxilla I, ; /,, first pair of legs, p n in r> n <? P f\ of
6,~*3, succeeding pairs ; A', head ; Br. thorax ; H, hind-body
or abdomen; ft a, heart or dorsal vessel; L, lung in front of several leaves,
the opening of the oviduct G ; the spinning-glands (.9/7) con- . .
nect with the spinnerets, sp W. The digestive tract is chaded, into Which the
and in the abdomen enveloped in the liver.— After Graber. n n
blood flows,
and is thus aerated. In Lycosa the blood flows through the
heart from the head backward. There is a great range of
structure, from the lowest mites to the spiders, certain mites
having no heart, no tracheae, very
rudimentary mouth-parts, and no
brain, there being but a single
ganglion in the abdomen.
Order 1. — The Pycnogonida
are marine forms, without air-
tubes, with four pairs of long
legs, into which coecal prolonga-
tions of the stomach pass, as seen
in Fig. 307.
Order 2. Tardigrada*—The
bear animalcules (Fig. 308) are
related to the mites. In these
Fig. 307. — Ammothoi? pycnogo-
noides. a, stomach with coaca (6,
6, 6, 6) extending into the legs. —
From Gegenbaur.
singular beings the ovary and
testis exist in the same individual.
Macrobiotus Americanus Pack, is common in sphagnum
swamps. Like the Rotatoria, these low forms are capable
of revivifying after being apparently dead and dried up.
f The Pycnogonida, Tardigrada, and Linguatulina are probably
independent classes of Arthropods.
340
ZOOLOGY.
Order 3. Linguatulina. — This group comprises remark-
able worm-like forms, which are parasites. The young are
mite-like, the body spherical, with boring jaws, and two
Fig. 308. — Milnesium tardigradum, X
120 times. 7, mouth-parts; 6, alimentary
canal ; ov, ovary.— After Doyere.
Fig. 309. — Pentastoma tcenioides.
Natural size.— From Verrill.
Fig. 310.— Ixodes albipicmsfrom a partly
domesticated moose. The tick natural
size, gorged with blood, and its six-legged
young, niiu'li enlarged, a, beak or man-
dibles armed with teeth; b, maxilla, and
c, maxillary palpus: d, a foot with sucker
aud claws, enlarged.
Fig. 311.— Ixodes bovis. Natural size
and enlarged.
THE MITES.
341
pairs of short-clawed feet. Pentastoma (Fig. 309) occurs in
the lungs and liver of man, and in horses and sheep.
Order 4. Acarina. — The mites are degenerate Arach-
nid a, the body being oval in form,
the head usually small, more or
less merged with the thorax, while
the latter is not differentiated
from the abdomen. There is a
slight metamorphosis, the mite
when first hatched having b
three pairs of legs, the fourth
Fig. 319.— Sugar-mite,
enlarged.
Much
Fig. 313.— Carolina scorpion (Buthus
Carolinianus). Natural size.
(and last) pair being added after a moult. A typical mite,
though above the average size of the members of the group,
is the tick (Fig. 310, Ixodes albi-
pictusP&ck). Closely allied to this is
Ixodes bovis Riley, the cattle-tick
(Fig. 311), which buries its head in
the skin, anchoring itself firmly by
means of the backward-pointing teeth
of its jaws. Other examples of mites
are the cheese and sugar mites (Fig.
312, Tyroglyphus sacchari}. The lat-
ter appear as white specks in sugar,
and to them is due the disease known
as grocers' itch. Certain mites live
under the epidermis of the leaves of
trees, often forming galls.
Fig. 3U.—Chelifer cancroi-
des. Magnified.
342 ZOOLOGY.
Order 5. Arfhrogastra. — In tins group belong scor-
pions (Fig. 3K>). false scorpions (Fig. 314), the whip scor-
pions, and the harvest-man (Phalangium). In all these
forms the abdomen is plainly segmented, the segments not
being visible in the mites or spiders. Usually the maxillary
palpi are much enlarged, and end in claws. The scorpion
is viviparous, the young being brought forth alive. The
young scorpions cling to the back of the mother. The sting
of the scorpion is lodged in the tail, which is perforated,
and contains in the bulbous enlargement an active poison.
Though producing sickness, pain, and swelling in the arm,
the sting of the scorpion is seldom fatal.
The little false-scorpions (Chelifer, Fig. 314) often occur in
books, under the bark of trees, and under stones. The whip-
scorpion is confined to warm countries. Tlielyphonus gigan-
teus Lucas occurs in New Mexico and Mexico. Its abdomen
ends in a long lash-like appendage. Its bite is poisonous.
The harvest-men, or daddy-long-legs, are common in dark
places about houses. They feed on plant-lice. Our common
species is Phalanyinm dorsatum Say.
Order 6. Araneina. — The spiders are always recogniza-
ble by their spherical abdomen, attached by a slender pedicel
to the head-thorax. They breathe, like the scorpions, both
by lungs as/well as by trachea?, and the young resemble the
parent in having four pairs of feet.
The development of the spider has some peculiarities not
found in the higher insects. The egg undergoes total scsr-
O OO O O
mentation. The germ is somewhat worm-like, as in Fig.
315, then, as in C, the primitive band forms, with head and
tail end much alike. Afterward (Fig. 316) the head ac-
celerates in development, and the appendages begin to bud
out, six pairs of abdominal limbs appearing and then totally
disappearing, except the three pairs of spinnerets, as if the
spiders were descended originally from some Myriopod-like
form. The mandibles are vertical, and end in hollow points,
through which the poison exudes, the two poison-glands
being situated in the head. The male spider is usually
much smaller than the female ; the latter lay their eggs in
silken cocoons. The tarantula (Lycosa] usually lives in
TRAP-DOOR SPIDERS.
343
holes in the ground, and sometimes conceals the opening by
covering it with a few dead leaves. Our largest spider is
Nephila plumipes of the Southern States. The common
garden spider is Epeim vulgaris Hentz. It lives about
BAG
Fig. 315.— Development of the Spider.— A, worm-like stage ; B, primitive band ;
€, tlfe same more advanced, with rudiments of limbs.
houses and in gardens ; its geometrical web is very regular.
The large trap-door spider (Mygale) has four lung-sacs in-
stead of two, as in the other spiders, and only two pairs of
spinnerets. Mygale Henzii Girard
inhabits the Western plains and
Utah ; Mygale avicularia Linn, of
South America is known to seize
small birds, and suck their blood.
There are probably about six or
eight hundred species of spiders
in North America ; their colors
are often brilliant, and sometimes,
from the harmony in their colora-
tion with that of the flowers in
which they hide, or the leaves on
which they may rest, elude the
grasp of insectivorous birds.
In their instincts and reasoning
power, spiders are quite on a level with the insects, as
proved by their nest- and web-constructing abilities.
Fig. 31G. — Embryo Spider, still
more advanced. This and Fig. 315
after Claparede.
ZOOLOGY.
CLASS VI. — INSECTA.
General Character of Insects. — The triregional division
of the body is better marked in the genuine winged insects
than in the Myriopods and spiders. They usually have com-
pound as well as simple eyes; usually two pairs of wings;
three pairs of thoracic legs; often a pair of jointed abdomi-
nal appendages, besides an ovipositor or sting which mor-
phologically represents three pairs of abdominal legs.
Order 1. Titii*tniura. — The spring-tails (Pod lira) and
bristle-tails (Lcj>is»ia) represent this group. They are wing-
less, with some affinities to the Myriopods; and the typical
form Campodea (Fig. 319) is regarded as the ancestral form
of the six-footed insects, as it is a generalized
type, and forms like it may have been the
earliest insects to appear.
In Podnra, the spring-tail, and also in
Smynthurus (Smyntlmrus quadrisignatus
Pack., Fig. 317), the characteristic organ is
a forked abdominal appendage or "spring,"
held in place by a hook; when released the
spring darts backward, sending the insect
Fig. 317.-Smyn- , .
thurus, a spring- high 111 the air.
Our commonest Poduran is Tomo<-<'nix
plumbciix Linn. (Fig. 318), found all over the northern
hemisphere, in North America and Europe. The snow-flea,
Aclionitcx nivicola Fitch, is blue-black, and is often seen
leaping about on the snow in forests.
The Pod u ran s belong to the suborder CollemMa • ; the
higher forms, which bear a greater resemblance to the larvae
of Neuropterous insects and to the young cockroach, are
the ('in iint. ticolopendrella, with its well-developed ab-
dominal legs, represents the suborder $y>nj>hyla.
In the group Cinura there is no spring, but the tail ends
in two or three bristles; and in MacJt.il is, the highest form,
there are compound eyes. In all there are jointed abdominal
appendages, which structures are unique among Hexapodous
insects. Campodea slapliylinus (Fig. 319) is a small white
DERMAPTKRA AND ORTHOPTERA.
345
slender form, with long, many-jointed antennae, and two
long, slender, jointed caudal ap-
•f pendages. It lives under stones,
and C, Cookei lives in Mammoth
Cave.
Order 2. Dermaptera. - - The
earwigs (Forficulu) have a flat
Fig. 318.— A Poduran (Tomocerus) and its scales. Much enlarged.
body, ending in a forceps; while the
fore-wings are small, the large hind-
wings being folded under them.
Order 3. Orthoptera*— T\\e insects
of this group, so called from the
straight-edged fore- wings of the grass-
hoppers, locusts, crickets, etc., are
characterized by their net -veined
wings and incomplete metamorphosis.
Organs of hearing may be situated
either on the fore- legs, as in the green
grasshoppers, katydids, or at the base
of the abdomen, as in the locusts.
Most Orthoptera have a large ovi-
positor, by which they burrow in the
earth or into soft wood, and deposit
their eggs singly or in masses. Mautis
(Fig. 320) lays its eggs in a cocoon-
like mass.
Fig. 319.— Campodea.
mandibles; b, maxilla.
Many Orthoptera, as the crickets, green grasshoppers,
* See Reports 1-3 of U. S. Entomological Commission, with plates.
ZOOLOGY.
katydids, etc., and locusts, produce loud, shrill sounds,
which are sexual calls. They stridulate in three ways — i.e.,
first, by rubbing the base of one wing-cover on the other
(crickets and green grasshoppers); second, by rubbing the
inner surface of the hind legs against the outer surface of
the front wings (some locusts); third, by rubbing together
the upper surface of the front edge of the hind wings anc|
Yig. .320.— An African Mantis, or soothsayer, with its egg-mass. —From Mon-
teiro's Angola.
the under surface of the wing-covers during flight (some
locusts).
Order 4. PA/////;/Vm. — This group comprises the bird-
lice, Psocidee, Perlidre, and white ants (Tcrmilida'). The
body is flattened, the head horizontal. The pronotum is
usually large, broad, and square. The bird-lice (MaUophaga)
are more nearly related to the wingless Psocidae, such as the
death-tick (Atropos) than to the Hemiptera, among which
they are usually placed, since their free jaws and mouth-
parts generally are like those of the Psocidge. They prob-
WHITE ANTS.
347
ably form a suborder of Platyptera. In the larval and
pupal Perla (Fig. 321), tufts of gills are situated on the
under side of the prot borax, and in the
adult winged Pteronarcys these gills are
retained.
The white ants top the Platypterous
series; they live in stumps and fallen
trees, and in the tropics do much harm
by undermining the sills of houses, and
destroying furniture, books, etc. The
colonies are very large and populous.
m i • ^ ! Fig. 321.— Perla, larva.
In our Termes flavipes there are males
and females, workers and soldiers; the workers being small,
ant-like, with small round heads, while the soldiers have
Fig. 3-.J2.— Pupa of a Drag-
on-fly (Eschna).
Fig. 323. — Agrion, natural size, and o, its
larval gill, much enlarged.
large square heads, with long jaws; the pupae are active.
Fritz M tiller found in Brazil that one species of Termes was
differentiated into six different kinds of individuals: viz., a
set of winged and wingless females; winged and wingless
males; workers and soldiers. A male always lives with a
female, and a wingless male and female may, on the death
of a winged normal male and female, replace them. He
348
ZOOLOGY.
found a male (king) living with thirty-one complemental
females.
Order 5. Odonata. — Here belong the dragon-flies, in
which the prothorax is remarkably small, the thorax nota-
ble for the great development of the side-pieces, the dorsal
pieces being rudimentary. The wings of both
pairs are large, of nearly equal size, and finely
net-veined. The larvae are all aquatic, some of
them having gills (Fig. 323, a) at the end of the
body.
Order 6. Plectoptera. — The May-flies have
rudimentary mouth-parts; while the hind-wings
are small, sometimes wanting, and the hind-body
ends in three long filaments. The larvae are
aquatic and breathe by gills placed on the sides
of the hind-bod v.*
Fig. 3SJ4.— May-fly and larva, the latter enlarged.
Fig. 325.— Thrips.
Order 7. Thysanoptera. — This group is represented by
Tlirips, and belongs nearer to the Hemiptera than any other
order. The mouth-parts are united to form a short conical
sucker. The mandibles are bristle-like, bulbous at the base,
and situated inside of the maxilla?, which are flat, triangular,
witli palpi shorter than those of the labium. The wings are
narrow and fringed, sometimes wanting; the pronotum is
large, and the two-jointed feet are swollen at the ends, being
without claws. The metamorphosis is incomplete; the pupa
is active, its limbs and wings encased by a membrane, and the
antennas are turned back on the head.
Order 8. Hanfpfcra. — Insects of this group are called
* See Eaton, Monograph of Ephemeridse.
11EM1PTERA.
349
bugs. They all have sucking mouth-parts, the mandibles
and first maxillas being bristle-like, and ensheathed by the
labium or second maxillae. Their metamor-
phoses are incomplete, the larva being like
the adult, except that the wings are absent.
Many bugs secrete a disagreeable fluid from
glands seated in the metathorax. The lice
O
are low, wingless parasitic Hemiptera. The
squash-bug (Fig. 326, Coreus tristis) and
chinch-bug (Blissus leucopterus Uhler) are
types of the order.*
While most insects live but a year or two,
or three at the most, the seventeen-year locust (Cicada sep-
temdecim Linn., Fig. 327) lives over sixteen years as a larva,
Fig. 326.- Coreus
tristis, squash-bug.
Fig. 327.— Seventeen-year Locust. «, 6, pupa; d, incisions for eggs.— After Riley.
finishing its transformations on the seventeenth; there is
also, according to Riley, a thirteen-year variety of this
species.
The froth insect (Ptyelus lineatus) abounds on grass in
early summer. The cochineal insect (Coccus cacti) belongs
to the CoccidcB, or bark-lice; the dried female is used as
a dyestuff, and abounds in Central America.
* See works by Amyot et Servillc, Say, Uhler, Riley, Comstock, etc.
350
ZOOLOGY.
The plant-louse (Fig. 330, Aphis mali Fabr.) is provided
with two tubes on the hind-body from which honey-dew
drops, which attracts ants, wasps, etc. In summer the
Fig. 3-28.— Cochineal in-
sect, male; female natural
size and enlarged.
Fig. 329.— Apple Aphis. Natural size and
enlarged.
plant-lice reproduce asexually, and as there may be nine or
ten generations, one virgin aphis may become the parent of
millions of children and grandchildren.
Order 9. Neuroptera. — We now come to insects with a
complete metamorphosis. All the foregoing orders are
ametabolous, the species
passing through an incom-
plete metamorphosis, the
Fig. 830.-Cftry8opo and group of stalked larV9e resembling the adult.
e8gs- This order is now restricted
to those net-veined insects with a complete metamorphosis,
the mouth-parts free, adapted for biting, with the ligula
entire and large, broad, flat, and rounded, while the pro-
thorax is large, broad, and square. The group comprises
the SialidcB (Gorydalus) and the Hemerobiidce (Chrysopa,
Mantispa, Rhaphidia, and Hemerobins)*
Order 10. Mecoptera. — The scorpion-flies are represented
by a single family (Panorpida?), with the typical genera
Panorpa and the wingless Boreus. They are net-veined
insects, but differ from the Neuroptera in the caterpillar-
like larvae and in the imagines having a minute rudimentary
ligula, the head being elongated, with minute mandibles
at the end of the snout. The maxilla? are long, and connate
with the labium.
Order 11. Trichoptera. — The group of caddis-flies, whose
* See Hagen's Synopsis of North American Neuroptera.
MEG AFTER A.
351
cylindrical larvas are called case-worms, differ from the
Neuroptera in features which ally them to the Lepidoptera.
The mandibles are obsolete, but well developed in the larva
Fig. 331.— Mantispa interrupta Fig. 332.— Fresh- Fig. 332a.— Larva of the
Say; and side view of the same ]y hatched larva of same, but older, before the
without wings. Natural size. — Mantispa styria- first moult. Enlarged. —
Emerton del. ca. Enlarged. After Brauer.
Fig. 333.— Panorpa.
Fig. 334.— Case-woim;
a, its case.
and pupa; the maxillae are connate with the labium, while
the palpi of both pair are well developed. The general
proportions of the head and body and of the legs are much
as in the Tineid moths.
352
ZOOLOGY.
Order 12. Coleoptera. — The beetles form a homogeneous
and easily circumscribed group, all having the fore-wings
thickened, not used in flight, and forming sheaths (elytra
Fig. 335 — Pine weevil, a, larva ; b, pupa.
or wing-covers) for the hinder pair. The mouth-parts are
free and adapted for biting. The metamorphosis is com-
plete. The young or larvaa of beetles are called grubs.
Examples of beetles and their transformations are the pine
Fig. 336 —June Beetle and its transformations. 1, pupa; 2, larva.— After Riley.
weevil (Fig. 335, Pissodes sirobi Peck) and the June beetle
(Fig. 336, Lachnosterna fusca Frohl.). The oil beetle is
remarkable for passing through three larval stages (Fig.
OIL BEETLE.
353
337, Meloe angusticollis Say), the first larva being minute
and parasitic on bees, sucking their blood, while in the
Fig. 337.— Oil Beetle, a, first larva ; 5, second larva ; c, third larva ; d, pupa.
second and third stages it feeds on the pollen mass designed
for the young bees.
Fig. 338.- Stylops childreni, male, dorsal and side view. Much enlarged.
The blister beetles (Lytta marginata) undergo a similar
series of transformations called a hypermetamorphosis.
354
ZOO LOG Y.
The most aberrant of beetles is Stylops (Figs. 338 and 339,
S. childreni AVestwood), the male of which has minute fore
Fig. 339. — Stylops childreni. female.
»., parasitic in the abdomen of a bee ;
b. top view of the same. Much en-
larged.
Fig. 340.— Astraptor illuminator, larva.
Fig. 342.— The early stages of the common House-fly. .4, dorsal and side Yiew of
the larva ; a, air-tubes : sp, spiracle. 0, the spiracle enlarged. F, head of the same
larva, enlarged ; bl, labrum (?); ?nd, mandililot- ; mx, maxilla; ; at, antennie. E, a
terminal spiracle much, enlarged. D, pupanum ; sp, epirac.e. All the figures much
enlarged.
wings. The female is wingless, grub-like, imperfectly de-
veloped, and is viviparous, the young issuing from her body
THE HOUSE-FLY
355
in all directions. A few beetles are phosphorescent. Such
are the fire-flies, the cucuyo of the "West Indies, the glow-
worm, and certain grubs, such as Astraptor illuminator
(Fig. 340), Melanactes, and the young of a snapping beetle.
Fig. 343.— Bot-fly of the ox and its larva.
Order 13. SipTionaptera. — The fleas (Fig. 341) are wing-
less, with sucking mouth-parts; all the palpi four-jointed.
Order 14. Diptera. — The common house fly (Fig. 342) is
a type of this division, all the members of which have but
two wings, while the tongue is especially developed for lap-
ping up liquids. The common house-
fly lives one day in the egg state, from
five days to a week as a maggot, and
from five to seven days in the pupa
state. It breeds about stables.
The Tachina-fly is beneficial to man,
from its parasitism in the bodies of
caterpillars and other injurious insects.
The bot-fly (Fig. 343, Hypoderma
lovis DeGeer) is closely allied to the
house-fly, but the maggot is much
larger. The larval bot-fly of the horse lives in the stomach,
that of the sheep in the frontal sinus.
The Syrphus flies (Fig. 344, Syrphus politus Say) mimic
wasps ; they are most useful in devouring aphides, while in
356
ZOOLOGY.
10
Fig. 341.— Metamorphosis of Sarcopxyllu )i< iitlriinx, or jigger, which lives in the toe
>f the natives of tropical America. 1, egg; 2, embryo; 8,larva; 4, cocoon; 5, pupa;
6, fecundated female ; 7, the same on the third day from its entrance under the skin
of its human host ; 8, the Fame after several days' residence in the skin of its host ;
9, fully grown female magnified four times ; 10, head of the fame still more enlarged ;
11, the female before it has entered the skin of its host ; 1~, the mouth -parts, much
enlarged ; m, mandibles ; d, maxillary palpi ; u, under-lip or labium.— After Karsteu
and (Jiiyon.
THE HESSIAN-FLY.
357
the larva state. They
may be recognized as
greenish maggots living
among groups of plant-
lice.
In the two- winged gall-
flies (Fig. 345, Cecidomyia
destructor Say, or Hes-
sian-fly) the body is small
and slender, with long
an te n n ae. The crane-flies
(Tipitla) are large flies,
standing near the head
of the order, and, like
the gall - fly, the chry-
salis has free append-
ages, there being no
pupavium or pupa-case,
as in the lower flies.
Lastly, we have the mos-
quito (Figs. 346 and 347),
whose larva is aquatic,
and breathes by a process
on the end of the body,
containing a trachea.
Order 15. Lepidoptera.
— The butterflies and
moths form a well-defined
group, and are known by
their scaly bodies (Fig.
348), the spiral maxillae or
tongue, rolled up between
the two large labial palpi,
and their usually broad
wings. As the butterfly,
+-he type of the order, has
been described at some
length, we will only
enumerate some of the
Fig. 345.— Hessian-fly, a, larva; 6, pupa;
c, incision in wheat stalk for larva. (Mag-
nified).—After Fitch.
B
Fig. 346.—^!, larva; c, its respiratory tube.
B, pupa; d, respiratory tube; a, two paddles
at the end of the body.
Fig. 347.— Head and mouth parts of mos-
quito, e, eye; a, antennae; Ibr, labrum; h,
hypopharynx ; m, mandibles; mx, maxillae;
mxp, maxillary palpus; Ib, labium; c, cly-
peas. (Magnified.)
358
ZOOLOGY.
typical forms. The lowest group are the plume-moths
(Pterophorus), in which the wings are fissured. Above
Fig. 348. —Showing mode of ar-
rangement of the scales on the wings
of a Moth.
Fig. 349.— Angoumois, Grain Motlr
Fig. 350.— Grain Moth, Tinea grandla. a, larva ; 6. pupa, nat. size and enlarged
C, grain of wheat held together by a web.— After Curiis.
Fig. 351.— Army-worm moth, a, male; b, female; c. eye; d, male; e, portion of
female antenna; /, larva. Much magnified. — After Kiley.
them stand the clothes and grain moths (Figs. 349 and 350),
which are minute moths with narrow wings.
THE COTTON-WORM.
359
Fig. 352.— Egg, caterpillar, and moth
of Aletla argillacea, the Cotton Army-
worm.
The larger moths are represented by the canker-worm,
the grass army- worm (Fig. 351), and the cotton army- worm
(Fig. 352), so destructive to
vegetation ; the silk - worm
moth (Bombyx mori Linn.),
of the Old World, and the
American silk-worm (Telea
Polyphemus Linn.). Certain
species of the silk - worm
family, called basket-worms
((Eceticus), live in cases con-
structed of short or long strips
(Fig. 353. Our native species
is Thyridopteryx ephemercefor-
mis Haworth.
The hawk-moths (Sphinx) are distinguished by their
large size and very long tongue. The butterflies differ from
the moths in having knobbed anten-
na?, while the chrysalides are often
ornamented with golden or silvery
spots.
Order Ifi. 3ymenoptera.—TFhe bees
stand at the head of the insect series
in perfection and specialization of
parts, especially the organs of the
mouth, and from the fact that in the
course of the metamorphosis from
the larva to the pupa the first ab-
dominal segments become transferred
to the thorax — a striking instance of
the principle of transfer of parts
head ward. In the large head, spheri-
cal thorax, and short, conical abdo-
men, the bees are opposed to the
dragon-flies and other Neuroptera,
in which the abdomen is long, the
thorax composed of three homogene-
ous segments, and the mouth-parts only adapted for biting.
In the bee there is a marked differentiation of the parts of
Fig. 353.— Cases of African
Basket-worms. Natural size.
SCO ZOOLOGY.
the first and second maxillae ; the tongue or fleshy prolonga-
tion of the second maxilla; (labium, see Fig. 354, </) being
very long and adapted for lapping up liquid food in the
bottom of flowers.
The Hymenoptera are represented by the saw-flies, the
gall-flies, the ichneumon-flies and the ants, the sand- wasps,
mud-wasps (Fig. 363), paper-making wasps, and bees.
The lowest family is the Uroceridce, or horn-tails (Fig.
355, larva of Tremex columla Linn.), whose fleshy white
Fig. 354 — Side view of the front part of the head of the Humble Bee. a, clypeus
covered with hairs; b, labrum ; c, the fleshy epipharynx partially concealed by the
base of the mandibles (il); e, lacinia or blade of the maxillse, with their two-jointed
palpi (/) at the base ; j, the labium to which is appended the ligula (iy) ; below are
the labial palpi ; /*, the two basal joints ; k, compound eyes.
larvae bore in trees. The adults are large, with a long, saw-
like ovipositor. In the saw-flies (Tenthredimdce, Fig. 356,
the pear-slug, Selandria cerasi Peck) the larva strongly re-
sembles a caterpillar, having eight pairs of abdominal feet.
The gall-flies (Fig. 357, Cynips) are small Hymenoptera
which lay eggs in the leaves or stems of the oak, etc., which,
from the irritation set up by their presence, causes the de-
formation termed a gall.
HABITS OF ANTS.
The ichneumon-flies (Fig. 358) are very numerous in spe-
cies and individuals ; by their ovipositor, often very long,
they pierce the bodies of caterpillars, inserting several or
many eggs into them ; the larvae develop feeding only on
the fatty tissues of their host, but this usually causes the
death of the caterpillar before its transformation. Certain
minute species, with veinless wings (Fig. 359, Platyyaster),
of the canker-worm eggs, are egg-parasites, ovipositing in
the eggs of butterflies, dragon-flies, etc.
Fig. 355. —Horn-
tail : larva of Tre-
mexcohimbu. Nat.
size.
Fig. 357.— Gall-fly of oak.
Fig. 358.— An Ichneumon-fly.
Fig. 356.— Pear Slug,
natural size, gnawing
leaves. a, larva en-
larged ; b, the fly.
Fig. 359.— Egg parasite of Canker,
worm. Highly magnified.
The family of ants is remarkable for the differentiation
of the species and the consequent complexity of the colony,
the division of labor and the reasoning powers manifested
by the workers and soldiers, which, with the males and
females, constitute the ant-colony.
Certain ants enslave other species ; have herds of cattle,
the aphides ; build complicated nests or formicaries (Fig.
361), tunnel broad rivers, lay up seeds for use in the winter-
362
ZOOLOGY.
time, are patterns of industry, and exhibit a readiness in
overcoming extraordinary emergencies, which show that
->
Fig. 300.— (Ecodoma, or Leaf-cutter Ant of Nicaragua.— After Belt.
they have sufficient reasoning powers to meet the exigencies
•of their life ; their ordinary acts being instinctive — namely,
Fig. 361.— Diagram of an ant's nest (CEcodoma), the chambers below containing
the unt food.— After Belt.
the results of inherited habits. The leaf-cutter ants of
Central and South America (Fig. 360) are famous from
MUD- WASPS.
363
their leaf-cutting habits ; the soldiers have large triangular
heads, while the workers have much smaller rounded heads.
Fig. 362 represents a species of Eciton.
Fig. 362. -Eciton.
Fig. 363.— Mud-dauber.
The mud-daubers (Pclopceus, Fig. 363) build their nests
against stone walls, of pellets of mud, while the sand- and
mud-wasps dig deep holes (Fig. 364, Sphex ichneumonea
Fig. 364.— Sand-wasp (Sphex). Natural size.
Linn.) in gravelly walks, and have the instinct to sting
grasshoppers in one of the thoracic ganglia, thus paralyzing
the victim, iu which the wasp lays her eggs ; the young
364
ZOOLOO Y.
hatching, feed upon the living but paralyzed grasshoppers,
the store of living food not being exhausted until the larval
wasp is ready to stop eating
and finish its transformations.
The genuine paper-making
wasps are numerous in species;
here the workers are winged,
and only differ from the
females or queens in being
rather smaller and with unde-
veloped ovaries. The series of
genera from Odynerus, which
builds cells of mud, and in
which there are no workers,
up to those which have work-
ers and build paper cells, such
as Polistes, is quite continu-
ous. The genuine paper-
making wasps, such as Vespa,
build several tiers of cells, ar-
ranged mouth downward, and
enveloped by a wall of several
thicknesses of paper. In the
Vespce, the females found the
colony, and raise a brood of
workers, which early in the
summer assist the queen in
completing the nest.
The bees also present a
gradual series from those
which are solitary, living in
holes in the earth, like the
ants (Fig. 365, nest of An-
Fig. 365.-Nest of Andrena. a, level ftrena ricind Smith), and fomi-
of ground ; a, first-made cell, con-
taining a pupa; 6, A larvae ; e, pollen jna silk-lined earthen COOO011S,
mass with an egg laid on it; f, pollen
mass freshly deposited by the bee.— to tllOSC WUlCh are SOCUil, Wltll
Emerton del. . •. i • i J.T j • j?
winged workers, slightly dif-
fering from the queens. The queen humble-bee hybernates,
and in the spring founds her colony by laying up pellets of
CLASSIFICATION OF INSECTS. 365
pollen in some subterranean mouse-nest or in a stump, and
the young hatching, gradually eat the pollen, and when it
is exhausted and they are fully fed, they spin an oval cylin-
drical cocoon ; the first brood are workers, the second males
and females. The partly hexagonal cells of the stingtess
bees of the tropics (Melipona) are built by the bees, while
the hexagonal cells of the honey-bee are made by the bees
from wax secreted by minute subcutaneous glands in the
abdomen. Though the cells are hexagonal, they are not
built with mathematical exactitude, the sides not always
being of the same length and thickness.
The cells made for the young or larval drones are larger
than those of the workers, and the single queen cell is large
and irregularly slipper-shaped. Drone eggs are supposed by
Dzierzon and Siebold not to be fertilized, and that the queen
bee is the only animal which can produce either sex at will.
Certain worker-eggs have been known to transform into
queen bees. On the other hand, worker-bees may lay
drone eggs. The maximum longevity of a worker is eight
months, while some queens have been known to live five
years. The latter will often, under favorable circum-
stances, lay from 2000 to 3000 eggs a day. The first brood
of workers live about six weeks in summer, and are suc-
ceeded by a second brood.
CLASS VI.— INSECTA.
A distinct head, thorax, and abdomen; three pairs of legs; breathing
ly trachea; usually two pairs of wings; usually with a metamorphosis,
which is either incomplete or complete,
SERIES I. Ametabola, or with an incomplete metamorphosis.
Order 1. Tliysamira. — Wingless, minute, with a spring; or ab-
domen ending in a pair of caudal stylets; usually no
compound eyes; no metamorphosis (Podura, Campodea,
Lepisma).
Order 2. Dermaptera, — Body flat ; the abdomen ending in a
forceps; fore-wings small, elytra-like; hind-wings ample,
folded under the first pair (Forticula).
3G6 ZOOLOOT.
Order 3. Orthoptera, — Wings net veined; fore-mugs narrow,,
straight, not often used in flight; metamorphosis incom-
plete; pupa active (Caloptenus, Locusta, Phaneroptera,
Acheta).
Order 4. Platyptera. — Body usually flattened; pronotum usually
large and square; often wingless (Mallophaga or bird-lice,
Perla, Psocus, white ants).
OrderS, Odonata. — Prothorax small; thorax spherical; both pairs
of wings of nearly the same size, net-veined. Larva and
pupa aquatic; labium forming a large mask (Agrion, Libel-
lula).
Order 6. Plectoptem. — Mouth-parts nearly obsolete; wings net-
veined, hinder pair small, sometimes wanting; abdomen
ending in three filaments. Larvae aquatic, with large jaws,
and with gills on the side of the bind body (Ephemera).
Order 7. Thysanoptera. — Mouth-parts forming a short conical
sucker; palpi present; wings narrow, fringed; abdomen end-
ing in a long ovipositor (Thrips).
Order 8. Hemiptera. — Mouth-parts forming a sucking beak; pro-
thorax usually large; fore-wings often thickened at base;
pupa active (Coreus, Anna, Pentatoma, Cicada, Coccus,
Aphis).
SERIES II. Metabola, or with a complete metamorphosis.
Order 9. Neuroptera. — Wings net -veined; mouth -parts free,
adapted for biting; ligula large, rounded; prothorax large,
square. Larvae often aquatic (Corydalus, Chrysopa, Myr-
meleon)
Order 10. Mecoptera. — Wings somewhat, net-veined, or absent.
Larvae like caterpillars (Panorpa, Boreus).
Order 11. Triclwptera. — Wings and body like those of moths;
mandibles obsolete in imago. Larvae usually aquatic, liv-
ing in cases (Phryganea).
Order 12. Coleoptera. — Fore-wings thick, ensheathing the hinder
pair, which are alone used in flight; mouth-parts free,
adapted for biting; metamorphosis complete (Doryphora,
Clytus, Lucanus, Harpalus, Cicindela).
Order 13. Siphonaptera. — Wingless; mouth-parts adapted for
sucking. Larva maggot-like, but with a well-developed
head and mouth-parts (Pulex).
Order 14. Diptera. — But one pair of wings; mouth-parts adapted
for lapping and sucking; a complete metamorphosis (Musca,
CEstrus, Syrphus, Cecidomyia, Tipula, Culex).
CLASSIFICA TlOX OF INSECTS.
367
Order 15. Lepidoptera. — Body and wings covered with scales;
maxillae lengthened into a very long tongue; larvae (cater-
pillars) with abdominal legs (Tinea, Geometra, Noctua,.
Bombyx, Sphinx, Papilio).
Order 16. Hymenopt&ra. — Wings clear, with few veins; mouth-
parts with a variety of functions, i.e., biting, lapping
liquids, etc. In the higher families the thorax consists of
four segments, the first abdominal segment of the larva
being transferred to the thorax in the pupa and imago.
Metamorphosis complete (Tenthredo, Cynips, Ichneumon,
Sphex, Vespa, Apis).
TABULAR VIEW OF THE SIXTEEN ORDERS OF INSECTA.
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Metabola
Thysanura.
(Cam pod ea.)
Ametdbola.
Laboratory Work. — In dissecting Myriopods, spiders, and insects, the
dorsal portion of the integument should be carefully removed with
fine scissors, leaving the hypodermis untouched; this should then be
raised, disclosing the delicate heart or dorsal vessel. The alimentary
canal will be found passing through the middle of the body; it should
be laid open with the scissors, or, better, a hardened alcoholic specimen
can readily be cut in two longitudinally, and if the section is true, the
oesophagus and crop — for example, of a locust — can be laid open, and
368 ZOOLOGf.
the rows of teeth examined. The thoracic and abdominal portions of
the nervous system, which lies loosely on the floor of the body, can be
readily found by raising the alimentary canal ; but the brain and infra-
<eK>phageal ganglia can best be detected by a longitudiual section of
the head. The ovaries always lie above the intestine, and the two
oviducts unite below the nervous cord to form the common duct which
opens on the ventral side of the third segment in front of the anus,
which is situated dorsally. Insects should be dissected in a shallow
pan lined with wax or cork, and the parts floated out ; fresh specimens
are desirable. The body may also be dissected, each segment with its
appendages being separated and glued in their true sequence to a card.
By simply dissecting an insect in this way, the student will acquire a
valuable knowledge of the external structure of insects.
LITERATURE OF ARTHROPODA.
Crustucea. — Milne-Edwards's Histoire Naturelle des Crustacea. 3
•vols. , 1834-1840. Dana's Crustacea of the U. S. Exploring Expedi-
tion. 2 vols., 1852. Gerstaecker's Arthropoden (in Bronu's Classen
und Ordnuugen des Tbierreichs). 2 vols., 1866-1891. Huxley's
The Crayfish, 1880. Packard's Monograph of North American Phyl-
lopod Crustacea, 1883. Also the writings of Say, Dohrn, Sars,
Claus, Brooks, Hagen, Faxon, Smith, Kingsley, etc.
Podostoinata. — Van der Hoeven's Reckerches sur 1'Histoire Natu-
relle des Liinules, 1838. Milne-Edwards's Recherches sur 1'Anatomie
des Limules, 1872. Packard's Four Memoirs on the Anatomy and
Embr3rology of Limulus, 1872-1891. Kingsley's Notes on the Em-
bryology of Limulus, 1885. Also the essays of Walcott, Dohrn,
Brooks, Lankester, Bruce, and Kishinouye.
Arachnida. — Heutz's Spiders of the United States. Boston, 1875.
Emerton's Structure and Habits of Spiders, 1883, and his various
essays, with those of G. W. and E. G. Peckham. McC'ook's American
Spiders and their Spinning Work. 3 vols., 1889-1892. With the
works of Walckeuaer, Blackwall, Thorell, Simon, Moggridge, Bert-
kau, Keyserling, Marx, etc.
Myriopoda. — Wood's The Myriopoda of North America, 1865. With
essays by Newport, Harger, Latzel, Haase, Packard, etc.
Insecta. — Kirbyaud Spence's Introduction to Entomology. 4 vols.,
1828. Burnieister's Manual of Entomology, 1836. Westwood's Mod-
ern Classification of Insects. 2 vols., 1839-1840. Harris's Treatise on
Insects injurious to Vegetation, 1886. Packard's Guide to the Study
of Insects, 1888. Packard's Entomology for Beginners. New York,
1890. Graber's Die Insekten, 1877. Kolbe's Einfiihrung in die
Kenntuissderlnsekten, 1889-1892. Lubbock's Ants, Bees, and Wr.sps,
1882. For economic entomology, the works of Harris, Fitch, Kiley,
Le Baron, Lintner, etc.; also for journals, Insect Life, Washington;
Psyche, Cambridge, Mass.; Canadian Entomologist, etc.
CHAPTER VIII.
BRANCH VIII.— VERTEBRATA.
General Characters of Vertebrates. — The fundamental
characters of the Vertebrates are the possession of a
segmented vertebral column, enclosing a nervous cord, and
a skull which contains a genuine brain; yet these features,
though common to most Vertebrates, are wanting in the
lancelet (Ampliioxus) and in a degree in the hag-fish, and
even the lamprey ; but the essential character is the division
of the body-cavity by the notochord (in the lancelet, etc.),
or by the back-bone of higher Vertebrates into two sub-
ordinate cavities, the upper (neural) containing the nervous
cord, and the lower (enteric) the digestive canal and its ap-
pendages and the heart. These are the only characters which
will apply to every known Vertebrate animal (compare p. 206
with Figs. 366, 370, and 371).
In general, however, the Vertebrates are distinguished
from the members of the other branches by the following
characters : they are bilaterally symmetrical animals, with a.
dorsal and ventral surface, a head connected by a neck with
the trunk ; with two eyes and two ears, and two nasal open-
ings, always occupying the same relative position in the head ;
an internal cartilaginous or bony, segmented skeleton, con-
sisting of vertebrae, from the bodies of which are sent off
dorsal processes which unite to form a cavity for a spinal
cord, the latter sending off spinal nerves in pairs * correspond-
ing to the segmentations (vertebra?) of the spinal column.
* Except in Amphioxus, in which the spinal nerves arise right and
left alternately.
370
ZOOLOGY.
From the underside of the vertebrae are sent off processes
articulating with the ribs, which enclose the digestive and
central circulatory organs. There is a skull formed by a con-
tinuation of the vertebral column, enclosing a genuine brain,
consisting of several pairs of ganglia. To the vertebral col-
umn are appended two pairs of limbs, supported by rays ir-
regularly repeated, or a series of bones of a definite number^
Fig. 3oO.— Transverse section of a worm, of Amphioxns, and of a Vertebrate con-
trasted. «, outer or skin layer ; 6, dermal connective layer ; c, muscles ; d, eeg-
mental organ : h, arterial, and i, venous bloud-vessel ; g. intestine ; /, notochord. —
After Haeckel.
attached to the vertebral column by a series of bones called
respectively the shoulder and pelvic girdle.
It will be observed that the fact of segmentation, so prom-
inent a feature in the Worms and Arthropods, survives, or at
least reappears in a marked degree in the Vertebrates, as-
seen not only in the vertebral column, but in the arrangement
of the spinal nerves. It is perceived also in the arrangement
of the muscles into masses corresponding to the vertebrae ;
and in the segmental organs or tubes forming the kidneys of
the sharks and rays, while segmentation is especially marked
in the disposition of the primitive vertebras of the early em-
bryos of all Vertebrates.
The digestive canal consists of a mouth with lips or jaws,
armed with teeth, a pharynx leading to the lungs ; an oesoph-
agus and thyroid gland ; sometimes a crop (ingluvies), often
a fore-stomach (proventriculus) ; a stomach and intestine,
cloaca and vent. Into the beginning of the intestine passes
a duct leading from a large liver ; a gall-bladder, usually a
pancreas, and a spleen, also communicating with the intestine.
The products of digestion do not all pass through the walls
of the stomach and directly enter the circulation, as in the
invertebrates, but there is a system of intermediate vessels
NERVOUS SYSTEM OF VERTEBRATES. 37 L
called the lacteal system or absorbents, which take up a part
of the chyle from the digestive organs and convey it to the
blood-vessels.
There is a true heart, with one, generally two, auricles, and
one or two ventricles with thick, muscular walls, and besides
arteries and veins, a capillary system, i. e., minute vessels
connecting the ends of the smaller arteries with the smaller
veins. There are no genuine capillaries in the lower animals
exactly comparable with those of the Vertebrates.
The blood is red in all the Vertebrates except the lancelet,
and contains two sorts of corpuscles, the white corpuscles
like the blood-corpuscles of invertebrates, and i ed corpuscles
not found in invertebrates, and which are said by some
authors to be derived from the white corpuscles.
While fishes and larval Amphibians breathe by gills, all land
and amphibious Vertebrates breathe the air directly by means
of cellular sacs called lungs, and connected by a trachea with
the pharynx, the trachea being situated beneath the oesopha-
gus, and the opening from the mouth into the pharynx lead-
ing into the trachea being placed below the throat or passage
to the oesophagus. The air filling the cells or cavities of the
lungs passes by osmose through the walls of the cells into the
blood sent by the heart through the pulmonary artery, and
after being oxygenated, the blood returns by the pulmonary
vein to the heart. On the other hand, carbonic acid passes
from the blood out of the lungs through the trachea.
The nervous system of Vertebrates consists of a brain and
spinal cord. The brain consists of four pairs of lobes, i. e.,
the olfactory lobes, cerebral hemispheres, the optic thalami
(Thalamencephalon) and pinealgland,*and the optic lobes; and
two single divisions : the cerebellum and the beginning of the
spinal cord, called the medulla oblongata. The olfactory lobes
are the most anterior, and send off the nerves of smell to the
nose. The cerebral hemispheres in the fishes and amphibians
are little larger than the adjoining lobes, but in the reptiles. .
become larger, until in the mammals, and especially in the
apes and man, they fill the greater part of the brain-box and
overlap the cerebellum ; the latter, in the mammals, also
exceeding all the other lobes in size, excepting the cerebrum,
* This proves to be the rudiment of the median eye.
372
ZOOLOGY.
Attached to a downward prolongation (infundibulum) of the
optic thalami is the curious pituitary body. The medulla
sends nerves to the skin and muscles, giving sensibility and
motion to the face, eves and nose, to the larynx and sensitive
' •/ •/
portion of the lungs ; a pair also is sent to the lungs and
heart. If the spinal marrow is severed, the parts below are
paralyzed ; if the medulla is cut or broken up mammals die
at once, while the lower Vertebrata die sooner or later.
The brain in an embryo originally consists of three vesi-
cles or primitive lobes ; and the correspondence between
Fig. 367.— "Diagrammatic, longitudinal and vertical section of a Vertebrate brain.
Mb, mid brain ; what lies in front of this is the fore brain, and what lies behind, the
hind brain. L, iamina terminalis ; Olf, olfactory lobes ; Hmp, cerebral hemi-
spheres ; Th E, thalamencephalon ; PH, pineal gland ; Py, pituitary body ; FM, fo-
ramen of Munro ; CS, corpus etriatum ; 7%, optic taalamus; CQ, corpora quadri-
gemina ; CO, crura cerebri ; Cb, cerebellum ; PV, pons varolii ; MO, medulla oblon-
gata; /, olfactorii ; //, optici ; III, point of exit from the brain of the Motores
oculorum ; IV, of the pathetic! ; VI, of the abducentes ; V-XII, origin of the other
cerebral nerves ; 1, olfactory ventricle ; 2, lateral ventricle ; 3, third ventricle ; 4,
fourth ventricle.— After Huxley.
the three primitive lobes, called respectively the fore, mid,
and hind brain, may be seen by the following table :
TABULAR VIEW OF THE SUBDIVISIONS OP THE VERTEBRATE BRAIN.
Olfactory lobes or ganglia, with tlieir ventricles (rhinen-
cepbalon).
Cerebrum or cerebral lobes or hemispheres (with the
c, two lateral or first and second ventricles, forming
bore brain. •( .
the prosencephalon or prothalami).
Optic thalami, with the third ventricle and couarium
above and hypophysis (pituitary body) below
(Thalamencephalon pineal gland).
NERVOUS SYSTEM OF VERTEBRATES.
373
Mid brain.
Optic lobes, corpora bigemina or quadrigemina (tnesen-
cepbalon).
Crura cerebri.
Optic ventricle or Iter a tertio ad quartum ventriculum.
I Cerebellum (witb its ventricle and the pons varolii, form-
Hind brain. \ ing the metencephalon).
I Medulla oblongata and fourth ventricle.
JU
The accompanying sketches represent the typical nervous
system of an amphibian, which also resembles that of many
fishes, and even the lower Reptilia.
The spinal cord (Fig. 368) usually
extends through the whole length of
the spinal canal, except in the toads
and frogs, birds and many mammals,
where it stops short of the end of its
canal. In those Vertebrates with
limbs, the cord enlarges where the
nerves which supply them are sent off ;
these are the cervical or thoracic, and
lumbar enlargements, especially large
in turtles and birds. The white and
gray substance of the brain continues
in the cord.
As the most essential characteristic
of Vertebrates is the internal skeleton
(endoskeleton) we will enter more into
detail in describing1 it, and afterwards
notice the external skeleton (exo-
skeleton).
In the embryos of higher Vertebrates
and in the adult lancelet, hag-fish and hemispheres ; c, 'optic lobes ;
, . «?, cerebellum in the form of a
lamprey, the vertebral column is rep- lamella bridging over the
-, i -iTi / 11 fourth ventricle (,<) ; m, spinal
resented by a I'Od-llke axis (notOChord cord; t, terminal cord.— After
or chorda dor sails) which is composed
of indifferent, or only partly organized cells, the substance
of the chord resembling cartilage. These chordal cells secrete
a membrane called the chordal sheath. The notochord is not
Pig. 368.— Brain ana spinal
cord of the frog. A, from
374
ZOOLOGY.
segmented. In all Vertebrates above the lamprey, the verte-
bral column grows around the notochord, which finally
FIG. 371.
Fig. 369.— Transverse section through the spinal cord of a calf, a, anterior, 6,
posterior longitudinal fissure ; c, central canal; d, anterior, e, posterior cornua ; /,
enbstantia gelatinosa; (/, anterior column of the white substance; h, lateral, i, pos-
terior column ; k, transverse commissures. —After Gegenbaur.
Fig. 370.— Section through the vertebral column of Ammocoetes (lamprey). Ch, no-
tochord; cs, chorda! sheath ; M, spinal chord ; a, aorta; i\ veins.
Fig. 371.— Section through the spinal column of a young salmon. Ch, notochord ;
cs, chordai sheath; m, spinal chord; k, superior, k', inferior arch (rudimentary) ; a,
aorta; v, veins.— After Gegtnbaur.
forms the central portion of the bodies of the vertebra?, and
in the higher Vertebrates is wholly effaced ; the centra or
LIMBS OF VERTEBRATES.
375
Fig. 372.— Diagram of a Vertebra
with its Dody (5), rib (7), breast-bone
(6) ; 1, neural spine; 2, 3, fore and
hind oblique processes ; 4, transverse
processes.
bodies of each vertebra of a lizard, bird or mammal being
solid bone. Figs. 370 and 371 represent the relations of the
notochord in an adult lamprey and a young fish.
The vertebra of a bony fish
or higher vertebrate consists
of a body, with a dorsal or
neural spine ; a pair of oblique
processes (zygapophyses) arching
over and enclosing the spinal
cord ; and transverse processes,
bending downwards, to which
the ribs are articulated ; certain
of the thoracic ribs uniting
with the sternum or breast-bone
(Figs. 372 and 373).
Vertebras like those of fishes,
which are hollow or concave at
each end, are said to be ampMccelous ; those hollow in front
and convex behind procoelous, as in most toads and frogs
and crocodiles, and most existing
lizards, and those convex in front
and concave behind opisthoccelous,
as in the garpike, some Amphib-
ians (the salamanders and cer-
tain toads, Pipa and Bombinator).
Vertebrates never have more
Fig. 373. — Thoracic vertebra of ,.
buzzard (Buteo vulgaris). <; centrum than tWO pail'S OI limbs, ail ail-
or body ; g, superior spinous pro- . . , n . , . ,,
cess ; tr, transverse process ; io, tenor and nmder pair ; the pecto-
rib ; a, tuberculnm of the rib : /•?. ca- •. • « n « /> i
pituium of the rib.-After Gegen- ™1 pair of fins of fishes represent
baur- the fore limbs of Amphibians and
higher Vertebrates, and the arms of man ; the two ventral
fins represent the hind legs of higher Vertebrates, and the
legs of man. Each pair of limbs is connected by ligaments
and muscles to a girdle or set of bones, called respectively
the shoulder girdle and pelvic girdle, each girdle being con-
nected by muscles to the vertebral column. The shoulder
girdle consists of a clavicle (or collar-bone), scapula (or
shoulder-blade), and coracoid bone, usually a process of the
scapula. These bones differ greatly in the different classes,
376
ZOOLOGY.
and arc reduced to cartilaginous pieces in sharks. The pelvic
girdle, or pelvis, consists of three bones, i.e., one dorsal, the
ilium, and two ventral, the anterior of which is called pubis
and the posterior ischium.
The limbs each consist of a single long bone, succeeded by
two long bones, followed by two transverse rows of short
wrist or ankle bones, and five series of long finger or toe
bones, called phalanges. For example, in the fore limb of
most Vertebrates, as in the arm of man, to the shoulder gir-
dle, i.e., at the point of junction of the three bones com-
posing it, is articulated the humerus ; this is succeeded by
376
FIG. 374.
Fio 375.
Fig. 374. —Sternum and shoulder girdle of Frog (Sana
tempararia). p, body of the sternum ; «•, scapula ; sc',
supra-scapula ; co, coracoid bone, fused in the middle line
with its fellow of the opposite side (s) ; <V, clavicle ; e, epis-
ternum. The extreme shaded double portion below p is the
Xiphisternum. The cartilaginous parts are shaded.— After
Gegenbanr.
Fig. 375.— Fore-leg of a seal. S, scapula ; ff, humerus ;
O, olecranon or tip of elbow ; S, radius ; U, ulna ; Po,
pollex, or thumb
Fig. 376.— Pelvis or pelvic bones on one side of a mai>u-
piai (Kangaroo). 62, ilium; «, situated on the pubic bone
(pubis) indicates the acetabulum or concavity for the artic-
ulation of the head of the femur; (>3, lechium, consolidated with the pubis. The
three bones thus consolidated form the os innominatam ; m, marsupial bones ar-
ticulated to the pubic boues.— After Owen.
the ulna and radius, the carpals, the metacarpals, and the fin-
ger-bones or phalanges, the single row of phalanges forming
a digit (finger or toe). To the point of union (acetabulum,
Fig. 376, #) of the three pelvic bones is articulated the fe-
mur, or thigh; this is succeeded by the tibia and fibula
(shank-bones), the tarsal (ankle-bones) and metatarsal bones,
and the phalanges or bones forming the digits (toes).
Figs. 378-380 represent the simplest form of the posterior
limbs in the higher Vertebrates, that of the bird showing an
COMPOSITION OF THE SKULL.
377
extreme modification in form. At first nil limbs arise as
little pads, in which the skeletons subsequently develop, and
in early life the limbs of all Vertebrates above the fishes are
much alike, the mod-
ifications taking place
shortly before birth. Ac-
cording to Gegenbaur
and others, the limbs of
Vertebrates have been
probably derived from
the pectoral and ventral
fins of fishes in which
the fin-rays are irrela-
tively repeated.*
In the fins of fishes
there is a simple system
of leverage ; in the limbs
of higher air-breathing Fig> 377>_^ skull . ^ vertebrffi
c, sacrum,
> >_ , ,
a fnrmpd Itv and e. its continuation (nrostyle) ;/, suprascap-
b» UJ ula; g, hiimcrus; h, fore-arm bones; i, wrist
walking O11 land, a Com- bones (carpals and metacarpus) ; d, ilium ; m
thigh (femur); n, leg bone (tibia) ; o, elongated
pOUlld System Of lever- first pair of ankle-bones itarsfil*) ; p,q, foot
J boues or phalanges.— After Owen.
age (Wyman).
The head of all Vertebrates above the lancelet is supported
by a more or less perfect cartilaginous or bone framework,
the skull (cranium), or brain-box (Fig. 381). It is a contin-
uation of the vertebral column, and protects the brain,
besides forming the support of the jaws, tongue-bone
(hyoid bone), and branchial arches. The series of lateral
(visceral or branchial) arches varies, but there may be nine ;
the most anterior (if it be counted as the first one, Fig.
382, a, b, c) is formed by what are called the labial carti-
lages; next comes the rnandibular arch (o, n}, which is suc-
ceeded by the hyoid arch (II.) and the six branchial arches.
In the embryos of all Vertebrates these visceral arches are
* A modified form of this theory is advocated by Balfour and J. K.
Thatcher, who attempt to show that the limbs with their girdles were
derived from a series of similar simple parallel rays, and that they
were originally a specialization of the continuous lateral folds or fins of
embryo fishes, and probably homologous with the lateral folds of the
adult lancelet (Aniphioxus).
378
ZOOLOG Y.
well marked ; of the slits or openings between them, the
first is destined to form the mouth, the next pair of slits
FIG. 379.
FIG. 380.
Fig 378.— Hind leg of a larval Salamander. The dotted lines are drawn through
the rays to which the different pieces belong. Fe, femur : T, tibia ; F. tibula ; i, t,
c f tarsal bones; i, os intermedium; t, tibiale ; /, flbulare; c, centrale ; 1-5, the
five tarsals. The first row of phalanges are culled metatarsals (in the hand, mctu-
Fig. 379.— Bones of the foot of a Reptile (lizard) A, and an embryo bird. B. /, fe-
mur ; t, tibia ; n. fibula ; ts, upper, ti. lower pieces of the tarsus ; m, metatarsus ;
1- V, metatarsalia of the toes.
Fig. 380.— Leg ot the Buzzard (Biitto rulr/ariit). a, femur; b, tibia ; b', fibula; c,
tarso-metatarsr.s ; c', the same piece isolated, and seen from in front; dd', d", d'",
the four digits or toes. — After Gegenbaur.
in the Amphibia and higher Vertebrates forms the ear-pass-
age, while the other slits may remain open in fishes, form-
COMPOSITION OF THE SKULL.
379
ing gill-slits or spiracles, but are closed in the higher Verte-
brates. As a rule, the skull is symmetrical, exceptions being
found in the flounders and the bones about the nose of cer-
Pig 381. -Skull of the Lion. 2, occipital condyle ; 7, Parietal bone and sagittal
crest ; 8, paroccipital ; 27', squaraosal bone ; 27, zygomatic arch ; 26, malar bone ;
11, frontal bone ; 12, post-orbital process; 15. nasal bone; 21, maxillary bone; 22,
premaxillary bone ; 32, mandible ; 3, occipital crest ; c, canine teeth ; /»'-', second pre-
molar ; nil, molar tooth.— After Owen.
tain whales and porpoises. The base of the skull is perfo-
rated for the exit of the nerves proceeding from the base of
the brain, and the hinder bone (occiput] is perforated (fora-
men magnum) for
the passage of the
spinal cord from the
medulla oblongata.
It is probable that
there is a general
parallelism between
the head of Insects
a n d Vertebrates.
While the head of Fi& 382.— Skull and vi-ceral skeleton of a Selachian
, . (diagram), on: occipital region; la, wall of the laby-
Wlllged insects, for rintl\ ; >//>. ethmoidai region ; n, nasal pit ; a, first, b, c,
,, second labial cartilage ; o, superior, n, inferior portion
example, Consists OI ot the maudibulararch/. ; //., hyoid arch; III.-V11I.
•u £ (1-6), branchial arches.— After Gegenbaur.
a certain number or
segments, homologous with those of the rest of the body,
and with mouth-parts homologous with the limbs ; so the
skull is also segmented, and an expansion and continuation
of the vertebral column. Gegenbaur even maintains that
the various arches of the head are homologous with the limbs.
01
VJ11
380 ZOOLOGY.
On the other hand, while the brain of insects is a single
pair of ganglia like those of the rest of the body, the differ-
ent ganglia forming the brain of Vertebrates are concen-
trated in the head alone ; still the different pairs of nerves
sent off from the base of the brain are homologous with
the spinal nerves, sent off at intervals corresponding to each
vertebra.
There are two theories of the composition of the skull.
That of Oken, Goethe, and of Owen, who believed that the
skulls of the bony fishes and mammals were composed of
three or four segments. . It should be noticed that these
views are based on an examination of highly specialized ver-
tebrates. From a study, however, of the more generalized
types of fishes (such as the sharks), and the embryos of ver-
tebrates belonging to different groups, the old vertebrate
theory of the skull has been discarded, and the view of Ge-
genbaur, confirmed by Salensky, is probably nearly the cor-
rect one. As stated by Gegenbaur :
1. The skull is comparable to a portion of the vertebral
column, which contains at least as many vertebral segments
as there are branchial arches. This view is borne out by the
following facts :
a. The notochord, which forms the foundation of the
vertebral column, passes through the cranium in the
same way as it passes through the vertebral column.
b. All the nerves which pass out of the base of the
skull (or that portion traversed by the notochord)
are homologous with the spinal nerves.
c. The difference between the skull and vertebral col-
umn consist of secondary adaptations to certain con-
ditions, which are external to the skull, and are
partly due to the development of a brain.
2. The skull may be divided into two regions, a vertebral
portion and an anterior evertelral portion, lying beyond
the end of the notochord.
3. The number of vertebraB which enter into the forma-
tion of the skull are nine at least (according to Salensky, in
the sturgeon, seven); the exact number is immaterial.*
* The number of mesoblastic somites concerned in the formation of
the skull is nine.
TEETH OF VERTEBRATES. 381
In the lancelet there is no skull, or even the rudiments of
one (unless the semi-cartilaginous supports of the tentacles
be regarded as such), hence the Vertebrates are divided into
the skulless or acnntiate (Acrania, represented by the lance-
let alone) and the skulled or craniate (Cnmioia}, the latter
series comprising all forms from the hag-fish to man. In
the Craniota the skulls may be, according to Gegenbaur, di-
vided into two groups. . In the hag and lamprey the noto-
chord is continued into the base of a small cartilaginous
capsule, enclosing the brain, and which represents the skull
of higher Vertebrates (Craniota). This capsule behind is
continuous with the spinal column.
With the skull of the second form two jaws are developed,
hence all the vertebrates above the hag and lamprey form a
series (Gnathostomata) opposed to the former, or Cyclos-
tomata.
In the GnatlLOstouuita there is a gradual modification and
perfection of the skull. In the sharks it may be quite sim-
ple and cartilaginous ; in the bony fishes it is highly special-
ized, consisting of a large number of separate bones. In
the Amphibians we first meet with a skull consisting of few
bones, partly comparable with those of mammals; in the rep-
tiles and birds a single condyle connects the skull and back-
bone; the lower jaw is articulated to the skull by the quad-
rate bone. A progress is seen in the mammals where the
quadrate bone forms the zygomatio process of the squamosal
bone. Now. also, the brain becoming much larger, evincing
a much higher grade of intellect, the skull is greatly en-
larged to accommodate the great increase in size of the
cerebrum and cerebellum, the perceptive and reasoning fac-
ulties predominating over those regions of the brain and
skull devoted to perceiving, grasping, and masticating the
food.
Though not properly forming part of the skeleton or de-
veloped with it, we may here consider the teeth.
The teeth of A'ertebrates are formed from the modified
epidermis and eutis, or dermis ; the former secretes the
enamel and the latter is changed into the pulp or dentine.
The simplest form of tooth is conical. In the jawless hag
there are no teeth in the lips, but a single median tooth on
382
ZOOLOGY.
the palate and two rows of comb-like tcetli on the tongue.
In the lamprey the ('(lyes of the circular mouth are provided
with circular rows of conical horny teeth. The teeth of
higher Vertebrates are derived from the cells of the mucous
membrane of the mouth, which is formed of connective tis-
sue as well as epithelium. The teeth of fishes are developed
not only in one or several rows in the lip, but may also arm
the bony projections into the mouth-cavity of the palate,
vomcr and parasphenoid bones and the hyoid and bran-
chial arches. In the Amphibia teeth survive on the palatine
and vomerine bones, more rarely on the parasphenoid ; among
the reptiles, the snakes and lizards alone have teetli on the
palatine and pterygoid bones, while in the crocodiles and in
mammals the teeth are confined to the maxillary bones. In
the geckos, snakes and the crocodiles, as well as the mam-
mals, the teeth are inserted in sockets (alveoli) of the jaw.
(Gegenbaur.)
In certain extinct birds (Odontornithes) there were teeth
in the jaws, though all existing birds are toothless. It is
said that rudimentary
teeth were found by
Geoffrey St. Hilaire in
the jaws of a parrot.
Blanchard afterwards-
found the germs of
teeth there, though
they never come
through. In the Mam-
mals the teeth are dif-
ferentiated into inci-
sors, canines, premo-
lars and molars (Fig.
383). In descriptive anatomy the teeth are for convenience
expressed b^ a formula, the number of teeth of the upper
jaws being placed like the numerator of a fraction, and those
of the lower jaw like the denominator, the initials of the
names of the teeth being placed before the figures, thus
Fig. 383.— Teeth of the Tasmanian devil. The
incisors are situated in front, of the large conical
canine teeth. 2, 3, premolars ; m, 1^4, four molar
teeth.— After Owen.
the dental formula of man is 7 ^^ , C
2-2 1-1
P - — -, M-
-2 3-3
SCALES, HAIRS, AND FEATHERS.
383
In the fishes. Amphibians and reptiles, the worn-out teeth
are replaced by a succession of new ones ; in mammals (ex-
cept cetaceans, where there is no change) there is but a single-
change, the first (milk) teeth being replaced by a second set
of permanent teeth. Tlu teeth of the lower Vertebrates
are shed while swallowing the food. In the boa (Python)
the teeth thus shed are found scattered along the intestinal
canal and are discharged with, the remnants of the food
(Wyman).
The dermal or exoskeleton consists of the scales of fishes,
reptiles and certain mammals, such as the armadillo, the
Fig. 384. — Vertical section through the skin of an embryonic shark. C, corium or
dermis ; c, c, c, 1 tyers of the corium ; d, uppermost layer ; p, papilla ; E, epidermis;
e, its layer of columnar cells; o, enamel layer. — After Gegeubaur.
feathers of birds and the hairs of mammals. Most scales
arise from dermal papillae (Fig. 384, p), and are covered over
by a layer of enamel (Fig. 384, o) developed from the epider-
mis ; so that the scales of sharks and rays, and turtles,,
arise from both the dermis and epidermis.
A hair or feather arises in the same way as a scale ; the papilla
is sunken in a pit of the dermis, the conical cap of epi-
dermis arising from it ultimately forming the hair or feather.
The plates of turtles, the scales of snakes and lizards, and
feathers of birds are epidermal. In the horns of mammals.,,
as of the rhinoceros, and the hoofs of the horse, the epi-
dermal substance is penetrated by numerous long dermal
papillae.
384
ZOO LOU Y.
The head of the sturgeon, garpike, and of other ganoid
lishes, is protected by solid dermal bones, and the shells of
turtles are dermal structures.
The color of the skin of Vertebrates is due to pigment -
granules situated either in the epidermis or derails, and in
the chameleon tlu-\
are contained in special
sacs (chromatophores)
which are under the
control of the nervous
system.
The muscular system
of Vertebrates arises
from the middle gerni-
layer (mesoderm), and
Fig. 385.— Placoid scale of dog-fish (vertical sec- ;, ,'ji, , , fUn ,-VU
tion magnified). «, enamel layer ; 6, deutiuo of the m tlle gei m tllO niUSClCS
spine on the scale.-AlU-r Owen. ]n part avise from the
primary segments indicated by the protovertebrae, while in
the adults of fishes and certain salamanders, the muscular
system is distinctly segmented, corresponding to the seg-
mentation of the ver-
tebral column, the
four lateral trunk-
muscles being divided
into a number of seg-
ments by tendinous
bands, which corre-
spond in number to
the vertebrae (Gegen-
baur).
The eye in Verte-
brates in its develop-
mentalhistory belongs
to a different type of
structure from that of
any invertebrates, nn
less it be the larval
Fig. 386.— Cyloid scale of roach, magnified, seen in
section, A, and from the surface, B.— After Owen.
Ascidians, for in both types the eye is said by Gegenbaur not
to be directly developed from the ectoderm, but from the
ETE8 AND EARS OF VERTEBRATES. 385
anterior portion of the central nervous system. The differ-
ence between the highly-developed eye of a cuttle-fish and
H bony fish, for example, consists in the fact that the rods
and cones (similar to those of the invertebrate eye) forming
a layer (the bacillar layer) behind the retina, are in the ver-
tebrate eye turned away from, while in the invertebrates they
are directed tow;ird the opening of the eye.
The ear of Vertebrates is at first a primitive otocyst, or
ear- vesicle, which is gradually cut off and enclosed, forming
a cavity of the skull. As we rise towards the mammals, the
ear becomes more and more developed until the inner,
middle, and outer ear is formed ; the Eustachian tube being a
modification of the first branchial cleft, forming the spiracle
in the sharks (Selachii) and Ganoids.
In the lancelet a head is scarcely more set apart from the
rest of the body than in many invertebrates. In the fishes
and Amphibians the head is not separated by a neck from
the trunk ; in reptiles the neck begins to mark off a head
from the thorax, while in the birds and mammals the head
is clearly demarked, the degrees of cephalization and trans-
fer headward of those features subordinate to the intellec-
tual wants of the animal becoming more striking as we
ascend through the mammalian series to the apes, and finally
man.
The development of Vertebrates can scarcely be epitomized
in a few lines. The mode of growth of Amphioxus is a
general expression for that of all Vertebrates, for all develop
from fertilized eggs, which undergo total or partial segmen-
tation of the yolk, become three-layered sacs and assume the
peculiar vertebrate characters, the development of the mam-
mals differing from that of the other classes only in compar-
atively unimportant features.
The Vertebrates or Chordata are divided into three series
or sub-branches: the Urochordata, the Acrania, and Crani-
ota. The Urochordata. are represented by the class Tuni-
cata. The sub-branch Craniota is divided into six classes,
the Marsipobranchs, fishes, amphibians, reptilia, birds, and
mammals.
386 ZOOLOGY.
CLASS I. — TUXICATA (Ascidians, Sea Squirts).
General Characters of Tunicates. — These animals were
once regarded as mollusks, and in former editions of this book
they were assigned a position among the worms, between the
Brachiopods and the Nemertina.
Kecent advances in our knowledge of Ascidians on the
one hand, and of the primitive features of the Vertebrates on
the other, show quite conclusively that the Ascidians, par-
ticularly the adult form Appendiculana, and the larvae of
those Ascidians which undergo a metamorphosis, have the
fundamental characters of Amphioxus and the embryos of
genuine Vertebrates, such as the lamprey.
It will be remembered that these fundamental characters
are the presence of a notocord, over which lies the central
nervous system. No invertebrate is known to possess
this dorsal position of the nervous system to the dorsal cord,
unless we except Balanoglossus, which, as Mr. Bateson has
shown, has a notocord lying under a central nervous cord.
If the larva of this form was not like that of the worms and
Echinoderms, presenting no vertebrate features, we might
adopt Bateson's view that Balanoglossus should be placed
at or near the base of the Vertebrate series, in a group Pro-
tocliordata.
The result of admitting the Tunicates into the same
branch or type as the Vertebrates has led to the proposal of
a group Cliordata, including the Tunicates and the genuine
Vertebrates; but as Amphioxus seems to be a connecting-
link between the Tunicates and the genuine Vertebrates,
beginning with the hag-fish and the lamprey, we will, for
convenience, retain the familiar word Vertebrata for all ani-
mals having a notocord (either in the embryo, larval, or
adult state) situated between a neural and an enteric cavity.
Fig. 386' will show the close resemblance of the larval as-
cidian to the embryo lamprey.
It will be seen that even the larval Ascidian has an incipi-
ent brain, consisting of two ganglia, from which arise a
spinal nervous cord, with even spinal nerves. The intestine
in the larval Ascidian is bent and ends in front, but in the
adult tadpole-shaped Append icularia the end of the intes-
tine is ventral and opens directly outwards.
POSITION OF THE ASOWIAN8.
387
While all Tunicates, except Appendicularia, are more or
less degenerate, losing their vertebrate characters, in Appen-
dicularia these are retained. The heart is situated ventrally,
occupying nearly the same relation as in Fig. 3861. Accord-
ing to Glaus, "the elongated cerebral ganglion is divided
by constrictions into three parts; it is connected with a cili-
ated pit and an otolithic vesicle, and is prolonged into a
nerve-cord of considerable size. The latter is continued
into the tail, at the base of which it swells out into a gan-
glion; in its further course it forms several small ganglia,
Fig. 3861.— Diagram of embryo Lamprey.
Sfn.
Fig. 3862.— Diagram of larval Aseidian. Lettering- n« in Fig. 3%'. m, mouth: i,
, i __. • . i. j i_
digestive tract; sp, spiracles in the pharyngetil portion: hi, heart; e, eye; er, ear;
br, brain; ?ic, nervous cord; b', b", mid-brain; cl. cerebellum; s/m, spinal nerves;
n, notoeord; ol, nasal cavity; s, suckers (their homologues also occur in young
garpikes and tadpoles).
whence lateral nerves pass out. In consequence of a torsion
of the axis of the tail, the originally dorsally-placed caudal
nerve comes to have a lateral position. The segmentation
of the nerve-cord in the t;iil (as shown by the ganglionic
swellings) corresponds to the segmental divisions of the
muscles, which recall the myotomes of Amphioxus. The
large chorda (urochord), which extends along the whole
length of the tail, constitutes another point of resemblance
to Amphioxus."*
* Also see the treatises of Kowalevsky, Kupffer, Bateson, etc.
388 ZOOLOGY.
Order 1. Ascidiacea. — As an example of Tunicates (Fig.
3862), we will now study the internal anatomy of Boltcnia.
On examining the test of this Ascidian, which is mounted
on a long stalk, the oral or incurrent orifice is soen at the
insertion of the stalk, and the atrial or excurrent orifice on
the same side near the opposite end. On cutting open the
thick test and throwing the flap over to the left, the deli-
cate mantle or tunic is disclosed ; it extends a short distance
into the stalk or peduncle. This thin hyaline mantle is
crossed by two sets of narrow raised muscular bands ; the
transverse fibres are arranged concentrically to the two ori-
fices, so as to close or open them, the longitudinal ones curv-
ing outward from the left side.
Currents of sea-water laden with organic food pass into
the oral orifice, which is surrounded by a circle of tentacles
pointing inward, and thence into a capacious saccular bran-
chial chamber within the mantle, which contracts at the
bottom, where the cesophageal opening is situated. The
walls of this chamber, which is over an inch long in a good-
sized specimen, and gathered into fringed folds, is sieve-like
with ciliated perforations (compare Fig. 3S62 e), making the
walls like a lattice-work, the blood coursing through the ves-
sels passing between the meshes of the sieve-like walls.
The oesophagus, which lies at the bottom of this branchial
chamber, is also situated near the intestine passing over
the anal end into the short stomach. The intestine is long,
passing up to the insertion of the stalk, where it is held
in place by muscular threads extending into the stalk and
attached to the mantle ; it then suddenly bends back and
passes straight down to the vent, which opens opposite to
the atrial orifice ; the end of the intestine is in part revolute
and provided with a fringe of about twenty filaments. The
liver forms a broad and flat mass of a bright livid green, and
consists of three flat lobes each composed of eight or nine
lobules, with very short ducts enveloping the inner aspect of
the intestine. The ovaries are two yellowish, large and long
lobulated masses extending nearly the whole length of the
body, while the right one is a little smaller, and situated in
the fold of the intestine. The atrium is that region of the
STRUCTURE OF APPENDICULARIA.
389
body-cavity which lies between the end of the intestine and
the atrial or excurrent orifice ; into this atrial region the
fasces, eggs, etc., pass on their way to and out of the atrial
orifice.
The simplest form of Tunicate is Appendicularia, which
is tadpole-shaped, bearing a general resemblance to the larva
of an ordinary Ascidian, so that it may be properly called a
larval form. The Appendicularia is a pelagic animal, usually
about one-half of an inch in length, found floating at or
near the surface when the ocean is calm, and occurring in
all seas a few miles from land or in mid-ocean. It swims
by means of its large, long, broad, flat tail, the body being
Fig. 3862.— Anatomy of Boltenia. — Drawn by J. S. Kingsley from the author's
dissections.
oval or flask-shaped. In Appendicularia flabellum, as de-
scribed by Huxley, the caudal appendage is three or four
times as long as the body. The mouth leads into a large
pharyngeal or branchial sac ; a narrow oesophagus at the
bottom of this sac leads to a spacious stomach, with two
lobes, from the left one of which the intestine arises, curves
and ends midway between the mouth and insertion of the
tail. In the middle of the haemal side (that side in which
the heart is situated and bearing the atrial opening) is a
fold of the wall of the pharyngeal cavity called the endostyle.
On each side of this endostyle is an oval ciliated aperture,
390
ZOOLOGY.
•»--.,.,;•,
W'-i
corresponding to the numerous branchial slits in the other
„ Ascidians, but in Appendicularia each oral
r /j~^J' ? aperture leads into a funnel-shaped at rial
rdiutl, the open end of which terminates
beside the rectum.
The heart is a large pulsatile PCC situated
, between the two lobes of the stonnch. The
- nervous system is much more fully developed
than in other Tunicates, and is constructed
on the Vertebrate type, consisting first of
a ganglion situated below the mouth on the
side opposite the atrial opening and opposite
the anterior end of the endostyle. This
nerve-centre throws off nerves to the sides of
the mouth, and from it posteriorly extends a
long cord past the oesophagus to fie base of
the tail, thence it extends along one side of
the axis of the tail (urochord), swelling at
regular intervals into small ganglia, from
which from two to five small nerves radiate.
On the cephalic ganglion a round ear-vesicle
is attached. Behind the posterior turn of
the digestive canal is the testis and ovary,
the Appendicularia being hermaphrodite, as
Fol claims, though the ovary is developed
later than the testis. The Appendicularia
has no test, but secretes a fibrous envelope,
which is at first gelatinous, loosely surround-
_ *. 380". — struc- ing the whole body, and allowing the creature
ture of a compound °
Ascidian, Amarce- the Ireest motion Wltlllll its Cavity.
fin m A, branchial mi •, » . . , .
sac; m, stomach ; /fc, J-hc general structure of an Ascidian may
rr?°&ser- perhaps be more readily comprehended by a
ovary6; tl])'' s^udy of a compound Ascidian (Amaracium),
*••«_' in the bouy-cav- which STOWS in white or flesh-colored masses
ity ; p", eggs in the
atrium; w, anus; o, on sea-weeds, etc. On removing an AHHI-
Bhows the site of the . °
heart; i, liver; e, Tceciuni from the mass and placing it under
openings in walls of , . .,
branchial chamber, the microscope, US Structure Can be per-
— From Macalis er. • i mi i j • i T i j
ceived. The body is long and slender, as
seen in Fig. 386s. The mouth leads by the capacious bran-
°-
dnct
STRUCTURE OF ASCIDIANS. 391
chial sac (A) to the stomach, while the intestine (B) is flexed,
directed upwards, ending at the bottom of the atrium not
far from the atrial opening. The reproductive glands are
situated behind or below the bend of the intestine, the eggs.-
being fertilized as they pass into the atrium, and the heart
lies in the bottom of the body-cavity, being directly opposed
to the nerve-ganglion (not represented in the figure), which
lies between the two openings.
In the perfectly transparent Peropliora, which grows on
the piles of wharves on the coast of Southern New England,
one individual after another buds out (as also in Clavellina)
from a common creeping stalk like a stolon. In this form
the circulation of the blood-disks in the branchial vessels and
the action of the heart can be studied by placing living ani-
mals in glasses under the microscope. The heart is a straight
tube, open at each end, and situated close to the hinder end
of the bianchial sac. After beating for a number of times, .
throwing the blood with its corpuscles in one direction, the
beatings or contractions are regularly reversed and the blood
forced in an opposite direction.
Renal organs are apparently represented in Pltallusia by
a peculiar tissue, consisting of innumerable spherical sacs
containing a yellow concretionary matter. In Molgula and
Astidia vitrea Van Beneden, an oval sac containing concre-
tions of uric acid lies close to the ovary.
In the forms already considered the plan of structure is
complicated, owing to the difficulty of distinguishing an
anterior or posterior, a dorsal or ventral aspect of the
animal. In Salpa and Doliolum, however, the body is more
or less barrel-shaped, the hoops of the barrel represented by
the muscular bands which, at regular intervals, surround the
body. The mouth is near the centre of the front end, the
pharyngeal sac is very large, and the digestive tract makes
less of a turn than in the ordinary Ascidians, while the
atrial opening lies directly at the posterior opening. The
heart is truly a dorsal vessel, and the nervous ganglion is
situated on the opposite side of the body. This relation of
the anatomical systems is most clearly shown in the genua
Dolinhim, and we have here a slight approach to the sym-
392 ZOOLOGY
metrical relation of parts seen in the true worms, and which
strongly suggest the conclusion that the Tunicates are mod-
ified worms. This conclusion is strengthened by the fact
that in Appendicularia the ventral nervous cord is gangli.
onated yt intervals, as in the Annelids, while the twisted
digestive tract is much as seen in Polyzoa and Brachiopods.
Furthermore, the branchial sac is strongly analogous to the
pharyngeal or gill-sac of B:ila)io<jlossus, and this structure in
the Ascidian and whale's-tongue worm anticipates the pha-
ryngeal or gill-sac of AtnpMoxus and vertebrate embryos.
The simple Ascidians attain to a large size, Ascidia callo^a
being about ten centimetres in diameter, quite round, and in
form and color bears a strong resemblance to a potato.
Ascidia gigas, dredged by the Challenger Expedition, is from
thirty to forty centimetres in diameter, and has a ganglion
nearly as large as a pea. A floating colony of Pyroxoma
gigas is sometimes five feet long. Cyutlt ia pyrifonn /'x Rathke
may be called the sea-peach, from its size, form, and the rich
bloom and reddish tints of its test. It is common in deep
water from Cape Cod to Greenland and Scandinavia.
While the Ascidians as a rule do not live below a depth of
150 fathoms, the stalked Hypobythius call/codes Moseley was
dredged by the Challenger Expedition in 2900 fathoms in
the North Pacific Ocean ; it is stalked, and about twenty
inches high. The aberrant Octacnemus bythius Moseley was
also dredged in 1070 fathoms near the Schouten Islands,
Tasmania.
Panceri has described the luminous organs of Pyrosoma,
which is highly phosphorescent ; the substance from which
the light is emitted is probably a fatty matter.
Ascidians multiply by budding and by eggs. Examples of
budding or germination are seen in the compound or social
Ascidians, such as Amarcecium, etc., where the individuals of
the colony bud out from the primitive one just as it lias left
the larval condition and has become fixed. In Dideniniuni
buds arise from masses of cells floating free within the test.
They multiply by division as soon as the digestive and repro-
ductive organs are indicated. In Botryllns the zooid which
results from the tadpole -like larva serves, according to
DEVELOPMENT OF ASGIDIANS.
393
Huxley, merely as a kind of stalk, from which new zooids
bud out, and this process, in his opinion, "leads to the still
more singular process of development in Pyroxn/nti, in which
the first formed embryo attains only an imperfect develop-
ment, and disappears after having given rise to four ascidio-
zooids." In ClaveUin-a and Peropkora the original parent
Aseidian throws off branches or stolons from which develop
new individuals.
The usual mode of development in the simple and com-
pound Ascidians (forming the order Ascidiacea) is by fertil-
ized eggs. We will give the life-history of an Aseidian as
based on Kowalevsky and Kupffer's researches on Phallusia
mammillata Cuvier, in which the embryonic stages were ob-
a
Fig. 3864.— Embryo Aseidian. A. a. primitive opening: h. primitive digestive
cavity; c, segmentation-cavity or primitive body-cavity; B. i, pharynx; u, nerve-
cavity; t, epithelium forming the body-wall; .r, rudimentary notocord; .O. sec-
tion of a fish embryo: u, nervous tube, open in front and situated dorsally;
ch, notocord; bb, mouth; e, alimentary canal; a, place of vent; m, mesoderm.
served, and Ascidia intestinalis, whose larva was studied.
The esg consists of a yolk unprotected by a yolk-skin, but
surrounded by a layer of jelly containing yellow cells. The
yolk undergoes total segmentation. The next step is the
imagination of the ectoderm, a true gastrula state resulting.
Fig. 386", A (after Kowalevsky), represents the gastrula ; h,
the primitive digestive cavity ; «, the primitive opening,
which soon closes ; and c, the segmentation-cavity or primi-
tive body-cavity. After this primitive opening (a) is lost to
view, sometime before the embryo has reached the stage By
another cavity (n) appears with an external opening. This
cavity is formed by a union of two ridges which grow out
394 ZOOLOGY.
from the upper part of the germ. This is the central ner-
vous system, and in the cavity are subsequently developed
the sense organs. We thus see, says Kowalevsky, a com-
plete analogy in the mode of origin of the nervous system of
the Ascidians to that of the vertebrates, the nervous cavity,
where the embryo is seen in section, being situated above
the digestive cavity in both types of animals.
The next important stage is the formation of the tail.
The pear-shaped germ elongates and contracts posteriorly
until of the form indicated at Fig. 3S64, B. At this period
appears the axial string of nucleated cells, called the chorda
dorsalis, as it is homologous with that organ in Amphioxus
and the embryo of higher vertebrates. The nervous system
consists of a mass of cells extending halfway into the tail
and directly overlying the chorda, but extending far beyond
the end of the latter as seen in the figure. The nerve-cav-
ity (B, n] after closing up forms the nerve-vesicle, a large
cavity (Fig. 3865, a), in which the supposed auditory organ
(e) and the supposed eye (a) arise ; this cavity finally closes,
and the sense-organs are indicated by certain small masses
-of pigment cells in the fully grown Ascidian larva.
As the embryo matures, the first change observed in the
cord is the appearance of small, refractive bodies between
the cells. Between the neighboring cells soon appear in the
middle minute highly refractive corpuscles which increase
in size, and press the cell-contents out of the middle of the
•cord. After each reproductive corpuscle grows so that the
•central substance of the cell is forced out, it unites with
the others, and then arises in the middle of the simple cel-
lular cord a string of bodies of a firm gelatinous substance
which forms the support of the tail After this coalescence
the substance develops farther and presses out the proto-
plasm of the cells entirely to the periphery. The cord when
complete consists of a firm gelatinous substance surrounded
by a cellular sheath which is formed of the remains of the
cells originally comprising the rudimentary cord. The cells
lying under the epithelial layer form a muscular sheath of
which the cord (Fig. 386B, c) is the support or skeleton.
The alimentary cavity arises from the primitive cavity
DEVELOPMENT OF A8CIDIANS.
(Fig. 138, A, //) ; whether the primitive opening (Fig. 3S64,
A, a] is closed or not, Kowalevsky says is an interesting
question. According to analogy with many other animals
it probably closes.
The larva hatches in from
forty-eight to sixty hours af-
ter the beginning of segmen-
tation, and is then of the
form indicated by Fig. 386'
(copied with some additions
and omissions from Kupffer's
figure, being partly diagram-
matic). This anatomist dis-
covered in the larva of As-
cidia canina, which is more
transparent than Kowalev-
sky's Phallusia larva, not
only a central nervous cord
•overlying the chorda dorsalis
and extending well into the
tail, while in the body of the
larva it becomes broader,
•club-shaped, and surrounds
the sensitive cavity («), but
he also detected three pairs
of spinal nerves (.s) arising at
regular intervals from the
spinal cord (h, h') and dis-
tributed to the muscles (not
represented in the figure) of
the tail ; Kupffer calls / the
middle and g the lower brain-
ganglion. The pharynx (b),
or respiratory sac, is now
very large ; it opens pos-
teriorly into the stomach and
intestine (i) • x represents
•one of the three appendages by which the larva fastens
itself to some object when about to change into the adult,
Fig. 3866.— Larval Ascidian. a, sense
cavity containing the eye; b, pharynx or
respiratory sac ; c, notochord ; e, supposed
auditory organ ; /', middle, 17, lower brain-
ganglion ; h, ft, spinal cord ; ,s, s, s, three
sets of spinal nerves ; i, intestine ; <,
body-wall, consisting of epithelial cells. —
Copied with some changes from Kupffer.
396 ZOOLOGY.
sessile condition ; t indicates the body-wall, consisting of
epithelial cells.
We will now, from the facts afforded ns by Kowalevsky,
trace the changes from the larval, free-swimming state to
the sessile adult Ascidia, which may be observed on the
New England coast in August. After the larva fastens itself
by the three processes to some object, the chorda dorsalis
breaks and bends, the cells forming the sheath surrounding
the broken axial cord. The muscular fibres degenerate into
round cells and fill the space between the chorda and the
tegument, the jelly-like substance forming a series of wrin-
kles. With the contraction and disappearance of the tail be-
gins that of the nerve-vesicle, and soon no cavity is left. The
three processes disappear ; the pharynx becomes quadrangu-
lar ; and the stomach and intestine are developed, being
bent under the intestine. A mass of cells arises on the an-
terior end beneath the digestive tract, from which originate
the heart and pericardium. In a more advanced stage, two
gill-holes appear in the pharynx, and subsequently two more
slits, and about this time the ovary and testis appear at the
bottom, beyond the bend of the alimentary canal. The free
cells in the body-cavity are transformed into blood-cells, and
indeed the greater part of those which composed the nervous
system of the larva are transformed into blood-corpuscles.
Of the embryonal nervous system there remains a very small
ganglion, no new one being formed. The adult Ascidian
form meanwhile has been attained, and the very small indi-
viduals differ for the most part only in size from those which
are full-sized and mature.
It will be seen that some highly important features, recall-
ing vertebrate characteristics, have occurred at different pe-
riods in the life of the embryo Ascidian. Kowalevsky remarks
that " the first indication of the germ, the direct passage of
the segmentation cells into the cells of the embryo, the for-
mation of the segmentation-cavity, the conversion of this
cavity into the body-cavity, and the formation of the diges-
tive cavity through invagination — these are all occurrences
which are common to many animals, and have been observed
in Amphioxus. Saqitta, Phoronis, Echinus, etc. The first
RELATION OF ASCIDIANS TO VERTEBRATES. 397
point of difference from other animals in the development
of all vertebrates is seen in the formation of the dorsal
ridges, and their closing to form a nerve-canal. This mode
of formation of the nervous system is characteristic of the
vertebrates alone, except the Ascidians. Another primary
character allying the Ascidians to the vertebrates, is the
presence of a chorda dorsalis, first seen in the adult Appen-
dicularia by J. M filler. This organ is regarded by Kowal-
evsky to be functionally, as well as genetically, identical with
that of Amphioxus. This was a startling conclusion, and
stimulated Professor Kupffer, of Kiel, to study the embry-
ology of the Ascidians anew. He did so, and the results this
careful observer obtained led him to fully endorse the con-
clusions reached by Kowalevsky, particularly those regarding
the unexpected relations of the Ascidians to the vertebrates,
and it would appear from the facts set forth by these emi-
nent observers, as well as Metschnikoff, Ganin, Ussow, and
others, that tlie vertebrates have probably descended from
some type of worm resembling larval Ascidians more perhaps
than any other vermian type, though it is to be remembered
that certain tailed larval Distomge appear to possess an organ
resembling a chorda dorsalis, and farther investigation on
other types of worms may lead to discoveries throwing more
light on this intricate subject of the ancestry of the verte-
brates. At any rate, it is among the lower worms, if any-
Avhero, that we are to look for the ancestors of the Vertebrates,
as the Coeleuterates, Echinoderms, the Mollusks, Crustacea
and Insects, are too circumscribed and specialized groups to
afford any but characters of analogy rather than affinity.
For example, the cuttlefish, with its "bone," brain-cap-
sule and highly-developed eye, is, on the whole, more remote
from the lowest vertebrate, Amphioxus, than the Appendi-
cularia or the larval Ascidian.
Certain (three) species of Molgula have been found by
Lacaze-Duthiers to have a nearly direct development, not
producing tailed young. There is a slight metamorphosis,
however, the young having five temporary, long, slender
processes. In Ascidia ampulloides the larva has a tail, no-
tochord and pigment spots, which are wanting in the young
398
ZOOLOGY.
of several species of Molgula, but it has the five long decid-
uous appendages observed in young Molgulw. Among the
compound Ascidians, Botryllus and Botrylloides have tailed
young, while in other forms there is no metamorphosis, de-
velopment being direct.
Order 2. ThaUacea. — On the whole, we may regard this
order, represented by Salpa (Fig. 3S66), and DoUohnn, as
comprising the more specialized forms of Tunicates. Salpa
is pelagic, one species occurring in abundance off the shores
of Southern New England, while
the ethers mostly live on the high
seas all over the tropical and sub-
tropical regions of the globe. Late
in the summer our Salpa spinosa
of Otto can be captured in multi-
tudes by the tow-net in Long Island
Sound.
There are in Salpa two kinds of
individuals, i.e., the solitary, and
aggregated or chain-Salpse. The
body of the solitary or asexual
form is more or less barrel-shaped,
with a series of circular bands of
muscles, like the hoops of a barrel,
and situated on the inner side of
the outer tunic. The test is trans-
parent, though very thick, while
the outer tunic lines the cavity of
^ test as in other Tunicates. In
the chain are united ; h, heart; «, the members of this order the oral
nervous ganglion ; o, nucleus ; r,
gill. -After A. Agassiz, fromVer- aperture of the mantle is at one
rill's Report.
end ot the body, and the atrial
opening at the opposite end, the minute digestive canal be-
ing but slightly curved, the body-cavity being largely occu-
pied by the pharyngeal or respiratory sac. Moreover, the dor-
sal or haemal side of the body is clearly distinguishable from
the ventral or neural side, as well seen in Doliolinn, where
the well-marked tubular heart lies above the digestive organs,
and is directly opposed, as in worms generally, to the nervous
*. -Salpa spinosa. An
STRUCTURE OF SALPA. 399
system, which is situated ventrally between the mouth and
vent. We thus have in these Tunicates a front and hindi
end of the body, a dorsal and ventral, as well as a distinct-
bilateral symmetry of the body. This is seen in Appendi-
cularia as well as in Doliolum and Salpa, however much
this symmetry may be obscured in the more typical Ascidi-
ans, such as Ascidia, Molgula, BoUenia, etc.
The oral aperture leading into the respiratory sac is larger
being as wide as the body ; the respiratory sac is more com-
plicated than in other Ascidians, and more so than in Doll-
olttDi, where it is a wide, dee}) passage, the oesophagus at the
hinder end, the sac itself perforated by two rows of bran-
chial slits, four or five slits in each row. In Salpa, how-
ever, the respiratory sac, as described by Brooks, is attached
to the outer tunic, around the edges of the mouth, as in
other Tunicates. There are only two branchial slits, one on
each side ; these are very large, and cover almost the whole
surface of the branchial sac. except the median dorsal and
haemal lines. On the neural side the branchial slit opens
directly into the atrium, the ciliated line where the two.
tunics unite being marked by the so-called "gill'' (Brooks).
In Salpa, according to Brooks, the branchial sac, though
ciliated within, is not so directly concerned in the respiratory
act as in other Tunicates, since respiration is effected largely
by the action of the muscles, which also assist deglutition,
and are the organs of locomotion. These contract rythmi-
cally, with great regularity, and at each contraction the
water is expelled from the branchial sac through the atrial
aperture ; and when the muscles are relaxed, the elasticity
of the test distends the chamber, and afresh supply is drawn
in through the branchial aperture, the lips of which readily
admit its passage in this direction, while a similar set of
valves allows its passage out of the atrial aperture, but pre-
vents its return." Thus a chain of individuals move with a
uniform motion, while the solitary individuals and those
which have been set free by the breaking up of a chain, move
by jerks.
The digestive canal is small, curved on itself, the oesopha-
gus leading from the bottom of the pharyngeal or respiratory
400
ZOOLOGY.
sac into a small stomach, the intestine bending Lack on
itself, and the vent being near the month. The entire dio-cs-
tive canal is immovable, the food being driven through the
permanently distended cavity by means of the cilia lining
its inner surface. The great posterior blood-sinus surrounds
the digestive system on all sides, the nutriment being di-
rectly absorbed from its surface and mixed with the blood.
The nervous system is, in adaptation to its locomotive life,
more specialized than in the sessile forms, and highly spe-
cialized organs of sight and hearing are present, The'heart
is a short, complicated organ, lying in the sinus-system. Its
action is often reversed ; the reversal of the beats tending
to clear the sinuses of the blood-disks overcrowding them.
In one species of Salpa Prof. Brooks states that the blood-
channels are in all cases sinuses, which are parts of the body-
cavity and have no special Avails, though in species investi-
gated by other writers there are said to be true blood-vessels,
lined with epithelium.
The hermaphroditic, aggregated or chain-salpa differs from
the solitary asexual form in being less regularly barrel-
shaped, and without the two long posterior appendages of
the latter ; in the proportions of the different organs, the
two forms are essentially alike.
The young chain is easily perceived in the solitary indi-
viduals in the posterior part of the body, curving around the
digestive organs. When first set free from the body of the
solitary Salpa, the chain is about half an inch long, and the
single, individual Salpa? composing it are about two and a half
millimetres in length. They grow very rapidly, and soon
reach their full size, when the chains are often a foot or a
foot and a half long ; the individuals composing them when
fully grown being about two centimetres in length. The
chain easily falls apart, and the individuals are capable of
living a solitary life, Huxley stating that the chain-individu-
als of the species observed by him were generally found soli-
tary ; for this reason we should regard the cham-salpSB as
individuals, not zooids, being capable of leading an inde-
pendent existence, and with a structure almost identical with
that of the solitary Salpge.
DEVELOPMENT OF SALPA. 401
Brooks has studied the mode of development of the female
and male Salpa sj)ino*a (Fig. 386"). When a Salpa-cham is
discharged from the body of the asexual Salpa, each indi-
vidual of the chain contains a single egg which is fertilized
by sperm-cells of individuals belonging to some other chain,
and after passing through the mulberry stage and entering
the gastrula stage, the germ is in most intimate relation
-\vith the body of its parent. The vase-shaped gastrula is
lodged in a brood-sac. Its body-cavity, originally formed by
invagination of the ectoderm, opens directly into the tmuis-
system of its nurse, and the blood now circulates in and out
of the primitive digestive cavity as well as around the out-
side of the embryo. But as the embryo grows and tills the
brood-sac, so that the outer surface of the gastrula becomes
intimately connected with the wall of the brood-sac, the
blood no longer bathes the outside of the embryo.
At this time the " placenta" is formed. Brooks believes
that it originates directly from the blood, "by the aggrega-
tion and fusion of its corpuscles," not being derived from any
of the parts of the parent or embryo. Soon after its appear-
ance it consists of an inner chamber communicating with the
sinus of the nurse, and having no communication with any
of the cavities of the embryo ; its cavity being a part of the
original "primitive stomach" of the gastrula. It finally has
two chambers, an inner and outer one, and Huxley describes*
the foetal circulation in the placenta, a deciduous organ
analogous in function, but by no means homologous in struc-
ture, with the vertebrate placenta.
When the embryo of the solitary Salpa is nearly one
millimetre (-£-$ inch) long, and while still in the brood-sac of
the parent, the tube which is to give rise to the chain ap-
* " The blood-corpuscles of the parent may be readily traced enter,
ing the inner sac on one side of the partition, coursing round it, and
finally re-entering the parental circulation on the other side of the par-
tition ; while the fcetal blood-corpuscles, of a different size from those
of the parent, enter the outer sac, circulate round it at a different rate,
and leave it to enter into the general circulation of the dorsal sinus.
More obvious still does the independence of the two circulations be-
come when the circulation of either mother or tetus is reversed."
402 ZOOLOGY.
pears within its body. We will now briefly trace the devel-
opment of the chain-salpa, condensing Brooks's statement.
The aforesaid tube is at first simply a cup-like protrusion of
the outer tunic into the cellulose test which now surrounds
the embryo ; the cavity of the cup is an offshoot from the
sinus-system, the blood passing in and out of it, A small
bud-like protrusion now appears upon the surface of the per-
icardium, and lengthens to form a long rod or stolon, ex-
tending across the sinus and projecting into the cavity of the
cup. At about this period a long, club-shaped mass of pro-
toplasm appears within each of the sinus-chambers of the
tube, and soon after the puU-r wall is constricted at regular
intervals, each segment being destined to form the outer tu-
nics of the chain-salpa?, the constrictions indicating the
bodies of the latter.
By the deepening of these constrictions, each of the
sinus-chambers, which are diverticula from the body-cav-
ity of the solitary Salpa, becomes divided up to form the
body-cavities of the Salpa? on one side of the chain. From
the central tube of the stolon arises a row of buds on each
side, which become the branchial and digestive organs of the-
Salpa? on each side of the chain ; while a similar double row,
upon the other edge, gives rise to the ganglia. The club-
shaped organs within the sinus-chambers become divided up
into single rows of eggs, one of which passes into the body-
cavity of each chain-salpa at a very early period of develop-
ment.
Thus, as Huxley states, budding occurs, not from the outer
wall alone, as in Hydroids and Polyzoa, "but, from the first,
several components, derived from as many distinct parts of
the parental organism, arc distinguishable in it, and each com-
ponent is the source of certain parts of the new being, and
of these only." Prof. Brooks adds that while these changes
are going on the constrictions on the surface deepen, the
wall protruding from them, and each is soon seen to mark
off, on each side of the stolon, the body of a young Salpa,
which soon becomes visible to the naked eye. They do not
increase in size gradually from one end of the stolon or tube
to the other, but develop in sets of from thirty to fifty each,
GENERATIONS OF SALPA. 403
and the development of all which are embraced within a set
progresses uniformly ; there are usually three of these sets
upon the tube of an adult solitary Salpa.*
Thus the Salpa reproduces parthenogenetically as in some
Crustacea and insects, and we have here a true case of " alter-
nation of generations." In 1819 Chamisso stated "that a
Salpa mother is not like its daughter or its own mother, but
resembles its sister, its granddaughter, and its grandmother, f
Immediately after the publication of Brooks' researches
on Salpa spin-osa, those of Salensky on Salpa democratica-
mucronata (a species said to be closely allied if not identical
with S. spinosa) appeared. According to the Russian ob-
server, as stated by Huxley, who adopts his conclusions, the
chain-salpa is a hermaphrodite, and the egg while still in
the ovarian follicle is fertilized, when the oviduct shortening
and widening forms a single uterine sac, the maternal and
* The Development of Salpa, by W. K. Brooks. Bulletin of the
Museum of Comparative Zoology, III., No. 14, Cambridge, 1876. We
have presented quite fully the author's account of the mode of devel-
opment of the young asexual (his female) Salpa, without, however,
adopting1 his interpretation of the sexes of the two kinds of individuals,
of Salpa ; believing his " female" Salpa to be asexual, and his " male"
Salpa to be hermaphrodite, with an ovary and testis, as he has not ap-
parently observed the fact of the introduction of an egg into the body
of his "male" Salpa. On the contrary, it appears to be developed
originally in a true, simple ovary or "ovarian follicle;" the testis being
immature and the egg fertilized by sperm-cells of other hermaphro-
dites, in-and-in breeding thus being prevented.
\ This view has been endorsed by Steeustrup, Sars, Krohn, and
others, especially by Leuckart in the following words quoted by
Brooks: "It is now a settled fact that the reproductive organs are
found only in the aggregated individuals of Salpa, while the solitary
individuals, which are produced from the fertilized eggs, have, in
place of sexual organs, a bud-stolon, and reproduce in the asexual
manner exclusively, by the formation of buds. Male and female
organs are, so far as we yet know, united in the Salpae in one indi-
vidual. The Sulpce are hermaphrodite." On the other hand, Todaro,
in an elaborate memoir (1876), considers the Salpa as the synthetic
type of all the vertebrata, presenting features peculiar to each class,
even including the mammals. In his opinion it is an allantoidian ver-
tebrate, developed in a true uterus, the neck of which, after the life of
the embryo begins, becomes plugged with mucus.
404 ZOOLOGY.
embryonic parts of the placenta arising, respectively, from
the wall of the ovarian sac and from certain large cells (blas-
tomeres) on the adjacent (haemal) face of the embrvo. Thus
the asexual development of the Salpa is like that of the germ-
masses destined to form the Ccrcarm developed in the body
of the Redia of the Distoma ; and is also like that of the
plant lice (Huxley). This is a reaffirmation and extension
of the original view of Chamisso.
To recapitulate, the life-history of the Salpa is as follows :
There are two kinds of individuals : a, solitary, asexual ; b,
social, aggregated, and hermaphroditic.
(1.) The solitary, asexual Salpa produces by budding a
chain of hermaphrodite Salpie ; the latter produce a fertil-
ized
(2.) Egg, which passes through a —
(3.) Morula and—
(4.) Gastrula stage, contained and growing in a placenta-
like organ, where the embryo is directly nourished bv the
blood of the parent, the embryo finally becoming—
(5.) A solitary asexual Salpa.
We thus have a true alternation of generations, like the
sexless Hydroid and its sexual Medusa, the asexual Aphis
and its last brood of males and females ; the asexual Redia
and the sexual Dixionia ; in all these cases the offspring (b)
of the asexual individual (a) is unlike the parent, but the off-
spring (c) of the second generation (b) is like (a) the grand-
parent.
"In Doliolum the reproductive processes are much more
complicated, for not only do the sexually produced young
undergo a metamorphosis, but a new series of generations is
introduced into thp life-history. The eggs are laid, and the
larva? which issue from them are provided with tails and re-
semble Ascidian larvae. They develop into asexual forms,
which differ from the sexual forms, and are provided with a
dnrxal stolon; the ventral stolon (stolon of Salpa) is rudimen-
tary. Two different kinds of buds are formed on this dorsal
stolon, viz., median ltt<f« and lateral buds. The lateral buds
have a slipper-like form, and are without the cloacal cavity;
they do not reproduce themselves, but are concerned with the
nourishment of the asexual form. The latter as it increases
CHARACTERISTICS OF TUNIC AT KS. 405
in size, loses its gills and alimentary canal, while its muscu-
lar system becomes powerfully developed. The median buds
develop into individuals, which resemble the sexual animals,
except that they are without genital organs; they, therefore,
represent a second generation of asexual forms, which become
free and produce the sexual generation from a ventral sto-
lon."*
CLASS I.— TUNICATA.
Body usually subspherical, or sac-like, obscurely symmetrical ; some-
times barrel shaped, bilateral, with a dorsal and ventral symmetry, pro-
tected by a transparent or dense test, containing cellulose, lined within
by a tunic surrounding the body-cavity. Two openings in the test, one
oral, the other atrial ; mouth leading into a capacious pharyngcal res-
piratory sac, opening posteriorly by an o&sopliagus into a stomach, which
is provided icith a liver; intestine flexed, vent opening near the oesophagus,
the fwces passing into an atrium or cloacal space, and thence out of the
atrial opening. Nervous system bilateral, forming a double ganglio-
nated chain (AppenrUcul/iria), but usually reduced to a single ganglion,
situated within the tunic between the two openings ; a tubular heart, open-
ing at each end, lodged in a sinus-system, and its beatings often reversed,
the blood flowing in and out at either end. Sexes usually united ; in some
forms asexual individuals ; reproducing by eggs or budding partheno-
genetically, or by gemmation.
Order 1. Ascidiacea. — Body sac-like, subspherical, usually sessile,
sometimes stalked, simple or compound, minute individuals
growing in a common mass ; the oral and atrial openings
contiguous ; often a complete metamorphosis. (Appendicu-
laria, Botryllus, Auiarceciuin, Clavellina, Perophora, As-
cidia, Boltenia, Pyrosoma).
Order 2. Thaliacea. — Body barrel-shaped ; free-swimming, test thick,
hyaline; with circular muscular bands; respiratory sac
widely open ; reproducing by alternation of generations.
(Salpa, Dolioluui).
Laboratory Work. — The Tuuicates can well be studied only in a
living state; or sections of hardened Salpae may be made. The young,
caught with the tow-net, should be immediately examined, as they
are very short-lived. Delicate sections of hardened eggs and larvae
are made with great difficulty, but are necessary to examine in con-
nection with the living, more or less transparent animals.
* Glaus, Zoology, English edition, ii. p. 107.
406
ZOOLOGY.
CLASS II. LEPTOCARDII (Lancelet).
The lancelet
worm-like form
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is the only type of this class. From ite
it was regarded as a worm by some authors,
and as a mollusk ("Limax") by
Pallas. The body is four or five cen-
timetres in length, slender, com-
pressed, pointed at each end, hence
the generic name (Amphioxus, a^cpi,
both, o£v$, sharp), the head-end be-
ing thin, compressed. The muscu-
lar segments are distinct to the
naked eye. From the mouth to the
Vent is a deep ventral furrow, and
a slight fin extends along the back
and ventrally as far front as the vent.
The lancelet, A. lanceolatu* (Pal-
las), lives in sand just below low-
water mark, ranging on our coast from
. the mouth of Chesapeake Bay to
Florida ; it also occurs on the South
American coast, and in the European
seas and the East Indies, the species
being nearly cosmopolitan.
As this is the lowest Vertebrate, its
structure and mode of development
merit careful study.
The mouth is oval, surrounded
with a circle of ciliated tentacles
supported by semi-cartilaginous pro-
cesses arising from a circu moral ring.
The mouth leads directly into a large
broad pharynx or "branchial sac"
(Fig. 387, (1), protected at the en-
trance by a number of minute cili-
ated lobes.
The walls of this sac are perforated
by long ciliated slits, comparable with those of the bran
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DEVELOPMENT OF THE LANCELET. 407
filial sacs of Ascidians and of Balanoglossus. The water
which enters the mouth passes out through these slits where
it oxygenates the blood, and enters the peribranchial cavity,
thence passing out of the body through the abdominal pore
(Fig. 387, c). The pharynx leads to the stomach (e), with
which is connected the liver or coecum (/). There is a
pulsatile vessel or tubular heart, beginning at the free end
of the liver, and extending along the underside of the phar-
ynx, sending branches to the sac and the two anterior branches
to the dorsal aorta. " On the dorsal side of the pharynx the
blood is poured by the two anterior trunks, and by the
branchial veins which carry away the aerated blood from
the branchial bars, into a great longitudinal trunk or dorsal
aorta, by which it is distributed throughout the body."
(Huxley.) There are also vessels distributed to the liver,
and returning vessels, representing the portal and hepatic
veins. The blood-corpuscles are white and nucleated.
The vertebral column is represented by a notochord which
extends to the end of the head far in front of the nervous
cord ; and also by a series of small semi-cartilaginous bodies
above the nervous system, and which are thought to repre-
sent either neural spines or fin-rays. The nervous cord lies
over the notochord ; it is not divided into a true brain* and
spinal cord, but sends off a few nerves to the periphery, with
a nerve to the single minute eye. There are no kidneys
like those of the higher Vertebrates, but glandular bodies
which may serve as such. The reproductive glands are
square masses attached in a row on each side of the walls of
the body-cavity. The eggs may pass out of the mouth or
through the pore. Kowalevsky found the eggs issuing in
May from the mouth of the female, and fertilized by sper-
matic particles likewise issuing from the mouth of the male.
The eggs are very small, 0 • 105 millimetres in diameter. The
eggs undergo total segmentation, leaving a segmentation-
cavity. The body-cavity is next formed by invagination.
The blastoderm now invaginates and the embryo swims
about as a ciliated gastrula. The body is oval, and the germ
does not differ much in appearance from a worm, starfish.
* Langerhans lias figured an olfactory lobe; and all observers agree
'that a ventricle is. present ; thus there is a slight approximation to a
brain.
408 ZOOLOGY.
or ascidian in the same stage of growth. No vertebrate
features are yet developed.
Soon the lively ciliated gastrula elongates, the alimentary
tube arises from the primitive gastrula-cavity, while the edges
of the flattened side of the body grow up as ridges which
afterwards, as in all vertebrate embryos, grow over and en-
close the spinal cord. When the germ is twenty-four hours
old it assumes the form of a ciliated flattened cylinder, and
now resembles an Ascidian embryo (Fig. 138, B], there
being a nerve-cavity, with an external opening, which after-
wards closes. The notochord appears at this time.
In the next stage observed the adult characters had ap-
peared, the mouth is formed, the first pair of gill-openings
are seen, eleven additional pairs appearing. It thus appears
that while the lancelet at one time in its life presents Ascidian
features, yet as Balfour states " all the modes of develop-
ment found in the higher Vertebrates are to be looked upon
as modifications of that of Amphioxus."
A second form of this group, from Moreton Bay, North-
ern Australia, has been described by Peters under the name
of Epiyonichtliys cult ell UK. It differs from Amphioxus in
the presence of a high dorsal fin, in the want of a distinct
caudal and anal fin, with some differences in the structure
of the mouth and oral tentacles. It is from thirteen to
twenty-three millimetres in length.
CLASS II.— LEPTOCARDII.
Comprising the lowest Vertebrate known ; body lancet-shaped, with no
skeleton; notochord persistent, no brain; no cranium ; no paired fins ;
blood colorless ; a metamorphosis ; gastrula ciliated, free-swimming.
A single order (Pharyngobrancki), family (Amphioxini), and genus
(Ampliioxus), each with the characters of the class.
Laboratory Work. — The structure of the lancelet can only be imper-
fectly made out by a triplet lens and higher powers ; but by sections
stained with carmine the anatomy can be well studied.
LITEUATURE. — The writings of Kowalevsky, Sin-da, Hatschek,
Langerhaus, Lankester, and Rice (Arner. Nat , 1880).
GENERAL CHARACTERS OF MARS1POBRANC1IS. 409
CLASS III. MARSIPOBRANCHII (Lampreys, or CycUttomi).
General Characters of the Cyclostomatous Vertebrates.
-In the hag-tish and lamprey, representatives of the jaw-
less Vertebrates, the body is long and slender, cylindrical,
the skin smooth, scaleless, with only a median dorsal and
ventral fin (or in Myxine only a small lower median fin) ;
the mouth is circular, and in the lampreys armed with nu-
merous conical teeth. There is no bony skeleton ; the
spinal column is represented simply by a thick rod (dorsal
cord, notochord) surrounded by a sheath. The skull is car-
tilaginous, not movable on the vertebral column ; is very
imperfectly developed, having no jaws, the hyo-mandibu-
lar bones and the hyoid arch existing in a very rudimentary
state. The few teeth present in the hag-fish are confined to
the palate and tongue ; those of the lamprey are numerous,
conical and developed on the cartilages supporting the lips.
The nervous system is much as in the fishes, the brain
with its olfactory, cerebral lobes, thalami, optic lobes, and
medulla being developed, the cerebellum in Myxinc blended
with, in the lamprey free from the medulla. The digestive
canal is straight, with no genuine stomach, but the liver is
much as in higher Vertebrates. The respiratory organs are
very peculiar, being purse-like cavities (whence the name
Marsipobranchii), in the lamprey being seven in number on
each side of the pharynx, opening externally by small aper-
tures ; internally they connect with a long cavity lying under
the oesophagus, and opening anteriorly into the mouth. The
heart is like that of fishes, as are the kidneys. The eyes
are minute, sunken in the head and under the skin in the
hag (My. tine), but larger in the lamprey.
Another extraordinary feature in the class is the single
nasal aperture, as opposed to the two occurring in all
higher Vertebrates. The aperture leads to a sac, which
in the Myxine communicates with the mouth (pharynx), but
in the lamprey forms a cul-de-sac.
The ovaries and male glands (the sexes being distinct) are
impaired plates suspended from the back-bone, and have no
410 ZOOLOGY.
ducts, the eggs breaking through the walls of the ovary, fall-
ing into the abdominal cavity and passing out of the abdom-
inal pore. The eggs of My.rinc are very large in proportion
to the fi-h, enclosed in a horny shell, with a filament at each
end by which it may adhere to objects.
The hag-fish is about afoot long and an inch thick, with
the head small, a median palatine tooth, and two comb-like
rows of teeth on the tongue. There is a single gill-opening
a long way behind the head ; there are large mucous or
slime-glands on the side of the body, for these tishcs are
very slimy. The hag lives at considerable depths in the sea ;
we have dredged one at 114 fathoms in soft deep mud oil'
Cape Ann. It is often parasitic, attaching itself to the bod-
ies of fHi, and has been found to have made its way into the
body-cavity of sturgeons and haddock.
The lamprey lives both in fresh and salt water. The eggs
of the common lamprey. P<>trnniy\on nun-inns (Linn.), are
laid in early spring, the fish following the shad up the rivers,
and spawning in fresh water, seeking the sea in autumn ;
small individuals, from five to seven inches long, have been
seen by Dr. Abbott attached to the bellies of shad, sucking
the eggs out of the oviducts.
The lamprey when six inches long is quite unlike the adult,
being blind, the eyes being concealed by the skin ; it is tooth-
less, and has other peculiarities. It is so strangely unlike the
adult that it was described as a different genus (Amtnoccetes).
P. nigricans Lesueur is smaller, and occurs in the lakes of
New York and eastward, while P. nujer Rafinesque is still
smaller, and lives in the Western States.
CLASS IIL MARSIPOBRANCHT.
t
Worm-like Vertebrates, without paired fins ; notocJiord persistent; a
single nasal sac, stix or ten pairs of purse-like gill-sacs, no jaw-born ••>•.
Order 1. ir///n/'»tetra. — Nasal duct leading into the mouth. (Myxine.)
Order 2. Hyperonrtiu. — Nasal duct a blind sac, not connecting with
the mouth. (Petromyzon.)
GENERAL CHARACTERS OF FISHES.
411
Laboratory Work. — The anatomy of th'ese animals is exceedingly in-
teresting ; the respiratory sacs and nasal duct can be exposed by a lon-
gitudinal section of the head ; the relations of the notochord can be
l,,.st seen by transverse sections ; the heart and vessels should be in-
ii-cted. Preparations of the brain should be made, and with care the
skull prepared. SeeMiiller, 1835-45, W. B. Scott (Journ. Morphology,
1888).
CLASS IV. PISCES (Sharks, Rays, Sturgeons, Garpikes, and
bony fishes).
General Characters of Fishes? — We now come to Verte-
brates which have genuine jaw-bones and paired fins, and
which, in short, are affiliated to the Batrachians, and through
them with the reptiles, birds, and mammals. All the fishes
agree in having a true skull, to which is attached a movable
lower jaw. The brain is well developed, with its lobes for
the most part, at least, equivalent to or homologous with
those of the reptiles, birds, and mammals, though the cere-
bral hemispheres are small, and in most fishes of nearly the
same size as the optic lobes ; the cerebellum is also generally
Damnl fin.
Caudal.
Anal. Ventral. Pectoral.
Fig. 388.- The Mud-Minnow.
-of moderate size. The head forms part of the trunk, there
being no neck (except in the Hippocampidce}, and the body
is usually compressed and adapted in shape for rapid motion
in the water.
Paired fins are always primitively developed, though the
posterior or ventral fins, at least, are in many cases wanting
through the atrophy of parts developed in. embryonic life.
The pectoral and ventral fins (Fig. 388), which represent the
fore and hind legs of higher Vertebrates, are attached to tho
body or trunk by a shoulder and pelvic girdle. The shoulder
* Giiuther's Introduction to the Study of Fishes. London, 1880.
413 ZOOLOGY.
girdle is either lyre-shaped or forked, like a bird's wish-bone,
curved forward, and with each side connected below ; the
fishes in this respect differing from the Batrachians (Gill).
The shoulder girdle is usually closely connected by a series
of intervening bones with the skull, and makes its first ap-
pearance opposite the interval between the second and third
vertebrae.
The skull and skeleton may be either cartilaginous or bony,
and the bones of the head and skeleton very numerous. In
some sharks there are 365 vertebrae ; in some bony fishes 200,
while in the Plectognatlii (fishes like the sun-fishes and Ba-
listes) there may be no more than fifteen ; thus in some
fishes there may be about one thousand separate bones. No
fishes have a well-defined sternum or breast-bone, this bone
appearing for the first time in the Batrachians. The verte-
brae are almost always biconcave ; this is the simplest, most
primitive form of vertebra^ ; it forms a weak articulation,
admitting, as Marsh states, of free, but limited motion.
All fishes breathe by gills, which are supported generally
on four or five cartilaginous or bony supports or arches. The
gills are never purse-shaped, as in the lampreys, and are
mostly situated within the head, in front of the scapular arch.
The mouth is generally armed with teeth varying greatly
in number and form, and in the bony fishes especially, not
only the jaws, but any bony projections, such as the palatine,
pterygoid and vomerine bones, as well as the tongue and pha-
ryngeal bones may be armed with teeth, so that the food is
retained in the mouth and more or less torn and crushed be-
fore being swallowed.
Fish have no salivary glands. The tongue moves only as
a part of the hyoid apparatus upon which it is attached.
After being crushed and torn in the mouth the food passes
through a short throat or oesophagus into the stomach. The
intestine is generally provided at the anterior end with
several or numerous coscal appendages which are especially
abundant in the cod. The gut is twisted once or twice be-
fore reaching the vent, but is usually much shorter than in
the air-breathing Vertebrates, while the vent is placed much
nearer the mouth than in the tailed Amphibians, thus sepa-
STRUCTURE OF FISHES. 413
rating the trunk into a thoracic and caudal portion. To
make up for the short intestine, its absorbing surface is
greatly increased in all except the bony fishes by a peculiar
fold called the "spiral valve." The rectum always opens in
front of the urinary and genital outlets ; except when the
latter communicates directly with the rectum, thus forming
a cloaca. All fishes have a well-developed liver, usually a gall-
bladder, with several gall-ducts ; and in general a yellowish
pancreas.
The heart consists of a ventricle and auricle, the latter
branchial with a venous sinus (sinus venosus) ; while to the
ventricle is added an arterial bulb, which subdivides into five
pairs of arteries, one for each gill-arch. The Dipnoi ap-
proach the Amphibians in the possession of a second auricle
as well as of genuine lungs, i.e., cellular air-sacs. The lungs
are fundamentally comparable with the air-bladder or swim-
ming bladder. It is generally situated below the back-bone,
and is developed originally as an offshoot of the oesophagus.
It is either free, not connected with the digestive tract, or its
original attachment may be retained in the form of the
''pneumatic duct," which, when persistent, opens into the
cesophagus. In the sharks it is either absent or exists in a
rudimentary state.
The kidneys are two voluminous, dark-red lobulated or-
gans, lying close together next to the back-bone, behind, i. e.,
above the air-bladder, and occupying nearly the whole length
of the abdominal cavity. The efferent ducts (ureters) either
pass along in front of or by the side of the kidney, and some-
times unite to form a single sac, the outlet of which is situ-
ated either behind or below the generative orifice. It has
been found that the minute structure of the kidneys of em-
bryo sharks resembles somewhat the segmental organs of
worms, the original kidney being composed of bundles of
ciliated funnels, like those of worms, combined, however,
with Malpighian bodies and renal lobules which do not exist
in worms, while all these parts have a common duct, the
ureter, which also does not exist in worms, being character-
istic of Vertebrates.
In the fishes the sexes are, with a very few exceptions, dis-
414 ZOOLOGY.
tinct. The ovaries are large bodies, either discharging the
eggs directly, as in the eel, salmon, and trout, into the body-
cavity, thence passing along a fold of the peritoneum out of
a minute opening situated directly behind the vent, or, as in
most bony fishes, there is a duct leading from each ovary to
the common outlet. In the sharks and skates (Elasmo-
branchs) the ovary is single, and the oviducts unite behind
to serve as a uterus in such sharks as are viviparous ; or th'-
same parts secrete a shell in the egg-laying sharks (Scyllium)
and skates.
The reproductive glands of most fishes are, except in the
breeding season, so much alike, that it is difficult to distin-
guish them except by a microscopic examination. In the
breeding season the ovaries of the cod, perch, and smelt are
very large and yellowish, while the testes are small and white.
Fishes, like some Amphibians and many invertebrates, may
be able to perform the reproductive functions before they are
fully mature ; in fact, some fishes continue to grow as long
as they live.
The fishes are not a homogeneous or "closed," i. e., well-
circumscribed, type, as the birds and mammals, for the form
of the body is liable to great variation, the differences be-
tween the subdivisions or orders, families and genera being
much greater than in birds and mammals.
The class is divided into three subclasses, viz. : the Elax-
mobranchii (sharks and rays), the Ganoidei (sturgeons, gar-
pikes, etc.), and the Teleostei, or bony fishes. The classifi-
cation we adopt is that of Professor Gill.
Subclass 1. Elasmobranchii*('SV7rrr///Yms, or Sharks and
Rays). — These are the most generalized as well as among the
oldest of all fishes. In some respects they stand above the bony
fishes, with some features anticipating the Amphibians, while
in their cartilaginous skeleton, their numerous gill-openings,
and their general appearance they are scarcely higher than the
embryos of the bony fishes. It would seem as if a shark were
an embryo fish, Avhich had been hurried by nature into exist-
ence with some parts more perfect than others, in order to
serve in the Upper Silurian and Devonian times as destructive
* Sec Muller aud Heule, Basse, Balfour, Wyman, Garman, etc.
A It KS AJ!fD SAYS. 415
agents to the types of invertebrate life which then became
extinct, partly through their means. These and ganoid fishes
having thus accomplished their work were replaced in the
later ages by more highly elaborated and specialized forms,
i.e., the bony fishes. Sharks and skates are engines of de-
struction, having been since their early appearance in the
Upper Silurian age the terror of the seas. Their entire
structure is such as to enable them to seize, crush, tear, and
rapidly digest large invertebrates, and the larger marine
members of their own class. Hence their own forms are
gigantic, soft, not protected by scales or armor, as they have
in the adult form few enemies. Hence they do not need a
high degree of intelligence, nor special means of defence or
protection, though from their activity the circulatory system
is highly developed.
In the general form the sharks are long and somewhat cylin-
drical, with the head rather large, often pointed, sometimes,
in in the hammer-headed shark, extraordinarily broad, with a
capacious mouth, situated in the under-side of the head.
The body tapers behind, and the caudal portion is unequally
lobed, the upper lobe being much longer than the lower,
upturned and supported by a continuation of the vertebral
column, while the tail-fins of bony fishes are equally lobed
and consequently called Itoinocercal ; those of sharks are
unequally lobed, and are therefore said to be heterocercal. In
tli is respect they resemble an early stage in the development
of bony fishes, such as the trout or herring. Sharks, like
bony fishes, have two pectoral and generally two ventral
fins ; these two pairs of fins corresponding to or homologous
with the limbs of air-breathing Vertebrates, and besides this
there is one or usually two dorsal fins, and an anal fin, the
latter situated behind the vent.
The skin is either smooth or covered with minute placoid
scales (see Fig. 385) ; the integument of such species as
are provided with these fine scales forming shagreen. Whilo
the spinal column is in the sharks usually cartilaginous, and
easily cut with a knife, there are different grades of devel-
opment from certain forms, as the Ghimaera, to a well-marked
416 ZOOLOGY.
column or series of biconcave vertebrae, with the cartilage in
part replaced by bone, forming radiating leaves or plates ;
while in the rays or skates the anterior part of the column
is bony.
The ribs are small, sometimes rndimentarv. The skull is
%t
rudimentary, without membrane-bones, embryonic in char-
acter, forming a simple cartilaginous brain-box, without pre-
maxillary or maxillary bones, the constitution of the jaws be-
ing quite unlike that of the bony fishes, the jaws being formed
of elements, i.e., "cartilaginous representatives of the pri-
mary palatoquadrate arch and of Meckel's cartilage." (IIux
ley.) "
There are no opercular bones such as cover the gill-open-
ings in bony fishes, their place being taken by cartilaginous
filaments.
The mouth is armed in most sharks with numerous sharp,
flattened, conical teeth, arranged in transverse rows and
pointing backwards ; they are never fixed in sockets, but
imbedded in the mucous membrane of the upper and under
jaws. In the Heterodontid.se, represented by Cestracion or
Port Jackson shark, the teeth are much blunter than in
other living sharks, the middle and hinder teeth having
broad, flattened crowns, forming a pavement of rounded
teeth. The Devonian sharks were in most cases like the
Cestracion in this respect. In the Carboniferous age, sharks
with teeth more like those of modern forms came into ex-
istence ; and they must have been of a more active nature,
the sharp teeth directed backward indicating the rapacity of
these monsters, which darting after and seizing their prey
were enabled to retain it by the backward-pointed teeth ;
while the more sluggish Devonian Cestracions kept near the
bottom and devoured the shelled mollusks, etc., possibly Or-
thoceratites, Nautili, and Trilobites, which became nearly
extinct about the time the type of pavement-toothed sharks
culminated.
The teeth of the skates or rays have obtuse points. In
Myliobatis the teeth are flattened and united to form a solid
pavement, so that the mouths of these large rays are fur-
DEVELOPMENT OF SHARKS AND RAYS. 417
nished with an upper and nether millstone for crushing and
comminuting the thick, solid shells of mollusks. The mouth
in both sharks and rays is always situated on the underside
of the head, all being ground-feeders. Such sharks as rise
to the surface for food seize it by turning over before closing
their jaws on the luckless victim.
The throat or oesophagus is wide ; the stomach a capacious
sac, and the intestine short, separated from the stomach by
a pyloric valve. The spiral valve of the intestine is a fold
projecting into the cavity of the gut, the fixed edge forming
a spiral line around the inner wall of the intestine.
The heart consists of a ventricle and auricle, with an
aortic bulb which pulsates as regularly as the heart ; and the
blood must be sent forward with great force, as the very mus-
cular bulb is provided within with three rows of semi-lunar
valves.
The gills are pouch-like, generally five, rarely six or seven,
in number, the external openings or gill-slits being usually
of moderate size, but sometimes long and large, as in the
basking shark. While the clefts open on the side of the
neck in sharks, in the skates they are placed beneath the neck.
A spiracle or opening leads, in some sharks, from the up-
per side of the head into the mouth. According to Wyman
this is the remnant of the first visceral cleft of the embryo.
•/
In the brain the optic thalami are separate from the optic
lobes, the olfactory lobes being large and long in the skates
and some sharks. The medulla forms the larger part of the
brain. The optic nerves unite, as in higher Vertebrates, form-
ing a common stem or chiasma, before diverging to the eyes.
The eyes of some sharks have a third lid or nictitating
membrane analogous to that of birds. The ear, except in
Clnnmra, has the labyrinth completely surrounded by carti-
lage. There are two testes, and usually two ovaries, but in
the dog-fishes and the nictitating sharks there is but a single
ovary. The oviducts are true " Fallopian tubes," expanding
posteriorly into uterine chambers, which unite and open
into the cloaca. (Huxley.)
The sharks and skates are not prolific ; having but few
ZOOLOGY.
enemies they do not lose much ground in the struggle for
life. The oviparous forms such as certain sharks, skates^
and CJtiiiiara, lay large eggs enclosed in tough, leathery,
purse-shaped cases. The other Elasmobranchiates are vivip-
arous, bringing forth their young alive. In J/«,y/f/?/x and
Carcharias a rudimentary "placenta"' analogous to that of
Mammals is developed from the yolk. The following ac-
count of the development of the dog-fish (Muxfclxx). which
is condensed from Balfour, may be found to be applicable to
sharks in general :
The blastoderm or germinal disk is a large round spot
darker than the rest of the yolk, bordered by a dark line
(really a shallow groove). Segmentation occurs much as de-
scribed in the bony fishes, reptiles, and birds. The upper
germ-layer (epiblast) arises much as in the bony fishes, the
Batrachians and birds, while the two inner germ-layers are
not clearly indicated until a considerably later stage. The
segmentation-cavity is formed nearly as in the bony fishes.
There is no invagination of the outer germ-layer to form the
primitive digestive cavity, as in Amphioxus, the lamprey,
sturgeons, and Batrachians, but the Selachians agree with
the bony fishes, the reptiles, and birds, in having the alimen-
tary canal formed by an infolding of the innermost germ-
layer, the digestive track remaining in communication with
the yolk for the greater part of embryonic life by an
umbilical canal. This mode of origin of the digestive cav-
ity, Balfour regards as secondary and adaptive, no "gas-
trula" (Hffickel) being formed as in Amphioxus, etc. The
embryo now rises up as a distinct body from the blastoderm,
just as in other Vertebrates, and there is a medullary groove
along the middle line, and by the time this has appeared the
middle and inner germ-layers are clearly indicated. After
this development continues in much the same manner as in
the chick.
At this time the embryo dog-fish externally resembles the
trout ; the chief difference is an internal one, the outer
germ-layer not being divided into a nervous and epidermal
sublayer as in the bony fishes.
DEVELOPMENT OF SHARKS AND RATS. 419
The next external change is the division of the tail-end
into two caudal lobes. The notochord arises as a rod-like
thickening of the third germ-layer, from which it afterwards
entirely separates, so that the germ, if cut transversely,
would appear somewhat as in the embryo bird.
The primitive vertebrae next arise, and about this time the
throat becomes a closed tube. The head is now formed by
a singular flattening-out of the germ, like a spatula, while
the medullary groove is at first entirely absent. The brain
then forms, with its three divisions, into a fore, middle, and
hind brain. Soon about twenty primitive vertebrae arise,
and by this time the embryo is very similar, in external
form, to any other vertebrate embryo, and finally hatches in
the form of the adult.
The skate was found by Wyman to be at first long and
narrow, the dorsal and anal fins extending to the end of the
tail, as in the eel. Soon after it becomes shark-shaped, and
finally assumes the skate form. Thus skates pass through
a shark-stage, and this accords with the position in nature
of skates, since they are, as a whole, a more specialized as
well as more modern group than the sharks. Wyman found
that there are in the skate at first seven branchial fissures,
the most anterior of which is converted into the spiracle,
which is the homologue of the Eustachian tube and the
outer ear-canal ; the seventh is wholly closed up, no trace re-
maining, while the five others remain permanently open.
The Elasmobranchs are subdivided into two orders (re-
garded by Gill as super-orders, the Plagiostomi, represented
by the sharks and rays, and the Holocephali, the type of
which is Chimcera.
Order 1. Plagiostomi. — In the sharks and skates the teeth
are very numerous ; the gill-slits are uncovered. The rays
or skates differ from the sharks in their broad, flat bodies,
with the gill-slits opening below ; the great breadth of the
body is due to the enlargement of the pectoral fins which
are connected by cartilages to the skull ; there is likewise no
median articular facet upon the occiput or base of the
skull, for the first vertebra.
The most common of our Selachians is the mackerel shark
420 ZOOLOGY.
or Isurus punctatus (Fig. 389). The head is conical, with
the nostrils under the base, and the lobes of the tail are
nearly equal. It is from four to eight feet in length, and is
often taken in fish-nets, being a surface-swimmer. In the
thresher shark (Alopecias vulpes Cuvier), the upper lobe of
the tail is nearly as long as the body of the shark itself. It
grows twelve or fifteen feet in length, and lives on the high
seas of the Atlantic.
Nearly twice the size of the thresher is the great basking
shark, Selache (Cetorhinus) maxima Cuvier, of the North
Atlantic, which becomes nine to thirteen metres (thirty or
forty feet) in length. It has very large gill-slits, and is by
no means as ferocious as most sharks, since it lives on small
Fig. 389.— Mackerel Shark.— From Tenney's " Zoology."
fishes, and in part, probably, on small floating animals, strain-
ing them into its throat through a series of rays or fringes of
an elastic, hard substance, but brittle when bent too much,
and arranged like a comb along the gill-openings, the teeth
being very small.
Among the smaller sharks is the dog-fish (Squalus Ameri-
canus Storer), distinguished by the sharp spine in front of
each of the two dorsal fins. It is caught in great numbers
for the oil which is extracted from its liver. The dog-shark
(Mustelus canis Dekay), which is a little larger than the
dog-fish, becoming over a metre (four feet) long, brings forth
its young alive. In the European Mustelus ICBVIS Risso a
so-called placenta is developed, while it is wanting in the
Mustelus vulgaris of Miiller and Henle.
SHAKKS AND BAYS.
421
Among the more aberrant sharks is the hammer-headed
SpJiyrna zyycena (Linn.), which grows to the length of twelve
feet, and is one of the most rapacious and formidable of the
order.
Of the rays and skates, the saw-fish approximates most
to the sharks. Its snout is prolonged into a long, fla»
bony blade, armed on each side with
large teeth. Pristis antiquarian
Latham (Fig. 390), the common saw-
fish, inhabits the Mediterranean Sea
and the Gulf of Mexico ; it is vivipa-
rous (Caton. ) Pristis PerroteU lives
in the Senegal River, while Car char ias
gangeticus is found sixty leagues from
the sea.
The genuine skates or rays have the
body broad and flat, rhomboidal (ow-
ing to the great extension of the
thick pectoral fins). Portions of the
ventral fins in the males are so elon-
gated and modified as to form intro-
mittent and clasping organs. They
swim close to the bottom, feeding upon
shell-fish, crabs, etc., crushing them
with their powerful flattened teeth.
The spiracle is especially developed in
the rays, while, as observed by Gar-
man, in the majority of the sharks
which swim in midwater or near the
surfac.1, the water enters the mouth
and passes freely out of the gill-open-
ings, but in the rays, which remain at
the bottom, the purer sea-water enters
the spiracle from above to pass out of
the gill-slits.
The smallest and most common skate of our northeast-
em Atlantic coast is Raja eriuacea Mitclnell. It is one half
of a metre (twenty inches) in length, and the males are
smaller than the females. The largest species is the barn-
door skate, Raja Icevis Mitchell, which is over a metre (forty-
of S;i\v-fisli,
,-lio\ving its
lateral
422
ZOOLOGY.
two inches) long. Raja eglanteria Lacepede (Fig. 391)
ranges from Cape Cod to the Caribbean Sea. The smaller
figures in Fig. 391 represc-nt respectively the mouth and
gill-slits, and the jaws of Myliobatis fremenvillii Lesueur.
In the torpedo the body is somewhat oval and rounded.
Fig. 392 represents Torpedo marmoratus, of the Mediter-
ranean Sea.
Our native species, found mostly in winter, especially
on the low sandv
*•
shores of Cape Cod,
is Torpedo occiden-
tal is Storer. Its bat-
teries and nerves are
substantially as in
the European spe-
cies. The electrical
organs are construct-
ed on the principle
of a Voltaic pile,
consisting of two
series or layers of
hexagonal cells, the
space between the
numerous fine trans-
verse plates in the
cells filled Avith a
trembling jelly-like
mass, each cell
representing, so to
Fig. 391.— Raja eglanteria, male. Mouth and gill- speak, a Leydoil jar.
slits, jaws and teeth of Myliubatlg fremt nvillii j . ml , '
There are about 4,0
cells in each battery, each provided with nerves sent off from
the fifth and eighth pairs of nerves. The dorsal side of
the apparatus is positively electrical, the ventral side nega-
tively so. The electrical current passes from the dorsal to
the ventral side. When the electrical ray is disturbed by the
touch of any object, the impression is conveyed by the sen-
sory nerves to the brain, exciting there an act of the will
which is conveyed along the electric nerves to the batteries,
THE ELECTRICAL RAT.
423
producing a shock. The benumbing power is lost by fre-
quent exercise, being regained by rest ; it is ulso increased
by energetic circulation and respiration. As in muscular
S
Fig. 392. — To pe<lv ntariiutratus. c, cerebrum : b, the medulla ; c, spinal cord ;
</and &', electric portion of the trigeminaie or fifth pair of nerves ; ee', electric portion
of tin- pneumogastric or eighth pair of nerves ; ./', ivcunvnt nerve ; g, left electric
organ entire ; g', right electric organ dissected to show the distribution of the nerves ;
h, the last of the branchial chambers ; i, mucus-secreting tubes.— From Gervais and
Van Beni-den.
exertion the electrical power is increased by the action of
strychnine (Owen).
Marey has more recently made interesting experiments on
the torpedo, examining the discharge of this n'sh with the
ZOOLOGY.
telephone. Slight excitations provoked a short croaking
sound. Each of the small discharges was composed of a
dozen fluxes and pulsations, lasting about one fifteenth of a
second. The sound got from a prolonged discharge, how-
ever, continued three to four seconds, and consisted of a sort
of groan, with tonality of about mi (165 vibrations), agree-
ing pretty closely with the result of graphic experiments.
Marey has also studied the resemblance of the electrical
apparatus of the electrical ray or torpedo and a muscle.
Both are subject to will, provided with nerves of centrifugal
action, have a very similar chemical composition, and re-
semble each other in some points of structure. A muscle in
contraction and in tetanus executes a number of successive
small movements or shocks, and a like complexity has been
proved by M. Marey in the discharge of the torpedo.
The sting-rays (Trygori) have no caudal fin, but the spinal
column is greatly elongated, very slender, and armed with a
long, erect spine or "sting." Some live in fresh water;
several species of sting-rays (Potamotrygon) inhabit the large
rivers of Brazil and Surinam, as the Amazon, Tapajos, Ma-
deira, and Araguay, digging holes in the sand, in which they
lie flat and await their prey. In this connection it may be
said that Raja fluviatilis of India has been taken near Ram-
pur, nearly 1000 miles above tide-reach.
Myliobatis has the teeth forming a solid plate or pavement.
The devil-fish (Oephalopierus diabolus Mitchell) of the coast
of South Carolina and Florida is the largest of our rays, be-
ing eighteen feet across from tip to tip of its pectoral fins,
and ten feet in length, weighing several tons. It sometimes
seizes the anchors of small vessels by means of the curved
processes of its head and swims rapidly out to sea, carrying
the craft along with it.
Order 2. Holocephali. — This small but interesting group
is represented by Chimcera of the north Atlantic, and Cal-
lorhynchus of the antarctic seas. In these fishes the four
gill-openings are covered by an opercular membrane ; thus
approaching the true bony fishes, and there are but four teeth
in the upper and two in the loAver jaw. The brain of Chi-
masra is said by Wilder to combine characters of those of
GANOID FISHES. 435
Selachians, Ganoids, and Batrachians. Chimcera plumlea
Gill lives in deep water off the coast of New England.
Subclass 2. Ganoidei (dlarpikes, Mud - Fixlti'*). — The
term Ganoid was applied to these fishes from the form of
the scales, which in most of the species are angular, square,
or rhomboidal and covered with enamel, as seen in the com-
mon garpike. In others, however, as in the Amia and Dip-
noans, the scales are rounded or cycloid. These fish, i.e.,
including Pterichthys and Cephalaspis, were the character-
istic fishes of the Devonian age, which has consequently been
called the Age of Fishes, there being no bony fishes (Teleos-
tei) at that time. The forms were much larger than at
present, far more numerous in species, genera, and families,
and they, with the sharks, were the rulers of the sea.
At the present day the type is nearly extinct, being repre-
sented by such isolated forms as the sturgeon, the paddle-
fish, the Si-apliirliynchops, the garpikes, and the American
mud-fish (Amia}. Like most of the palaeozoic types of life,
the Ganoids were both generalized forms and also combined
the characters of classes of animals not then in existence ; in
other words they were synthetic or comprehensive types.
Thus in forms like Amia, the Teleostean fishes were antici-
pated ; in the Dipnoi, with their external gills and lungs,
not only the Amphibians, but even the reptiles were indica-
ted in their hearts with two auricles, just as the Trilobites and
Merostomata, as indicated by the structure of the living
king-crab, combined with the structure of Crustaceans, fea-
tures which became in a degree reproduced in the terrestrial
scorpions and spiders which subsequently appeared. Owing
to this intermixture of ancient and modern characteristics,
this reaching up and out of the piscine type of life over into
the amphibian and reptilian boundaries, the classification,
i. e., actual position in nature of the Ganoids, becomes very
difficult, and the views of naturalists regarding their system-
atic position are very discordant. If, as insisted on by Gill,
we recognize the fact that the Ganoids are an older, more
generalized, and therefore more elementary group, and the
osseous fishes a newer, more highly specialized group, and
426 ZOOLOG T.
that there is a natural series of forms leading from the stur-
geon, which is nearest the Elasmobranchs, up through the
spoon-bill to the true Ganoids, and that the latter, through
Anu'a, leads to the bony fishes, we shall have a clue to the
intricate relations existing between them and the other sub-
classes of fishes.*
The Ganoids of the present day are well nigh confined to
fresh water, the sturgeons alone living in the sea as well ;is
ascending rivers ; though the Devonian and carboniferous
forms occur as marine fossils.
In synthetic forms, like the Ganoids, it is difficult to find
absolute characters separating them from the Elasmobranchs
•on the one hand and the Teleosts on the other. The diag-
nostic characters are the following: the skeleton is either
wholly cartilaginous, or partly or wholly bony ; the skin is
either smooth, or with cycloid, or usually with ganoid scales ;
the gills are free ; the gill-opening is covered with an opcr-
cular bone ; the first fin-rays generally sharp ; the air-blad-
der with a pneumatic duct ; the embryos sometimes with ex-
ternal gills.
The spinal column is usually cartilaginous ; in the Pip-
noans, the sturgeons, the paddle-fish and allies, the notochord,
with its sheath, is persistent ; while in Polypterus and Aniia
the spinal column is completely bony, the vertebra? being
ampliiccelom, i. e., biconcave ; while in the garpike (Lepidox-
teus) the vertebras are convex in front and concave behind.
The cartilaginous skull is covered by broad, thin membrane-
bones, as seen in the sturgeon. The tail is heterocercal, the
lobes being, in Amin, nearly equal.
The brain is as in the bony fishes, but the optic nerves
unite in a chiasma. The heart and aortic bulb are as in the
Elasmobranchs, and all but Lepidfix/cit* have a well-devel-
oped spiral valve in the intestine, the valve being rudimentary
* For works on Ganoids, see Wilder's Garpikes, Old and Young (Pop.
Sc. Monthly, 1877); A. Agassiz's Development of Lepidosteus (Proc.
Ainer. Acad. Arts and Sc., 1878); Bill four and Parker's Structure
and Development of Lepidosteus (Phil. Trans., 1882); Shufeldt's
Osteology of Amia calva, 1885; Ryder's Sturgeons, etc., of Eastern
TJ. S., 1890; Mark's Studies on Lepidosteus (Bull. Mus. C. Zool., 1890);
with the writings of J. Miiller, Hyrtl, Kolliker, Gegeubaur, Liitken,
Boas, Hertwig, Garmau, etc.
[To face page 426.]
DEVELOPMENT OF THE STURGEON. 427
in the garpikes. The oviducts communicate with the ure-
ters as in the sharks and amphibians. The different modifi-
cations of Ganoid structure may be observed in the examples
of the different orders.
Many of the Ganoids of the Upper Silurian and Devonian
rocks belonged to the groups Cephalaspidce and Placoder-
mata. In the Cephahispids, represented by the singular
Cephalaspis Lyellii of Agassiz, the broad head was covered
by a single semi-circular plate, with large orbits above, the
mouth being below. The pectoral fins were rayless folds of
the skin ; the body behind the head was covered with rhom-
boidal scales, and provided with a dorsal fin. The Pteraxpis
had a head-shield composed of seven pieces. Among the
Placoderms, Pterichthys had a plated head half as long as
the body, the tail short and scaled. These fishes, the earliest
known Vertebrates, were bottom-feeders. Nothing is known
as to the nature of their jaws or teeth.
Order 1. Ghondroganoidei. — In these Ganoids the dorsal
chord is not ossified ; the skull is cartilaginous, covered with
membrane-bones ; they are either toothless or with small .
teeth. The skin is naked as in the paddle-fish, or protected
as in the sturgeons with very large, bony, solid plates. The
sturgeons have the snout long and pointed, with the mouth
underneath, and toothless. Acipenser sturio Linn, is the
common sea-sturgeon of our coast, ascending rivers. The
shovel-nosed sturgeon, Scaphirhyncliops platyrhynchus has a
spade-like snout. It inhabits the waters of the Mississippi
Valley. Salensky has studied the embryology, of the Russian
sturgeon. The freshly-laid eggs are two millimetres in di-
ameter, the yolk undergoes nearly total segmentation, thus
connecting most Vertebrates in which the eggs only partially
segment, with the Amphioxus, lampreys, and amphibia, in
which segmentation is total. The skeleton is developed
much as in the Elasmobranchs. The sheath of the noto-
chord develops in three weeks after hatching. At the
end of the third week the upper and lower vertebral arches
appear, arising as in other fishes. The skull is indicated in
two or three weeks after hatching.
428
ZOOLOGY.
<h
The singular spoon-bill, Poli/»t/<»t folium Lacepede, is five
feet long; it is smooth-skinned und has a snout one-third as
long as the body, and spatulate, with thin edges. It has
a very wide mouth with minute teeth,
and lives on small Crustacea. It abounds
in the Mississippi and its larger tribu-
taries.
Order2. Branchioganoidei, — Here be-
longs the Polypterits of the Nile and
Senegal. In these Ganoids the tail is
either protocercal or heterocercal ; the
scales are cycloid or rhomboid. The
dorsal fin is long, subdivided into divis-
ions, each with a separate ray and spine.
Polypfents bichir Geo&roy (Fig. 393) has
a protocercal tail. The young has exter-
nal gills (Fig. 394). It inhabits the river
Fig. 394.— External gills of a young Polypterus bichir.
hi; external gills.
Nile, P. seneyalus the Senegal. Cola-
moichthys differs in having no ventral
fins and in its elongated form. It inhabits
the rivers of Old Calabar. Allied to
these living forms are the Devonian 0$-
teolepis, Ccelacantltux, and Hulopt ychins.
Order 3. Hyoganoidei. — This group is
represented by the garpike and Amid or
mud-fish of the United States, which
is an annectant form connecting the
Ganoids with the Teleosts. In these
Fig. 393. — Polypterus r. , ,-, -11 i .LI
bichir.— From Cuvier. fishes the spinal column is bony, tlie
tail partially heterocercal.
In Lepidosteus (Fig. 395, L. oxwns Agassiz) the body is
long, the jaws long and armed with sharp teeth, the vertebrae
are opisthocoelous, and the scales are large and rhomboidal,
(.1AKP1KE. 429
while the air-bladder is cellular, lung-like. Fossil species oo-
cur with those of Amia in the tertiary rocks of the West.
Lepidosteus O.VNVMX Agassiz, the bony gar, with a long, slender
snout is sometimes five feet long; L. plutyxtomns Kafin.
has a short nose, while the alligator gar, L. spatula Lace-
pede, has a short and wide snout, and grows to a larger size
(nearly three metres) than the other species, and inhabits
the Mississippi Valley. The garpikes are carnivorous, very
rapacious, and are said to destroy large numbers of food-
fishes. They usually remain near the surface of the water,
emitting bubbles of air and apparently taking in a fresh
supply. Wilder has observed Amia inhaling air, and re-
marks that " so far as the experiments go, it seems probable
that, with both Amia and Lepidosteus, there occurs an inha-
lation as well as exhalation of air at pretty regular intervals,
the whole process resembling that of the Mcnobranclius and
other salamanders, and the tadpoles, which, as the gills
Fig. 39o. — Garpike. From Tenney's Zoology.
shrink and the lungs increase, come more frequently to the
surface for air." Both of these fishes are very tenacious of
life and withstand removal from water much better than
bony fishes and sturgeons, on account of the lung-like nature
of their air-bladder. Wilder shows that there is a series of
forms, mostly Ganoids, from the Amia and Lepidosteus in
which the pneumatic duct enters the throat on the dorsal
side, up to Lepidosiren in which it enters the throat on the
ventral side, like the air-tube or trachea of Amphibians and
higher Vertebrates.
The breeding habits and external changes in form of the
garpikes have been described by Mr. A. Agassiz. The gars,
which are nocturnal in their habits, appear on the shores of
Lake Ontario,near Ogdensburg,in immense numbers between
430
ZOOLOGY.
the middle of May and the 8th of June, remaining at other
times of the year in deep water.
The young begin to hatch about the end of May. At
first the embryo gar possesses an unusually large yolk-sac,
while the notochord is very large ; otherwise posteriorly it
resembles the young of bony fishes. It differs, however, in
its large mouth, which is surmounted with a hoof-shaprd
depression edged with a row of projecting suckers, by which
it attaches itself, hanging immovable, to stones ; the eye and
brain is smaller than in bony fishes. The tail is at first
protocercal, beginning on the second day to become hetero-
cercal. On the third day the gill-covers form rectangular
flaps, and the first traces of the pectoral fins appear, while
the snout becomes longer. By the fifth day the traces of
the dorsal, caudal, and anal fins appear. When a little over
three weeks old it assumes a more fish-like form ; the suck-
ing disk has nearly disappeared, the lower jaw greatly length-
ened, and the gill-covers extend to the base of the pectoral
fins. When between two and three weeks old the young
gar-fish is 20 millimetres (f inch) long. The young rise to the
surface to swallow air, as in the adult. Soon after this it is
of the form first discovered and figured by Wilder. The
gar-fish, according to Agassiz, bears some resemblance to
the sturgeon in certain stages of growth, and in the forma-
tion of the pectoral fins from a lateral fold, as well as by the
mode of growth of the gill-openings and the gill-arches, while
it closely resembles the young of bony fishes in the develop-
ment of the posterior part of the body, by the mode of origin
of unpaired fins from the embryonic fin-fold, and by the
mode of formation of the fin-rays, and of the ventral
fins.
The mud-fish, Amia calva Linn., is like an ordinary bony
fish in form, with rounded scales; the caudal fin "masked
lieterocercal," the snout is short and rounded, and the air-
bladder is large and cellular. It attains a length of two
thirds of a metre, and occurs in the Mississippi Valley and
as far east as New York. A fossil form closely allied to
Amia dates back to the Cretaceous Age, and the genus
lOaturus is a Liassic and Oolitic genus.
ANATOMY OF THE GUNNER. 431
Subclass 3. Teleostei (Bony fishes).— We now come to a
type of fishes which, within very recent geological times as
well as during the present period, has become differentiated
or broken up into thousands of species, corresponding to
the complexity of their physical environment as compared
with the simple features of the physical geography of De-
vonian and Carboniferous land-masses. Like most of the
larger groups of animals, as the Decapod Crustacea, and
especially the insects, as well as the mollusks, the bony
fishes have attained an astonishing amount of specialization,
as if the tree of icthyic life, taking root in the Silurian Age,
and sending out but a few branches in later Palaeozoic times,
had suddenly, in the Cretaceous and Tertiary Ages, thrown
out a multitude of fine branches and twigs intertwining and
spreading out in a way most baffling to the systematist.
The essential, diagnostic characters of the bony fishes, i.e.,
such as separate them from the Elasmobranchs and Ganoids,
are as follows : The skeleton is bony, the vertebras being sep-
arate ; the outer elements of the scapular arch are simple, the
inner elements for the most part bony and usually three or
two in number ; the pectoral fins are without any bone rep-
resenting the humerus, and are connected with the scapular
arch by several (generally four) narrow bones (Gill). The
optic nerves cross one another. The gills are free, usually
four on each side, and with several opercular bones. The
heart is without a cone, but with an arterial bulb, and with
but two values at the origin of the aorta. The intestine is
destitute of a spiral valve.
The student should dissect a typical Teleost, such as a
fresh-water or sea perch, with the aid of the following ac-
count of its anatomy. The drawing and account here given
of the anatomy of the sea-perch have been prepared by Dr.
C. Sedgwick Minot. The common sea-perch or cunner
(Tautogolabrus adspersus Gill, Fig. 396) resembles the fresh-
water perch very closely in its anatomy, the most note-
worthy difference being the absence of the cceca at the
pyloric end of the stomach in the marine species ; with this
exception the following description applies almost equally
well to the fresh-water perch, so that this account will be
ZOOLOGY.
available for western students who have not access to speci-
mens of the cunner.
The perch has the general form of a flattened spindle, for
it tapers down at either end and is compressed laterally.
There is no neck marked off externally, and the head ap-
pears as the direct continuation of the body, but separated
from it by a fissure on either side ; this is the opening of
the gills, which extends from above downwards and curves
forward, nearly meeting its fellow on the median line of the
under jaw ; upon opening the gill-slit the pectinate or comb-
like gills or branchiae are seen within. There are four sets
of branchial filaments, each set attached to a separate de-
scending arch, in front of each of which is a slit leading into
the cavity of the mouth ; but there is no slit behind the
last gill. The branchiae are protected externally by the gill-
cover or operculum, which is attached in front, but is free
behind, where it forms the front edge of the gill-slit ; it is
composed of four distinct parts : 1. The praeoperculum
nearest the eye, and with its lowest corner almost a right
angle ; its posterior and vertical edge is furnished with
numerous minute projecting spines. 2. Appended to the
underside of the margin thus armed is the operculum. 3.
Below the praeoperculum is the interoperculum, which par-
tially covers up 4, the suboperculum. Each of these parts
has a separate bony support ; all four bones are developed
only in the Teleosts ; in sturgeons, for example, there is
only an operculum, to which in other Ganoids other parts
are added ; in Selachians the whole apparatus remains
undeveloped.
The mouth is placed in front ; the upper lip is capable of
independent motion, b?ing supported by the praemaxillary
bones, which are but loosely attached to the cranium, though
in many other fishes the union is closer. The eyes are large
and lidless ; just in front of each eye is an opening of the
size of a pin's head ; these openings lead into the nasal sacs,
of which there are two, but both are without communica-
tion with the mouth ; in higher vertebrates, from the Dip-
noi upwards and in .l///./-//ie, there is such a communication.
In the MarsipobrancMi there is but a single median nasal sac.
ANATOMY OF THE GUNNER 433
The ear has no external opening, being completely encased
in bone. Nearly parallel with the line of the back extends
a continuous row of yellow spots marking the lateral line
(Fig. 396, L), along which are found the pore-like open-
ings of the so-called muciparons glands.
All fish have fins of two kinds — unpaired and paired ; the
latter, four in number, correspond to the limbs of other Ver-
tebrates. The unpaired fins are first developed on a contin-
uous median nap of integument, which extends along the
back, around the tail, and on the underside as far forward as
the anus ; cartilaginous or bony rays are developed in it as a
support. In the adult fish the fold is generally discontinu-
ous, being usually separated into three distinct fins — dorsal,
caudal, and anal ; the dorsal fin is frequently, the anal fin
sometimes subdivided. The fin-rays are (1) either simple
pointed rods, or (2) jointed and branching. All the rays of
the caudal fin, and the posterior rays of the dorsal and anal
fins, are branching. In some Malacopterygians all the rays
are branching ; in many, however, the first ray is simple in
the dorsal and anal fins, while fishes like the perch and din-
ner are distinguished by having several or many of the an-
terior rays of the dorsal and anal fins simple and pointed.
In the dinner half the rays of the dorsal and the first two of
the anal fin are simple.
The pectoral fins are attached to the side of the body and
are large and rounded. The ventral fins lie further back
near the median ventral line ; they are smaller than the pec-
torals. The position of the ventrals varies in different fish,
and is much used in classification. The anus lies immedi-
ately in front of the anal fin.
The body is covered by scales, which overlap one another
from before backward ; their free edges are rounded and
smooth, hence they are called cycloid. These scales, as in
all Teleosts, are ossifications of the underlying cutis, and are
covered by the epidermis ; they were formerly wrongly sup-,
posed to be epidermal structures.
To dissect a perch the side-wall of the mouth must be re-
moved, then the gill-cover ; study the arrangement of the
gills. Next make an incision along the median ventral line
434 ZOOLOGY.
from the level of the pectoral fins to just before the anus, and
following the upper edge of the body-cavity upward and for-
ward cut away the body-wall, taking care not to injure the
large swimming-bladder above, nor the heart in front. Now
open the pericardial cavity, which lies ventrally immedi-
ately behind the gills (see Fig. 39G, Ht}. Cut away the mus-
cular masses around the back of the head ; expose the cavity
of the brain, and remove the loose cellular tissue around the
nervous centres. If the gills of one side are excised and the
intestine drawn out, the dissection w'll appear very much as
in Fig. 396.
The cavity of the mouth widens rapidly and continues as
the branchial chamber or pharynx (G), whence we can pass a
probe outward through any of the gill-slits. There is a single
row of sharp-pointed teeth in front on both the under and
upper jaws ; in the pharynx above and below there are
rounded teeth. At the side of the pharynx are the four gill-
slits and the four arches ; the inner surface of the anterior
three arches is smooth, while the arch behind the fourth slit
is much modified in shape and is armed with tubercles
and teeth. The entrance of each slit is guarded in front
and behind by a row of projecting tubercles appended to the
arches. On the outside of each arch, except the fourth, is
a double row of filaments, richly supplied with blood-vessels
which, shining through, give a brilliant red color to the
gills ; on the fourth arch there is but a single row. At the
upper and posterior corner of the pharynx is the sma'l open-
ing of the short oesophagus. The branchial chamber has an
upward extension on the sides of which lie the pseudobran-
chite (Ps), accessory respiratory organs not connected with
the gills proper, and receiving their blood-supply from distinct
arteries. There are no salivary glands.
The oesophagus dilates almost immediately to form the
stomach (partly concealed in the figure by the liver, Li),
which seems hardly more than a dilatation of the intestine
(In}. This last is of nearly uniform size throughout, and after
making three or four coils terminates at the anus, immedi-
ately in front of the urinary and genital apertures. When
in situ, the terminal portion of the intestine or the rectum
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Fig. 3966.— Swimming-bladder (S, anterior, S', posterior, division) of the bleak;
as. oesophagus; I, air-passage of the air-bladder leading into the oesophagus.
Fig. 396c.— Circulation of the blood in a bony fish, an, auricle; ven, ventricle;
bar, bulbus arteriosus; ao, aorta; 60, one of the four branchial arteries which
carry the blood to the gills, and afterwards unite to form the descending aorta
(dao); pc, portal circulation; vc, great descending vein (vena cava); kid, kidney.
Fig. 396d.— The structure of the minnow and the living fish. B— n. nose; A — n,
nose-pit; gc, gill-cover; a.f, pectoral or arm-fin; If, leg-fins or ventrals; rf/, dorsal
fin; sf, anal tin; cf. <¥aii(ial fin; MS. mucous scales of the latenil line; e, optic
nerve; ea, par-nerve leading from the brain; f/, gills; h, heart; t, oesophagus; s,
stomach; fc, kidnev: r. \ent; da, dorsal artery; «, air-bladder; b, back-bone;
nv, nerve-cord or spinal cord.
[To fitci- paije 435.]
ANATOMY OF THE CUNNER. 435
extends straight along the median ventral line. The liver
(Li) forms an elongated light-brown mass resting upon the
stomach. The elongated gall-bladder lies between the
liver and stomach, somewhat imbedded in the substance of
the former. There is no pancreas, though it is present in
some fishes. The spleen (Sp) lies between the stomach and
intestine, in the mesentery ; it is dark reddish-brown in
color.
The air-bladder (S) is a single large sac, placed in the dor-
sal part of the body-cavity. Its glistening walls are com-
posed mainly of tough fibrous tissue. The pneumatic duct,
by which the bladder communicates with the oesophagus in
many fishes, is wanting in the perch as in nearly all other
Teleosts. The air-bladder normally contains only gases. It
conceals most of the kidneys, which extend the whole length
of the body-cavity on either side of the middle line, as two
long strips of a deep though dull red. They project beyond
the air-bladder in front (Ki) and behind (AT). Their an-
terior ends are somewhat separated from one another by the
intervening pharynx. The ureters open into a urinary
bladder (11} behind the anus.
The ovary is single and varies greatly in size according to
the season. In the male the sexual glands are double. Each
testis ( i ) is an elongated, whitish, tabulated organ, placed im-
mediately below the swimming-bladder, and continues pos-
teriorly with the spermiduct, which opens immediately be-
hind the anus.
The heart (fft) lies in the triangular pericardia! cavity ; it
consists of two portions, the dark-colored venous chamber,
or auricle, above, and the lighter-colored arterial chamber, or
ventricle, below. The auricle receives from above two large
veins, one from either side ; these veins are called the ditrfi
( '"fieri. Each Cuvierian duct, as can be seen in the figure,
ascends beside the oesophagus, and there receives a large jug-
ular vein from in front, and a large cardinal vein fr.om be-
hind. Furthermore, a large vein, the sole representative of
the vena cava of higher Vertebrates, passes from the liver,
near its anterior end, through the pericardium, and empties
into the Cuvierian ducts near their common auricular orifice.
43G ZOOLOGY.
The walls of the auricle are comparatively thin ; the auriculo-
ventricular orifice is provided with valves, which prevent
the blood flowing back into the auricle. The walls of the
ventricle are thick and very muscular ; from the upper end
of the ventricle close to the base of the auricle springs the
bulbus (irfcrinsus, a muscular cylinder, which, running hori-
zontally forward, passes out through the pericardium, and is
continued as the less muscular aorta (.4) underneath the
branchial arches along the median line ; the aorta gives off
branches on both sides, one to each arch to supply the bran-
chiae ; the vessels after ramifying are gathered together, to
again form a single trunk, which passes backward immedi-
,B
Fig. 396 —Anatomy of the Gunner, male. L, lateral line ; fft, heart ; G, pharynx ; P«,
peeuaobranchia ; .Sp, spleen ; S, air-bladder ; £1, Ki', kidneys ; bl, bladder ; T, tes-
tis ; A, aorta ; B, brain ; In, intestine ; Z,i, liver ; G, gills.— Drawn by C. S. Minot.
ately underneath the spinal column ; it is called the descend-
ing aorta.
The body and pericardia! cavities are called serous, because
their lining membranes are always moist with serum, a watery
fluid, very much like blood-plasma. The lining of the body-
cavity is named the peritoneum, and forms a continuous cov-
ering around the viscera. It is important to observe that the
various organs simply project into the body-cavity and do
not lie really inside of it. In fishes we find the disposition of
the parts to correspond more closely with the fundamental
type of Vertebrate structure than it does in higher forms, in
which further modifications have supervened. The pharynx
still has its distinctive character ; the pericardium lies at tlvj
ANATOMY OF THE GUNNER. 437
base of the neck, instead of in the thorax as in the higher Ver-
tebrates. The heart still preserves its primitive division ; on
the other hand, the swimming-bladder is a special adaptation
of the piscian type, while the frequent absence of the pan-
creas is a peculiarity of fishes the meaning of which is not
yet understood.
The brain (B) does not occupy the whole of the cranial
cavity, but is imbedded in a large accumulation of cellular
tissue. In order to study the brain satisfactorily, it should
be exposed from above, laying bare at the same time the optic
nerves and muscles. The two olfactory lobes are followed
by two lobes (H), the cerebral hemispheres, and immediately
behind them two larger lobes (Q), the corpora bi- or quadri-
gemina (optic lobes, not optic thalami) ; further back follows
.a single median lobe (Cb), the cerebellum, somewhat conical
in shape and resting upon the medulla oblongata (M], from
which spring various nerves, and which, tapering backward,
is continued as the spinal cord. In front appear the very large
and conspicuous optic nerves (Op), the right nerve passing
obliquely to the left eye, the left nerve to the right eye
running under the right nerve, but forming no chiasma;
each optic nerve is a plaited membrane, folded somewhat
like a fan when shut up, an arrangement occurring only
among fishes. In a side-view of the brain (Fig. 400, JJ), the
mode of origin of the optic nerves and their origin from the
optic lobes can be clearly seen ; it further shows the various
forms of the lobes of the brain, and the large inferior lobes
(L) below the corpora quadrigemina ; these lobes are very
remarkable and difficult to homologize.
The eyes lie in two sockets, separated by an interorbital
septum (Fig. 397, S). The eyeball has the form of an ob-
late spheroid, and is moved, as in all Vertebrates, by four
recti and two obliqui muscles. The recti spring from around
the exit of the optic nerve from the brain-case, and thence
diverge to be inserted into different parts of the eyeball ;
above is the rectus superior (Rs) ; towards the interorbital
septum (S) rectus interims (Ri), opposed to the last is the
rectus externus (Re), and below is the rectus inferior, not
.shown in the figure. In Teleosts both oblique muscles, the
438
ZOOLOGY.
superior (Os) and inferior (Oi), arise from the front of the
orbit near the interorbital septum. The disposition of the
Fig. 397.— Anatomy of the brain of the Gunner, dorsal and side view. B. 01, olfac-
tory lobea ; the crura and the thalami not represented.— Drawn by C. S. Minot.
recti is very constant, but the obliqui vary considerably in
their origin in different Vertebrates.
If a perch be cut through transversely, so that the section
passes through the fore-part of the
air-bladder, and the anterior portion
then looked at from behind, a very
instructive view will be obtained, as
in Fig. 398. The best sections can be
made by first freezing the fish. The
vertebral column ( F) appear? a little
above the middle ; overlying it is the
neural canal with the spinal cord ; im-
mediately below it is the descending or
dorsal aorta (Ao), on either side of
which follow the kidneys (A"), resting
directly upon the air-bladder (Bl).
Lowermost is the body-cavity, with
the stomach (S'), and intestine (In),
In
surrounded by the liver, which has &naotCunner--Drawn by Cl s
been almost entirely removed. The
rest of the section is occupied by muscles, which, it will thus
be seen, make up the main bulk of the body. (Minot.)
MUSICAL FISU. 439
The so-called " mucous canal" or lateral line of fishes and
Amphibians is sensory. It consists of small masses of
nerve-epithelium, arranged in linear series along the sides of
the head and body, having hair-cells continuous with nerves.
They are called ''nerve-buttons" or " nerve-heaps." Accord-
ing to Schultze, their office appears to be to appreciate mass-
movements of the water, and more particularly vibrations,
which have longer periods than those appreciated by the ear
(Dercum). In the blind-fish of the Mammoth Cave a row
of sense-papillae is situated on the front of the head, sup-
plied with nerve-fibres sent from the fifth pair of nerves
(Wyman).
The angler (LopJiius piscatorius) has long been known to
possess hinged teeth, capable of being bent inward toward
the mouth, but by virtue of the elasticity of the hinge at
once resuming the upright position when pressure is removed
from them. Andbleps and Pcecilia have also 'movable teeth.
The hake, a voracious predatory fish, and in a less degree
other Gadidce, are possessed of hinged teeth.
The nature of respiration is intimately connected with the
production of sounds by fishes. Recent researches by Jobert
on certain unusual modes of breathing in fishes are of special
interest. He has examined certain fishes of the Amazons,
i.e., species of Callichtliys, Doras, Erithrinus, Hypostomus
and Sudis (/If/as or "pirarucu" of the natives, the latter being
allied to the herring. In the Callichthys the intestine is trans-
formed into a respiratory organ. When the water dries up
it emigrates to other pools or streams, creeping by means
of its pectoral fins. This fish can live twenty-four hours
out of the water with impunity.
In the gigantic pirarucu, the swimming-bladder is a long-
sac, and the upper part does not look like that organ, being
spongy, areolar, reddish - brown, friable, and intimately
pressed to the dorsal and lateral walls of the body ; its color
recalls that of the lungs of a bird, and functionally it re-
sembles the latter. •
Among accessory breathing organs are the lamellate cavity
of the Anabas, and the sac-like appendages which are in con-
nection with the gill-cavity, and extend under the muscles
440
ZOOLOGY,
of the body of AmpJiipnous cucliia, Gymnarchus and Sacco-
branchus zincjio.
The noises produced by certain fishes are due primarily to
the action of the pneumatic duct and swimming-bladder,
while different kinds of noises are made accidentally or in-
voluntarily by the lips or the pharyngeal or intermaxillary
bones, as in the tench, carp and a large number of other
fishes. Over fifty species of fish are known by Dufosse to
produce sounds of some sort, and Abbot has increased the
number in this country. The swimming-bladders of Triyla
and Zeus have a diaphragm and muscles for opening and
closing it, by which a murmuring sound is made. The
Fig. 399.— Gizzard Shad.
loudest sounds are made by Pogonias cliromis, the drum-
fish. In some Cyprinince, Siluroids and eels the sound is
made by forcing the air from the swimming-bladder into the
oesophagus. In the sea-horse (Hippocampus), the sounds
are made by the vibrations of certain small voluntary
muscles.
Dr. C. C. Abbot has in this country discovered that the mud
sun-fish (A rdtifltiirehus ptniwh'*) utters a deep grunting sound;
the gizzard shad (Dorosoma cepedianum, Fig. 399) makes "an
audible whirring sound ;" the chub-sucker or mullet (Erimij-
zon oblong um) "utters a single prolonged note accompanied
by a discharge of air-bubbles ;" the cat-fish (Ainlnrny
VIVIPAROUS FISH. 441
produces "a gentle humming sound ;" eels utter a more dis-
tinctly musical sound than any other of those observed by
Abbot, who states that '''it is a single note, frequently re-
peated, and lias a slightly metallic resonance." It should
also be noticed that the organs of hearing in many musical
fishes are said to be unusually well developed, hence these
sounds are probably love-notes : and Abbot notices the fact,
that these fishes are dull-colored during the reproductive sea-
son, as well as at other times, while voiceless fishes, such as
the perch, common sun-fish, chub, roach, etc., are highly
colored daring the breeding season, and thus the sexes are
mutually attracted in the one case by music, and in the other
by bright colors. Finally the sounds of fishes may be said
to be homologous with those of reptiles, birds and mammals,
the air-bladder being homologous with, the lungs of the
higher Vertebrates, while the pneumatic duct is comparable
with the trachea of birds and mammals.
In swimming, the propelling motion is mainly exerted by
the tail, the movements of which are somewhat like those of
an oar in sculling. The spines of the tail-fin are movable,,
and are capable of being brought into such a position that
the fin will meet with less resistance from the water while the
tail is bent, they are then straightened, and it is when being
straightened that the fish is propelled. The movements of
the pectorals and ventrals are to steady the fish and to ele-
vate and depress it, while the dorsal and anal fins steady
the body and keep it upright, like a dorsal and ventral keel.
Among viviparous bony fishes are certain Cyprinodonts
(as Anableps and PceeiUit), the eel -like Zoarces, and the
blind-fish of the Mammoth Cave. A small family of Cali-
fornian marine fishes, in form resembling the sun-fish (Pomo-
tis) are called by Agassiz Embiotocidce, from the fact that
they bring forth their young alive. Embiotoca JacTcsonl
Agassiz, which is twenty-seven and a half centimetres (1O|
inches) long, has been known to produce nineteen young,
each about seven and a half centimetres (3 inches) long.
During their reproductive season, many bony fishes, such
as the stickleback, salmon, and pike, are more highly colored
than at other times, the males being especially brilliant in
442 ZOOLOGY.
their hues, while other secondary sexual characters are devel-
oped. The female deposits her eggs either in masses at the
surface of the water, as the goose-fish, or at the bottom
on gravel or sand as do most other fishes, the male passing
over them and depositing his '• milt " or spermatic particles.
The egg has a thin transparent shell, and the yolk is small,
covered with a thick layer of the " white."
The eggs after fertilization undergo partial segmentation,
the primitive streak, notochord, nervous cord, and brain de-
velop as in the chick, but that the embryo is to become a
fish is soon determined by the absence of an amnion and allan-
tois, and by the fact that the germ lies free over the yolk
like a band.
In the pike the heart begins to beat about the seventh day,
and by this time the alimentary canal is marked out. The
primitive kidneys are developed above the liver. The air-
bladder arises as an offshoot opposite the liver from the ali-
mentary canal, and the gall-bladder is also originally a
diverticulum of the intestine. The urinary bladder in the
fish is supposed to be the homologue of the allantois of the
higher Vertebrates. The principal external chan ge is the
appearance of the usually large pectoral fins.
The embryo pike hatches in about twelve days after devel-
opment begins, and swims about with the large yolk-bag
attached, and it is some seven or eight days before the young
fish takes food, living meanwhile on the yolk mass. The
perch hatches in twelve days after the egg is fertilized, and
swims about for eight or ten days before the yolk is absorbed.
The gills gradually develop with the absorption of the yolk.
The tail in most bony fishes is at first protocercal, then
becoming heterocercal as in the adult sharks, but subse-
quently, after the fish has swam about for a while and in-
creased in size, it becomes homocercal or symmetrical. The
scales are the last to be developed.
In the large size of the pectoral fins, the position of the
mouth, which is situated far back under the head, the hetero-
cercal tail, the cartilaginous skeleton and uncovered gill-
slits, the embryo salmon, pike, perch, etc., manifest transi-
tory characters which are permanent in sharks.
BREEDING HABITS OF TUE EEL. 443
The bony fishes date back to the Jurassic period, but did
not become numerous until the Cretaceous and especially the
Tertiary Period. The Green River beds of Wyoming abound
in their remains.
The Teleosts are divided into eight orders, in an ascending
series as follows : Opisthonii, Apodes, Nematognatld, Scypho-
phori, Teleocephali, Pediculati, Lophobranchii and Plectoy-
nathi.
Order 1. Opifithomi. — The fishes of this group are char-
acterized by the separation of the shoulder-girdle from the
head. The ventral fins are either abdominal or wanting.
The typical genus is Notocanthus, in which the body is elon-
gated, with a proboscis-like snout.
Order 2. Apodes. — In this group, also, the scapular arch
Fig. 400.— Common Eel, Angullla acutirostris.
is free from the skull, while the maxillary bones are rudi-
mentary. The branchial apertures are unusually small, and
there are no ventral fins, while the body is very long, cylin-
drical, snake-like. The order is represented among many
other forms by the common eel (Anyuilla}, the conger-eel,
and the Murmna of the Mediterranean Sea. The conger-eel
(Conger oceanicus Gill) ranges from Newfoundland to the
West Indies. Gill, as well as Giinther and others, regards a
long transparent ribbon-like fish, described under the name
of Leptocephalus as the young of the conger-eel.
The common eel, Angullla, acntiruxt.ris (Fig. 400), occurs
on both sides of the Atlantic, on the North American coast
as far south as Cape Hatteras, and in inland rivers and lakes.
The sexes do not differ externally, and internally only
444 ZOOLOGY.
as regards the form of the reproductive glands. The
ovaries form two ribbon-like masses extending from the
liver to just beyond the vent and attached by one edge
to the walls of the body, with the free edge hanging
downwards. When in spawn the ovary is very thick,
white, and the eggs can be seen with the naked eye,
being nearly one half millimetre in diameter. When ripe
they break through the wall of the gland and drop into
the' body-cavity, there being no oviduct, and pass out of the
genital opening situated directly behind the vent, The male
glands occupy the same position as the ovaries of the female,
but are smaller, narrower, and distinctly lobulated. Out of
about six hundred specimens of eels, only four males' have
yet been found in this country. These had testes like those
described by Syrski in the Italian eel (A. vulc/aris), while Pack-
Fig. 401.— A Siluroid Fish, Anus. Young with the yolk not absorbed.
arc! detected the mother cells, and Mr.Kingsley observed mov-
ing active spermatozoa. It is probable that the eel descends
rivers in October and November, spawning in the autumn and
early winter at the mouth of rivers, and in harbors and es-
tuaries in shallow water. By the end of the spring the
young eels are two or three inches long, and then ascend
rivers and streams. They grow about an inch a month, and
the females do not spawn at least before the second year, i. e. ,
when about twenty inches long. Mr. Mather estimates that
the ovary of an eel weighing six pounds when in spawn con-
tains upwards of 9,000,000 eggs.
Order 3. Nematoynatlii. — This group is represented in
North American waters by the catfish and horned pout.
The name of the order (from v-tj^n, vqjAaros, thread, and
SILUROID FISUE8.
445
yvados, jaw) is in allusion to the filaments or barbels grow-
ing out from the jaws, and which are characteristic of the
members of the group. The upper jaw is formed by the
intermaxillary bones only, while
the supra-maxillary bones form
the bases of the large barbels.
The suboperculum is always ab-
sent, as is also the symplectic ;
the supra-occipital and parietal
bones are co-ossified. The skin is
either naked or with bony plates.
The air-bladder connects by a
duct with the roof of the oesoph-
agus. While a few forms are
marine, most of the Siluroid
fishes are inhabitants of the riv-
ers of tropical countries, a large
number being characteristic of
the rivers of Brazil. All the
North American species belong to
the family Silvridce, of which
the common representatives are
the horned pout and western
catfish. In these forms the skin
is naked. The horned pout,
Amiurus atrarius Gill, ranges
from New England to Maryland
sules attached by slight stalkST and the Gr(?at Lakeg> jt breedg in
New England in holes in gravel during the midsummer. The
Great Lake catfish, Amiurus nigricans Lesueur, is abundant
in the Great Lakes, and is about a metre (2-4 feet) in length.
The blind catfish, Gronias nigrilabris Cope, inhabits a sub-
terranean stream tributary to Conestoga Eiver in Eastern
Pennsylvania.
Among the exotic South American Siluroids are Arius
(Fig. 401) and Aspredo (Fig. 405) of Guiana. In Arius and.
some of its allies in South America the eggs are carried by
the males in their mouth, from five to twenty being thus
44G ZOOLOGY.
borne about until the young hatch. They are probably
caught up after exclusion and fertilization. Some of these
eggs are half an inch in diameter. Dr. Day states that the
same habits occur in certain Indian species of Arius and
Osteogeniosus. A species of Arius was found by Stein-
dachner, at Panama, to carry its eggs in a fold of the skin of
its belly ; afterwards the males bear them about in their
mouth.
The females of Aspredo have on the ventral surface
horny, stalked capsules, which contain eggs from one to two
millimetres in diameter ; the capsules disappear as soon as
the young hatch.
Malapterurus elect ricus Lacepede, of the Nile, is electri-
cal, the electric cells forming a layer directly beneath the
skin and enveloping the whole body, except the head and
fins. The cells are minute, lozenge-shaped, about one and
a half millimetres in diameter. They are supplied by a
nerve from the spinal cord. The shock is comparatively
feeble, but suffices for defence, '•' the fish being protected by
its electrifying coat, as is the hedgehog by its spines."
(Owen.)
Order 4. Scyphophori. — This order, first named and
characterized by Cope, derives its appellation from the
Greek ffnixpo?, a bowl, and (pepco, to bear, in allu-
sion to a peculiarity of the pterygoid bone, which is en-
larged, funnel-shaped, and excavated by a bowl-like cham-
ber which expands laterally and is covered by a lid-like bone.
The brain has a peculiar plicated organ over the cerebellum ;
the air-bladder is simple, communicating by a duct with the
intestinal canal. The order comprises two families, the
members of which inhabit the rivers of Africa ; they are the
MormyridcB, represented by a number of genera and species,
and the Gymnarcliidce, of which Gymnarchus niloticus is
the only known species.
Order 5. TeleocephaU. — These are our common types of
fishes, and are, whether we consider their individual struc-
ture or the number of specific forms, the most highly de-
veloped, i. e., specialized, of the class. The name is derived
from rf'A^os, perfect, and H£(pa\i}, head, in allusion to the
HABITS OF THE HERRING AND SHAD. 447
high degree of elaboration and diversity in the bones of the
head. The skeleton is usually completely ossified. The
bones of the skull and of the jaws are fully developed. The
lower jaw is attached to the skull by a suspensorium of sev-
eral well-marked bones, including a symplectic, while the
hyoid and gill arches are well developed, as is the scapular
arch. The brain has small olfactory lobes and a small cere-
bellum. The scales are generally present, and either cte-
noid (i.e., rough-edged) or cycloid (i.e., rounded but smooth
on the edge). The common examples are the carp, herring,
trout and salmon, pike, perch, cod, and flounder.
Turning now to some of the more characteristic members
of the order, we first notice one of the lowest Teleosts, the
electrical eel (Gymnotus elect ricus Linn.) of South Amer-
ica, which is two metres in length, and is characterized by
its greatly developed electrical batteries. These are four in
number, situated two 011 each side of the body, and together
form nearly the whole lower half of the trunk. The plates
of the cells are vertical instead of horizontal, as in the tor-
pedo, while the entire batteries or cells are horizontal, in-
stead of vertical, as in the electrical ray. The nerves sent
to the batteries of the eel are supplied by the ventral
branches of about two hundred pairs of spinal nerves.
Succeeding these and allied forms are the herrings (Clu-
peidce], represented by the common English herring, Clupea
harengus Linn., which inhabits both sides of the North
Atlantic, extending on the American side from the polar
regions to Cape Cod; the alewife, Pomolobus pseudoharengus
Gill, which ranges from Newfoundland to Florida ; the shad,
Alosa sapidissima Storer, which has the same geographical
distribution as the alewife ; and the menhaden or pogy,
Brevoortia tyrannus Goode, which extends from the coast
of Maine to Cape Hatteras. These, with the cod, hake,
haddock, salmon, and a few other species, comprise our
most valuable marine food-fishes. The fisheries of the
United States yield about $40,000,000 annually, whilst those
of Great Britain amount to about $40,000,000, and those of
Norway about $10,000,000.
The herring is a deep-water fish which visits the coast in
448 ZOOLOGY.
spring in immense schools, in which the females are three
times as numerous as the males, to spawn, selecting shoal
Avater from three to four fathoms deep in bays, win re the
eggs hatch. At this season, and early in the summer, hun-
dreds of millions are caught, especially on the Canadian,
I Newfoundland, and Labrador coasts. The English white-
bait is the young of the herring. The herring is caught in
deep nets with meshes large enough to capture individuals
, of ordinary size, the nets having a finer mesh than those
used for the mackerel fishery.
The aleAvife and shad are said to be anadromous, from
their habit early in spring of visiting the coast and ascend-
ing rivers in vast numbers to spawn. The eggs are of mod-
erate size ; the ovaries are said to contain about 25,000, and
Fig. 403.— The Herring, Clupea harengus, one third natural size.— From the Ameri-
can Naturalist.
at times as many as 100,000 or 150,000 eggs. They are dis-
charged near the surface, sinking sloAvly to the bottom.
The time between impregnation and hatching varies from
about three to six days, according to the temperature. The
shad eats little or nothing in fresh water, being then engaged
in the act of reproduction. In the sea they liAre on small
Crustaceans, such as My sis, etc. The menhaden is HOAV put
up as a substitute for sardines, and is of great value as fish-
bait, especially in the mackerel fishery, and for its oil.
The family Salmonidce comprises the salmon, trout, and
whitefish, with a number of species and varieties. The
species of the genus tfalnm have not more than eleven rays
to the anal fin, while the salmon of the Avest coast, quinnat,
THE SALMONID^E. 449
has fifteen or sixteen anal rays. The tialmo salar Linn,
sometimes weighs eighty pounds. It is common to Europe
as well as Northeastern America. In the autumn the salmon
ascends rivers to spawn, penetrating as near the source as
possible. During the breeding season the males differ de-
cidedly from the females, in the long, slender, hooked snout,
the body being thin and high-colored. The eggs are very
large, exceeding a pea in size, and are laid in shallow holes
made in the gravel of streams. The extreme young are
banded and called parr ; when about a year old, and of a
bright silvery color, before descending the rivers to the sea,
it is called a smolt ; after its return from the sea into fresh
water it goes by the name of grilse; and finally, after re-
turning a second time from the sea, it assumes its name of
salmon. The trout, Sal/no (Salvelinus) fontinalis Gill and
Fig. 404.— The Smelt— Osmerus mordax — one half natural size.— From the Amer-
ican Naturalist.
Jordan, also breeds in the autumn and early winter ; it is
not anadromous, living permanently in streams and ponds.
An allied family embraces the smelts, Osmerus eper-
lanus Linn., and 0. mordax Mitchill, which live on both
sides of the Atlantic, and range from Nova Scotia to Vir-
ginia, The capelin, Mallotus villosus Cuvier, is valuable
as bait in the cod fishery. It spawns in the summer. The
males are distinguished by a prominent lateral ridge along
the sides of the body and are more numerous than the
females.
Belonging to the same suborder or group of families
as the Salmonidce is the family GalaxiidcB, represented by
Galaxias and Neoclianna (Fig. 413), in the latter of which
the ventral fins are absent.
450
ZOOLOGY.
The carps (Cyprinus), shiners and minnows abound every-
where in the Northern States in ponds and weedy streams. The
breeding habits of the dace (Rhinichthys atronasus Mitchill)
have been observed by Dr. Gregg. The females spawn over
'•'nests" or shallow depressions two feet in diameter in run-
ning brooks about a foot deep ; the male passes over the
eggs fertilizing them ; then the pair bring small pebbles
which are dropped over the eggs, until layer after layer alter-
Fig. 405.— Neochanna.— From Liitken.
nately of eggs and pebbles are deposited, when a heap is
formed, the young hatching out and remaining among the
pebbles until old enough to venture out into the stream.
The dace is closely allied to the chub (Semotilus rliotlieus
Cope, Fig. 407). Succeeding them are the suckers (family
GatostomidcB) of which Oatostomus teres Lesueur is an ex-
ample.
The blind fish of the Mammoth and other caves, and of
Fig. 406.— Mud-Minnow.— From Abbot.
adjoining wells connecting with subterranean streams, are
remarkable for the rudimentary state of the eyes, and con-
sequently of color. There are but two species, the more
common and larger being Amblyopsis spelceus De Kay; this
species is viviparous. Representing the family Unibridte is
the mud-minnow (Melanura limi Kirt., Fig. 406).
The flying-fish represent another family. Their pectoral
fins are very broad and large. They dart from the water
FLYING-FISH.
451
with great speed without reference to the course of the wind
and waves. They make no regular flying motions with their
pectoral and ventral fins, but spread them out quietly,
though very rapid vibrations can be seen in the outstretched
pectoral fins. They usually fly farther against the wind than
with it, or if their track and the direction of the wind form
an angle. Most flying-fish which fly against or with the
wind continue in their whole course of flight in the same di-
rection in which they come out of the water. Winds which
blow from one side on to the original track of the fish bend
their course inward. All fish which are at a distance from
the vessel hover in their whole course in the air near the sur-
face of the water. If in strong winds they fly against the
Fig. 40:.— The Large Chub, Semotilua rhotheus, one fifth natural size.— From Abbot.
course of the waves, then they fly a little higher ; sometimes
they cut with the tail into the crest of the waves. Only
such flying-fish rise to a considerable height (at the highest,
by chance, five metres above the surface of the sea) whose
course in the air becomes obstructed by a vessel. In the
daytime flying-fish seldom fall on the deck of the ship, but
mostly in the night ; never in a calm (Moebius). Whitman
claims that they truly My and can change their course in
mid-air. We have seen one rise and fall during flight.
Following the flying-fish is the family represented by the
silver gar or bill-fish (Belonv longirostrus Mitchill, Fig. 408).
The sucker (Echeneis remora Linn.) occurs along the
whole coast of the United States, and is found all over the
452
ZOOLOGY.
tropical and subtropical seas. It is provided with a broad
oval sucker on the upper side of the head, by which it ad-
heres to other fish or even to ships, and may thus be trans-
ported long distances. Another noticeable member of the
order is the blue-fish (Pomatomus saltatrix Linn., Fig. 409),
so valuable as a food-fish.
Fig. 408.— The Bill-fish, Belone longirostrus.—FTom the American Naturalist.
The dolphin (CorypJicena] is sometimes found upon our
coast, but it is essentially a pelagic fish, occurring only out
of sight of land upon the high seas. The pilot-fish is also
a pelagic form.
The percoid fishes are represented by the perch (Perca flu-
viatilis Linn.), which spawns in winter, making slight hol-
lows in the gravel in shoal places in ponds ; their movements
Fig. 409. —The Blue-fish, Pomatom.us mltatrisn, one sixth natural size. — From the
American Naturalist.
can be watched through the ice. On the other hand, the
sun-fish or bream (Eupomofis cnireus (1. and J.) spawns in
the summer time, making a nest, which it scoops out of
the river bottom. The banded sun-fish (Mesogonistius clim-
todon Gill) occasionally scoops out a little basin in the sand,
in which it deposits its eggs late in the spring. The spotted
HABITS OF THE MUD-MINNOW, ETC.
453
sun-fish (Enncacanthus obesus Gill, Fig. 410) lives in muddy
streams, burying itself in the mud in winter. Of similar
mud-loving habits is the mud-minnow (Melanura Hint
Agassiz), which spawns in the spring. The pirate perch
(Apliredoderus sayanus De Kay) occupies the nest of com*
Fig. 410.— The Spotted Sun-fish, Enneneanthus obesus.— After Abbot.
mon sun-fish, and with the female guards it and afterwards
the young till they are nearly a centimetre (two-fifths inch)
in length, when they are left by their parents. (Abbot. )
The darters, Etlteoxtonuda>, belong near the perches, and
comprise the smallest of fishes. They inhabit the streams
of the Mississippi Valley. A common example is the sand-
darter (Pleurolepis pellucidus Agassiz, Fig. 411).
Fig. 411.— Sand-Darter.— After Jordan.
The male stickleback (Gust croxt ens) makes an elaborate
nest of leaves, etc., suspended in mid-water, within which it
remains watching the eggs and young.
One of the most valuable food -fishes is the mackerel
(Scomber scombrus Linn., Fig. 41:3), whose range is from
454 ZOOLOGY.
Greenland to Cape Hatteras. It remains in deep water dur-
ing the late autumn and winter, approaching the coast in
May and June for the purpose of spawning, its annual
appearance being very regular. The number of eggs de-
posited in one season by each female is said to be from five
to six hundred thousand. After spawning they move north-
ward, following the coast until they are checked by the
coolness of the water, when they return, and in November
seek the deep water again. When spawning they do not
take the hook ; they are then lean ; but at the time of their
departure from the coast they are fat and plump. (Blake.)
The eggs of the mackerel as well as of the cod are so light
as to rise to the surface, where they develop. Allied to the
mackerel, though of great size, are the horse-mackerel and
the sword-fish, whose upper jaw is greatly prolonged.
Fig. 412.— The Mackerel, Scomber scombrux, one quarter natural size —After Blake.
The singular Anabas of the East Indies is the representa-
tive of a small group of fishes called Labyrinthici or laby-
rinth-fishes, in allusion to a cavity on the upper side of the
branchial cavity on the first gill-arches, containing a laby-
rinthine organ, which consists of thin plates, developed
from the upper pharyngeal bones, enabling the fish to live
for a long time out of water. Anabas scandens Cuvier, of
the fresh waters of India, will travel over dry land from one
pond to another, and is even said to climb trees by means
<>!' the spines in its fins.
Near the head of the order stands the dinner (T<inh><i»l<t-
brus adspersns Gill), whose anatomy is represented_by Figs.
:'.!ii;-398. Passing over the tautog, the voracious wolf-h'sh
{Anarrliirlttt*}, the blennies (lilcmiithp}, in which the body
HABITS OF THE CODFISH AND HADDOCK. 4;.:.
is long and narrow, and the viviparous eel-pout (Zoarces), the
cottoids or sculpins, and a number of allied forms, we come
to the hake (JferlHciH* hiliiu'ttris Gill), the haddock (Melano-
ijnutunus (eylcF')iiix Gill, Fig. 413), and cod (Gadus morrliua
Fig. 413.— The Haddock, Melanogrammus ceglefinus.—U'rom the American Xut-
urahst.
Linn., Fig. 414), all of which extend northwards from Cape
Hatteras, the cod abounding on both sides of the Atlantic,
being a circumpolar fish. The cod does not, as formerly
supposed, migrate along the coast, but seeks the cool tempe-
rature to which it is adapted by gradually passing in the
Fig. 414.— The Cod-fish, Gadus morrhua.— From the American Naturalist.
early summer from shallow to deep water, and returning as
the season grows colder. It visits the shallow water of Mas-
sachusetts Bay to spawn about the first of November, and
towards the last of the month deposits its eggs. About
456 ZOOLOGY.
eight or nine million of eggs are annually deposited by each
female. (Blake.) The eggs laid by the cod rise to the sur-
face of the water, on which they float, The young fish
hatch on the New England coast in twenty days after they
are extruded. Several millions of cod were artificially hatched
at Gloucester, Mass., in the winter of 1878-9, by the United
States Fish Commission ; it has thus been demonstrated
that this fish can be artificially propagated.
The cod is the most important of all the food-fishes,
whether we consider the number taken and the amount of
capital involved in the cod-fishery. It abounds most on
tlir (I rand Banks of Newfoundland. The breeding habits
of the haddock, hake and pollock are probably like those of
the cod.
Fierasfer is a small eel-like fish, with a long, thin tail. It
is typical of a peculiar family, and is noteworthy from being
a " commensal" or boarder in the digestive canal of Holo-
thurians, etc. F. acus Briinn. lives in Holuthurians, and
another species in a star-fish (Culcita}. The Brotulidcs are
fishes allied to the cod, but constituting a distinct family.
Most of them are salt-water species, but allied forms (Lnci-
fuga suMerraneus and Stygicola dentata} live in subterra-
nean waters in Cuba.
At the head of Teleocepltali stand the flounders, halibut
and soles, which are an extremely modified type of the order.
In these fishes the body is very unsymmetrical, the fish vir-
tually swimming on one side, the eyes being on the upper
side of the head. The upper side is colored dark, due as in
other fishes to pigment-cells ; the lower side is colorless, the
pigment-cells being undeveloped. When first hatched the
body of the flounder is symmetrical, and in form is some-
what cylindrical, like the young of other fishes, swimming
vertically as they do, and with pigment-cells on the under-
side of the body. Steenstrup first showed by a series of
museum specimens that the flounder was not born with the
eyes on the same side of the head, but that one eye gradually
passed from the blind to the colored side. Mr. A. Agassiz
has studied the process, and finds that the transfer of the eye
from the blind side to the colored side occurs very early in
HABF1S OF THE FLOUNDER, ETC.
457
life, while all the facial bones of the skull are sdll cartilagl
nous, long before they become hard and ossified, i.e., when
the flounder (Plagusia) is twenty-five millimetres (one inch)
Ion"-. "The transfer of the eve from the right side to the
O v O
left takes place by means of a movement of translation, ac-
companied and supplemented by a movement of rotation
over the frontal bone." Young flounders, when less than
two inches in length, are remarkably active compared with
the adults, darting rapidly through the water after their
food, which consists principally of larval, surface-swimming
crustaceans, etc. (A. Agassiz. ) The common flounder from
Nova Scotia to Cape Hatteras is Pseudopleuronectes Ameri-
canus of Giil.
Fig. 415.— Goose-fish, one tenth natural size.— From Tenney's Zoology.
Order 6. Pediculati. — The type of this order is the goose-
fish. The name was given to the group from the long
slender bones supporting the pectoral fins. The gill-open-
ings are small and placed in axils of the pectoral fins. L<>-
pliius piscatorius Linn., the goose-fish or angler (Fig. 415),
has an enormous mouth, and swallows fishes nearly as large
as itself. The head and fore-part of the body is very large;
the skin is naked, scaleless. Its eggs are laid in broad,
ribbon-like, thin gelatinous masses, two metres long and
half a metre wide, which float on the surface of the
ocean.
Order 7. Lophobranchii. —The tufted-gilled fish — such the
name of the order indicates — have a fibre-cartilaginous skele-
458
ZOOLOGY.
ton ; a single opercnlar bone, while the snout and lower
jaw are prolonged into a tube, with the mouth at the
end. The chief peculiarity, however, is the gills, which are
developed in the form of a row of tufted lobes on each side
of the branchial arches. The scales are large, forming an-
gular plates arranged in longitudinal rows (Gill). In ,Wr-
nostoma of the Indian Ocean the female carries the eggs in
a pouch formed by the union of the ventral fins with the
integument of the breast.
The male of the pipe-fish (Syngnathus ]><'rki<oins Storer)
receives from the female the eggs, and carries them in a
small pouch under
his tail, which is
open beneath
through its whole
length. This sin-
gular mode of mas-
culine gestation is
still farther per-
fected in the sea-
horse (Hippocam-
pus hudsonius De
Kay, Fig. 416),
which lives off-
shore from Cape
Cod to Cape Hat-
teras). The pouch
is situated on the
breast. The male, by simple mechanical pressure of its
tail, or by rubbing against some fixed object, as a shell,
forces the fry, to the number of about a thousand, out of its
brood-pouch, the young at this time measuring about twelve
millimetres (5-6 lines) in length. In the young the head is
at first rounded, the snout being short and blunt (Lockwood).
Order 8. Plectoynathi. — This group, represented by a few
singular forms, such as the trunk-fish, file-fish, puffers, and
sun-fish, is characterized by the union of the bones of the
upper and especially the lower jaws. There are few verte-
bra?, the scales are often modified to form spines, and the
Fig. 416.— Sea-horse, male, with the young issuing
from the brood-pouch.— After Lockwood.
THE SUN- FISH.
459
ventral fins are usually absent. They are inhabitants of warm
waters. The trunk- fisli or box-fish, Lactiythrijx triyonus
Poey, is a West Indian fish ; one specimen has appeared at
Holmes' Hole, Mass. The porcupine -fish (ChiHchthys
turgidus Gill) and smooth puffer (Tetrodon Icevigatus Gill)
and the spring box-fish (Chilomycterus geometricus Kaup)
Fig. 417.— Sun-fish, Mola rotunda, one eighteenth natural size.— After Putnam,
range from Cape Cod to Florida. The sun-fish (Mola ro-
tunda Cuvier, Fig. 417) is, like the others of the order, a
surface - swimmer. It is sometimes a metre or more iu
length, weighing five hundred pounds or more. Allied
forms are Orthayoriscus oblongus (Fig. 418) and the globe-
4GO
ZOOLOGY.
fish, Molacantlms Pallasii (Fig. 419), which occur in the
North Atlantic.
Fig. 418.— Orthagoriscus oblongus, young, natural
size.— After Harting.
Pig. 419.— Mole*
canthus Pallaxii,
half grown, natural
size. — After Put-
nam.
CLASS IV.— PISCES.
Aquatic Vertebrates with a movable lower jaw, a cartilaginous or
osseous skeleton, with paired and unpaired fins supported by fin rays ;
no sternum; usually covered with scales; breathing by gills. Heart
with a single ventricle and auricle. Mostly oviparous.
Subclass I. Elasmobranchii. — Skeleton cartilaginous ; skull without
membrane bones, five to seven pairs of gill-sacs and gill-
openings ; no opercular bones ; tail heterocercal ; scales
placoid ; heart with a pulsating aortic bulb ; optic nerves
forming a chiasma ; intestine with a spiral valve ; both
oviparous and viviparous.
Order 1. Plagiostomi (Selache, Lamna, Raja).
Order 2. Holocephali (Chiniaera).
Subclass II. Ganoidei. — Skeleton cartilaginous or ossified ; skull with
plate-like membrane bones ; one pair of gill-openings cov-
ered by opercular bones ; skin usually with cycloid or gan-
oid scales ; air-bladder with a pneumatic duct ; embryos or
young sometimes with external gills ; chiasma of the optic
nerves ; intestine with a spiral valve ; development, so far
as known, much as in the sharks, and in some respects like
the bony fishes ; the living forms oviparous.
Order 1. Chondroganoidei (Acipenser).
CLASSIFICATION OF FISHES. 461
Order 2. Brancliioganoidei (Polypterus).
Order 3. Hyoganoidei (Lepidosteus, Amia).
Subclass III. Teleostei.— Skeleton bony ; skull composed of numerous
bones ; optic nerves crossing each other ; usually four pairs
of gills, with several opercular bones ; heart without a cone,
but with an arterial bulb ; intestine generally without a
spiral valve ; mostly oviparous.
Order 1. Opisthomi (Notacanthus).
Order 2. Apodes (Anguilla).
Order 3. Nematognathi (Amiurus).
Order 4. Scyphophori (Mormyrus).
Order 5. Teleocephali (Salmo, Perca, Gadus).
Order 6. Pediculati (Lophius).
Order 7. LophobrancJiii (Hippocampus).
Order 8. PlectognatM (Tetrodon, Mola).
Laboratory Work. — Fishes should usually be dissected, except when
large, under the water; small specimens can be pinned down to the
bottom of cork- or wax-lined dissecting pans, and the more delicate
parts worked out with fine scissors and knives. The brain and spinal
cord can be dissected with ease, provided care be taken, with scalpel
and scissors, as the bones covering them can be cut away by means of
stout scissors and bone-pliers and fine surgical saws. Longitudinal
sections will bring out the relations of the brain and beginnings of the
nerves, and transverse sections of the tail may be made to show the
disposition of the muscles. The skeleton may be prepared whole by
removing the flesh carefully from alcoholic or partly macerated speci-
mens. Disarticulated skeletons for study can be made by parboiling
the fish and then separating the bones from the flesh. To study the
circulation, careful injections should be made by the use of an inject-
ing syringe, with wax, plaster of Paris, or vermilion as the injecting
medium.
CLASS V. — DIPNOI (Lung-fi*lt).
General Characters of Dipnoans.* — The lung-fishes are
so called from the fact that, often being in pools and streams
lial'le to dry up, they breathe air directly, having true lungs,
like those of Amphibians, as well as gills. From the nature
* Hyrtl, Lepidosiren paracloxa. Prag, 1845.
462 ZOOLOGY.
of their lungs and heart, the Dipnoans are quite different
from all other fishes, anticipating in nature the coming of
Amphibians, while on the other hand the notochonl and
sheath is persistent, and as they were characteristic and
more numerous in Devonian times, they may be said to he a.
prematurative type.
The body of the Dipnoans is somewhat eel-shaped, though
not very long in proportion to its thickness, and is covered
with cycloid scales. The pectoral and ventral fins are long,
narrow, and pointed, and there is a long caudal fin which is
/trotocercal, a term proposed by Wyman to designate the form
of the caudal fin of embryo sharks. In fact, the tail of the
young garpike, as of embryo Teleosts or bony fishes, is at
first protocercal, afterwards being heterocercal in adult
Ganoids, such as the garpike, and in the embryo and
early free stage of most bony fishes ; the tail in the latter
becoming finally homocercal or equal-lobed. Thus the
tail of the Dipnoans may be said to be embryonic, i.e.,
protocercal.
The spinal column is represented by a simple notochord and
sheath ; within the latter the basal ends of the bony neural
arches and ribs, and near the tail the lower (haemal) arches
are imbedded. The skull is cartilaginous. The extremity of
the lower jaws supports large tooth-like plates (dentary plates)
which shut in between the few palatine teeth ; in Cerutodnx
these plates are single, and in all Dipnoans these single den-
tary plates are very characteristic of the group. The narrow
pectoral and ventral fins are supported by a single, median,
many-jointed cartilaginous rod, to which are attached fine-
fin-rays, supporting the thin edge of the fin.
The spiral valve is present in the intestinal tract, ending
rather far from the cloaca, into which the oviducts and ure-
ters both open. There is a muscular conus arteriosus, and
the heart has, besides the right large auricle, a left smaller
one which receives the blood from the luno-s, and a single
O o
ventricle, as in Amphibians and most reptiles; they have
true nostrils. The lungs are like those of Amphibians, and
in addition they possess both internal and external gills, the
latter nearly or wholly aborted in the adult.
L UNO-FISHES. 463
The genus Ceratodus was originally named by Agassiz,
from teeth found in Jurassic and Triassic strata in Europe.
Living specimens were found by Mr. Krefft in Queensland,
Australia, and called Ceratodus Foster i Krefft (Fig. 420).
This fish is rather more elementary in form than Lepidosiren,
the body being stouter, and the large scales of the body,
witli the fin-like paddles and distinctly rayed vertical fins,
cause it to resemble more closely ordinary bony fishes than
Lepidosiren (Giinther). Moreover, the lung is single, and
Fig. 420.— Ceratodus, or Australian Lung-fish. (The tail in nature ends in a
point.)— After Gtinther; from Nicholson.
not used so much as the two perfect lungs of Lepidosiren.
It attains a length of six feet. It can breathe by either gills
or lungs alone. When, Guuther thinks, the fish is com-
pelled to live during droughts in thick muddy water charged
with gases which are the product of decomposing organic
Fig 4?l.—Protopterus annectena, a lung-fish of Africa. (One-third natural size.)
matter, it is obliged to use its lungs. The gills are more
like those of ordinary bony fishes than those of Lepidosiren.
It lives on the dead leaves of aquatic grasses, etc. The
local English name is " flat-head," the native name being
"barramundi." Little is known of its breeding habits or
mode of development. The eggs when ready to be laid arc
2.5 millimetres in diameter. The lower part of the oviduct
is much as in Menopoma. Fossil teeth of Ceratodus occur
464
ZOOLOG T.
in the Jurassic beds of Wyoming, and two species have been
found in still older beds in Illinois, regarded by Cope as
either Upper Carboniferous or Permian. Thus, as remarked
by Gfmther, we have in CiTitfudus a genus which has sur-
vived from the Triassic period.*
Tho lung-fish are distinguished by two well-formed lungs,
and the narrow ribbon-like fins. In Lepidosiren paradoxa
Fitzinger, there are five gill-arches, with four slits, and the
body is rather longer, more eel-like, with a blunter snout
than in Protopterus.
It grows to one metre in length, and
m -in
in ni
rrTTTrrrrrTfrrrrnrrrrn
Fi<r. 423. — Skeleton of Protnpterus annecfens, showing the protocercal tail and the
simple rod-like limbs, the pelvic and shoulder girdles, and the nature of the jaws.
ch. notochord ; p, hones representing the luemal arche* attached to the notochordal
sheath ; /«, haemal spines ; in, ih. rays of the caudal fin.— After Owen.
inhabits the rivers of Brazil. This is represented in Africa
by the closely allied Protopterus annectens Owen (Figs. 421
and 422 skeleton), which has six gill-arches, with three
pairs of external gills in the young. It is 40-70 centimetres
in length. It lives on leaves in the White Nile, Q.uilimani,
Niger, Gambia, and their tributaries. It buries itself in the
mud a foot deep.
CLASS VI. — BATKACHIA (Salamanders, Toads, and Froys).
General Characters of Batrachians. — We have had an-
ticipations of the Batrachians or Amphibia in the Ganoids,
especially the Dipnoan fishes, which it will be remembered
approach the members of the present clas-s in the lung-like
nature of the air-bladder and in the presence of external
* Description of Ceratodus, Phil. Trans. Roy. Soc., London, 1871.
Avrr's Ik-itriige zur Anatomic u. Phys. der Dipuofir. Jeua, 1885.
ANATOMY OF BATRACIIIANS. 465
gills in the young, as well as in the form of the skull, there
being many bony parts in the skull which resemble similar
parts in Batrachia. Indeed so close in some characters is the
approximation of the fishes to the Batrachians, that the two
classes have been placed in a series called Ichtliyopsida. The
Batrachians, however, differ essentially from the fishes in hav-
ing the bones of the skull few, directly comparable with
those of reptiles, birds, and mammals, and in being jointed
to the vertebral column by two articular surfaces called con-
(h/les, the first vertebra, or atlas, having two corresponding
articulating hollows. The limbs have the same number of
subdivisions, with disti" t leverage systems, as the higher
Vertebrates, the bones composing them being closely homol-
ogous. True ribs now appear. Some have persistent exter-
nal gills, and all have well-developed lungs. So that for the
first time we have the coexistence of true limbs and lungs
in animals which are air-breathing and move about freely on
land, though from passing a part of their adult life in or
about fresh water they are said to be amphibious. The skin
is usually scaleless. The circulation is incompletely double,
there being sometimes two auricles. Like fishes, they are
cold-blooded. They are mostly oviparous, a few are vivipa-
rous, and nearly all undergo a metamorphosis.
To enter more into detail : The vertebras of Batrachians
are in the living Proteus and allies, and in the blind-worms
(Apodci) biconcave ; in the salamanders and in the Surinam
toad (Pipa) and Bombinator they are concave behind, but
in the toads and frogs generally they are for the most part
concave in front, but vary in different parts of the' spinal
column, some of the same individuals being biconvex and
others biconcave. While the vertebrae are numerous in the
tailed forms, in the tailless toads and frogs there are but
eleven, two in the coccyx, one in the sacrum, the remaining
eight forming the rest of the column. In the frog, when
the tail disappears, a long, spine-like piece (Fig. 428, e) called
the urostyle is developed from the rudiments of a few verte-
bras. In the extinct Archegosaur'us the bodies of the verte-
bras are but little ossified ; in Trimerorliachis they are rep-
resented by the bony rings of three segments, while in allied
466
ZOOLOGY.
Labyrinthodonts such as Rhiachitomus, the vertebra are
ossified, but the centra consist of three pieces. In Cricotii*
there are two kinds of bodies, ci'iitra and i/tfrrccii />•//. Tlie
ribs are rudimentary, except in the blind-worms (>',,;•!! ia}.
The skull is usually broad and flattened : it differs from
that of fisbesir. having no bones representing the opeiculum,
subopereulum, interoperculum, or branchiostegal bones ; but
a membrane bone probably homologous with the preopercu-
Inm is said to exist. The maxillary are usually and the prc-
maxillary bones always present, usually armed with teeth : no
Batrachian possesses a complete basioccipital, snpraocci-
pital, basisphenoid, ali-
sphenoid, or presphe-
noid cartilage bone;
while "the frog's skull
is characterized by the
development of a very
singular cartilage bone,
called by Cuvier the ' os-
en ceinture,' or girdle-
bone.'' (Iluxle}'.)
The embryonic carti-
lage persists in the low-
er jaw in adidt Batra-
chians as in fishes, and
Fig. 428— Skeleton of a Frog. «, skuii ; b, bony parts are developed
vertebrae ; c, sacrum, and e, its continuation , •> • . ...
(iirostyle);/, Huprascapala; y, humerns; A, fore- m connection AVltll it
ami bones'; i, wrist bones (carpals and meta- _ . . . ..
carpals) ; d, ilium ; m, thigh (femur) ; „, ]eg which essentially COl're-
bone (ulna) : o, elongated first pair of ankle- , , , ',, fi ,
boiu-s (taisals) ; p, q, foot bones or phalanges. Spoiltl tO tllOSe OI HSlieS.
(Gegenbaur.)
The suspensorium is immovably joined to the skull, and
with it is connected the hyoidean arch. The branchial
arches in the tailed forms persist in varying numbers, /. e.,
from two to four, but are dropped in the toads and frogs. The
skulls of certain Labyrinthodonts are roofed in by hroad.
flat bones, so that they bear a strong resemblance to certain
Ganoids represented by the garpike, while Gegenbaur states
that there are many bony parts in the skull of the Batra-
chians which resemble those in the Dipnoan fishes. The ex-
ANATOMY OF BATRACHIANS. 4G7
tinct Arcliegosaurus had in its larval life branchial arches,
and in fact so close are the affinities of some Amphibians to
the Ganoids that it is probable that both types have had a com-
mon origin ; while on the other hand the bones of certain
extinct scaly Labyrinthodonts have been regarded by some
.authors as reptilian ; for example, the Carboniferous Mas-
todonsaurus was described as a reptile, but has been referred
to the Amphibians by modern writers.
The sternum or breast-bone (Fig. 429, s) first appears in
the Batrachians. The shoulder-girdle is in great part carti-
laginous. In the toads and
frogs (Amir a} the fore limbs,
the radius, and ulna, and in
the hind limbs the tibia and
fibula, grow together ; there
are four toes in the fore feet,
and five toes in the hind feet.
In the Siren the hind legs are Fig. 429.-sternum and
\\-mfiiio- • in +ViP pnno-n smlcp<s of Frog ^'ma temporaria). p, body t>f
« anting , 111 Hie > the sternum ; w, scapula ; w', siipra-srap-
flip limlis -iff ula , co, coracoid-bone, fused in the mid-
. dle line with it fe)low 0| • the
.piflipr two rtr fhrpp-tnpil side (s); <•/, clavicle ; «, epiaternum. The
extreme shaded double portion below jt
The teeth of modern Ba- is the xiphietemum. The cartilaginous
parts are shaded.— After Gegeiibaur.
trachians are conical or lobate,
and microscopically are simple, while those of the extinct
forms are mostly complicated by the labyrinthine infolding
of the walls, as seen in microscopic sections ; the teeth of
many Ganoids have a similar, though much simpler struc-
ture. They are usually of the same size, and may be ar-
ranged on projecting portions of different bones of the mouth,
i.e., the premaxillary, maxillary, mandibular, vomerine, pal-
atine, and pterygoid bones, as in fishes. In tadpoles and
in Siren the jaw-bones are encased in horny beaks like those
-of turtles and birds. In many Labyrinthodonts two tusks
were developed on the palate. The nasal canal is much as
ill the Dipnoan fish, the internal opening being situated in
the Perennilminchiates just within the soft margin of the
mouth. In the salamanders and frogs it is bordered with
firmer parts of the jaw. The labyrinth of the ear is large,
and the tympanum or drum of the ear is external, Am-
408
ZOOLOGY.
phibians having a middle ear in addition to the internal ear
of fishes. In toads and frogs the tongue is quite free and
capable of being protruded, except in Pipa and Dactyle-
tlira, where it is entirely wanting. In other forms the
tongue is much as in fishes, not being capable of extension
from the mouth. As in
fishes, there are no salivary
glands. The gills of Am-
phibians consist of two or
three pairs of branched,
fleshy appendages, Avhich
grow out from as many
arches. While in the toad
and frog the gills are small
and remain but for a short
time, in the larval salaman-
ders, especially the axolotl
(Fig. 430), the gills are still
longer retained, while in
the mud-puppy (AVv7///v^)
they persist throughout life.
The digestive canal is us-
ually simple, there being no
special enlargement form-
ing a stomach ; in other
species, both tailless and
tailed, the canal dilates into
a stomach, which in the
toad lies across the body-
_ ier. 430.— Axolotl. or larval Salamander,
sho
ami
from which the vascular arches (5) origi- matter, the digestive tract
nate ; bb, branchial vein ; the lower A, vena
cava ; I', descending aorta.— From Gervais Jg yei'Y long and closely COll-
et Van Beueden. ._J.
ed (Fig. 431).
The lungs are long, slender sacs, much like those of the
Dipnoan Lepidosiren, which extend backwards into the ab-
domen, as in the lizards and snakes, no diaphragm existing
to confine them in a thoracic cavity. The larynx exists in
a very rudimentary state, though the vocal powers of the
ANATOMY OF BATRA CHI AN S.
toads and frogs are so highly developed. The trachea is
short.
The heart has two auricles, the right one the larger, and a
single ventricle ; but in Proteus the auricles connect Avith
each other, and in the salamanders there is a hole in the par-
tition separating the auricles. There are also indications of
Fig. 431.— Mouth and digestive
canal of a Tadpole. A, mouth ; 6,
intestine coiled on itself ; c, liver ;
d, hepatic duct ; f, pancreas ; /,
rudimentary hind legs ; g, rectum.
— After Gervais and Van Beneden.
a partition in the ventricle. Fig.
432 represents the circulatory or-
gans of a tadpole, after the gills
have become absorbed, and before
the aortic arches are reduced in
number.
rr,, . ,
Hie nerVOUS System IS much
as in fishes; but the optic lobes
are rather small; the cerebrum is small.* The kidneys are
in many respects like those of fishes, especially sharks, as
is the internal reproductive system. The ovaries are greatly
enlarged during the breeding season. The sperm is usually
passed to the kidney, and thence through the ureters out of
the cloaca. The oviducts and ureters have a common outlet
* See Wyman, 011 the Nervous System of Raua pipiens. Smiths.
Contr. 1853.
V«K
tncle ; 6' arterial bulb ; 7, branchial
artery and its internal branches; 8,
branchial veins; 9, aorta; 10, pul-
monary artery and its subdivisions
in the lungs.— After Gervais and Van
470 ZOOLOGY.
into the cloaca. In the salamanders the end of the oviduct
serves as a uterus. There are also fat-bodies (Fig. 433) at-
tached to the anterior end of the reproductive glands of the
toads and frogs, the use of which is unknown. For a gene-
ral idea of the structure of Amphibians the student should
dissect a frog or toad iu connection with the following de-
scription and accompanying illustration (Fig. 433), prepared
by Dr. C. S. Minot.*
The frog is one of the types of Vertebrates most valuable
to the student, being readily obtained and easily dissected.
The accompanying figure represents the anatomy of the
spotted or leopard frog, Rana halecina, male.
The skin is smooth, having neither scales, feathers, nor
hairs, and contains numerous microscopic glands, of which
there are said to be two kinds — one having an acid, the other
an alkaline secretion (L. Hermann). It is pigmented on
the dorsal surface, but whitish underneath. The head is
broad, triangular, with two large nasal openings in front,
large and prominent eyes, two tympanic membranes formed
by a part of the integument stretched across a hard ring,
.and an enormous mouth. The neck is short and not con-
stricted. The body tapers slightly posteriorly, and has the
•opening of the cloaca upon the posterior end of its back.
3£ach limb consists of the three divisions : in the front leg,
brachium, antebrachium, and manus with four digits, of
•which the fourth is very much thickened in the male ; the
.sexes may be distinguished by this mark. In the hind leg
the three divisions are the femur, cms, and pes, with five
long digits, between which the membranous web is stretched.
If the web is examined in a living frog with a microscope,
the circulation of the blood in the capillaries can be studied.
The current of corpuscles and plasma is constant, and in a
given vessel passes only in one direction ; by following the
-stream backwards and forwards it will be found to issue
from larger vessels, the arteries, and to enter into other and
different vessels, the veins. The pigment corpuscles can
also be seen in the web ; they are branching bodies, capable
of drawing in or expanding their processes, and they can be
made to contract by an electrical shock from an induction
apparatus.
* Also see Ecker's Anatomy of the Frog; and the manuals of Mivart
and of Marshall; also Huxley and Martin's Biology.
ANATOMY OF THE COMMON FROG. 471
Slit open the skin along the median ventral line the
whole length of the animal, turn the skin back, and then
out through the muscular walls of the abdomen, being care-
ful not to injure the underlying organs. The viscera will
then be exposed : the coiled intestine, the large liver, and in
the female the sexual organs at either side ; finally, pos-
teriorly, the thin-walled bladder, B. The next step is to
seize the posterior end of the sternum with a pair of for-
ceps, lift it up, cut the fibres which run from its under sur-
face, and cut with a pair of strong scissors along both sides
of the sternum and around its anterior end, so as to remove
it entirely. Underneath the sternum lies a thin-walled bag,
the pericardium, enclosing the heart. On either side are
the lungs.
To complete the preparation dissect out the intestine, by
cutting through the mesentery ; follow it to the stomach,
which must be separated from the oesophagus and drawn
-aside together with the intestine, while the liver must be
turned over to the right of the animal. The pericardium
must be cut through and removed without injury to the
heart ; finally, the skin must be removed from the hind
legs. If the dissection is of a male, it will then appear very
much as in the figure.
The heart is conical in shape ; its apex points backwards,
and is formed by a single chamber, the ventricle, with thick
muscular walls, from which springs on the ventral surface a
little to the right the truncus arteriosus (-40), which runs
forward and divides into the two aortic arches. The base of
the heart contains two chambers, the right and left auricles,
the separation of which is not marked externally. A large
vein ( F) passes from the liver to the back of the heart, and
there empties into a thin-walled sac, the sinus venosui
which also receives on either side a vein from above, tit'
vence caves superiores. The vein from the liver receives alsc
the genital and renal veins, and is then called the vena cava
inferior. As the heart continues to beat for many hours
after a frog has been killed, if a fresh specimen is taken for
•dissection the rythmically alternating dilatations and con-
tractions may be observed. The order of contraction is,
472 ZOOLOGY.
1st, the sinus venosus ; 2d, both auricles ; 3d, the ventricle ;
4th, the truncus.
In front of and below the heart may be seen the trachea,
easily recognized by the hard rings of cartilage, and having
the larynx just in front of the aortic arches and giving off
two branches posteriorly, the bronchi, which run directly to
the lungs. The trachea overlies the oesophagus, which ter-
minates in the stomach (St). On either side of the trachea
lies a thyroid gland (th).
The liver (Li) is a large brown mass, composed of two
lobes, of which the left is the larger, and subdivided into
two. Between the two lobes lies a small greenish sac, the
gall-bladder (b). The liver receives a large vein (pv) from
the kidneys ; this is the portal vein, which distributes to the
liver the blood which has already once passed through the
capillaries of the other abdominal viscera. The hepatic vein
takes the blood from the liver directly to the heart.
The stomach (St), when in situ, lies on the left side of the
abdominal cavity, its oesophageal end being the largest ; it
leads directly into the intestine, which is of uniform width
throughout, but terminates in the dilated rectum (R), which
in its turn opens into the cloaca. To the ventral surface of
the cloaca is appended the bladder (B). Imbedded in the
mesentery near the commencement of the intestine is a pale
compact mass, the pancreas, not represented in the figure,
and a little farther from the stomach a small round dark
body, the spleen (Sp).
The kidneys (Kl) are two elongated deep red bodies, upon
which lie a number of yellow spots, the adrenal gland*.
The renal ducts arise from the outer and anterior portion of
the kidneys and then run backwards as two white convoluted
canals (vd), at first very narrow, then widening, and end-
ing with a dilatation immediately before they open into the
cloaca. These ducts serve at once as ureters and vasa defer-
entia. In front of the kidneys lie a pair of oval yellow
bodies, the testes (Te). The female has both ureter and
oviduct. The ovary varies greatly in size and appearance
according to its condition. The oviduct is a very long con-
voluted tube running from the pericardium backwards to
ANATOMY OF THE COMMON FROG. 473
the cloaca, where it opens just in front of the ureter. At
the season of reproduction the oviduct is found very much
distended with ova. Its anterior end has a ciliated opening
into the body-cavity. In the neighborhood of the sexual
glands lies the fat-body (/).
The lungs (l,u) are two large sacs with very elastic walls,
richly supplied with blood-vessels. These vessels spring
from the pulmonary artery. From each division of the
t mucus arteriosus are given off four branches (Fig. 433, II).
The first is the pulmonary aorta (Pet}, Avhich also gives off
a large cutaneous branch ; the second, the true aortic arch
(Ao), which, curving backwards, unites with its fellow just
in front of the kidneys and below the spinal column, to form
the descending aorta ; the third (cr), the carotid artery, run-
ning to the head, and bearing at its origin the singular caro-
tid gland (eg) ; the fourth, the lingual artery. The blood
is returned from the lungs by two veins, which empty into
the left auricle.
The space of the lower jaw is covered over by a thin trans-
verse muscle (My), the mylohyoid. On either side behind
the posterior edge of this muscle lies a croaking bag or air-
sac (S). In the mouth are to be observed, 1st, the mus-
cular tongue, attached by its anterior end to the lower jaw,
and forked posteriorly ; 2d, the openings of the nasal cavi-
ties ; 3d, the recessus Eustacltii, lying farther back, and
leading into the tympanic cavity ; 4th, f.ie opening of the
oesophagus ; and 5th, the slit-like epiglottis.
The muscles are best dissected in alcoholic specimens.
The muscles of the hind limbs are as follows : On the ven-
tral surface, the cut ends of the recti abdinnini* (r.al.)\
on the ventral surface, 1, of the thigh, outwardly musculua
vastus internus (mvi), the adductor long us (a), the sur*
tttriiis (it**), adductor tnagnus (ft"), rectus internes minor
(ri") ; the rectus internus major (n") ; a small part of the
addnrtor brevis can be seen close to the pubis between the
adductor magnus and the rectus internus major ; underneath
the rectus internus major lies the long and the semilnidino-
sus with two heads ; 2, of the leg (crus) gastrocnemius (//),
ar>d between that muscle and the bone the tibialis posticus ;
ZOOLOGY.
f.
FIG. 433.— Anatomy of the common Frog.
ANATOMY OF THE COMMON FROG. 475
in front is the iibialis anticus (fa). On the dorsal surface
of the thigh (Fig. 433. Ill) the ylutceus (gl), the pyriformis
(p), the reel us anticus femoris (ra), the vastus externus
(i'e), the biceps (b], the semimembranosus (sni), lying deep
between the biceps und semimembranosus are seen the
femoral vessels and sciatic nerve ; the rectns anticus, vastus
internus and externus are known collectively as the triceps
femoris ; in the leg the gastrocnemius (y] and peronceus (p).
The sympathetic nerves can be seen as two cords, one on
either side of the vertebral column. The spinal nerves can
be seen as white threads on the dorsal surface of the body-
cavity. The brain (Fig. 373) may be dissected out by open-
ing the skull from above. The olfactory lobes of frogs and
toads are fused together, but separate in the tailed Batrachia.
The seventh, eighth, and ninth spinal nerves unite to
form the very large sciatic trunk ; the intercommunications
of these nerves form the lumbar plexus ; while the second
and third spinal nerves form the brachial plexus from which
arises the brachial nerve. (C. S. Minot.)
Certain glands in the skin of some Batrachians secrete a
corrosive, or as in the European Salamandra maculosa, a nar-
cotic poison, which is poisonous to small animals. Tho
toads secrete in the parotid glands a bad-smelling fluid,
which applied to tender skins produces erysipelas. Lacerda
states that the poison of the Brazilian Bufo ictericus is a
milky humor from the glands on the sides of the neck. The
action of the poison is less fatal to small animals than that
of the European toad ; it gives a slight acid reaction and is
not soluble in alcohol, while that of the European toad is.
Like fishes, the Batrachians assume high colors during
the breeding season. The males of the newts at this time
Fig. 433.— Anatomy of common Frog. My, mylohyoid ; sr, sternoradials ; tfi,
thyroid; hi, lungs;./', fat-body; Te, testis; St, stomach; Sp, spleen; R, rectum;
«, adductor longus'; mri, vastus internus; ins, eartorms; rV, rectus interims
major ; ta, tibialis anticus ; g, gastrocnemius ; ri", rectus internus minor ; a", ad-
ductor magnus ; rab, rectus abdominalis ; S, bladder; ml, vas deferens ; b, gall-
bladder; Ki, kidney ; pv, portal vein ; Li, liver ; V, vena cava inferior ; Ao, aorta ;
S, vocal sac, or croaking-bag.
II. Origin of the arterial trunks. I, arteria ingnalis ; eg, carotid gland, which is
merely a re.te mirabile ; cr, carotid artery ; Ao, aortic arch : Pa, pulmonary artery.
III. Dorsal view of muscles of hind leg. r/l, glutteus ; ra, rectus anterior ; p, pyri-
formis ; tie, vastus externus; sin, semi-membraiiosus ; b, biceps ; g, gastrocnemius;
per, perorueus.— Drawn by C. S. Minot.
ZOOLOGY.
acquire the dorsal crest and a broader tail-fin, while in some
species prehensile claws are temporarily developed on the fore
legs of the male. The males of the Anura (toads and frogs)
are musical, the females being comparatively silent ; the vocal
organs of the male are more developed than in the females, and
'in the edible frog (Rana esruli'iita) large sacs for producing
a greater volume of sound stand out on each side of the head
of the males. Among the few viviparous Batrachians known
is an Alpine European Salantiutdra (S. atra) which brings
forth its voung alive.
•/ O
It is common to find tadpoles in the winter in ponds,
which have been retarded in their metamorphosis, and by
artificial means this retardation may be greatly increased.
For example, Wyman is said to have kept tadpoles of the
bull-frog for seven years in a cellar.
Unlike the higher Vertebrates the segmentation of the egg
in the Amphibia is total, the process beginning usually about
three hours after impregnation in the frog, and lasting twen-
ty-four hours. The primitive streak, the notochord and
nervous system then arise as in other craniated Vertebrates.
After the appearance of the branchial arches, the gills begin
to bud out from them, finally forming the larger gills of the
tadpole. Unlike young fishes, the yolk is entirely absorbed
before the tadpole leaves the egg. In warm climates the
tadpoles hatch in four or five days after the eggs are laid.
When hatched the tadpole is not so well developed as in most
young fishes. The digestive canal at first is simple and
straight. Afterwards it becomes remarkably long and coiled
in a close spiral. The mouth is small (Fig. 434, J), with no
tongue and only horny toothless jaws. The vertebra of the
tadpole are biconcave as in fishes, afterwards becoming con-
verted into cup-and-ball joints.
The accompanying figures represent the external changes
of the toad from the time it is hatched until the form of the
adult is attained. The tadpoles of our American toad are
smaller and blacker in all stages of growth than those of the
frog. The tadpole is at first without any limbs (Fig. 434 A],
and with two pairs of gills ; soon the hinder legs bud out.
After this stage (B] is reached, the body begins to diminish in
METAMORPHOSIS OF BATRACHIANS. 477
size. The next important change is the growth of the front
legs and the partial disappearance of the tail ((7), while very
small toads (D and E), during midsummer, may be found on
the edges of the pools in which some of the nearly tailless tad-
poles may be seen swimming about. It is three years before
the Amphibia are capable of breeding. In the newts (Tri-
ton) the gills are in three pairs, larger and more complex
than in the frog ; the fore limbs are the first to grow out,
and the gilla persist long after the hind limbs are developed.
In the newts we have the larval state of the toads and frogs
persistent ; thus the successive steps in the development of
the individual frog is an epitome of the evolution of the
typical forms of the class to which it belongs.
C B
D
Fig 434.— Metamorphosis of the Toad. — After Owen ; from Tenney's Zoology.
In certain Batrachians as the Alpine salamander, the Su-
rinam toad (Pi pa) and the Hi/lodes of Guadaloupe in the
West Indies, the metamorphosis is suppressed, development
being direct ; though the young have gills, they do not lead
an aquatic life. In the axolotl there is a premature devel-
opment of the reproductive organs, the larvae as well as the
adults laying fertile eggs.
The Batrachians are inhabitants of the warmer and tern-*
perate zones. Frogs extend into the arctic circle. The
Amblystoma mavortium breeds at an altitude of about 8000
feet in the Rocky Mountains. Rana septentrionalis Baird
extends to Okak, Northern Labrador, where the climate is as
extreme as that of Southern Greenland ; frogs have also been
478 ZOOLOGY.
observed at the Yukon River in lat. 60° N., but the climate
there is milder than that of Labrador. The common toad
and a salamander (Plethodon glutinosa Baird ?) extend to
Southern Labrador.
Nearly 700 species of existing Batrachians are known, 101
of which are North American, and about 100 fossil forms
have been described.
There are five orders of Batrachians, Professor Cope's
classification being adopted in this work. Those Batrachians
with persistent gills are sometimes called Perennibrancliiates.
Order 1. Trachystomata. — The sirens have a long eel-like
body, with persistent gills ; there is no pelvis or hind limbs,
and the weak, small fore legs are four or three-toed. The-
great siren, Siren lacertina Linn., is sometimes a metre in
length, and has four toes in the fore leg ; it lives in swamps
and bayous from North Carolina and Southern Illinois to
the Gulf of Mexico. A small siren with three toes and
small gills is Pseudobranclius striatus Le Conte. It occurs
ill Georgia.
Order 2. Proteida. — This group is represented by the
Proteus of Austrian caves and the mud-puppy (Necturus}
of the United States. These Batrachians have bushy gills,
with gill-openings and well-developed teeth. In Proteus,
which is blind, there are three toes in the fore feet and two
in the hinder pair. In the mud-puppy, Necturus (formerly
Menobranchus) lateralis Baird, each foot is four-toed. The
head and body are broad and flat, brown with darker spots.
It has small eyes and is about half a metre (from 8 inches to
2 feet) in length. It inhabits the Mississippi Valley, extend-
ing eastward into the lakes of Central New York.* The
Proteus as well as the mud-puppy lay eggs.
Order 3. Urodela. — The tailed Batrachians or Salaman-
ders rarely have persistent gills, these organs being larval or
"transitory ; the body is still long and fish-like, the tail some-
times with a caudal fin-like expansion as in the newts, but is
usually rounded, and the four legs are always present. With
only one or two viviparous exceptions, most of them lay eggs
in the water. The eggs of Triton are laid singly on sub-
merged leaves ; those of Diemyctylus viridescens are laid
* See Gage's Observations on ... Necturus. Buffalo, 1882.
SALAMANDERS.
479
singly on leaves of Myriophyllum, which adhere to the glu-
tinous egg, concealing it.* (Cope.) Those of Desmognathus
are laid connected by a thread both on land and in water.
The common land salamander, or Phthodon cn/fhronotum
Baird, lays its eggs in summer in packets under damp
stones, leaves, etc. ; the young are born with gills, as is the
case with the viviparous Salamandra atra of the Alps. The
possession of gills by land salamanders, which have no use
for them, and which consequently drop off in a few days,
leads us justly to infer that the land salamanders are the de-
scendants of those which had aquatic larvae.
The lowest form of this order is the aquatic Congo-snake
or Amphiuma means Linn., in which the body is large, very
long, round and slender, with small rudimentary two-toed
limbs ; there are no gills, though spiracles survive. It lives
in swamps and sluggish streams of the Southern States.
A step higher in the Urodelous scale is the Menopoma, which
is still aquatic, with large spiracles, but the body and feet
are as in the true salamanders. The Menopoma Alleghani-
ense Harlan, called the hellbender or big water lizard, is
about half a metre (1^-2 feet) in length, and inhabits the
Mississippi Valley. Allied to the Amphiuma is the gigantic
Japanese salamander, Crt/ptobranchus Japonicus Van der
Hoeven, which is a metre in length. Allied in size to this
form was the great fossil sal inlander of the German Tertiary
formation, Andrias Sclieuchzeri, the homo diluvii testis of
Scheuchzer, thought by this author to be a fossil man.
In the true salamanders the body is still tailed, the eyes are
rather large ; there are no spiracles ; they breathe exclusively
by their lungs, except what respiration is carried on by the
skin.
The genus Amblystoma comprises our largest salamanders ;
they are terrestrial when adult, living in damp places and
feeding on insects. The larvae retain their gills to a period
when they are as large or even larger than the parent. The
most interesting of all the salamanders is the Amblystoma
mavortium, whose larva is called the axolotl, and was origi-
nally described as a perennibranchiate amphibian under the
name of Siredon lichenoides Baird. This larva is larger than
* Gage's Life-history of the Vermillion-spotted Newt. Am. Nat. 1891.
480 ZOOLOGY.
the adult, terrestrial form, sometimes being about a third of
a metre (12 inches) in length, the adult being twenty centim-
etres (8 inches) long, forming an example of what occurs
in the Amphibians and also certain insects, of the excess in
size and bulk of the larva over the more condensed adult
form. This law is also strikingly observed in the P«t'i/</r.«
(Fig. 437). This fact of prematuritive, accelerated, vegetatiye
development of the larva over the adult is an epitome of what
has happened in the life of this and other classes of animals.
The fossil, earliest
representatives of the
Amphibians, as we
shall see farther on,
were enormous, mon-
strous, larval, prem-
ature forms corn-
Fig. 435— Siredon or larval Salamander.— From pared With their Q6-
Tenney's Zoology. scendants. The same
law holds good in certain groups of Crustacea (trilobites),
insects, fishes, reptiles and mammals.
The axolotl or siredon abounds in the lakes of the Rocky
Mountain plateau from Montana to Mexico, from an altitude
of 4000 to 8000 or 9000 feet ; the Mexican axolotl being of
a different species, though closely allied to that of Colorado,
Utah and Wyoming. The Mexicans use the animal as food.
Late in the summer the siredons at Como Lake, Wyoming,
where we have observed them, transform in large numbers
into the adult stage, leaving the water and hiding under
sticks, etc., on land. Still larger numbers remain in the
lake, and breed there, as I have received the eggs from Mr.
William Carlin, of Como. Thousands of the fully-grown
siredons are washed ashore in the spring when the ice melts.
They do not appear at the surface of the lake until the last
of June, and disappear out of sight early in September.
The eggs are laid in masses, and are 2 millimetres in diameter.
Mr. F. F. Hubbell has observed in Como Lake, July 23d,
young siredons four to six centimetres (l£-2^ inches) in
length, and September 3d specimens eight centimetres (3
inches) long. In Utah, Mr. J. L. Barfoot raised in 1875
HABITS OF THE AXOLOTL. 481
several adults from the larva, and I have been told that sire-
dons in the mountains among the miners' camps near Salt
Lake City leave the water and transform. It thus appears
that in the elevated plateaus* as well as at the sea-coast, some
siredons transform while others do not. Mexican siredons
have for a number of years been bred from eggs in the
aquaria of Europe, laying eggs the second year.
The change from the larva to the adult consists, as we have
observed, in the absorption of the gills, Avhich disappear in
about four days ; meanwhile the tail-fins begin to be absorbed,
the costal grooves become marked, the head grows smaller,
the eyes larger, more protuberant, and the third day after
the gills begin to be absorbed the creature becomes dark,
spotted, and very active and restless, leaving the water. Their
metamorphosis may be greatly retarded and possibly wholly
checked by keeping them in deep water. The internal
changes in the bones of the head and in the teeth are very
marked, according to Dumeril.
Experiments made in Europe show that the legs and tail
of the axolotl, as of other larval salamanders, may be repro-
duced. We cut off a leg of an axolotl the first of November ;
it was fully reproduced, though of smaller size than the
others, a month later. The tail, according to Mr. L. A.
Lee, if partly removed, will grow out again as perfect as ever,
vertebrae and all.
The Tritons or water-newts, represented by our common,
pretty spotted newt, Diemyctylus viridescens Rafinesque, are
also known in Europe to become sexually mature in the larval
state when the gills are still present, as has been observed by
three different naturalists. The female larva of Lissotriton
punctatus has been known to lay eggs.
Order 4. Gymnopliiona. — The blind snake with its several
allies is the representative of this small but interesting order.
* It has been stated by De Saussure, Cope, Marsh, and more recently
by Weismann, that the siredon does not change in its native elevated
home. No naturalist has seen the Mexican siredon transform into an
Amblystoma, but as it does so in abundance in Wyoming and Utah,
it probably transforms in Mexico. (The adult Mexican form has recent-
ly been found, and is at the Smithsonian Institution.)
482 ZOOLOGY.
The body is snake-like, being long and cylindrical ; there
are no feet and no tail, the vent being situated at the blunt
end of the body. The skin is smooth externally, with scales
embedded in it, but with scale-like transverse wrinkles.* The
eyes are minute, covered by the skin. The species inhabit
the tropics of South America, Java, Ceylon, and live like
earthworms in holes in the damp earth, feeding on insect
larvae. They are large, growing several feet in length.
Ccecilia lumbricoides Daudin inhabits South America. Cce-
cilia compressicauda of Surinam is viviparous, the young
being born in water and possessing external gills which are
leaf-shaped sacs resting against the sides of the body ; when
the animal leaves the water they are absorbed, leaving a scar.
(Peters.) Siphonops Mexicana Dumeril and Bibron, is a
Mexican form.
Order 5. StegocepTiala. — Here belong an order of extinct
Batrachians, with three suborders, Labyrinthodontia, Gano-
cephnla, and Microsauria (Cope). In these forms the skulls
were either somewhat like those of the frogs, or the crania
were roofed in by solid fiat bones, similar to those of ganoid
fishes. The vertebras were biconcave. The limbs of the
Labyrinthodonts were like those of the tailed Batrachians, of
small size and weak, compared with the great size of the
body. Von Meyer states that Archegosaurus possessed
branchial arches when young, and that probably other Laby-
rinthodonts resembled it in this respect. It had paddles
instead of feet, the head had an armor of plates, and the
body was covered witli overlapping ganoid scales. It had
teeth like those of ganoid fishes ; it had a notochord, the
bodies of the vertebrae being neither bony nor cartilaginous.
Owen regards it as combining the characters of the perenni-
branchiate Amphibians and the Ganoid fishes. It was a
little over a metre (3£ feet) in length. It is a representative
of the suborder Ganocepliala.
While the older text-books in the restorations of Lalnj-
rinthodon represented it as like a toad, with large legs and
tailess, it is now known that some of the gigantic prede-
cessors of the salamanders and tritons had long tails, while
others had long, cylindrical, snake-like bodies. Unlike exist-
* The " scales" are flaps, not like the scales of fislies or icpliles.
Fie 434«.— Salamander, showing the double row of lateral sense-organs
)\ ; the dots on the head being organs of the same kind, o, gms.
Fig. 435a. — Head and tail-end of blind-snake
(Ccecilia).
Fig. 4356.— Young of Coecilia, with
the gills, and head of the same after
the gills have been absorbed.
Fig. 435c.— Skeleton of the hellbender (Menopomtn.
Fig. 435d.— Archegosaurus. A Labyrinthodout. (About four feet long; restored.)
[To face page 482.]
LABYRINTTTODONT BATRACHIANS. 483
ing Batrachians, their fossil ancestors had an armor of large
breast-plates, Avith smaller scales on the under and hinder
part of the body.
But the largest forms were the true Labyrinthodonts repre-
sented in the Carboniferous rocks of this country by Baphetes',
and in Europe by Antliracosaurus, Zygosaurus, and in the
Permian beds of Texas by Enjops. Labyrinthodonts also
abounded in the Triassic Period, and forms like the Euro-
pean Labyrin/hodon or Mastodontosaurus must have been
colossal in size. Footprints occur in the Subcarboniferous
rocks of this country which indicate forms still larger than
any yet discovered in the Old World. A large number
(thirty-four species, referable to seventeen genera) of medium*
sized Labyrinthodonts have been described from the coal
measures of Ohio by Cope which were characterized by
their long, limbless, snake-like bodies and pointed heads,
forming a still more decided approach to the Ganoids. This:
was the lowest group of Stegocepliala, called Microsauria by
Dawson.
Thus we have in these Labyrinthodonts synthetic or an-
nectant forms, which connect the fishes with the Am-
phibians, and on the other hand point to the incoming of
the reptiles. They were thus prematuritive, larval forms,,
which in certain characters anticipated the coming of a
higher type of Vertebrate. The reptiles were ushered
in during the Permian Period, the rocks of this age imme-
diately overlying the coal measures, though it should be
stated that there are obscure traces of reptiles in the Carbon-
iferous rocks. It is not improbable that evidence will be
found to substantiate the impression that the reptiles,
together with but independently of the Amphibians,
branched off from the Ganoid fishes, or from extinct forms
related to them.
Order G. Anura. — The toads and frogs represent this
order, which comprises tailless Batrachians, with the four
limbs present:, the toes being very long (due to the great
length of the calcaneum and astragalus), while the body is
short and broad, the skin soft and smooth, scaleless, though
small plates are sometimes embedded in it. The lower jaw is
484 ZOOLOGY.
usually toothless. The larva? are called tadpoles, and repre-
sent the adult form of the Perennibranchiates. The exter-
nal gills are in the adult replaced by shorter internal ones.
Among the lower frogs or arciferous Ann, "a of Cope, i.e.,
those with the acromial and coracoid bones divergent and
connected by distinct cartilage plates, are certain forms,
as Alytes, Pelobates, and Pelodi/fi1*, whose breeding habits
are peculiar and interesting. The eggs of Pelodiites are
deposited in small clusters in the water, those of Pelo-
bates in a thick loop. The male of the European Alt/1 c*
obstetricans winds a string of eggs which it takes from
the female, and goes into the water, where it remains
until the young (which have no gills) are hatched. The
American ^rnpJiiojnis, or spade-footed to.ad, is not known to
have this obstetrical habit. This singular toad appears sud-
denly and in great numbers. It remains but a day or
•two in the water, where it lays its eggs in bunches from
•one to three inches in diameter. The tadpoles hatch
in about six days after the eggs are laid ; their growth is
rapid, the young toads leaving the water in two or three
weeks. The croaking of this toad is harsh, peculiar, and
need not be confounded with that of any other species.
(Putnam.) As the specie-footed toads are rarely seen, it is
possible that they burrow in the soil, like the European
Alyfps. Another peculiarity in the reproductive habits of
Alt/tes, Pelobates, Cultripes, and Pelodt/fes is that they
.spawn at two seasons instead of one, and that their larva1,
like Psc-udes (Fig. 437), attain a greater size than those of
•other frogs before completing their metamorphosis. (Cope.)
Among the tree-toads, Polypedates of tropical Western
Africa, contrary to the usual habits of frogs, deposits its eggs
in a mass of jelly attached to the leaves of trees which bor-
der the shore overhanging a pond. On the arrival of the
rainy season, the eggs become washed into the pond below,
where the male frog fertilizes them. Our common piping
tree-toad (Hyla Pickcringii Le Conte), about the middle of
April, in the neighborhood of Boston, attaches her eggs
simply to aquatic plants. The young are hatched in about
twelve days.
S UPPEESSED MET A MO RP HO SIS.
485
As an example of a suppressed metamorphosis, due ap-
parently to a radical difference in the physical environment
of the animal, may be cited the case of a tree-toad in the
island of Guadeloupe. There are no marshes on this island,
consequently in a species of Hylodes the development of
the young is direct ; they hatch from the eggs which are
laid under moist leaves, without tails, and are otherwise, ex-
cept in size, like the adults. On the other hand, a tree-toad
of the island of Martinique {Hylodes Martinicensis, Fig.
436) has tadpoles, which it carries on its back. The female
of Nototrema marsupiatum Dumeril and Bibron, of the
Andes, has a marsupium or sac on its back in which the
young are carried. The Notodelp/t//*
of South America has similar habits ;
for example, the female Opistliodel-
])hy* (Notodelpliys] ocifeni has a dor-
sal sac a centimetre deep in which
the eggs are carried. In the young
of this and of Gastrotheca also of
Central America, Peters found traces
of external gills. The Pipa, or Suri-
nam toad (Pipa Americana Laurent),
which has no tongue, neither teeth in
the upper jaw, has similar breeding
habits. In this interesting toad the
young, according to Prof. Wyman,
are provided with small gills, which, however, are of no
use to them, as the tadpoles do not enter the water, but are
carried about in cavities on the back. The eggs are placed
by the male on the back of the female, where they are
fertilized. The female then enters the water ; the skin
thickens, rises up around each egg and forms a marsupial
sac or cell. The young pass through their metamorphosis
in the sacs, having tails and rudimentary gills ; these are
absorbed before they leave their cells, the limbs develop,
and the young pass out in the form of the adult.
The toad (Bufo lentii/hioxtix Shaw) is exceedingly useful as
a destroyer of noxious insects. It is nocturnal in its habits ;
is harmless, and can be taken up with impunity, though it
Fis;. 43t>. — The Martinique
Tree-toad carrying the young
OH its back.
486
ZOOLOGY.
Fig. 437.— The Paradoxical Frog. 1, 2, larva, nearly of natural wze ; 3, 4. PseiidfS
mini/tti, natural size.— 1, 2, after Pizarro ; 3, 4, after Garman. — From the American
Naturalist.
CLASSIFICATION OF BATRACH1ANS. 487
gives out an irritant acrid fluid from the skin, which may
poison the eyelids. In New England toads begin to make
their peculiar low trilling notes from the middle to the 20th
of April ; from the latter date until the first of June they
lay their eggs in long double strings, and the tadpoles (Fig.
434) are usually hatched in about ten days after the eggs are
deposited. (Putnam.)
The paradoxical frog of South America (Psendes para-
doxa "Wagler, Fig. 437, 1, 2, the larva) is remarkable from the
fact that the larva is larger than the adult. 3 and 4 repre-
sent another species of Pseudes (P. minuta}.
The highest genus of the Anura is Rana, of which there
are numerous species, our American forms being the bull-
frog (Rana pipiens Linn.), the Rana palustris Le Conte, or
pickerel-frog, and the marsh -frog (Rana halecina Kalm).
They lay their eggs in masses in the Avater in April, May,
and the early part of June, according to the latitude.
While most frogs are eaten by birds, and such species are
preserved from extinction by their nocturnal habits and their
protective resemblance to the herbage and the bark and leaves
of trees, Thomas Belt records the case of a little Nicaraguan
frog which is very abundant in damp woods, and "hops
about in the daytime, dressed in a bright livery of red and
blue." Its immunity from destruction is due to the fact
that ducks and fowl could not be induced to eat it, owing to
its unpleasant taste, the same reason inducing birds to reject
certain bright-colored caterpillars, which are distasteful to
them.
CLASS V.— BATRACHIA.
Amphibious Vertebrates, with gills in certain adult aquatic forms, all
breathing air by lungs ; the skin of existing species naked; with true
limbs like those of higher Vertebrates ; skull with two occipital condyles ;
heart with two auricles and one ventricle. Mostly oviparous; a distinct
metamorphosis.
Order 1. Trachystomata. — Body long, eel-like, with persistent gills ;
no pelvic bones or hind limbs; no maxillary bone. (Siren.)
488 ZOOLOGY.
Order 2. Proteida. — Body flattened, with persistent gills, and
openings ; a maxillary bone. (Proteus, Necturus.)
Order 3. Vrodela. — No persistent gills, body with a tail ; no gill-open-
ings except in Menopoma and Amphiuuia. (Salamandra.)
Order 4. Gymnophiona. — Body snake-like, no feet ; no tail ; young with
gills. (Coecilia.)
Order 5. Btegocephala. — Extinct forms; the temples with a bony roof;
often large ; either snake-like, without limbs, or with pad-
dle-like limbs, or with four legs ; teeth with or without
labyrinthine structure. (Archegosaurus, Labyrinthodon.)
Order 6. Anura. — Body short, tailless, with four limbs ; toes very long ;
leapers ; larvae tailed. (Bufo, Rana.)
Laboratory Work, — The student should carefully follow, with a speci-
men in hand, the description of the structure of the frog, aided by the
figure ; then should make a skeleton of the same species. These
studies should then be followed by a close comparison with the struc-
ture of a mud-puppy and of a salamander — the osteology and anat-
omy of the softer parts receiving equal attention. The breeding hab-
its of the Batrachians may be studied by confining them in jars or
aquaria. The embryology can best be studied by hardened stained
sections of the eggs.
CLASS VII. — REPTILIA (Lizards. Snakes, Turtles, and
Crocodiles}.
General Characters of Reptiles. — In the members of the
present class we have a still farther elaboration of a type of
structure which first appears in the Batrachians, with the
addition of features, which on the other hand are wrought
out in a more detailed manner in the birds, so much so that
while the fishes and Batrachians form one series (Ictliyop-
sida), a study of different fossil reptiles, especially the bird-
like reptiles (Dinosaurs and Pterosaurs), which clearly con-
nect the birds with the reptiles, shows that the two latter
groups should be united into a series called Saiiropxida.
Thus no one class of Vertebrates stands alone by itself ; every
year fresh researches by paleontologists, and the re-examina-
tions of living Vertebrates, especially as to their embryonic
history, proves that no single class, not even a type so well
REPTILES. 489
circumscribed as the modern birds, is without links forming-
genetic bonds allying them all together. In fact, the different
classes of Vertebrates, as well as of other branches of the
animal kingdom, form an ascending series, from the more-
generalized, though not always simple forms (numerous
groups comprising synthetic types), to those which are more
specialized, i.e., in which separate organs or groups of or-
gans are elaborated and worked out in great detail. This is
the tendency all through nature, and were Cuvier himself
now living, and were he to examine the facts revealed since
his death, he would, as many others in advanced life have
done, cast aside the limited, analytical notions of the past,
based as they were on fragmentary evidence, and adopt
the more philosophical principles of classification, based on
sciences that were in embryo thirty or forty years since.
These reflections have great force in the study of a class like
the reptiles where there are a larger number (six) of extinct,
than of living (five) orders, and where the fossil types were
of a more general, almost embryonic type, and consequently
gigantic and ill-shapen, showing a tendency to extremes or
prematurity in development rather than to an equality in and
maturity of the whole organization compared with their de-
scendants. A high degree of specialization of type tends
nearly always in living beings, plants as well as animals, to a
condensation and higher grade of form. These animals also
have given a name to 'the Age of Reptiles, the middle or
Mesozoic age of the world, when they were the dominant type;
of life.
The essential characters of reptiles are the following : As
regards the skeleton, the bodies of the vertebrae vary in being
either biconcave, concave in front, concave behind, or flat
at each end ; the cup-and-ball vertebrae are most common,,
forming a strong and flexible joint well fitted for general
motion. The ribs are well developed, the sternum is rhom-
boidal ; there are usually, if not always, more than three
toes. The body is covered with scales ; the blood is cold, the-
heart has in the crocodiles, the highest order, four chambers ;
two or more aortic branches persist, and certain memtranes,
called an amuion and allantois, envelop the embryo.
490
ZOOLOGY.
The vertebral column is now more distinctly marked off
than in the Batrachians ; a cervical and lumbar region being
indicated in most reptiles except the snakes and turtles. Well-
marked ribs exist in nearly all the vertebrae of the trunk,
except in the turtles, where the so-called ribs are possibly,
U
f\ r\
Fig. 438.— Skull of a Tur-
tle seen from behind, 1,
basi occipital ; 2, exoccipi-
tal; 3, supraoccipital ; 5, basi-
sphenoid ; 15, prootic (pe-
trosal) ; 17, quadrate.— After
Gegeubaur.
according to Gegenbaur, modified
transverse processes.
The skull of reptiles is much **
more like that of birds than of
Amphibians. There is a single
occipital condyle, and the lower
jaw is articulated by the quad-
rate-bone to the base of the skull.
The primitive skull, or that part
immediately enclosing the brain,
has an incomplete roof, but still
is more bony than in Batrachi-
ans ; while owing to the great
size of the bones developed orig-
inally in and from the palato-
quadrate cartilage, but a small
part of the true skull is to be
seen. The parts forming the iia of the toes.
hyoid suspensorium in fishes (hyomandibular and symplectic
bones) are, as in the Batrachians, entirely separate from the
skull.
While the limbs are, as a rule, absent in the snakes, the
lore legs always wanting, in a few forms, as the pythons,
Pi? 43g._B0nes of the foot of a
/ feffirf
STRUCTURE OF REPTILES. 491
boas, iind Tortrices, the pelvis exists in a rudimentary state,
and attached to it is a pair of rudimentary hind legs ending
in claws ; in all other existing reptiles the limbs are directly
comparable with those of birds and mammals, the bones of
the legs being best developed in the Chelonians (turtles),
which have nine carpal bones and five digits in each foot.
Certain extinct saurians had paddle-like limbs, others binl-
like limbs, and still others approached the crocodilian type,
in which the carpal bones and phalanges become reduced in
number. In the hind limbs an intermedium (in birds only
present in the embryo) is united with the lib idle bone to
form an astragalus or heel-bone.
The scales of reptiles are very characteristic, though scales
existed on the underside of the body of most Stegocephalous
Batrachia. The scales of lizards and snakes are developed
from the cutis. The large horny plates of Chelonians are
greatly developed and unite above with the "ribs" to form
the shell or carapace,, while nine large plates below form
the plastron.
The teeth are simple, conical, and while in the lizards
and snakes they may exist on the palatine and pterygoid
bones, in the crocodiles, where they are implanted in sockets
of the jaw-bones, they are, as in the mammals, confined to
the maxillary bones. The teeth are said to be acrodont when
situated on the edge, or pleurodont if on the side of the jaw,
or thecodont if inserted in sockets. There is a middle and
internal ear much as in birds. The New Zealand lizard,
Hatteriti, is the only reptile which has the beginning of a spiral
turn indicated in its cochlea, which in other reptiles is, as in
birds, merely a flask-shaped cavity. (Rolleston.) The eyes of
reptiles approach those of birds, and in both there is an upper
and a lower movable eyelid besides a nictitating membrane.*
True nostrils exist in reptiles for the first time among Ver-
tebrates, and may be closed like the ears by cutaneous valves.
The tongue is either not extended out of the mouth, and
is broad, as in turtles and crocodiles and some lizards, or as
in most lizards and all snakes it is long, slender, forked, and
can be darted rapidly out of the mouth.
* In mauy reptiles there is a median rudimentary, "pineal " eye.
492 ZOOLOGY.
True lips now, as in birds, border the jaw-bones, while-
salivary glands for the first time in the Vertebrates appear
in the Chelonians and lizards ; besides these there are smalier
glands in the lips of lizards and snakes, the poison-glands
of the rattlesnake, viper, etc., being modifications of t lie-so
labial glands.
While the oesophagus is wide and the stomach usually
quite simple, in the crocodiles there is a muscular gizzard
approaching that of birds, and there is a special pyloric por-
tion in the crocodiles like that of grallatorial and swimming
birds. The liver and pancreas have, as in birds, two or more
excretory ducts, and a gall-bladder is always present. A
large fat-body (Fig. 440, /) is present on each side of the-
body.
The lungs, trachea, and larynx of reptiles are much
simpler than in birds ; in the long slender-ringed trachea
there is an approach to that of birds, but the lungs are
modelled on the Amphibian type ; the larynx, especially in
the Chelonians and crocodiles, is much more perfect than in
the Amphibians.
The organs of circulation show a decided advance in situ-
ation over the Batrachians. The heart (Fig. 440) recedes
farther back into the thorax. Of the two auricles the right
and larger one receives the systemic and the left the pul-
monary veins. In all but the crocodile the ventricle has
a partition, the right half containing venous and the left
arterial blood, while in the crocodiles there are two ven-
tricles, so that the heart is four-chambered. In the lizards
two aortic branches (a right and a left) survive. In the
crocodiles a vessel which gives off the right aortic arch and
the carotids arises from the left ventricle, while a left aortic
arch and the pulmonary arteries arise from the right ven-
tricle. In the reptiles as in birds there are two superior as
well as one inferior vena cava. In reptiles as in lower Ver-
tebrates there are no true lymphatic glands ; an organ re-
sembling them is present in reptiles (Fig. 440. ///), forming a
small swelling situated behind the angle of the lower jaw.
While the brain is still simple, though it fills the cavity of
the skull, the different lobes being subequal in size, the cere-
ANATOMY OF THE LIZARD.
Fi?. 440.— Anatomy of a lizard, Sctlefiortis i/mlitldtug. t, trachea ; (, carotid artery;
th, thyroid gland ; h, ventricle of the heart— above are the two auricles; ///, lung:
/, liver turned out; «, stomach ; i, intestine; a, vent — above it the cloaca is laid
open to disclose the openings (o o) of the kidneys (AT, above are the two openings of
the oviducts; n, oviduct; o, ovary ; v, vena cava ; /, fat-body.— Drawn by A. t.
Gray from dissections made by the author.
494 ZOOLOG Y.
bellum is small, especially in the serpents. In the croco-
diles the brain most approaches that of birds, the cerebellum
being larger than usual in the middle, and in this respect
somewhat approaching the birds.* Corpora striata (which
are thickenings of the outer walls of the cerebral hemispheres)
and the anterior commissure of the cerebral hemispheres arc
present for the first time in the vertebrate series.
The kidneys (Fig. 440, &) are lobulated, varying in form
and position, and usually situated near the cloaca, the ureters
being short and opening into the cloaca. The reproductive
organs are generally like those of the Batrachians. The
ovaries lie on each side of the vertebral column, and vary in
size with the season, being largest during the time of repro-
duction. The oviducts (Fig. 440, n) are voluminous coiled
canals, which in most reptiles open into the cloaca ; in the
turtles, however, opening into the neck of the so-called
urinary bladder. After the egg passes into the oviduct it
is enveloped by the "white" or albumen, which is secreted
in the anterior part of the oviduct, while the thick-walled
terminal part secretes the shell.
The external differences between the sexes is more marked
than in the Amphibians. According to Darwin, the sexes of
the Chelonians and snakes differ very slightly ; male rattle-
snakes are said to be more yellow ; in the East Indian Dip-
sas cynodon the male is bright green, while the female is
bronze-colored. Male lizards are usually larger, while male
snakes are always smaller than those of the opposite sex.
Various appendages, suoh as crests, warts, horns, etc., when
present in both sexes, are most developed in the males,
while the colors and markings are brighter in the latter sex.
The moulting of the skin is effected by its being pushed off
by the upward growth of fine, temporary cuticular hairs.
On certain parts of the body, as on the underside of the
capsular skin and scales of the eyes, these hairs do not de-
velop. After the skin is loosened, it dries and is readily
shuffled off.
The eggs of turtles, like those of birds, are very large,
the yolk mass being greatly developed. The lizards, snakes,
and crocodiles lay their eggs in sand or light soil, while those
* Stegosaurus had the smallest brain proportionally of any land
vertebrate.
DEVELOPMENT OF REPTILES. 495
of the iguana are laid in the hollows of trees. Certain
snakes, as the vipers, are viviparous. In many snakes and
lizards the development of the embryo goes on in the egg
before it leaves the oviduct ; such species are said to be ovo-
viviparous, the young being born living. The Eutwnia
sirtalis, or common striped snake, brings forth its young
alive, and is probably ovoviviparous rather than viviparous.
The early phases of the development of the reptiles, in-
cluding the origin of the amnion and allantois, is much as
in the chick. In the turtle, by the time that the heart has
become three - chambered, the vertebrae have reached the
root of the tail, the eyes have become entirely enclosed in
complete orbits, and the allantois begins to grow. The
nostrils may now be recognized as two simple indentations
at the end of the head, and at first are not in communica-
tion with the mouth, but soon a shallow furrow leads to it.
The shield begins to develop by a budding out laterally of
the musculo-cutaneous layer along the sides of the body,
and by the growth of narrow ribs extending to the edge of
the shield. In the oviparous snakes (e.g., Natrix torquata)
the embryo partially develops before the egg is laid, while
the young hatches in two months after the egg is deposited.
By this time the amnion is perfected, the head is distinct,
and shows the eyeball and ear-sac ; also the maxillary and
mandibular processes. The allantois is about as large as the
head. The long trunk of the serpent grows in a series of
decreasing spirals, and when live or six are formed, the rudi-
ments of the liver and the primordial kidneys are discern-
ible. At the latter third of embryonic life the right lung
appears as a mere appendage to the beginning of the left.
The reptiles are essentially tropical and subtropical ani-
mals ; they are scarce in north temperate countries, though
in North America snakes extend north farther than lizards ;
in Europe snakes cease at 60° north latitude, and at GOOD
feet elevation in the Alps ; lizards in Europe sometimes ex-
tend farther north than snakes, and ascend to an elevation
of 10,000 feet in the Alps. Reptiles are usually wanting in
oceanic islands which possess no indigenous mammals, though
lizards are sometimes found on islands where there aro
490 ZOOLOGY.
neither mammals nor snakes. The reptiles in cool climates
hibernate, while those of the tropics have a summer-sleep in
the dry season, becoming active when the rainy season begins.
There are about three thousand species of living reptiles
known, of which three hundred and fifty-eight are North
American ; between three and four hundred fossil forms
have been described. The reptiles are divided into eleven
orders, of which six are extinct.
Order 1. OpMdia* The snakes, of which there are over
one hundred and thirty species in America north of Mexico,
have a remarkably long cylindrical body, the tail very long
and slender ; they are footless, with no shoulder girdle, and
are covered with scales, which are all shed simultaneously.
These scales are epidermal growths, and while usually they
overlap, in a few cases (Acrochordus, etc.] they are tubercu-
lar, and do not overlap. The eyes are not protected by true
lids, but the latter are thin, covering the eye permanently,
thus accounting for the fixed, stony stare of snakes. The
number of vertebras (which are hollow in front and convex
behind), may in the boa amount to more than four hundred.
Each vertebra, except the first (the atlas) is provided with
ribs, and the processes with articular facets, which interlock-
ing give great strength and flexibility to the spinal column.
The hyoid bone is very slightly developed, though the
tongue is long, forked, can be rapidly darted out, and with-
drawn into a sheath ; the quadrate bones connecting the
lower jaw with the skull are movable. The bones of the
brain-case are firmly united together, while those of the jaws
and palate are more or less freely movable to allow the snake
(the boa especially) to distend its throat immensely and
swallow comparatively large animals, though ordinary snakes
will swallow large toads and frogs and other snakes but
slightly smaller than themselves. In order to retain the
prey and prevent its slipping out of the mouth, the recurved
short conical teeth are developed on the maxillary, palatine,
pterygoid, and mandibular bones, and occasionally on the
premaxillaries ; they are not set in sockets, and consequently
are not used to crush or tear food.
The peculiar gliding motion of snakes is effected by the
* See Garman's Reptiles mid Batrachians of N. Am., 1883; also
Baird, Cope, etc.
ANATOMY OF THE SNAKE. 497
movements of the large ventral scales, which are successively
advanced, the hinder edges of the scales resting on the
.ground and forming fulcra ; resting on these the body is
then drawn or pushed rapidly forwards.
The brain of serpents is small, much as in the lizards, the
cerebellum being especially small and flat, while the cerebral
hemispheres together form a mass broader than long.
The more characteristic features of the internal anatomy
of snakes is a want of symmetry in the paired organs, as seen
in the absence of a second functional lung, and second pul-
monary artery, one of the lungs being minute, rudimentary,
while the other is very long and large ; the trachea is also
very long, while the right ovary is larger than the left -:nd
placed in front of it. The other viscera are so arranged as to
pack well in the long narrow body-cavity.
The student should dissect a snake with the aid of the ac-
companying figure of the common striped snake (Eutcenia
sir tails Baird;.
A few snakes are viviparous, as the vipers ; others are ovo-
viviparous. In the oviparous Natrix torquata of Europe,
the embryo partly develops before the egg is laid, while the
young hatches in two months after the egg is deposited. At this
time the amnion is fully formed, the head is distinct, as well
as the eyeball, and ear sac. The long body grows in a series
•of decreasing spirals, and when five or six are formed, the
rudiments of the liver and of the primordial kidneys may be
detected, while at the latter third of embryonic life, the
left lung appears as a mere appendage to the beginning of
the right. The embryo, at the time of hatching, is provided
with a temporary horny tooth on the snout to cut through
the egg shell.
Most snakes conform in coloration to the nature of the
soil or places they frequent ; some being, as in the rattlesnake
of the western plains, of the color of the soil in which they
burrow ; the little green snake is of the color of the grass
through which it glides ; others are dull gray or dusky, har-
monizing with the color of the trunks of trees on which
they rest. The poisonous Elaps of the Central American
forest is gaily and conspicuously colored ; indeed it can af-
ford to be brightly colored, as no birds dare to attack it.
-198
Fig. 441. — Anatomy of the common striped Snake. Hi/, hyoidean apparatus;
Tr, trachea; th. thyroid; Oe, oesophagus; T, thymus; Ht. heart; Br, bronchus;
L, lung; A, air-sac; Li. liver; On. ovary; O. gall-bladder; Pa, pancreas; Orf, ovi-
duct; Cl, cloaca; R, rectum; Orl', right oviduct cut off; u, ureter; K, kidney; F",
vena portaa; /, intestine.— Drawn by C. S. Minot.
POISONOUS SNAKES.
499
The Salenoglyph poisonous snakes may always ue recog-
nized by their broad, flattened heads, and usually short thick
bodies. The poison gland of the rattlesnake (Fig. 442, a) is
a modified salivary gland. The two fangs arc modifications
of maxillary teeth, each of which has been, so to speak,,
pressed flat, with the edges bent towards each other, and
soldered together, so as to form a hollow cylinder open at
both ends, the poison dnct leading into the basal opening.
When the fangs strike into the flesh, the muscles closing,
the jaws press upon the poison gland, forcing the poison
into the wound. The poison-fangs are largest in the most
deadly species, as
the viper ( Vij)cra).
the puff adder
(Clotho), the rat-
tlesnake, and fer-
de-lance (Tr'ujono-
cephalux), but are
small in the asps
or hooded snakes
(y«j<(). The bite
of -the rattlesnake
is intensely painful;
it is best cured by Fro. 443.— Head of the rattlesnake : a a, poison gland
J and its excretory duct : e, anterior temporal muscle ; /,
Slicking, freely hill- posterior temporal muscle ; g, digastricns ; h, external
, , pterygoid muscle ; i, middle temporal muscle ; q, arti-
Cing, anil by Canter- cttlo-maxillary ligament which joins the apnnenrotic
ii -i capsule of the poison gland ; r. the cervical angular
IZlllg tlie WOUIHI, muscle ; t. vertebro-mandibnlar muscle ; u, costo- man,-
and drinking large
quantities (at least a pint) of whiskey or brandy, sufficient,
ordinarily to produce insensibility. Deaths from the bite of:
rattlesnakes are not common, while in India it is estimated
that several thousand people annually die from the bite of
the cobra — 20,000 dying eac'x year from the bite of snakes-
and the attacks of wild beasts. The '"'rattle" of the rattle-
snake is a horny appendage formed of buttonlike compart-
ments ; the sound made by the rattle, which has been com-
pared by some to the stridulation of a Carolina locust, or of
the Cicada, is an alarm note, warning the intruder : the rat-
tle is sprung before the snake strikes. Allied to this suaka
500 ZOOLOGY.
is the copperhead (Ancistrodon contortrix Linn.) and the
black mocassin (Ancistrodon piscivorus Linn.). In the water
snakes the tails are laterally compressed, while the poison-
fangs are small. These snakes are not much over a metre in
length, and live far from land in the East Indian seas.
The poisonous snakes stand lowest in the series ; they are
succeeded by the striped snake, milk adder, and by the boas,
which attain a length of five metres ; while the anaconda
grows eight metres long.
In time snakes reach back to the Eocene Tertiary period,
when a great sea-snake (Titanophis), represented by several
species, one six metres in length, haunted the coast of Kew
Jersey, while in the western lake-deposits of the same age,
forms allied to the existing boa-constrictor were not un-
common. The snakes, then, appear to be a modern type
compared with the lizards, turtles, and crocodiles.*
Order 2. Pythonomorpha. — This group includes a num-
ber of colossal serpent-like forms, with paddle-like feet, which
are regarded by Cope as the types of a distinct order, char-
acterized by a complex suspensorium, by the absence of a
sternum and sacrum, by the rootless teeth, recurved parie-
tal bones, etc.
They were fifty and sixty feet in length, and Mnxaxannis
tnaximus Cope, from New Jersey was still more colossal.
They combined characters of the snakes, lizards, and plesio-
saurs, and correspond in a degree to the descriptions of the
mythical sea-serpent.
The resemblance to the Ophidians is still farther strength-
ened by the late discovery by Professor F. H. Snow, that one
of the forms (Liodon) was covered above by small imbricated
scales, like those of the snakes, rather than large ones, like
those of lizards. The more abundant type is the Mosa-
saurus of the Cretaceous seas, which was a huge sea-serpent
originally referred by Cuvier and Owen to the neighborhood
of the lace-lizards (Varanidce) ; Cope describes it as a long
slender reptile, with a pair of powerful paddles in front, a
moderately long neck, and flat pointed head, with a long
forked tongue. The very long tail was flat and deep, like
that of a great eel, forming a powerful propeller. The
* The sequence of orders of reptiles should be as on page 517.
ORDER OF LIZARDS. 501
arches of the vertebral column interlocked more extensively
than in other reptiles except the snakes. They swam rapidly
through the water by rap id undulations of their bodies aided
by the paddles. The skull was not so strong, though as
light as that of the serpents. " While the jaws were longer, the
gape was not so extensive as in serpents of the higher groups,
for the os quadratum, the suspensor of the lower jaw, though
equally movable and fastened to widely spread supports, was
much shorter than in them. But there was a remarkable
arrangement to obviate any inconvenience arising from these
points. While the branches of the under jaw had no natural
connection, and possessed independent motion, as in all ser-
pents, they had the addition;] 1 peculiarity, not known else-
where among Vertebrates (except with snakes), of a movable
articulation a little behind the middle of each. Its direction
being oblique, the flexure was outwards and a little down-
wards, greatly expanding the width of the space between
them, and allowing their tips to close a little. A loose flexi-
ble pouch-like throat could then receive the entire prey
swallowed between the branches of the jaw ; the necessity of
holding it long in the teeth, or of passing it between the
short quadrate bones could not exist. Of course the glottis
and tongue would be forwards." The order became extinct
before the Tertiary Period.
n filer 3. Lacertilia. —The existing lizards or Saurians are
tho survivors or descendants of a multitude of forms, many
colossal in size, which characterized the Permian and Meso-
zoic periods ; while the extinct forms of reptiles were in
many cases synthetic types, with affinities to fishes, Am-
phibians, and even birds. The group as now existing is well
circumscribed.
Most lizards have cylindrical bodies, usually covered witli
small overlapping scales, with a long, slender tail, and general-
ly two pairs of feet, the toes long and slender, and ending in
claws. They run with great rapidity, and are active, agile
creatures, adorned with bright metallic colors, in some cases
green or brown, simulating the tints of the vegetation or
soil on which they live ; some are capable of changing their
color at will, as in the chameleon and Anolis ; this is due to
502 ZOOLOGY.
the fact that the pigment cells or chromutopliores are under
the influence of the voluntary nerves.
While the scales of the body are developed, as a rule, from
the epidermis, in the scink there are dermal scales (scutes),
and such dermal plates in the head may unite with the bones
of the skull. In most lizards, all except the Geckos, the
vertebra? are proccelous, i.e., with a ball-and-socket joint,
the vertebrae being rounded in front, and concave behind.
In the Geckos the vertebral column is fish-like, the notochord
persisting except in the centre of each vertebra, which is bi-
concave. In many lizards (Lncerta, Ljuana and the Geckos),
the middle of each caudal vertebra has a thin cartilaginous
o
partition, and it is at this point that the tails of these liz-
ards break off so easily when seized. In such cases the tail
is renewed, but is more stumpy. The tail of the specimen
of Sceloporus (Fig. 440) which we dissected is much shorter
than in the normal animal, and must have grown out after
having been lost.
The throat is often distensible by the hyoid apparatus ;
but the bones of the jaws ai'e firm, the bones united in front.
Both jaws are provided with teeth, while some have them
developed on the palatine and pterygoid bones. The teeth
are usually simple, sharp, conical, as in most lizards, includ-
ing the Monitor, or they are flattened, blade-like, with ser-
rated edges, as in the Iguana, or as in C't/rlt>t/tts they are
broad, adapted for crushing the food. Most lizards prey on
insects ; some live on plants. New teeth are usually devel-
oped at the bases of the old ones. They are attached to the
surface of its jaws ; in certain extinct forms (Thecodonts)
they are lodged in sockets. (Huxley.) The eyelids are
well developed except in the Geckos, in which the lids are
modified somewhat, as in the snakes, to form a transparent
skin over the cornea of the eyes. The tongue is free and
long, sometimes forked ; in the iguana it ends in a horny
point.
While the limbs are usually present, one or the other pair
may in rare cases (in Pseudopus the fore feet are wanting ; in
CMrotes the hind feet are absent) be absent, or as in A tn-
phisbfenn and its allies the feet are entirely wanting, though
HORNED TOADS. 503
ihe shoulder-girdle invariably remains, the pelvic-girdle in
such cases disappearing; the pelvis being complete, how-
ever, when there are hind limbs. The feet are usually five-
toed. The internal anatomy of lizards has already been de-
scribed and illustrated on p. 493. In the snake-like lizards
(Aiiyxix) the left lung is the smaller, and in Acontias
and Ti/p/iline it is almost wanting. A urinary bladder,
wanting in the snakes, is present in lizards.
The lizard lays eggs in the sand or soil ; those of the iguana
are deposited in the hollows of trees. Certain lizards are
viviparous.
There are between seven hundred and eight hundred species
of existing lizards, most of which inhabit tropical or subtrop-
ical countries ; eighty-two species of lizards inhabit America
north of Mexico. The earliest lizards date back to the Per-
mian formation in Texas, and in Europe to the Jurassic
rocks.
Reviewing some of the more interesting lizards in the as-
cending order, we may, passing over the snake-like, limbless
Amphisbcend, and the limbless glass snake (Opheosaurus),
first consider the chameleon of the Mediterranean shores, in
which the eyes are movable with a circular eyelid, and with
the five toes in two opposable groups adapted for grasping
twigs of trees. It is remarkable for its power of changing
its colors. The tongue of the chameleon (Fig. 443) is
capable of extending five or six inches, and is covered with
a sticky secretion for the capture of insects, as the crea-
ture itself is very sluggish. The chameleon of our country
is the A noli* of the Southern States, and is a long smooth-
bodied lizard, which can change its color from a bright pea-
green to a dec}) bronze-brown.
The horned toads (Phrynosomd) are characteristic of the
dry western plains ; the body is broad, flattened, and armed
with spines ; its coloration depends on that of the soil it in-
habits. It will stand long fasts. When PJtrynosoma DOH-
giasxii of the Northwestern Territories and States is about to
moult, small dry vesicles appear on the back and sides, run-
ning along the horizontal rows of pyramidal scales forming
the margin of the abdomen. In a day or two the vesicles
break and desquamation begins, which continues for eight or
504
ZOOLOGY.
ten days, the skin finally separating from the spines of tne
head and the claws. (Hoffman.)
Our most common lizard in the Middle and Southern
States is Sceloponis undulatus Harlan (Fig. 440). it is
common, running up trees. The iguanas are very large liz-
ards inhabiting the West Indies and Central America ; the
head is protected by numerous small shields, with a dorsal row
of bristling spines. They are about tlin-e feet long, live in
the lower branches of trees, and are said to be excellent eat-
ing. A still larger form, closely resembling the iguanas, is
the sea-lizard (Amblyrhynckus) of the Galapagos Islands,
where it lives in the rocks by the shore, feeding on seaweeds.
These large creatures are among the largest of existing liz-
Fig. 443.— Tongue of Chameleon. Natural size. — After Rymer Jones.
ards, being eighty-five centimetres (over 3 feet) in length.
Closely allied to the iguanas were a number of extinct sau-
rians of colossal size which nourished in the Jura-Trias and
Chalk Periods.
The largest lizard in Mexico is the Heloderma horridum
of Wiegmann. It grows to the length of one metre (over
three feet). It is allied to the iguanas, but the body is
heavily tuberculated. Heloderma suspect um Cope, inhab-
its southern Utah, Arizona, and New Mexico. The largest
of the existing lizards are the monitors, or species of Vara-
nus, of tropical rivers, which nearly rival the crocodiles in
size, being five or six feet in length.
Order 4. Clielonia. — Although the tortoises and turtles
are a well circumscribed group, with no aberrant or connect-
ANATOMY OF THE TURTLE. 505
ing forms, yet they have some affinities with the Batrachia.
They are distinguished from the other reptiles by the shell,
the upper part forming the carapace, and the lower the
plastron ; these two parts unite to form a case or box within
Fig. 444.— Skeleton of European Tortoise, with the plastron or under shell removetl
—After Owen.
which the turtle can retract its head and limbs and tail.
Owing to the presence of the carapace, the dorsal vertebras
are immovable, and the ribs are quite rudimentary.
The bones of the ventral shield or plastron are usually
£.06
ZOOLOGY.
nine in number. The jaws are toothless, being, as in birds,
encased in horny beaks*; there are rarely fleshy lips ; the
tongue is spoon-shaped and immovable. The heart consists
of two auricles and a ventricle. The brain has larger cere-
bral lobes than in the lizards. The eyes have a third lid, or
nictitating membrane. The student can best obtain an
idea of the organization of the turtles by studying the skel-
eton and dissecting a turtle with the aid of the accompany-
ing description and figure of the common turtle.
The common swamp-turtle (Ghrysemys picta) is a good
type of the Chelonia. The animal is enclosed in a hard shell
made up of an arched dorsal portion, and a flat ventral por-
M
•Hum.
Can-
Fig. 445. — Skeleton of the common spotted turtle. Jl/u, mandible: O, orbit of
eye; A, ear-opening; H, hyoid bone: Cer, cervical vertebrae; Dor. dorsal verte-
brae consolidated with the carapace (Car a); C<i it, caudal vertebrae; S, scapula;
Co, coracoid; St, sternum; Hum, humerus; Rod, radius; Ul, ulna; Car, carpal
bones; M, metacarpals; //, ilium; Pub, pubic bone; Is, ischiuna; Fern, femur; T,
tibia; F, fibula; Tar, tarsus; Pes, foot.
fcion, the two connected laterally, but widely separated an-
teriorly to give exit to the head and fore limbs, and pos-
teriorly for the tail and hind limbs. These parts can all be
withdrawn within the protecting shell, by being doubled or
folded back upon themselves. The soft parts of the skin are
covered with scale?, formed by overlapping folds. The limbs
are stout ; upon the anterior feet there are five, upon the
posterior four claws. On the under surface of the short
tapering tail near its base is the wide opening of the cloaca.
The ventral plastron consists of twelve symmetrical pieces,
six on each side. Fig. 445. The first and last pair are tri-
angular, the others are four-sided ; the fourth pair is the
* Teeth occur in the embryo of Trionyx ("Wiedersheim).
ANATOMY OF THK TURTLE.
50?
largest. Underneath the epidermal plates aro nine bony
pieces. The dorsal carafxice is composed of thirty-eight
plates, twenty-five marginal, of which the most anterior lies
in the middle line ; there are five median plates and a lateral
row of four plates on each side.
To dissect a turtle, saw through the lateral pieces of the
£3'
Fig. 446.— Anatomy of the Turtle, ChrijRemys p'tria.— Drawn by C. S. Minot.
shell which unite the plastron and carapace, then remove the
ventral piece, carefully freeing it from the organs beneath.
Fig. 446 represents a female, with the intestines and di-
gestive glands partially freed and turned aside, while the
shoulder-blade, oviduct, and ovary of the left side and the
508 ZOOLOGY.
right lung have "been entirely removed. The middle line of
the neck is occupied by the trachea, which overlies the much
wider oesophagus, which again rests upon two very large
cylindrical muscles, the powerful retractors of the head.
The muscles (R] extend backwards along the vertebral
column, behind the heart and through the abdomen. The
trachea branches just in front of the heart, to send ;*
bronchus to each lung. The left bronchus can be seen in
the figure, passing between the pulmonary artery (p) in
front, and the pulmonary vein behind ; the three tubes run
closely parallel forming the so-called root of the lung.
Each lung (Lu] is a large elastic sack with numerous air-
cells. The size of the lung depends upon its degree of ex-
pansion; when entirely collapsed it is quite small, but it may
easily be blown up through the trachea. The heart (Ht) is
much broader than in the frog or bird. We shall recur to
its structure presently.
Below the trachea lies the much larger oesophagus, a cyl-
indrical tube with muscular Avails. The oesophagus termi-
nates in the stomach (£), which, together with the remaining
digestive organs and the spleen, is drawn aside in the figure.
The long and coiled intestine can be followed to the point
where it passes under the oviducts (ord) and the bladder
(/?/) to terminate in the cloaca, the external opening of
which is represented at Cl. The main mass of the elongated,
gray, and mottled liver lies upon the intestine, being turned
so as to show its raphe (m), by which it is suspended from the
peritonaeum, the portal vein (r), and the retort-like gall-
bladder ((f) ; the gall duct passes through the body of the
pancreas (Pan), an elongated whitish mass resting upon the
first coil of the intestine, the so-called duodenum. Alongside
the pancreas is the much smaller dark oval spleen ($p)-
The specimen figured is a female killed during the period
of reproduction. The genital organs are therefore enor-
mously developed. The long and prominent oviducts con-
tained eggs already provided with a shell. The right
oviduct is seen drawn out and suspended by a mesentery, a
thin and transparent membrane with numerous blood ves-
sels. The lower end of the oviduct is seen through the
ANATOMY OF THE TURTLE.
509
mesentery, and contains three oval eggs, one of which is
lettered Eg. The oviduct can be followed to its anterior-
end which is much pigmented and has a terminal opening.
The cut-end of the left oviduct (ovd) shows the folds of the
lining mucous membrane.
The ovary (o) is likewise suspended by a thin membrane,
the mesovarium, and is equally developed on both sides in a
complete specimen. It is easily recognized by the numerous
bulging yellow spheres, of all sizes, which are the egg-yolks
in various stages of development.
The heart of the turtle (Fig. 447) will repay careful dis-
section. A small round body lies just in front of it ; this is
usually considered the equivalent of the thyroid gland,
through its real nature is still un-
certain. The heart itself (Fig. 447)
consists of two auricles and one
ventricle (ven), with an imper-
fect internal septum. It receives
the veins upon its dorsal surface,
and gives off the arterial trunks
from its ventral side. The two
auricles are equal in size ; together
they a little more than equal the
ventricle. The arterial vessels arise
together a little to the right, and
are most conveniently described as
three in number : 1st. The right
aorta (R Ao) arising on the left ;
3d. The left aorta on the right Fig. 447.— ventral surface of
., . the heart of the Turtle, Cliryse-
(L Ao) • the tWO CrOSS near their mys pitta. Dissected and drawn
. . T i i i by C. S. Minot.
origin and curve upwards and back-
wards, to reunite posteriorly just in front of the retractor
muscles, their union forming the single median descending
aorta ; 3d. The pulmonary aorta (p(t), which soon divides
into a branch for each lung. The left aorta gives off a
branch (d) which persists as a mere cord, the remnant of the
(/xrfus arteriosus, which originally united the aorta with the
pulmonary artery. The right aorta gives off an innominate
branch, that soon divides, and from each division springs
510 ZOOLOGY.
the carotis (car), and subclavian artery of the same side. The
veins are two in number, as they enter the heart : 1st. The
pulmonary veins (pv) unite to form a very short trunk
emptying into the left auricle ; while (2d) the two venw
ctvcv xtt/it'riiires unite with the cava inferior (V) to empty
through the sinus venosus into the right auricle.
The kidneys lie at the posterior end of the body against
the vertebral column. In the figure they are concealed by
the bladder and oviducts. (Minot.)
There are about forty species of Chelonians in America
north of Mexico. The lower forms of turtles are the marine
species. Such is the great sea-turtle (Sphargis coriiK'i'n
Gray) of the Atlantic and Mediterranean, which is the
largest of all existing turtles, and is sometimes eight feet
long, weighing from eight hundred to twelve hundred pounds.
Next to this species is the loggerhead turtle (Thalassochelys
cnouana Fitzinger), which is sometimes seen asleep in mid-
ocean. Still another is the hawk-bill or tortoise-shell turtle
(Eretmoclielys imbricata Fitz. ), the plates of whose shell is
an article of commerce. The green-turtle of the West
Indies weighs from two hundred to three hundred pounds,
and is used for making delicious soups and steaks ; being
caught at night when laying its eggs on sandy shores. All
the foregoing species have large, flat, broad flippers or fin-like
limbs, while in the pond and river turtles the feet are webbed,
and the toes distinct. A very ferocious species is the common
soft-shelled turtle (Axpidonectes spin if er Lesueur), whose
shell is covered with a thick leathery skin. It is carnivorous,
voracious, living in shallow muddy water, throwing itself
forward upon small animals forming its prey. The snap-
ping-turtle (Chelydra serpent inn Schweigger) sometimes
becomes four feet long; its ferocity is well known ; the flesh
makes an excellent soup.
The terrapins belong to the genus Pseudemys ; the pretty
painted turtle (Chrysemys picta Agassiz) is common in the
Eastern States, while the Nanemys gut tat us (Agassiz), or
spotted tortoise, is black, spotted with orange. In the land
tortoises the feet are short and stumpy. The Testudo Indica
of India is three feet in length. The great laud tortoises of
THE ICHTHYOSAURI 511
the Galapagos Islands, the Mascarine Islands (Mauritius and
Rodriguez), and also of the Aldabra Islands, lying northwest
of Madagascar, are in some cases colossal in size, the shells
being nearly two metres (six feet) in length. The fierce Mas-
carine species were contemporaries of the dodo and solitaire,
and are now extinct. The bones of extinct similar species
have been found in Malta and in one of the West Indian
islands. The land tortoises are long-lived and often reach a
great age. Certain tortoises of the Tertiary Period, as the
Colossochelys of the Himalayas had a shell twelve feet long
and six feet high. The turtles extend back in geological
time to the Jurassic, a species of Compsemys being char-
acteristic of the Upper Jurassic beds of the Rocky Moun-
tains. (Marsh.)
The eggs of turtles, as those of birds, are of large size ;
they are buried in June in the sand and left to be hatched
by the warmth of the sun. It is probable that turtles do not
lay eggs until eleven to thirteen years of age. The develop-
ment of turtles is much as in the chick. By the time the
heart becomes three -chambered, the vertebrae develop as far
as the root of the tail, and the eyes are completely enclosed
in their orbits. The shield begins to develop as lateral folds
along the sides of the body, the narrow ribs extending to the
edge of the shield. In the lower forms of turtles (the
Ghelonioidce), the paddle-like feet are formed by the bones of
the toe becoming very long, while the web is hardened by
the development of densely packed scales, so that the foot is
nearly as rigid as the blade of an oar.
OrderS. RhyncJiocep]ialia.—r^\\Q only living representa-
tive of this order is the Splienodon or Hatter ia of New Zea-
land ; a lizard-like form of simpler structure, however, than
the lizards in general.* This rare creature somewhat re-
sembles an iguana in appearance, having a dorsal row of
spines. It is nearly a metre (32 inches) in length. In this
group the vertebrae are biconcave ; the quadrate bone is im-
movable, and there are other important characters based on
a study of the living and fossil forms, the latter represented
by the Triassic Rliynchosaurus and Hyperodapedon.
Order 6. Iclitliynpteryyia. — This order is entirely extinct.
* See Guenlher's Contribution to the Anatomy of Hatteria. London,
1867.
512
ZOOLOGY.
The Ichthyosaurs were colossal reptiles from two to thirteen
metres (six to forty feet) in length, swimming in the ocean by
four paddle-like limbs consisting of six rows of digital bones
Fit;. 448.— Skull of Ichthyosaurus ; lateral view. Pinx, premaxillary bone ; MX,
maxillary ; N~, nasal ; Fr, frontal ; Prf, prefrontal ; Pof, postfrontal ; Pa, parietal
Z, lachrymal; M, malar; Qj, quadratojugal ; Q, quadrate; Pob, postorhital ; Sq,
equamosal ; D. dentary; Ang, angular ; Art, articular ; 3. Ar, subarticular ; Pier
pterygoid.— After Cope.
the head was very large, the neck very short, and the orbits
were enormous ; the vertebras were remarkably short and bi-
concave. They were carniv-
orous, and powerful swim-
mers, and common in tho Ju-
rassic seas of Europe ; one
form existed in the Jurassic
times in Wyoming.
Order 7. T/ieromorpha. —
This order is divided into the
Pelycosauria and Aiwmo-
dontia. The beaked Saurians
were somewhat lizard-like, but
Fig. 449.— Posterior view of the skull of wei'6 Synthetic types. COmbill-
IchthyoKaurus ; lettering: as in Fig. 443, .
With following additions; Bo, basiocci- lllg the Characters OI the icll-
pital ; EJCO, Exoccipital ; Sup. 0, supra- ., ,, , .,
occipital ; Opo, opisthotic ; Slap, supra- thyOSaurs, tllC turtles, the
etapedial or hyomaudibnlar.— After Cope. /-, 7 ; •,-, ,, a -,•
Sphenodon, with those of liz-
ards, Dinosaurians, and crocodiles. The skull was short,
and in Dicynodon the jaws in front had the nipping, horny
beak of a turtle, while from behind in the upper jaw pro-
truded two long, curved, canine teeth. Dirt/not/on lii/rici'jis
Owen, had a skull about half a metre (20 inches) long.
THE PLESIOSAUR8.
513
Another form was still more like the turtles, the jaws being
toothless and enclosed in a nipping, horny beak. In Lys-
trosaurus (Fig. 450) the head was blunt, the jaws armed in
front with stout teeth, and behind with canine teeth ; and
these animals, anticipating in their dentition the lions and
tigers, were called by Owen Theriodonts (beast-toothed).
These forms lived during the Permian and Triassic times.*
Order 8. Sauropterygia. — The Plesiosaurus is the type
Prf
--.I/a;
An —
Fig. 450.— Skull of LystrosaurusfrontosusfTomCeapeCoAouy, Profile. Lettering
as in Fifr. 443 and 444, with the following additions : Etnom, ethmovonierine ; x/>/i,
sphenoid; pro. Prootic; Pt-er, Pterygoid ; Col, Columella ; JSctp, Ectopterygoid ;
Subart, subarticular bone.— From Cope.
of this extinct order. The Plesiosaurs were somewhat like
the Ichthyosaurs, swimming by paddle-like feet, but the neck
was very long, and the head rather small. The largest true
Plesiosaur was about nine metres in length. They ahounded
during the Jurassic and Cretaceous period. During the lat-
ter period off the coast of New Jersey and in the seas of
Kansas nourished huge Plesiosaurian reptiles, such as Elax-
mosaurus, which had an enormous compressed tail. The
* The Theromorphs were the earliest, most generalized reptiles.
514 ZOOLOGY.
vertebrae of E. i>lnhjnrus Cope, of the New Jersey m J-
beds, had vertebras nearly as large as those of an elephant,
while the creature was whale-like in bulk, the neck long and
flexible, the paddles short. The skull was light, with a
long, narrow, very flat muz/U- It must have been the ter-
ror of those times ; it was about fifteen metres (45 feet )
in length. (Cope.)
Order '•>. (.'rocodilia. — The crocodile, caiman, gavial, and
alligator are the types of this well-known group. They pre-
sent a decided step in advance of other reptiles, the heart
approaching that of birds, in having the ventricle completely
divided by a septum into two chambers ; the venous and arte-
rial blood mingle outside of the heart, not in it, as in the
foregoing living orders. The brain is also more like that of
birds, the cerebellum being broader than in the other rep-
tiles. The nostrils are
capable of closing, so
that crocodiles and
alligators draw their
prey under the water
and hold them there
until they are drown-
ed ; but they are
Fig. 451.-Head of the Florida Crocodile.-After obliged to drag them
Hornaday. ashore in order to eat
them. The skin is covered with horny, epidermal scales. The
conical teeth are lodged in sockets in the jaws. The vertebra
are concave in front and convex behind, or the reverse ; the
quadrate bone is immovable. The feet are partly webbed.
The crocodiles and gavials appeared during the Jurassic pe-
riod, but the early forms were marine and like gavials, tlip
head being long and narrow in front, with biconcave verte-
bras. They lay from twenty to thirty cylindrical eggs in the
sand on river banks. The crocodiles are distributed through'
out the tropics, even Australia ; the gavials are mostly con-
fined to India and Malaysia, and also Australia. The group
is represented in the Southern States by the alligator (A.
Mississippiensis Dnudin). It is nearly four metres (10-12
feet) long; while the Florida crocodile (C. aciitus Cuvier,
DINOSAURIAN BEPTILES. 515
Fig. 451) in which the jaws are much narrower, is over four
and a half metres (14 feet) long. It inhabits the rivers of
Florida where it is very rare, and also the West Indies and
South America. The cayman of Guiana belongs to a dis-
tinct genus, Caiman, and is characteristic of the rivers of
tropical South America.
Order 10. Dinosaur ia. — We now come to reptiles which
have more decided affinities as regards their skeleton (the
only parts preserved to us) to the birds, especially the os-
triches, than any reptiles yet mentioned ; while the Dino-
saurs were genuine reptiles, in the pelvis and hind limbs,
including the feet, they approached the birds. This is seen
especially in the ischium, which is long, slender, and inclined
backwards as in birds. In the hind limbs the resemblance
to birds is seen ; among other points, in the ascending pro-
cess of the astragalus, in the position of the farther (distal)
end of the fibula, and in their having onlv three functional
O */
toes. The fore limbs were shorter and smaller than the
hind extremities, sometimes remarkably so. Moreover, the
limb-bones, vertebra?, and their processes were sometimes
hollow ; the sacrum consisted of four or five consolidated
vertebra?, in this respect anticipating the birds and mam-
mals. They walked with a free step, like quadrupeds,
instead of crawling like reptiles ; some walked on the hind
legs alone, making a three-toed footprint, occasionally
putting down the forefoot, like the kangaroo. The lar-
gest Dinosaurs were the Iguanodon, which was from ten
to sixteen metres (30-50 feet) in length, and the Cama-
raxdiirus (Atlantosaurus) which was about twenty-seven
metres (80 feet) in length. The Cetioxdunts had a length of
from twenty to twenty-three metres (60-70 feet). The Ha-
(Iroxiiuritx stood on its ponderous hind legs, with a stature of
over eight metres (25 feet). These were bulky, inoffensive,
herbivorous monsters, able to rise up on their hind feet and
browse on the tops of trees ; their undue increase was
prevented by carnivorous forms like Lcelaps, which was an
active, possibly warm-blooded Dinosaur, with light, hollow
bones, large claws, and serrate, conical teeth. It stood six
metres (18 feet) high, and could leap a distance of ten,
metres through the air. (Cope.)
ZOOLOGY,
Still nearer the birds was the Compsognathus ; it was
only two thirds of a meter (2 feet) long, with a light head,
toothed jaws, and a very long, slender neck ; the hind limbs
were very large and disposed as in birds, the femur being
shorter than the tibia ; moreover, the fore legs were very
small. "It is impossible," says Huxley, "to look at the
conformation of this strange reptile and to doubt that it
hopped or walked, in an erect or semi-erect position, after
the manner of a bird, to which its long neck, slight head,
and small anterior limbs must have given it an extraordi-
nary resemblance." The so-called bird tracks of the Triassic
rocks of the valley of the Connecticut were all reptilian
footprints, and without doubt made by Dinosaurs with the
above-mentioned affinities to the birds. These bird-like,
colossal lizards appeared in the Jura-Trias Period, and be-
came extinct in late Cretaceous times.
Order 11. J'lrmxnurui. — The forms of this order, rep-
resented by the Pterodactyles, would lead one to infer that the
group was still more bird-like than the Dinosaurs, and 8<'»>-
ley has shown that they have as many and important points
of similarity to that class as the preceding group. They are
a sort of reptilian bats, forming links between reptiles and
flying birds, as the Dinosaurs connect with the ostriches,
and it is in the hand and foot, which in birds are the most
characteristically ornithic, that they resemble the ornithic
type. They also approach birds in their long heads and
necks, the jaws with or without teeth, the short tail, in the
skull which is more rounded and bird-like than in other
reptiles, with large orbits, as also in the form of the brain ;
while the jaws were probably, in part at least, encased in
horny beaks. The shoulder girdle was bird-like, -and the
sternum was keeled, but the pelvis and limbs were like
those of lizards, while the fore-feet were much larger than
the hinder ones, and the nlnar finger was enormously
long and probably supported a broad membrane, connecting
the fore and hind limbs, as in bats ; moreover, the limb
bones were hollow, and air-cells were present, so that
these winged lizards could fly like birds or bats. The jaws
of the Pterosaurs were completely toothed ; those of the
CLASSIFICATION OF REPTILES. 517
Rhamphorhynchus had teeth in the back of the jaw, the
ends of the jaws being toothless and probably encased in
horny beaks, while in Pteranodon the jaws were toothless.
They were of different size, some expanding only as much
as a sparrow, others with a spread of about nine metres (37
feet). They were contemporaries of the Dinosaurs, several
forms, discovered by Marsh, occurring in the Cretaceous
beds of Kansas.
CLASS VI. REPTILIA.
Air-breathing Vertebrates, with limbs usually ending in daws; limbs
sometimes absent, rarely paddle-shaped ; body scaled ; ribs well developed ;
heart in the highest forms four-chambered; cold blooded; an incomplete
double circulation ; oviparous; eggs large; embryo with an amnion and
allantois ; no metamorphosis.
Order 1. Theromorpha. — Mammal-like sauriaus with solid pelvis and
shoulder-girdle, and with canine-like teeth, or toothless
and beaked. (Dkyuodon.)
Order 2. Sauropterygia. — Extinct colossal saurians, with long necks,
head of moderate size. (Plesiosaurus, Elasmosaurus.)
Order 3. Ichtliyopterygia. — Head large, orbits large; limbs paddle-
shiiped ; extinct forms. (Ichthyosaurus.)
Order 4. Rhynchocephalia. — Lizard-like; vertebrae bi-concave, species
mostly extinct. (Sphenodon.)
Order 5. Ophidia. — Body long, cylindrical, usually limbless; no shoul-
der-girdle. (Eutaenia.)
Order 6. Pythonomorpha. — Extinct, snake-like, limbs paddle-shaped.
(Mosasaurus.)
Order 7. Lacertiiia. — Body with a long tail; usually four limbs; mouth
not dilatable, the bones of the jaw being firm. (Sceleporus.)
Order 8. G1heloma.—Bo<\y enclosed in a thick shell, within which the
head and limbs can be withdrawn. (Testudo.)
Order 9. Crocodilia. — Thick - scaled ; heart four-chambered. (Croco-
dilus.)
Order 10. Dinosauria. — Colossal extinct saurians, capable of rising
and resting on the hind legs, and making three-toed tracks.
(Hadrosaurus.)
Order 11. Pterosauria. — Extinct flying saurians, with the fore limbs
large and a very long ulnar finger; toothed or toothless.
(Pterodactylus.)
618 ZOOLOGY.
CLASS VIII.— AYES (Birds).
General Characters of Birds. — We have met in the rep-
tiles, especially in the fossil forms, many characters indicat-
ing that birds are by no means so specialized or so well
circumscribed a group as was formerly supposed. Such a
relationship between the two classes has recently been still
further exhibited by Meyer's discovery of ArchcBOpteryx mac-
rum Owen of the Solenhofen slates of the Jurassic beds of
Germany, and by Marsh's discovery of birds with teeth and
biconcave vertebrae in the Cretaceous rocks of North Ameri-
ca. On account, therefore, of the close relations between
birds and reptiles, Huxley has placed these two classes in a
series called Sauropsida, which may be opposed to the Icli-
thi/ojixida. (Fishes and Batrachians) on the one hand, and
the Mammalia on the other, by the following characters : —
Sauropsida. — There are no mammary glands. There is
an amnion and an allantois ; the species are oviparous or
ovoviviparous, with reproductive organs and digestive canal
opening into a common cloaca, and AVolffian bodies replaced
functionally by permanent kidneys. There is no corpus
callosum, nor complete diaphragm. Respiration is effected
by lungs, never by gills. The heart is three or four cham-
bered, and there are usually two or three aortic arches ; in
birds but one ; there are red oval nucleated blood corpuscles.
The bodies of the vertebra are ossified, but without terminal
epiphyses. There is a single convex, occipital condyle, in
connection with an ossified basi-occipital. The ramus of
the mandible consists of several pieces, the articular one of
which is connected with the skull by a quadrate bone. The
ankle-joint is between the proximal and distal divisions of
the tarsus. The skin usually developes scales or feathers.
These important characters, derived from Huxley (as are
many of those given beyond for the class Aves), may remind
the student of the actual affinities between birds and rep-
tiles. The former are distinguished from other Sauropsida
by the following peculiarities : —
Aves. — The body is covered with feathers, a kind of der-
mal outgrowth found in no other animals. The fore limbs
STRUCTURE OF BIRDS. 519
form wings, serviceable in nearly all cases for flight. There
are never more than three digits in the hand, two of them
usually much reduced, and none of them bearing claws
(with rare exceptions); nor more than two separate carpal
boms in adult recent birds ; nor any separate interclavicle ;
the clavicles are normally complete, and coalesce to form a
*• merry - thought." The sternum is large, and usually
keeled (the only exception among recent forms being the
struthious birds); it ossifies from two to five or more centres,
and the ribs are attached to its sides. The skull articulates
with the spinal column by a single median convex condyle,
developed in connection with a large ossified basi-occipital.
The lower jaw consists of several pieces, articulated by a
quadrate bone to the skull, and in all recent birds both jaws
are toothless and encased in a horny beak. The bodies of
at least some of the vertebrae of recent birds have snb-cyclin-
drical, articular faces ; when these faces are spheroidal, they
are opisthocoelian, but some fossil forms are amphicoelian.
The proper sacral vertebrae have no expanded ribs abutting
against the ilia. The ilia are greatly prolonged forwards ;
the acetabulum is a ring, not a cup ; the ischia and pubes
are prolonged backwards ; there is no ischial symphysis ;
there may be a prepubis ; a process of the astragalus early
anchyloses with the tibia. The incomplete fibula does not
reach the ankle-joint ; there are not more than four digits,
the normal numbers of phalanges of which are 2, 3, 4, 5.
The 1st metatarsal is incomplete above ; the 3d, 3d and 4th
anchylose together, and with the distal tarsal bone unite to
form a tarso-metatarsus.* The heart is completely four-cham-
bered ; there is but one aortic arch (the right), and but one
pulmonic "trunk from the right ventricle; the blood is red
and hot. The large lungs are not free in the cavity of the
thorax, but fixed and moulded to the walls of that cavity :
and in all recent birds the larger air-passages of the lungs ter-
minate in air-sacs. All except the quadrate- ju gal and scapular
bones are hollow, and permeable to air from the lungs. There
is at most a rudimentary diaphragm. The eggs are very large,
in consequence of a copious supply of albuminous substance,
in the form of yolk and white, and are enclosed in a hard
* The structure is diagnostic of birds.
520
ZOOLOGY.
22
o .-• . \\ \ \ v \\ >:---\. x • \ \ » • \ 23
4- •/>m\.\\x\;N ^NU\ \ \ \ \ \ \ ' v x
46 454443424140393837 36 35 34 33 3231302928 27 26 25 24
Fig. 452.— Topography of a bird. 1. forehead (front); 2, lore; 3, circumorular
region ; 4, crown (vertex) ; 5, eye; 6, hind heart (occiput) ; 7, nape (nuclin) ; 8. hind
neck (cervix); 9, side of neck ; 10, interacapular region ; 11, dorst/m or back proper,
including 10 ; 12, notceum, or upper part of body proper, including 10. 1 1 and 13 ;
13, rump (i/ropyr/i/i/n); 14, upper tail coverts; 15, tail; 16, under tail coverts: 17,
tarsus ; 18, abdomen ; 19. hind toe (halht.r) ; 20. gaRtrcKiim. including 18 and 24 : 21,
outer or fourth toe ; 22. middle or third toe : 23, side of the body : 24, breast (jin-tuxr.
25, primaries ; 2K, secondaries ; 27, tertiaries. Nos. 25, 26. 27 are all niii'ni<s; 2S.
primary coverts ; 29. alula, or bastard wing ; :50. greater coverts ; 31, median coverts ;
32, lesser coverts : 33. the "throat," inclu'l!n<r 34, 37 and 38; 34, jiigi/liim, or lo\v«r
throat; 35, auriculars ; 3li, malar region; 37, gttta or middle throat; 38, menhini or
chin ; 3!), angle of commissure, or corner "of month ; 40, ramus of under man-
dible ; 41, side of tinder mandible ; 42, gonys ; 43, apex, or tip of bill ; 44, tomtit, or
cutting edges (if the bill ; 45, C'llmen, or ridee of upper mandible, corresponding to
gonys ; 46, side of upper mandible ; 47, nostril ; 48, passes urross the bill a little in
front of its face.— From Onus's Key.
Fig. 453o.— Cockatoo's
beak, the dotted line show-
ing the position of the up-
per bill when raised.
Fig. 452a.— Head of dove, ce, cere; n, nostril; w,
upper mandible; t, tomia; d, tooth; e, culmen; p, tips
of mandibles; i, under mandible; go, gonys; g, gape.
Al
Br
Fig. 4526.— Topography of the dove. Al, alula; B, belly; Bfc, back; Br, breast;
C, crown; E, ear; F, forehead; L, lore; Oc, greater coverts; Lc, lesser coverts; Me,
middle coverts; N, nape; O, occiput; P, primaries; S, secondaries; K, rump; Sr,
scutellate and reticulate tarsus; T,tail; Ta, tertiaries; Tc, tail-coverts; Th, throat.
[To face page 520.]
Fig. 456a.— Types of birds' feet. A, reticulate tarsus of black-bellied plover;
B, scutellate tarsus of meadow-lark; C, booted tarsus of robin; D, cursorial foot
of ostrich; E, rasorial foot of prairie-chicken; F, semi-palmated foot of peep; G,
totipalmate foot of wood-duck; H, of cormorant; /, tarso-metatarsus of penguin.
[To face page 521 .]
STRUCTURE OF BIRDS. 521
calcareous shell ; there is an amnion and allantois, and no
metamorphosis after hatching.
The external form of birds is very persistent ; the different
parts of the body have been named in terms of continual use
in descriptive ornithology. Hence, without entering into
details, we reproduce from Coues's "Key" his figure of the
topography of a bird.
The student, after a careful study of the external form,
should prepare a skeleton of the common fowl, or examine one
already at hand, and observe those characters peculiar to birds.
The skull is formed of bones consolidated into a more roomy
brain-box than in any reptiles, unless it be the Pterosaurians.
In the parrots the beak of the upper jaw is articulated (Fig.
453, n) to the skull, so that the movement of the beak on the
skull is unusually free. The
quadrate bone (Fig. 453, e) is
usually movable on the skull ;
and in the parrots when the
mouth opens the upper jaw rises,
since when the mandible is low-
ered, the qnadrato-iugal rod
,_,. _., ,. J ° Fig. 453.— Skull of Parrot : ,22, pre-
Or bar (V Ig. 400, /) pushes the maxillary bone ensheathi'rt in horn ;
•11 /oo\ ^ -i 15- nasal bones ; ?>, mandible, the
premaxilla (<2) Upwards and end sheathed with horn; I, malo-
forwards. This is a constant fea-
ture in recent birds, the degree f,',
of motion which this peculiar
mechanism allows being variable. °wen-
The form of a bird's vertebras is peculiar to the class ; the
articulation of the body (centrum) in all the vertebrae in
front of the sacrum being saddle-shaped. " In Str it/ops
and a few other land birds ; in the penguins, the terns, and
.-nine other aquatic birds, one or more vertebra? in the dor-
sal region are without the saddle-shaped articulation, and
are either opisthocoelian, or imperfectly biconcave." (Marsh.)
In the fossil Ichthyornis, which had a powerful flight, the
vertebras are bi-concave, as in fishes, and Amphibians, and
a few reptiles ; but the third cervical shows an approach to
the saddle - vertebrae of all other birds. The saddle form
renders the articulation strong and free, and especially
adapted to motion in a vertical plane. (Marsh.)
522
ZOOLOGY.
While the sternum of the cassowaries and other struthious
birds (Ratitce) is smooth, approaching that of reptiles, that
of the higher living birds is keeled or carinate (Fig. 454,
rr.y) ; hence these birds are called Cari-
natw ; to this keel and neighboring parts
the muscles which raise and lower the wings
are attached.
The fore limbs of birds (Fig. 455) are
greatly modified to form the framework of
the wings. In spreading and closing the
wings, the bones of the forearm slide along
each other in a peculiar manner. (Cones.)
The ulna is usually thicker and longer than
the radius, and there are only two carpal
bones, one radial, the other ulnar, in adult
recent birds. The hand in the Aptenjs and
cassowaries has but one complete digit,
while in other birds there are three digits,
which probably correspond to the first,
second, and third fingers of the human
hand. The wings are attached to a strong shoulder-girdle,
which consists of the two collar bones, uniting* to form the
wish-bone, and of acoracoid bone and scapula.
Fig. 454.— Sternum
of the Guinea Hen,
seen from in front ;
crs, crest ; c, coracoid
bone.— After Gegen-
baur.
Fig. 455.— Right wing bones of a young Chicken. A, shoulder ; B, elbow ; C, wrist
or carpus; D, tip of third finger; a, humerus ; ft, ulna; c, radius; d, scapholunar
bone ; e, cuneiform bone; /, y, epiphysea of metacarpal bones/, k, respectively ; h,
metacarpal and its digit i. — From Coues'sKey.
The pelvis of birds is remarkable for the long slender back-
wardly projecting ischium and pubic bones; there is generally
* The clavicles are separate in the emeu and toothed birds; absent
in the ostrich.
sJi
FIG. 455a. — Feather, s/i, shaft; v, vanes; A, barbule, with (be) the barbicels.
C.
FallSM'l
FallSM'l
HSISc't
FIG. 455&. — Six stages in the development of the feather. Feathers arise in
pits of the dermis lined by the epidermis: at the bottom of the pit is a papilla
(A, Pap) the epidermal investment of which Rives rise by rapid growth to the
feather. FK in B is the germ of the feather; C, section showing the horny layer.
At D, the barbs have grown out and become free; at E, the barbules of the
down-feather; F, the rudimentary feather; On,, derma; SM, Malpighian layer;
Sc, horny layer; ,SMf ', Scl. extensions of these tissues into the feather-papilla,
Pap: FK, feather -germ; F. Fl, feather-follicle; P, pulp; Ffil (SM1), folds of the
Malpighian layer extending into the feather-germ, and enclosed externally by
the horny layer HS^Sc1); both layers are seen in the transverse section (C!\; FSp,
quill of feather, which breaks up above into a tuft of rays or barbs (HSt); xrr-,
sec, secondary rays (barbules) arising from the latter; R~, rachis; Tr, vexillum. —
From Wiedersheim, mainly after Studer.
[To face p. 523.]
STRUCTURE OF BIRDS.
523
no bony union of the two pubic bones, nor do the ischia
unite with the sacrum or each other, except in Rhea. In the
ostrich, the pubic bones are solidly united. The hind limbs
(Fig. 456) are two, three, or four toed, the ostrich having
but two digits ; in most four-toed birds, one toe (the hallux)
is directed backwards, while in the parrots and trogons,
etc., there are two toes in front and two toes behind, and
in the swifts and certain other forms all
four toes are turned forwards. The bones of
the skeleton are dense and hard ; both the
long bones and the bones of the skull are
commonly hollow, containing air; the air-sacs,
in connection with the lungs, communicating
with the hollows of the bone. In some birds
which fly well, only the skull-bones have air-
cells, while in the ostrich which is unable to
fly, the bones have even a greater number of
cavities than the gull. The body during
flight is thus greatly lightened, and the bird
can sustain itself in the air for many hours in
succession.
With all these characters, the most re-
markable and diagnostic external feature is
the presence of feathers; no reptile on the
one hand, or mammal on the other, is clothed
with feathers, though the scales on the legs
and feet of birds are like those of reptiles,
but it should be borne in mind that feathers
are distinct in origin and structure from hairs.*
The ordinary feathers are called pennae or atar BUS ;'c' the same
J piece isolated, and
contour feathers ; as they determine by their seen from m front;
J J „ dd'. d"d'", the four
arrangement the outline ot the body. They toes.— After Gegen-
are, like hairs, developed in sacs in the skin ;
the quill is hollow, partly imbedded in the derm ; this merges
into the shaft, leaving the outgrowths on each side called barbs,
which send off secondary processes called barbules. These
tertiary processes (called barbules and booklets) are com-
monly serrated, and end in little hooks by which the bar-
bules interlock. Down is formed of feathers with soft.
* Jeffries' The Epidermal System of Birds. Proc. Bost. Soc. N. H.
1883.
Fig 456. — Hind
limb of a Hawk,
Buteo vnlgario. a,
femur ; b, tibia ; b',
fibula; c, tarso-met-
524
ZOOLOGY.
free barbs, called plumules. Over the tail-bone (coccy.r) are
usually sebaceous glands, which secrete an oil, used by the
bird in oiling and dress-
ing or "preening"' its
feathers. In some birds,
especially in the males of
the gallinaceous fowls, as
the cock and turkey, the
head and neck are orna-
mented with naked folds
of the skin called " combs"
Pig. 457. — Brain of t lie Hen. A , from above, ,,
B, from below ; a, olfactory bulbs ; b. cere- and Wattles.
bral hemispheres; c, optic lobes; (/, cerebel- ^f,^ i • • 11
him ; ci', its lateral parts ; e, medulla.— After Ihe Drain IS much larger
Carus, from Gegenbaur. ,n ,n ,•-> ,-,
than in the reptiles, the
cerebral hemispheres being greatly increased in size, while
the cerebellum is transversely furrowed, and is so large as to
cover the whole of the me-
dulla. The alimentary tract
consists of an oesophagus as
long as the neck ; it dilates
in the domestic fowl and other
seed-eating birds, as well as
in the raptorial birds, into a
lateral sac called the crop (in-
yluvies). The stomach is di-
vided into two parts, the first,
the proventriculus, which is
glandular, secreting a digest-
ive fluid ; and the second,
which corresponds to the pylo-
ri c end of the stomach in the
mammals, is round, with mus-
cular walls, especially develop-
ed in seed-eating birds, and
Called the " o-jzzard." In the Fig. 458.— Thymus (th} and thyroid 1/1
. .. .. . , "lands of a youns; hawk, Buteo viilf/uri*
fowl the gizzard IS lined With ol Europe;" lr, "trachea.— After Gegen-
a firm horny layer, by which
the food is crashed and comminuted, thus taking the place
of teeth. The intestine (including the large and small intes-
ANATOMY OF THE PIGEON. 525
tine) is long and ends in a cloaca, which receives the ends
of the urinary canals and oviducts. Attention should be
given to the trachea ; its bronchial branches, the larynx and
t\ie syrinx or lower larynx, which may be developed either
at the end of the trachea, or at the junction of the trachea,
and bronchi, or in the bronchi alone. The thymus gland
(Fig. 458, th) is very large and long, while the thyroid (t) is
a small, oval mass situated at the beginning of the bronchi.
The following account and drawings of the anatomy of
the pigeon have been prepared from original dissections by
Dr. C. S. Minot. As pigeons are one of the most readily
obtainable and convenient types of birds, the following
description of the anatomy of a male is given as illustrative
of the class, those peculiarities being especially noticed by
which birds are distinguished from reptiles and mammals.
Before dissecting a bird, it must be carefully plucked ;
this operation is much facilitated by dipping the animal in
boiling water for a few minutes. The limbs and muscles of
one, best of the left, side are to be removed ; the powerful
pectoral muscles cut off close to their attachment to the
keel of the breast-bone, and the ribs then cut away, care
being taken to avoid injuring any of the internal organs,
most of which will now be displayed in situ nearly as shown
in Fig. 459, which represents a dissection carried somewhat
further.
The skin (Fig. 459, E, from the neck) is characterized by
the presence of numerous ridges which cross one another,
so as to enclose quadrilateral spaces ; at the intersections
of the ridges are small pits in which the feathers are in-
serted.
The digestive canal begins in the horny bill with three
openings, one the large gape or mouth, and two oblique
elongated nasal clefts («), through which respiration is or-
dinarily alone effected. It then extends backward under-
neath the base of the skull, where it splits into the oesopha-
gus and trachea, two large tubes which run down the front
of the neck, the oesophagus on the right and the trachea
on the left. Just below the head the trachea lies, in its
normal position, in front of the oesophagus, though in most
526 ZOOLOGY.
adult birds both tubes follow a symmetrical course, but ex-
hibit a mock or secondary symmetry with regard to each
other. The origin of the two canals is embraced by the
hyoidean apparatus, one of the horns (cornua) of which ap-
pears at Hi] ; the apparatus is too complicated to be de-
scribed here ; it closely resembles that of reptiles, and is
functionally connected with the rapid thrusting out of the
tongue. In some birds, as, for example, the woodpeckers
and humming-birds, the horns are so developed as to curve
round the back of the cranium on to the top of the skull.
(Fig. 474).
The trachea (TV) is composed of cartilaginous rings with
intervening membranes, and an external sheath of connect-
ive tissue, which has been removed at Tr. It extends into
the thorax, and is of nearly uniform diameter throughout,
except at its lower extremity, where, as shown in Fig. 459,
D, it forms an enlargement, the syrinx or vocal chamber
(L), found only in birds, but wanting in the ostrich, etc.
(Ratit(c], storks, and certain birds of prey. The trachea
terminates immediately behind the syrinx in two smaller
branches, the bronchi (B], each of which passes into the
lung (Lu) of the same side. The cartilaginous rings of
the bronchi are incomplete, the walls being partly formed
by an elastic membrane. The rings of the trachea are pe-
culiarly modified in the syrinx, which is furnished with ex-
ternal muscles and internal membranous expansions, serving
to produce the voice ; the muscles are the sterno-tracheal,
furculo- or claviculo-tracheal, and the proper muscles of the
syrinx. A true larynx is present in the upper part of the
trachea, but is unessential to the formation of the voice.
The trachea presents flexuosities in various birds, usually
more marked in the male than in the female ; in swans there
is a great band which extends into the hollow breast-bone,
but the object of this disposition is unknown.
The lungs (Fig. 459, Lii) are two large sacs, placed dor-
sally in the anterior part of the body-cavity, but not suspend-
ed freely in a short thoracic sac nor enclosed in a pleura, as
in mammals ; they are composed of reddish spongy tissues,
and are attached between the ribs by connective tissue.
ANATOMY OF THE PIGEON. 527
Each lung has upon its outer and dorsal surface five trans-
verse depressions, corresponding to as many ribs. The
bronchi and pulmonary blood-vessels enter together the
anterior third of the lungs, and follow one another in their
ramifications, but the bronchus traverses the lungs, giving
off numerous branches, and opens into the abdominal air-
sac, while upon the surface of the lungs there are small
openings communicating with the remaining air-sacs.
These structures the student had best tear through and
altogether neglect in his first dissection. The air-sacs are
thin-walled bags, nine in number : three near the clavicle,
four in the thorax, and two in the abdomen ; their ramifi-
cations extend even into the bones, most of which are ac-
cordingly found to be hollow. This striking organization
is one of the most characteristic peculiarities of birds, and
serves to lighten the body by filling very large spaces with
air, besides fulfilling certain other less obvious functions.
In many chameleons and some Geckos the lungs have di-
verticula or offshoots, which foreshadow the air-sacs of
birds.
The alimentary canal consists of seven parts : the oes-
ophagus, crop, glandular and muscular stomachs, large and
small intestines, and cloaca. The oesophagus extends about
three fifths of the way down the right side of the neck, and
is approximately of the same diameter as the trachea., with
regard tr which, as before mentioned, it lies symmetrically.
It opens into the crop (Or), a thin- walled sac, which fills
the triangular space between the base of the neck and the
keel of the sternum, and forms a large part of the curved
outline of the breast. In the specimen figured, the left half
of the crop has been removed to show the irregular folds
upon the inner surface, the deep lateral pouch and the
three posterior longitudinal folds of one side, which serve
to guide the food onward to the stomach. As shown in
Fig. 459, D, the crop (Cr) ends just to the right of and
above the trachea, in a dorsally-placed, narrow tube, that
reaches to the origin of the bronchi, and there gradually ex-
pands into the glandular stomach, which cannot, however,
be seen in a general dissection, while the heart, lungs, and1
328 ZOOLOGY.
liver are still in situ. The muscular stomach or gizzard
(St) of the main figure is represented very large, being
distended with food ; it is sometimes found much con-
tracted ; it is not sharply separated from the glandular
stomach, the two being in reality only the greatly modified
anterior and posterior divisions of the same dilatation. The
opening of the glandular stomach and the origin of the
small intestine are near together upon the anterior border
of the gizzard. The walls of this last organ are remarkable
for the enormous development of the muscular layers,
especially in the graminivorous birds, under which pigeons
are to be included ; the muscles radiate on each side from
a central tendinous space. The small intestine has nu-
merous coils, in the first of which lies the pancreas (Pan),
very much as in mammals. The large intestine (R) is rel
atively short ; its commencement is marked by two small
diverticula, distinctive of birds.* These appendages are
well developed in some species, as, for instance, the Galli-
nacece, while in the bustard they have been described as
three feet long. Gegenbaur considers the oesophagus, crop,
and stomach to be derived from the fore-gut, the small in-
testine from the mid-gut, and the large intestine from the
hind-gut of the embryo. The cloaca (Cl) is the short and
widened termination of the alimentary canal, and further
receives four ducts, the two ureters ( Ur), and in the male
the two vasa defer entia (Vd), in the fen ale the two ovi-
ducts.
The digestive canal has two glandular appendages, the
pancreas (Pan) and the liver (Li) ; thei former, as in
birds generally, is quite large, whitish, and sends out a pro-
longation, which extends to the spleen ; it has two ducts.
The liver (Li) is very voluminous, dark reddish brown in
color, and forms two lobes, which rest upon the apex of the
heart and the gizzard, and conceal the glandular stomach.
There is no gall-bladder, a somewhat unusual feature among
birds, but there are two bile-ducts, the larger and shorter
* Some snakes have a single diverticulum, as is said to be the case
witb herons.
ANATOMY OF THE PIGEON. 529
opening into the upper part, while the longer duct, after
uniting with that of the pancreas, opens into the lower part
of the duodenum.
The length of the neck in birds is never less than the
height at Avhich the body is carried from the ground ; the
number of vertebnB entering into its formation varies from
9 to 2-1 (swan) ; in the pigeon there are twelve, accompanied
by a corresponding number of spinal nerves, the branches of
which may be observed immediately underneath the skin.
The main mass of the neck is composed of the vertebral col-
umn and muscles, the trachea and oesophagus. On either
side of the base of the neck, in close proximity to the trachea
and carotid artery, is a small oval white body, the thyroid
gland (Tr), at first developed as an evagination of the fore-
gut, but afterward becoming a closed and ductless sac,
which is found in the majority of vertebrates, but the use of
which to the organism is entirely unknown. Above the thy-
roid lie the carotid artery and jugular vein, the main vas-
cular trunks of the head and neck. The right jugular vein
is usually the largest. Along the side of the neck, above
the trachea on the left and the oesophagus on the right, lies
the elongated thymus gland (Tm), drawn somewhat dia-
grammatically ; this gland forms part of the lymphatic sys-
tem, and in minute structure resembles the spleen.
The heart (Ht] lies immediately below the lungs and
against the sternum, with its apex between the two lobes of
the liver pointing oblicpiiely downward and backward ; it
is enclosed in a thin membranous bag, the pericardium,
which is filled with serous fluid and attached to the roots of
the main vascular trunks. To study the heart, it must be
excised, taking the greatest care to leave as much as possible
of the vessels, especially the large veins behind, in connec-
tion with it. Viewed from behind (Fig. 459, C), the heart
is seen to be composed of four chambers, the two anterior
ones, the auricles, being the smaller. The left auricle receives
upon its dorsal side the opening of the united pulmonary
veins (Pv), one from each lung ; the right auricle is larger
than the left, and receives in its upper portion the right vena
cava superior ( Vsd] ; in its lower portion the left vena
530 ZOOLOGY.
cava superior ( Ys), just above which opens the vena cava
inferior ( Ft). The two larger and posterior chambers, the
ventricles, form the apex of the heart, and give off the
arterial trunks. Of the ventricles, the left ( Yen. s] is the
largest, has the thickest walls, and alone extends to the apex
of the heart ; it gives off the aorta, a short trunk which
divides into a right and left branch, from which spring the
carotid arteries for the head and neck, and which continue
as the subclaviaii or auxiliary arteries A and A' for the
wings. From the base of the right branch A arises the
large aorta (Ao), which turns around the bronchus of the
same side, and runs to the front and right of the vertebral
column through the abdomen, forming the descending aorta
which gives off arteries to the intercostal and lumbar regions
and to the viscera, and terminates in A crural branch to each
leg. The right ventricle ( Yen. d) has much thinner walls
than the left ; from it arises the pulmonary aorta (Pet)
which soon branches to each side.
Birds are distinguished from reptiles by having a four-
chambered heart and a single permanent aortic trunk ;
from mammals by the persistence of the right instead of
the left aortic arch to form the aorta. Each auricle com-
municates with the ventricle of the same side ; the con-
necting orifices are furnished with valves. The right
auriculo- ventricular valve is muscular in all birds, Avhile
the left is membranous.
The uro-genital organs lie dorsally in the hinder part of
the body-cavity. The dark reddish brown kidneys (A7)
consist, as in most birds, each of three lobes, the posterior
being the largest ; they lie immediately behind the lungs.
The ureters ( Ur] are slightly curved, whitish tubes, which
pass back from the kidneys and open into the dorsal side of
the cloaca. The testicles (Te) are two large oval whitish
bodies, each situated immediately behind the lung and be-
low the kidney of the same side. The vasa defer entia ( Yd]
arise from the anterior and inner surfaces of the testicles,
have a flexuous course, and, after forming terminal enlarge-
ments, open separately into the cloaca, in front of the
ANATOMY OF THE PIGEON. 531
ureters. In neither sex in birds are the genital ducts pro-
vided with accessory glands.
As usual among birds, the head is approximately top-
shaped. The eyes are very large and much exposed, as be-
comes evident upon dissecting off the skin as in the figure.
The external ear is a mere circular opening, entirely covered
during life by the feathers. The side of the cranium may
be removed so as to expose the brain, with the large smooth
cerebral hemispheres (C), the convoluted cerebellum (Cb),
and the much smaller medulla (McT). To study the brain
satisfactorily, it must be removed from its case. A view of
it from the side is given in Fig. 459, ^4, and a view from
above in the same figure at B. The medulla oblongata
(M) appears as hardly more than the enlarged upper end
of the spinal cord ; upon its dorsal surface there is a trian-
gular depression IV, the fourth ventricle, which is par-
tially concealed by the cerebellum. (Ob), a large mass mark-
ed by transverse ridges and imperfectly divided into three
lobes, thus exhibiting, both in its size and its complication
of structure, a great advance over the reptiles. The corpora
quadrigeminaov bigemina* (Q) project as two large lobes far
out on the sides and down the base of the brain : their posi-
tion and great size are characteristic for the whole class.
The optic thalami, which intervene between the bigemina
and the hemispheres, are relatively small ; they enclose the
third ventricle and have a funnel-shaped downward exten-
sion, to which the pituitary body is attached, as to a stalk.
The cerebral hemispheres (He] form more than half of the
whole brain ; their surfaces are entirely without convolu-
tions, but each hemisphere lias a small projection, the olfac-
tory lobe (01), upon its anterior and inferior extremity.
The cavities of the hemispheres or the lateral ventricles are
very large and extend also into the olfactory lobes. The
greatly thickened inferior walls of the hemispheres are
termed the corpora striata. Birds differ from mammals in
having only a rudimentary for nix and no cotpu* ntlloxion.
The description of the cranial nerves is purposely omitted.
* Also called the optic lobes, middle brain, and mesencephalon.
532 ZOOLOGY.
*
Between the liver and the glandular stomach lies the
small, somewhat elongated, reddish brown spleen.
In birds, as in most vertebrates, several spinal nerves unite
to form a brachial plexus, part of which is shown at B, and
which supplies the wings. Posteriorly, there is also formed
a plexus, the lumbar, for the legs.
The muscles of the limbs are much modified in accordance
with the peculiar locomotion of birds. In connection with
the power of flight, the sternum has a very large keel, to
which are attached the pectoral muscles. The pectoralis
major (Pc) is the most external ; it arises from the outer
half of the keel and is inserted into the humerus, and effects
the downward stroke of the wing. The second pectoral
(pectoralis tertius of some authors and the homologue of
the comparatively insignificant subclavius of human anat-
omy) arises from the inner portion of the keel, runs forward
and outward, and, tapering off, passes through a groove be-
tween the coracoid and sternum, as over a pulley, to be in-
serted into the humerus. The wing is raised by its action.
In the ostrich, etc. (Ratitce), the breast-bone has no keel,
and the disposition of the muscles of the rudimentary wings
therefore differs greatly from that here described. (Minot.)
The ovary may be distinguished by the large incipient eggs
forming the greater part of the mass. The right ovary is
usually undeveloped, but when partly formed, as in some
hawks, the eggs do not mature.
The " white" is deposited around the true egg in the upper
part of the oviduct, while the shell is secreted from glands
emptying into the lower part of the duct. The eggs of
birds are enormous in proportion to those of other verte-
brate animals, except the lizards. The egg of the jEpyorm's,
an extinct bird of Madagascar, is about a third of a metre
(I3£ inches) in length, and as the egg is in reality a cell,
this is the largest cell known. The development of the
chick is better known than that of any other animal. It
travels the same developmental path as other vertebrates in
which an amnion and allantois are formed. About the sixth
day of embryonic life the bird-characters begin to appear,
the wings be^in to differ from the legs, the crop and giz-
ANATOMY OF THE PIGEON.
533
534 ZOOLOGY.
zard are indicated, and the beak begins to develop. By the
ninth or tenth day the feathers originate in sacs in the
skin, these sacs by the eleventh day appearing to the naked
eye as feathers; the claws and scales of the legs and toes are
marked out on the thirteenth day, and by this time the
cartilaginous skeleton is completed, though the deposition
of lime (ossification) begins on the eighth or ninth day by
small deposits of bone in the shoulder-blade and limb-bones ;
centres of ossification appearing in the head by the thir-
teenth day.
" After the sixth day, muscular movements of the embryo
probably begin, but they are slight until the fourteenth day.
when the embryo chick changes its position, lying length-
ways in the egg, with its beak touching the chorion and
shell membrane, where they form the inner wall of the
rapidly increasing air-chamber at the broad end. On the
twentieth day or thereabouts, the beak is thrust through
these membranes, and the bird begins to breathe the air
contained in the chamber. Thereupon the pulmonary cir-
culation becomes functionally active, and at the same time
blood ceases to flow through the umbilical arteries. The
allantois shrivels tip, the umbilicus becomes completely
closed, and the chick, piercing the shell at the broad end
of the egg with repeated blows of its beak, casts off the
dried remains of allantois, amnion, and chorion, and steps
out into the world." (Foster and Balfour.)
Some young birds have, as in turtles and snakes, a tem-
porary horny knob on the upper jaw, used to crack the
shell before hatching. In birds which lay small eggs, with
a comparatively small yolk, the young are brooded in nests
and fed by the parent ; but in the hen and other gallina-
ceous birds, in the wading birds and many swimmers, as
ducks, where the yolk is more abundant, the young main-
tain themselves directly on hatching.
Following the business of reproduction is the process of
moulting the old and weather-beaten feathers. This is often
a critical period in a bird's life, judging by the occasional
mortality among domesticated and pet birds. The annual
moulting begins at the close of the breeding season, though
SONGS OF BIRDS. 535
some birds moult twice and thrice. The quill-feathers (rem-
iges) are usually shed in pairs, but in the ducks (Anatidce)
they are shed at once, so that these birds do not at this
time go on the wing, while the males put off the highly-
colored plumage of the days of their courtship, and as-
sume for several weeks a dull attire. In the ptarmigan
both sexes not only moult after the breeding season is
over into a gray suit, and then don a white winter suit,
but also wear a third dress in the spring. In the northern
hemisphere the males of many birds put on in spring
bright, gay colors. Other parts are also shed ; for example,
the thin, horny crests on the beak of a western pelican (Fcli-
canus erythrorliytichus), after the breeding season, are shed
like the horns from the head of deer. Even the whole
covering of the beak and other horny parts, like those
about the eyes of the puffin, may also be regularly shed.
The variations in the frequency, duration, and completeness
of the process are endless.
As a rule, male birds are larger and have brighter col-
ors, with larger and more showy combs and wattles than
the females, as seen in the domestic cock and hen ; and the
ornamentation is largely confined to the head and the tail,
as seen especially in male humming-birds. Mr. Darwin has
adduced a multitude of examples in his Descent of Man,
Vol. 2. Sometimes, however, both sexes are equally orna-
mented, and in rare cases the female is more highly colored
than the male; she is sometimes also larger, as in most birds
of prey. There is little doubt that the bright colors of male
birds render them more conspicuous and to be more readily
chosen by the females as mates, for in birds, as in higher
animals, the female may show a preference for or antipathy
against certain males. Indeed, as Darwin remarks, when-
ever the sexes of birds differ in beauty, in the power of sing-
ing, or in producing what he calls " instrumental music,"
it is almost invariably the male which excels the female.
The songs of birds are doubtless in part sexual calls or
love-notes, though birds also sing for pleasure. The notes of
birds express their emotions of joy or alarm, and in some
cases at least the notes of birds seem to convey intelligence
536 ZOOLOGY.
of the discovery of food to their young or their mates. They
have an ear for music ; some species, as the mocking-bird,
will imitate the notes of other birds. The songs of birds
can be set to music. Mr. X. Clark has published in the
America ii Naturalist (Vol. 13, p. 21) the songs of a immber
of our birds. The singular antics, dances, mid-air evolu-
tions, struts, and posturings of different birds, are without
doubt the visible signs of emotions which in other birds find
vent in vocal music.
The nesting habits of birds are varied. Many birds, as
the gulls, auks, etc., drop their eggs on bare ground or rocks ;
as extremes in the series are the elaborate nests of the
tailor-bird, and the hanging nest of the Baltimore oriole,
while the woodpecker excavates holes in dead trees. As a
rule, birds build their nests concealed from sight ; in tropi-
cal forests they hang them, in some cases, out of reach of pred-
atory monkeys and reptiles. Birds may change their nesting
habits sufficiently to prove that they have enough reasoning
powers to meet the exigencies of their life. Parasitic birds,
like the cuckoo and cow-birds, lay their eggs by stealth in
the nests of other birds.
The duties of incubation are, as a rule, performed by the
female, but in most Passerine birds and certain species of
other groups, the males divide the work with the females,
and in the ostrich and other Ratitce the labor is mostly per-
formed by the males.
There are probably from 7000 to 8000 species of living
birds; Gray's "Handlist" enumerates 11,162, but many
of these are not good species. Of the whole number, about
700 distinct species or well-marked geographical races in-
habit North America north of Mexico. The geographical
distribution of birds is somewhat complicated by their mi-
grations. While the larger number of species are tropical,
arctic birds are abundant, though most of them are aquatic.
In the United States there are three centres of distribution :
(1) the Atlantic States and Mississippi Valley ; (2) the
Rocky Mountain plateau, and (3) the Pacific coast. The
migrations of birds will be treated of near the close of this
volume.
FOSSIL BIRDS.
537
While in former times existing birds were divided into a
Jarge number of " orders," these are now known to be sub-
divisions of the two sub-classes Ratitce and CarinatcB, and
probably in many cases should be honored only with the rank
of sub-orders. The discovery of the Archceopteryx and of
birds with teeth and biconcave vertebras has essentially mod-
ified prevailing views as to the classification of birds.
Sub-class 1. Saururce. - - The oldest bird, geologically
speaking, is the Archceopteryx (Fig. 460) of the Jurassic
slates of Solenhofen, Germany. This was a bird about the
size of a crow, the tail being 22 cent. (8-9 inches) long, but
longer than the body, supported by many movable vertebrae
Fig. 460.— Restoration of Archrtopteryx macrura.— After Owen, from Nicholson.
and covered with feathers in distichous series, not in the
shape of a fan. The jaw-bones were long, and contained
conical teeth. The head, shoulder girdle, and fore limbs,
with their three digits, were reptilian in form. (Vogt.) In
these respects and in the long tail the creature served as a
connecting link between the reptiles, such as the bird-like
CoMpsognathiis^nd the existing birds. The hind legs and
wings have the ordinary bird structure, though the metacar-
pal bones were not co-ossified ; the foot consisted of three digits.
Sub-class 2. Odontornitlies* — Still other connecting links
between the reptiles and birds has been discovered by Marsh
* Of these the Ichthyornis was probably !he ancestor of the gulls,
and the Hesperornis of the grebes and loons (Parker).
538 ZOOLOGY.
in the upper Cretaceous beds of this country. The remains
of Ichthyornis indicate an aquatic bird about the size of a
pigeon. The reptilian affinities are seen in the vertebrae,
which, unlike those of all other birds, are biconcave, and in
the long, slender jaws, with stout, conical teeth held in
sockets, as in the crocodiles. On the other hand, the wings
were well developed, and the legs were of the ordinary bird
type, the metacarpal bones being co-ossified, while the ster-
num was keeled. In a second member of the group (Hes-
perornis) the teeth were in grooves, the vertebne as in recent
birds, the sternum without a keel, and the wings were rudi-
mentary (Marsh).
Sub-class 3. Ratitce.- — This group, represented by the kiwi-
kiwi, the moa, cassowary, and ostrich, is characterized by
the smooth unkeeled sternum and the short tail ; the wings
are rudimentary* and the hind legs strong, these birds (except
Apteryx') being runners, and either of large or, as in the ex-
tinct forms, of colossal size. The bones are tilled with marrow.
The simplest form is the " kiwi-kiwi," or Apteryx of
New Zealand (Fig. 461), of which there are three or four
species. It is of the size of a hen, with a long slender beak,
the nostrils situated at the end of the upper jaw, while the
body is covered with long hairy feathers. The female lays
only a single large egg, which weighs one quarter as much as
the bird itself, in a hole in the ground. It is a night bird,
hiding by day under trees.
The giant, ostrich-like, extinct birds of New Zealand,
called moa, and represented by several species, chiefly of
the genera Dinornis and Palapteryx (Fig. 461), were sup-
posed to have been contemporaries of the Maoris or natives
of New Zealand. While a fourth toe (hallux) is present in
the Apteryx, the moa-bird has only three toes.
The largest of the moas, Dinornis giganteus of Owen,
stood nearly three metres (9| feet) in height, the tibia or
shin-bone alone measuring nearly a metre (2 feet 10 inches)
in length. These moa birds belong to three genera : Di-
nornis with ten, Palapteryx with three, and Apt-amis with
a single species.
Allied to the moa was a still larger bird, the JEpyornis
t The moa had glenoid cavities, showing that it had wings (Forbes).
^
Fig. 219 —Birds with teeth. Below, two Hesperornis; above is an Ichthyornis.
(Restored.)— From Miss Buckley.
[To face 'page 538.]
CURSORIAL BIRDS.
539
of Madagascar, supposed by some to be the roc
of the Arabian Nights' Tales. Of this colossal bird, remains
of the skull, some vertebras, and a tibia 64 cent, long, have
been found. The single egg discovered is of the capacity of
one hundred and fifty hens' eggs.
To this order belong the three-toed cassowaries of the
East Indies and Australia, and the emeu of Australia ; both
_- """s^BSvf^ai,,, \Jj\iiva5
Fig. 461.— Moa, Palapteryx, with three Kiwi-kiwi birds.— After Hochstetter, from
Tenney's Zoology.
of these birds are about 2 metres (5-7 feet) high. The
South American ostrich (RJiea Americana') with three toes to
each foot, is a smaller bird, standing 1-3 metres high, run-
ning in small herds on the pampas. The two-toed ostrich
(Struthio camelus Linn.), of the deserts of Africa and
Arabia, now reared for the feathers of its wings and tail, so
540
ZOOLOGY.
valuable as articles of commerce, is the largest bird now liv-
ing, being 2-2-7 metres (6-8 feet) high. It can outrun a
horse, and lives in flocks. It lays about thirty large white
eggs in a nest in the sand ; they are covered in the day-
time by the hen or left exposed to the sun, while at night
the male sits over and guards them. In Cape Colony, os-
trich-culture has become an important business : in 1865
Fig. 462.— Great Auk.— From Cones' Key.
there were only eighty individuals on the ostrich farms ; in
1875 there were 32,247 ostriches, either free or in parks
where Lucerne grass is cultivated as food for these useful
birds. The South American ostrich is in Patagonia hunted
for its feathers. During the Eocene Tertiary period a gi-
gantic ostrich-like bird (Diatryma Cope), twice as large as
DIVING BIRDS.
541
an ostrich, lived in Texas and New Mexico, part of a leg-
bone having been found on the San Juan River.
Sub-class 4. Carinatce. — All other living birds belong to
this group ; they are remarkably homogeneous in form
and structure, and the subdivisions may be regarded as
orders. They are characterized by the keeled breast-bone
or sternum — the wings, as a rule, being well developed.
The diving birds (Pygopodes) are eminent as swimmers,
and comprise the penguins, auks, puffins, grebes, and loons.
The penguins are confined to the antarctic regions. They
are large birds, and form a characteristic element in a Pata-
gonian landscape. The bones are solid, not light and hol-
low, as in other birds ; the wings are small, paddle-like,
with scale-like feathers ; on shore they have an awkward
gait. They lay but a single egg, and some species do not
lay their egg on the rocks, but bear it about in a pouch-
like abdominal fold. The penguins, however, differ so
much from the other divers that they are now often ranked
as a separate group of this grade, called Sphenisci.
The guillemots and auks are characteristic arctic birds
ranging from Labrador northward, and have great powers
of flight. The gare fowl, or great
auk (Alca impennis, Fig. 462), is
nearly or quite extinct, being un-
til lately confined to one or two
inaccessible islets near Iceland,
where it has been extinct since
1844, and to Labrador, though
formerly it ranged from Cape
Cod northward, a few survivors
having lived on the Funks, an
islet on the eastern coast of New-
foundland, within perhaps thirty
years.
The loons are well known for
,-, • i • n -i • Tenney's Zoology.
their large size and quickness in
diving. They are migratory, laying two or three eggs in
rushes near the water's edge.
The petrels, gulls, and terns (Fig. 463, roseate tern) rep-
rig. 463.— Roxeate Tern.— From
542
ZOOLOGY.
resent the group of long-winged swimmers (Longipennes).
They have long, slender, compressed bills, long, sharp wings,
immense powers of flight, and lay their eggs in rude nests
on rocks or upon the ground. The most notable member
of the group is the albatross (Diomedca c:rulaus} of the South-
ern hemisphere. Its wings expand more than three metres
(nearly ten feet). It lays a single egg 12 cm. long, and
spends most of its life on the ocean far away from laud.
The sooty albatross (D. fuliyinosu Lawrence, Fig. 464), is
occasionally seen on our coast.
Fig. 464. — Sooty Albatross. — From Tenney's Zoology.
These birds are succeeded in the ascending series by the
tropic-bird, frigate or man-of-war bird, the darter or snake-
bird, the cormorants, pelicans, and gunnets (Steganopodes),
in which all four toes are fully webbed, the web reaching to
the tips of the toes. The body, especially in the pelicans and
gannefcs, is buoyed up more than in other birds by a large
number of much subdivided air-cells under the subcutane-
ous areolar tissue of the body.
The pelican is remarkable for the large, loose pouch on
the under jaw, capable of holding several quarts, or several
G BIRDS.
543
hundred small fishes. In the East Indies, pelicans are
tamed and used by the natives in fishing, as is the cormorant
in China, while in early times it was in England.
The ducks and geese (Lamellirostres] have usually broad
bills furnished with lamellate, teeth-like projections. The
feet are palmated, adapted for swimming rapidly. In the
mergansers the bill is narrow and more strongly toothed.
The eider duck (Sommateria mollissima) which breeds from
Labrador around northward to Scotland, plucks its down
from its breast, building with it a large warm nest under
low bushes on the sea-coast, where it lays three or four pale
Fig. 465.— Summer Duck. -From TYnnsy's Zoology.
dull green eggs. The canvas-back (Fiiligula valMsneria)
feeds, as its specific name implies, on the wild celery ( Val-
lisneria) on the middle Atlantic coast in winter, whence it
derives its delicious flavor. The summer duck (Aixsponsa,
Fig. 465) breeds in trees. The original source of our do-
mestic duck is the mallard, or Anas boschas. It is known
to cross with various other species. Upward of fifty kinds
of hybrid ducks arc recorded, some of which have proved
to be fertile (Coues). The black duck (Anas obscura) is
abundant on the shores of Northeastern America, and is fre-
544
ZOOLOGY.
Fig. 466. — Carolina Rail. — From
Tenney's Zoology.
quently brought iiito the market. The wild goose (Brantn
Canadensis) breeds in the North-
ern United States and in British
America. While it usually breeds
on the shores of rivers, it has
been known in Colorado and
Montana to nest in trees. Allied
to it is the barnacle goose of
Europe (Brant a leucopsis), which
very rarely occurs in this coun-
try. The swans are characterized
by their long necks, the trachea
or wind-pipe being remarkably long, especially in the trum-
peter swan, where it enters a cavity in the breast-bone,
makes a turn and enters the lungs,
after forming a large coil.
To this group, or next to it, also
belong the flamingoes, the American
flamingo (Phcenicopterus ruler} occur-
ring on the Florida and Gulf coast.
Its feathers are scarlet, its bill yellow,
large and thick, while the legs and
neck are of great length. It connects
the swimming with the wading birds.
The foregoing group forms a division
called the Natatores or swimming
birds. We now come to the Oralla-
tores or wading birds, which have long,
naked legs, and therefore long necks,
with usually remarkably long bills.
They are divided into cranes, rails, etc.
(Alectorides), the herons and their
allies (Herodiones), and the shore-birds,
snipes and plovers, or Limicolm.
The cranes, together with rails (Por-
sana Carolina, Fig. 466) sometimes
have lobate feet, the toes are often
long, and in some forms, such as the
coots and gallinules, there is an approach to the ducks.
Fig. 467.— The •' Giant " ol
Mauritius.— After Schlegei.
WADING BIRDS.
545
Allied to the gallinules is the " giant " or Gallmula (Le-
guatia) gigantea of Schlegel (Fig. 467), which formerly lived
in the Mascarene Islands, having been observed as late as
3 694. It stood two metres (over six feet) high. With it was
associated a large blue galli-
nule — Porphyrio (Notorni* .')
ccerulescens Selys — which was
last seen on the Isle Bourbon
between 1669 and 1672. It
was incapable of flight, but
ran with exceeding swiftness.
The cranes are of great
stature, the legs and neck very
Fig. 468.— Long-billed curlew.— From loiiff, with the head sometimes
Coues' Key. • i *, j w±i ±\
curiously tinted. With the
true herons are associated the night herons and the bitterns
of the United States, the boat-billed heron of Central Am-
erica, and the odd Balceniceps rex of Africa, which has an
enormous head and broad, large bill. The herons are suc-
ceeded by the singular spoon-bills represented by the rose-
ate spoon-bill, and which, with
the wood Ibis and other species
of this group, adorn the swamps
and bayous of the South Atlan-
tic and Gulf States.
The shore-birds, or the cur-
lews (Numenius longirostris,
Fig. 468), plover, sandpipes,
peeps, snipes (Gallinago Wil-
xuitii, Fig. 469), woodcock, and
stilt (Himantopus nigricollis,
Fig. 470), are long-legged, long-
billed birds, going in flocks by
the Seashore Or river-banks, Fig. 469.— American Snipe.— From
sometimes living inland on low Tenneys zoology,
plains ; they are not, generally speaking, nest-builders, the
eggs being laid in rude nests or hollows in the ground.
They feed on worms, insects, and snails, either picking
them up from the surface or boring for them in the mud or
-
546
ZOOLOGY.
sand, or forcing the vermian food out of their holes by
stamping on the ground.
Connecting in some degree
the waders and gallinaceous
fowl are the bustards of the
Old World, certain strange
exotic birds, especially the
horned screamers represented
by a very rare bird, the Pala-
medea cor nut a Linn., which
has sharp horns on the wings.
The form of the gallina-
ceous birds, formerly called
Rasores, from their peculiar
habit of scratching the ground
for food, is readily recalled
Fig. 4TO.-stiit.lprom Tenney's Zoology. bJ a simple enumeration of
the partridge, Oreortyx (0.
pictus, Fig. 471), quail (Ortyx), ptarmigan (Lagopus, Fig.
472), pinnated grouse or prairie hen (Cupidonia cupido],
sage-cock, Canada grouse
or spruce partridge (Te-
trao), and wild turkey
(Meleagris), as well as the
exotic forms, the pheasant
of the Old "World, the use-
ful hen or barn-yard fowl,
which is a descendant of
Gallus Bankiva Tem-
minck, of India. These are
allied to the argus-pheasant
and the peacock, the latter
rivalling the humming-
birds in its gorgeous plum-
age. The guinea-hen is
an African bird. To this
•. , ,, . Fin. 471.— Plumed Partridge.— From Ten-
group belongs the curious ney's zoology.
mound-bird (Megapodius),
of Australia and New Guinea. It heaps up a large mass of
0e-—
coe-
ov — >
FIG. 459a.— Digestive canal of a seed- FIG. 471a.— Hoasin or Hoatzin. OpisthO'
eating bird, a?, oesophagus, cr, comus cristatus.
crop; pv, proven triculus; gz, giz-
zard; /, liver; p, pancreas; cce,
caecum; si, small intestine; Zi,
large intestine; ov, oviduct; u,
ureter; cl, cloaca.
FIG. 471b. — Wing of Opisthocomus, whpn the embryo was about half ripe for
hatching, showing the claw on the first digit, rig1 ; on the second digit, dg*; th«
rudimentary claw on the third digit, dc/3', and the rudiment of a fourth digit, dy*~,
h, humerus; r, radius; u, ulna; re, radiale; tie, ulnare; i, intermedium; c, cen-
trale; dc1, dc2, distal carpals.— After W. K. Parker.
[To face p. 546.]
GALLINACEOUS BIRDS.
54?
rubbish, forming a hot-bed, in which its eggs aw left to
hatch. The megapods, together with the American guans
and curassows (Cracidoe), form a sort of passage from tho
gallinaceous to the columbine birds. One of the most puz-
zling forms for the systematic ornithologist to deal with is
the hoasin of Guiana (Opisthocomus cristatus Illiger). In
this bird the keel of the breast-bone is
cut away in front, the wish-bone unites
with the coracoid bones, and also with
the manubrium of the breast-bone. It
was an archaic gallinaceous bird.*
In the tinamous of Central and South
America the tail-feathers are, in some
cases, entirely wanting, and the breast-
bone and skull-bones have some anom-
alous features. Most all gallinaceous
birds have plump
bodies, with short
beaks and small
rounded wings, not
being good fliers.
In some of their
cranial characters
they are so peculiar
that Huxley makes
them one of his
primary divisions
of CarinatdB.
We now come to
birds of a higher
° Fig. 472.— White-tailed Ptarmigan (Lago/ms leucurus),
type, in Which the in (upper figure) summer and (lower figure) winter
1 -, , » plumage. — From Hayden's Survey.
Knee and part ol
the thigh are free from the body, the leg being usually
feathered down to the tibio-tarsal joint ; the toes are usually
on the same level, being fitted for grasping or perching.
The doves are rapid fliers, but a notable exception is seen
in their extinct ally the Dodo (Didus ineptus Linn.) of
Mauritius, which became extinct on the island of Mauritius
in the seventeenth century, while the solitaire, Didus (Pe-
* The young have wings with two claws, a third rudimentary claw,
and two rudiments of a fourth digit ; its scapula is batrachiau, its
three clavicles lizard-like (Parker), see Fig. 471/j.
5-±3 ZOOLOGY.
zopliaps) solitarius Schlegel, inhabited the island of Ro-
driguez, having been exterminated about the same date
(1681). These were clumsy, defenceless birds, incapable of
flight, and were destroyed by the domestic animals which
accompanied the Portuguese voyagers to the Mascarene
Islands. The doves and their allies now commonly form a
group, called Columbce.
The birds of prey (Raptores), comprising the vultures,
buzzards, falcons, hawks, eagles, and nocturnal owls, have
a hooked and cered beak — i.e., with a waxy, dense mem-
brane situated at the base of the upper mandible. The
claws are large and sharp. The raptorial birds live either on
birds and mammals, or fish, reptiles, batrachians, and insects.
Of the vultures, the most notable for size is the condor of
the Andes (Sarcorhampusgryphus), which has great powers
of flight, its wings expanding nearly three metres (nine
feet).
The carrion crow and turkey buzzard (Cathartes atratu*
and C< aura Illig.) are useful as scavengers, especially the
former, which is partly domesticated in southern cities and
towns ; they nest on the ground or in stumps, and are more
or less social. The bald-headed eagle (Haliattu* leucocepha-
lus) is dark-brown when young, and 1 ef >re shedding its
youthful plumage is larger than the white-headed adult. It
nests on inaccessible rocky points ; is the sworn enemy of
the fish-hawk, and, like it, fond of fish, often wresting its
living food from the talons of the hawk. This species is the
emblem of our country. The osprey or fish-hawk (Pandion
haliaetus) is two-thirds of a metre long, nests in tall trees,
and is migratory. Among the hawks, the most notable are
the falcons or hunting hawks, used during the Middle Ages
in hunting the hare, etc. ; in nature they chase their prey
and kill it immediately, devouring it, and rejecting the
bones and hair of the partly digested food in a ball from the
mouth.
The owl is a bird of the night ; its flight is noiseless, ow-
ing to its soft plumage, the feathers having no after-shaft.
It has large eyes and a hooked bill, giving the bird of Mi-
nerva an air of consummate wisdom. Owls capture living
EIRDS OF PREY. 549
mice and other small nocturnal animals, ejecting from the
mouth a ball of the indigestible portions of their meal.
The little burrowing owl of the western plains (Spheotyto
cunicularia, var. hypogcea) consorts with the prairie dogs and
rattlesnakes, nesting in the holes when deserted. Their
rusty, dull hues assimilate them with the color of the soil
they inhabit. Our largest owl is the great gray owl (Syr-
nium cinereum) ; it is nearly f metre (2| feet) in length, and
Fig. 473. — Carolina Parroquet.— From Tenney's Zoology.
is an inhabitant of Arctic America. A visitor in winter
from the Arctic regions is the snowy owl (Nyctea nivea}.
which is nearly f m., or two feet long. The great horned
owl (Bubo Virginianus) is about the same size as the snowy
owl, but has two conspicuous ear-tufts, adding to its height:
and its general impressiveness as a bird of more than ordi-
nary sagacity.
Of more intelligence and gifted with the power of speech
550
ZOOLOGY.
are the parrots (Psittaci). The tongue is large, soft, and
remarkably mobile, us the muscles at the base are more dis-
tinctly developed than in other birds, and the lower larynx
is complicated with three pairs of muscles ; hence these
birds are wonderful mimickers of the human voice, imi-
tating the laughter or crying of babies, and repeating brief
sentences, while some sing. In proportion to their capacity
for talking, parrots command a very
high market price. Their toes are in
pairs, the bill is cered and very stout,
adapted for cracking hard nuts. The
wish-bone is sometimes rudimentary,
and the sternum entire, not notched.
Parrots are monogamous, like the hawks,
and nest in rocks or hollow trees. Our
only parrot is the Carolina parroqiiet
(Conurus Carolinensis Kuhl, Fig. 473),
which is common in Florida. It for-
merly extended to the Great Lakes and
to New York, but is nearly exterminated.
About three hundred and fifty species
are scattered through tropical countries,
Australia and South America being es-
pecially favored by these gorgeous birds.
The ground parrot of New Zealand does
not fly, all the others being good fliers.
Fig. 474— skuii of Ge- Parrots live to the age of eighty years.
cinus viridis L., showing m, r> • • 11
the asymmetrical position lllO riCCtriCB, a Somewhat miSCelhl-
neous group of birds, comprising the
tbo Piir-kofis nnfl >illip<?
Jis, clX ^S,
and the swifts and humming-birds, con-
nect the preceding groups with the Pas-
serine or singing birds. From the latter the Picarice com-
monly differ in the form of the sternum, in the less
developed vocal apparatus, there being no more than three
pairs of separate muscles, so that the birds are not musical ;
as well as in the nature of the toes and wing and tail
feathers.
The woodpeckers usually have pointed, stiff tail-feathers,
through the right nasal ,vnn,l npplc
opening to the end of the wo LK
PERCHING BIRDS.
551
and the bill is straight and strong. The tongue is long,
flat, horny, and barbed at the end, and can be usually darted
out with great force, so that the bird can make holes in the
bark of trees and draw out the larvae of insects boring under
the bark ; in tnis way these birds render us signal service.
The tongue, as in all vertebrates, is supported by the hyoid
apparatus, especially by two cartilaginous appendages to the
hyoid bone, called " the horns. " These in the woodpeckers,
when fully developed, are curved into wide arches, each
horn making a loop down the neck, and thence bending
upward, sliding around the
skull, and even down on the
forehead. Through a peculiar
muscular arrangement of the
sheaths in which the horns slide,
they can be retracted down on
the occiput, and work as springs
on the base of the tongue, foi'C-
ing it out with great velocity.
Lindahl has noticed in some
European Avoodpeckers an asym-
metric arrangement of the horns
as indicated in Fig. 474.
The second group, the Cuculi,
comprise such forms as horn-
bills, kingfishers, toucans, and
cuckoos. These are succeeded by
the Cypseli, embracing the hum-
ming-birds, goatsuckers, swifts,
nighthawk (Chordeiles Viryinianus, Fig. 475), and whip-
poorwill, which have long pointed wings, great powers
of flight, small weak feet, and, in the humming-birds,
long slender bills. The latter are peculiar to America,
being chiefly confined to South and Central America, only
one species (Trochilns cohibris Linn.) extending into the
Eastern United States, though a dozen or more species oc-
cur in the Western United States, and very many in Mexico.
The highest group of birds, those which sing, are the
Passeres or perchers. In these birds the feet are adapted for
. — From
552
ZOOLOGY.
grasping, one toe projecting backward, while the bill is horny,
usually sharp — conical, according to Coues. Various as are
the shape of the wings, they agree in having the great row
of coverts not longer than half the secondaries ; the pri-
maries cither nine or ten in number, and the secondaries
more than six. The tail, extremely variable in shape, has
twelve rectrices (with certain anomalous exceptions). There
is but one common carotid artery, and the sternum is very
uniform in shape. Their high physical irritability is co-
ordinate with the rapidity of their respiration and circula-
tion ; they consume the most oxygen and live the fastest
of all birds (Coues).
There are two groups of
Passerine birds, differing in
the structure of the lower
larynx; in the first (Clnnia-
tores) the vocal organs are
more or less rudimentary,
* *
the species not being singers,
while in the second and
higher division (Oscines) the
lower larynx is so developed
that most of the species ex-
cel as singers. In the sing-
ing birds the vocal apparatus
(*>/rinx), or lower larynx, is
situated next to the lungs at
the end of the windpipe, with a muscular apparatus formed
of five or six pairs of muscles, whose action varies the
tension of the vocal cords and narrows or widens the
glottides, which are elastic folds of the mucous membrane.
A fold of the tympanal membrane of the syrinx, called the
menibrana semilunaris, projects inward.
Representatives of the Clamatores are the Acadian fly-
catcher, the wood pewee, the pewee or phoabe-bird, and the
kingbird (Fig. 476). The last, sometimes called the bee-
martin, Coues tells us, destroys a thousand noxious insects
for every bee it eats. The lyre-bird (Fig. 477) is also a
member of this group.
Fig. 476. — Kingbird. — From Tenney's
Zoology.
81NUINU BIRDS.
553
This bird, with tail feathers so strikingly developed (Fig.
477), is so peculiar among higher Passeres that it has been
proposed to separate it, with certain probable allies, from
all the rest.
The Oscines are represented by a host of species. These
birds stand at the head of their class ; and as they are mostly
Fig. 477.— The Lyre-bird of Australia ( Memira euperba).
of small size, it may be said of them that they excel in qual-
ity, not quantity ; most of them sing, being highly wrought,
exquisite winged gems. Among the most notable are the
lays, including the magpie of the Rocky Mountains (Fig.
554
ZOOLOGY,
478), the crow, and blackbird, so useful a bird, notwith-
standing its mischievous propensities ; the oriole, whose
. 478.— Magpie.— From Teimey's Zoology.
Fig. 479.— Butcher-bird.— From Tenney's Zoology.
hanging nest, brilliant colors, and lively song render it one
of our most interesting birds ; while the reed-bird of the
SINGING BIRDS.
555
Fig. 4SO. — Warbling VTireo.— From
Tenuey's Zoology.
South or bobolink, as it is called in the North, wakes up the
meadows with ins lively notes. The finches with their
conical beaks are succeeded, in the ascending series, by the
English sparrow, a bird useful in the cities in destroying
canker-worms, but a nuisance in
the country. Our song-sparrow
(Melospiza fasciata) is widely
distributed, and everywhere
commends itself by its pleasant
notes. Quite opposed in its
habits is the butcher-bird or
shrike (Fig. 479), a quarrelsome,
rapacious bird, which feeds on
insects or small mammals, often
impaling them on thorns or sharp
twigs, and leaving them there. The group of vireos or
greenlets (Fig. 480) are peculiar to America ; their bills are
hooked, with a notch at base ; they are warblers. The wax-
wing (Ampelis cedrorum, Fig. 481) is the type of an allied
family. The swallows and
martins are interesting from
the change made in the nest-
ing habits of the more com-
mon species which rear their
young in artificial nests or
in barns, or under the eaves
of buildings.
Another group character-
istic of North America is
the warblers, Dendrceca (D.
virens, Fig. 482) being the
representative genus. On
the other hand, the larks
are an Old World assemblage Fig. 481.— Carolina Waxwing.— From
. ° Coues' Key.
or birds, but tew species
occurring in this country, while the wrens (Fig. 483) are
mostly restricted to America.
The smallest bird in the United States, except the hum-
jning-bird, is the gold-crested kinglet (Regulus satrapa
556
ZOOLOGY.
Liechtenstein), which is less than 9 cm. (3f inches) in length.
Lastly come the bluebird, the melodious thrushes, and the
Fig. 482.— Black-throated Green Warbler.— From Cones' Key.
ig. 483.— Winter Wren.— Prom Cones' Key.
mocking-bird, while at the head of the class in this country-
stands the robin (Turdus migrator ius Linn.).
CLASSIFICATION OF BIRDS. 557
CLASS VII. — AVES.
Feathered Vertebrates; jaws encased in horny beaks in existing forms :
the fore-limbs forming wings; warm-blooded; heart four-chambered ;
lungs with accessory air-sacs ; the bones dense, hollow ; oviparous ; egg*
very large, covered by a calcareous shell.
Sub-class 1. Saurum.— Tail as long as the body; head and fore limbs
reptilian; with feathers, scales, and teeth. (Archaeopteryx.)
Sub-class 2. Odontornithes.*— Vertebrae biconcave, or as usual ; jaws
slender, with teeth implanted in sockets or in grooves; mefra-
carpals co-ossified; sternum keeled or uukeeled ; wings well
developed (Ichthyoruis) or rudimentary (Hesperornis).
Sub-class 3. liatitd1. — Sternum smooth ; wings rudimentary. (Struthio).
Sub-class 4. Carinatce. — Sternum keeled ; wings well developed. (Tur-
clus.
Laboratory Work. — The student should prepare a skeleton of a hen or
any other bird, and compare it, and especially the skull and limbs, with
those of a reptile and a mammal. In dissecting a pigeon or fowl, at-
tention should be given to those points previously indicated in which
birds diverge from reptiles on the one hand and mammals on the other.
CLASS IX. — MAMMALIA (Mammal*).
General Characters of Mammals.— In the mammals, which
begin with the duck-bill, a creature in some respects re-
minding us of the birds, and end with man, we observe,
as compared with birds, an increased complexity of struc-
ture ; and in the nature of the work done by the different
organs, we may see a constant tendency to a development
of parts headward, so that the head becomes large in pro-
portion to the body, the brain increases in size, and the fore-
limbs finally become hands, ministering to the intellectual
wants of the animal. Also, as we ascend the series, the body,
from being horizontal, with limbs adapted for walking on all
fours, becomes finally in the apes semi-erect, in man wholly so.
The greatest step in advance over the reptiles and birds
* It is doubtful if this is a natural group. Ichthyornis was probably
an archaic or generalized gull with teeth ; and the wingless Hesperornis
was the ancestor of the grebes and loons. (See also W. K. Parker.)
558 ZOOLOGY.
is in the nature of the limbs, the structure of the head, the
organs of special sense, together with the increased com-
plexity of the teeth, and the size and complicated structure
of the brain, particularly of the cerebrum and cerebellum.
The more important (diagnostic) features of the mammals
are the articulation of the lower jaw directly to the skull,
the quadrate bone becoming the zygomatic process of the
squamosal ; there are two occipital condyles; the teeth are dif-
ferentiated into incisors, canines, premolars, and molars; the
body is covered with hair.* The body-cavity is divided into
two compartments (thorax and abdomen) by a large muscle,
the diaphragm, so that the lungs are separated from the ab-
dominal viscera. From the four-chambered heart the
single aorta is reflected over the left bronchus ; the blood is
warm, with non-nucleated corpuscles ; the circulation is com-
plete, the blood being entirely received by the right auricle
and transmitted by the right ventricle to the lungs for aera-
tion, whence it is after ,vard returned by the left ventricle
through the system. The brain is much larger than in
birds, the cerebral hemispheres forming the bulk of the
train, and gradually, in different members of the ascending
series, overarching and finally concealing from above the
cerebellum. The cerebral hemispheres are more or less
connected (and in nearly inverse ratio) by an anterior com-
missure and a superior transverse commissure (corpus callo-
sum], the latter more or less roofing in the lateral ventricles
(Gill). Mammals are viviparous, the embryo developing
from a minute egg, and the young after birth are fed by
the mother with milk secreted in the mamma? or mammary
glands ; hence the name of the class, Mammalia.
Eeturning to the skeleton, which we may examine more
in detail : the skull, as a brain-box, is much larger than in
the reptiles and birds. The brain-cavity of Coryphodon
and other extinct Tertiary mammals was exceedingly small,
scarcely larger in proportion than in reptiles, and there is a
progressive increase in size of the cavity of the skull in the
more specialized descendants of this early Tertiary type, as
seen in that of the horse, when compared with its Eocene
progenitors. There is also a decided increase in the brain-
* The incus and malleus bones are also diagnostic of mammals.
STRUCTURE GF MAMMALS. 559
box of the monkey as compared with that of the lemur, and
of apes as compared with monkeys, while in man the brain
capacity is twice that of the highest apes.
The different regions of the vertebral column are better
defined than in the birds and reptiles ; this is seen in the
cervical vertebrae, the number of which is usually seven.
The exceptions to this rule are few, there being six in one
sloth (Cholcepus), eight or nine in another sloth (Bradypus),
and six in the American manatee. Behind the cervical is
the dorsal region, consisting of from ten to twenty-four,
usually thirteen, vertebras, and the lumbar region, which is
composed of from two to nine, usually six or seven, vertebras,
and is marked off by the absence of movable ribs. The
Fig. 484.— Skull of the Lion.— After Owen.
shoulder-girdle is not solidly united to the dorsal vertebrae,
but loosely attached by mv les and tendons. The pelvis
—i.e., that portion called the ilium — connects with a single,
sometimes two, rarely three, vertebras of the sacral region,
and the union of these vertebras with one or more caudal
vertebras forms an assemblage of consolidated vertebras, called
the OK sacrum, which in the sloths, or Edentates, comprises
eight or nine vertebras. The number of caudal vertebras-
in the monkeys may amount to thirty, in the long-tailed
manis (Fig. 501) to forty,* while in other mammals there
may be less than this number, there being four retained by
man and the larger apes, while in some bats there are only
three. The coracoid bone is free in Mouotremes.
* ID Microgale longicauda there are 48 ; in Manis macrura, 49.
5(30
ZOOLOGY.
But it is in the limbs, and especially the feet, of mammals
that the skeleton varies most, and always in accordance with
the different habits of the creature. The limbs of mammals
differ from those of the lower vertebrates in the fact stated
by Gegenbaur, that the planes in which the angles of the
limbs of either side are set are parallel to the vertical me-
dian plane of the body, thus giving greater independence to
the limbs, which now become supports for the body, since
they raise it from the ground. Beside this, the angles be-
tween the equivalent portions in each limb do not agree
with each other, as in the rep-
tiles, but point in an opposite
direction in the case of the fore
and hind limbs respectively
(Gegenbaur). As we ascend in
the mammalian series, the limbs,
particularly the fore-limbs, are
variously modified. The limbs
of whales are paddle-like, though
the bones of the limbs are homo-
logous with those of other mam-
mals. The feet of the seal are
webbed, forming nippers ; it can-
not support itself on its limbs,
but the fore-feet have consider-
able motion of the radius on the
ulna. In the dog the fore-limbs
have but little motion of the
Fie. 485— Arm of the Thumbiess radius on the ulna, but the cats
Monkey (Ateles). . , .
(Felidce) have more of this rotary
motion, enabling them to grasp with the fore-foot. This
rotary motion of the fore-arm, involving the modification
of the fore-foot into a hand, is seen in the thumblcss mon-
keys (Fig. 485), and in those provided with a thumb, in the
gorilla, and especially in man. The extreme of specializa-
tion of all four limbs is seen in the horse, which has but
one digit, and walks on its single toe-nail. In the bat, the
ulna and radius are fused together as one bone, and the
last three fingers are greatly lengthened. The liberation of
HAIR AND HORNS 0* MAMMALS.
5C1
the limb from the body becomes more marked as we ap-
proach man. In the seal, only the wrist protrudes from
the skin, the limb of the otter slightly more ; the horse's
leg does not protrude beyond the elbow, that of the monkey
projects two thirds of its length, while in man the limbs
become wholly free from the trunk (Wyman).
The hairs originate in minute sacs which extend from the
epidermis into the cutis ; from the bottom of this inpushing
of the epidermis grows up the shaft of the hair, which is
Fig. 486. —Diagram of the development of the nipple ; vertical section, ff, periphery
of the glandular area (b) ; gl, glands. A, form of the gland in Echidna ; B, its form
in most mammals ; C, its form in some ungulates, as the cow, mare, etc. — After
Gegenbaur.
surrounded at the base by the cellular wall of the hair-sac
forming the root-sheaths. The spines of the porcupine, the
scales of the Manis, of the armadillo, of the tail of the rat,
are modified hairs, all developing in the same manner.
Many mammals, especially the ruminants, as the deer, ox,
rhinoceros, etc., are armed with horns. There are two
kinds, those which are solid and bony, as in the deer ; while
in others, as the antelopes, sheep, goats, and oxen, the horns
are hollow, the horny case enveloping a bony core ; hence
562
ZOOLOO r.
they are sometimes called Cavicorns. In most horned
mammals, the horns are persistent ; in the deer they are
dropped annually ; in the prong-horned antelope (Fig. 487)
the horns are also shed annually. The giraffe's horns are hairy.
The mammary glands are modifications of the tegument-
ary glands which are found in all vertebrates except fishes.
In the duckbill and spiny ant-eater (Echidna}, these glands
retain their simple elementary nature. In all others nip-
ples are developed (Fig. 486). They correspond in general
to the number of young in a litter.
The dentition needs careful study in connection with the
Fig. 488.— Skull of Ant-eater.— After Owen.
Fig. 487. — Hollow
horn of the Prong
horned Antelope.
Fig. 489.— Skull of a Porcupine.— After Owen.
fossil remains of mammals, as the different orders are char-
acterized in great part by the differences in the form and
number of the teeth, which are intimately correlated with
the structure of the digestive organs and the nature of the
limbs ; thus while vertebrae are useful in identifying or re-
storing fossil reptiles, the teeth are especially serviceable in
classifying fossil mammals. Some existing forms are en-
tirely toothless, as the duckbill, where the teeth are repre-
sented by horny plates, and the ant-eater (Fig. 488). While
the sloths have no incisors, these are present and very
large in the rodents, but the canines are absent (Fig. 489).
THE EAR OF MAMMALS.
563
In the elephant the upper incisors form thb tusks, the cor-
responding teeth of the lower jaw being absent. In many
teeth, as those of the deer (Fig. 490), the
crown of the molars is quite convex, with
crescent-shaped enamel areas. The canines
are large and sabre-shaped in the cat fam-
ily, while in the pigs, especially the baby-
roussa of Malaysia, the upper pair curve
upward and backward to the forehead.
The premolars and molars have two or
three roots or fangs ; in none of the lower *oxvh]ghtho enamel
vertebrates do the teeth have more than Crescents. -After
one root.
The organs of sense are much developed, especially the
ear. The quadrate bone of the reptiles and birds, which is
Fig. 490.— Crown of
Fig. 401.— Diagram of the labyrinth of the ear in J, the fish. //. the bird, and ///. a
mammal. U, utriculus; 8, sacculus: U8, utriculus and sacculus; Cr, caniilis n-unicns ;
R, recessus labyrinth!; UC, commencement of the cochlea, C . L. lagi'iia: A", circal
sac at the apex; C, ccecal sac of the vestibuluni of the cochlear canal.— After Wai-
deyer, from Gegenbaur.
large, external, and suspends the lower jaw to the skull,
now becomes much changed, and forms the zygomatic
process of the squamosal bone. The labyrinth of the ear,
largest in fishes, is smallest in mammals. The cochlea
564 ZOOLOGY.
(Fig. 491, C) is greatly developed in the mammalia, while
the external ear now appears. This is a prolongation of
the edges of the first branchial cleft of the embryo. There
is, however, no external ear in the Monotremes (duckbill).
It is also absent in whales, the Siren ians or sea-cows, in
most seals, and is very small in the eared seals (Otaria).
The eye of mammals is not essentially different from that of
the lower vertebrates.
The general anatomy of the soft parts of a mammal may
be studied by dissecting a cat, with the aid of the following
description and drawings prepared by Dr. C. S. Minot :
Fig. 492 illustrates the general anatomy of the cat ; the
skin and right half of the body-wall have been removed.
The body-cavity is divided into an anterior and posterior
division by a transverse arched partition, the diaphragm (D),
composed of a thicker peripheral muscular portion and a
thinner central tendmo^^s part. Through the latter pass
the great blood-vessels and the oesophagus. The anteriof
chamber is the thorax or pleura! cavity, and contains
the respiratory organs and heart. To show these, the
right lung has been removed. The heart (Ht) was en-
closed in the thin-walled pericardial sac, which has been
cut away. The great systemic veins enter from behind — -
i.e., dorsally ; from below the vena cava inferior, passing
up through the diaphragm and uniting opposite the heart
with the large vein, cava superior, V, from above, the two
emptying into the right auricle. The oesophagus (Oe)
overlies the trachea (Tr). The aorta arises from the heart,
and, curving upward and backward, runs to the left of
both trachea and oesophagus, as indicated by the dotted
lines, and continues its backward course just below the vena
azygos, into the abdomen. The trachea gives off a bronchus
to each lung (Lit}. The lungs are sacculated elastic organs,
with no main central cavity. They are separated dorsally by
a thin median vertical membrane (M), the mediastinum, the
equivalent of the mesentery in the abdomen. Lying on the
side of the vertebral column can be seen part of one of the
two chains of sympathetic nervous ganglia (S).
ANATOMY OF THE CAT. 500
The abdominal cavity contains the principal reproduc-
tive, excretory, and digestive organs. The oesophagus ter-
minates in the stomach almost immediately below the dia-
phragm. The stomach (Si) occupies a transverse position,
its larger (cardiac) end, which receives the oesophagus, lying
on the left, the smaller (pyloric) end on the right. The
pylorus has a sphincter muscle which can completely close
the orifice. The stomach is followed by the long intestines
(In), most of which have been removed, leaving a short
piece in front. The posterior portion of the intestine is
somewhat dilated, is called the colon, and passes into
the wide terminal rectum (Rcc). The whole abdominal
portion of the intestinal canal is suspended from the me-
dian dorsal line by a thin membrane, the mesentery, which
forms several folds, the most striking of which is the omen-
turn or grand epiploon (Om.). This fold, when in situ,
hangs down from the stomach like an apron, covering over
the intestines ventrally. Upon opening the walls of the
abdomen, it is the first structure met with. It usually con-
tains a great deal of fat. Its principal function is supposed
to be to prevent the loss of heat. The omenturn is present in
all mammals, but is least developed in Cetaceans, being most
prominent in Carnivora and ruminants. Connected with
the intestine are two glands, the liver (Li) and pancreas.
The liver is large and lies directly underneath the diaphragm.
The elongated light-colored pancreas lies alongside the front
end of the intestine (In), or so-called duodenum ; in its
microscopic structure it resembles the salivary glands. The
spleen is closely connected with the stomach, and is of an
elongated shape, as in the majority of the Mammalia >/x>i/<>-
The kidneys (Ki) are large and oval, and lie on either
side of the vertebral column ; the aorta passes between
them, giving off a renal branch to eacli gland. A deli-
cate ureter ( Urt) passes from each kidney obliquely across
the rectum to the large flask-shaped bladder (Bl). A
urethra ( Ur) arises from the bladder posteriorly and
566 ZOOLOGY.
opens in the female immediately below the anus, but in the
male enters the penis.
The ovary (Ov) is small and is placed near the open end
of the oviduct or Fallopian tube, which can be seen in the
figure extending alongside the rectum above the bladder.
The two oviducts (Ovil) unite posteriorly to form the uterus
(Ut).
Fig. 492, II., is a median longitudinal section of the brain.
The spinal cord passes into the medulla oblonyata (M], over
which lies the large cerebellum (Cb), and the small corpora
quadriyemina ($). In front is the large cerebrum (C) and
the small olfactory lobe (L). Fig. 492, III., is a diagram of
the eye (see explanation of the figure).
By carrying the dissection further, the student will be able
to examine the tongue with its papillre ; the epiglottis at
the back of the mouth in front of the trachea ; the larynx,
a, peculiarly modified portion of the trachea in the neck,
with two elastic bands stretched across its interior ; the
bands or vocal cords may be set in vibration by a blast of
air from the lungs. The heart may also be dissected fur-
ther to find the origin of the pulmonary vessels, and to
make out the four divisions or chambers. (Minot.)
The eggs of mammals are exceedingly minute, partly owing
to the small quantity of yolk in them ; the eggs of the few
which have been examined are about a quarter of a milli-
metre (TJ-g — J^Q- inch) in diameter. In the duckbill the egg
is large and with more yolk, like those of birds, being about
five millimetres in diameter. Mammals are divided into
non-placentals and placentals, according as the embryos are
surrounded or not with a placenta or "after-birth." This
organ is a development of the allantois, serving as a means
chiefly of nutrition, being filled with blood-vessels leading
from the walls of the womb of the parent, and also acting
as an organ of respiration, and to carry off the effete pro-
ducts by means of the maternal circulation.
Mammals may be born helpless and only partly developed,
as in the Marsupials ; or capaole of locomotion and sucking
milk, as in the calf or colt ; or helpless for many months,
as in human infants. The changes in the form of the body
after birth are much less, on the whole, than in the birds.
The sexes differ externally in size and ornamentation.
ANATOMY OF THE CAT.
507
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568 ZOOLOGY.
Darwin calls attention to the fact that in mammals the male
wins the female rather by the law of battle than by the dis-
play of high colors and attractive ornaments. During the
breeding season, desperate contests take place between the
rival males ; even the males of the timid hare will at such
times fight until the weaker is killed ; so moles, squirrels,
horses, male seals and male sperm-whales, whose heads are
larger than in the female, and beavers, will fight desperately.
It is a rule that the males of such animals as are provided
with tusks or horns alwaj's fight for the possession of the
female. It is so with bulls, deer, elephants, boars, and rums ;
at the same time these are organs of defence by which the
males protect their family, flock, or herd. On the other
hand, in the female rhinoceros, some antelopes, the reindeer,
as opposed to the other deer, some sheep and goats, etc., the
horns are nearly as well developed as in the opposite sex.
The modes of attack are various : the ram charges and
butts with the base of his horns, the domestic bull gores
and tosses any troublesome enemy, while the Italian buffalo
" is said never to use his horns ; he gives a tremendous blow
with his convex forehead, and then tramples on his fallen
enemy with his knees." Darwin also says that male quad-
rupeds with tusks use them in a variety of ways ; thus the
boar " strikes laterally and upward, the musk-deer with
serious effect downward," while the walrus can strike either
upward, downward, or sideways with equal dexterity.
The males are usually larger when there is any difference
in size ; this is seen in the eared seals, especially Callorhinus
ur sinus, in the ox, Indian buffalo, and the American bison,
as well as the lion. The mane of the latter adds to its ap-
pearance of greater weight and bulk, and Darwin says that
the lion's mane " forms a good defence against the one
clanger to which he is liable — namely, the attacks of rival
lions." As regards distinctions in color, male ruminants
are most liable to exhibit them. In the Derbyan eland the
body is redder, the neck much blacker, and the white band
separating these colors broader than in the females. In the
Cape eland the male is slightly darker than the female. In
the Indian black-buck the male is very dark, almost black,
VOCAL ORGANS OF MAMMALS. 569
while the female is fawn-colored : male antelopes are blacker
than the female. The Banteng bull is almost black, while
the cow is of a bright dun. Among the lemurs the male of
Lemur macaco is coal-black, while the female is reddish yel-
low. The sexes of monkeys differ much in coloration. Cer-
tain male seals, bats, rats, and squirrels have brighter colors
than in the opposite sex. On the other hand, the female
Rhesus monkey is adorned with a brilliant red naked ring
around the tail ; this is wanting in the male, which, how-
ever, is larger, with larger canines, more bushy whiskers
and eyebrows ; and Darwin states that in monkeys the males
usually differ from the females in " the development of the
beard, whiskers, and mane."
The vocal organs of mammals are, in general, constructed
on the same type. The larynx is formed by a modification
of the uppermost ring of the trachea, called the cricoid car-
tilage, to the anterior and dorsal edges of which two arytenoid
cartilages are attached, while a V-shaped thyroid cartilage,
open behind, is attached to its side. The vocal cords, which
are modified folds of the mucous membrane lining the
trachea, are stretched between the arytenoid and thyroid
cartilages, the slit between them being called the glottis,
which is covered by the epiglottis. Thus, in mammals the
organs of voice are situated almost solely at the upper end
of the trachea. In the whales the vocal chords are not de-
veloped. The male gorilla, which has an exceedingly loud
voice, as well as the adult male orang and the gibbon, is
provided with a laryngeal sac. In the howling monkey
(Mycetes] of Brazil, the hyoid apparatus and larynx are re-
markably modified, the body of the former being changed
into a large bony drum or air-sac communicating with the
larynx. The vocal organs are a third larger in the males
than in the females. " The males begin the dreadful con-
cert, in which the females, with their less powerful voices,
sometimes join, and which is often continued during many
hours " (Darwin). They apparently howl, as birds sing,
for the simple pleasure of the thing. Apparently, the most
musical mammal, man excepted, is a gibbon (Hylobates
agilis), which can sing " a complete and correct octave of
570 ZOOLOGY.
musical notes "' (Martin ex Darwin). While quadrupeds
use their voices as alarm calls, most of the sounds are pro-
duced by the males, especially during the breeding season.
Animals are mutually attracted or are individually pro-
tected from the attacks of other species by odors. The
scent-bags or odoriferous glands secreting a fluid differing
in consistencv in different animals, are situated near the
•/
base of the tail, as in the skunk, polecat, musk-deer, civet-
cat and allies, or they may be developed in the side of the
face, as in the male elephant, as well as sheep and goats.
The odor is either of musk or some form of it. The shrew-
mice, by reason of their odoriferous glands, are disliked and
consequently not hunted by birds. Universal deference is
paid to the skunk ; few dogs, and only those which are in-
experienced or peculiarly gifted, attacking them. The
males more usually emit a stronger odor than those of the
opposite sex.
Some mammals have a summer and a winter pelage. The
hare, at the beginning of winter, doffs its summer coat for a
suit of white. The hibernation, or winter-sleep, is a re-
markable feature in the life of quadrupeds living in the
north temperate zone, such as the bear, dormouse, and bats.
During this period the temperature of their body falls,
respiration and circulation are lowered in the one case or
nearly ceases in the other, and life is sustained by the ab-
sorption of fat, which accumulates on the under side of the
neck in the so-called hybernation-glands.
There are about 3500 species of mammals described, of
which 2100 are living ; of these 310 inhabit America north
of Mexico. Mammals live all over the earth's surface, but
mostly in the tropical region, those of the arctic zones having
been derived from the south since the end of the Tertiary
period. The range in space of certain species is very great —
for example, the cougar, panther, or puma ranges from Brit-
ish to South America (Chili). The mammalian fauna of the
Tertiary deposits of the west was far more abundant than now,
the remains of over five hundred species having been already
discovered by Leidy, Cope, and Marsh in the few. spots ex-
amined. The earlier (Eocene) mammals were generalized
ORIGIN OF DOMESTIC MAMMALS. 571
forms, combining in a remarkable degree characters more
elaborated, and in great detail, in different orders of living
mammals, especially the Ungulates. For example, from the
Eocene Coryphodon, a generalized ungulate animal, have
probably been derived the ruminants, the tapirs, hog, hip-
popotamus-like forms, the rhinoceros, and, finally, the
horse. This inference is based on the fact that the bones
and teeth of Coryphodon present characters which are no
longer combined in any one species of mammals, but which
are found worked out in detail in the members of the differ-
ent orders referred to.
Moreover, the early Tertiary mammals had brains much
smaller than in any existing forms, and with only one ex-
ception, without convolutions — showing that the develop-
ment of the size of the brain and its convolutions, and con-
sequently of the intellect, has kept pace with the successive
stages in the specialization shown in existing forms, and
which agree with the increasing complexity of the Ameri-
can Continent and the subdivision of the western part of
the continent into distinct basins, Avith separate mountain
systems and river- valleys. The result of all this apparent
waste of generalized forms, and the survival of the few
favored types now existing, has been the preservation of
animals which have been domesticated by man, such as the
dog, pig, horse, ox, camel, elephant, and of others useful as
food or as intelligent servants ministering to his every-day
wants.
The earliest mammals were small insectivorous or gnaw-
ing marsupials, none larger than a cat, and first appearing
in the Triassic. They may have originated from Theromorph
reptiles.
The Mammalia are divided into three sub-classes — viz., the
Ornithodelphia (duckbill and Echidna), the Diddphia or
marsupials, and the Monodelphia, comprising all the higher
mammals.
Sub-class 1. Ornithodelphia. — The duckbill and spiny ant-
eater (Fig. 493, Echidna hystrix) are the only representatives
of the sub-class, of which there is but a single order, called
Monotremes, and are distinguished by the following char-
acters. The oviducts, vasa deferentia and ureters, open intc
•572
ZOOLOGY.
the cloaca, as in birds. The sternum articulateswith a free cora-
coid, and an inter-clavicle and epicoracoid bone are present.
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The brain differs from that of the mcmlters of the higher sub-
classes.* Echidna lays large eggs, 2 cm. long, placing them
* The hind skull is intermediate between that of Amphibians and
higher mammals. (Parker.)
DUCKBILL AND ECHIDNA.
573
in a mammary pouch, where the young hatch. The duck-
bill also lays large eggs. The embryonic development is
meroblastic, as in reptiles. The toothless jaws* are long and
narrow in the Echidna, or broad and flat in the duckbill
(Ornithorlt i/nrJi us paradoxus Blumenbach), where it is cov-
ered by a leathery integument; the external ear is wanting.
(52
Fig. 494. — Skeleton of Echidna hystrix,— From Brehm's Thierleben,
In the aquatic duckbill the feet are webbed, with claws
of moderate size. It is covered with a soft fur, and is about
half a metre (17-22 inches) long. Its
habits are like those of a muskrat, fre-
quenting rivers and pools in Australia
and Van Di email's Land, sleeping and
breeding in holes extending from un-
der the water up above its level into
the banks, and with an outlet on shore.
It lives on mollusks, worms, and
water-insects. Young duckbills, five
cm. long, have been found in their
nests.
The spiny ant-eater (Figs. 493 and
494) is represented by three species,
the Echidna hystrix Cuvier, of Aus-
tralia, E. Lawesii Ramsay, from Port
Moresby, New Guinea, also by a re-
cently discovered form inhabiting the
elevated portions of Northern New marsupial bones.
Guinea, and called by Gervais Acanthoglossus Bruijnii. In
these singular animals the bill is long and slender, tooth -
* Rudimentary teeth occur in the embryo, in the place occupied by
the plates (Poulton).
63
— One half of
pelvis of the Kangaroo; m,
674 ZOOLOGY.
less, while the palate is armed with rows of strong, sharp
spines ; the tongue is long and slender, like that of the ant-
eater, while the body is armed with quills like those of a
porcupine ; the claws are very large and strong, adapted for
tearing open ant-hills. All the species are from one third
to one half of a metre (12-19 inches) in length.
Fig. 496.— Skeleton of the Kangaroo.— From Brehm's Thierleben.
Rub-class 2. Marsupialia. — These are singular forms, rep-
resented by the opossum in this country, and the kangaroo,
with a number of other forms, in Australia. They differ
from all other mammals in having a pouch (marsupium) for
the reception of the young immediately upon birth, where
MARSUPIALS.
575
they are attached to the nipples at the bottom of the pouch.
This large pouch (absent in some opossums and in the
Dasyuridce) is supported by two long slender bones attached
to the front edge of the pelvis and projecting forward (Fig.
495 in and Fig. 497).
In Tliylacinus, the Tasmanian wolf, these bones are car-
tilaginous. In the opossum, the kangaroo, and probably
most marsupials, the young remains in the pouch attached
to the nipple, which fills the mouth. " To this it remains at-
tached for a considerable period, the milk being forced down
its throat by the contraction of the cremaster muscle. The
danger of suffocation is avoided by the elongated and coni-
cal form of the upper extremity of the larynx, which is em-
braced by the soft palate, as in the Cetacea, and thus respi-
ration goes on freely,
while the milk passes,
on each side of the
laryngeal cone, into
the O3sophagus':
(Huxley). In the car-
nivorous forms the
brain is low in struc-
ture, the olfactory
lobes being very large,
completely exposed,
while the cerebral
hemispheres are Small Fig. 40r.— Opossum (from Teuney's Zoology) and
side view of pelvis with the marsupial bone, M.
and quite smooth.
The dentition of marsupials is characteristic, none having
three incisor teeth upon each side, above and below, and
none but the wombat (Phascolomys], with an equal num-
ber of incisors in each jaw, there being usually more in the
upper than in the under jaw.
The lowest marsupial is the Tasmanian wolf (Thylacinus),
which is rather smaller than the wolf. The Tasmanian devil
(Dasyurus ur sinus Geoffroy, Fig. 383) is a vicious, trouble-
some creature, about the size of a badger. The opossums
inhabit North and South America. They have a long tail
and a plantigrade step — i. e. , they walk on the sole of the
whole foot. The Virginian opossum (Fig. 497, Didi'l/ritys Vir-
576
ZOOLOGY.
giniana Shaw) lives chiefly in trees. Lawson says that
" the female doubtless bret-ds her young at her teats, for 1
have seen them stick fast thereto when thev have been no
.
- -^mai1 /.'
-
M
5
a
3
i>
bigger than a small rasberry and seemingly inanimate. She
has a paunch, or false belly, wherein she carries her young
after they are from those teats, till they can shift for
§
EDENTATE MAMMALS. 577
themselves. Their food is roots, poultry, &r wild fruits.
They have no hair on their tails, but a sort of a scale or
hard crust, as the beavers have. If a cat has nine lives,
this creature surely has nineteen ; for if you break every
bone in their skin and mash their skull, leaving them for
dead, you may come an hour after and they will be gone
quite away, or perhaps you may meet them creeping away."
(" Perfect Description of Virginia," 1649.)
There are squirrel-like flying marsupials (Petaurus),
marsupial rats, marsupial bears, and marsupial ant-eaters
(Myrmecobius), but the most characteristic Australian ani-
mals are the different kinds of kangaroo (Macropus thetidis,
Fig. 498).
The largest species, M. giyanteus Shaw, is 1 • 8 metres, or
nearly six feet long. Kangaroos go in herds, and move by
a succession of long leaps.
All marsupials are stupid, low in intelligence, and, in the
insectivorous and carnivorous forms, of vicious temper.
With the exception of the opossums, all are confined to Aus-
tralia, New Zealand, and New Guinea.
Sub-class 3. Monodelpliia. — While in the marsupials the
termination of the oviduct is double, in the present group
it is always single, whence the name Monodelphia. The
members of the group are also called placental Mammalia,
because the young at birth are of considerable size and
nearly perfect in development, being nourished until born
by a highly vascular mass or thick membrane (placenta)
supplied with arteries and veins, developed originally from
the allantois, which is a temporary embryonic membrane.
The brain, as a rule, presents an advance over that of any
of the preceding mammals, the corpus callosum being better
developed, while the anterior commissures are all reduced.
There are no marsupial bones, though in some Carnivora
certain small cartilages appear to represent them.
There are twelve orders, as follows :
Order 1. Bruta or Edentata. — These creatures, repre-
sented by the sloths, ant-eaters, pangolins, and armadillos,
stand next above the non-placentals or marsupials, as the
brain is but little better developed, the hemispheres in some
578
ZOOLOGY.
forms being nearly smooth, while, in point of their general
structure and intelligence, they stand at the foot of the sub-
class. The teeth may be entirely undeveloped, as in the
common ant-eater, but when developed they are not encased
in enamel. In most Edentates the incisors are absent, bin.
the lateral one may exist in the armadillo (Dasypus). The
feet are formed for grasping or digging, and end in large
straight or curved claws. They are either hairy or pro-
SLOTHS AND THEIR ALLIES. 57i»
tected, as in the pangolins (Fig. 501) and armadillos (Fig.
502), with large thick, scales. They feed on insects and de-
cayed animal matter, or on leaves. They are of moderate
size, though certain extinct forms were colossal in stature.
The leaf-eating forms, viz., the sloths, differ from the
other Bruta in the very long and slender limbs, the hinder
pair the shorter. There are five teeth above and four below,
which become sharp with use, like chisels ; the stomach is
said to be remarkably complex. In disposition these crea-
tures are types of sluggishness ; they live in trees, being
absolutely helpless on the ground, not being capable of
walking on the bottom of the foot.
Waterton says that, in climbing, the
ai (Bradypus tridaciylus, Figs. 499 and
500) uses its legs alternately ; that its
hair " is thick and coarse at the ex-
tremity and gradually tapers to the
root, where it becomes fine as a spider's
web. His fur has so much the hue of
the moss which grows 011 the branches
of the trees, that it is very difficult to
make him out when he is at rest."
Only two Edentates now occur in
the United States, but formerly colos-
sal, sloth-like forms, with some resem-
blance to the ant-eaters, ranged over Fig. 500. — Ai, or Three-
' toed Sloth, in its natural atti-
the Southern and Middle States as far tude.— After Wood, from
, . i • ji • i Waterton.
north as Pennsylvania, their bones oc-
curring in ;aves. Such was the Megatherium, a gigantic,
sloth-like creature, which extended from Pennsylvania to
the pampas of South America, and whose skeleton is over
five metres (18 feet) long. With it was associated the Mey-
alonyx, first described by Thomas Jefferson ; it was as large
as a bison, as was the Mylodon. Thes? animals walked on
the soles of the feet, could rise on their hind legs and partly
support themselves by their thick tails, pulling down large
trees and feeding upon the leaves and smaller branches.
In the ant-eaters the jaws are toothless, but very long, and
the tongue is of great length and very extensile ; the sub-
580
ZOOLOGY.
maxillary glands are very large, so that the viscid salivary
fluid is very abundant. They burrow into ant-holes, thrust-
ing the tongue among the ants, which stick in multitudes to
the viscid, writhing rod, and are withdrawn into the mouth.
The pyloric end of the stomach is gizzard-like. The ant-
eaters (Myrmecophaga) inhabit South America.
The pangolins, or species of Manis, are mail-clad ant-
eaters, the body and long tail being covered with large
overlapping scales. When molested they roll up the body.
In walking the hind feet rest on the soles, while the fore-
feet are supported by the upper side of the long bent
claws.
Fig. 501.— Pangolin (Manis (ongicaudata) robbing white ant-nests. — After Monteiro.
The long-tailed pangolin of the West Coast of Africa (Fig.
501) tears open with its long claws the nests of the white
ants. It is nearly f metre (28-30 inches) in length.
The armadillos (Fig. 502) are small mammals covered with
a carapace, consisting of from three to thirteen transverse
rows of movable scales ; by rolling into a ball, these singu-
lar creatures become thoroughly protected from their ene-
mies. Dasypus novem-cinctus Linn, is much like the Peba
armadillo, and extends from South America to Texas. The
strange extinct armadillo-like Gli/pfodon of South Amer-
ica, which was over two metres (8 feet) long, was covered
THE ARMADILLO.
581
by a heavy, solid coat-of-mail consisting of polygonal plates
soldered together immovably.
The three following orders have by most authors been
placed near the Primates (monkeys, etc.), but Owen, from
I s-e.
the characters afforded by the brain, has shown that they be-
long at or near the bottom of the scale. Gill has shown
that not only by the brain, but by other characters corre-
lated with the low development of the brain, the Rodents,
582 ZOOLOGY.
Insectivora, and bats should be associated with the Edentates
in Bonaparte's division (or, as Gill terms it, super-order)
of Ineducabilia (which corresponds to Owen's sub-class
Lissencephala). In these four orders, then, the cerebrum is
small, smooth, with none or few convolutions ; in front
it does not cover the olfactory lobes, and behind leaves
the cerebellum wholly or partly uncovered.
On the other hand, in the super-order Educalilia, com-
prising the following order : Cete, Sirenia, Proboscidia, Ht/-
r;/roidea, Toxodontia, Unynlata, Carnivora, and Primates,
the brain has a relatively large cerebrum, behind overlap-
ping much, or all, of the cerebellum, and in front much, or
all, of the olfactory lobes (Gill). The cerebrum is also con-
voluted ; the convolutions increasing in number and com-
plexity, until we reach the apes and man, and accompanied
by increasing intelligence and capability for mental im-
provement. Other important characters are mentioned by
Owen and by Gill in support of this arrangement.
In the smooth small cerebrum, as well as in other re-
spects, the Ineducabilia are related, together with the mar-
supials and duckbill, to the birds and reptiles. In the
cloaca, the convoluted trachea, the long, slender, beak-like,
toothless jaws and the gizzard of the ant-eaters, the quills
of the porcupine and hedge-hog, the proventriculus or crop
of the dormouse and beaver, in the growing together of the
three chief metatarsals of the jerboa, as in birds, in the keeled
sternum and wings of the bats, there are points of resem-
blances to birds. Owen, whom we have quoted, also adds
the aptitude of the bats, insectivores and certain rodents
' to fall, like reptiles, into a state of torpidity, associated
with a corresponding faculty of the heart to circulate car-
bonized or black blood."
However, there are points in which these orders are re-
lated to the lemurs and monkeys.
Order 2. Glires. (Rodentia. ) — The rats, squirrels, por-
cupine, and beaver are common examples of this extensive
group. They differ from other orders in the large incisors,
the dental formula of which is normally f (f in Leporidce
and Lagoi>///t</<r), and in the absence of canine teeth. The
ORDER OF RODENT8.
583
condyles of the lower jaw are longitudinal, not received in spe-
cial glenoid sockets, but gliding freely backwards and forwards
in longitudinal furrows. The feet are adapted for walking
and climbing or burrowing, the claws being well developed.
A peculiarity in the incisors is that they grow out as fast as
they are worn down ; this is due to the fact that the pulp is
persistent ; the enamel in front causes them to wear away
Fig. 503.— American Flying Squirrel (Sciuropterus volucella)
behind so that they are chisel-shaped. The species are pro-
lific, live mostly on vegetable food, and are of small size ;
the muskrat, beaver, and capybara being the largest mem-
bers of the group. The flying squirrels (Fig. 503) take
short flights by means of the expansion of the skin between
the fore and hind legs. The Norway lemmings are notice-
able for their remarkable migrations from the elevated
584 ZOOLOGY.
plateaus of Scandinavia down and into the sea ; the object
and origin of which are inexplicable, and are not indicative
of much intelligence. From this and their nest-building
habits, rodents are, as a rule, not unlike birds ; and Owen, for
these reasons, ascribes to them a low degree of intelligence.
Granting that this is the case, an exception to this rule is
seen in the social beavers, which evince a high, exceptional
degree of intelligence. Beavers build a dam in a running
stream so as to create an artificial pond as a refuge when at-
tacked, as well as a subaquatic entrance to their lodges and to
their burrows in the banks of the streams they inhabit. Bea-
ver dams are built at first by a single pair or family, and are
added to from year to year, and afterwards maintained for
centuries by constant repairs. They are built of sticks and
mud, usually curve up stream, with a sloping water-face.
Beavers lay up stores of wood for winter use in the autumn ;
they can gnaw through trees eighteen inches in diameter ; they
Avork mostly at night. They often construct artificial canals
for the transportation of the sticks of wood to their lodges.
This, in the opinion of Mr. Morgan " is the highest act of
intelligence performed by beavers." When ponds do not
reach hard-wood trees or ground in which they can burrow
for safety, they will build canals with dams, and so excavate
them that they will hold the surface drainage. Morgan
describes one canal about 1G1 metres (523 feet) long which
"served to bring the occupants of the pond into easy con-
nection, by water, with the trees that supplied them with
food, as well as to relieve them from the tedious, and per-
haps impossible, task of moving their cuttings five hundred
feet over uneven ground, unassisted by any descent." Bea-
vers, in swimming, use their tail as a scull, and the hind
feet being webbed, its propelling power while swimming is
very great. They carry small stones and earth with their
paws, holding them under the throat, and walking on their
hind feet. They use the tail in moving stones, working it
under so as to " give it a throw forward." Beavers are very
social, working together and storing up wood in common.
" A beaver family consists of a male and female, and their
offspring of the first and second years, or more properly,
II. \11TT8 OF THE BEAVER.
585
under two years old. The females bring forth their young
from two to five at a time, in the month of May, and nurse
them for a few weeks,
after which the latter
takes to bank." They
attain their full growth
at two years and six
months, and live from {^^js^^^s^*^- „
twelve to fifteen years. *
Allied to the beaver, Fl(, 504.— Sewellel or Shpwt'l. Much reduced,
but forming the fy\v. -From American Naturalist.
of a distinct family, is the singular sewellel or showt'l
Fig. 505.— Alpine Hare of the Rocky Mountains.— After Haycleu.
(Haplodon rufus Cones, Fig. 504) of the mountains of west-
ern Oregon and Washington Territory. It is nearly as large
* The American Beaver and las Works. By Lewis H. Morgan. 1868.
586
ZOOLOGY.
as a muskrat, is nocturnal in its habits and, therefore, rarely
seen, and burrows in the earth, feeding on roots.
The lowest in intelligence are, perhaps, the hares, rep-
resented by the common varying hare (Lepns America-
nus Erxleben, Fig. 505), of which an interesting variety,
L. Bairdii, lives on the Alpine summits of the Rocky Mouu-
«•* *g?-\ f*_^~
^^^fe
Fig. 506.— The Spalax or Blind Rat.— After Owen.
tains. The largest of all existing rodents is the Capy-
bara of South America, which looks like a pig. This is
succeeded by the porcupine, which either lives in trees or
burrows in the earth, while the more intelligent, active
forms are the beaver, muskrat, the European blind rat
(S2)alax, Fig. 506) the rats and mice, squirrels, and lastly
the marmots. The domes-
tic mouse and the two rats,
the brown or Norway rat
(Mus decumanus Pallas),
the black rat (Mus rat In*
Linn.), and the common
house mouse (Mas m/t^c/t-
lus Linn.), are cosmopoli-
tan animals. The jumping
mouse (Fig. 507) has remarkably long hind legs and short
fore legs. Peculiar to the western plains is the prairie-dog,
(Cynomys ludovicianus] which represents the marmots of
the Old World ; it is semi-social and takes in perforce as
boarders the owl and rattlesnake, which devour its young.
Fig. 507. — .Tumping Mouse (Zapus hud-
sonius).— From Tenneys Zoology.
MOLES AND SHREWS.
587
Order 3. Insectivora. — In the moles the incisors, the
canines, and molars are well developed, and the molars have
the crown surmounted by conical projections called cusps.
The fore feet are plantigrade, with large claws, and the en-
tire limb is short, thick, mus-
cular, and fossorial,£.e., adapted
for burrowing in the soil (Fig.
508), The shrews comprise
the smallest mammals. Nearly
all are nocturnal, burrowing
tinder the surface, and never
seen by day ; consequently,
their eyes are small, and most-
ly hid under the fur ; while the
ears arc small and concealed bv
*/
the hair.
The shrews are mouse-like,
having feet of the normal form,
and a long nose. In our com-
mon shrew (Sorex platyrliinus Wagner, Fig. 509), the nose
is long, and the tail shorter than the head and body.
The genuine moles are the characteristic forms of the
•order ; the most peculiar being the star-nosed mole, Condy-
Fig. 508.— Bones of fore leg of a
Mole. 52, the cubital scapula ; 53,
humerus ; 54, ulua ; 55, radius.— Af-
ter Owen.
Fig. 509. -Common Shrew.— After Cones.
1 >ira cristata Linn., which occurs from the Atlantic to the
Pacific Ocean, while the common mole (Fig 510) is abundant
in the Eastern United States.
A flying form with a superficial resemblance to the bat, and
588
ZOOLOGY.
with the same habit of sleeping, head downward, holding on
by its hind feet, is the Craleopifhecus of the East Indies.
This singular creature has been placed among the lemurs
by some authors. G. volans Pallas inhabits Java, Sumatra,
Borneo, and Siam.
Fig. 510.— Common Mole (Scalops aqvaticm Linn.).— After Coues.
Order 4. Chi ropier a. — The bats form a well-circumscribed
group of mammals, very distinct from any other, especially
in the greatly modified fore-limbs, the radius and ulna being
united, and the second to the fifth metacarpal bones and
phalanges being very long and slender, supporting a thin,
leathery membrane or skin, extending to the hind legs, and
wholly or partly enclosing the tail ; the hind toes being, how-
ever, free, as when at rest or in the vegetarians when feeding,
bats hang head downwards, holding on bv their claws. The
o o v
sternum is slightly keeled for the attachment of the mus-
cles of flight. The mammary glands are pectoral. In other
respects, especially the dentition, the bats resemble the
hixectivora. The form of the teeth differs from the ordi-
nary insectivorous bats in those which live on fruit. The
vegetable-eating or fruit-eating bats have a superficial resem-
blance to the flying lemurs ; and because their mamma? are
pectoral, have been placed next to the Primates.
HABITS OF BATS.
589
Beats live in caves and in the hollow of trees by day ; all
hibernate in the same situations, going into winter quarters
in the autumn, and reappearing in the warm twilight of
spring. Though the eyes are small, and the sight, so far as
Fig. 511.— Skeleton of a fruit bat (Pteropus).— After Owen.
•we know, deficient in keenness, they show wonderful skill
in avoiding objects during their rapid flight. The ears are
very large, and in the vampires the nose is adorned with
590
ZOOLOGY.
sensitive, leaf-like growths of complicated form. Certain
bats are known to enter houses, and suck the blood from
Fig. 512.— Skull of adult sperm whale si-en from above and from the side. ?/o,
baeioccipital bone ; eo, exoecipital ; so, supraocclpital ; p, parietal ; *, squamosal ; f,
—
oe e, eo ; s, , e *, ,
frontal ; pi, palatine; j, jugal ; sh, stylohyoid ; bh, basihyoid ; t/i, thyrohyoid.— After
Flower.
the extremities of sleeping persons, who awaken to find their
feet covered with blood. The true vampire is harmless.
CETACEANS.
591
The largest bats are the fruit bats or flying foxes (Ptero-
of the East Indies; one species of which expands one and
a half metres (nearly five feet) from w?s ^
tip to tip of the wings. Our com- |J % 3
monest species is the little brown « '
bat, \'<'s/n'rtiUo subulatus of Say;
nearly as common is the red bat,
Atalapha noveboracensis Coues.
Order 5. Cete (Cctacea). — We
now come to the EducaMlia, in
which the brain is more highly de-
veloped, and begin with two very
aberrant orders, the whales and
Sirenians, in which the body is
fish-like, though the tail is hori-
zontal ; the pelvis and hind limbs
are wanting, either wholly, or mi-
nute rudiments may be present ;
and they are aquatic, occasionally
leaping out of the water, but usu-
ally only showing the dorsal fin or
nose when at the surface to breathe.
The whales and porpoises have
a large, broad brain, with numer-
ous and complicated deep convolu-
tions.
In the skull (Figs. 512, 513) the
aperture for the spinal cord (fora-
men magnum) is entirely posterior
in situation and directed some-
what upward. The lower jaw is
straight, with no ascending ramus,
the narrow condyles being situated
at the end of the jaw, at the point
indicated by the angle of the ramus
in other mammals. The teeth are
conical, with a single root, but are
sometimes wanting. There is no neck
V
the cervical verte-
brae are sometimes confluent, forming a single mass. The
592 ZOOLOGY.
limbs form a pair of paddle-like appendages just behind and
under the head, which are supported by short, flattened
limb-bones, the carpals and phalanges often separated by car-
tilage ; the second digit being composed of more than three
phalanges. There are two mammae situated near the anus.
The external nostrils are either single or double, and are sit-
uated on the top of the head ; they are modified to form the
spiracles or " blow-holes ;" certain folds of the skin prevent
the water from entering the air-passages. The vapor blown
from the holes does not consist of water, but of the mucus
from the nostrils, and the moisture in the breath. The
blow-holes vary in form in different kinds of whales. The
" spout" of the sperm-whale issues in a single short
stream from the extreme end of the snout, and curls over
in front of the head; that of the fin-back whale forms
a single column of vapor about ten feet high ; the right,
humpback and sulphur-bottom whales each "blow" in a
double stream which is directed backward toward the tail.
Whales are rarely over fifty feet long; the sperm-whale
lias been known to reach a little over twenty-three metres
(76 feet) in length, but Professor Flower questions whether
the sperm-whale frequently, if ever, when measured in a
straight line, exceeds a length of sixty feet. The largest of
all whales, as of all existing animals, is the fin-back or ror-
qual (BalcBnoptera loops), which sometimes measures thirty-
four metres in length. The smallest Cetacea are the por-
poises.
In the Mysticete or whalebone whales, the teeth, present in
the embryo, become reabsorbed into the gums before birth and
are replaced by plates of whalebone (Fig, 514), three hun-
dred of which may be present on each side of the mouth.
The inner edges of these plates have projecting fibres, form-
ing a rude strainer ; these whales feed on small pelagic jelly-
fish, molluscs and Crustacea, by taking in a mouthful of
water, and then pressing the tongue against the roof of the
mouth, expelling the water through the openings between
the plates, the fibres acting as a strainer. Three thousand
five hundred pounds of whalebone have been obtained from
a single bow-head or Greenland whale (Balania mysticetm}.
THE SPERM WHALE.
593
The cachelot or sperm-whale (Fig. 515) has an enormous
head, one third the length of the body, the upper jaw being
toothless. It is without the power of smell. It grows to
the length of sixty feet. Above the nasal, frontal, and
maxillary bones are cavities filled with a fatty fluid called
spermaceti, used in the manufacture of candles, ointments,
and cosmetics, such as cold cream. A large sperm-whale
will yield 2500 kilograms of this substance. Another
Fig. 514.— Fin-whale. From Liitken's Zoology.
valuable substance is ambergris, a morbid product, the result
of injury to the intestine by the beaks of cuttle-fishes, upon
which animals the toothed whales largely prey. It is a kind
of bezoar or gall-stone, fatty, aromatic, burning with a clear
flame. It is composed of benzoic acid, united with chlorine,
of a balsamic substance, and ambrein. It is used in making
perfumes. Lumps are occasionally thrown ashore, and it is
worth about five dollars an ounce.
''>_' . /< . LrUG .))[<•! II , /, III' l/ail
spiral strips or blanket pieces.— After Beak;, from Gill
But the chief use of whales is the oil extracted from the
fat enveloping the body, called blubber by whalers. The
most valuable' of the whales is the Greenland whale, as it
contains the most oil, individuals having been known to
yield nearly three hundred barrels.
ZOOLOGY.
The whale-fishery first sprang up in the twelfth century
in the Bay of Biscay. In the New England colonies whales
were pursued in boats from the shore. In 1854 the fishery
culminated ; since then it has decreased. It is principally
carried on by Americans, New Bedford being now the lead-
ing port from which whalers are sent out to the Arctic
Fig. 516.— Kogia Floweri.— After Grayson, from Gill.
regions and Behring's Straits, one hundred and ten vessels
having been sent out in 1876 from this port.
Closely allied to Physeter mar.roceplialus Lacepede, arc
the pigmy whales, represented on the California!! coast by
Kogia Floweri Gill (Fig. 516), which is nearly three metres
Fijr. 517.— Skull of Callignathus shnus, seen from the side and from below. —
After Owen.
(nine feet) in length, with a conical head. In
simus Owen (Fig. 517) the skull is short and broad ; it is
found on the coast of Madras, India.
Thenarwhale (Monodon monoceros Linn.) is distinguished
by the long, spirally-twisted, horn-like tusk of the male,
formed of the left upper incisor, which becomes nearly three
SIRENIANS OR SEA-COWS. 595
metres long, the female having no visible teeth ; there being
two rudimentary incisors which never appear through the
gum. It ranges from Hudson's Straits to the Arctic seas,
having formerly been seen along the coast of Labrador. To
the family of dolphins and porpoises belong the white whale
or Delphi napterus leucas Pallas, which ranges from the Gulf
of St. Lawrence northward ; the grampus ( Grampus griseus
Cuvier) ; the blackfish, of which there are two species, one
GloUcephalus melas Trail, ranging north of New York, and
one G. bracliypterus Cope, to the southward, and the por-
poises, of which the most common on our coast is Phoccena
brachycium Cope ; the rarer is P. lineata Cope. On the
coast of Labrador, as well as northward, occurs the thrasher
whale or killer (Orca gladiator Gray) which has large
teeth, and a high dorsal fin ; it attacks whales, gouging out
the flesh from their sides. Certain fossil whales were pigmies
in size ; while the Zeuglodon of the Alabama Eocene Ter-
tiary beds, was an enormous serpent-like whale, which must
have measured over seventy feet in length.
Order 6. Sirenia.— In the few species of sea-cows represent-
ing this order, the lower jaw is more as in other mammals,
having well developed ascending rami and normal transverse
condyles and coronoid processes. The teeth are well developed,
both incisors and molars, the latter with flattened or ridged
crowns, adapted for the trituration of vegetable food. A
neck is indicated ; the two nostrils are situated at the
upper part of the snout, and the lips are beset with stiff
bristles, while the mammae are pectoral. The fore limbs are
of moderate length, with five well-developed digits, but still
fin-like and bent at the elbow. The brain is narrow com-
pared with that of cetaceans, and the heart is deeply fissured
between the ventricles. The manatees of America and the
dugong of Australia and India (Fig. 518) live in the mouths of
large rivers, feeding on seaweeds, aquatic plants, or the gra.-s
along the shore. The Florida manatee (Manatus Ameri-
canus Desmarest) grows to a length of from two to nearly
three metres. It ranges from Florida to the Amazons, where
it is called Vacca marina ; it ascends the river as far as Pebas,
Peru, and is killed and eaten, its flesh resembling beef.
596
ZOOLOGY.
Steller's manatee (Rhytina Stelleri) was in the last century
found in abundance on the shores of Behring's Island on the
coast of Kamtchatka ; twenty-seven years afterwards (in
17G8) it was totally exterminated by the sailors ; a few im-
perfect skeletons exist in the National museum. This is the
g
•8
a
1
«
e
o
I
p
I
largest Sirenian known ; it was over six metres in length.
It differed remarkably from the other forms, in having no
teeth, but was provided with a very large, horny, palatine
plate, and a corresponding one covering the enlarged point
of union, or symphysis, of the lower jaws. In the Tertiary
THE PROBOSCIDIANS.
597
Period a fossil Sirenian (HaUthertum) inhabited the shores
of western Europe.
In the structure of the skull, their dentition and their her-
bivorous habits the Sirenians in a degree connect the Ceta-
ceans with the Ungulates, and elephants.
Order 7. Pro boscidia.— Only two representatives of this
group are now in existence, the Asiatic and African elephant,
a number of other forms having become extinct. The group
is well circumscribed, when we consider the living species,
but in the early (Eocene) Tertiary Period there existed forms
which indicate that the Proboscidians and Ungulates had a
common
origin.
In
the elephants the up-
per incisors are enor-
mously developed,
while there are none
in the lower jaw.
There are no canine
teeth, while the few
molars are large, trans-
versely ridged. In the
elephants the ridges
are numerous, the
spaces between them
filled with cement.
The young mastodon
has cement on the up-
per surface of the
tooth ; the ridges af-
terwards become free
and covered with
enamel. A peculiari-
ty in the elephant's skull is its large size, the brain cavity
being very small in proportion to the bulk of the skull itself.
To give lightness to what would bo otherwise an insupportable
weight, the cranial bones contain numerous large air-cells
(Fig. 520). Another remarkable feature,from which the group
takes its name, is the trunk or proboscis, a long, thick, fleshy,
flexible snout, growing from the front edge of the nasal
Fig. 519.— Skull of young elephant ; 22, premax-
illary hone containing; the root of the tusk, k ; 15,
nasal hone ; 7, parietal bone or temporal region ;
2t>, malar, zygomatic arch ; i, lower jaw ; c, upper
jaw ; m, molar tooth ; 21, maxilla ; 11, frontal ; g,
squamosal.— After Owen.
598
ZOOLOGY.
bones (Fig. 520, a). The trunk ends in a finger-like, highly
sensitive point, below which are situated the nostrils. The
brain has a large cerebrum, with numerous convolutions, but-
more of the cerebellum is exposed than in any of the succeed-
ing orders ; in this respect and in the large incisors the Pro-
boscidians approach the Rodenfui.
In the nature of the limbs, especially from the fact that
elephants walk on their toes, a relation to the Ungulates is
indicated. They are
five-toed, but the dig-
its are represented ex-
ternally only by the
five broad, shallow
hoofs, the foot being
supported by thick,
broad pads. The legs
are almost wholly free
from the body. The
placenta is zonary,
non-deciduate. The
skin is naked in the
existing elephants,
but the extinct mam-
moth was covered
sparsely with hairs.
Elephants live in
herds, browsing on
the leaves of trees
and herbs. They at-
tain a height of from
three to four metres
(10-12 feet). The
Asiatic elephant has a concave forehead and small ears, while
the African species has a full, rounded forehead and large
ears, with four hoofs on the fore feet and three on the hind
feet, the Asiatic elephant having one more hoof on each foot.
The fossil mammoth (Eli'/tlmx prin>i</t'ttii/x Blumenbach),
which was contemporaneous with early man, was not much
larger than the existing species. Its tusks, however, were of
Fig. 520.— Section of an elephant's skull, showing
tlu- small size of the brain cavity as compared to the
whole skull, and the numerous large air cells, v,
posterior nostrils ; 13, cavity of the nose ; a, front
opening of the bony nostrils, to the edge of which
the trunk is attached.— After Owen.
MAMMOTH AND MASTODON.
599
great size, some being five metres long. It formerly ranged
in herds over northern Europe and Asia, as well as America,
bones occurring under swamps in the Northern and Middle
United States. A carcass frozen in the ice, with the hair
still on, was discovered near the mouth of the Lena River in
Siberia. A pigmy, extinct Maltese elephant of the late Ter-
tiary Period was only 1.7 metres in height.
The Mastodon was characterized by having incisors in both
jaws of some of the species. The mastodon had molars with
Fig. 521.— Dinotherium.— From a restoration by Brandt.
conical cusps, and was 3f-4 metres (12-13 feet) in height.
The mastodon (Mastodon giganteum Cuvier) was an earlier
type than the elephant, and formerly inhabited the North
American continent.
In the Dinotherium of the Middle Tertiary (Fig. 521) there
were only two incisors, and they grew out from the under
jaw. It was elephantine in its form, according to Brandt.
Order 8. Hyracoidea. — With some affinities to the Ro-
dentia, and a decided resemblance in some particulars to
600 ZOOLOGY.
the rhinoceros among the Ungulates, the members of this
small order are in general characterized by having long,
curved incisors ; and by feet provided with pads as in Ro-
dents and Carnivora, the toes being encased in hoofs (four in
front and three behind). The Hyrax, a little gregarious
animal living in holes among rocks, of which there are two
or three species known, one South African, and another in
the Holy Land and Arabia, thought to be the coney referred
to in the Bible, is the only genus.
Order 9. Toxodontia. — Of this group, of which no spe-
cies are now living, the types are Toxodon and Nesodon.
They are placed by many authors among the odd-toed Ungu-
lates, not far from the tapirs. Their incisors were f or ^.
Toxodon in its skull bore some resemblance to the Sirenians,
and iu the teeth were in certain respects like the Edentates.
The species lived in South America during the early Tertiary
Period.
Order 10. Ungulata. — The larger proportion of mammals
belong to this interesting order, which comprises nearly all
those species of mammals useful to man, such as the ox,
camel, pig, deer, and horse. They are, in general, charac-
terized by walking, so to speak, on their toes, each toe being
at the end encased in a horny hoof ; not more than four toes
being completely developed on a foot. The teeth are usually
well developed, with six incisors in each jaw, but these are
often, especially in the upper jaw less in number or entirely
absent, as in the sheep, deer, and ox. The collar-bone is
absent. The brain still remains small compared with the
bulk of the skull, and the intestinal canal is of unusual
length compared with that of animals of the previous orders.
The Ungulates have been divided by Owen into two sub-
orders, according to the odd number of toes (Perisso-
dactyla) or even number (Artiodactyla). In the Perisso-
dactyles there may be three toes on each foot, as in the rhi-
noceros, or one, as in the horse ; while in the Artiodactyles
there may be four toes (Hippopotamus), or two, as in the
giraffe, or two functional and two rudimental, as in the ox
and deer, i. e., most Ruminants. The more generalized ex-
isting form of Ungulates is the tapir ; the most specialized
ORDER OF UNGULATES. GO!
typo is the horse, with its single toe on each limb. A large
number of extinct Tertiary Ungulates in the Western States
and Territories, and the Tertiary basins of Paris and Lon-
don, more or less allied to the tapir, especially Cnri/itkodon,
Anoplotlieriuin, Palceotlieriuni, etc., were generalized or
ancestral forms, from which the modern, more specialized
types have probably been evolved, and a study of these fossil
Ungulates shows that there was then (/. e., in Eocene times)
an essential unity of organization in all Ungulates, including
the Ruminants ; the breaking up of the Ungulate stem into
special groups, along favored lines or paths of development,
having resulted in a gradual improvement and elabora-
tion of particular parts, which rendered them more fitted
for their present life, and more intelligent in meeting and
overcoming the emergencies their more complex surround-
ings subjected them to. Thus in the Eocene Ungulates,
such as Coryphodon, the cerebrum was small, without convo-
lutions, indicating a slight degree of intelligence compared
with the modern Ungulates, while the gradual differentiation
of the horse, with its single toe and hoof, from its tapir-like
ancestors, is a marked example of the intelligent, beneficent
selection of favored, useful types which has gone on from the
earliest geological times.
All this specialization of type involved the destruction of
great numbers of forms unfitted to withstand changes in
their surroundings, or not sufficiently intelligent or wary to
avoid the attacks of carnivorous forms, and thus the present
number of Ungulates is much exceeded by the fossil forms.
Perissodactyles. The odd-toed Ungulates, on the whole,
stand lower than the even-toed forms. They all have at
least twenty-two dorsal and lumbar vertebrae, and a simple
stomach, with a large, sacculated coecum. The tapirs are
the more elemental, generalized forms. Fossil tapirs occur
in the older Tertiary beds of the West. The snout is
almost proboscis-like, and the legs are moderately long, with
four toes in front, three toes behind. The tapirs inhabit the
tropics of the New World and Sumatra. They are succeeded
by the rhinoceros, represented in this country by a number
of extinct Tertiary allies, the living species being restricted
€02 ZOOLOGY.
to Africa and the East Indies. The skin is remarkably thick
and dense, while these animals have either one or two long
median horns growing from the skin of the nose. A rhinoc-
eros contemporary with early European man formerly inhab-
ited England, France, and Germany, and extended into Si-
beria.
A number of fossil forms lead up to the family compris-
ing the horse, ass, zebra, and quagga, etc., in which there
is a single toe, being the third on each limb. Their den-
tion is — •
6 il 4-4 3-3
The genealogy or series of ancestral extinct Ungulates
leading from tapir-like forms to the modern horse has been
worked out partly by Huxley, and especially by Marsh, who
has with Leidy discovered a large series of remains in the Ter-
tiary beds of central and western United States, America being
the original home of the horse. The earliest member of the
.series directly leading up to the horse was Eoliippus, an older
•eocene form, about as large as a fox, which had four Avell-
developed toes and the rudiments of a fifth on each fore-foot,
and three toes behind. In later eocene beds appeared an
animal (Oroliippus) of similar size, but with only four toes in
front and three behind. In newer beds, i. e., lower miocene,
are found the remains of MesoMppus, which was as large as
a sheep and had three toes and the splint of another in each
fore-foot, with but three toes behind. In later miocene beds
another form (AnchWierium or Miohippus) had the same
number of toes, but Avith the " splint bone of the outer or fifth
digit reduced to a short remnant." The splint bones, then,
represent two of the digits of several-toed animals. The suc-
ceeding forms were still more horse-like. " In the Pliocene
above, a three-toed horse (Hipparion or ProtoMppus), about
as large as a donkey, was abundant, and still higher up a near
ally of the modern horse, with only a single toe on each foot
(Pliohippus) makes his appearance. A true HJquus, as large
ns the existing horse, appears just above this horizon, and
the series is complete." (Marsh.) Fossil horses extended
over portions of North and South America, but became ex-
tinct before the present Indians
THE HORSE AND ITS VARIETIES.
603
The horse (Equus caballus Linn.) is the most useful of all
domestic animals, and next to ships a prime means of the
diffusion of civilization. By artificial selection a great num-
ber of varieties, races, and strains have been produced,
adapted for the performance of different kinds of work. The
horse only exists in a domesticated state. Sanson states that
604
ZOOLOGY.
the horse in the Orient has five, and in the west (Africa) six
lumbar vertebrae ; in Arabia both forms occur ; in the horse
with but five lumbar vertebrae the shape of the skull is also
different. The Hemippus, the tarpau and muzir of Tartary,
as well as the white, shaggy horse of the elevated plains of
Pamir in central Asia which is often regarded as the original
stock, may be a race which has returned to a wild state, since
partly wild horses occur in Syria, on the Don, and live
in great herds on the llanos and pampas of South America.
There are two primitive races of horses, the Oriental and
Western. To the first belong three types : the Arabian, with
Fig. 523. — Stomach of a ruminant (sheep), showing the four compartments ; q, oeso-
phagus ; b, paunch ; c, honeycomb or reticulum ; of, liber psalterium or manyplies ; e,
true digestive stomach ; /, beginning of the intestine. —After Owen.
the Berber, Andalusian, Neapolitan ; and in England the
blood horse ; the Nizaischan type of the Deccan, India, to
which belong the Persian, Turkestan, Turkish horses, and
the Tartarian. The western races comprise the Frieseland,
to which belong the Brabant, Holstein, Mecklenburg, and
the English farm-horse, and among others the Percheron
horse, of France. Ponies are dwarf horses produced in cool,
mountainous areas, such as the Shetland Islands. The wild
ass (Equus onager Brisson) ranges from the Indus to Meso-
potamia. Equus hemionus Pallas, the Dschiggetai or Kiang,
goes in herds in central Asia and Mongolia. The hinny and
EVEN-TOED UNGULATES. 605
mule are infertile hybrids of the horse and ass (Equus
asinus Linn.).
Artiodactyles. — The even-toed Ungulates comprise the
peccary, pig, hippopotamus, and the Ruminants represented
by the deer, sheep, ox, and camel. The pig and peccary are the
descendants of a number of extinct earlier forms which flour-
ished in the Tertiary Period ; the pig, as Marsh observes,
having held its own with characteristic pertinacity. The
Hippopotamus (Fig. 522) has a large head, with large canines,
a clumsy body, and short, four-toed legs. Hippopotamus
amphibius Linn., ranges from the Upper Nile to the Cape of
Good Hope, and westward to Senegambia. It is nearly
3£ metres (11 feet) in length.
Ruminantia. — The remaining Artiodactyles are called
Ruminants, from the fact that they chew their cud. The
molars are provided with two double crescent-shaped folds
(compare Fig. 490). The stomach (Fig. 523) is divided into
at least three, usually four compartments, i.e., the paunch,
the reticulum or honeycomb, so named from the polygonal
cells on its interior, the psalterium or manyplies, and lastly
the rennet or true stomach. When a sheep, cow, or any
other Ruminant feeds, it thrusts out its long tongue, seizes
a bunch of grass, and bites it off by pressing the incisors
of the lower jaw against the toothless gum of the opposing
part of the upper jaw ; the mouthful of grass is then swal-
lowed, mixed with much saliva. When its appetite is satis-
fied it seeks a retired spot away from its carnivorous ene-
mies, if not a domesticated animal, and after lying down,
suddenly regurgitates a ball of grass, the cud,* which it slow-
ly grinds up between its molar teeth into a pulp. The
cropped grass passes into the honeycomb and paunch ; the
manyplies serves as a strainer for the pulp, which in the
fourth stomach is digested by the gastric juice.
Among a number of fossil forms leading up to the exist-
* The regurgitation of the cud is probably due to a sudden and sim-
ultaneous contraction of the diaphragm and of the abdominal muscles,
which compresses the contents of the rumen and reticulum, and
drives the sodden fodder against the cardiac aperture of the stomach,
which opens and the cud is propelled into the mouth, f Huxley.)
ZOOLOGY.
•:•:
' i
E YEN- TOED UN G i:LA TEti.
GOT
Fig. 525.— Skeleton of Sivatherium restored.— After Hawkins,
Fig. 526.— Virginian Deer.— From Catou.
608
ZOOLOGY.
ing deer and antelopes is the Sivath&rium (Fig. 524, 555)
of the Tertiary beds of the Himalaya Mountains, which had
two pairs of horns, and were gigantic creatures, nearly as
Fig. 527.— Elk or Wapati.— From Caton's Antelope and Deer of America.
bulky as an elephant, and of the singular form approxi-
mately indicated by the accompanying illustrations, having
affinities to the antelopes and the giraffe.
The deer family (Cervidce) is represented in the United
THE SHEEP AND ITS VARIETIES.
609
States by the common Virginian deer (Cariacus Virginianus
Gray, Fig. 526), the elk or wapiti (Cervus Canadensis Erxle-
ben, Fig. 527), and the caribou (Ranyifer caribou Audubon
and Bachman), which is probably a variety of the European
reindeer (R. tarandus Sundevall). In these beautiful, grace-
ful forms the solid antlers are cast off annually ; with the
exception of the reindeer the females or does have no antlers.
The prong-horn antelope (Antilocapra Americana Ord,
Fig. 528.— Head of young Prong-horn Antelope.— After Hays.
Fig. 528) so characteristic of the western plains, also drops
its horns in the autumn, though they are hollow when shed
and with a persistent core as in the ox and goat. It crops
grass, not, like the deer, eating leaves of trees and shrubs ;
" in fleetness it excels all other quadrupeds of our conti-
nent," though it is short winded, and does not run a great
distance (Caton). In its horns, hollow when cast off, and the
gall bladder, which is absent in the Cervidce, the prong-honi
GIG
ZOO LOU Y.
onnng
connects the deer family with the Bovidce, represented by
the sheep, goat, antelope, gazelle, and ox.
The domestic sheep (Ovis (tries Linn.) is not a natural
speck's, but an association of races whose specific origin is
obscure. Some authors regard the turf sheep of the stone
age of Europe as the ancestor of the domestic sheep, as forms-
like it are now living in the Shetland Isles and in Wales.
^j
It was of small size, with slender limbs, and erect, short
horns. This sheep was supplanted by a curved, large-horned
form, the modern domestic sheep. This latter form is pos-
sibly the descendant of the Ocis argali Pallas, of Asia, which
in North America is represented by the Ovis montana Cuvier,.
the Eocky Mountain sheep or big-horn (Fig. 530), still com-
mon on the less accessible summits along the upper Missouri
and Yellowstone Rivers, as well as the mountains of Wy-
and Montana.
In the same, though
higher and more inac-
cessible situations lives
the rare mountain
goat, Aploceros monta-
nus Richardson, whose
horns are jet black and
polished, slender and
conical, like those of
the Swiss chamois. It
is found sparingly in
the higher summits of
the Rocky Mountains
and the Cascade range ;
an individual has within a few years been shot on Mount
Shasta, California. Passing by the gazelles and true an-
telopes we come to another characteristic American an-
imal, the musk sheep (Ovibos moschatus Blainville,
Fig. 531), now confined to the arctic regions. A closely
allied species, Ovibos prisons of Rutimeyer, formerly during
the post-glacial period existed in England. France, and Ger-
many. Closely allied to the musk sheep is a fossil form
(Bootherium of Leidy) which is regarded by Rutimeyer and
Fig. 529. —Horns at different ages of the Pron.tr-
liorn Antelope, showing the hollow structure of
the horn when shod. — After Hay-.
THE BISON.
611
others as a musk sheep (Orib<>* /iriscus Riitimeyer). If this
is the case the musk sheep, or a species closely allied to it,
formerly extended to the Middle States at or near the close
of the glacial period.
We now come to the bison and ox. The American bison
Fig. 530.— Rocky Mountain Sheep or Big-Horu.— From Brelun's Thierleben.
(Bison Americanus Gmelin) formerly ranged from Virginia
and Lake Champlain to Florida, and westward from the
northern limit of trees to the Rocky Mountains and eastern
Mexico. It is now in danger of extermination, being mainly
restricted to a few herds on the plains. It is closely
612
ZOOLOGY.
allied to the European bison, (Bison Europceus Owen), the
"auroch," now preserved in the forests of Bialowicza, and
living wild in Caucasus. Bos primigenius Bojanus, which
in the time of Caesar lived in Germany and England bear-
ing the name "urns," is the " ur" of the Nibelungen
song. From it has descended the half-wild cattle in certain
THE OX AND ITS VARIETIES.
613
English parks, also certain large domestic races, such as the
Holstein and Friesland breeds. From another fossil species
(Bos longifrons Owen) arose the so-called brown cattle of
Switzerland, and the "runts" of the Scottish Highlands.
Still other domestic races are traced back to another fossil
I
re"
I
I
I
o
o
quaternary species, Bos frontosus Nilsson. Our present
races of domestic cattle, however, do not represent a genuine
species, but a number of races which have descended from
several fossil species ; the name Bos taurus (Fig. 532) is
simply, then, a conventional name (Cams' Zoologie). The
bison is known to breed with cattle in the Western States,
614
ZOOLOGY.
though whether the hybrids thus produced are fertile or not
is unknown.
The ox is succeeded by the giraffe, with its long neck,
which makes it the tallest of all quadrupeds.
The last family of Ungulates, the Cmnelidce, comprises the
camels of the Old World, and the llama and vicuna of South
America. In former (Tertiary) times a llama-like animal
inhabited the Pacific coast to Oregon. In the camels the
upper lateral incisors are present ; the stomach is less
distinctly divided into four chambers, the third stomach, as
such, is wanting., though the second stomach has the deep
cells, which suggested the fable that the camel stores up a
supply of water in its stomach for its march over deserts
Fig. 533.— Skull of Lion.
The toes have very large, thick pads, while the hoofs are
reduced to nail-like proportions.
Order 11. Carnivora (Ferce}. — The bear, cat, tiger, and
lion recall the leading forms of this order. The skull is
massive, though the head is small or of moderate size ; the
teeth are all well developed, especially the canines ; the mo-
lars usually have two or three roots, and the feet have large
claws. The stomach is simple. The cerebral hemispheres
of the lower carnivores have usually but three distinct con-
volutions, while the latter are much more numerous and
complicated, the brain itself being broader, in the aquatic
forms (Pinnipedia}. The group is divided into two sub-
orders, i.e. the Pinnipedia or seals, and the land species (/7\-
sipedict). In the former group the feet are webbed, the toes
13
Tig. 533a.— Side view of the cat's skull, the lower jaw and hyoid bone (th, t*) being detached, a
alisphenoid bone; ae, external auditory canal; a?-, ascending ramus; 6, auditory bulla; c, occipita
condyle; /, frontal; ip, interparietal; j, malar or jugal; la, lachrymal; m, maxilla; ms, mastoid pro
cess; n, nasal; os, orbito-sphenoid; p, parietal; pa, palatine; pt, pterygoid; pm, premaxilla; a
squainosal; so, supraoccipital; z, zygoma; 2, iufraorbital foramen ; 6, optic foramen.— After Mivart
Fig. 533d.— Claws of the cat or tiger.
A, claw held back by the strong liga-
ment I; B, claw pulled forward by the
tendon t being drawn back so that I is
Stretched out.
Fig. 5336.— Side view of cat's brain. F, frontal lobe; T, tem-
poral lobe; ol, olfactory lobe; in, medulla oblongata; c6, cere-
bellum; v, pons Varolii; S, sylvian fissure. — After Mivart.
Fig. SSSc.-y-Cat's brain seen froi
above, showing the deep longitudim
fissure dividing the two hemisphere
and the cerebellum behind them, c
crucial furrow; s, superior, m, middli
j', inferior, external gyms; v, verm
form process of cerebellum; ol, olfai
tory lobe.— After Mivart.
[To face page 614.]
BEARS AND THEIR ALLIES.
615
being connected ; the wrist and foot only projecting beyond
the ekin of the body, and there are no external ears, or only
small ones.
The walrus (Fig. 534), the seals, and the eared seals or
sea-lions (Otariidcs)
are the types of the
aquatic Carnivores ;
the sea-lions can walk
on all fours, and in
certain peculiarities of
the skull they resem-
ble the bears.
Of the terrestrial,
normal Carnivora, the
raccoon, coati, Cerco-
leptes, and bear, to-
gether with a number
of extinct forms, are
the more generalized
or lower types. They
are plantigrade, and
while standing at the
base of the carnivorous
series, have some fea-
tures suggesting and
anticipating those of
the lemurs, and mon-
keys. The raccoon,
Procyon lotor (Linn.),
abounds throughout
the United States. Al-
lied to it is the coati
(Nasud) of Central
America, a creature
about the size of, and
with the general hab-
its of the raccoon, being an exceedingly knowing and mis-
chievous animal. A number of extinct Eocene mammals
are also allied to a small plantigrade, long-tailed carnivore,
Cercoleptes, which resembles the Pri unites in its two cutting
616
ZOOLOGY.
p re-molars and three true molars ; while the rami of the
mandible are coossified ; for these reasons it was placed
by F. Cuvier between the orders Carnivora and Primates
(Cope). It is allied to the raccoon, is called the kincajou,
and lives in northern South America.
The bears have a thick, clumsy body, with a rudimentary
tail, and the teeth are broad and tuberculated, so that thev
can live indifferently on fish, insects, or berries. Our North
American species are the polar bear ( Ursus maritimus
Linn.) and Ursus arctos Linn., with its varieties of brown,
Fig. 535.— Skeleton of the Polar Bear, showing the plantigrade feet. 51, scapula ;
53, hnmerus; 54, radius; 55, ulna; 62, ilium : 63, isrhium; 65, femur; 66, tibia; 67,
fibula ; cl, calcareum ; C, cervical vertebra.— After Owen.
cinnamon and grizzly bears ; and the true black bear, Ursus
Americanus Pallas.
The bears are succeeded by the Mustelida, or the otter,
skunk, badger, wolverene, weasel, mink, ermine, etc., nearly
all of which are valuable for their furs.
The dog family (Canidce) is represented by the fox, wolf,
and dog. The gray fox (Urocyon Viryitiunnis Erxleben) the
common red fox ( Vulpes vulgaris Fleming), with its varie-
ties, the cross, silver, and black fox, as well as the wolf
(Canis lupus Linn.), are valuable for their furs. The wolf
is mostly gray northward, becoming "southward more and
I
THE SPECIES OF DOGS AJ\'D CATS. 017
more blackish and reddish, till in Florida black wolves pre-
dominate, and in Texas red ones." (Jordan's Manual of
Vertebrates.) The prairie wolf or coyote (Can is latrans
Say), is characteristic of the Western plains and Pacific coast.
The Indian dogs breed with the coyote, and the offspring is
fertile. (Cones.) This fact appears to support the theory
that the domestic dog (with its conventional name Canu
fattiiUurix Linn.) is a descendant of the wolf. On the other
hand, Fitzinger in his "Researches on the Origin of the
Dog," states that fourteen kinds of dogs can be distinguished
ill the Roman and Greek records ; of these he considers five
to be principal types or species, five others climatic varieties,
the remainder being either breeds artificially produced or
hybrids. As regards the Egyptian dogs, seven kinds may be
distinguished, besides the jackall, three of them being dis-
tinct species. He believes that wolves, jackalls, foxes, etc.,
are species quite distinct from the domestic dog ; they
may have interbred with the latter, and thus influenced cer-
tain breeds ; but they are not the parents of the domestic
dog. He concludes that there are seven species among our
dogs : — C. domesticus, extrarius or spaniel and Newfound-
land dogs, vertagus or badger dog, sagax or hound, molossus
or bulldog, Icporarius or greyhound, and the naked dog,,
C. caribcBHs. Among half-wild dogs is the dingo or hunt-
ing-dog of Australia, which goes in packs.
The Viverra and Genetta or civet cats, and the hyaenas
lead to the cat family, which stands at the head of the Car-
nivora. The panther, leopard, tiger, and lion belong to the
genus Felis. The Fells concolor Linn., cougar or puma,
ranges over both continents; it is 1-1-3 metres in length.
The domestic cat, Fells domestica Linn., was first domes-
ticated in Egypt, the Greeks and Romans not possessing
it ; the cat and common marten were in use as domesticated
animals side by side ; and at the same time in Italy, nine
hundred years before the crusades. It appears that the do-
mestic cat of the ancients was Mustela foina (Rolleston).
Of the lynxes there are two species in North America,
Lynx rufus Rafinesque, the American wildcat, and the
Canada lynx, Lynx Canadensis Rafinesque, the latter being-
much the larger species.
018 ZOOLOGY.
Order XII. Primates. — The last and highest order of
mammals contains a series beginning with creatures resem-
bling squirrels and bats, i. e., the lemurs, and comprising
monkeys, apes, and ending with man. In all the Primates,
the legs are exserted almost or quite free from the trunk,
with the great toe of the hind foot usually enlarged and op-
posable to the others ; nails, except in the marmosets, replace
claws ; the teeth are usually of the following formula :
with one exception canine teeth are always present ; the pre-
O _ 0 Q _ O
molars are usually = ~, but in the American monkeys 5^5.
• <J — £ « o — o
The hemispheres of the brain may in the lower forms be
quite smooth, but in all there is a well-developed " calcarine
furrow," giving rise to a "hippocampus minor" within the
posterior cornu of the ventricle, by which the posterior lobe
of the cerebrum is traversed (Flower). The collar-bones
(clavicles) are for the first time in the series well developed.
The placenta is also different in shape from that of other
mammals, being disk or cake-like, but in lemurs it is "diffuse/'
The Primates are divided into two sub-orders, i, e., the
Prosimice and Antliropoidea. The former group embraces
the lemurs, which vary in size from that of a rabbit to a
large monkey. They are covered, the face as well as the rest
of the body, with a dense fur ; walk on all-fours, usually
have long tails, though the lori is tailless, while the fore
3imbs are shorter than the hind limbs. The skull is small,
flattened, and narrow in front ; the brain-cavity small in
proportion to the rest of the skull, i. e., the face compared
with the monkeys. The cerebral hemispheres are small and
flattened, the frontal lobes narrow and pointed, and behind
they only slightly cover the cerebellum.*
By some authors the lemurs are separated from the Pri-
mates, the Insectivora and Cheiroptera being placed between
the Prosimice and the other Primate*. They have characters
in which they resemble Insectivora, Rodentia, and Carnivora,
but the weight of organization, or the sum of their charac-
ters, ally them nearest to the monkeys. They are therefore
essentially a generalized or ancestral type. Kecent discov-
* In Hapalemur the single pair of teats are situated on the arm.
THE PRIMATES. 619
eries have led to the hypothesis, that from still older, more
generalized types, four lines of development, respective! \
culminating in the typical Carnivores, Cetaceans, lemurs, and
monkeys, have taken their origin. That the lemurs, though
now restricted to Madagascar, eastern Asia, and South
Africa, were preceded by still more generalized types on the
American Continent, is indicated by the discovery of fossil
bones in the Eocene beds of the Rocky Mountains, referred
"by Marsh and Cope to the Primates; Marsh stating that
the principal parts of the skeleton are "much as in some of
the lemurs."
Allied to the true lemurs is a very puzzling creature, the
aye-aye or Cliironnjs, of Madagascar, whose dentition differs
from that of all other Primate*, and resembles that of the
.Rodents ; the thumb also is not truly opposable, and all the
hind digits, except the great toes, have claw-like nails. The
Gautyo, of West Africa, somewhat recalls the Insectivorat
while " in the more active and flexible-bodied Lemuridce,
the trunk-vertebrae resemble in proportions, connections, and
direction of neural spines those of the agile Carnivora."
(Owen.)
The genuine Primates or suborder Anthropoidea are, in
biief, characterized by the large, convoluted cerebral hemi-
spheres which nearly, or in the higher apes and man, conceal
the cerebellum when seen from above. * The ears are rounded,
with a distinct lobule, and the two mammas are pectoral.
These Anthropoidea are divided into two subdivisions, the
first comprising the monkeys and apes, and the second, man.
In the first group (tiimi.m), the body is prone, the animal
walking on all-fours, only the orang and gorilla walking
partly erect ; the great toe is rather short, thumb-like, and
opposable to the fingers, while the body is very hairy. The
monkeys of the New World have a wide septum to the nose,,
and are hence called PlatyrhincB ; they also have long tails.
The little, squirrel-like, gregarious marmosets are the small-
est of the monkeys and nearest allied to the lemurs. They
walk on all -fours, the anterior extremities being like the
* In the low Uapale and Gebus, however, the cerebrum projects,
backward as far or even farther than in man (Gill).
620 ZOOLOGY.
hind feet, and resting on the same plane, serving as a paw ;
the teeth are sharply tubercled, and the nails, except those of
the great toe, are claw-like. The cerebral hemispheres are
nearly smooth, though relatively large. Jacchus and Mhlax
are the typical genera, inhabiting South America. While
the marmosets (Mid idee) have but thirty-two teeth, in the
true platyrrhine monkeys there are thirty-six teeth ; there
beiuo- an additional molar on each side of each law. and the
O f
thumb is slightly opposable to the fingers (though a true
thumb is wanting in the spider monkeys). The New World
monkeys also have long prehensile tails, so useful in climb-
ing as to be sometimes called a fifth hand, as seen in the
spider monkeys (Ateles), in which the tail underneath is
naked and very sensitive. The skull varies greatly in the dif-
ferent genera, as does the brain, which in Ckrysothrix, etc.,
is nearly smooth, while in Ccbus the hemispheres are nearly
as much convoluted as in the catarrhine apes. (Huxley.)
The monkeys of the Old World mtergrade with the apes,
and are thus more specialized or highly developed than
those of the New World. The septum of the nose is narrow,
hence they are said to be catarrh ine or thin-nosed, while the
tail is short and not prehensile.
The catarrhine monkeys (Cercopitliccida'} walk on all-
fours ; the body being horizontal or prone ; they have thirty-
two teeth, as in man, though the canines are large and
sharp ; the thumb is well developed, and they are truly
quadrumanous ; the skull has a comparatively large facial
angle, and the hemispheres of the brain are well furrowed.
They have highly-colored, naked callosities over the ischiatic
bones, and cheek-pouches for the temporary reception of
the food. Of the baboons, with their dog-like muzzles and
short tails, the mandrills are the most noticeable, with their
white beards, scarlet lips, and blue cheeks ; they are less
arboreal than the macaques of Asia, running about over
rocks on all-fours. The common monkeys of menageries
are the macaques (Macacus) of India. All the foregoing
catarrhine monkeys have a simple stomach, as in man, but
in the sacred monkey of India (Semnopithecus) and the
African thumbless Colobns, the stomach is more complex,
and there are no cheek pouches.
Fig. 5356.— Head of Cebus vel-
lerosus.
Fig. 535c.— Head of Semnopithe-
cus cornutus. — After Darvviu.
Fig. 535a.— Qalago. From Lutken's Zoology. Fig. 535<<.— Orang-outang or Mias.— Afi.-r
Liitken.
[To face page G-'O.]
vmtf i ft
lJW'v \
i, ^ '\
li"1 '
THE MONKEYS AND APES.
621
Fig.
The
The apes live in trees, only occasionally walking on the
ground ; their posture is semi-erect ; they are tailless, the
fore legs are much longer than the hind legs, and used as
arms, the radius being ca-
pable of complete prona-
tion and supination. In
the form of the skull, of
the brain with its convolu-
tions, and in the teeth,
there is a still nearer ap-
proach to man.
There are three typical
forms or genera of apes,
i.e., the gibbon (Hylobates,
Fig. 536) ; the orang (Mi-
mcti'x jntlieci(s) and chim-
panzee (M. niger,
537), and the gorilla.
gibbons are nearest to the
monkeys; they are little
less than a metre (3 feet)
in height, and are very
slender, with very long
arms, so that they are rapid,
agile climbers, also run-
ning over the ground with
ease and rapidity ; when
standing erect the fingers
touch the ground ; only
the thumbs and great toes
have true nails, in all the
higher apes the nails of all
the digits being flattened ;
the spinal column is nearly
straight ; they have four-
teen pairs of ribs and
eighteen dorso-lumbar ver-
tebrae, there being in the other apes usually seventeen, as in
man. The siamang lives in the forest of Sumatra ; others
inhabit Java, Borneo, Cambogia, etc.
Fig. 53fi.— Skeleton of Siamang Ape, a gib-
bon.—After Owen.
622
ZOOLOGY
The orang-outang is 1-38 metres (4-4£ feet) high ; it
twelve pairs of ribs, the same number as in man ; the arms
are very long, reaching the ground, so that in walking they
rest on their knuckles, swinging the body through their long
arms as if Avalking on crutches ; their posture is only par-
tially erect. The forehead is less strongly marked than in
Fig. 537.— The Chimpanzee, variety Tshego. — From Brehm's Thierleben.
the other apes, showing better the shape of the skull. The
volume of the brain, both of the orang and chimpanzee is
about twenty-six or twenty-seven cubic inches. The follow-
ing table will show, according to "\Vyman, the relative
capacity of the skull in the different apes as compared with
man :
Fig. 537a.— Young Chimpanzee. —After Hartmann.
[To face page 622.]
"~* - . T" "• n
Fig. 5376. — Aged Male Gorilla. — After Harfmann.
[Tt> fiii'i- /»(;/(• 6*33.]
CHIMPANZEE AND GORILLA. 623
The average capacity of the Caucasian skull is 92 cubic inches.
" " Australian " 75
" " Gorilla 29 to near 35
cubic inches.
« " Chimpanzee " 26
" " Orang " 25 "
According to Wyman, the range of variation in different
races of men, as seen in seventeen skulls, is from 92 to 75
cubic inches ; in the gorilla from 34 to 25 cubic inches, nine
skulls having been measured. There is but a single species
of orang, which is restricted to Sumatra and Borneo. It is
said to be very intelligent, to possess a voice so loud as to be
heard one or two miles, and to build a nest to sleep on.
The chimpanzee .and gorilla are only found on the west
coast of Africa. The chimpanzee (Mimetes niger Geoffrey
with its variety Tscliego, Fig. 537) inhabits the coast from
Sierra Leone to Congo. It is about 1-j metres (5 feet) in
height. It can stand or run erect, but it usually leans for-
ward, resting on its knuckles ; the arms span about half as
much again as the creature's height. Both the chimpanzee
and gorilla have fourteen pairs of ribs. The chimpanzee lives
on fruit, is an active climber, and nests in trees, changing its
rude quarters according to circumstances. Kev. Dr. Savage
states that "they generally build not far above the ground.
Branches or twigs are bent, or partly broken, and crossed,
and the whole supported by the body of a limb or a crotch.
Sometimes a nest will be found near the end of a strong
leafy branch twenty or thirty feet from the ground."
The gorilla, like the chimpanzee, goes in bands, but the
company is smaller, and led by a single adult male. They
make similar nests, which, however, in the case of both apes,
afford no shelter, and are only occupied at night. The
gorilla sometimes reaches the height of about 1^- metres (5^-
feet) and weighs about 200 pounds. Its ordinary attitude is
like that of the chimpanzee ; there is a web between the first
joints of all the fingers and three of the toes, and both hands
and feet are broader, while the body is much more robust
than in the other apes, being very broad across the shoulders.
The span of the arms is to the height as three to two, or a
little over eight feet. The skull is thick, and the strength
624 ZOOLOGY.
and ferocity of the creature is evinced by the thick supra-
orbital ridges and the high sagittal and lambdoidal crests on
the top of the skull ; the face is wide and long, the nose
broad and flat, the lips and chin prominent. The gorilla
walks like the chimpanzee, though it stoops less. It is very
ferocious, bold, never running when approached or attacked
by man. It lives on a range of mountains in the interior of
Guinea, its habitat, so far as known, extending from a little
north of the Gaboon River to the Congo.
Tints, to recapitulate, while the gibbons are most remote
from man, the orangs approach him nearest in the number
of the ribs, the form of the cerebral hemispheres, and other
less obvious characters ; the chimpanzee is nearest related to
him in the form of the skull, the dentition and the propor-
tions of the arms, while the gorilla resembles him more in
the proportions of the leg to the body, of the foot to the
hand, in the size of the heel, the curvature of the spine, the
form of the pelvis and the absolute capacity of the skull
(Huxley). Anatomists have and do differ as to whether the
chimpanzee or the gorilla is nearest to man.
The question whether man (Homo sapiens Linn. ) considered
simply as an animal, is the representative of a distinct sub-
class, order, suborder or family, is and may never be settled ;
though the tendency among zoologists is to leave him among
the Primates, where he was placed by Linnaeus. When we
consider the slight absolute anatomical differences separating
man from the apes, and take into account the great variation*;
in form between the different genera of apes, and still more-
in the monkeys, it seems best, throwing out, as we have to
do in a purely zoological classification, the intellectual and
moral faculties of man, to adopt the view that man is
the representative of a group of Primates.* The absolute
differences of man from the apes consist in the greater num-
ber and irregularity of the convolutions of the cerebral hemi-
•'&•
* Geoffrey St. Hilaire placed man in a kingdom by himself ; Owen
assigned him to a subclass ; by others he is generally regarded as a
representative of an order Bimana, as opposed to the order Quadru-
inana, or monkeys and apes; while from recent comparative studies
man is considered as belonging either to a separate subo-der or a fam-
DIFFERENCES OF MAN FROM THE APES
spheres, which are also much larger compared with the cere-
bellum, and completely cover the latter ; the entire brain
being at least double the size proportionately of that of the
gorilla ; * it is also stated that two muscles exist in man
which have not yet been found in any ape, the extensor primi
inter notlii potticis and the peroimus tertius, belonging to the
thumb and foot respectively (Huxley). \ There are also points
in the origin of certain muscles which are peculiar to man, but
Huxley adds that all the apparently distinctive peculiarities
of the muscles of the apes are to be met with, occasionally,
as varieties in man. On the other hand, the relative differ-
ences of the skulls of the gorilla and man are, as Huxley
states, "immense." In man the cranial box overhangs the
orbits ; in the gorilla the forehead is hollowed out. The
hinder portion of the brain is also much more developed in
man than in the apes, and in the hinder part of the hemi-
spheres the convolutions are more numerous than in the
chimpanzee, this part in monkeys losing its convolutions
altogether (Wyman). Man stands erect ; his arms span a
distance equal to his height ; the spinal column has four
curves ; the skin of the hands and feet of man is highly
sensitive, compared with that of the apes. Finally, as Cuvier
stated, the grand distinctive zoological character separating
man from the other animals is the possession of the power of
speech.
Sometimes in man the coccyx has one or two more joints
than the normal number, but the apes have no tail ; though
the human embyro, like other young animals, has a tail,
* " It must not be overlooked, however, that there is a very striking-
difference in absolute mass and weight between the lowest human
brain and that of the highest ape — a difference which is all the more
remarkable when we recollect that a full-grown gorilla is probably
pretty nearly twice as heavy as a Bosjes man, or as many an European
woman. It may be doubted whether a healthy human brain ever
weighed less than thirty-one or two ounces, or that the heaviest gorilla
brain has exceeded twenty ounces." In another place Huxley states
that " an average European child of four year's old has a brain twice
as large as that of an adult gorilla." — Man's Place in Nature.
t Dr. Chapman has found in the arm of a gorilla a distinct extensor
primi internodii pollicis muscle, but no trace of the flexor longus polli-
c.i*.— American Naturalist, June, 1879. p. 395.
626
ZOOLOGY.
though as observed by His, it does not contain any vertebrae,
and is thus not like the tail of other embryo mammals. The
black and Australian races are slightly nearer the apes than
civilized peoples. In apes, as in the lower mammals, the pel-
vis is higher than wide ; when there is a degradation in the
human pelvis it tends to become higher than wide, as seen in
the pelvis of the Hottentots. In civilized man the legs are
one half the height of the body, but in the South African,
Hottentot, and Bushman the legs are a little less than half
the height, and the thigh bone is flattened from side to side,
as in the gorilla. The waist is broader in the African than
in the European ; the os calcis is not longer in negroes than
in the white man, the larger heel of the former being simply
due to an expansion of the
soft parts.
The form of the skull va-
ries greatly in the different
races, and even in individ-
uals of the same race of
mankind. This is seen in
the difference of the facial
Fig. 538.-Skuii of a Negro, showing its angle. This is obtained by
prognathism.-After Owen. drawing a line from the
occipital condyle along the floor of the nostrils, and inter-
secting it by a second, touching the most prominent parts
of the forehead and upper jaw ; the angle they make is
an index of the cranial capacity, and of the degree of in-
telligence of the individual. The facial angle in the reptiles
is very slight, as it is in the birds ; in the dog it is 20°, in the
gorilla 40°, in the Australian 85% in the civilized Caucasian
it averages 95°, while the Greek sculptors adopted an ideal
angle of 100°. (Owen.*) When the lower part of the face
protrudes, as in the negro, the face is said to be prognathous
(Fig. 538) ; where the facial angle is high, and the face
straight, as in the more intellectual forms, the cranium is
* Pagenstecher states that the facial angle in the Caucasian Euro-
pean is 80°-85°, and even over 90° ; in the Mongolians 75°-80° ; in
negroes 70°-75° ; in the tribe of Makoias in South Africa 64° ; in the
tribe of Tikki-Tikki, or Akka negroes, the dwarfs described by
Schweinfurth, only 60°. — Allgemeine Zoologie, i., p. 250.
TEE VARIETIES OF MAN. 627
said to be orthognathous. Those skulls which are high and
narrow, i.e., with the longer diameter to the shorter, as 100
to 05, are said to be dolichocephalic, while those with the
diameters as 100 to 85 are railed fir achy cephalic, but these dis-
tinctions have been found to be quite arbitrary.
The classification of the human races is in as an unsatis-
factory state as that of the domestic animals. Naturalists
are now agreed that there is but one species of man. Blu-
menbach, from the shape of the skull and the color of the
skin, divided mankind into three varieties, the white or Cau-
casian, the brown or Mongolian, and the black or Ethiopian.,
considering the American variety as connecting the Caucasian
and Mongolian, and the Malayan as intermediate between
the Caucasian and Ethiopian. Hamilton Smith divided
man into three varieties, Caucasian, Mongolian, and Tropi-
cal ; Latham, also, into three, Japetidse, Mongolidae, and
Atlantidre ; and Pickering into white, brown, and black
varieties, with intermediate races. Huxley divides the dif-
ferent races into two primary groups, the Ulotriclii, with
crisp or woolly hair, and the Leiutriclii with smooth hair.
The average height of Englishmen is 5-8-5-10 feet ; in
the universities more. In America, the average height of
medical and military men is 5-9f feet. The Patagonian men
are nearly six feet high on an average; the women 5-10 feet;
the Bushman and Esquimaux 4-7, the latter being the small-
est people on the earth. The smallest dwarfs in Europe
were 33 and 28 inches in height respectively ; while Pat-
rick Cotter, the Irish giant, was 8 feet 7 inches tall.
It is claimed by some naturalists that man has descended
from some generalized type of animal which gave rise to
several series of forms culminating in the monkeys, apes,
and man respectively, and by others that he is a direct
descendant of forms like the chimpanzee or gorilla ; but
it is probable that from the want of sufficient data,
the question as to the origin of man can never be def-
initely settled. Setting hypothesis aside, in ascending
the mammalian series, we have seen in the forms lead-
ing from the extinct Eocene generalized types of Ed-
ucdbilia to the Carnivora and Primates., a tendency to
an extreme specialization of those parts ministering to the.
€28 ZOOLOGY.
intellectual behests of the creature. On the other hand, in
all general points, man's limbs are those of the primitive
type so common in the Eocene Period. As Cope remarks :
"He is plantigrade, has live toes, separate carpals and tar-
sals ; a short heel, rather flat astragalus, and neither hoofs
nor claws, but something between the two. The bones of
the fore arm and leg are not so unequal as in the higher
types ; and remain entirely distinct from each other, and the
ankle joint is not so perfect as in many of them. In his
teeth his character is thoroughly primitive. He possesses, in
fact, the original quadrituberculate molar with but little
modification. His structural superiority consists solely in
the complexity and size of his brain."
Whether man in common with other animals is the result
of divinely ordered processes or biological laws, appearing at
the head of a long series of forms, and, as probably many
other animals have, with comparative suddenness, being at
the outset in all essential respects man, though a savage, and
not with a long pedigree of morphologically impossible Dar-
winian "missing links,"-— whether he thus originated, or by
.an independent creative act, the result is a being concerning
whom the fact that he is physically an animal, is after all the
least important characteristic of the nature of him who is
the historian of his own and other species ; who is capable
•of studying and in a degree comprehending the universe in
which he lives, and who whatever his physical origin may
have been, has intellectual, moral, and spiritual capabilities
which render his nature susceptible of endless improvement,
endowing him with immortality and all that it involves.
CLASS VIII. — MAMMALIA.
Body covered with hair ; young nourished with milk secreted in mam-
lower jaw articulating directly with the skull, the quadrate bone be-
coming one of the ear-bones (malleus) ; a diaphragm dividing the body-
cavity into thoracic and abdominal portions ; heart with the aorta reflect-
ed over the left bronchus; blood-corpuscles non-nucleated; brain large,
especially the cerebral hemispheres ; viviparous; uterine gestation.
Subclass I. Ornithoddphia. — Order Monotremata. — Urinary and gen-
ital outlets opening into the cloaca. Laying large eggs
(Echidna, Ornithorkynckus).
CLASSIFICATION OF MAMMALS. 629
Subclass II. Didt'lphia. — Order Marsitpialia. — Mammals with a mar-
supium and bones supporting it. (Macropus, Didelphys.)
Subclass III. Monodephia. — Placental mammals.
Super-order I. Ineducabilia. — Brain with a relatively small,
smooth cerebrum.
Order 1. Bruta. — Incisors absent; sometimes toothless.
(Bradypus.)
Order 2. Glires. — Rodents, incisors large. (Sciurus.)
Order 3. Insectivora. — Fore limbs often peculiarly adapted
for burrowing ; molars with conical cusps. (Scalops.)
Order 4. Chiroptera. — Fore limbs adapted for flight. (Ves-
pertilio.)
Super-order II. Edvcabilia.- Brain with a relatively large, con-
voluted cerebrum.
Order 5. Cet\ — Cetaceans; fish-like in form, no hind
limbs. ^Balaena.)
Order 6. Sirenia. — FisTi-like in form, but wit'fi ascending
rami to the lower jaw ; teeth ruminant-like. (Mana-
tus.)
Order 7. Proboscidea. — Snout prolonged into a proboscis.
(Elephas.)
Order 8. Hyracoidea. — Long curved incisors ; feet with
pads; toes encased in hoofs. (Hyrax.)
Order 9. Toxodontia. — Extinct forms, with well developed
incisors. (Toxodon.)
Order 10. Ungulata. — Ungulates ; toes encased in hoofs.
(Equus, Bos.)
Order 11. Carniwra. — Teeth pointed; claws large. (Felis,
Canis.)
Order 12. Primates. — Brain with cerebrum nearly or quite
covering the cerebellum ; nails usually present ; body
quadrupedal, quadrumanous, or erect and bimanous.
(Cebus, Gorilla, Homo.)
Laboratory Work.— All the craniate vertebrates may be dissected in
the same general manner, either under water in pans, or, if large, upon
the dissecting table. The necessary tools are a scalpel, forceps, scis-
sors, and tenaculum or hook for suspending the specimens or portions
630
ZOOLOGY.
of large subjects for better facility in dissecting. A small sharp-
pointed narrow-bladed scalpel, besides a large one, curved, as well as
sharp-pointed scissors are useful, with a German silver blow-pipe
for temporarily distending vessels; and also a blunt-pointed copper
wire or probe made for surgeon's use, will be necessary. All these in-
struments, put up in a compact box, can be purchased at the surgical
instrument maker's, as well as syringes for injecting the circulatory
organs and vascular parts of the viscera.
TABULAR VIEW OF THE EIGHT CLASSES OF VERTEBRATES.
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SUB-BRANCH III.— CRANIOTA.
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SUB-BRANCH II. — ACRANIA. I. LEPTOCARDII (Lancelet).
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SUB-BRANCH I.— UROCHORDATA. I. TUNICATA.
CHAPTER IX.
COMPARATIVE ANATOMY OF ORGANS.
HAVING studied the morphology of animals in a system-
atic way, it will be well for the student to make a brief re-
view of those facts stated in the foregoing chapters bearing
on the origin and successive degrees of complication of the
most important organs.
Organs of Digestion— The Mouth and Teeth. — The most
important organs in the animal system are those relating to
digestion, as an animal may respire solely through its body-
walls, or do without a circulatory or nervous system, but
must eat in order to live and grow. The opening by which
the food is taken into the alimentary canal is called the
mouth, whether reference is made to the " mouth" of a
hydra or of a vertebrate ; although the structure of the edges
may differ radically, still in all Metazoa the mouth is due to
an inpushing of the ectoderm, however differently the
edge of the mouth may be supported and elaborated. The
edges of the mouth are usually called the lips, but true lips
for the first time appear in the Mammalia. The trituration
or mastication of the food is accomplished among the in-
vertebrates in a variety of ways, and by organs not always
truly homologous.
Hard bodies serving as teeth occur for the first time in the
animal series in the sea-urchins, where a definite set of cal-
careous dental processes or teeth (Figs. 78 and 79), with solid
supports and a complicated muscular apparatus, serves for
the comminution of the food, which consists of decaying an-
imals and sea- weeds. In those Echinoderms which do not
have a solid framework of teeth, the food consists of minute
forms of life, protozoans and higher soft-bodied animals.
632 ZOOLOGY.
or the free-moving young of higher animals, which are
carried into the mouth in currents of Avater or swallowed
bodily with sand or mud.
Among the worms true organs of mastication for the first
time appear in the Rotatoria (Fig. 122), where the food, such
as infusoria, etc., is crushed and is partly comminuted by
the well-marked horny or chitinous pieces attached to the
mastax. In most other low worms the mouth is unarmed.
In the leeches there are three, usually in the annelids two.
denticulated or serrate, chitinous flattened bodies situated
in the extensible pharynx of these worms, and suited for
seizing and crushing their prey.
In the higher mollusks, such as the snails (Cephalophora)-
and cuttles, besides broad thin pharyngeal teeth, compara-
ble with those mentioned as existing in the worms, is the lin-
gual ribbon already described (p. 276, Fig. 215), and admira-
bly adapted for sawing or slicing sea- weeds and cutting
and boring into hard shells, acting somewhat like a lapi-
dary's wheel ; this organ, however, is limited in its action,
and in the cuttles the jaws, which are like a parrot's beak,
do the work of tearing and biting the animals serving as
food, which are seized and held in place by the suckered
arms.
In the crustaceans and insects we have an approach to-
true jaws, but here they work laterally, not up and down or
vertically, as in the vertebrate jaws ; the mandibles of these
animals are modified feet, and the teeth on their edges are
simply irregularities or sharp processes adapting the mandi-
bles for tearing and comminuting the food. It is generally
stated that the numerous teeth lining the crop of Crustacea
and insects (Fig. 282) serve to further comminute the food
after being partially crushed by the mandibles, but it is now
supposed that these numerous points also act collectively as
a strainer to keep the larger particles of food from passing
into the chyle-stomach until finely crushed.
The king-crab burrows in the mud for worms (Nereids,
etc.) ; these may be found almost entire in the intestine,
having only been torn here and there and partly crushed by
the spines of the base of the foot-jaws, which thus serve
COMPARATIVE ANATOMY OF ORGANS. 633
purpose effected by the serrated edges of the mandibles of
the genuine Crustacea and insects.
Among vertebrates, the lancelet is no better off than the
majority of the Ccelenterates and worms, having no solidl
parts for mastication ; and we have seen that the jaws and
teeth of the hag-tish and even the lamprey eel form a very
different apparatus from the jaws and its skeleton in the
higher vertebrates ; and that, even in the latter, the bony
elements differ essentially in form in the different classes,
though originating in the same manner in embryonic life.
In the birds we have seen that the mandible and maxilla are
encased in horny plates, that true teeth are remarkably ex-
ceptionable, the gizzard being, however, provided Avith two
hard grinding surfaces ; on the other hand, mammals with-
out teeth are exceptionable.
The teeth of fishes are developed, not only in the jaws,
but on the different bones projecting from the sides and
roof of the mouth, and extend into the throat. In many
cases, in the bony fishes, these sharp recurved teeth serve to
prevent the prey, such as smaller fish, from slipping out of
the mouth. On the other hand, the upper and lower sides;
of the mouth of certain rays (Myliobatis) are like the solid
pavement of a street, and act as an upper and nether mill-
stone to crush solid shells.
In the toothless ant-eaters the food consists of insects,
which are swallowed without being crushed in the mouth ;
true teeth in the duckbill are wanting, their place being
taken by the horny processes of the jaws, while in Steller's
manatee the toothless jaws are provided with horny solid
plates for crushing the leaves of aquatic succulent plants.
Examples of the most highly differentiated teeth in verte-
brates are seen in those animals, like the bear, whose food is.
omnivorous, consisting of flesh, insects, and berries, where
the crown of the molars are tuberculate; while the canines are
adapted for holding the prey firmly as well as for tearing the
flesh, and the incisors, for both cutting and tearing the food.
The simplest form of a genuine digestive or enteric canal
is to be found in the Hydra, and in a more advanced stage
in the marine Hydroids. For the technical name of the
634 ZOOLOGT.
digestive tract we may adopt Haeckel's term enteron. In
the jelly-fishes the stomach opens into four or more water-
vascular canals or passages, by which the food, when par-
tially digested and mixed with sea-water, thus forming a
rude sort of blood, supplies the tissues with nourishment.
Jn the sea-anemones and coral polyps, the digestive cavity is
still more specialized, and its walls are partly separated from
the walls of the body, though at the posterior end the
stomach opens directly into the body-cavity. In the Echi-
noderms and worms do we find for the first time a genuine
digestive tube, lying in the perivisceral space (which, with
Haeckel, we may call the ccelom), and opening externally
for the rejection of waste matter.
In the worms the digestive canal now becomes separated
into a mouth, an oesophagus, with salivary glands opening
into the mouth, and there is a division of the digestive tract
into three regions — i.e., fore (oesophagus), middle (chyle-
stomach), and hind (intestine) enteron. In the mollusks
and higher worms there is a well-marked sac-like stomach
and an intestine, with a liver, present in certain worms (in
the ascidians and mollusks), opening into the beginning of
the intestine. All these divisions of the digestive tract ex-
ist still more clearly in the Crustacea and most insects. In
the latter, six or more excretory tubes (Malpighian vessels)
discharge their contents into the intestines, and in the " res-
piratory tree " of the Holothurian and the excretory vessels
of certain worms we have organs with probably similar uses.
In the vertebrates, from the lancelet to man, the alimen-
tary canal has, without exception, the three divisions of oes-
ophagus, stomach, and intestine, with a liver. In this branch
the lungs are either, as in the lancelet, modified parts of
the first division of the digestive tract or originally sac-like
dilatations of the digestive tract. The intestine is also
subdivided in the mammals into the small and large intestine
and rectum, a ccecum being situated at the limits between
the small and large intestine. We thus observe a gradual
advance in the degree of specialization of the digestive or-
gans corresponding to the degree of complication of the an-
imal.
COMPARATIVE ANATOMY OF ORGANS. 635
Organs of Circulation. — Intimately associated with the
digestive canal are the vessels in which the products of di-
gestion mix with the blood and supply nourishment for the
tissues, or. in other words, for the growth of the body. In
the Infusoria the evident use of the contractile vesicles is to
aid in the diffusion of the partly digested food of these mi-
croscopic forms. In the Hydra the food-stuff is directly
taken up by the cells lining the coelum, while the imper-
fectly formed blood also finds access to the hollows of the
tentacles. The mode in which the cells lining the canals
in the sponge take up, by means of the large cilia, micro-
scopic particles of food, directly absorbing them in their
substance, is an interesting example of the mode of nourish-
ment of cellular tissues of the lower animals.
The sea-anemone presents a step in advance in organs of
circulation ; here the partly digested food escapes through
the open end of the stomach into the perivisceral chambers,
the action of the cilia, with the contractions of the body,
churning the blood, consisting of sea- water and the particles
of digested food, and a few blood-corpuscles, hither and
thither, and forcing it into every interstice of the body,
even into the tentacles, so that the tissues are everywhere
supplied with food.
The water-vascular system of the Ccelenterates presents an
additional step in degree of complexity ; but it is not until
we reach the Echinoderms on the one hand, and such
worms as the Nemertes and allies on the other, where defi-
nite tubes or canals, the larger ones contractile, and in the
latter type at least formed from the mesoderm, serve to
convey a true blood to the various parts of the body, that
we have a definite blood system. In the Echinoderms a
true haemal or vascular system may co-exist with the water-
vascular system. In the annelids, such as the Nereis, one
of the blood-vessels may be modified to form ix pulsating
tube or " heart," by which the blood is directly forced out-
ward to the periphery of the body through vessels which may,
by courtesy, be called arteries, while the blood returns to
the " heart " by so-called veins.
The mollusks have a circulatory system which presents a
636 ZOOLOGY.
nearer approach to the vertebrate heart and its vessels than
even the crustaceans and insects, for the ventricle and one or
two auricles, with the complicated arterial and venous sys-
tem of vessels of the clam, snail, and cuttle-fish, truly fore-
shadow the genuine heart and systemic and pulmonary cir-
culation of the vertebrates. The mollusks, and king-crab,
and the lobster present some approach to the capillaries of
vertebrates. The circulation in certain worms, from Ne-
mertes upward, may be said to be closed, the vessels being-
continuous ; but they are not so in insects, where true veins-
are not to be found, the blood returning to the heart in
channels or lacunce in the spaces between the muscles and
viscera.
We have seen that in vertebrates the "aortic heart " of the
lancelet or Amphioxus is simply a pulsating lube, and there
are portions of other vessels wbich are pulsatile, so that
there is, as in some worms, a system of "hearts." A gen-
uine heart, consisting of an auricle and a ventricle only, first
appears in the lamprey. This condition of things survives
in fishes, with the exception of those forms, such as the lung-
fish (Dipnoans], whose heart anticipates in structure that of
the amphibians and reptiles, in which a second auricle ap-
pears. Again, certain reptiles, such as the crocodiles, antici-
pate the birds and mammals in having two ventricles — i.e.
a four-chambered heart. It should be borne in mind that
in early life the heart of all skulled vertebrates (Craniota)
is a simple tube, and as Gegenbaur states, " as it gradually
gets longer than the space set apart for it, it is arranged in
an S-shaped loop, and so takes on the form which the heart
has later on." Owing to this change of form, it is divided
into two parts, the auricle and ventricle.
A striking feature first encountered in the craniate ver-
tebrates is the presence of a set of vessels conveying the
nutrient fluid or chyle which filters through the walls of
the digestive canal to the blood-vessels ; these are the lym-
phatics. In the lancelet, as well as in the invertebrate ani-
mals, such vessels do not occur, but the chyle oozes through
the stomach-walls and directly mixes with the blood.
COMPARATIVE ANATOMY OF ORGANS. C37
Organs of Respiration.— Always in intimate relation with
the circulatory system are the means of respiration. The
process may be carried on all over the body in the simple
animals, such as Protozoa or sponges, or, as in Coelenterates,
it may be carried on in the water- vascular tubes of those
animals, while in the so-called "' respiratory tree" of Echin-
oderms it may go on in company with the performance of
other functions by the same vessels. Respiration, however,
is inclined to be more active in such finely subdivided parts
of the body as the tentacles of polyps, of worms, or any
filamentous subdivisions of any of the invertebrates ; these
parts, usually called gills, though only the gills of fishes are
truly such, present in the aggregate a broad respiratory sur-
face. Into the hollows of these filamentous processes,
which are usually extensions of the body- walls, 1)1 ood is
driven through vessels, and the oxygen in the water bathing
the gills filters through the integument, and immediately
gains access to and mixes with the blood.
The gills of the lower animals appear at first sight as if
distributed over the body in a wanton manner, appearing
in some species on the head, in others along the sides of the
body, or in others on the tail alone ; but in fact they always
arise in such situations as are best adapted to the mode of
life of the creature.
The gills of many of the lower animals afford an admira-
ble instance of the economy of nature. The tentacles of
polyps, polyzoans, brachiopods, and many true worms serve
also, as delicate tactile organs, for grasping and conveying
food to the mouth, and often for locomotion. The suckers
or " feet" of star-fish or sea-urchins also without doubt
perform the office of gills, for the luxuriously branched,
beautifully-colored tentacles of the sea-cucumber are simply
modifications of the ambulacral feet. One of the readiest
ways of judging of the mental condition, so to speak, of a
worm, such as Sabella or Terebrella or of a polyzoon or a
brachiopod, is to watch the movements of their beautiful
delicate gills, which are thrust in or out, waved back and
forth, slowly or suddenly, according to the degree of tran-
quillity or disquietude of their possessors.
638 ZOOLOGY.
Ill the mollusks, especially the snails and cuttle-fish, the
gills ure in close relations with the heart, so that in the cut-
tle-fish the auricles are called *' branchial hearts." The
gills of crustaceans (Fig. 259) are attached either to the
thoracic legs or are modified abdominal feet, being broad,
thin, leaf-like processes, into which the blood is forced by
the contractions of the tubular heart. Eespiration in the
insects goes on all over the interior of the body, the tracheal
tubes distributing the air so that the blood becomes oxyge-
nated in every part of the body, including the ends of all the
appendages. The gills of aquatic insects are in all cases fila-
mentous or leaf-like expansions of the skin permeated by
tracheae (Fig. 32G) ; they are, therefore, not strictly homolo-
gous with the gills of crustaceans or of worms.
The gills of fishes are so situated as to be constantly
bathed by fresh water ; in the amphibians and lung-fishes,
lungs, which are outgrowths of the enteric canal, replace the
air-sacs of the fishes, the air being now swallowed by the
mouth and gaining access by a special duct, the larynx, to
highly specialized organs of respiration, the lungs, which
are situated in the thoracic cavity near the heart.
The Nervous System.— We have seen that animals of com-
paratively complicated structure perform their work in the
animal economy without any nervous system whatever. It
has been only recently discovered that in a few jelly-fish is
there, for the first time in the animal series, a consecutive
nervous system, with definite nerve-centres or ganglia. In
most Acalephs none has been found, so that the majority
of Coelenterates perform their complicated movements,
swimming about for food, taking it in, digesting it, and re-
producing their kind, without the aid of what seems, when
we study vertebrates alone, as the most important and
fundamental system of organs in the body.
The Protozoa, sponges, and most Coelenterates depend, for
the power of motion, on the contractility of the protoplasm
of the body, whether or not separated into muscular tissue.
In the Hydra for the first time appear the traces of a ner-
vous tissue in the so-called nervo-muscular cells, one por-
COMPARATIVE ANATOMY OF ORGANS. 639
tion of a cell being muscular, the other nervous in its func-
tions.
A more definite nervous organization is the disconnected
bodies and rod-like nerve-cells, and other nervous bodies
found near the eye-spots, and the nerve-cells and fibres at
the base of the sea-anemone ; but, as has been stated, a gen-
uine nervous system for the first time appears in certain
naked-eyed jelly-fishes, in which it is circular, sharing the
radiated disposition of parts in these animals. The Echiii-
oderms have a well-developed nervous system, consisting of
a ring (without, however, definite ganglia, though masses of
ganglionic cells are situated in the larger nerves), surround-
ing the oesophagus, and sending a nerve into each arm ; or in
the Holothurians situated under the longitudinal muscles
radiating from that muscle closing the mouth.
In all other invertebrate animals, from the worms and
mollusca to the crustaceans and insects, the nervous system
is fundamentally built upon the same plan. There is a pair
of ganglia above the oesophagus called the " brain ;" on the
under side is usually a second pair ; the four, with the nerves
or commissures connecting them, forming a ring. This ar-
rangement of ganglia, often called the " oesophageal ring,"
constitutes, with the slender nerve-threads leading away from
them, the nervous system of the lower worms, in many of
which, however, as also in the Polyzoa and Bracliiopoda,
the subcesophageal ganglia are wanting. Now to the
oesophageal ring with its two pairs of ganglia add a third
pair of visceral ganglia, and we have the nervous system
of the clam and many mollusks. In the higher ringed
worms, the Annnlata, and in the Crustacea and Insects, a
chain of ganglia, or brains, which is ventral, lying on the
floor of the coslum or body-cavity, completes the highest
form of nerve-centre found in the invertebrate animals,
unless we except the mass of ganglia, partly enclosed in an
impei'fect cartilaginous capsule of the Cephalopods, which
hints at the brain and skull of Vertebrates. The nervous
cord of the Appendicularia, an Ascidian, is constructed on
the same plan as in the Annulata, but the mode of origin and
apparently dorsal position of the nervous system of the
ZOOLOGY.
tailed larval Ascidian presents features which apparently
anticipate the state of things existing among the lower ver-
tebrates, such as the lancelet.
In the last-named animal the nervous cord has a dorsal
position — i.e., rests above the alimentary canal ; but as yet
no brain appears, only a very slight enlargement of the an-
terior end of the nervous cord from which a few nervous
threads are distributed to minute sense-organs in the head.
In all the craniate Vertebrates, from the lamprey upward,
the brain is a series of close-set ganglia, having a definite
site, enclosed by a skull or brain-box, and with definite re-
lations to the sense-organs. Attention has already been
given in a general way, in the foregoing pages, to the increas-
ing complexity of the brain, especially to the relative size
and markings of the cerebral hemispheres and cerebellum,
as we rise from the fish to man.
Organs of Sense. — While all animals, perhaps without
exception, unless it be the root-barnacles, and a few other
parasitic forms, have the sense of touch, which, in the lower
Protozoa is so slight as to be compared with the contractility
common to all living protoplasmic matter, whether existing
in cellular tissue or one-celled, independent animals ; not all
of the lower animals have, however, definite sense-organs.
The Eye.— The most important of these are undoubtedly
eyes, as they are the most commonly met with. The sim-
plest form of eyes are perhaps those of the sea-anemone, in
which there are, besides pigment cells forming a colored
mass, refractive bodies which may break up the rays of light
impinging on the pigment spot, so that these creatures may
be able to distinguish light from darkness. The next step
in advance is where a pigment mass covers a series of refract-
ive cells called " crystalline rods " or " crystalline cones,"
which are situated at the end of a nerve proceeding from
the " brain." Such simple eyes as these, often called " eye-
spots," may be observed in the flat worms, and they form
the temporary eyes of many larval worms, Echinoderms
and mollusks. In some nemertean worms, such as certain
species of Polia and Nemertes, true eyes appear, but in the
ringed worm, NeopTianta celox, Greef describes a remarka-
COMPARATIVE ANATOMY OF ORGANS. 641
bly perfect eye, consisting of a projecting spherical lens
covered by the skin, behind which is a vitreous body, a
layer of pigment separating a layer of rods from the exter-
nal part of the retina, outside of which is the expansion of
the optic nerve. Eyes are also situated on the end of the
body in some worms, and in a worm called Polyophthalmus
each segment of the body bears a pair of eyes.
The eyes of mollusks are, as a rule, highly organized, un-
til in the cuttle-fish the eye becomes nearly as highly de-
veloped as in fishes, but still the eye of the cuttle-fish is not
homologous with that of Vertebrates, since in the former
the crystalline rods are turned toward the opening of the
eye, while in Vertebrates they are turned away from the
opening of the eye, so that, as Huxley as well as Gegen-
baur show, the resemblance between the eye of the Ce-
phalopods and of the Vertebrates is a superficial one.
While, as we have seen, the eyes of the worms and the
mollusks are situated arbitrarily, by no means invariably
placed in the head, in the Crustaceans the eyes assume in
general a definite position in the head, except in a schizo-
pod crustacean (Eupliausid), where there are eye-like organs
on the thorax and abdomen. In insects there are both sim-
ple and compound eyes occupying definitely the upper and
front part of the head.
The eyes of the lancelet are not homologous with tho.se
of the higher Vertebrates, being only minute pigment spots
comparable with those of the worms. In the skulled Ver-
tebrates the eyes are of a definite number, and in all the
types occupy a definite position in the head.
The Ear.— The simplest kind of auditory organ is to be
found in jelly-fishes, where an organ of hearing first occurs.
In these animals, situated on the edge of the disk, are minute
vesicles containing one or more concretionary bodies or
crystals. Reasoning by exclusion, these are supposed to rep-
resent the ear- vesicles or otocysts of worms and mollusks ;
and the concretions or crystals, the otolitlis of the same kind
of animals.
The otocysts or simple ears of worms and mollusks are
minute and usually difficult to find, especially the auditory
ZOOLOGY.
nerve leading from them to the nerve-centres. In the
clam it is to be looked for in the so-called foot. In the
snails the auditory vesicles are placed in the head close to
the brain, as also in cuttle-fish. The ears of Crustacea are
sacs formed by inpushings of the integument filled with fluid,
into which hairs project, and which contain grains of sand
which have worked in from the outside, or concretions of
lime. These are situated in the shrimps and crabs at the
base of the inner antennae, but in certain other lower Crusta-
cea, as in Mysis, they are placed at the base of the lobes
of the tail. In the insects the ear is a sac covered by a
tympanum, with a ganglionic cell within, leading by a
slender nerve-fibre to a nerve-centre, and in these animals
the distribution of ears is very arbitrary. In the locust they
are situated at the base of the abdomen (Fig. 279) ; in the
green grasshoppers or katydids and the crickets in the fore
tibire ; and it is probable that in the butterflies the antennae
are organs both of hearing and of smell.
The vertebrate ears are two in number and occupy a dis-
tinct, permanent position in the skull, however much modi-
fied the middle and outer ear become.
Organs of Smell.— The sense of smell is obscurely indi-
cated by special organs in the invertebrate animals, nasal
organs as such being characteristic of the skulled Vertebrates.
Whether organs of smell exist in any worms or not is un-
known ; there are certain pits in some worms which may
possibly be adapted for detecting odors. In most insect^ at
least the organs of smell are without doubt well developed ;
the antennas of the burying beetles are large and knob-like,
and evidently adapted for the detection of carrion. It is
possible that certain organs situated at the base of the wings
of the flies and on the caudal appendages of the cockroach
and certain flies (Fig. 290) are of use in detecting odors.
CHAPTER X.
DEVELOPMENT AND METAMORPHOSES OP AM.
MALS.
Embryology.— The development of the individual is often
an epitome of the classification of the order or class to which
it belongs, as well as of the development or appearance in
geological history of the different members of the order or
class to which the individual belongs. The changes under-
gone by the animal within the egg are often so sudden and
marked that the separate chapters of its history as an em-
bryo can be read side by side with the history of the succes-
sion of the different genera and families of its type in past
ages. Moreover, it is now generally supposed by naturalists
that these critical periods in the development of the individ-
ual have a constant relation to external causes which have
acted on the ancestors of the animal, and hence that these
changes are the result of influences and changes in the sur-
roundings of the forms which have preceded. So much in-
terest, therefore, attaches to the subject of the early develop-
ment of animals, that much prominence has in the foregoing
pages been given to the matter.
"We may now briefly review the more striking phenomena
of development in the invertebrate animals, and close with a.
summary of the mode of development of Vertebrates.
The eggs of all animals consist of three portions, the egg
proper, consisting of a mass of protoplasm enveloped by
the yolk or food-stuff, the nucleus or germinative vesicle,.
and the nncleolus or germinative spot.
Before the egg is ready for fertilization it undergoes a
special process of maturation, involving the following series-
044
ZOOLOGY.
of events : 1. Transportation of the germinal vesicle to the
surface of the egg ; 2. An absorption of the membrane of
the nucleus or germinative vesicle and a change in the ger-
minative spot ; 3. The portion of the nucleus surviving as-
sumes a spindle-shape, this portion being largely formed
from the nucleolus ; 4. One end of the spindle enters into a
protoplasmic prominence at the surface of the egg ; 5. The
spindle divides into two halves, one remaining in the egg,
the other in the prominence, the latter separating from the
egg and forming the polar cell ; 6. A second polar cell forms
in the same manner as the first, part of the spindle still re-
maining in the egg ; 7. The part of the spindle remaining
in the egg, after the formation of the second polar cell, is
converted into a nucleus, the female pronudeus, and finally,
just before fertilization, the female pronucleus takes its po-
sition at the centre of the egg.
Fig. B39. — Development of the sperm-cells of a blind worm (Epicrium glutinotuni).
a, testis-cell; b, the same, more numerous; c, d. e, becoming more numerous and
finally forming spermatozoa (/). Highly magnified.— After Miuot.
After this, the first step in the development of many-celled
animals is the fusion of the protoplasm of the female pronu-
cleus with that of the sperm-cell ; for this end the latter is
•exceedingly minute and provided with a vibratile cilium or
•" tail," so that it may force its way in toward the centre
of the egg. These sperm-cells are developed in the testis
•of the male. On close examination with very high powers of
the microscope, certain cells, called " mother cells," maybe
found developed in fine tubules forming the gland ; these are
known to possess several nuclei, which are destined to be-
come spermatozoa (Fig. 539, a and 5) ; these multiply until
they become very numerous, elongated, and packed side by
DEVELOPMENT OF ANIMALS. 645
side in bundles (e) ; from each one acilium or " tail " grows
out, when they are set free from the mother-cell. In this
tailed form they are very active, and effect the fertilization
of the egg of an animal of the same species. This is due to
contact of one spermatozoon with the female pronucleus situ-
;ited in the egg. Immediately after the spermatozoon has
penetrated into the egg, its ''head' is converted into a
nucleus, called the male pronucleus ; after this, radiating
strias make their appearance around its surface ; then the
male pronucleus travels toward the female pronucleus, and
finally the male and female pronuclei fuse together and form
the first " segmentation nucleus."
This nucleus subdivides, and the result is a mass of cells
resembling a mulberry, and hence called the morula. The
outer circle of the cells of the morula may hereafter form
what is called th e blastoderm ; after a while it pushes in at
one point, and the portion thus forced is called the inner
germ-layer (endoderm} and the outer is called the ectoderm
or outer germ-layer, and in this condition the germ is called
a gastrula. Subsequently, a third layer develops from the
endoderm, which is called the mesoderm, and after this the
different tissues become developed.
All animals, from sponges to man, become first two- and
afterward three-layered sacs ; so that all animals above the
Protozoa not only, as a rule, originate from eggs, but may be
said to travel, up to a certain point, the same developmental
path. From this point the members of different types of
life diverge. How different are the modes of development
of animals has been set forth in the different life-histories
related in the foregoing pages of this book.* But the laws
of growth are as stable and uniform — certain causes pro-
ducing certain results — as the laws of the motions of the
heavenly bodies.
When the workings of these laws of development are in-
terfered with by sudden accidents, by too scanty nourish-
ment, and by the transmission of the effects of such acci-
* For a fuller, more consecutive, though still fragmentary account,
the reader is referred to the author's " Outlines of Comparative Em-
bryology, or Life Histories of Animals, including Man."
646
ZOOLOGY.
dents or abnormal products from parents who have been
affected by them, the results are usually abnormal, more or
less distorted forms, with greater or less defects ; and here
again have been observed laws governing the production of
abnormalities, the study of these being called teratology.
We may study the mode of development of the domestic
fowl or hen as the best known example to illustrate the
changes undergone by an embryo vertebrate, for this pur-
pose condensing the statements of Foster and Balfour in
their " Elements of Embryology."
Fig. 540.— Blastodermic disk and germ of a rabbit about one day old. seen from the
back, a, edge of the head-end of the amnion; b, fore-brain; c, lateral expansion of
the same, or primitive eye-vesicle; d, middle, e, hind brain. There are eight protover-
tebne, between which is situated the spinal cord. Enlarged ten times.— After Bischoff.
First Day. — After fertilization of the egg, segmentation of
the egg occurs, but instead of being total, forming a morula
or mulberry mass, it is, as in all birds and in the majority of
fishes and reptiles (except the lanceletand lamprey eel), par-
tial, or confined to the periphery of the yolk, resulting in
the formation of a blastoderm, the oval more apparent por-
tion being called the " blastodermic disk," which is the be-
ginning of the embryo. In six or eight hours after fertili-
zation the three germ-layers appear. From the outer germ-
DEVELOPMENT OF ANIMALS. 647
layer are destined to arise the skin and wall of the body
with the nervous system ; from the second (mesoderm, in
the embryo called the meso blast) are formed the heart and
the vascular system, as well as the stomach and intestines.
The middle layer now thickens, causing the mark known
as the " primitive streak," along the middle of which runs
the " primitive groove." The notochord now appears and
the muscle-plates (called profoverfebrcc, Fig. 540). The am-
nion arises as a membrane, splitting off from the outer germ-
layer of the embryo, and finally forms a cavity which is
filled with a fluid. About this time the allantois arises as
an offshoot of the alimentary canal, budding out at the
hinder end of the embryo, and finally curving over the em-
bryo, serving as a foetal respiratory membrane.
Second Day. — The three portions or vesicles of the brain
now appear (Fig. 540), as well as the alimentary tract and
heart, both arising in the head-fold or enlargement (Fig. 540,
a to c), and soon the blood-vessels arise as channels in which
blood-corpuscles appear, originating as amceba-like cells
separating from the cellular mass of the mesoderm. Dur-
ing the second day also the eyes and ears begin their devel-
opment, being at first simply folds or inpushings of the
outer germ-layer.
Tli ird Day. — This is one of the most eventful days, as im-
portant steps in the elaboration of the different organs are
taken ; the different parts of the brain, of the alimentary
tract and its appendages being sketched out, and the rudi-
ments of the lungs, the liver, pancreas, nose, and different
parts of the eye and ear appearing. On the fourth day the
wings and legs grow out, appearing first as flattened buds.
The notochord, which is indicated by the second day, by the
sixth begins to diminish in size, disappearing by the time
the chick is hatched, while by the twelfth day the deposition
of bcne in the bodies of the vertebras commences. Between
the eightieth and one hundredth hour the internal differences
in the sexes appear, the testes beginning to arise on the
sixth day.
Fifth Day. — The limbs have by this time developed so as
to show the knee- and elbow-joints, as well as the cartilages
648
ZOOLOGY.
ch
Fig. 541 .—Five schematic figures showing the development of the foetal egg-mem-
branes, where in all except the last the embryo is represented as if seen in longitudinal
Bection. 1. Diagram of egg with zoiia pellucida, blastoderm (a, i). germinal disk, anch
embryo. 2. Egg with the first traces of the yolk-sac (dl and ninnion (to, .«.«. and am.
3. Egg with the amnion uniting and forming a sac ; the allantois (ah budding out.
4. Egg with the villi of the serous membrane (sz); the allantois larger ; embryo with
mouth and anal opening. 5. Egg in which the vascular layer of the allantois lies close
to the serous layer and has grown into the villi of the same, constituting the true
chorion (ch). Yolk-sac much smaller, about to be drawn into the cavity of the amniou,
DEVELOPMENT OF ANIMALS, 649
which precede the formation of the bones of the digits and
limbs. The primitive skull also arises from the mesoderm.
Until the sixth day it would be impossible to say whether
the embryo was that of a bird, reptile, or mammal, but now
the characters peculiar to birds appear. The wings and legs
manifest their bird -like characters, the crop and intestinal
coeca are indicated, " the stomach takes the form of a giz-
zard, and the nose begins to develop into a beak, while the
incipient bones of the skull arrange themselves after the
avian type. . . . From the eleventh day onward, the embryo
successively puts on characters which are not only avian,
but even distinctive of the genus, species, and variety J>
(Balfour). By the ninth or tenth day the feathers originate
in sacs in the skin, while the nails and scales begin to ap-
pear on the thirteenth day, and at this time the various
muscles of the body can be distinguished. Development is
thus seen to be from the general to the special, from the
simple to the complex ; the trunk is first indicated ; while
the peripheral parts — i.e., the extremities, the digits, the
skin, feathers or scales, or hair, whatever be the type of
Vertebrate — are the last to be elaborated ; in other words,,
the characters of the branch, class, and order are the first.
to be evolved, those of the family, genus, and species the
last.
The development of the rabbit, guinea-pig, or any mam-
mal, including even man, follows much the same order as
in the chick, there being, however, a well-marked morula ;
the differences are due to the fact that the embryo mammal
d, yolk-skin ; d', villi of the yolk-skin ; sh, serous membrane ; sz. villi of the serous
membrane ; ch, chorion (vascular layer of the allantois); chz, true villi of the chorion
(arising from the projections of the chorion and the sac of the serous membrane);
am, aninion ; ks, head-fold of the amnion ; us, tail-fold of the amnion ; ah, cavity of
the aninion : as, sheath of the amnion for the navel-string : a, the first beginning of
the embryo arising from a thickening of the outer layer of the blastoderm a' ; »«v
thickening forming the germ in the middle layer of the blastoderm (mr), which at first
only reached as far as me germinal disk, and afterward forms the vascular layer of
the yolk-sac (df) which connects with the intestino-musciilar layer (darmfaserblatt);
st, sinus terminalis ; dd, intestine-glandular layer (darmdrusenblatt) arising out of a
part of i, the inner layer of the blastoderm (afterward the epithelium of the yolk-
sac) ; kh, cavity of the blastoderm, which afterward becomes (ds) the cavity of the
yolk-sac ; dg, passage way of the yolk ; al. allantois ; e, embryo ; r, original space
between the amniou and chorion. filled with albuminous fluid ; vl, anterior body-wall
in the region of the heart ; hh, cavity of the heart without the heart itself. In Fins.
i and 3, the amnion is, for the sake of clearness, represented as situated too far away
from the embryo ; so also the cavity of the heart is drawn too small and the embryo
too large, since, except in Fig. 5, they are only drawn diagrammatically. — From Kol«
liker's " Entwickelungsgeschichte des Menschen und der hoheren Thiert."
650 ZOOLOGY.
develops in a specialized portion of the oviducts, the uterus
or womb, and that the growing germ until birth is supplied
not with yolk as food, but by the nourishment in the ma-
ternal blood. In fact, while the eggs of reptiles and birds
are enormous, it was not known with certainty until 1827
that mammals developed from eggs. The eggs of these an-
imals are very minute, owing in part to the minute amount
of yolk they contain ; that of man being less than a quarter
of a millimetre (Tfg- inch) in diameter.
The mammalian embryo, nourished as it is through the
maternal circulation, needs additional temporary organs ;
these are the chorton (Fig. 541, cJi), formed from the vitelline
membrane (present in birds as well as mammals), which sends
off villi or processes extending into the walls of the womb.
Besides this, in the higher or placental mammals, the pla-
centa or after-birth is formed, which serves as an organ of
respiration as well as to supply the embryo or foetus with
nourishment, and to carry off its effete products by means
of the maternal circulation.
It is comparatively late in embryonic life that the mam-
malian features appear ; in the dog it is twenty-five days
before it can be told whether the embryo is a mammal or
not.
All mammals may be said to pass through a morula and
gastrula stage. In the next stage when the nervous chord
and notochord arise, the mammalian germ is on the same
footing with an Ascidian larva. In a succeeding stage,
when the proto vertebrae appear, an Amphioxus stage is
reached ; when a brain is formed, the level of the fishes is
reached ; after the limbs bud out the young mammals may
be said to assume the condition common to the embryos of
all Amphibian and higher Vertebrates. When the allantois
begins to appear the amphibian feature (the want of an
allantois) is dropped. When the placenta has developed
the avian characters are surpassed and the mammalian feat-
ures assumed. Thus the development of the individual
mammal is an epitome of that of the branch or type to
which it belongs, and the successive steps in the degree of
specialization of the individual mammal are also paralleled
METAMORPHOSES OF ANIMALS. C51
by the geological succession of the representatives of the
different classes, as without much doubt lancelets (or at least
acraniate, boneless forms) were the first Vertebrates to ap-
pear, and we know that fishes appeared before Amphibians,
that their type culminated before the reptiles held full
sway in Mesozoic times, and that birds, after them mam-
mals, and, last of all, man appeared, who crowns the series
of vertebrate forms.
Metamorphosis.— While many animals are hatched like
the chick with the form of the parent, others pass through
a series of changes of form called metamorphoses ; these
changes of form adapt the animal to changes in its sur-
roundings, involving alterations in its mode of life — slight if
the change of body-form is slight, thorough-going and radi-
cal if its body becomes profoundly modified. As an exam-
ple of a complete metamorphosis may be cited the life-his-
tories of the jelly-fishes, the star-fish, sea-urchins, sea-cu-
cumbers, the marine-worms, the mollusks, the crustaceans,
insects, and the salamanders and toads and frogs, already de-
scribed in the foregoing pages. If the student will read and
compare these different accounts, and then consider the
striking differences between the complicated histories of cer-
tain species, compared with the direct mode of growth of
other species of the same order or family, or even of the
same genus, the inquiry will arise, What is the purpose or
use of such a series of changes ? If he look carefully into
the embryological changes of those species which are born
or hatched with the form of the adult, he will see that their
embryological history is, in point of fact, a condensed sum-
mary of the changes undergone after hatching by their co-
species, which, to gain the same adult form, have been sub-
jected by nature to a series of complicated, and, at first
sight, superfluous changes of form and environment.
Most shrimps and crabs undergo a complicated metamor-
phosis ; in the different changes of forms they lead different
lives, and are subjected to different surroundings, the larvae,
for the most part, being free-swimming and living near the
surface of the water, while the parents are stationary. The
barnacle, when very young, swims near the surface of the
652 ZOOLOG T.
sea, afterward, as a pupa, becoming fixed to a rock ; the
young oyster-spat swims freely about, finally becoming fixed
to the bottom. This change of life and of form undoubted-
ly tends to prevent the extinction of the species, since, if at
a given moment the parents were swept out of existence,
the young living in a different station would continue to
represent the species. This law is seen to hold good among
insects, where many species are represented in the winter-
time by the egg alone, others by the caterpillars, others by the
chrysalis, while still others hybernate as imagines. Again,
in the marine species, the free-swimming young are borne
about by ocean and tidal currents, and in this way what in
adult life are the most sedentary forms become widely dis-
tributed from coast to coast and sea to sea. On the other
hand, the larval forms of fixed marine animals serve as food
for fishes, especially young fishes and numerous inverte-
brates, while their stationary parents afford subsistence for
still other forms of life ; thus were it not for the metamor-
phoses of animals, many species would become extinct
sooner than they do, while the great overplus of larval
forms gives to many other species of animals a hold on ex-
istence.
Metamorphosis among the invertebrate animals, espe-
cially, is perhaps the rule and not the exception. "Where ani-
mals develop directly, as in certain insects, crustaceans, cer-
tain salamanders, toads and frogs, this is due to some
change in the environment ; in the case of Amphibians,
perhaps the want of water, or some other cause, there always
being an adaptation in the case of the direct mode of de-
velopment to the surroundings of the animal and the require-
ments of its existence.
Parthenogenesis, and Alternation of Generations.—
Having traced the normal process of development of ani-
mals, we may turn to certain unusual or abnormal modes of
production. As an example of what is known as " alternation
of generations," may be cited the mode of development of the
jelly-fish, such as the naked-eyed medusa? (Meliccrtum and
Campanularia], which at one time of life develop by budding,
at another by eggs ; of thetrematode worms, the adult forms
ALTERNATION OF GENERATIONS. 653
of which lay eggs, while the reclia or proscolex of the same
worm produces cercarice by internal budding. Here also
may be cited the cases of strobilation of the Aurelia, the
tape-worm, the Nais, Syllis, and Autolycus, among Anne-
lids. Tims among Coelenterates and worms, as well as some
Crustacea, a large number of individuals are produced,
not from eggs, but by budding.
Similar occurrences take place among insects, as the
Aphis or plant-louse, in which a virgin Aphis may bring
forth in one season nine or ten generations of Aphides, so
that one Aphis may become the parent of millions of
young. These young directly develop from eggs or buds
which are never fertilized, hence the term parthenogenesis,
or virgin-reproduction, sometimes called ayarnoyenesis (or
birth without marriage). The bark-lice as well as the
Aphides develop in this manner during the warm Avea-
ther ; but at the approach of cold both male and female
Aphides and Coccidae appear, the females laying fertilized
eggs, the first spring brood thus being produced in the
normal, usual manner.
Still more like the production of young in the redia of
the Trematode worms is the case of the larva of a small gall-
gnat (Miastor), which during the colder part of the year from
autumn to spring produces a series of successive generations
of larvse like itself, until in June the last brood develops
into sexually mature flies, which lay fertilized eggs.
While the larval Miaster produces young like itself, the
pupa of another fly, Chironomus, also lays unfertilized eggs.
A number of moths, including the silk-worm moth, are
known to lay unfertilized eggs which produce caterpillars.
Among the ffymenoptera, the currant saw-fly, certain gall-
flies, several species of ants, wasps (Polistes), and the honey-
bee, are known to produce fertile young from unfertilized
eggs ; in the case of the ants and bees, the workers lay eggs
which result in the production of males, while the fertilized
eggs laid by the female ant or queen bee produce females
or workers.
Taking all these cases together, parthenogenesis is seen to
be due to budding, or cell-division, or multiplication. Now,
C54: ZOOLOGY.
it will be remembered that the egg develops into an animal
by cell-division, so that fundamentally parthenogenesis is
due to cell-division, the fundamental mode of growth ;
hence, normal growth and parthenogenesis are but extremes
of a single series. In this connection, it will be remembered
that all the Protozoa reproduce by simple cell-division,
that among them the sexes are not differentiated, that they
do not reproduce by fertilized eggs ; hence, so to speak,
among Protozoa parthenogenesis is the normal mode of re-
production ; and when it exists in higher animals it may
possibly be a survival of the usual protozoan means of
stocking the world with unicellular organisms, with which
we know the waters teem. And this leads us to the teleol-
ogy or explanation of the cause why parthenogenesis has sur-
vived here and there in the world of lower organizations ;
it is plainly, when we look at the millions of Aphides, of
bark-lice, the hundreds of thousands inmates of ant-hills
and bee-hives, for the purpose of bringing immediately
into existence great numbers of individuals, thus ensuring
the success in life of certain species exposed to great vicis-
situdes in the struggle for existence. That this unusual
mode of reproduction is all-important for the maintenance
of the existence of most of the parasitic worms, is abundantly
proved when we consider the strange events which make up
the sum total of a fluke or tape-Avorm's biography. With-
out this faculty of the comparatively sudden production of
large numbers of young by other than the slow, limited
process of ovulation, the species would be stricken off the
roll of animal life.
Dimorphism and Polymorphism. — Involving the produc-
tion of young among many-celled animals (Metazoa} by what
is fundamentally a budding process, we have two sorts of
individuals. When the organism is high or specialized
enough to lay eggs which must be fertilized, we have a
differentiation of the animal into two sexes, male and fe-
male. Reproduction by budding involves the differentia-
tion of the animal form into three kinds of individuals —
i.e., males, females, and asexual individuals, among insects
often called workers or neuters. These have usually, as in
DIMORPHISM. 655
ants and bees, a distinct form so as to be readily recog-
nized at first sight. Among the Coelenterates and worms
the forms reproducing by parthenogenesis are usually larval
or immature, as if they were prematurely hurried into ex-
istence, and their reproductive organs had been elaborated
in advance of other systems of organs, for the hasty, sud-
den production, so to speak, of large numbers of individu-
als like themselves.
In insects, as we have stated elsewhere,* dimorphism is
intimately connected with agamic reproduction. Thus the
summer wingless, asexual Aphis and the perfect winged
autumnal Aphis may be called dimorphic forms. The per-
fect female may assume two forms, so much so as to be mis-
taken for two distinct species. Thus, an oak gall-fly (Cy-
nips quercus-spongifica) occurs in male and female broods in
the spring, while the autumnal brood of females were de-
scribed originally as a separate species under the name O.
aciculata. Walsh considered the two sets of females as di-
morphic forms, and that Cynips aciculata lays eggs which
produce C. quercus spongifica. Among butterflies, dimor-
phism occurs. Papilio memnon has two kinds of females,
one being tailless, like the tailless male, while Papilio Pani-
mon is polymorphic, there being three kinds of females be-
sides the male.
There are also four forms of Papilio Ajax, the three
others being originally described as distinct species under
the name of P. Marcellus, P. Telamonides, and P. Walsh ii.
Our Papilio glaucus is now known to be a dark, dimorphic,
climatic form of the common Papilio Turnus. There are
dimorphic males among certain beetles, as in the Golofa
liastata Dejean, of Mexico, in which one set of males are
large and have a very large erect horn on the prothorax,
and in the other the body is much smaller, with a very
short conical horn.
Temperature is also associated with the production of
polymorphic forms in the temperate regions of the earth,
as seen in certain butterflies, southern forms being varieties
* Guide to the Study of Insects, sixth edition, p. 52.
€56 ZOOLOGY.
of northern forms, and alpine " species " proving to be va-
rieties or seasonal forms of lowland species. For example,
Weismann states that the European butterflies, Lycaon amyn-
tas and potysperchon, are respectively summer and spring
broods. Antliocharis Simplonica is an alpine winter form of
Anthocharis Bella, as is Pier is bryonice of Pieris napi. In
this country, as Edwards has shown, two of the polymorphic
forms oiPapilio Ajax — i.e., Walshii and Telamonides — come
from winter chrysalids, and P. marcellus from a second
brood of summer chrysalids. It thus appears that poly-
morphism is intimately connected with the origin of species.
Perhaps the most remarkable case of polymorphism is to be
seen in the white ants (Termites), where in one genus there
are two sorts of workers, two sorts of soldiers, and two kinds
of males and females, making eight sorts of individuals ; in
the other genera there are six. Among true ants there are,
besides the ordinary males, females, and workers, large-
headed workers. In the honey-ant (Myrmecocystus Mexi-
canus], besides the usual workers, there are those with
enormous abdomens filled with honey. Other insects, es-
pecially certain grasshoppers, are dimorphic. Certain par-
asitic Nematode worms are dimorphic ; and among the
Ccelenterates, especially the Hydroids, there is a strong ten-
dency to polymorphism.
Individuality. — Perfect individuality among animals is
the rule, each individual being capable of maintaining an
independent existence ; but we have seen that there are many
of the lower animals in which it is difficult to determine
whether the different members of a colony are really in-
dividuals or simply individualized organs.
The student, in referring back to the account of the Por-
tuguese man-of-war, will find it difficult to say whether the
four kinds of members of the floating colony are organs or
individuals, and he will probably agree with the view that
it is best to provisionally call them zooids or individualized
organs ; for the feeders, the reproductive zooids, the digest-
ive zooids, and the swimming float, or the swimming bells
of the other Siphonophores, are highly specialized organs,
and only differ from true individuals in lacking the power
INDIVIDUALITY AND HTBRIDITT. 657
of free motion and of maintaining an independent existence.
So with many other Coalenterates and with the tapeworm,
whose proglottides or segments are finally capable of sepa-
rate existence. Among the higher invertebrates, even the
different members of a colony of white or true ants lack a
certain amount of individuality, the workers performing
labors upon which the maintenance of the very existence of
the colony depends, so that there are different grades of in-
dividuality, from examples like the Hydractinia and the
Siphonopnores up to those insects which live socially ; and
we see that the most perfect individuality exists in those
animals which can most efficiently provide for their own
sustenance and for the continuance of their species.
Hybrid! ty.— It is rare that two species, even of the same
genus, can produce offspring ; when such cases occur, the
result is called a hybrid. For example, the mule is a hybrid,
being bred from a female horse and an ass ; but the mule
is not fertile, and hybrids are very rarely fertile. The In-
dian dog and coyote are said by Cones to interbreed, and
on the Upper Missouri we have seen dogs which had every
appearance of being such hybrids. Dogs also cross with the
fox (Darwin). The American bison is known to breed with
the domestic cattle, and it seems to be a well-established
fact that the hybrids are fertile. Fish readily hybridize.
Darwin states that he knows of no thoroughly well-au-
thenticated cases of perfectly fertile hybrid animals, though
he adds, " I have reason to believe that the hybrids from
Cervulus vaginalis and Reevesii and from PJiasianus col-
chicus with P. torquatus are perfectly fertile." The hare
and rabbit are supposed to have fertile offspring ; the hy-
brids of the common and Chinese geese (Anser cygnoides)
are fertile. The crossed offspring from the Indian humped
and common cattle interbreed. Caton has hybridized the
Virginia deer with the Ceylon deer and the Acapulco deer ;
" the hybrids seem perfectly healthy and prolific." Among
insects over 100 cases of hybridity have occurred. Hybrids
between the brown and polar bear, the leopard and jaguar,
Equus onager and E. hemippus, E. burchelli with the com-
mon horse, and with the common ass and E. hemionus ;
have been raised.
CHAPTER XI.
THE GEOGRAPHICAL DISTRIBUTION OF ANI-
MALS.
THE assemblage of animal life peopling any one locality
or area is called its fauna, as the plants of a place consti-
tute its flora. Where the physical geography— i.e., the con-
tour of the surface, the plains, valleys, and hills— is of iden-
tical character and the climate the same, the fauna is much
the same, but when these characteristics of soil and climate
change, as in passing from lowlands to highlands, or from
south to north, the assemblage of animals will be found
to change in a corresponding ratio. And as there are no
definite limits to any large area of the earth's surface, the
physical features of one area merging insensibly, as a rule,
into adjoining districts, so adjoining fauna? merge into one
another, and a certain proportion of the species may range
through two or more faunal areas.
There are in nature causes tending to restrain animals
within their faunal limits, and others tending to diffuse
them, or to cause them to migrate from their specific cen-
tres or centres of creation— namely, the point where the in-
dividuals of a species are most abundant, and where, ac-
cordingly, they are supposed to have originated.
Barriers to the Spread of Animals from their Specific
Centres.— Among the most important are the oceans and
their basins. The animals of the opposite sides of the Pa-
cific Ocean are entirely nnlike, no species being common to
the two sides ; while, of the immense numbers of animals
peopling the coast of Brazil and the opposite coast of Af-
rica, only two or three are known to be identical. Differ-
ence in climate is also a great barrier, the animals of the
GEOGRAPHICAL DISTRIBUTION. 659
tropics, as a whole, being unlike those of the temperate
zones ; while arctic and antarctic animals have features in
common. Mountains serve as most important barriers, re-
straining animals within their limits ; thus the basins be-
tween or surrounded by continuous ranges of mountains
harbor fauna1 differing from those on the opposite sides of
the mountains. For example, the majority of the animals
of the Great Basin between the Rocky Mountains and the
Sierra Nevada differ from those of the Pacific slope or the
prairie lands lying east of the Rocky Mountains, as the
meteorological and geological features are different. The
Cordilleras of South America form a barrier to the diffusion
westward of Brazilian animals. Still this fact is not to be
taken too literally, as the mountains are divided by valleys
and rivers, which afford means of communication and an
interchange of specific forms ; thus certain species of ani-
mals of the Rocky Mountain plateau occur on each side of
the range, as do those in the Alleghany district of the At-
lantic coast. In the West Indian and especially the Hawa-
iian Islands, where the species of land snails are very numer-
ous, certain forms are restricted to the deep narrow valleys,
being confined to very restricted areas. So also the cold
Alpine summits of the White Mountains of New Hamp-
shire, of the Rocky Mountains, of the Alps and Scandina-
vian mountains harbor a few species either peculiar to those
extremely limited tracts or found northward in the Arctic
regions.
Deserts may act much as inland seas to separate the ani-
mals of the adjoining more fertile tracts, and they afford
dwelling-places for animals which are incapable of living
elsewhere. Desert faunae have a general fades the world
over, though the original elements out of which the faunae
have been made up may radically differ.
The distribution of plants also has much to do with that
of those animals which are dependent on them for food ;
as a rule, the distribution of both plants and animals de-
pends on the same physical causes.
Large rivers sometimes act as barriers, but more often,
perhaps, aid in the diffusion of the smaller forms, such as
£60 ZOOLOGY.
insects, mollusks, and crustaceans. Different systems of riv-
ers have distinct sets of fluviatile animals ; for example, the
fishes of the Ohio and Upper Mississippi and its tributaries
differ from those of the Hudson River and the New England
rivers, and the latter from those draining the Southern At-
lantic States. The fresh-water mussels, so abundant and
•characteristic of the waters of the Mississippi and its tribu-
taries are confined to the region lying west of the Allegha-
aiies and east of the Great Plains. The fishes and mollusks
of the rivers of the Pacific slope differ from those of the
scanty waters of the Great Basin.
Means of Dispersal. — The most general are the alterna-
tions of winter and summer, leading birds and mammals to
migrate great distances to and from their breeding-places.
Ocean-currents are most important factors in the dispersal
of many marine and some laud animals. By means of such
great currents as the Gulf Stream, tropical animals are borne
to temperate and even subarctic regions ; and, on the other
hand, arctic and temperate animals are borne southward,
:and thus marine faunas interdigitate and merge insensibly
into one another. By this agency also new coral islands
are peopled from the mainland, and peninsulas are colo-
nized from adjoining continents or islands ; for example,
the southern extremity of Florida has been visited by trop-
ical plants and animals borne by currents and winds from
the West Indies, thus lending a purely tropical aspect to
the southern part, a semi-tropical fauna occupying the rnid-
•dle and northern part of the State.
Trade winds play an important part in scattering insects.
and especially the minute forms of life ; whirlwinds and
tornadoes catch up larger forms and transport them from
.stream to stream, pond to pond, and from lowlands to
highlands, and even to Alpine summits, where may some-
times be found, under loose stones, multitudes of insects
which have been borne up from below by strong gales or
ascending currents of air.
The direction of the migrations of the Rocky Mountain
locust seems to be mainly dependent on the direction of pr6-
mailing winds. Insects as well as birds are blown off-shore
GEOGRAPHICAL DISTRIBUTION. 661
sometimes for hundreds of miles, and in this apparently
haphazard way islands are, in part at least, supplied with
their quota of animal life.
Great rivers, like the Missouri, Mississippi, and the Ama-
zons, afford means of transportation from one part of a con-
tinent to another, from the interior to the seaboard, of
which many fishes, insects, and especially fluviatile mollusks,
avail themselves. Artificial means of crossing broad rivers
are offered, to insects especially, by country-roads and bridges
and railroad bridges, of which the potato-beetle and the
cabbage-butterfly have fully availed themselves. The Colo-
rado beetle has advanced steadily eastward, suddenly ap-
pearing in isolated points in New England, having appar-
ently been transported by through grain-cars from Chicago,
and has been carried to Europe in vessels. The European
cabbage-butterfly introduced into Quebec spread southward
into Maine along the Grand Trunk Railroad, into New
York along the railroads from Montreal to New York, and
then along the railroads to Washington.
Geological changes, such as the rise and submergence of
the edges of continents, and also the incoming and wane of
the glacial period, were still more general and fundamental
means of the dispersal and rearrangement of faunae.
Division ofithe Earth into Faunae.— When we go from
Maine to California we shall find that the faunistic features
of the country radically change three times. Leaving the
moist, temperate, forest-clad Atlantic region with its char-
acteristic animals, and entering on the broad, treeless, dry,
elevated plateau of the Kocky Mountains, we shall notice
that the Atlantic fauna has been replaced almost Avholly by
a new and strange assemblage ; and when we descend the
Pacific slope of the Sierra Nevada, there will be found to
be a second replacement, though much less marked than
the first. Again, when we pass from Labrador to the Isthmus
of Panama, we shall find several distinct fauna?, from an
arctic one to a purely tropical one. If we pause at Wash-
ington and analyze the fauna of that point, we shall see
that it is made up mainly of animals common to the Middle
Atlantic States, with an infusion of northern and southern
6G2 ZOOLOGY.
forms. Indeed, at almost any point in temperate North
America the fauna is found to consist of three elements — •
i.e., mainly a temperate, with a certain percentage of boreal
or subarctic and of southern or semi-tropical forms ; and if
the point be situated near some lofty range of mountains, a
fourth element — i.e., a purely arctic or alpine feature — is
superadded. The earth's surface may then be mapped out
into general and special divisions. First, a tropical, tem-
perate, and arctic or circumpolar fauna or realm, and, sec-
ondly, each continent may form a smaller subdivision or spe-
cific centre — i.e., the Europeo- Asiatic, the African, the Aus-
tralian, and the South and North American regions, for
each of these continental divisions have been peopled with
animals which have been from the earliest geological times
the original possessors of the soil, though they may have
adopted members of each other's faunae.
Confining ourselves to the North American Continent,
let us examine the distribution of life on its surface. We
shall have to throw out the arctic regions, which belong
with the arctic regions of Europe and Asia, to a distinct
circumpolar fauna or realm, and then map out the rest of
the continent into five provinces — i.e., the Canadian, the
Alleghanian, the Central or Rocky Mountains, the Pacific
or Calif ornian, and the Mexican ; all of these .provinces are
bounded by natural geological limits and differ in tempera-
ture and moisture. While the cougar, or Felis concolor, is
common to each one of them, and the bison and black bear
range throughout the Canadian, Alleghanian, and Central
provinces, there is a certain percentage of animals which
are confined to each province ; and on closer examination,
each province, especially on the Atlantic and Pacific coasts,
will be found capable of minuter subdivision into more lo-
cal faunae or faunulcB.
It will also be found that the animals, especially the
insects, of the Atlantic province have certain elements
reminding us of Northeastern Asia, while on the Pacific
slope — i.e., the Calif ornian province, a few insects, shells,
and Crustacea, as well as the birds, remind us of European
types, which are wholly wanting east of the Rocky Moun-
tains.
o
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a
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The Moose and other characteristic Canadian Mammals (Porcupine, Skuukv
and Jumping Mouse).-Af ter Wallace.
GEOGRAPHICAL DISTRIBUTION. 6G3
On inquiring into the origin of the North American
fauna, in the light of the geological history of the conti-
nent, we shall find, first, that immediately preceding the
glacial period, Arctic America was peopled by a flora and
fauna of which the larger proportion of the animals of the
continent north of latitude 30° are probably the descend-
ants ; and, second, that a number of species migrated north-
ward from the South American Continent. Now, when
the glacial period came in. the semi-tropical and warm tem-
perate animals of the northern two-thirds of the continent
were mostly swept out of existence ; a scanty arctic fauna
took their place ; as the ice melted and retreated to its pres-
ent limits, the present assemblage of temperate animals,
mostly modified descendants of those originally driven south,
migrated back again and colonized the region laid compara-
tively bare by the ice and cold of the glacial period. This
is an illustration of the sweeping extinctions, recolonizations.,
and extended migrations of animals on our continent in
former times, by which the existing relations of fauna? have
been brought about. Parallel events have occurred on the
Europeo- Asiatic Continent, and thus geological extinctions
and widespread migrations and recolonizations have taken
place ; and it is only in this way that the existing relations
in the geographical distribution of animals as well as plants
can be accounted for.
It should also be observed that in the beginning of
tilings the continents were built up from north to south —
such has been at least the history of the North and South
American and the Europeo-Asiatic and African Conti-
nents ; and thus it would appear that north of the equator,,
at least, animals slowly migrated southward, keeping pace,,
as it were, with the growth and southward extension of th&
grand land masses which appeared above the sea in the Pa-
leozoic Age. Hence, scanty as are the arctic and temperate
regions of the earth at the present time, in former ages these
regions were as prolific in life as the tropics now are, the
latter regions, now so vast, having all through the Tertiary
and Quaternary ages been undisturbed by great geological
revolutions, and meanwhile been colonized by emigrants
driven down bv the incoming cold of the glacial period.
ZOOLOGY.
It appears, then, that each continent has had from the
first its distinct assemblage of life, and thus opposing con-
tinents, such as South America and Africa, have fundament-
ally different fauna?, because they have had a separate geo-
logical history. Though the climate, moisture, and extent
of forests of Brazil and the West Coast of Africa may, for
example, be nearly identical, the animals are of a different
type. At the present day, Australian trees may be trans-
planted to California, and flourish there, and camels from
the Orient may breed in Southern California, because at the
present day the climate and soil are so much alike in the two
countries.
Distribution of Marine Animals.— Nearly all that has
been said thus far applies to land animals. Marine species
are assorted into faunas which are nearly as well marked as
terrestrial assemblages of species. The barriers restraining
them within their fauna! limits are the temperature of the
water, this being modified more or less by the ocean-cur-
rents, the nature of the shore, whether rocky or muddy or
sandy, and the nature of the sea-bottom, whether also
rocky, muddy, or sandy. Many marine animals live attached
to rocks and stationary pebbles, others are found only in
coarse or in fine sand, while the muddy bottoms of harbors,
bays, and gulfs, or the soft, deep ooze of the ocean-depths
harbor a different assemblage of mud-loving species. The
temperature of the water is the most important agency now
in operation in the limitation of marine animals. Thus
there is a tropical, north and south temperate, an arctic
and probably an antarctic zone, and these are, along the
shores of the different continents, subdivided into distinct
fauna?. For example, along the coast of Eastern North
America, the arctic or circumpolar fauna extends from the
polar regions to Labrador and Newfoundland ; a second,
the Acadian, to Cape Cod ; between Cape Cod and Capo
Hatteras another assemblage (the Virginian) is found ; from
Cape Hatteras to Southern Florida a fourth, and the Flor-
id an peninsula belongs to the tropical regions. Along these
different areas the water is of different temperatures. We
also find a large proportion of circumpolar animals in the
GEOGRAPHICAL DISTRIBUTION. 665
Acadian fauna and a few in the Virginian fauna, as the
Labrador or polar current passes down along the coast,
bathing the New England coast north of Cape Cod, and
even extending under the warm surface-water as far as New
Jersey. On the other hand, the great volume of heated
tropical water forming the Gulf Stream issuing from the
Straits of Florida makes its influence most sensibly felt as
far as Cape Hatteras, and in a diminished degree to Cape
Cod, and even southern shells, etc., are found as outliers of
more southern faunas near Portland, Me., and Nova Scotia.
As we descend from the shore into deep water, the tem-
perature becomes lower and lower the deeper we go, until
we come to a stratum or zone of water about o2°-36° Fahr.,
where circumpolar or arctic life alone abounds. Wherever
deep abysses off the coast or at the bottom of bays or gulfs
occur, the water is found to be colder than elsewhere ; just
as when we ascend a mountain the air becomes colder, un-
til at the Alpine summits we find an arctic temperature
and fauna ; thus, in the sea, increase of depth is paralleled
by increase of height on land.
Usually, off the coast of the United States, north of New
»/ '
York, there is a distinct zone of life between high and low
water, a second extending to the depth of about fifty fathoms,
and a third to one hundred fathoms or over. At a depth of
from one or two hundred fathoms in the Northern Atlantic,
and from five hundred to one thousand fathoms in the sub-
tropical and tropical seas, down to the deepest parts of the
ocean, now known in a few points to be about five miles in
depth, the water is about 33° Fahr. and the animal life is
polar in its nature. The water of the ocean all over the
globe, as shown by the results of the " Challenger" and
other expeditions for the exploration of the sea at great
depths, everywhere below a depth of one thousand fathoms,
is of an arctic temperature, overlaid by the heated water of
the tropics. The abysses or deeper parts of the ocean-bed
support a nearly uniform assemblage of life, which may bt>
called the deep-sea or abyssal fauna. The animals largely
consist of Echinoderms, notably Crinoids, with Coelentcratrs,
mollusks, worms, and Crustacea, and it is an interesting fact
6GG ZOOLOGY.
that a few of the Echinoderms belong to genera which flour-
ished in the Cretaceous Period ; so that in a sense the abys-
sal fauna may be said to be an extension in time of the
Cretaceous fauna ; the physical features of the deeper parts
of the sea having remained nearly the same, while the
shallower parts have risen and fallen so as to undergo great
changes, and have wrought corresponding changes in the life
along the shores of the continents.
The following tabular view of the chief zoological faunas
of the earth, proposed by Mr. J. A. Allen, is based on a
study of the mammals, but will primarily apply to most
land animals. The arctic realm is most distinctly charac-
terized by the distribution of marine invertebrates, where it
becomes of primary value :
I. Arctic realm, undivided.
II. North Temperate realm, with two regions, viz. :
1. American region, with four provinces, viz.:
a. Boreal.
6. Eastern.
c. Middle.
d. Western.
2. Europjeo-Asiatic region, also with four provinces, viz. :
a. European.
I). Siberian.
c. Mediterranean.
d. Manchuriau.
III. American Tropical realm, with three regions, viz. :
\. Antillean.
2. Central American.
3. Brazilian.
IV. Indo -African realm, with two regions, viz. :
1. African region, with three provinces, viz. j
a. Eastern.
b. Western.
c. Southern.
GEOGRAPHICAL DISTRIBUTION. 667
2. Indian region, with two provinces, viz. :
a. Continental.
b. Insular.
V. South American Temperate realm, with two provinces, viz.:
a. Andean.
b. Pampean.
VI. Australian realm, with three regions, viz. :
1. Australian, with two provinces, viz. •
a. Australian.
b. Papuan.
2. Polynesian.
3. New Zealand.
VII. Lemuriau realm, undivided.
VIII. Antarctic or South Circumpolar, undivided.
Migrations of Animals. — Intimately connected with zoogeog-
raphy are the migrations of animals, especially birds. Nearly all the
birds of the United States which breed in the central and northern
portions pass southward in the autumn, and winter in the Southern
States or hi Central America and the West Indies. Most of the birds
which breed in Northern and Central Europe fly at the approach of
cold weather into Southern Europe or across the Mediterranean into
Northern Africa. The causes of this regular periodical migration are
probably due, primarily, to the changes of the seasons and to the want
of food in the colder portion of the year, and, secondarily, to the
breeding habits of birds.
The periodical migrations of fishes from deep to shoal water are
connected with their breeding habits, the marine fish being in most
cases compelled to spawn in rivers or in shoal-water. The migratory
movements of fishes along the coast are probably connected with the
presence or absence of their accustomed food.
The partial, occasional migrations of locusts depend on the undue
increase in the numbers of the insects, and the consequent lack of
food, while the direction of the swarms is largely dependent on the
general course and force of the winds.
CHAPTER XII.
THE GEOLOGICAL SUCCESSION OF ANIMALS.
THE different systems of rocks, from the Silurian to the
Quaternary or present age, contain the fossil remains of ani-
mals, which show that in the beginning the animals were,
as a whole, unlike those now living, the later types becom-
ing more and more like those now constituting the earth's
fauna. The oldest set of animals, the Palaeozoic, comprised
species of nearly all the branches of: invertebrates, with a
few fishes. A large proportion of these animals belonged
either to simple or to what are called generalized types,
though some were as specialized as any invertebrates now
living. Progress upward has involved the disappearance of
most of the generalized types, and their replacement by more
or less highly specialized types. Thus the earliest corals were
mostly of the Rugose type, which were succeeded by the
more complicated recent forms ; the Brachiopods or shelled
worms were replaced by mollusks ; the generalized trilobites
gave way to the genuine specialized shrimps and crabs ; tbe
existing generalized king-crab, with its affinities to spiders,
has survived a number of still more generalized or synthetic
allies. The generalized sharks and ganoids abounded at a
time when there were no bony fishes like the cod and her-
ring. Nearly nine thousand species of bony fishes have
appeared since the extinction of the earlier types of cartila-
ginous and mail-clad fishes. The highly specialized horse
was preceded by a number of more generalized species and
genera, the oldest of which approached the tapir, one of the
most generalized of mammals. The succession of forms
leading up to the horse is paralleled by the succession of
GEOLOGICAL SUCCESSION OF ANIMALS.
sea-urchins and of ammonites, the older being of simpler,
more generalized forms, and the later with a greater
specialization or elaboration of the different, especially ex-
ternal, hard parts of the body.
When we ascend to the Amphibians, the reptiles and the
mammals, we shall find that there has been an elaboration
or working out into great detail, of the parts most used by
the animal, this differentiation being more and more marked
as we approach the present time ; and this has been in ac-
cord with the building up of the continental masses, and
the differentiation or specialization of the surface of the
different continents into plains, plateaus, highlands, and
mountain ranges, with their different climatic features,
and the dividing up of the waters into mediterranean
seas, friths, fiords, rivers, and lakes. Thus the extinction
of successive faunae all over the globe has been followed by
the appearance of new sets of animals, each assemblage be-
ing adapted to the new and improved condition of things.
Having seen that the earlier forms of life were of a sim-
pler form, though often combining the features of diverse
classes and orders of animals which appeared afterward, so
that Agassiz called them, in some cases, prophetic types,
combining as they did characters which have been trans-
mitted to two or more later groups, and these specially elab-
orated, so that such generalized or prophetic types serve as
points of departure from which several series of forms have
arisen — having traced the law or principle underlying the
geological succession of animals, we may inquire whether
this has been paralleled by the development of any one of
the members of a group. That this is the case has been
proved by Hyatt, who shows that the development of the
individual Ammonite is paralleled by that of the geological
succession of the members of the order to which it belongs.
Stalked Crinoids were the style in Palaeozoic ages, while free
Crinoids are more abundant at the present day ; and we
have seen that in the individual development of the existing
Antedon, the young is stalked at first, afterward becoming
free. The young, bony fish has at first a cartilaginous
skeleton and a heterocercal tail, these being characteristics
670 ZOOLOGY.
of early fishes. The earlier Batrachians were tailed, the
tailless toads and frogs in general appearing last, as the
tadpole precedes the frog condition.
Extinction of Species. — The laws governing the extinction
of animals are obscure, but we know that geological extinc-
tions must have been due to natural causes, since the earth
has at different periods evidently undergone great changes,
sufficient to account for the death of such species as were
unable to withstand the oscillations and changes of climate.
In Palaeozoic times existed multitudes of animals which, judg-
ing by their descendants of later times, belonged to old-fash-
ioned, obsolete, useless types. They cumbered the ground,
and were destroyed by the beneficent action of unerring natu-
ral laws promoting the decay and extinction of antiquated
forms, and the recreation, by the laws of transmission with
modification, of new, improved types, useful in their day and
generation as stepping-stones to a still higher, more improved
stock. That the extinction was due to causes acting pri-
marily from without, and secondarily from within by trans-
mission force, seems demonstrated when we take into ac-
count the destruction of life which we know took place
during and at the close of the Glacial Period, when the
earth was swept with glaciers, and afterward garnished
with the vegetation and fresh life of the post-glacial times,
and made ready for the abode of man. Thus the death of
species by the action of laws that we can comprehend in-
volves the recreation of new and improved animal forms by
laws that we can at least in part, if not fully, understand.
CHAPTER XIII.
THE ORIGIN OF SPECIES.
THE extinction of species was in some cases gradual, in
others sudden, so in all probability as different assemblages
of life became slowly extinct new forms as slowly originated
from them by genetic descent and took their places. While
here and there certain species, under favorable circumstances,
suddenly appeared, if we could have been there to look on,
it would perhaps have been as difficult to have observed the
process as it is at the present day to observe the changes
going on in the relation of existing faunas. We know,
however, that changes are going on in the world of life about
us, that the balance of nature is being disturbed.
The nature of the evidence tending to prove that species
have originated through the agency of physical and biologi-
cal laws is mainly circumstantial, there being comparatively
few facts in demonstration of the theory, the direct act of
transformation of one species into another under the eye of
scientific experts having never been observed.
Seasoning d priori, we assume that organisms, both
plant and animal, have been created by development from
pre-existent forms because it agrees with the general course
of nature. All the events in geology, as in physics and as.
tronomy, being due to the operation of natural laws, it is
reasonably supposed that the production of all the species
of plants and animals from original simple forms, like the
Monera or bacteria, have been the result of the action of
natural law. The study of the early forms of life found in
the Palaeozoic strata ; the laws of the succession of types ; the
correlation existing between the development of the indi-
672 ZOOLOGY,
vidual and of the members of the class to which it belongs ;
the parallelism between the formation and differentiation
of the land-masses of the globe and the successive extinc-
tions and creations of plants and animals — all these facts,
notwithstanding the imperfections of the geological record,
and the fact that many of the older forms of animals were
nearly as much specialized as those now living ; tend strongly
to prove that, on the whole, the world as it now exists has
been the result of progressive development, one form com-
ing genetically from another ; the animal and plant worlds
constituting two systems of blood relations, rather than sets
of independent creations.
When to more special studies of those species which live
in extraordinary environments, such as cave-animals, para-
sitic animals, brine-inhabiting animals, Alpine forms and
certain deep-sea species, we add the study of rudimentary
organs in adult animals, of temporary, deciduous organs in
young or larval animals ; when we compare the metamor-
phoses of some species congeneric with others which undergo
no transformations ; when we study the delicate balance in
nature as observed in the geographical distribution of ani-
mals ; the harmony in nature between species and their en-
vironment ; protective coloration and resemblance in form,
the relations between carnivorous and herbivorous creatures,
the struggle for existence between animals, we are forced
to acknowledge that the operations of nature, as a whole,
tend, on the one hand, to the origination of new forms
and the preservation of those which are useful, or, in other
words, are in harmony with their surroundings ; and, on the
other hand, to the destruction of those which are incapaci-
tated by changes in their environment for existence in what
has been and now is a constantly changing, progressive
world.
Again, reasoning by induction, as an actual fact we know
that species vary ; that hardly any two experts agree exactly
as to the limitation of species ;* that varieties tend to break
* As one of many examples, we may cite the fact that fifty-nine nom-
inal species of the squirrels have been described as inhabiting tropical
America, but lately the number has been reduced to twelve.
THE ORIGIN OF SPECIES. 673
up into races, and that no two individuals of a race are ex-
actly alike. Where the climate and soil remain the same,
the species tends to remain fixed and stable ; remove the
stability in the environment, or subject the individuals of a.
species to changes of soil and temperature, and expose ib
more than usual to the attacks of its natural enemies, it
then begins to undergo a change. This is seen in those in-
dividuals of a species which live on the borders of lowland*
and highlands, of deserts and fertile tracts, of salt and
brackish water, of shallow and deep water, and of polar and
temperate zones, or to the influence of alternating cold and
warm weather. When, as in some cases, climatic or other
agencies suddenly change, we may have species and even
genera suddenly appearing, as is known to be the case in
the change of one genus to another of brine shrimps when
the water changes from brackish to a brine, as worked out
by Schmankevitch in Russia.
The struggle for existence resulting in the survival of the
fittest is a fact now generally observed. The cod may de-
posit several millions of eggs, but of this immense number
only one or a few pair of adults survive ; there are probably
no more codfish now than two centuries since — indeed, not
as many ; the eggs are devoured by different animals, the
young fish, as soon as hatched, form the food of larger fish,
half-grown cod serve to supply the wants of larger animals,
until finally the survivors may be to the original number of
eggs as one to a million. The queen bee may, during her
whole life, lay more than a million of eggs, the queen
white ant may lay eighty thousand eggs a day, an Aphis
may be the mother of a hundred young, those hundred may
each produce their centesimal offspring until the result in one
season, at the end of the tenth generation, amounts to a
quintillion of plant-lice ; but most of these insects serve as
food for other species, many die of disease and cold, until
at the end of the season only one or several pairs survive to
lay a few eggs, which represent the species in the winter-time.
Lastly, the variation in domestic animals, the result of
the subjection of the species to influences not felt in what
we call a state of nature, is an indication that animals not
674 ZOOLOGY.
exposed to human interference may vary when subjected to
changes in their environment. Also the fact that man can, by
careful selection, breed races of horses adapted for draught,
speed, or the road ; races of cows for different qualities of
milk ; beeves for meat ; races of sheep for pre-eminence in
the quality of their wool or mutton, or races of doves or
poultry for beauty, usefulness, or other qualities ; the fact
that gentleness, and generally good mental qualities, can be
made to replace viciousness in horses, cattle, dogs — all these
and many other facts, in the art of breeding animals knoAvn
to fanciers, indicate that nature has, through the past ages,
by the operation of natural laws, evolved races and species
of animals which have followed constantly improving lines
of development, the outcome of which are creatures the best
fitted to withstand the struggle for existence, the most use-
ful in the scheme of nature, and the most in harmony with
the world about them. Progress, on the whole, therefore,
has been beneficent, the best proof of which is the last
[product of evolution, man, the paragon of creation.
Lamarck laid the foundations of the doctrine of evolution, the fac-
tors he suggested being changes in the environment, inducing new needs
and desires in animals, and consequent use and disuse of organs, also
the transmission by heredity of characters acquired during the lifetime
of the individual. But his docfiues were published, in 1809. in very
•crude shape, and before the sciences of geographical distribution, em-
bryology, palaeontology, and of histology -were adequately understood
or had even been founded. Lamarckism in its modern form is called
Neolamarckism. It comprises the fundamental factors of evolution.
Darwin in 1859 published the principle of natural selection and its
.general application, and supported it upon such broad grounds that it
was universally accepted. Herbert Spencer insisted on the fact of
" the survival of the fittest." Neolamarckism endeavors to explain the
origin of variations, and thus lays the foundation on which natural
selection rests.
We may with some changes adopt the following tabular view by
>Giard of the factors of organic evolution:
{Direct. — Changes of cosmical environment, changes of
climate, light, darkness, temperature, dryness and
humidity, physical and chemical constitution of the
p . soil and of waters, mechanical state of the milieu,
",ni winds, currents of water, biological environment,
food, parasitism, symbiosis.
Indirect. — Reaction against cosmical environmental
conditions; adaptation, convergence, reaction against
[ biological conditions, mimicry.
TT ,., , I Heredity, vital concurrence, natural and sexual selec-
11. beco aryl tion segregation, geographical isolation, amixia,
rs' f hybridity. "
CHAPTER XIV.
PROTECTIVE RESEMBLANCE.
CLOSELY related to the foregoing subjects is the protective
resemblance or " mimicry" of natural objects by which spe-
cies of animals are preserved from extinction. Animals may
" mimic" or imitate, or be assimilated in shape or in color
to natural objects, as stones, lichens, dry bushes, the bark
of trees, or portions of leaves, or entire leaves, fresh or
dried, and their stems, or so closely imitate other animals
which enjoy an immunity from attack as to escape notice
or attacks from their enemies, and thus prolong their own
lives and that of their species.
The animal is, as a rule, unconscious that it is thus pro-
tected ; though there are examples, as in the case of the
trap-door and other spiders, which cover their holes in such
a way to avoid notice that it would appear as if they were
semi-conscious or aware of what they were doing.
In the first place, we know that animals may be deceived,
as is proved by the various subterfuges employed by hunters
in tolling or deceiving the larger quadrupeds, the use of
decoy-ducks, by which water-fowl are often thoroughly de-
ceived and brought within reach of the gun.
The disguises worn by animals, the exquisite adaptation
of the colors of their fur or feathers to their surroundings,
are part of the general harmony existing throughout nature.
Desert animals are rusty or light-colored ; birds and insects
and lizards, as well as frogs and tree-toads, which live among
trees, are green ; those which live among the trunks and
larger branches of trees assimilate in color to the color of
the bark. The cougar, which clings to the trunk of some
676
ZOOLOGY.
tree, prepared to spring upon the deer passing underneath,
is protected from observation by its brown neutral color,
while the bars and lines of the tiger are said to resemble the
lights and shades of the jungle grass in which it lies in wait
for its prey. The prairie-dog, the deer, buffalo and ante-
lope on the "Western plains, are concealed by their resem-
blance in color to the soil, or to the bushes on its surface.
Among insects, the grasshoppers nearly always harmonize
in color with the general hue of the fields in which they
abound ; insects on light-colored sandy beaches are often
pale, as if bleached out by the sun's rays. Alpine and arctic
butterflies and moths, which have limited powers of flight,
when nestling on lichen-covered rocks, are difficult to detect.
Fig. 542.— A Katydid-like form resembling a leaf.
Certain orthopterotis insects resemble leaves ; such are
certain katydids (Fig. 542), and especially the famous leaf-
insect, Pliyllium siccifolium Linn. (Fig. 543), which strik-
ingly resembles a green leaf. The stick-insects (Fig. 544
also would be easily mistaken for the twigs of trees or stalks
of leaves, one species (Fig. 544) representing a moss-grown
twig. The under sides of the wings of our native Graptu
butterflies have the color of dead leaves, so that when they
are at rest they resemble a withered dry leaf. The most
perfect resemblance to a leaf with its stem is the Kallima
butterfly when setting at rest with its wings folded over its
PROTECTIVE RESEMBLAKCE.
677
Fig. 543.— Leaf insect (Phy-
liunf). Half natural size.
back. The caterpillars of the geometrid moths often won-
derfully mimic the stems of the plants they feed upon, in
color and markings, even to the
warts and tubercles on their skin.
As an example of possibly con-
scious mimicry or effort at conceal-
ing their nest from the search of
their enemies, may be cited the trap-
door spider observed by Moggridge
in Southern Europe. This spider
digs its hole among moss and small
ferns, and after the trap-door is
made the top is covered with growing
ferns, etc. , transplanted by the spider,
and the deception is so perfect that
Mr. Moggridge found it difficult to detect the position of
the closed trap, even when holding it in his hand.
Mimicry of other insects is of
very frequent occurrence, certain
flies resembling bees in appearance
and the sounds or buzzing they
make ; the Syrphus flies closely
imitate wasps. Fig. 545 illustrates
a case observed by Belt in Nicara-
gua, where a wasp (Priocnemis) is
mimicked by a hemipterous insect
(Spiaif/er luteocornis Walker, the
left-hand figure) in every part,
even to its vibrating, brown, semi-
transparent wings and its wasp-like
motions. Here the bug is evidently
protected by its resemblance to the
wasp, for whose ferocity and sharp
sting
insects have
all unarmed
great respect.
Some butterflies are distasteful
to birds, and there are other but-
terflies which have no bad taste,
Fig. 544.— Stick insect.
but closely resemble in
color such species as are passed over by birds. Thus,
678
ZOOLOGY.
Danais arcJiippus, a common large butterfly, is not eaten
by birds on account of its pungent odor, which is disagree-
able to them. Another butterfly, Limenitis disippus, a
smaller but similarly colored butterfly, which is inodorous,
is supposed to be mistaken by the birds for the Danais, and
thus escapes destruction.
Belt says that in Central America stinging ants are not
only closely copied in form and movements by spiders, but
by species of Hemiptera and Coleoptera ; as stinging ants
are not usually eaten by birds, this disguise is thought to
protect the various forms which imitate them.
Many highly-colored caterpillars, which live exposed on
the leaves of plants, are not eaten by birds, owing to their
bad taste. This and other bright-colored insects may be said
Fig. 545. — Wasp mimicked by a bug, — After Belt.
to hang out danger-signals to warn off hungry birds. Mr.
Belt, in his " Naturalist in Nicaragua," suggests that the
skunk is an example of this kind. " Its white tail, laid
back on its black body, makes it very conspicuous in the
dusk when it roams about, so that it is not likely to be
pounced upon by any of the Carnivora mistaking it for other
night-roaming animals." He also cites the case of a very
poisonous, beautifully banded coral snake (Elaps), which is
" marked as conspicuously as any noxious caterpillar with
bright bands of black, yellow, and red." This author also
found that while the frogs in Nicaragua are dull or green-
colored, feeding at night, and all preyed upon by snakes
and birds, one little species of frog, dressed in a bright liv-
PROTECTIVE RESEMBLANCE. 679
ery of red and blue, hops about in the day-time, and, as he
proved by experiment, is thoroughly distasteful to fowls
and ducks.
We have seen that many animals resemble externally those
above them in the scale of life ; in the synthetic or general-
ized types from which the more specialized forms have prob-
ably originated, there are characters which cause them to
resemble more recent, new-fashioned types. It is possible-
that in many cases the older types, doomed as they were to
destruction, have had their existence prolonged by their
protective resemblance to modern types.
For example, the Neuroptera as a group are geologically
of high antiquity ; owing to geological extinction, but few
species, compared with those of other orders, have survived j
and those which are now living often resemble members of
higher, more recent orders. The inference is, then, that
the mimickers have survived by reason of their resemblance
to the more abundant forms which appeared, as the more
old-fashioned types were waning or dying out.
Certain Brazilian species of the lepidopterous family,
Zyycenidce and Bombycidce, mimic in form and coloration
certain butterflies, especially the Heliconiihe, which abound
in Brazil. The former groups are evidently the older geo-
logically, as there are wide gaps between the genera ; and
the indications are that these butterfly-like moths have
likewise, from their resemblance to the more abundant Heli-
conidce, been preserved. It thus appears that protective
mimicry may be an important factor in the preservation of
species.
LITERATURE.
Bates. Contributions to the Insect Fauna of the Amazon Valley.
Lepidoptera: Helicouidse. Trans. Liuuean Society, London, xxni-
1862.
Wallace. Contributions to the Theory of Natural Selection. 187<X
—On the Phenomena of Variation and Geographical Distribution
as illustrated by the Papilionidce of the Malayan Region. Trans. Lin-
iiean Soc., London, xxv. 1805.
Trimen. On some Remarkable Mimetic Analogies among African
Butterflies. Trans. Linnean Soc., London, xxm. 1869.
Poulton. The Colors of Animals. 1890.
With the writings of Darwin, Weismann, Fritz Muller, Meldola,
G. W. and E. G. Peckham, Butler, Beddard, Riley, Lubbock, Weir,
Morse, etc.
CHAPTER XV.
INSTINCT AND SEASON IN ANIMALS.
WE have seen that animals have organs of sense, of per"
eeption, in many cases nearly as highly developed as in man,
and that in the mammalia the eyes, ears, organs of smell
and touch differ but slightly from those of our own species ;
also that the brain and nervous system of the higher mam-
mals closely approximate to those of man. We know that
all animals are endowed with sufficient intelligence to meet
the ordinary exigencies of life, and that some insects, birds,
and mammals are able, on occasion, to meet extraordinary
emergencies — in other words, to rise with the occasion.
These occurrences indicate that what usually goes by the
name of " instinct ' is more or less pliable, unstable ;
that animals are in a limited degree free agents, with powers
of choice. Moreover, those naturalists who observe most
closely and patiently the habits of animals do not hesitate
to state their belief that animals, and some more than
others, possess reasoning powers which differ in degree
rather than in kind from the purely intellectual acts of
man.
As a matter of not infrequent observation, animals exer-
cise the power of choice, they select this or that kind of
food, prefer this or that kind of odor, and have their likes
and dislikes to certain persons, and all this aside from mere
physical stimulation of the senses. Moreover, animals are
subject to the passions, they show anger, even when not
hungry or under the domination of the reproductive in-
stincts ; their sounds express dissatisfaction or contentment.
Indeed, many facts could be stated showing that animals
INSTINCT AND REASON. 681
not only have feelings, intelligence, and volition, but are
possibly, in a very slight degree, self-conscious. The fact
that animals exercise discrimination in the selection of
food, in the choice of a flower or object of one color in
preference to another, in perceiving likeness or unlikeness in
two objects, indicates that they can exercise the power of
intelligent discrimination, as has been said by Mr. G. H.
Lewes :* " When there is no alternative open to an action
it is impulsive ; when there is, or originally was, an alter-
native, the action is instinctive ; where there are alterna-
tives which may still determine the action, and the choice
is free, we call the action intelligent."
Indeed, animals have the principle of similarity strongly
developed. It is the bond that holds together the social or-
ganizations of such insects as live in colonies, and such fish,
birds, or mammals as go in schools, flocks, or herds. Were
it not for this mental quality some species would tend to
die out.
Animals possess memory, which consists in storing up in
the mind the results of external impressions, so that they
are enabled to perceive the points of resemblance or differ-
ence between two objects, after having been out of sight of
them for a greater or less length of time. Bain defines
memory, acquisition or retention, as " being the power of
continuing in the mind impressions that are no longer stim-
ulated by the same agent, and of recalling them afterward
by purely mentaJ forces. 5>
With the aid of memory, birds make their migrations,
bees and ants find their way back to their nests. As we
have elsewhere said, " No automaton could find its way
back to a point from which it had once started, however
well the machine had been originally wound up. Xor does
the common notion of an inflexible instinct meet the case.
Memory is often due to a repetition of certain experiences,
and experiences lay the foundation for instinctive acts ; it
is the sum of these inherited experiences which make up
the total which passes under the name of instinct, "f
* Article on Instinct in Nature, April 10th, 18?::.
\ Half Hours with Insects, p. 374.
(582 ZOOLOGY.
It would appear, then, that animals have in some slight
degree what we call mind, with its threefold divisions of the
sensibilities, intellect, and will. When we study animals in
a state of domestication, especially the dog or horse, Ave
know that they are capable of some degree of education,
and that they transmit the new traits or habits which they
have been taught to their offspring ; so that what in the
parents were newly acquired habits become in the descend-
ants instinctive acts. We are thus led to suppose that the
terse definition of instinct by Murphy, that it is " the sum
of inherited habits," is in accordance with observed facts.
Indeed, if animals have sufficient intelligence to meet the
extraordinary emergencies of their lives, their daily, so-
called instinctive acts, requiring a minimum expenditure of
mental energy, may have originated in previous genera-
tions, and this suggests that the instincts of the present
generation may be the sum total of the inherited mental ex-
periences of former generations.
Descartes believed that animals are automata. Lamarck
expressed the opinion that instincts were due to certain in-
herent inclinations arising from habits impressed upon the
organs of the animals concerned in producing them.
Darwin does not attempt any definition of instinct ; but
he suggests that " several distinct mental actions are com-
monly embraced by this term," and adds that " a little
dose, as Pierre Huber expresses it, of judgment or reason
often comes into play, even in animals low in the scale of
nature." He indicates the points of resemblance between
instincts and habits, shows that habitual action may become
inherited, especially in animals under domestication ; and
since habitual action does sometimes become inherited, he
thinks it follows that " the resemblance between what origi-
nally was a habit and an instinct becomes so close as not to
be distinguished. " He concludes that, by natural selection,
slight modifications of instinct which are in any way useful
accumulate, and thus animals have slowly and gradu-
ally, " as small consequences of one general law," acquired,
through successive generations, their power of acting in-
INSTINCT AND REASON. 683
stinctively, and that they were not suddenly or specially
endowed with instincts.
Rev. J. J. Murphy, in his work entitled " Habit and In-
telligence," seems to regard instinct as the sum of inherited
habits, remarking that " reason differs from instinct only
in being conscious. Instinct is unconscious reason, and
reason is conscious instinct." This seems equivalent to
saying that most of the instincts of the present generation
of animals is unconscious automatism, but that in the begin-
ning, in the ancestors of the present races, instincts were
more plastic than now, such traits as were useful to the or-
ganism being preserved and crystallized, as it were, into the
instinctive acts of their lives. This does not exclude the
idea that animals, while in most respects automata, occa-
sionally perform acts which transcend instinct ; that they
are still modified by circumstances, especially those species
which in any way come in contact with man ; are still in a de-
gree free agents, and have unconsciously learned, by success
or failure, to adapt themselves to new surroundings. This
view is sti-engthened by the fact that there is a marked de-
gree of individuality among animals. Some individuals ot
the same species are much more intelligent than others,
they act as leaders in different operations. Among dogs,
horses, and other domestic animals, those of dull intellect
are led or excelled by those of greater intelligence, and this
indicates that they are not simply automata, but are also in
a degree, or within their own sphere, free agents.
LITERATURE.
Romanes. Animal Intelligence. 1883. — Mental Evolution in Ani-
mals. 1884.
Bastian. The Brain as an Organ of Mind. 1880.
James. Psychology. Chapter XXIV. 1890.
See also the works of Darwin.
BIBLIOGKAPHY.*
GENERAL ZOOLOGY.
Elements of Comparative Anatomy. By Carl Gegenbaur. London,
1878.
A Manual of the Anatomy of Vertebrated Animals. By T. II. Hux-
ley. London, 1871.
A Manual of the Anatomy of Invertebrated Animals. By T. H.
Huxley. New York, 1878.
Forms of Animal Life. By George Rollestou. Oxford, 1888.
Coues and Kingsley's Standard Natural History. 6 vols. Boston,
1884-85.
Handbuch der Zoologie. Band 1, Wirbelthiere, Mollusken und Mol-
luscoiden, von J. Victor Carus, Leipzig, 1868-1875 ; Band 2, Arthropo-
den, von A. Gerstaecker ; Raderthiere, Wiirmer, Echinodermen, Coelen-
teraten und Protozoen, von J. Victor Carus, Leipzig, 1863.
Bronn's Classen und Ordnungen der Thierreichs. Protozoa, Radiata,
Crustacea, Amphibia, (Other parts incomplete.) Leipzig und Heidel-
berg.
Wiedersheim. Elements of the Comparative Anatomy of Verte-
brates. 1886.
Parker. On Mammalian Descent. London, 1885. And his works on
the morphology of the skeleton of fishes, reptiles, birds, and mammals.
The Anatomy of Vertebrates. By R. Owen. 3 vols. London, 1868.
A Key to the Birds of North America. By Elliott Coues. Boston.
Ridgway's Manual of North American Birds. 1887.
The Birds of North America. 3 vols. By S. F. Baird, T. M.
Brewer, and R. Ridgway. Land Birds. Boston, 1874.
Contributions to the Natural History of the United States. By L.
Agassiz. 4 vols. Boston, 1857-1862.
Mind in Nature. By H. J. Clark. New York, 1865.
Manual of the Vertebrates of the Northern United States. By D. S.
Jordan. Fifth edition. Chicago, 1888.
Seaside Studies in Natural History. By E. C. Agassiz and Alexander
Agassiz. Radiata. Boston, second edition, 1871.
Introduction to Entomology. By W. Kirby and W. Spence. 4 vols.
London, 1828.
* Works used in the preparation of this volume, with the titles of others indispen-
sable to the student.
686 ZOOLOGY.
Manual of Entomology. By H. Burmeister. London, 1836.
Guide to the Study of Insects. By A. S. Packard, Jr. Eighth
edition. New York, 1883.
Invertebrate Animals of Vineyard Sound. By A. E. Verrill. (Re-
port U. S. Commissioner of Fish and Fisheries.) Washington, 1873.
Invertebrata of Massachusetts. By A. A. Gould. Edited by W. G.
Binney. Boston, 1870.
Lang. Text-book of Comparative Anatomy. Pt. I. 1891.
Manual of the Mollusca. By S. P. Woodward. Second edition.
London, 1868.
Corals and Coral Islands. By J. D. Dana. New York, 1872.
Introduction to the Osteology of Mammalia. By W. H. Flower. 1870.
Flower and Lydekker. Introduction to the Study of Mammals.
London, 1891.
Elementary Text-book of Zoology. By C. Claus. Translated by
A. Sedgwick. 2vols., 8vo. London, 1884-5.
Practical Biology. By T. H. Huxley and H. N. Martin. 1889.
Parker's Zootomy. 1889.
Parker's Lessons in Elementary Biology. 1891.
With the works and monographs of Dana, Wymau, Leidy, L. and A.
Agassiz, H. J. Clark, Cope, Gill, Hyatt, Verrill, Scudder, Binney,
Allen, Coues, Smith, Baird, Ridgway, Brewer, Ball, Cooper, Wilder,
Riley, Uhler, Edwards, Grote, Le Conte, Hagen, Scammon, Stimpson,
Jordan, Morse, Thomas, Gould, Bland, Prime, Tryon, Gabb, Packard,
and others, and the standard works of Linnaeus, Cuvier, Von Baer,
Leuckart, Gegenbaur, Haeckel, St. Hilaire, Huxley, Mivart, Allman,
Hincks, Shuckard, Westwood, P. J. and E. Van Beneden, Brandt,
Ratzburg, Bunneister, Oscar Schmidt, Melschnikoff, Kowalevsky,
Kupffer, and many others.
The student should also consult the following serials : American Jour-
nal of Science and Arts, New Haven, Conn. ; The American Naturalist,
Philadelphia ; Nature, London ; Quarterly Journal of Microscopical
Science, London ; Archiv fur Naturgeschichte, Berlin ; Annals and
Magazine of Natural History, London ; Aunales des Sciences Naturelles,
Zoolosrie, Paris; Siebold und Kolliker'sZeitschrift; Journal of Mor-
phology, Boston, 1887; Canadian Entomologist; Psyche; The Auk,
New York.
Descriptions of North American animals and essays on their anatomy ,
physiology, and development are to be found in the Transactions and
Proceedings of the following scientific societies : American Academy
of Arts and Sciences, Boston ; American Philosophical Society, Phila-
delphia ; Academy of Natural Sciences, Philadelphia ; Boston Society
of Natural History ; Smithsonian Institution ; American Entomologi-
cal Society, Philadelphia ; Museum of Comparative Zoology, Cam-
bridge, Mass. ; Essex Institute ; Peabody Academy of Science, Salem;
Academy of Sciences, San Francisco, Cal. ; and other societies in Port-
land, Me. ; Buffalo, N. Y. ; Davenport, Iowa; St. Louis, Mo., and
Charleston, S. C. ; New York and New Haven.
BIBLIOGRAPHY. 687
HISTOLOGY.
Handbook of Human and Comparative Histology. By S. Strieker.
New York, 1872; Frey's Histology, 1886; Stirling's Histology, 1890.
And the monographs or essays of Leydig, Clark, C. S. Minot, etc.
PHYSIOLOGY.
Treatise on Human Physiology. By J. C. Dalton. Philadelphia.
Elementary Lessons in Physiology. By T. H. Huxley. Fourth
edition. London, 1870.
Text-book of Physiology. By M. Foster. London, 1877, 1891.
The Human Body. By H. Newell Martin, N. Y. , 1881.
EMBRYOLOGY.
Entwicklungsgeschichte der Thiere. Von Baer. Konigsberg, 1828.
Entwicklungsgeschichte des Menschen. Von A. Kolliker. 1861.
Elements of Embryology. By M. Foster and F. M. Balfour. 1874.
A treatise on Comparative Embryology. By F. M. Balfour. 1880.
Hertwig. Text-book of Embryology. Man and Mammals. 1892.
Korschelt and Heider. Text-book of Embryology. Invertebrates.
1892.
With the monographs of Wolff, Harvey, Barry, Coste, Pouchet,
Von Baer, Remak, Bischoff, L. and A. Agassiz, Weismanu, Metsch-
uikoff, Huxley, Balfour, Parker, and others.
ZOOGEOGRAPHY.
The Geographical Distribution of Animals. By A. R. Wallace.
2 vols. New York, 1876. Murray's Distribution of Mammals.
With the essays of Agassiz, Baird, Allen, Verrill, Ridgway, Gill,
Murray, Merriam, Packard, and others.
EVOLUTION AND RELATION OP ANIMALS TO THEIR ENVIRONMENT.
Philosophic Zoologique. ft J. B. de Lamarck. 8vo, 2 vols. 1809.
On the Origin of Species. By Charles Darwin. New York, 1871.
The Origin of Genera. By E. D. Cope. Philadelphia, 1861.
Contributions to the Theory of Natural Selection. By A. R. Wal-
lace. New York, 1870. Wallace's Darwinism. 1890.
On the Origin of Species. By T. H. Huxley. New York. 1863.
With the essays of Cope, Hyatt, Wagner, Weismann. Haeckel,
Kupffer, Palmen, Romanes, Semper, Gulick, Packard, and others.
NATURAL HISTORY OF MAN.
De Generis Humani Varietate Nativa. Von J. F. BlumenbacU.
Editio 3. Gottingen, 1795.
688 ZOOLOGY.
Researches into the Physical History of Mankind. By J. C. Prich-
ard. London, 1851.
Types of Mankind. By J. C. Nott and G-. R. Gliddon. Philadel-
phia, 1854.
Natural History of the Varieties of Man. By R. G. Latham. Lon-
don, 1850.
Races of Man. By Charles Pickering. London, 1863.
Evidence as to Man's Place in Nature. By T. H. Huxley. New
York, 1863.
Prehistoric Times. By Sir John Lubbock. London, 1872.
Natural History of the Human Species. By H. Smith. Edinburgh,
1852.
Brinton's Races and Peoples. 1890.
Briuton's The American Race. 1891.
De Quatrefages' The Human Species.
Tylor's Anthropology.
Tylor's Primitive Culture.
With the works and essays of Retzius, Wilson, Mortillet, Broca,
Lartet, Von Baer, St. Hilaire, S. Van der Kolk, Vrolik, Schaaffhausen,
Rlitimeyer, Busk, Morgan, Wyman, Squire, Davis, Schmerling, Wag-
ner, Vogt, Rolle, Quatrefages, Tylor, Bastian, Ratzel, Dall, Abbott,
Putnam, Holmes, Fewkes, Mason, Morse, and others.
GLOSSARY.
AB-DO'MEN. In mammals the part
of the trunk below or behind
the thorax; in insects the third
region of the body, or hind
body.
AB ER'RANT. Departing from the
regular or normal type.
AB-O'RAL. Opposite the oral or
mouth region.
A-BRAN'CHI-ATE (Gr. a, without;
bragchia, gills). Without bran-
chiae or gills.
A-cu 'MI-NATE. Ending in a pro-
longed point.
AL-VE'O-LUS. A cavity forming
the socket in the jaws of verte-
brates for the teeth.
AM-BU-LA'CRUM (Lat. from ambu-
lare, to walk, a garden-walk).
The perforated space or area
in the shell of the sea-urchin or
the arm of a star-fish, through
which the foot-tubes or ambu-
lacral feet are protruded.
A-ME-TA'BO-LIC (Gr. a, without ;
metabole, change). Referring
to insects and other animals
which do not undergo a meta-
morphosis.
A-MOR'PHOUS (Gr. a, without;
morphe, form). Without a defi-
nite figure ; shapeless ; espe-
cially applicable to sponges.
AM-PHI-CCE'LOUS (Gr. amphi;
koilos, hollow). Applied to
vertebrae which are doubly
concave, or hollow at both
ends.
A-NAL'O-GY (Gr. analogia, propor-
tion). The relation between
organs which differ in struc-
ture, but have a similar func-
tion; as the wings of insects
and birds.
A-NAS-TO-MO'SING. Inosculating
or running into each other like
veins.
AN-CHY-LO'SIS. The growing to-
gether of two bones so as to
prevent motion between them.
AN'NU-LATE. When a k'g or an-
tenna is surrounded by narrow
rings of a different color.
A'PLA-CEN-TAL. Referring to
those mammals in which the
embryos are destitute of a pla-
centa.
A'po-Dorjs. Footless.
AP'TE-ROUS (Gr. a, without \pter-
on, wing). Destitute of wings.
A-QUI'FE Rorjs(Lat. aqua, water;
fero, I carry). Applied to the
water-carrying or water-vascu-
lar system of the sponges, etc.
A-RACH'NI-DA (Gr. arachne, a spi-
der). The class of Arthropods,
690
GLOSSARY.
embracing the spiders, scor-
pions, aud mites.
A'RE-O-LATE. Furnished with
small areas; like a network.
A-RIS'TATE. Furnished with a
hair.
AR-THRO'PO-DA (Gr. artTiros, a
joint; pans, podos, foot). Those
Articulata with jointed feet,
such as crabs, bees, etc.
AR-TI-CU-LA'TA (L&t.articulus, di-
minutive of artus, a joint).
Cuvier'ssubkiugdom of worms,
Crustacea, and insects.
AR-TI-O-DAC'TY-LA (Gr. artios,
even; daktulos, finger or toe).
Those Ungulates with an even
number of toes, as the ox.
A-SEX'U-AL. Applied to animals,
especially insects, in which the
ovaries or reproductive organs
are imperfectly developed ; aud
which produce eggs or young
by budding.
AU-RE'LI-A. Old term for the
pupa of an insect.
AU'RI-CLE (Lut. auricula, a little
ear). One of the cavities of
the heart of mollusks and verte-
brates.
AZ'Y-GOS (a, without ; zugon, a
yoke, a pair). An organ, such
as a nerve or artery, situated
in the middle line of a bilater-
ally symmetrical animal, which
has therefore no fellow.
B/E-NO'PO-DA (Gr. baino, to walk).
The thoracic legs of insects.
B^E'NO-SOME (Gr. baino, to walk;
soma, body). The thorax of in-
sects.
BI'FID. Divided into two parts;
forked.
BLAS'TO-DERM (blastos, a bud or
sprout ; derma, skin). The outer
layer of the germ-cells of the
embryo.
BLAS TO-PORE. The mouth of
the gastrula.
BLAS TO- SPHERE. The embryo
when consisting of a single
cell-layer.
BRAN CHI- A. A gill or respiratory
organ of aquatic animals.
BRAN 'CHI- AL. Relating to the
gills or branchiae.
BUC'CAL. Relating to the mouth
cavity; or rarely to the cheeks.
BUL'LATE. Blistered.
CA-DU-CI-BRAN'CHI-ATE (Lat. ca-
ducus, falling off; Gr.bragchia,
gills). Applied to those Ba-
tracJiia in which the gills be-
come absorbed before adult life.
CAL'CA-RA-TED. Armed with
spurs.
CA'LYX. A little cup; often ap-
lied to the body of a Criuoid.
CAP'I-TATE. Ending in a head or
knob.
CEN-TRUM. The body or central
part of a vertebra.
CE-PHAL'IC. Relating to the
cephalum or head.
CE-PHAL'O-MERE. A cephalic seg-
ment of an Arthropod.
CE-PHAL'O-SOME. The head of in-
sects, Arachnida and Myrio-
poda.
CER-CO'PO-DA (Gr. cercos, tail;
pous, podos, foot). The last pair
of jointed abdominal appen-
dages of insects; the "cerci."
CHE'LA. The terminal portion of
a limb with a movable lateral
part, like the claw of a crab ; as
GLOSSARY.
691
in the chelate maxilla of the
scorpion.
CHI-AS'MA (Gr. chiasma, a cross-
ing). The commissure of the
optic nerves in most verte-
brates.
CHI'TIN (Gr. chiton, a tunic). The
horny substance in the skin of
insects, etc.
CHYLE (Gr. cJiulos, juice). The
milky fluid resulting from the
action of the digestive fluids on
the food or chyme.
CHYME (Gr. churnos, juice). The
acid, partly fluid or partly
digested food, produced by
the action of the gastric juice
on the food.
CIL'I TJM (pi. cilia). Microscopic
filaments attached to cells,
usually within the body, and
moving usually rhythmical-
iy.
CIR'RUS. A slender process on
the body of worms.
CLO'A-CA (Lat. a sewer). The
common duct or passage at the
end of the intestine into which
the oviducts and urinary ducts
open, as in reptiles, birds, and
monotreme mammals.
C<E'CAL. Ending blindly or in a
cul-de-sac.
COZ'CUM. A blind sac; usually
applied to one or more append-
ages of the digestive canal.
CCE-NEN'CHY-MA (Gr. komos, com-
mon; chum os, chyme or juice).
Applied in polyps to the coral
mass containing the chymifer-
ous or nutritive canals connect-
ing the different polyps.
COL'LO-PHORE. The sucker-like
organ extended from the under
side of the abdomen of Podu-
rans.
COM-MIS'SURE. The nerves con-
necting two ganglia.
CON-COL'O ROUS. Of the same
color as another part.
CON'DYLE (Gr. kondulos, a
knuckle). The articular sur-
face of a bone, especially of
the occiput.
COR'TI CAL. Relating to the cor-
tex or inner skin; external, as
opposed to medullary.
COS'TAZ, (Lat. costa, a rib). Re-
lating to the ribs.
CRIB'RI FORM (Lat. cribrum, a
sieve ; forma, form). With
perforations like those of a
sieve.
CROP. A partial dilatation of
the gullet or oesophagus, the
ingluvies ; in many insects the
fore stomach or proventricu-
lus.
CU'TI-CLE. The outermost layer
of the integument.
DE-CID'C-OUS. Relating to parts
which fall off or are shed dur-
ing life, as the gills of the
frog, etc.
DEN'TATE. Furnished with
teeth.
DERM'A-TOP-TE-RA (Gr. derma,
skin; pteron, wing). The ear-
wigs.
OM'A-LUE. The third pair
of head appendages of Myri-
opoda.
DI-DEL'PHI-A (Gr. din, two, or
double; delphus, womb). The
sub-class of Marsupials.
DTK FKU EN-TI-A'TION. The spec-
ialization or setting apart of
692
GLOSSARY.
special organs for special work,
as the specialization of the
hand of man from the fore-
foot of other mammals ; also
applied to the special develop-
ment during embryonic life of
parts adapted for peculiar or
special functions.
DIG'IT. A finger or toe.
DI-MID'I-ATE. Half round.
DI-<E'CI-OUS. (Gr. dis, two;
oikos, house). With distinct
sexes.
DIP'TE-RA (Gr. dis, two; pteron,
wing). Two-winged flies ; an
order of insects.
DI-VER-TIC'U-LUM. An offshoot
from a vessel or from the ali-
mentary canal.
DUCT. A tube or passage usu-
ally leading from glands.
EC-DY'SIS (Gr. ekdusis, casting
off). The process of casting the
skin ; moulting.
E-CIIIN-O-DER'MA-TA (Gr. echinos,
a hedgehog or urchin ; hence
applied to the sea-urchin ; and
derma, skin). The fourth sub-
kingdom of animals.
E-LAS-MO-BRAN'CIII-I (Gr. elasma,
a strap; bragchia, gill). The
sharks and rays.
E-LA'TER. The spring or forked
"tail" of Podurans.
E-LY'TRA (Gr. elutron, a sheath).
The fore-wings of heetles,
serving to cover or sheathe the
hind wings.
EM'BRY-O. The germ or young
animal before leaving the egg
or body of the parent.
ENDO-BLAST. The primitive,
embryonic eudoderm.
EN'TE-RON (Gr. enteron). A gen-
eral term applied to the diges-
tive canal as a whole.
E-PHEM'E-RI-NA. The order of
net-veined insects represented
by Ephemera.
E'-Pi-BLAST. The ectoderm in
its embryo state. The ecto-
blast.
E-PIB'O LE. Where the gastrula
is formed by a spreading of a
thin layer of epiblast cells
over the much larger hypoblast
cells.
E-PIS'TO-MA. That part of the
face of flies situated between
the front and the labrum.
E QUI-LAT'E-RAL. Having the
sides equal, as iii Brachiopod
shells.
E'QUI-VALVE. Applied' to shells
like the clams and most La-
mellibranchs, which are com-
posed of two equal pieces or
valves.
EX-SER'TED. Protruded; opposed
to enclosed.
EX-TJ'VI-UM. Cast-off skin.
FIS-SIP'A-ROUS (Lat. fissus, cleft ;
pario, to bring forth). Ap-
plied to a form of asexual gen-
eration where the parent splits
into two parts, each part be-
coming a new individual.
FCE'TUS. The embryo of a
mammal.
GANG'LI-ON (Gr.gaffglion, a swell-
ing or lump). A centre of
the nervous system, consisting
of nerve-cells and fibres.
GEM-MIP'A-ROUS (gemma, bud ;
pario, to bring forth). Ap-
GLOSSARY.
693
plied to a form of asexual gen-
eration where new individuals
arise as buds from the body of
the parent.
GLA'BROUS. Smooth ; opposed
to hairy; downy, villous.
GLAND. A cellular sac which
secretes, i.e. separates, certain
constituents of the blood. The
liver is a gland secreting bile ;
the kidneys excrete urine,
GLATJ'COUS. Bluish green or gray.
GON-OP'O-DA (Gr. gone, genera-
tion; pous, podos, foot). The
modified first pair of abdomi-
nal appendages of the male lob-
ster, shrimps, and crabs.
(Gr. liaima, blood).
Connected with the blood-ves-
sels or heart.
HAL/LUX. The thumb or great toe.
HAL'TER-ES (Gr. halteres, poisers).
Balancers : the rudimentary
hind wings of Diptera.
HAUS'TEL-LATE. Furnished with
a proboscis so as to take food
by suction.
HE-MIP'TE-RA (Gr. hemi, half ;
pteron, wing). An order of in-
sects with the fore-wings part-
ly opaque, hence called heme-
lytra.
HER MAPH RO-DITE (Gr. Hermes,
Mercury ; Aphrodite, Venus).
Any animal having the organs
of both sexes, usually the
ovary and testes, combined in
the same individual.
HE-TE-RO-CER CAL. Unevenly
lobed, as in the tail of sharks
and Ganoids, when the back-
bone is prolonged into the up-
per lobe.
HET-E-ROG'A-MY.= Parthenogen-
esis.
HEX-A'PO-DOUS. Provided with
six feet.
Ho MO-CER'CAL. Even-lobed, as
in the tails of bony fishes.
HO-MOL'O-GY (Gr. homoloyia,
agreement). Implies identity
in structure between organs
which may have different uses ;
as the fin of a whale, and the
foot of a dog, or a bird's wing.
Homology implies blood-rela-
tionship, i.e., a community of
origin between parts which
may have distinct uses.
HY'DA TID. The bladder-worm,
or the cystic stage of a tape-
worm.
HY-MEN-OP'TE-RA (Gr. humen,
hymen, or membrane; pteron,
wing). An order of insects
with two pairs of membranous
wings.
HY'OID (Gr. T, eidos, resem-
blance). A bone in man named
from resembling the letter U ;
its form being different in
other vertebrates : also called
os linguae, from its supporting
the tongue.
HY PO BLAST. The under or in-
ner layer of the embryo. =
ectoblast, and the eudoderm of
the adult.
IM'A-GO. The final or fourth,
winged and adult state of in-
sects.
IN-E-QUI-LAT'E-RAL. Having the
two ends unequal, as in the
clam, qiiohog, and most La-
mellibranch shells.
IN-E'QUI-VALVE. With one valve
694
GLOSSARY.
differing in size or shape from
the other, as iu the oyster or
Brachiopod shells.
IR'RO-RA-TED. Freckled ; sprin-
kled with atoms.
LAMB-DOI'DAL. Referring to the
lambdoidal or V-shaped suture,
with the apex upward, in a
mammal's skull.
LAM-EL-LI-BRAN'CHI A-TA (Lat.
lamella, a leaf or sheet ; bran-
cilia, gill). A class of mollusks
with large leaf-like gills.
LAR'VA (Lat. larva, a mask).
The second stage of the insect,
a caterpillar, grub, or mag-
got.
LUM'BAR (Lat. lutnbus, a loin).
Connected with the loins.
LTJ'MEN. The cavity of an organ.
MA-LI'PE-DES. The fourth and
fifth pairs of head-appendages
of chilopod Myriopods.
ME-DUL'LA (marrow). The spinal
cord of vertebrates.
MEN'TUM (chin). The basal
piece or sclerite of the labium
or second maxillae of insects.
Submentum is the posterior
division of the meiitum.
MES-EN'TE-RON. The mid-gut or
stomach.
MES'EN-TE-RY (Gr. mesos, inter-
mediate ; enteron, intestine).
The membrane between the in-
testine and abdominal walls.
ME SO-BLAST. The primitive,
embryonic mesoderm.
ME-TAG'E-NE-SIS. Alternation of
generations.
ME'TA-MERE. The same as som-
ite or arthromere.
MON-(E'CI-OTJS (Gr. monos, single:
oikos, house). With the sexual
glands, etc., united in the same
individual.
MY'O-BLAST. The embryonic
cells which become muscle
cells.
MYR-I-OP'O-DA (Gr. murios, thou-
sand ; pous, podos, foot). The
class of tracheates comprising
the Millipedes and Centipedes.
NE-MAT'O-CYST (Gr. nema, a
thread ; kustis, a bladder).
The nettling, stinging organs
or thread-cells or lasso-cells of
the jelly-fishes and polyps,
etc.
NE-PHRID'I-A (Gr. nephros, kid-
ney). The segmeutal organs
of worms, etc.
NEU-ROP'TE-RA (Gr. neuron,
nerve; pteron, wing). The
order of net-veined insects with
a complete metamorphosis.
NID-A-MEN'TAL. Referring to a
nest, or egg-sac.
NO'TO CORD (Gr. noton, back ;
chorde, a string), or chorda
dorsalis. The primitive sup-
port of the body of vertebrate
embryos, larval ascidians, and
the backbone of the lancelet
and lampreys.
OB'TEC-TED. Covered ; con-
cealed.
O'DO-NA-TA (Gr. odous, teeth).
The dragon flies.
O-DON'TO-PHORE (?Gr. odous, a
tooth ; phero, I carry). The
so-called tongue or lingual
ribbon of the higher mol-
lusks.
GLOSSARY.
G95
(E-SOPH'A-GUS (Gr. oisos, a reed ;
phagein, to e;it). Tlie gullet.
Ox-TOG'E-NY(Gr. on, ontos, beiug;
gene, birth). The development
from the egg, of an individual
animal.
O-PER'CU-LUM (Lat. operio, to
cover). In fishes one or more
bones covering the gills ; in
Gastropod mollusks a horny
plate or solid limestone mass
closing the orifice of shells.
O-PIS-THO-CCE'LOUS (Gr. opisthen,
behind ; koilos, hollow). Those
vertebrates with bodies hollow
behind and convex in front.
O'RAL. Related to the mouth.
OR-NI TIIO-DEL'PH I-A (Gr. or nix,
bird ; delphus, womb). The
sub class of mammals and or
der Monotremata.
OR-THOP'TE-RA (Gr. orthos,
straight ; pteron, wing). The
order of insects with straight
narrow fore-wings, as the grass-
hoppers.
OS-TRA'CO-DA (Gr. ostracodes,
shelled). A group of shelled
Crustacea.
O'TO-LITHS (Gr. mis, ear ; lithos,
stone). Small bones suspended
in the internal ear of fishes, or
concretions in the auditory
sacs of invertebrates.
O-VIP'A-ROUS (Lat. ovum, an egg;
pario, I bring forth). Applied
to animals bringing forth eggs
instead of living, active young.
O-VI-POS'I-TOR (Lat. orutn, an
egg; pono, I place). An organ
in insects homologous with the
sting, by which eggs are de-
posited in solid substances.
O'VI-SAC. A sac or bag-like mem-
brane attached to the parent,
and containing eggs.
O-VO-VI-VIP'A-ROUS (Lat. ovum,
an egg; rin/x, alive; pario, 1
bring forth). Applied to such
animals as retain their eggs m
the body until they are hatched.
DO-GEN'E-SIS. Parthenoge-
nous development in larval in-
sects.
PAL'LI-UM (Lat. a cloak). The
mantle or body-wall of mol-
lusks, which secretes the shell ;
adj. pallial.
PA-PIL'LA. A minute soft projec-
tion.
PA-REN'CHY-MA (Gr. paregchuma,
from para, en, chiio, something
poured in besides). Applied
to the proper substance of vis-
cera, excluding connective tis-
sue, blood-vessels, and other
accessory parts.
PAR-THE NO GEN'E-SIS (Gr. par-
thenos, virgin; yenesis, genera-
tion). Reproduction by direct
growth of germs from the egg,
without fertilization by male
germs or spermatozoa, as in the
aphis, gall-insects, lluke-worm,
etc.
PEL'A-GIC. Living on the high
seas, away from the coast; in
mid-ocean.
PER'I-SOME (Gr. peri, around;
soma, body). In Crinoids the
oral region of the cup or body.
PE -REN-NI-BKAN < I! I- A TA (Lat.
perennis, perennial: branchiit.
gill). Those Batrachia whicli re-
tain their gills throughout, life.
PER-IS-SO-DAC'TY-LA (Gr. perissos,
uneven; dnktulos, finger).
696
GLOSSARY.
Those Ungulates with an un-
even number of toes, as the
horse.
PE-RI-TO-NE'UM (Gr.peri, around;
teino, I stretch). The mem-
brane lining the abdominal
walls and covering the enclosed
viscera.
PER-I-VIS'CE-RAL (Gr. peri,
around; Lat. riscera, the inter-
nal organs, especially of the
abdominal cavity). The body-
cavity containing the alimen-
tary canal with its outgrowths.
PHA-RYN'GE-AL. Relating to the
pharynx.
PHY-LOG'E-NY (Gr. phulon, stem;
gene, birth). The development
by evolution of the members of
a genus, family, order, class, or
the animal kingdom as a whole.
PI'CE-OUS. Pitchy; the color of
pitch; shining reddish black.
PI'LOSE. Clothed with pile, or
dense short down.
PLAN'U-LA. The two - layered
embryo of Coeleuterates.
PLA-TYP'TE-RA (Gr. plains, flat ;
pterori). The order of insects
represented by the white ants,
Psocida? and Perlidse.
PLEX'US (Lat. a knot). Applied
to a knot-like mass of nerves
or blood-vessels.
POL-LEX. The thumb or inner-
most digit of the hand or fore-
foot.
POL'Y-PIDE or POL'Y-PITE. The
separate animals of a Hydro-
zoon.
PRE'O-RAL. In front of the
mouth.
PROC'ESS. A projection; used
chiefly in osteology.
PRO-CCE'LOUS (Gr. pro, front;
koilos, hollow). Those verte-
brae concave or hollow in front.
PROC-TO-D^E'UM. The primitive
hind gut, or rectum.
PRO-TOM'A-L^:. The second pair
of head-appendages in Myrio-
poda.
PRO'TOPLASM (Gr. protos, first;
pUisma, from plasso, I mould).
The albuminous, elementary
matter forming cells and the
body-substance of Protozoa.
PROX'I-MAL (Latproximus, next).
The fixed end of a limb, bone,
or appendage; that nearest the
body; opposed to distal, the
farther end.
PSEU-DO-PO DI-A (Gr. pseudes,
false; podes, feet). The tem-
porary processes sent out from
the bodies of Protozoa.
PTER-OP'O-DA (Gr. pteron, wing;
pous,podos, foot). A class of
pelagic mollusks.
PU-BES'CENT. Coated with very
fine hairs.
PUNC'TURED. Marked with nu-
merous small impressed dots.
PTJ'PA (Lat. a doll). The third
or usually quiescent, chrysalis
stage of insects.
PY-LO'RTJS. The valve between
the stomach and intestine.
RAT'I-T<£ (Lat. rath, a raft). A
division of birds with a keel-
less, raft- or punt-like sternum.
RHAB'DI-TES. The blade-like ele-
ments of the sting and oviposi-
tor of insects.
RHI-ZO'PO DA (Gr. risa, root;
pous, podos, foot). The root-
footed Protozoa.
GLOSSARY.
697
RO-TIP'E-RA (Lat. rota, & wheel;
fero, I bear). A class of worms
with a pair of ciliated vela
which iii motion resemble
wheels.
SA-GIT'TAL. Referring to a line
or plane parallel with the
sagittal or median suture of
the skull of higher vertebrates.
SAR'CODE (Gr. ,<tar.r, flesh; odos,
way). Equivalent and earlier
term for protoplasm.
SCA'BUOUS. Rough like a file,
with small raised dots.
SCLE'RITE. Any separate piece
of au insect's integument.
SCUTE. Applied to the dorsal
pieces in Myriopods.
SEP'TUM. A partition.
SO-MAT'IC. Relating to the body.
SOM'ITE. A segment of a seg-
mented animal, such as a
worm.
SE-TA'CE-OUS (Lat. seta, a bristle).
Bristle-like.
SPI'RA-CLE (Lat. spiro, to breathe).
The lateral breathing pores of
insects.
STIG'MA-TA (Gr. stigma, a mark).
A synonym of spiracle.
STO'LON (L&t.stolo, a shoot spring-
ing from the root of a plant).
Applied to the root-like creep-
ing growths of polyps and
other Coeleuterates.
STO-MO D^E'UM. The primitive
mouth and resophagus of the
embryo of worms and Ar-
thropoda.
STREP SIP'TE-RA (Gr. strephis, a
twist; pteron, wing). A group
of beetles, whose minute front
wings appear as if twisted.
STRO'BI-LA (Gr. strobilos, a fir
cone). The chain of zooids of
a larval medusa; the chain of
proglottides of a tape-worm.
SUC-TO'RI-AT.,. Adapted for suck-
ing.
SU-PRA-OR'BI-TAL. Above the or-
bits.
SU'TURE. A seam or impressed
line between the bones of the
skull or parts of the crust of au
Arthropod.
SYM'PHY-SIS (Gr. sumphmis, a
growing together). The union
of two bones.
TAC'TILE. Relating to the sense
of touch.
T^-NID'I-UM. The band or chili-
nous fibre, forming the so-
called "spiral thread" of the
tracheae of insects.
TEL'SON (Gr. tehon, from telos,
end). The rudimentary ter-
minal segment of the abdomen
of Arthropods.
TEN'E-RAL. A state of the Neu-
ropterous imago after exclu-
sion from the pupa, in which
it has not fully completed its
coloring, clothing, etc.
TEN-TAC'U-LUM (Lat. tento, I
touch). A feeler or tentacle.
TER'GTJM (Lat. back). The dorsal
region of Arthropods.
TEST (Lat. testa, a shell). The
thickened integument of Tuni-
cata.
TES-TA'CEOUS. Dull red; brick
color.
THO'RAX (Gr. thorax, a breast-
plate). The chest in verte-
brates; the middle body in in-
sects and some Crustacea.
608
GLOSSARY
THY-SAN-U'RA (Gr. thusanoi,
fringes; oura, tail). The low-
est order of insects.
To MEN-TOSE'. Covered with fine
matted hairs.
TRA-BEC'U-L/E (crauii), dim. of
trabs, a beam. Applied to the
longitudinal cartilaginous bars
of the fore-part of the head of
vertebrate embryos.
TRA'CHE-A (Gr. tracheia, the
rough windpipe). The respira-
tory tube in vertebrates; the
air-tube of tracheate insects.
TREM-A-TO'DA (Gr. trema, a pore
or hole). An order of worms.
TRUN CA'TED. Cut squarely off;
docked.
TU-BER CU-LOSE. Covered with
tubercles.
TuN-i-CA'TA(Lat. tunica, a cloak).
The class of worms called As-
cidians.
UM'BO (Lat. the boss of a shield).
The beak of a Lamellibranchi-
ate shell.
UN-GTJ-LA'TA (Lat.ungula, a hoof).
The order of hoofed mammals.
U-RO-DE'LA (Gr. oura, tail; delos,
visible). The tailed Batrachi-
aus.
U-RO-MERE' (Gr. ouros,lA\\ ; meros,
a part). Any of the abdominal
segments of an Arthropod.
U-ROP'O-DA (Gr. ouros; pous, po-
dos, foot). Any of the abdom-
inal feet of Arthropoda.
U-RO-SOME' (Gr. ouros, tail ; meros,
a part). The abdomen of Ar-
thropods.
U-RO-STERN'ITE. The sternal or
under piece of the uromeres or
abdominal segments of insects.
VAC-U-OLE' (Lat. vacuus, empty).
The little cavities in the bodies
of Protozoa.
VEIN. Applied to the ribs or
" nervures" of the wings of in-
sects; the branches of the veins
are called venules.
VEN'TRAL. Applied to the under
sitie of the abdomen, or of the
bod}' of invertebrates.
VEN'TRI CLE (Lat, ventriculus, di-
minutive of venter, belly)- One
of the cavities of the heart.
VER-RIC'U-LATE. With thick set
tufts of parallel hairs.
VER'RU-COSE. Covered with wart-
like prominences.
VER'TE-BRA (Lat. verto, I turn).
One of the bones of the spinal
column or backbone.
VER-TI-CIL'LATE. Placed in
whirls.
VES'I-CLE (Lat. vesica, a blad-
der). A little sac, bladder, or
cyst.
VIS'CE-RA (Lat. viscus). The in-
ternal organs of the body.
VI-VIP'A-ROUS (Lat. virus, alive;
and pario, I bring forth). Ap-
plied to animals which bring
forth their young alive.
ZO'OID (Gr. soon, animal ; eidos,
form). The highly specialized
organs of such animals as the
Hydroids, and other compound
forms which have a marked in-
dividuality, and which might
be mistaken for genuine indi-
viduals.
ZO-O'PHYTE (Gr. zoon, animal;
phuton, plant). Applied to the
plant-like polyps, sertularians,
and sponges.
INDEX.
ACANTHARCHTJS POMOTIS, 443
Acantbocephali, 123, 133
Acanthoglossus Bruijnii, 573
Acarina, 339, 366
Achorutes nivicola, 344
Acineta, 34
Acipenser sturio, 427
development of, 427
Acrania, 401, 405
Adheres Carpenter!, 278
Actinia, 74, 78
Actinophrys sol, 27
Actinosphserium, 26
Actinozoa, 74, 91
Adaptation of animals to their
surroundings, 10
Adder, puff, 499
jEgineta, 62
JEoYis pilata, 245
^Epyornis, 538
Agalmopsis, 70
Agamogenesis, 54
Agelacriuus, 190
Ai, 579
Aix sponsa, 543
Albatross. 542
Albertia, 137
Alca impennis, 541
Alcyonaria, 85, 91
Alectorides, 544
Aletia, 359
Alewife, 450, 451
Alligator Mississippiensis, 514
Alopecias vulpes, 420
Alosa sapidissima, 450
Alpheus, 305
Alytes obstetricans, 484
Amaroecium, 390
Ambergris, 593
Amblyopsis spelanis, 433
Amblyrbyncbus, 504
Amblystoma mavortium, 479
Amia calva, 433
Amiurus lynx, 443
Ammocoetes, 410
Ammonites, 280
Amoeba, 3, 17, 22
Ampelis cedrorum, 555
Ampbibia, 464
Amphioxus, structure of, 406
development of, 407
Amphipoda, 285
Ampbisbaena, 502, 503
Ampbitrite cirrata, 173
ornata,
Ampullae of Echinoderms, 179
Anabas scandens, 457
Anadromous fishes, 451
Analogy, 12
Anas boschas, 543
obscura, 543
Anchitberium, 602
Ancistrodon contortrix, 500
piscivorus, 500
Andrena, 364
Andrias Scheuchzeri, 479
700
INDEX.
Anemone, sea, 74
Angle, facial, 626
Angler, 442, 460
Anguilla acutirostris, 446
Anguillula aceti, 128
tritici, 128
Animalcule, bear, 341
Animalcules, bell, 39
infusorian, 31
root, 22
trumpet, 35
Animal kingdom, classification
of, 15
Animals, development of, 643
distinguished from plants,
1
high and low, 6
Annelides, 167, 176
Anuulata, characters of, 163
classification of, 176
Anochauus sinensis, 203
Anodonta, 225
Anolis, 503
Anomodontia, 512
Anopla, 157
Anoplodium Schneideri, 103
Ant, 361
Ant-eater, spiny, 573
Ant, white, 347
Antedon rosaceus, 187
Antelope, prong-horn, 609
Anthracaridse, 272
Anthrapalsemon, 272, 294
Anthropoidea, 618, 619
Antilocapra Americana, 609
Antipathes arborea, 85
Anura, 463, 468
Apes, 621
Aphis, 350
lion, 349
Apis niellifica, 365
Aploceros montauus, 610
Apodes, 446
Appendicularia, 389
Apteryx, 538
Aptornis, 538
Apus sequalis, 282
Arachnactis, 79
Arachnida, characters of, 338, 366
development of, 342
Araneina, 342, 366
Arcella, 24
Archseopteryx inacrura, 537
Archaster, 196
Archegosaurus, 482
Architeuthis monachus, 262
princeps, 262
Arciferous Anura, 484
Arcturus Baffini, 290
Argonauta, 263
Argulus alosse, 279
Armadillo, 580
Army worm, 359
Artemia fertilis, 284
Arthrogastra, 342
Arthromere, 266
Arthropoda, characters of, 265
Artiodactyla, 600, 605
Ascaris den tat a, 122
lurnbricoides, 125
mystax, 125
nigroveuosa, 122
Ascetta primordialis. 42
Ascidia callosa, 392
gigas, 392
Ascidiacea, 387, 405
Ascidians, 386
Asellus, 288, 290
Asexual generation, 653
Asiphonia, 256
Asp, 499
Aspergilluni, 250
Aspidogaster couchicola, 110
Aspidonectes spiuifer, 510
Aspredo, 449
Asterias vulgaris, 178, 191, 197
Asteridea, 193, 198
Asteroidea, 191, 198
INDEX.
701
Astrsea pallida, 81
Astrangia, 80
Astrangia Dante, 81
Astrogouium, 196
Astroides, development of, 82
Astropecteu, 196
Astropbytou Agassizii, 193
Atalapha uoveboracensis, 591
Ateles, 560, 620
Atlantosaurus, 515
Atoll, 89
Atrium, 388
Auk, great, 541
Aurelia aurita, 63
flavidula, 65
Auricularia, 214
Aurochs, 612
Autechinida, 205, 208
Autolycus, 173
Automata, animals as, 682
Aves, anatomy of, 518, 525
characters of, 518, 557
development of, 532
feathers of, 523
moulting of, 534
nesting habits of, 536
sexual colors of, 535
skeleton of, 518, 519, 521
songs of, 535
topography of, 520
Axinella polypoides, 48
Axolotl, 479
Aye-aye, 619
BABOOIT, 620
Balsena mysticetus, 592
Balseniceps rex, 545
Balaenoptera boops, 592
Balanoglossus aurantiacus, 157
Balanus hnlanoides, 273
Balatro, 137
Baphetes, 483
Barnacle, 272
anatomy of, 273
Barramundi fish, 430
Bathycrinus, 183
Bats, 588
Batrachia, breeding habits of, 484
characters of, 464, 487
development of, 476
gills of, 468
poison of, 475
reproduction of lost parts
of, 481
skeleton of, 465
teeth of, 467
viviparous, 479
Bear, 615
Beaver, 584
Bee, 359, 365
Beetles, 372
oil, 372
Belone longirostris, 454
Bilateral symmetry of Ctenopho-
ra, 92, 93
Echinoderms, 178, 202
Bilharzia haematobia, 110
Bill-fish, 454
Bimana, 624
Bipaliuni dendrophilus, 101
Bipinnaria, 195
Birds, diving, 541
of prey, 548
perching, 551
raptorial, 548
swimming, 543
(Also see Aves.)
Bison, 611
Bladder, swimming, of fishes, 442
Blastoidea, 189, 191
Blind fish, 442, 444, 453
shrimps, 315
Blissus leucopterus, 349
Blister beetles, 353
Blood, circulation of, 635
Blood corpuscles, 8
Blue-fish, 455
Boa constrictor, 496
702
INDEX.
Bolina alata, 92, 93
Boltenia reniformis, anatomy of,
389
Bonellia viridis, 162
Bootherium, 610
Bopyrus palaemoneticola, 288
Bos longifrons, 612
primigenius, 612
taurus, 613
Bot fly, 355
Botbriocepbalus latus, 117
Box-fish, 462
Bracbiata, 183, 191
Bracbiolaria, 195
Bracbiouus, development of, 136
Bracbiopoda, development of,
150
structure of, 146, 150, 153
Bracbyura, 294
Bradypus tridactylus, 579
Brain coral, 80
Branch inectes Coloradeusis, 283
Brancbioganoidei, 431
Brancbiopoda, 279, 305
Brancbipus, 283
Branta Canadensis, 544
leucopsis, 544
Bream, 455
Brisinga, 196
Bristle-tails, 344
Bmta, 577, 629
Bryozoa, 138
Bubo Virginiauus, 549
Buccinum undatum, 248
Bucephalus cuculus, 108
Budding in Ascidiaus. 392, 402
Hydroids, 54
Infusoria, 37
Medusa, 60
Polyps, 77, 82
Starfish, 192
Bufo ictericus, 475
lentiginosus, 485
Bugs, 350
Bustard, 546
Butcher bird, 555
Butterfly, 357
Buzzard, turkey, 548
CACHELOT, 593
Caddis-fly, 348
Caiman, 515
Cayman, 515
Calamoichtbys, 431
Calcispongiae, 46, 49
Caligus curl us 279
Callignathus shmis, 594
Callorbynchus, 424
Caloptenus spretus, 308
femur-rubrum, 308
Calyptraea sinensis, 243
striata, 243
Camarasaurus, 515
Cambarus pellucidus, 295
Camel, 614
Camelus, 614
Campanularise, 61
Campodea, 344
Americana, 345
Cookei, 345
Cancer irroratus, 293
Canis caribseus, 617
domesticus, 617
extrarius, 617
familiaris, 616
latrans, 617
leporarius, 617
molossus, 617
sagax, 617
vertagus, 617
Cantbocamptus cavernarum, 277
Capelin, 452
Capybara, 586
Carcbarias gangeticus, 421
Cardium pygmaeum, develop-
ment of, 233
Cariacus Virginianus, 609
Caribou, 609
INDEX.
703
Carinata?, 541, 557
Carneospongeae, 47, 49
Carnivora, 614, 629
Carp, 453
Caryocystites, 190
Cavyopbyllaeus, 119, 120
Cassowaries, 539
Catarrhinae, 620
Cat, anatomy of, 564
civet, 617
domestic, 617
Cat-fish, 443
Cateuula lemnse, 102
quaterna, 102
Cathartes atratus, 548
aura, 548
Cattle tick, 341
Caudina arenata, 216
Cavolina tridentata, 238
Cebus, 620
Cecidomyia, 357
Cells, 5
Centipede, 338
Cephalaspis Lyellii, 427
Cephalization, 289, 314, 405
Cephalophora, characters of, 237
classification of, 252
Cephalopoda, characters of, 252
classification of, 263
development of, 258
Cephalopterus diabolus, 424
Cephalula, 135
of worms, 171, 172
Ceratodus Fosteri, 429
Cercaria cystophora, 108
ecbinata, 108
Cercaria, history of, 105
Cercoleptes, 615
Cercopithecidse, 620
Cerianthus borealis, 79
Cermatia forceps, 338
Cervus Canadeusis, 609
Cestodes, structure of, 111, 121
Cestracion, 416
Cetacea, 591, 629
Cete, 591, 629
Cetiosaurus, 515
Cboetoderma nitidulum, 162
C'ha'tognutlii, 132, 133
Chsetopoda, 174
Chaetosoma, 128
Chalinula oculata, 48
Chameleon, 503
Charybdaea, 62
Cheiromys, 619
Chelifer, 342
Chelouia, anatomy of, 505
characters of, 504, 517
Chelydra serpentina, 510
Chick, development of, 646
Chilichtbys turgidus, 462
Chiloguatha, 356, 385
Chilomycterus geometricus, 462
Chilopoda, 338, 366
Chimaera, 425
plumbea, 425
Chimpanzee, 622
Chinch-bug, 349
Chirodota laeve, 216
Chiroptera, 588, 629
Cbirotes, 502
Chiton, nervous system of, 248
Chiton ruber, 248
Chondroganoidei, 427
Chorda dorsalis of Ascidians, 396
Chordeiles Virginiauus, 551
Chrysemys picta, anatomy of, 506
Chrysothrix, 620
Chub, 453
Chub sucker, 443
Chyle of polyps, 77
Chyme of polyps, 75
Cicada, seven teen -year, 350
Cidaris nutrix, 204
Ciliary motion, 142
Ciliata, 35, 40
Cinclides, 75
Cinura, 345
704
INDEX.
Cirratulus grandis, 226
Cirripedia, 272, 3U5
Cistenides Gouldii, 174
Cladocera, 279
Cladodactyla crocea, 215
Clam, anatomy of, 222
Clamatores, 552
Classification, 13
Clepsine, embryology of, 166
Clidiophora trilineata, 230
Climbing fish, 457
Clioua sulphurea, 49
Clione papillouacea, 239
Clupea harengus, 450
Clymenella torquata, 174
Clypeaster, 205
Coati, 615
Cocbineal insect, 350
Cod, 458
Codosiga pulcherrimus, 32
Ccecilia, 482
Ccelenterata, 51
Ccenosarc of coral polyps, 85
Coleoptera, 352, 346
Collembola, 344
Collosphrera spiuosa, 27
Colobus, 621
Coloration, protective, 675
of snakes, 497
Colossocbelys, 511
Commensals, 68, 459
Comparative anatomy, 631
Complementary males, 273
Compsemys, 511
Compsognatbus, 516
Condor, 548
Condylura cristata, 587
Conger oceanicus, 446
young of, 446
Conjugation in Infusoria, 39
Conurus Carolinensis, 550
Copperhead snake, 500
Corals, deep-sea, 84
development of, 83
Coral, fishery, 85
polyps, 74
rate of growth of, 84
reefs, formation of, 86, 88
tabulate, 58
Corallium rubrum. 85
Cordylophora lacustris, 57
Coreus tristis. 350
Cormus, 181
Coryne mirabilis, 59
Coryphoena, 455
Coryphodon, 571, 601
Cotton worm, 379
Cowry money, 249
Crane fly, 357
Cranes, 544
Craniota, 385
Craspeda of polyps, 75
Craw-fish, 3%
Cribellasauguinoleuta, 197
Criuoidea, 183, 190
development of, 187
Crocodilia, 514, 517
Crocodilus acutus, 514
Crossaster papposus, 197
Crow, carrion, 548
Crustacea, classification of, 272,
305
structure of, 266
Cryptobranchus Japonicus, 479
Cryptocoelum opacum, 103
Cryptopbialus minutus, 277
Ctenophora, bilateral symmetry
of, 92
characters of, 92, 94
classification of, 95
digestive cavity of, 92, 93
nervous system of, 92
water-vascular system of.
92
Cuculi, 551
Cuma. 293
Cumacea, 294
Cunina octonaria, 63
INDEX.
705
Cunuer, anatomy of, 434
Curlew, 545
Cuttle-fish, 253
gigantic, 261
Cyainus ceti, 291
Cyauea arctica, 67
Cyclocardia novaugliaj, 229
Cyclops, 267
Cyclostomata, 381
Cyclostomi, 409
Cymothoa, 288
Cynthia pyriformis, 392
Cyphonautes, 145
Cyprsea moneta, 249
Cypriuus, 453
Cypris, 279
Cysticercus cellulosae, 114
Cystid, 139
Cystidece, 190, 191
Cytode, 6
DACE, 453
Dactylogyrus amphibothrium,
111
fallax, 111
Daphnia, 279
Darter, 456
Dasypus novem-cinctus, 580
Date shell, 230
Decapoda, 292, 305
Cephalopoda, 260
Deer, 608
Deltocyathus Agassizii, 80
I Jrndroccela, 103
Dendroccelum lacteum, 99, 102
piTca'cum, 100
Deudrojca vircns, 555
Dentaliuni, 237
Desmosticha, 208
Devil-fish, 424
Diatryma, 540
Dibraiifhiata, 260, 264
Dicyema, 97
Dicyemdla, 98
Dicynodon, 512
tigriceps, 512
Didelphia, 571, 628
Didelphys Virginiana, 575
Didus iueptus, 547
Diemyctylus viridesrrns, 481
Differentiation, 6
Digestion, organs of, 631
Digestive canal, 9
Dimorphism, 654
Dingo, 617
Dinichthys Torrelli, 431
Diuoruis giganteus, 538
Dinosauria, 515, 517
Diuotherium, 599
Diomedea exulans, 542
Diplopoda, 336
Diploria cerebriformis, 80
Diplozoon paradoxum, 110
Dipnoi, 425, 426, 462
Diptera, 355, 366
Discina, 151
Diwcophora, 62, 72
Dispersal of animals, 660
Distomum crassum, 109
development of, 105
heterophycs, 109
lanceolatum, 109
macrostomum, 110
ophthalmobium, 109
Distribution, geographical, 658
Dodo, 547
Dog-fish, 420
shark, 420
Dog, varieties of, 617
Doliolum, 398, 404
Dolphin, 455
Doris, 245
Dorosoma cepedianum, 443
Dove, 547
Drum-fish, 443
Duck, black, 543
canvas back, 543
eider, 543
706
INDEX.
Duck, summer, 543
Dugoug, 596
Dysmorphosa, 60
EAGLE, bald-headed, 548
Ear, 641
of clam, 225
of Crustacea, 271
Ears of mammals, 563
Earwig, 344
Earthworm, anatomy of, 167
embryology of, 1 68
Ecardines, 196
Echeneis remora, 454
Echidna hystrix, 573
Echiuarachuius parma, 205
Echinococcus, 117
Echinoderes, 137
Echiuodernr.ata, blood system of,
1.S3, 212
characters of, 178
direct development of,
196, 203, 215
" heart" of, 182, 186
metamorphoses of, 188,
194, 202
nervous system of, 179,
186
skeleton of, 179, 200
viviparous, 192, 203, 204
water- vascular system of,
181, 212
Echiuoidea, 199, 208
Echinorhynchus angustatus, 124
claviceps, 124
Echinorhynchus gigas, 123
Echinus, 199
esculent us, 205
Echiurus, 162
Eciton, 363
Ectoderm, 6
Ectoprocta, 146
Educabilia, 5S2, 591
Edentata, 577, 029
Edible Holothuriaus, 217
sea-urchin, 205
Edwardsia, 78
Eel, breeding habits of, 446
conger, 446
sound produced by, 444
Eel pout, 458
Eggs, winter, of Crustacea, 280
Planarians, 103
Polyzoa, 145
Rotatoria, 136
Elasinobranchii, characters of,
414, 463
development of, 418
eyes of, 417
teeth of, 416
Elaps, 497, 678
Elasmosaurus platyurus, 513
Electrical eel, 450
fish of the Nile, 449
ray, 422
Elephant, 597
Elephas, 597
priuiigenius, 598
Elk, 608
Elytra. 352
Embryology, 13, 643
Encriuites, 183
Encrinus liliformis, 219
Endocyst, 139
Endoderm, 6
Eudostyle, 389
Enneacauthus obesus, 456
Enopla, 157
Enteropueusta, development of,
158
structure of, 157, 159
Eutomostraca, 277, 305
Entoprocta, 146
Eohippus, 602
Epeira vulgaris, 343
Ephemera, 348
Epigonichthys cultellus, 408
Epipodium of mollusks, 238
1XDEX.
707
Epistome of Polyzon, 142
Epistylis, 39
Epithelium, 7
Epizoauthus Araericanus, 79
Equus asinus, 605
caballus, races of, 603
Lemiomis. 604
onager, 604
Eretrnochelys inibricatn, 510
Erimyzon oblougum, 443
Escharina, 144
Estberia Belfragei, 282
Eucboue elegans, 174
Euplectellum aspergillum, 48
Eupomotis aureus, 455
Euproops Dana2, 302
Eupyrgus, 210
Eurypauropus, 338
Eurystomete, 94
Eustrongylus buteonis, 127
chordeilis, 127
gigas, 120
papillosus, 127
Evolution, 11
Existence, struggle for, 673
Eye, 640
dorsal, of Mollusca, 237
of blind craw-fish, 295
of Crustacea, 270
of mollusks, 254
FASCIOLA HEPATICUM, 108
Fauna, 661
chief zoological, 666
Favia, 80
Feathers, 523
Felis concolor, 617
domestica, 617
Ferae, 614
Fer-de-lance, 499
Fertilization of egg, 644
Fierasfer, 459
Filaria hematica, 128
lentis, 128
Filaria hematica, medinensis,
127
sanguinis-hominis, 128
Fishes, see Pisces.
Fishes, anatomy of, 434
bony, 434
characters of, 411
climbing, 457
development of, 445
Elasmobranch, 414
fins of, 411, 428
ganoid, 425
lateral line of, 442
mucous canal of, 442
respiration of, 442
sounds produced by,
442
spiracle of, 417
teeth of, 416, 442
viviparous, 418, 444
Fish-hawk, 548
Fish lice, 297
Fission in Planarians, 102
Flabellum angulare, 80
Flagellata, 31, 40
Flamingo, 544
Flea, 355
sand, 391, 356
snow, 344
water, 279
Flounder, 459
Fluke- worms, 105
Fly, bot, 355
house, 354, 355
Flying-fish, 453
Foraminifera, 24, 27
Forficula, 344
Fossil jelly-fishes, 71
sea-urchins, 125
star-fishes, 116
Frog, 487
anatomy of, 470
Fuligula vallisueria, 543
Fuugia, 82
708
INDEX.
GADUS MORRHUA, 458
Galago, 619
Galeopitbecus volans, 588
Gall-flies, two-winged, 357
Gall-fly, hymeuopterous, 360
Gallinago Wilsonii, 545
Gallinula, 544, 545
Gamrnarus robustus, 291
.Gampsonyx, 286
Ganglion, 8
Ganocephala, 482
Gunoidei, characters of, 425, 463
development of, 432
Gare fowl, 541
Gar-pike, 431
development of, 432
Gasterosteus, 456
Gastraeades, 98
Gastropoda, 239, 252
Gastrotheca, 485
Gastrotricha, 137
Gastrula, 43
Gavial, 514
Generations, alternation of, 652
in Ascidians, 403
in corals, 82
in Trematodes, 105
in worms, 172
Geographical distribution, 658
Geological succession, 068
Geophilus bipuncticeps, 338
Geoplana flava, 100
Gephyrea, development of, 161
structure of, 159, 163
Gerardia, 85
Germigcne, 99, 105
Geryonia, 62
Giant bird, 545
Gibbon, 621
Gills, 637
Gizzard-shad, 443
Gland, green, of lobster, 271
Glass-snake, Opheosaurus, 503
Glires, 582, 629
Globe fish, 463
Globicephalus brachypterus, 595
Globicephalus melas, 595
Globigerina bulloides, 24
Glycimeris siliqua, 230
Glyptodon, 580
Guathostomata, 381
Gouotheca, 61
Goose, barnacle, 544
wild, 544
Goose-fish, 460
Gordiacea, 129
Gordius aquaticus. 130
Gorgonia flabellum, 86
Gorgouidse, 86
Gorilla, 623
Grallatores, 544
Grampus griseus, 595
Graptolites, 61, 71
Grasshopper, anatomy of, 308
Gregarina gigantea, 28
Gregarinida, 28, 31
Grilse, 452
Guanin, 75
Guillemot, 541
Guinea-hen, 546
Guynia annulata, 84
Gymnarchus niloticus, 449
Gymnolremata, 186
Gymnomonera, 22
Gymnophiona, 481, 488
Gymuotus electricus, 450
Gynaecophore of trematode
worms, 110
Gyrodactylus elegans, 111
HADROSAURUS, 515.
Hag-fish, 409
Haimea, 85
Hair, 561
Hair-worms, 129
Hake, 458
Halcampa producta, 78
Haliaetus leucocephalus, 548
709
Halicore, 596
Halistemma carum, 70
Halophila borealis, 138
Halyclystus auricula, 64
Haplodon rufus, 585
Haplophyllia paradoxa, 84
Hare, varying, 586
Harmony between auiinals and
their surroundings, 675
Harvest-men, 342
Hatteria, 511
Hearing, organs of, 250
in mollusks, 250
in insects, 326
Heliopora ccerulea, 85
Heliozoa, 27
Helix albolabris, anatomy of,
245
Hell-bender, 479
Heloderma borridum, 504
suspectum, 504
Hemiaster cavernosus, 121
Philippii, 121
Hemippus, 604
Hemiptera, 349
Herring, 450
Hesperornis, 538
Hessian fly, 357
Heteromita, 33
Heterodontidtv, 416
Heteropoda, 250, 253
Hexapoda, 344
Hexatbyridium piuguicola, 152
venarum, 152
Himantopus nigricollis, 545
Hipparion, 602
Hippocampus, 443
Hippocampus minor, 618
Hippopotamus, 605
llirudinea, development of, 167
structure of, 164, 176
Hoasin, 547
Holocepbali, characters of, 424
Holopus, 186
Holotburia edulis, 217
Floridana, anatomy of, 213
Holothuroidea, 208, 218
Homology, 12
Homo sapiens, 624
Horned toad, 503
Horn-tail, 380
Horse, genealogy of, 602
races of, 604
House-fly, 354
Humming-bird, 551
Hyalonema boreale, 48
Hybocodon, 60
Hybrid ducks, 543
Hybridity, 657
Hydatids, 116
Hydra, anatomy of, 52
development of, 56
vulgaris, 52
Hydractinia echinata, 56
Hydroidea, 52, 72
Hydrozoa, 52, 71
classification of, 73
nervous system of, 62, 65
organs of taste in, 63
Hyla Pickering!!, 484
Hylobates, 622
Hylodes Martiuicensis, 485
Hymenoptera, 359, 367
Hyocrinus, 184
Hyoganoidei, 431
Hyperia, 68, 291
Hyperoartia, 410
Hyperoletra, 410
Hypobytliius calycodes, 392
Hypodermis, 289
Hyraeoidea, 599, 629
Hyrax, 599
IBLA, 273
Ichneumon fly, 361
Ichthyopterygia, 511, 517
Ichthyornis, 538
Ichthyosaur, 512
710
INDEX.
Idotsea, nervous system of, 286,
290
Idyia roseola, 93
Iguana, 504
Iguanodou, 515
Individuality, 656
Ineducabilia, 582
Infusoria, 31, 40
Inheritance, law of, 11
Insectivora, 587, 629
Insects, anatomy of, 308
brain of, 317
characters of, 307, 344
classification of, 365
digestion in, 316
ears of, 325
eye of, 325
embryology of, 329
locomotion in, 327
metamorphosis of, 308
parthenogenesis in, 333
polymorphism in, 348
respiration of, 323
senses nf, 326
useful, 334
Instinct, nn I nre of, 680
Isopoda, 285
Isurus punctatus, 420
Ixodes albipictus, 341
bovis, 341
JACCHUS, 620
Jaws, 631
Jelly-fish, 62
Julus, 336
KANGAROO, 575, 577
Katydid, 676
Killer-whale, 595
King-bird; 552
King-crab, 297
Kinglet, 555
Kiwi-kiwi, 538
Kogia Floweri, 594
LABYRINTHICT, 457
Labyrinthodon, 482, 483
Labyrinthodontia, 482
Laccrtilia, 501, 517
Laclmosterua fu?ca, 352
Lactophrys trigonus, 462
Lselaps, 515
Lagopus leucurus, 546, 546
Lamellibrauchiata, 222
classification of, 236
Lamprej's, 409
Lamp shells, 146
Lancelet, 406
Larva of Echiuoderms, 178, 187.
192, 194, 202
Hydrozoa, 83
Insects, 328
Worms, 171
Lasso-cells in Aurelia, 67
Hydra, 53
Infusoria, 37
Polyps, 76, 81
Sponges, 43
Worms, Kil
Lateral line of fishes, 442
Leaf insect, 657
Leech, 164
Lem nisei, 123
Lemur, 618
Lepas fascicularis, 273
Lepidoptera, 357, 367
Lepidosiren paradoxa, 430
Lepidosteus, development of, 432
osseus, 431
platystomus, 432
spatula, 432
Lepidurns Couesii, 282
Lepomonera, 22
Leptocardii, 406, 408
L'eptocephalus, 446
Leptodiscus medusoides, 34
Leptoplana, 102
Leptosynapta Girardii, 216
Leptychaster. 19d
INDEX.
711
Lepus Amcricanus, 586
Bairdii, 586
Lerutea branchialis, 277
Lerneonema radiata, 278
Leucocbloridium, 110
Lice, plant, 350
Ligula simplicissiina, 120
Limaciua arctica, 238
Limax flavus, 245
Limicolre, 544
Limnadia Agassizii, 282
Limnetis Gouldii, 281, 282
Limuoria terebrans, 290
Limpet, 248
Liinulus, anatomy of, 297
development of. 300
Polyphemus, 297
Linen*, 156
Lingual ribbon of mollusks, 256,
632
Linguatulina, 340
Liugula, 147, 148, 149
pyramidata, 153
Liodon, 500
Lissotritor. punctatus, 481
Lithobius Americanus, 338
Litbodomus, 230
Littorina littorea, 248
Liver fluke, 108
Lizards, sea, 504
structure of, 5.01
Lobatre, 95
Lobster, anatomy of, 266
Locust, anatomy of, 308
Loggerhead turtle. 510
Loligo pallidn, 253
Pealii, anatomy of, 253
Loon, 541
Lopbius piscatorius, 460
Lopbobrancbii, 460
Lopbobelia prolifcra, 80
Lopbopbore, 140
Loxosoma, 143, 145
Luceruaria, 63
Lucifuga subterraneus, 459
Luidia, 196
Lumbricus agricola, 168
rubellus, 168
terrestris, 167
Lunatia beros, anatomy of, 241
Lung-fish, 428
Lymnaeus appressus, 246
elodes, 246
Lymphatics, 636
Lynx Canadensis, 617
rufus, 617
Lyre-bird, 552
Lystrosaurus, 513
Lytta margiuata, 353
MACACUS, 620
Macbilis, 345
Mackerel, 456
Macrobiotus Americanus, 340
Macropus thetidis, 577
Mactra lateral is, 229
ovalis, 231
Madrepora cervicornis, 82
Ma-andrina, 80, 81, 84
Magpie, 554
Malacopoda, 335, 365
Malapterurus electricus, 449
Male fishes, obstetrical habits of,
449, 461
Mallotus villosus, 452
Mammalia, anatomy of, 564
characters of, 557, 628
development of, 566
ears of, 563
hair of, 561
horns of, 561
limbs of, 560
music of, 569
sexual differences of, 566
skeleton of, 558
teeth of, 562
Mammals, development of, 64U
Mammoth, 598
712
INDEX.
Man, embryology of, 650
origin of, 627
relation to apes, 624
skull, 626
varieties of, 627
Manatus, 595
Mandrill, 620
Manis, 580
Mantis, 345
Manubrium, 70
Marine animals, distribution of,
664
Marmoset, 619
Marsupial ia, 574
Marsipobranchii, characters of,
409, 410
Mastodon giganteum, 599
May fly, 347
Mecoptera, 315
Meckelia ingens, 156
Medusa, 59
Megalops, 293
Megapoclius, 546
Megatherium, 579
Melanogrammus reglefinus. 458
Melipoua, 365
Mellita testudinata, 205
Melo6 augusticollis, 353
Melospiza, 555
Membranipora, 138, 144
Memory of animals, 681
Menhaden, 450
Menobranchus, 478
Menopoma Alleghaniensis, 479
Merostomata, 297, 306
Mesenteries of polyps, 75
Mesoderm, 6
Mesogonistius chsetodon, 455
Mesohippus, 602
Mesozoa, 97
Metabola, 366
Metamorphosis, 651
of Batrachia, 476
suppressed, 477, 485
Metamorphosis, of Crustacea,
293
of echinoderms, 187, 192,
194
Metridium marginatum, 74
Miastor, 653
Microsauria, 482, 483
Microstomum lineare, strobilation
iu, 103
Midas, 620
Migrations of animals, 667
Millepedes, 336
Millepora alcicornis, 57
nodosa, 57
Miluesium tardigradum, 361
Mimicry, protective, 675
Mimetes niger, 622
pithecus, 621
Mind, in animals, 682
Miohippus, 602
Mites, 341
Moa, 538
Moccasin snake, 500
Molacanthus Pallasii, 463
Mola rotunda, 462
Mole, 587
Molgula, 399
Mollusca, development of, 233,
243
structure of, 220
Molluscs, edible, 248
Monads, 31
Monas termo, 31
Monera, 18, 20
Money, shells used as, 269
Monitor, 504
Monkey, 619
Monocaulus, 60
Mouodelphia, 571, 577, 629
Monodon monoceros, 594
Monograptus, 62
Monostomum, development, of,
107
Monotremes, 571
INDl-'.X.
713
Morphology, 5
Morula, 43
Mosasaurus maximus, 500
Mosquito, 357
Moths, 358
Mound bird, 546
Mouse, 586
Mucous canal of fishes, 442
Mud dauber, 383
Mud fish, 432
puppy, 478
sun fish, 443
Mullet, 443
Mus, 586
Musca domestica, 355
Musical fishes, 443
Music of mammals, 569
Mussa, 80
Mussel, edible, 248
development of, 254
Mustek foina, 617
Mustelus canis, 420
hevis, 420
vulgaris, 420
Muzir, 604
Mya arenaria, 222
Mygale avicularia, 363
Heutzii, 363
Myliobatis, 416, 424
fremeuvillii, 422
Mylodon, 579
Myriopoda, 336, 365
Myriotrochus Riukii, 216
Myriozoum subgracile, 138
Mysis, 293
Mysticete, 592
Mytilus edulis, 228
Myxiue, 409
NAJA, 499
Nanemys guttatus, 510
Narwhale, 594
Nasua, 615
Natatores, 544
Natica heros, anatomy of, 241
Natrix torquata, 495
Nauplius, 274
Nautilus pompilius, 260
Ncbalia, 291
bipes, 292
Necturus lateralis, 478
Nematelminthes, development of,
122
structure of, 12i, 133
Nematodes, 125, 133
Nematogene, 99
Nemertian worms. 154
Nemertina, development of, 1 •">.">
structure of , 154, 157
Neochanna, 452
Nephila plumipes, 343
Nereis virens, anatomy of, 169
Nervous system, 638
Nervous system of ctenophores,
92
insects, 317
hydrozoa, 62, 65
Nests of birds, 536
Neuroptera, 349
Neurula stage of leeches, 166
worms, 168
Nighthawk, 551
Noctiluca miliaris, 33
Noises produced by fishes, 442,
443
Notacanthus, 446
Notochord of ascidians, 396
Notommata, 135
Nototrema marsupiatum, 485
Nudibranch molluscs, 245
Numerius lonjrirostris, 545
Nummulites, 25
Nurse of trematode worms, 107
Nyctea nivea, 549
OCULINA, 80
Octacnemus bythius, 392
Octopod cephalopoda, 260
714
INDEX.
Octopus Bnirdii, 262
Odonata, 348
Odontophore, 256
Odontornithes, 537, 557
(Ecodoma, 382
Oligochaeta, 174
Onchidium, 257
Ouiscus murarius. 287
Operculum of gastropoda, 261
Ophidia, 496, 517
Ophiocoma vivipara, 192
Ophiopholis bellis, 192
Ophiuridea, 191, 198
Opisthodelphys ovifera, 485
Opisthomi, 446
Opossum, 575
Orang, 622
Orca gladiator, 595
Oreortyx pictus, 546
Organisms, 6, 23
Organs, comparative anatomy of,
631
of circulation, 635
of digestion, 631
of respiration, 637
of sense, 640
of smell, 642
nature of, 4, 6, 8, 9
Origin of species, 671
Ornithodelpliia. 571, 628
Ornitliosauria, 516
Orohippus, 602
Orthagoriscus oblongus, 462
Orthoptera, 345
Oscines, 552, 553
Oscula of sponges, 43
Osmerus eperlanus, 452
mordax, 452
Osprey, 548
Ostracoda, 279
Ostrich, 539
Otocyst, 270, 641
of clam, 245
of worms, 101
Ova, winter, of planarians, 103
of polyzoa, 145
of Rotatoria, 136
Ovibos moschatus, 610
priscus, 610
Ovis argali, 610
aries, 610
montana, 610
Owl, 548
Ox, 612
Oxyuris vennicularis, 125
Oyster, pearl, 232
PADDLE PISH, 427
Palseocaris typus, 272
Paleontology, 16
Palamedea cornuta, 546
Palapteryx, 538
Palechinida, 205, 208 .
Palisade worm, 126
Paludicella, 140
Pandion haliae'tus, 548
Pangolin, 580
Panopsea arctica, 230
Paragorgia arborea, 86
Paramecium caudatum, 35
Parr, 452
Parroquet, 550
Parrot, 550
Parthenogenesis, 54, 652
in ascidians, 403
Partridge, 546
Passeres, 551
Patella vulgata, 248
Pauropoda, 336, 366
Pauropus Lubbockii, 336
Pearl oyster, 232
shell, 232
Pedicellaria, 179
Pediculati, 460
Fed i pal pi, 342
Pelagic molluscs, 238. 249
Pelecanus erythrorhynchus, 535
Pelican, 542
INDEX.
715
Pelobates, 484
Pelodytes (a genus of frogs), 484
(a geuus of thread worms),
122
Pelomyxa palustris, 24
Pelopseus, 363
Peltogaster, 276, 277
Pelycosauria, 512
Penella, 278
Penguin, 541
Penuatula aculeata, 86
Pentacriuu*. 183
Pentacta frouclosa, anatomy of,
209
Pentastoma, 340
Pentrcmites, 189
Perca fluviatilis, 455
Perch, 455
sea, anatomy of, 434
Peridinium, 34
Peripatus, anatomy of, 335
Perisarc, 61
Perissodactyla, 600
Perla, 347
Perophora, 391
Petalosticlia, 205, 208
Petromyzon mariuus, 410
niger, 410
nigricans, 410
Pezophaps sol i tar i us, 547
Phalangella flabellaus, 144
Phalangium, 342
Pharyngobranchii, 408
Phascolosoma caementarium, 162
Gouldii, 159
Pheronema Annae, 48
Phocoena brachycium, 595
liueata, 595
Phcenicopterus ruber, 544
Phorouis, 161
Phosphorescent annelides, 175
ascidians, 392
Hydrozoa. 70
insects, 355
Phosphorescent aunelides, Pro
tozoa, 33
worms, 175
Phrynosoma Douglassii, 503
Phylactolsemata, 144
Phyllocarida, 291, 305
Phyllopoda, 280
Physa heterostroplia, 245
Physalia arethusa, 68
Physeter macrocephalus, 594
Physiology, 12
Picnrise, 550
Pigeon, anaiomy of, 525
Pilidium, 156
Pill bug, 286, 287
Pipa Americana, 485
Pipe fish, 461
Pirarucu, 442
Pisces, characters of, 411, 463
development of, 418, 432,
445
Pissodes strobi, 352
Plagiostomi, 419
Plagtisia, 460
Planarian worms, 99
land, 103
lasso-cells of, 101
nervous system of, 101
parasitic, 103
Planaria torva, 101
Plant lice, 350
Planula, 59
Platygaster, 361
Platyhelminthes, 99, 120
Platyptera, 347
Plectognathi, 461
Pliohippus, 602
Plesiosaunis, 513
Plethodon erythronotum, 479
Pleurobrachia rhododactyla, 93
Pleurolepis pellucidus, 456
Pleuroma, 298
Pleurum of insects, 309
Plumatella, 140
716
INDEX.
Pneumophora, 134
Podostomata, 295
Podura, 344
Pogonias chromis, 443
Pogy, 450
Poisonous bati'achians, 475
jelly fish, 67
snakes, 497, 499
Polycelis, 102
Polycladus Gayi, 101
Polydora, development of, 171
Polykrikos, 37
Polymorphism, 654
in insects, 348
Polyodou folium, 428
Polypedates, 484
Polypide, 181
Polyps, coral, 74
Polypterus bichir, 428
Senegalus, 428
Polystoineae, 110
Polystomum integerrimum, 111
Polyzoa, development of, 143
structure of, 138, 146
Polyzoarium, 139
Pomatomus saltatrix, 455
Pomolobus pseudoharengus, 450
Pomotis, 455
Porcellio, 286, 290
Porcupine fish, 462
Porifera, 42, 49
Porphyrio coerulescens, 545
Porpoise, 595
Porsana Carolina, 544
Portuguese man-of-war, 69
Potamotrygon, 424
Pourtalesia, 206
Prestwichia rotuudatus, 302
Primates, 618, 629
Primnoa reseda, 86
Pristis antiquorum, 421
Perroteli, 421
Proboscidea, 597, 629
Procyon lotor, 615
Proglottis of tape worms, 156
trematode worms, 150
Prorhynchus, 196
Proscolex of tape-worms, 114
trematode worms, 108
Prosimiae, 618
Protamoeba, 19
Protaster, 193
Protective resemblance, 487, 675
Proteida, 478, 488
Proteus, 478
Protista, 2
Protohippus, 602
Protomonas amyli, 19
Protomyxa, 19
Protomyxa aurantiaca, 19
Protoplasm, 5
Protoplasta, 31
Protopterus annectens, 464
Protozoa, 17, 41
contractile vesicles of, 32
Pseudemys, 510
Pseudes paradoxa, 487
Pseudobrauchus striatus, 478
Pseudocrinus, 190
Pseudofilaria, young of gregariua,
30
Pseudopleurouectes Americauus.
460
Pseudopodia, 23
Pseudopus, 502
Psolus ephippifer, 215
Psychology, 12
Ptarmigan, 546
Pteranodon, 517
Pteraster, 196
Pterodactyle, 516
Pteropoda, 238, 252
Pterosauria, 516, 517
Pterotrachea coronata, 271
Ptyelus lineatus, 350
Puffer fish, 462
Pulex irritans, 356
Pulmonata, 245
INDEX.
717
Pupa of insects, 308
of the barnacle, 296
Purpura lapillus, 243
Pycnogouidoe, 339
Pycnopodia, 115
Pygidium, 304
Pyrosoma gigas, 392
Pythonomorpha, 500, 517
QUOHOG, 229
RACCOON, 615
Radio! aria, 26, 27
Rail, 544
Raja eglauteria, 422
erinacea, 421
fluviatilis, 424
laevis, 421
Raua, 487
halecina, 470
Rangifer caribou, 609
tarandus, 609
Raptores, 548
Rasores, 546
Rat, black, 586
blind, 586
Ratitse, 538, 557
Rattlesnake, 499
Ray, 421
sting, 424
Reasoning power of animals,
680
Redia of trematodes, 108, 109
Reefs, coral, formation of, 87
Reindeer, 609
Renilla reniformis, 86
Reproduction, 13, 643
Reproduction of lost parts in
Hydrozoa, 53
Planarians, 102
Batrachia, 481
Reptilia, characters of, 488, 517
development of, 495
skeleton of, 489
Reptilia, sexual differences of,
494
teeth of, 491, 499
viviparous. 495, 497
Resemblance, protective, 487, 675
Respiration, organs of, 637
Rhabdoco-la, 103
Rhabdopleura mirabilis, 145 •
Rhamphorynclms, 517
Rhea Americana, 539
Rhiuichthys atronasus, 453
Rhizocriuus lofotensis, 184
Rhizopoda, 22, 27
Rhombogeue, 99
Rhopalodina, 214
Rhynchocephalia, 511, 517
Rhyncodesmus sylvaticus. 103
Rhytina Stelleri, 596
Robin, 556
Rodeutia, 582, 629
Root barnacle, 2
Rotalia, 25
Rotatoria, development of, 136
structure of, 134, 138
Rotifera, 134
Rotifer vulgaris, 134
Rugose corals, 84
Rurninantia, 605
SACCAT/E, 95
Sacculina, 276
Sagitta, 132
Salamander, 479
Saleuoglyph snakes, 499
Salmo fontinalis, 452
qtiinnat, 451
salar, 452
Salmon, 451
Salpa, development of, 401, 404
structure of, 391, 398
spinosa, 401
Sarcorhamphus gryphus, 548
Sauropterygia, 513, 517
Sauropsida, 518
718
INDEX.
Saururae, 537, 557
Saw fish, 421
Saw fly, 360
Saxioava, 230
Scalpellum, 273
Scaphiopus, 484
Scnphirhynchops platyrhynchus,
*427
Scaphopoila, 237, 252
Sceleporus imdulatus, anatomy
of, 493, 504
Scbizaster fragilis, 206
Scbizopoda, 294
Scolex of tape-worms, 114
trematode worms, 108
Scolopeudra gigautea, 338
heros, 338
Scolopendrella, 344
Scomber scombrus, 456
Scypbopbori, 449
Seal, 614
Sea-anemone, 74
Sea-cow, 595
Sea-cucumber, anatomy of, 210
apodous, 215
pedate, 215, 217
Sea-fan corals, 86
Sea-borse, 443
Sea-lion, 614
Sea-pen, 86
Sea-squirts, 386
Sea-worms, 169
Selacbe maxima, 420
Selacbians, 414
Semotilus rbotbeus, 453
Semuopithecus, 621
Sense, organs of, 640
Serolis Gaudicbaudi, 286
Sertularia, 61
Sewellel, 585
Sexual coloration in fishes, 444
Shad, 450, 451
gizzard, 443
Shagreen, 415
Shark, basking, 420
hammer beaded, 421
mackerel, 419
Port Jackson, 416
thresher, 420
Sharks, 414
Sheep, varieties of, 609
Sheep, musk, 610
Sheep hydatid, 118
Shells, fossil, 270
Ship worm, 250, 254
Shovvt'l, 585
Shrew, 587
Shrike, 555
Shrimp, 292, 294
Sida, 279
Simise, 619
Sipbonaptera, 355
Sipbonophora, 68, 72
Siphouops, 482
Sipbydora ecbinoides, 47
Sipunculus, 159
Siredon, 479
Sirenia, 595, 629
Siren lacertina, 478
Sivatherium, 605
Skates, 421
development of, 419
Skull, brachycepbalic, 627
dolicocephalic, 627
Slug, 245
Smelt, 452
Smolt, 452
Smynthurus, 344
Snail, 245
Snake, hooded, 499
striped, anatomy of, 498
Snakes, 496
protective coloration of
497
viviparous, 497
Snipe, 545
Snow-flea, 344
Solaster endeca, 115
1XDEX.
719
Solitaire, 547 .
Somateria mollissima, 543
Somite, 266
Sorex platyrhiuus, 587
Sounds produced by insects, 349
Sounds, tisbes', 442
Spalax, 586
:Sparrow, 555
Spatangus, 206
Specialization, 6
Species, origin of, 672
variation of, 10, 672, 673
Spermaceti, 593
Spermatozoa, formation of, 644
Sphserodorum, 231
Spbargis coriacea, 510
Sphenodon, 511
Spueotyto cunicularia, 549
Sphex ichueumonea, 363
Sphinx, 359
Spiders, 342
Spirialis Gouldii, 239
Spirula Peronii, 261
Sphyrna zygtena, 421
Spirorbis, 175
Sponges, 42
silicious, 47
useful, 49
Spongia adriatica, 49
equina, 49
gossypina, 49
tubulifera, 49
Spongilla, 47
Spoonbill fish, 428
Sporocyst of Nematodes, 109
Spring-tails, 344
Squalus Americanus, 420
Squamella oblonga, 176
Squid, anatomy of, 273
Squilla, 292
Squirrels, flying, 583
Sur-fish, 178, 191, 193
anatomy of, 178
Star-worm, 159
Statoblast, 145
Stegocephala, 482, 488
Steller's manatee, 596
Stentor polymorphic, 36
Sternum of insects, 309
Stick insect, 677
Stickleback, 456
Stilt, 546
Sting rays, 424
Stomapoda, 292, 305
Stone lilies, 183
Strobila of Hydrozoa, 66
Strobila of Planarians. 102
tape-worms, 114
Strobihitioninworms, 102, 10:5, 172
Struggle for existence, 673
Struthio camelus, 539
Sturgeon, embryology of, 427
Sturgeon, 427
Stygicola dentata, 459
Stylaster, 58
Styliola vitrea, 238
Stylochus elliptica, 101
Stylocordyla, 48
Stylops, 353, 354
Sucker, 453, 454
Suctoria, 40
Sun-fish, fresh water, 455
banded, 455
spotted, 456
salt-water, 462
Swimming, in fishes, 444
Sycandra, 44
Sycon ciliatum, 45
Syllis, 215
Symmetry, bilateral, in cteno-
phores, 92, 93
echinoderms, 202
Symphyla, 344 .
Synapta, 216, 217
Syncarida, 272
Syuguathus peckianus, 461
Synthetic types, 483, 679
Syrinx, 526, 552
720
INDEX.
Syrniura cinereum, 549
Syrphus, 355
TABULATE CORALS, 58
Tachiua, 375
'1 a-uia acanthotrias, 115
bacillaris, 113
coenurus, 118, 119
echinococcus, 116
mediocanellata, 116
solium, 113, 115
Tn?niata, 95
Tape-worms, development of, 112
structure of, 111
Tardigrades, 339
Tarpau, 604
Tasmanian devil, 575
wolf, 575
Taste, organs of, in Hydrozoa, 63
insects, 326
polyps, 77
Tautogolabrus adspersus, anato-
my of, 434
Teeth, 631
rudimentary, 402
of sea-urchins, 200
Teleocephali, 449
Teleostei, characters of, 434, 464
anatomy of, 434
Tentaculifera, 34, 40
Teratology, 646
Terebratulina septentrionalis, 146
development of, 150
Terebrella. 174
Teredo navalis, 230, 234
Tergipes lacinulata, 245
Tergum of insects, 309
Terines. 347
flavipes, 347
Terrapin, 510
Testicardines, 146
Testudo Indica, 510
Tetrabranchiata, 260, 264
Tetradecapoda, 286, 305
Tetrao, 546
Tetrarhynchus, 120
Tetrastemma serpentinum, 157
Tetrastoma renale, 110
Tetrodon laevigatus, 462
Thalascaris, 295
Thalassochelys caouana, 510
Tlialiacea, 398, 405
Thamnocephalus brachyurus, 283
Theca of corals, 79
Thelyphonus giganteus, 342
Theriodonts, 513
Theromorpha, 512, 517
Thrasher whale, 595
Thrips, 348
Thylacinus, 575
Thyone briareus, anatomy of, 213
Thysanoptera, 348
Thysanura, 344
Tick, 341
Tinamous, 547
Tipula, 377
Tissue, bony, 8
cartilaginous, 7
connective, 7
elastic, 7
epithelial, 7
fibrous, 7
gelatinous, 7
muscular, 8
nervous, 8
Titanophis, 500
Toad, 485
horned, 503
metamorphosis of, 477
poison of, 475
spade-footed, 484
Tomocerus plumbeus, 344
Tooth shell, 237
Torpedo marmoratus, 422
occidentalis, 422
Tortoise, 510
Touch, organs of, in Crustacea,
271
IKDKX.
721
Touch, organs of, in mollusks,
250
Toxodontia, 600, 629
Trachymedusse, 62
Trachystomata, 478, 487
Transmission, law of, 11
Trematodes, structure of, 104,
121
development of, 105
pupa of, 107
Trichina spiralis, 127
Trichocephalus dispar, 127
Trigla, 443
Trigouocephalus, 499
Trilobita, young, 303
Trinucleus. young of, 303
Triton, 478
Trivia californica, 239
Trochilus colubris, 551
Trochosphere, 233, 244
of polyzoa, 144
of worms, 105
Trochus, development of, 244
Trout, 452
Trunk-fish, 462
Trygon, 424
Tubularia, 60
Tubipora, 85
Tunicata, development of, 393,
401
structure of, 386, 405
Turbellaria, 100, 120
Turdus migratorius, 556
Turkey, wild, 546
Turtle, green, 510
hawkbill, 510
loggerhead, 510
sea, 510
snapping, 510
soft-shell, 510
swamp, anatomy of, 506
tortoise-shell, 510
Tylenchus scandens, 128
Tylos, 286
Typhlocolax acuminnta, 103
Tyroglyphus sacchari, 341
UI-OCYATFIUS ARCTICUP, 80
Umbellularia groenlandica, 86
Ungulata, 600, 629
Unio complanatus, 224
Urchins, sea, 199
Urodela, 478, 484, 488
Urolabes palustris, 128
Ursus Americanus, 616
arctos, 616
maritimus, 616
Urus, 612
Uvella, 32
VARANUS, 504
Variation of species, 672
Veliger stage of mollusks, 232,
239, 243, 246
Velum of rotifers, 176, 178
Venus mercenaria, 229
Vermes, characters of, 96
classification of, 176
Vertebra, 375
Vertebrata, characters of, 369
classification of, 630
brain of, 372
ear of, 385
eye of, 385
hair of, 383
limbs of, 376
notochord of, 373
scales of, 383
skeleton of, 375
skull of, 377
teeth of, 381
Vertebrates, relations of ascidians
to, 386
mollueks to, 221
worms to, 157, 167
Vespertilio subulatus, 591 I
Vinegar worm, 128
Viper. 499
INDEX.
Yipera, 499
Vitellogene, 105
Viviparous fishes, 444
reptiles, 495
sea-urchins, 203, 204
star-fish, 192, 196
Vorticella, 39
Vulture, 548
WALRUS, 614
Wapiti, 608
Wasp, 364
Water-bear, 340
Water-flea, 279
Watering-pot shell, 230
Waxwing, 555
Whale, 591
fishery, 594
sperm, 593
bone, 592
white, 595
Whale's-tongue worm, 157
Whelk, 248
White ant. 347
Worms, 96
flat, 99
fluke, 104
nemertean, 154
parasitic, 103, 104
phosphorescent, 175
round, 121
strobilation in, 102, 103
tape, 111
thread, 121
trematode, 104
Worm, whale's-tongue, 157
Wren, 555
XlPHOSURA, 304
ZEUGLODON, 595
Zoantharia, 79, 91
Zoanthus, 79
Zoea, 293
Zoogeography, 16, 658
Zooids, 56, 400
OUTLINES OF COMPARATIVE EMBRYOLOGY ;
OR. LIFE HISTORIES OP ANIMALS, INCLUDING MAN. By A. S. PACK-
ARD. Copiously Illustrated. 8vo. $2.50.
" An ample work of reference for advanced students It would not bo
ca^y to find u work on the branch of Animal Physiology of which it treats, which dis-
plays such acute and delicate analysis, or presents a more complete statement of the
recondite facts."— Tribune.
" Must remain for many years the one standard work on the subject. . . . Alto-
gether it forms one of the most valuable works of science yet published in this coun-
try, and it is safe to say that, no working naturalist can do without it." — Prof. E. S.
MORSE, in Poji't/ar Science Monthly.
" It occupies worthily an important place absolutely unfilled to this time."— Chan-
cellor WINCIIELL.
GUIDE TO THE STUDY OF INSECTS,
AND A TREATISE ON THOSE INJURIOUS AND BENEFICIAL TO CROPS.
For the use of Colleges, Farm- Schools, and Agriculturists. By
A. S. PACKARD, M.D. With 11 Plates and 650 Woodcuts.
Eighth edition. $5.
"I hold that your work ought, in connection with Harris's 'Treatise on Insects
Injurious to Vegetation,' to which it is, as it were, the key, to be introduced in all onr
agricultural colleges, as the best text-book of that kind now extant."— Professor L.
AGASSIZ.
"Your 'Guide to the Study of Insects' has become the text-book up here."— G.
CROTCH, Librarian of Cambridge University, England.
" But it is of its scientific merits especially we wish to speak, and of which we can
speak in no qualified terms of praise. The first two parts are, we do not hesitate to
affirm, the best things of the kind that our language possesses ..... We have
seldom fallen on so thoroughly good a scientific treatise, and we can only conclude
our notice of it by advising all our natural history readers to make its acquaintance.
There is no work we should prefer to it as a book for the student " — Scientific Opin-
ion, London.
"Among the best, guides to the study of insects which at present exist in our liter-
ature."— Dr. A. DOHRN, in the Entomological Journal, of Stettin, Prussia.
"The study of Entomology is one that can be almost as easily pursued in the
echool-room as Botany, and we should be glad to see the experiment tried. Dr.
Packard's work is well fitted, by its clear, simple style, for use as a text-book." — The
Michigan Teacher.
"In typography and illustrations t lie part before us leaves nothing to be desired,
while the author's style is very perspicuous. We hope the work will be used as
intended, in colleges and farm-schools and by agriculturists ...... In every
particular of text, illustrations, and manufacture, it is thoroughly well done."— The
Nation.
"Altogether, we are immensely pleased with this work. It is assuredly, all in all,
the fullest, most modern, and most clearly-written treatise on insects we have ever
Science Review, London.
"The most recent memoirs connected with these subjects have been made use of
by the author ; and this part of his work is certainly the best manual of entomology
which the English reader can at present obtain." — Nature, London.
'• As a practical treatise on American entomology, with reference especially to the
insects injurious or beneficial to crops, it stands almost alone, and reflects the highest
credit upon American scholarship, patience, and scientific skill." — New York Tribune.
HENRY HOLT & CO., PUBLISHERS, NEW YORK.
THE AMERICAN SCIENCE SERIES.
THE principal objects of the series are to supply the lack — in
?ome subjects very great — of authoritative books whose princi-
ples are, so far as practicable, illustrated by familiar American
facts, and also to supply the other lack that the advance of Sci-
ence perennially creates, of text-books which at least do not
contradict the latest generalizations. The scheme systemati-
cally outlines the field of Science, as the term is usually em-
ployed with reference to general education, and includes
ADVANCED COURSES for maturer college students, BRIEFER
COURSES for beginners in school or college, and ELEIMENTARY
COURSES for the youngest classes. The Briefer Courses are not
mtre abridgments of the larger works, but, with perhaps a
single exception, are much less technical in style and more
elementary in method. While somewhat narrower in range
of topics, tney give equal emphasis to controlling principles.
The following books in this series are already published :
THE HUMAN BODY. By H. NEWELL MARTIN, Professor in
the Johns Hopkins University.
Advanced Course. Svo. 655 pp.
Designed to impart the kind and amount of knowledge every
educated perscn should possess of the structure and activities
and the conditions of healthy working of the human body.
While intelligible to the general reader, it is accurate and suffi-
ciently minute in details to meet the requirements of students
who are not making human anatomy and physiology subjects of
special advanced study. The regular editions of the book contain
an appendix on Reproduction and Development. Copies without,
this will be sent when specially ordered.
From the CHICAGO TRIBUNE: " The reader who follows him through
to the end of the book will be better informed on the subject of
modern physiology in its general features than most of the medical
practitioners who rest on the knowledge gained in comparatively an-
liquated text books, and will, if possessed of average good judgment
and powers of discrimination, not be in any way confused by state-
ments of dubious cuestionsor conflicting views."
2 THE AMERICAN SCIENCE SERIES.
THE HUMAN BW( .—Contimted.
Briefer Course. I2mo. 364 pp.
Aims to make the study of this branch of Natural Science a
source of discipline to the observing and reasoning faculties,
and not merely to present a set of facts, useful to know, which
the pupil is to learn by heart, like the multiplication-table.
With this in view, the author attempts to exhibit, so far as is
practicable in an elementary treatise, the ascertained facts of
Physiology as illustrations of, or deductions from, the two car-
dinal principles by which it, as a department of modern science,
is controlled, — namely, the doctrine of the " Conservation of
Energy" and that of the " Physiological Division of Labor. " To
the same end he also gives simple, practical directions to assist
the teacher in demonstrating to the class the fundamental facts
of the science. The book includes a chapter on the action upon
the body of stimulants and narcotics.
From HENRY SEWALL, Professor of Physiology, University of Michi-
gan : " The number of poor books meant to serve the purpose of
text-books of physiology for schools is so great that it is well to
define clearly the needs of such a work: I. That it shall contain ac-
curate statements of fact. 2. That its facts shall not be too numer-
ous, but chosen so that the important truths are recognized in their
true relations. 3. That the language shall be so lucid as to give no
excuse for misunderstanding. 4. That the value of the study as a
discipline to the reasoning faculties shall be continually kept in view.
I know of no elementary text-book which is the superior, if the
equal, of Prof. Martin's, as judged by these conditions."
Elementary Course. 1 2 mo. 261 pp.
A very earnest attempt to present the subject so that children
may easily understand it, and, whenever possible, to start with
familiar facts and gradually to lead up to less obvious ones.
The action on the body of stimulants and narcotics is fully treated.
From W. S. PERRY, Supet intend? nt of Schools, Ann Arbor, Mich.:
*" I find in it the same accuracy of statement and scholarly strength
that characterize both the larger editions. The large relative space
given to hygiene is fully in accord with the latest educational opinion
and practice; while the amount of anatomy and physiology comprised
in the compact treatment of these divisions is quite enough for the
«nost practical knowledge of the subject. The handling of alcohol
and narcotics is, in my opinion, especially good. The most admira-
ble feature of the book is its fine adaptation to the capacity of younger
pupils The diction is simple and pure, the style clear and direct, and
the manner of presentation bright and attractive "
THE AMERICAN SCIENCE SERIES. 3
ASTRONOMY. By SIMON NEWCOMB, Professor In the Johns
Hopkins University, and EDWARD S. HOLDER, Director of
the Lick Observatory.
Advanced Course* 8vo. 512 pp.
To facilitate its use by students of different grades, the sub«
ject-matter is divided into two classes, distinguished by the size
of the type. The portions in large type form a complete course
for the use of those who desire only such a general knowledge
of the subject as can be acquired without the application of ad-
vanced mathematics. The portions in small type comprise ad-
ditions for the use of those students who either desire a more
detailed and precise knowledge of the subject, or who intend to
make astronomy a special study.
From C. A. YOUNG, Professor in Princeton College : " I conclude
that it is decidedly superior to anything else in the market on the
same subject and designed for the same purpose."
Briefer Course. I2mo. 352 pp.
Aims to furnish a tolerably complete outline of the as-
tronomy of to-day, in as elementary a shape as will yield satis-
factory returns for the learner's time and labor. It has been
abridged from the larger work, not by compressing the same
matter into less space, but by omitting the details of practical
astronomy, thus giving to the descriptive portions a greater
relative prominence.
From THE CRITIC: "The book is in refreshing contrast to the
productions of the professional schoolbook-makers, who, having only
a superficial knowledge of the matter in hand, gather their material,
without sense or discrimination, from all sorts of authorities, and
present as the result an indigesta moles, a mass of crudities, not un-
mixed with errors. The student of this book may feel secure as to
the correctness of whatever he finds in it. Facts appear as facts, and
theories and speculations stand for what they are, and are worth."
From W. B. GRAVES, Master Scientific Department of Phillips
Academy : " I have used the Briefer Course of Astronomy during the
past year. It is up to the times, the points are put in a way to inter-
est the student, and the size of the book makes it easy to go over the
subject in the time allotted by our schedule."
From HENRY LEFAVOUR, late Teacher of Astronomy, U'iiliston Semi~
nary : " The impression which I formed upon first examination, that
it was in very many respects the best elementary text-book on the
subject, has been confirmed by my experience with it in the class-
room."
4 TffE AMERICAN SCIENCE ZEKIES.
ZOOLOGY. By A. S. PACKARD. Professor in Brown
sity.
Advanced Course. 8vo. 7 19 pp.
Designed to be used either in the recitation-room or in the
laboratory. It will serve as a guide to the student who, with a
desire to get at first-hand a general knowledge of the structure
of leading types of life, examines living animals, watches theii
movements and habits, and finally dissects them. He is pre-
sented first with the facts, and led to a thorough knowledge
of a few typical forms, then taught to compare these with
others, and finally led to the principles or inductions growing
out of the facts.
From A. E. VERRILL, Professor of Zoology in Yale College: " The
general treatment of the subject is good, and the descriptions of
structure and the definitions of groups are, for the most part, clear,
concise, and not so much overburdened by technical terms as in sev-
eral other n.anuals of structural zoology now in use."
Briefer Course. I2mo. 334 pp.
The distinctive characteristic of this book is its use of the
object method. The author would have the pupils first examine
and roughly dissect a fish, in order to attain some notion of
vertebrate structure as a basis of comparison. Beginning then
with the lowest forms, he leads the pupil through the whole
animal kingdom until man is reached. As each of its great
divisions comes under observation, he gives detailed instruc-
tions for dissecting some one animal as a type of the class, and
bases the study of other forms on the knowledge thus obtained.
From HERBERT OSBORN, Professor of Zoology, Iowa Agricultttral
College : " I can gladly recommend it to any one desiring a work of
such character. While I strongly insist that students should study
animals from the animals themselves, — a point strongly urged by
Prof. Packard in his preface, — I also recognize the necessity of a
reliable text-book as a guide. As such a guide, and covering the
gi-ound it does, I know of nothing better than Packard's."
First Lessons in Zoology. I2mo. 290 pp.
In method this book differs considerably from those men-
tioned above. Since it is meant for young beginners, it de-
scribes but few types, mostly those of the higher orders, and dis-
cusses their relations to one another and to their surroundings.
The aim, however, is the same with that of the others ; namely,
to make clear the general principles of the science, rather than
to fill the pupil's mind with a mass of what may appear to /him
unrelated facts
THE AMERICAN SCIENCE SERIES. 5
PSYCHOLOGY— Advanced Course. By WILLIAM JAMES, Pro-
fessor in Harvard University. 2 vols. 8vo., 689, 704 pp.
From Prof. E. H. GRIFFIN, John Plopkins University: "An important
contribution to psychological science, discussing its present aspects and
problems with admirable breadth, insight, and independence."
From Prof. JOHN DEWEY, University of .Michigan; " A remarkable
union of wide learning, originality of treatment, and. above all, of
never-failing suggestions. To me the best treatment of the whole
.natter of advanced psychology in existence. It does more to put
psychology in scientific position both as to the statement of established
results and a stimulating to further problems and their treatment, than
any other book of which I know."
From Hon. W. T. HARRIS, National Bureau of Education : " I have
never seen before a work that brings together so fully all of the labors,
experimental and analytic, of the school of physiological psychologists."
BOTANY. By CHARLES E. BESSEY, Professor in the Univer-
sity of Nebraska.
Advanced Course. Svo. 611 pp.
Aims to lead the student to obtain at first-hand his knowledge
of the anatomy and physiology of plants. Accordingly, the
presentation of matter is such as to fit the book for constant
use in the labaratory, the text supplying the outline sketch which
the student is to fill in by the aid of scalpel and microscope.
From J. C. Arthur, Editor of The Botanical Gazette: " The first
botanical text-book issued in America which treats the most important
departments of the science with anything like due consideration. This
is especially true in reference to the physiology and histology of plants,
and also to special morphology. Structural Botany and classification
have up to the present time monopolized the field, greatly retarding
the diffusion of a more complete knowledge of the science."
Essentials of Botany. I2mo. 292pp.
A guide to beginners. Its principles are, that the true aim of
botanical study is not so much to seek the family and proper
names of specimens as to ascertain the laws of plant structure
and plant life; that this can be done only by examining and
dissecting the plants themselves; and that it is best to confine
the attention to a few leading types, and to take up first the
simpler and more easily understood forms, and afterwards those
whose structure and functions are more complex.
From J. T. ROTHROCK, Professor in the University of Pennsylvania:
" There is nothing superficial in it, nothing needless introduced, noth-
ing essential left out. The language is lucid ; and, as the crowning
merit of the book, the author has introduced throughout the volume
' Practical Studies,' which direct the student in his effort to see .for
himself all that the text-book f. caches."
6 THE AMERICAN SCIENCE SERIES.
CHEMISTRY. By IRA REMSEN, Professor in the Johns Hop.
kins University.
Advanced Course. 8vo. 828 pp.
The general plan of this work will be the same with that of
the Briefer Course, already published. But the part in which
the members of the different families are treated will be con-
siderably enlarged. Some attention will be given to the lines
of investigation regarding chemical affinity, dissociation, speed
of chemical action, mass action, chemical equilibrium, thermo-
chemistry, etc. The periodic law, and the numerous relations
which have been traced between the chemical and physical
properties of the elements and their positions in the periodic
system will be specially emphasized. Reference will also be
made to the subject of the chemical constitution of compounds,
and the methods used in determining constitution.
Introduction to the Study of Chemistry, I2mo. 389 pp.
The one comprehensive truth which the author aims to make
clear to the student is the essential nature of chemical action.
With this in view, he devotes the first 208 pages of the book to
a carefully selected and arranged series of simple experiments.
in which are gradually developed the main principles of the sub-
ject. His method is purely inductive ; and, wherever experience
has shown it to be practicable, the truths are drawn out by
pointed questions, rather than fully stated. Next, when the
student is in a position to appreciate it, comes a simple account
of the theory of the science. The last 150 pages of the book
are given to a survey, fully illustrated by experiments, of the
leading families of inorganic compounds.
From ARTHUR W. WRIGHT, Professor in Yale College : — The student
is not merely made acquainted with the phenomena of chemistry, but
is constantly led to reason upon them, to draw conclusions from them
and to study their significance with reference to the processes ot
chemical action — a course which makes the book in a high degree dis-
ciplinary as well as instructive.
From THOS. C. VAN NUYS, Professor of Chemistry in the Indiana
University: — It seems to me that Remsen's "Introduction to the
Study of Chemistry" meets every requirement as a text or class book.
From C. LES MEES, Professor of Chemistry in the Ohio University:
— I unhesitatingly recommend it as the best work as yet published for
the use of beginners in the study. Having used it. I feel justified in
saving this much.
THE AMERICAN SCIENCE SERIES. 7
CH E MISTR Y— Continued.
Elements of Chemistry, i2mo. 272 pp.
Utilizes the facts of every-day experience to show what chem-
istry is and how things are studied chemically. The language
is untechnical, and the subject is fully illustrated by simple ex-
periments, in which the pupil is led by questions to make his
own inferences. The author has written under the belief that
"a rational course in chemistry, whether for younger or oldei
pupils, is something more than a lot of statements of facts of
more or less importance; a lot of experiments of more or less
beauty; or a lot of rules devised for the purpose of enabling
the pupil to tell what things are made of. If the course does
not to some extent help the pupil to think as well as to see it
does not deserve to be called rational."
CHASE PALMER, Professor in the State Normal School, Salem, Mass.:
— It is the best introduction to chemistry that I know, and I intend to
put it into the hands of my pupils next Fall.
A. D. GRAY, Instructor in Springfield (Mass.) High School : — Neat,
attractive, clear, and accurate, it leaves little to be desired or sought
for by one who would find the best book for an elementary course in
our High Schools and Academies.
GENERAL BIOLOGY, By WILLIAM T. SEDGWICK, Professoi
in the Mass. Institute of Technology, and EDMUND B. WIL-
SON, Professor in Bryn Mawr College. Part I. 8vo. 193 pp.
This work is intended for college and university students as
an introduction to the theoretical and practical study of bi-
ology. It is not zoology, botany, or physiology, and is intended
not as a substitute, but as a foundation, for these more special
studies. In accordance with the present obvious tendency of
the best elementary biological teaching, it discusses broadl)
some of the leading principles of the science on the substantial
basis of a thorough examination of a limited number of typica
forms, including both plants and animals. Part First, now
published, is a general introduction to the subject illustrated
by the study of a few types. Part Second will contain a de-
tailed survey of various plants and animals.
W. G. FARLOW, Professor in Harvard University, Cambridge, Mass..
— An introduction is always difficult to write, and I know no work in
which the general relations of plants and animals and the cell-struc-
ture have been so well stated in a condensed form.
8 THE AMERICAN SCIENCE SERIES.
POLITICAL ECONOMY. By FRANCIS A. WALKER, President
of the Massachusetts Institute of Technology.
Advanced Course. 8vo. 537 pp.
The peculiar merit of this book is its reality. The reader is
brought to see the application of the laws of political economy
to real facts. He learns the extent to which those laws hold
good, and the manner in which they are applied. The subject
is divided, as usual, into the three great branches of production,
exchange, and distribution. An interesting and suggestive
" book " on consumption is added, which serves to bring in con-
veniently the principles of population. The last part of the
volume is given to the consideration of various practical appli-
cations of economic principles.
From RICHMOND MAYO SMITH, Professor in Columbia College,
N. Y.: — In my opinion it is the best text-book of political economy
that we as yet possess.
From WOODROW WILSON, Professor in Princeton University, N. J. :
— It serves better than any other book I know of as an introduction
to the most modern point of view as to economical questions.
Briefer Course. I2mo. 415 pp.
The demand fora briefer manual by the same author for the
use of schools in which only a short time can be given to the
subject has led to the publication of the present volume. The
work of abridgment has been effected mainly through excision,
although some structural changes have been made, notably in
the parts relating to distribution and consumption.
From ALEXANDER JOHNSTON, late Professor in Princeton Univer-
sity, N.J.: — Using the "Briefer Course" as a text-book, suited to
any capacity, I am able at the same time to recommend the "Ad-
vanced Course " to those who are better able to use it as a book of
reference, or more inclined to carry their work further.
Elementary Course. I2mo. 323 pp.
What has been attempted is a clear arrangement of topics;
a simple, direct, and forcible presentation of the questions
raised; the avoidance, as far as possible, of certain metaphys-
ical distinctions which the author has found perplexing; a fre-
quent repetition of cardinal doctrines, and especially a liberal
use of concrete illustrations, drawn from facts of common ex-
perience or observation.
HENRY HOLT & CO PUBLISHERS, IN. Y.
o /